U.S. patent application number 12/901390 was filed with the patent office on 2011-05-26 for hydrogel wound dressing and biomaterials formed in situ and their uses.
This patent application is currently assigned to ULURU Inc.. Invention is credited to Daniel G. Moro, John St. John.
Application Number | 20110123621 12/901390 |
Document ID | / |
Family ID | 39277479 |
Filed Date | 2011-05-26 |
United States Patent
Application |
20110123621 |
Kind Code |
A1 |
St. John; John ; et
al. |
May 26, 2011 |
HYDROGEL WOUND DRESSING AND BIOMATERIALS FORMED IN SITU AND THEIR
USES
Abstract
The present invention relates to a method of forming
shape-retentive and shape-conforming aggregate wound dressings and
biomaterials composed of gel nanoparticles and wound or bodily
fluid in which the aggregates are held together by non-covalent
bond physical forces such as, without limitation,
hydrophobic-hydrophilic interactions and hydrogen bonds. The method
comprises introducing a dry powder of gel nanoparticles to a wound
site in which the nanoparticles absorb some of the blood or wound
exudate and coalesce in situ into the claimed shape-retentive
aggregate dressing. The method also comprises introducing the dry
nanoparticle powder in or on a wet bodily tissue in vivo to form
the claimed shape-retentive biomaterial. In addition, the method
also comprises incorporating biomedical agents to produce medicated
aggregate dressings or biomaterials for a variety of medical
applications. This invention also relates to uses of the method of
formation of the shape-retentive aggregates of gel
nanoparticles.
Inventors: |
St. John; John; (Grapevine,
TX) ; Moro; Daniel G.; (Carrollton, TX) |
Assignee: |
ULURU Inc.
|
Family ID: |
39277479 |
Appl. No.: |
12/901390 |
Filed: |
October 8, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11581049 |
Oct 13, 2006 |
7910135 |
|
|
12901390 |
|
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Current U.S.
Class: |
424/486 ;
424/78.31 |
Current CPC
Class: |
A61L 26/0014 20130101;
A61L 26/0061 20130101; A61P 17/02 20180101; A61P 31/00 20180101;
A61L 2400/12 20130101; A61P 27/02 20180101; A61P 35/00 20180101;
Y10S 977/906 20130101; A61P 29/00 20180101; A61L 26/0014 20130101;
C08L 33/08 20130101 |
Class at
Publication: |
424/486 ;
424/78.31 |
International
Class: |
A61K 9/14 20060101
A61K009/14; A61K 31/765 20060101 A61K031/765; A61P 17/02 20060101
A61P017/02 |
Claims
1. A dry powder of polymeric nanoparticles prepared by a method
comprising: a) polymerizing an effective amount of a monomer or two
or more monomers, at least one of which is a 2-alkenoic acid, a
hydroxy (2C-4C) alkyl 2-alkenoate, a dihydroxy (2C-4C) alkyl
2-alkenoate, a hydroxy (2C-4C) alkoxy (2C-4C) alkyl 2-alkenoate, a
(1C-4C) alkoxy (2C-4C) alkoxy (2C-4C) alkyl 2-alkenoate or a
vicinyl epoxy (1C-4C) alkyl 2-alkenoate, in a polar liquid or a
mixture of two or more miscible liquids, at least one of which is
polar, and an effective amount of a surfactant to produce a
suspension of a plurality of polymeric nanoparticles wherein the
polymeric nanoparticles have an average diameter of less than
1.times.10.sup.-6 m; and b) removing the liquid(s) from the
suspension such that the amount of liquid(s) remaining in the dry
powder is less than 10% by weight wherein the percentage is based
on the total weight of the dry powder.
2. The dry powder of claim 1, wherein the polymeric nanoparticles
have an average diameter of from about 1 nanometer to about 1
micrometer.
3. The dry powder of claim 1, wherein the polymeric nanoparticles
have an average diameter of from about 20 to about 800
nanometers.
4. The dry powder of claim 1, wherein the polymeric nanoparticles
in the suspension exist as clusters when the concentration of
polymeric nanoparticles in the suspension is between 5 and 20%.
5. The dry powder of claim 1, wherein the polymeric nanoparticles
are about the same average diameter, are formed from one or more
monomers and are of a narrow polydispersity.
6. The dry powder of claim 1, wherein the polymeric nanoparticles
are of differing average diameter, are formed from one or more
monomers and are of a narrow polydispersity.
7. The dry powder of claim 1, wherein the polymeric nanoparticles
are formed from one or more monomers and are of a broad
polydispersity.
8. The dry powder of claim 1, wherein the step a) further
comprises: a) adding one or more first working substance(s) in an
amount effective to give a first working substance-containing
liquid, wherein after polymerization, a portion of the first
working substance-containing liquid is occluded by the polymeric
nanoparticles; and step b) further comprises: adding one or more
second working substance(s) in an effective amount to the dry
polymeric nanoparticles and dry blending to give a second working
substance-containing particulate powder, wherein the first working
substance(s) may be the same as or different than the second
working substance(s).
9. The dry powder of claim 1, wherein the step a) comprises: a)
adding from 0.01 to 10 mol percent of a surfactant to a
polymerization system comprising a monomer, or two or more
different monomers, wherein the monomer or at least one of the two
or more monomers comprise(s) one or more hydroxy and/or one or more
ester groups, in a polar liquid or mixture of polar liquids,
wherein the polar liquid or at least one of the two or more polar
liquids comprise(s) one or more hydroxy groups and polymerizing the
monomer(s) to form a plurality of polymeric nanoparticles, wherein
the addition is in the absence of a cross-linking agent.
10. The dry powder of claim 9, wherein the monomer(s) are selected
from the group consisting of a 2-alkenoic acid, a
hydroxy(2C-4C)alkyl 2-alkenoate, a dihydroxy(2C-4C) alkyl
2-alkenoate, a hydroxy(2C-4C)alkoxy(2C-4C)alkyl 2-alkenoate, a
(1C-4C)alkoxy(2C-4C)alkoxy(2C-4C)alkyl 2-alkenoate and a vicinyl
epoxy(1C-4C)alkyl 2-alkenoate and a combination of two or more
thereof.
11. The dry powder of claim 10, wherein the monomer(s) are selected
from the group consisting of acrylic acid, methacrylic acid,
2-hydroxyethyl acrylate, 2-hydroxyethylmethacrylate,
diethyleneglycol monoacrylate, diethyleneglycol monomethacrylate,
2-hydroxypropyl acrylate, 2-hydroxypropyl methyacrylate,
3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, dipropylene
glycol monoacrylate, dipropylene glycol monomethacrylate,
2,3-dihydroxypropyl methacrylate, glycidyl acrylate, glycidyl
methacrylate and a combination of two or more thereof.
12. The dry powder of claim 11, wherein the monomer(s) are selected
from the group comprising methacrylic acid, 2-hydroxyethyl
methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl
methacrylate, glycerol methacrylate and a combination of two or
more thereof.
13. The dry powder of claim 12, wherein the liquid(s) are selected
from the group consisting of water, a (1C-10C) alcohol, a
(2C-8C)polyol, a (1C-4C)alkyl ether of a (2C-8C)polyol, a
(1C-4C)acid ester of a (2C-8C)polyol, a hydroxy-terminated
polyethylene oxide, a polyalkylene glycol and a hydroxy(2C-4C)alkyl
ester of a mono, di- or tricarboxylic acid.
14. The dry powder of claim 13, wherein the liquid(s) are selected
from the group consisting of water, methanol, ethanol, isopropyl
alcohol, ethylene glycol, diethylene glycol, triethylene glycol,
polyethylene glycol 200-600, propylene glycol, dipropylene glycol,
1,4-butanediol, 2,3-butanediol, 1,6-hexanediol, 2,5-hexanediol,
ethylene glycol monomethyl ether, ethylene glycol monoethyl ether,
methylcellosolve ether, ethylene glycol monoacetate, propylene
glycol monomethyl ether, glycerine, glycerol monoacetate,
tri(2-hydroxyethyl)citrate, di(hydroxypropyl)oxalate, glyceryl
diacetate, and glyceryl monobutyrate.
15. The dry powder of claim 14, wherein the liquid is water.
16. The dry powder of claim 1, wherein the step a) further
comprises adding from about 0.1 to about 15% mol percent of a
cross-linking agent.
17. The dry powder of claim 16, wherein the cross-linking agent is
selected from the group consisting of ethylene glycol diacrylate,
ethylene glycol dimethacrylate, 1,4-dihydroxybutane dimethacrylate,
diethylene glycol dimethacrylate, propylene glycol dimethacrylate,
diethylene glycol dimethacrylate, dipropylene glycol
dimethacrylate, diethylene glycol diacrylate, dipropylene glycol
diacrylate, divinyl benzene, divinyltoluene, diallyl tartrate,
diallyl malate, divinyl tartrate, triallyl melamine, N,N'-methylene
bisacrylamide, diallyl maleate, divinyl ether, 1,3-diallyl
2-(2-hydroxyethyl) citrate, vinyl allyl citrate, allyl vinyl
maleate, diallyl itaconate, di(2-hydroxyethyl) itaconate, divinyl
sulfone, hexahydro-1,3,5-triallyltriazine, triallyl phosphite,
diallyl benzenephosphonate, triallyl aconitate, divinyl
citraconate, trimethylolpropane trimethacrylate and diallyl
fumarate.
18. The dry powder of claim 17, wherein the cross-linked polymeric
nanoparticles have an average molecular weight of from about 3,000
to about 2,000,000.
19-39. (canceled)
40. A method of forming a shape-conforming, shape-retentive
aggregate dressing or biomaterial in vivo or in situ on a wet wound
site, comprising applying the dry powder of claim 1 to the wet
wound site.
41. (canceled)
42. A method of treatment of a wound, comprising applying an
effective amount of the dry powder of claim 1.
43-51. (canceled)
Description
FIELD OF THE INVENTION
[0001] This invention relates to the fields of organic chemistry,
physical chemistry, polymer chemistry, pharmaceutical chemistry,
medicine and material science.
BACKGROUND OF THE INVENTION
[0002] The principal function of a wound dressing is to provide an
optimum healing environment. No one dressing is appropriate for all
wounds and the choice of a wound dressing is dependent on the
cause, presence of infection, wound type and size, stage of wound
healing, cost, and patient acceptability (Findlay D., Aust. Fam
Physician, 1994:23(5):824-839). According to Lawrence (Lawrence, J.
C., Injury, 1982; 13:500-512), dressing material should be sterile,
strong, absorbent, protective, inexpensive, and conform to the
contours of the body. It should be nontoxic, hypoallergenic, and
free of particulate material that may shed into the wound. Also, it
should be easy to remove without it adhering to the wound and have
an acceptable appearance to patients, nursing staff, and
others.
[0003] Wound dressings can be classified as either primary or
secondary. Primary dressings are placed directly over the wound.
They provide protection, support, and absorption, prevent
desiccation and infection, and serve as an adhesive base for the
secondary dressing. Secondary dressings provide additional support,
absorption, protection, compression, and occlusion. Often the
secondary dressing serves as a pressure dressing.
[0004] There are a wide variety of dressings available to
accomplish the essential goals of topical therapy, which are to
provide adequate oxygen and circulation to the tissues, insulate
and protect the healing wound, eliminate clinical infection by
removing excess exudate, maintain a clean and moist environment,
and obtain complete wound closure. Several different types of
products may be needed as the wound progresses through the healing
stages. These products include alginates, which form a gel covering
over the wound, cleansers, which clean the wound site, collagen, a
non-adherent covering that stimulates cellular migration,
composites and enzymatic debriders, which facilitate autolytic
debridement, exudate absorbers and foams, which fill the dead space
in a wound, medicated gauze products, to treat and control
infection, hydrocolloids and hydrogels, which reduce pain and
facilitate autolytic debridement, pouches, to collect and contain
drainage, skin sealants, and transparent films which reduce
friction and facilitate autolytic debridement (Robert G. Smith,
Wound Care Product Selection, U.S. Pharmacist, 4/2003). These
products have attributes in treating various and different stages
of wounds, however all have limitations. For example, alginates can
possibly dehydrate the wound bed, give off foul odors and are
contraindicated for use in the presence of dry eschar, on third
degree burns and surgical implantation. Collagen dressings are also
contraindicated for use in third degree burns and necrotic wounds.
Gauze bandages, which are rendered non-adherent by incorporating
petrolatum, still have a tendency to tear away new skin in removal
and shed lint into the wound. In addition, they are non-absorbent.
Hydrocolloids dressing are difficult to remove and malodorous
yellow-brown drainage fluid typically collects under these
dressings. Foams are not recommended for wounds with no exudates or
wounds with dry eschar. Current hydrogel dressings have many
advantages as compared to other products, but since they contain a
large amount of water (80-90%), they are non-absorbent and not
recommended for use on heavily exuding wounds, and if used alone,
do not keep bacteria out of the wound.
[0005] This overview has been presented regarding wounds and
different treatment modalities, and it is also important that a
detailed description of polymer hydrogels be given since this
invention pertains to hydrogel wound dressings and
biomaterials.
[0006] A gel is a three-dimensional polymeric network that has
absorbed a liquid to form a stable, usually soft and pliable,
composition having a non-zero shear modulus. When the liquid
absorbed by a gel is water, the gel is called a hydrogel. Water may
comprise a significant weight percent of a hydrogel. This, plus the
fact that many hydrogel-forming polymers are biologically inert,
makes hydrogels particularly useful in a wide variety of biomedical
applications.
[0007] For example, hydrogels are widely used in soft contact lens.
They are also used as burn and wound dressings, with and without
incorporated drugs that can be released from the gel matrix to aid
in the healing process (e.g., see U.S. Pat. Nos. 3,063,685 and
4,272,518). Hydrogels have been used as coatings to improve the
wettability of the surfaces of medical devices such as blood
filters (U.S. Pat. No. 5,582,794). They have also found utility as
devices for the sustained release of biologically active
substances. For example, U.S. Pat. No. 5,292,515 discloses a method
of preparing a hydrophilic reservoir drug delivery device. The '515
patent discloses that drug release rates can be controlled by
changing the water content of the hydrogel subcutaneous implant,
which directly affects its permeability coefficient.
[0008] In all the above applications, the gel or hydrogel is in
bulk form, that is, it is an amorphous mass of material with no
discernable regular internal structure. Bulk hydrogels have slow
swelling rates due to the large internal volume relative to the
surface area through which water must be absorbed. Furthermore, a
substance dissolved or suspended in the absorbed water will diffuse
out of the gel at a rate that depends on the distance it must
travel to reach the surface of the gel. That is, molecules near the
surface of the hydrogel will escape quickly, whereas molecules
deeper within the matrix will take a much longer time to reach the
outer surface of the gel. This situation can be ameliorated to some
extent by using particulate gels. If each particle is sufficiently
small, substances dispersed in the particles will diffuse to the
surface and be released at approximately the same time.
[0009] Particulate gels can be formed by a number of procedures
such as direct or inverse emulsion polymerization (Landfester, et
al., Macromolecules, 2000, 33:2370) or they can be created from
bulk gels by drying the gel and then grinding the resulting xerogel
to particles of a desired size. The particles can then be
re-solvated to form particulate gels. Particles having sizes in the
micro (10.sup.-6 meters (m)) to nano (10.sup.-9 m) diameter range
can be produced by this means. Molecules of a substance occluded by
particles in these size ranges will all have about the same
distance to travel to reach the outer surface of the particle and
will exhibit near zero-order release kinetics. However, particulate
gels have their problems. For instance, it is difficult to control
the dissemination of the particles to, and localization at, a
selected target site. Furthermore, while bulk hydrogels can be
rendered shape-retentive, making them useful as biomaterials in a
variety of medical applications, currently available particulate
gels, cannot.
[0010] Co-pending U.S. Patent Application Publication No. US
200410086548A1 discloses a shape-retentive aggregate formed from
hydrogel particles, thus combining the shape-retentiveness of bulk
hydrogels with the substance release control of particulate gels.
The '548 application discloses a method of forming the
shape-retentive aggregates comprising preparing a suspension of
hydrogel particles in water or other polar liquid and concentrating
the suspension until the particles coalesce into a shape-retentive
aggregate held together by non-covalent bond physical forces
including but not limited to hydrophobic/hydrophilic interactions
and hydrogen bonds. The devices of this invention are particularly
useful, for example, as drug delivery implants, tissue scaffolds
for cartilage or bone repair, and moldable drug eluting contact
lenses and catheters.
[0011] Co-pending U.S. Patent Application Publication No. US
2005/0118270A1 discloses a method of forming shape-retentive
aggregates in situ, such that the shape of the aggregate would be
dictated by the shape of the locus of application. Aggregate
formation is accomplished by introducing a suspension of gel
particles dispersed in a polar liquid, preferably water, wherein
the gel particles have an absolute zeta potential enabling the
particles to remain dispersed, into a receiving medium wherein the
absolute zeta potential of the gel particles is reduced. The gel
particles coalesce into a shape-retentive aggregate held together
by non-covalent bond physical forces comprising
hydrophobic-hydrophilic interactions and hydrogen bonding.
Applications include, but not limited to biomedical uses such as
joint reconstruction, wound repair, drug deliver implants formed in
situ and cosmetic and reconstructive surgery.
DISCLOSURE OF THE INVENTION
[0012] Applicants disclose an integral, shape-conforming and
shape-retentive aggregate that forms a dressing directly on a wound
in situ and for other applications, forms a biomaterial in vivo in
or on a wet bodily tissue. In the former application, the hydrogel
nanoparticulate powder utilizes the blood or exudate from a wound,
which is substantially composed of water and other biological
compounds, such as serum, fibrin and white blood cells, absorbs
this polar liquid and coalesces into a closely packed network of
nanoparticles and wound fluid, held together by non-covalent bond
physical forces comprising hydrophobic-hydrophilic interactions and
hydrogen bonding. The aggregate dressings realize their
characteristic wound conforming and shape-retentive properties by
virtue of strong inter-particle attractive forces such as, without
limitation, hydrogen bonds, and by virtue of hydrogen bonding
between the particles and the liquid in the voids between the
particles. The dressings remain intact as integral films during the
healing stages of the wound, and fall off when the wound is no
longer wet or healing has occurred. In the latter application, the
powder utilizes any bodily fluid in vivo to form a shape-retentive
aggregate biomaterial held together by the same forces previously
described. The discussion to follow will primarily focus on wound
dressings formed in situ, realizing however that the same
properties can be provided for biomaterials formed in vivo for a
wide array of medical applications.
[0013] One important feature of these dressings and biomaterials is
that a variety of biological and/or pharmaceutical agents can be
easily incorporated by mixing the nanoparticulate powder with an
active or combination thereof and applying the mixed material to
the wound site directly or placed in or on a wet bodily tissue in
vivo. The resulting bandage will then provide a sustained delivery
of the therapeutic compound(s) for a prolonged period of time to
the underlying wound bed to aid in the treatment, management and
eventual healing of the wound and/or to alleviate pain. The ability
to form in situ protective, non-occlusive, biocompatible,
shape-conforming, shape-retentive dressings with or without
therapeutically active compounds for a variety of exuding wounds,
such as burns, dermabrasions, skin donor sites, punch biopsies,
decubitus and vascular ulcers and the like represents a major
advancement in the treatment and management of wounds. These
dressings have all of the ideal attributes that wound dressings
should exhibit, namely provide adequate oxygen to the underlying
tissue, since these non-occlusive dressing are porous as they are
composed of nanoparticles and wound exudate, protect the wound from
exogenous bacteria, eliminate the potential for infection by
utilizing the exudate of the wound in the formation of the
dressing, maintain a clean and moist environment as they are
hydrogels and obtain complete wound closure.
[0014] Thus, the present invention provides a dry powder of
polymeric nanoparticles prepared by a method by polymerizing an
effective amount of a monomer or two or more monomers, at least one
of which is a 2-alkenoic acid, a hydroxy (2C-4C) alkyl 2-alkenoate,
a dihydroxy (2C-4C) alkyl 2-alkenoate, a hydroxy (2C-4C) alkoxy
(2C-4C) alkyl 2-alkenoate, a (1C-4C) alkoxy (2C-4C) alkoxy (2C-4C)
alkyl 2-alkenoate or a vicinyl epoxy (1C-4C) alkyl 2-alkenoate, in
a polar liquid or a mixture of two or more miscible liquids, at
least one of which is polar, and an effective amount of a
surfactant to produce a suspension of a plurality of polymeric
nanoparticles wherein the polymeric nanoparticles have an average
diameter of less than 1.times.10.sup.-6 m; and then removing the
liquid(s) from the suspension such that the amount of liquid(s)
remaining in the dry powder is less than 10% by weight wherein the
percentage is based on the total weight of the dry powder.
[0015] In another aspect, the present invention provides a method
of forming a shape-conforming, shape-retentive aggregate dressing
in situ on a wet wound site by applying the dry powder to the wet
wound site.
[0016] In a further aspect, the present invention provides a method
of forming a shape-conforming, shape-retentive aggregate
biomaterial in vivo in or on a wet bodily tissue, by applying the
dry powder on the wet bodily tissue.
[0017] In another aspect, the present invention provides a method
of treatment of a wound, comprising applying an effective amount of
the dry powder.
BRIEF DESCRIPTION OF THE FIGURES AND TABLES
[0018] FIG. 1 is photograph showing the hydrogel nanoparticle
powder, the powder applied to phosphate buffered saline and the
resulting aggregate film after the powder hydrates.
[0019] FIG. 2 is a plot showing the relative mass of an aggregate
formed from 500 mg of nanoparticle powder applied to phosphate
buffered saline and changes in the mass of those aggregates over
time at constant temperature and humidity. The aggregates had
different chemical compositions.
[0020] FIG. 3 is a plot showing the release of lidocaine from
nanoparticle aggregate burn dressings composed of pHEMA and
copolymers of HEMA and GMA.
[0021] FIG. 4 is a plot showing the release of erythromycin from
nanoparticle aggregate burn dressings composed of pHEMA and
copolymers of HEMA and GMA.
[0022] FIG. 5 is a plot showing the release of 1,10-phenanthroline
from nanoparticle powders composed of mixtures of pHEMA and pHPMA
particles with different diameters.
[0023] FIG. 6 shows the inhibition of staph aureus bacteria on a
petri-dish from a nanoparticle aggregate loaded with doxycycline
and rifampin.
[0024] FIG. 7 shows the inhibition of staph aureus bacteria on a
Petri-dish from a control nanoparticle aggregate without any
antibiotic.
[0025] FIG. 8 shows plots of the inhibition of the bacteria strains
Pseudomonas aeruginosa, Staphylococcus aureus, and Enterococcus
faecalis over time with nanoparticle aggregates containing
doxycycline and rifampin compared to a commercial silver antibiotic
impregnated bandage.
[0026] FIG. 9 shows nanoparticle powder being applied to a full
thickness wound in a porcine model.
[0027] FIG. 10 shows the nanoparticle powder and a commercial
hydrogel dressing applied to skin graft donor sites in a porcine
model with healing over time.
[0028] FIG. 11 shows the histology for wounds treated with
nanoparticle aggregate containing platelet derived growth factor
and a control aggregate containing no growth factor.
[0029] FIG. 12 shows the histology for wounds treated with
nanoparticle aggregate containing vascular endothelial growth
factor and a control aggregate containing no growth factor.
[0030] FIG. 13 shows the histology for wounds treated with
nanoparticle aggregate containing a combination of platelet derived
growth factor and vascular endothelial growth factor and a control
aggregate containing no growth factor.
[0031] Table 1 shows the ratios of HEMA and HPMA monomers in mass
and mmol used to form hydrogel nanoparticles that consist of
copolymers.
[0032] Table 2 shows the ratios of HEMA and GMA monomers used to
form hydrogel nanoparticles that consist of copolymers.
[0033] Table 3 shows the relative elongation and tension at failure
for aggregates formed of nanoparticles with different chemical
compositions.
[0034] Table 4 shows the sizes of nanoparticles used to form
aggregates of mixtures of nanoparticle with different chemical
composition for the controlled release of 1,1-phenanthroline.
MODES FOR CARRYING OUT THE INVENTION
Definitions
[0035] As used herein, the term "comprising" is intended to mean
that the compositions and methods include the recited elements, but
not excluding others. "Consisting essentially of" when used to
define compositions and methods, shall mean excluding other
elements of any essential significance to the combination. Thus, a
composition consisting essentially of the elements as defined
herein would not exclude trace contaminants from the isolation and
purification method and pharmaceutically acceptable carriers, such
as phosphate buffered saline, preservatives, and the like.
"Consisting of" shall mean excluding more than trace elements of
other ingredients and substantial method steps for administering
the compositions of this invention. Embodiments defined by each of
these transition terms are within the scope of this invention.
[0036] All numerical designations, e.g., pH, temperature, time,
concentration, and molecular weight, including ranges, are
approximations which are varied (+) or (-) by increments of 0.1. It
is to be understood, although not always explicitly stated that all
numerical designations are preceded by the term "about". It also is
to be understood, although not always explicitly stated, that the
reagents described herein are merely exemplary and that equivalents
of such are known in the art.
[0037] As used herein, the term "gel" refers to a three-dimensional
polymeric structure that itself is insoluble in a particular liquid
but which is capable of absorbing and retaining large quantities of
the liquid to form a stable, often soft and pliable, but always to
one degree or another shape-retentive, structure. When the liquid
is water, the gel is referred to as a hydrogel. Unless expressly
stated otherwise, the term "gel" will be used throughout this
application to refer both to polymeric structures that have
absorbed a liquid other than water and to polymeric structures that
have absorbed water, it being readily apparent to those skilled in
the art from the context whether the polymeric structure is simply
a "gel" or a "hydrogel."
[0038] The term "polar liquid," as used herein has the meaning
generally understood by those skilled in the chemical art. In
brief, a polar liquid is one in which the electrons are unevenly
distributed among the atoms of its molecules and therefore create
an electrical dipole. To be polar, a molecule must contain at least
one atom that is more electronegative than other atoms in the
molecule. Examples of polar liquids include, without limitation,
water, where the oxygen atom bears a partial negative charge and
the hydrogen atoms a partial positive charge, and alcohols, wherein
the O--H moiety is similarly polarized.
[0039] As used herein, "gel particle" refers to a microscopic or
sub-microscopic quantity of a gel in a discrete shape, usually, but
not necessarily, spherical or substantially so. As used herein, a
"gel particle" includes small clusters of individual particles held
together by non-covalent bond physical forces such as
hydrophilic/hydrophobic interactions and hydrogen bonding, wherein
the clusters do not adversely affect the stability of a gel
particle suspension (suspension system) containing them or the
performance of the nanoparticle powder in the methods of this
invention. Clusters result from changes in concentration of gel
particles in suspension and during the drying stage to isolate the
nanoparticles. That is, at higher concentrations, it is more likely
individual particles will get close enough to one another for
non-covalent bond forces to cause them to coalesce.
[0040] As used herein, a "suspension" refers to a uniformly
distributed, stable dispersion of a solid in a liquid in which the
solid is not soluble. A surfactant may be added to the liquid to
help stabilize the dispersion. As used herein, a "suspension
system" refers to a suspension wherein gel particles of this
invention are the dispersed solid. By "stable" is meant that the
solid remains uniformly dispersed for at least 24 hours, unless
subjected to disrupting external forces such as, without
limitation, centrifugation or filtration.
[0041] As used herein, a "surfactant" has the meaning generally
understood by those skilled in the chemical art. That is, a
surfactant is a soluble compound, which may be anionic, cationic,
zwitterionic, amphoteric or neutral in charge, and which reduces
the surface tension of the liquid in which it is dissolved or that
reduces interfacial tension between two liquids or a liquid and a
solid.
[0042] As used herein, the term "shape-conforming and
shape-retentive aggregate" refers to a structure formed in situ on
a wet wound or biomaterial formed in vivo on or in a wet bodily
tissue composed of a large number of gel particles held together by
inter-particle and particle-liquid forces such as, without
limitation, hydrophilic/hydrophobic interactions and hydrogen
bonding wherein the structure maintains indefinitely as longs as it
remains hydrated.
[0043] As used herein, the term "monomer" has the meaning
understood by those skilled in the chemical art. That is, a monomer
is a small chemical compound that is capable of forming a
macromolecule of repeating units of itself, i.e., a polymer. Two or
more different monomers may react to form a polymer in which each
of the monomers are repeated numerous times, the polymer being
referred to as a copolymer to reflect the fact that it is made up
of more than one monomer.
[0044] As used herein, the term "size" when used to describe a gel
particle of this invention refers to the volume of an essentially
spherical particle as represented by its diameter, which of course
is directly related to its volume. When referring to a plurality of
gel particles, size relates to the average volume of the particles
in the plurality as represented by their average diameter.
[0045] As used herein, the term "polydispersity" refers to the
range of sizes of the particles in a suspension system. "Narrow
polydispersity" refers to a suspension system in which the size of
the individual particles, as represented by their diameters,
deviates 10% or less from the average diameter of the particles in
the system. If two or more pluralities of particles in a suspension
system are both stated to be of narrow polydispersity, what is
meant is that there are two distinct sets of particles wherein the
particles of each set vary in diameter by no more than 10% from an
average diameter of the particles in that set and the two averages
are distinctly different. A non-limiting example of such a
suspension system would be one comprising a first set of particles
in which each particle has a diameter of 20 nm.+-.10% and a second
set of particles in which each particle has a diameter of 40
nm.+-.10%.
[0046] As used herein, the term "broad polydispersity" refers to a
suspension system in which the size of the individual particles of
a set of particles deviates more than 10% from the average size of
the particles of the set.
[0047] As used herein, the term "plurality" simply refers to more
than one, i.e., two or more.
[0048] As used herein, "chemical composition" as it relates to a
gel particle of this invention refers to the chemical composition
of the monomers that are polymerized to provide the polymer strands
of the particle, to the chemical composition and ratios of
different monomers if two or more monomers are used to prepare the
polymer strands of the particles and/or to the chemical composition
and quantity of any cross-linking agent(s) that are used to
inter-connect the particle strands.
[0049] As used in, a "particle strand" refers to a single polymer
molecule or, if the system in which the strand exists contains a
cross-linking agent, two or more inter-connected polymer molecules.
The average number of polymer strands that will be cross-linked and
the average number of cross-links between any two polymer strands
in a particular gel particle will depend on the quantity of
cross-linker in the system and on the concentration of polymer
strands.
[0050] As used herein, a "working substance" refers to any
substance that is occluded by a gel particle or entrapped in a
shape-retentive aggregate dressing or biomaterial of this
invention. Examples of working substances, without limitation,
include biomedical agents; biologically active substances such as
pharmaceutical agents, genes, proteins, peptides, poly-saccharides,
growth factors, monoclonal antibodies, fragmented antibodies,
antigens, polypeptides, DNA, RNA and ribozymes.
[0051] As used herein, the phrase "pharmaceutical agent" refers to
both small molecule and to macromolecular compounds used as drugs.
Among the former are, without limitation, antibiotics,
chemotherapeutics (in particular platinum compounds and taxol and
its derivatives), analgesics, antidepressants, anti-allergenics,
anti-arryhthics, anti-inflammatory compounds, CNS stimulants,
sedatives, anti-cholinergics, anti-arteriosclerotics, and the like.
Macromolecular compounds include, without limitation, monoclonal
antibodies (mAbs), Fabs, proteins, peptides, cells, antigens,
nucleic acids, enzymes, growth factors and the like. A
pharmaceutical agent may be intended for topical or systemic
use.
[0052] As used herein "hydroxy" refers to an --OH group.
[0053] As used herein, the term "alkyl" refers to a straight or
branched chain saturated aliphatic hydrocarbon, i.e., a compound
consisting of carbon and hydrogen only. The size of an alkyl in
terms of how many carbon atoms it contains is indicated by the
formula ("a"C-"b"C)alkyl where a and b are integers. For example, a
(1C-4C)alkyl refers to a straight or branched chain alkyl
consisting of 1, 2, 3 or 4 carbon atoms. An alkyl group may be
substituted or unsubstituted.
[0054] As used herein, the term "alkoxy" refers to the group
--O-alkyl wherein alkyl is as defined herein. The size of an alkoxy
in terms of how many carbon atoms it contains is indicated by the
formula ("a"C-"b"C) alkoxy where a and b are integers. For example,
a (1C-4C) alkoxy refers to a straight or branched chain --O-alkyl
consisting of 1, 2, 3 or 4 carbon atoms. An alkoxy group may be
substituted or unsubstituted.
[0055] As used herein, "ester" refers to the group --C(O)O-alkyl
wherein alkyl is as defined herein.
[0056] As used herein, "ether" refers to the group alkyl-O-alkyl
wherein alkyl is as defined herein.
[0057] As used herein, "2-alkenoic acid" refers to the group
(R.sup.1) (R.sup.2)C.dbd.C(R.sup.3)--C(O)OH wherein each of
R.sup.1, R.sup.2, R.sup.3 are independently selected from hydrogen
and alkyl wherein alkyl is as defined herein. These 2-alkenoic
acids are exemplified, for example by, acrylic acid, methacrylic
acid, etc.
[0058] As used herein, "2-alkenoate" refers to the group
(R.sup.1)(R.sup.2)C.dbd.C(R.sup.3)--C(O)O-alkyl wherein each of
R.sup.1, R.sup.2, R.sup.3 are independently selected from hydrogen
and alkyl wherein alkyl is as defined herein.
[0059] As used herein, the phrases "voids between the hydrogel
nanoparticles" or "between the nanoparticles" refer to the open
space generated when essentially spherical gel particles touch at
their circumferences when forming shape-retentive aggregate
dressings of this invention. The volume of the voids can be
approximated as 0.414 times the average radius of the spheres if
the spheres have narrow polydispersity and pack in a close-packed
arrangement.
[0060] As used herein, a "cross-linking agent" refers to a di-,
tri-, or tetra-functional chemical entity that is capable of
forming covalent bonds with functional groups on polymeric strands
resulting in a three-dimensional structure.
[0061] A "hydrogen bond" refers to the electrostatic attraction
between a hydrogen atom covalently bonded to a highly
electronegative atom and another electronegative atom having at
least one lone pair of electrons. The strength of a hydrogen bond,
about 23 kJ (kilojoules) mol.sup.-1, is between that of a covalent
bond, about 500 kJ mol.sup.-1, and a van der Waals attraction,
about 1.3 kJ mol.sup.-1. Hydrogen bonds have a marked effect on the
physical characteristics of a composition capable of forming them.
For example, ethanol has a hydrogen atom covalently bonded to an
oxygen atom, which also has a pair of unshared (i.e., a "lone
pair") electrons and, therefore, ethanol is capable of hydrogen
bonding with itself. Ethanol has a boiling point of 78.degree. C.
In general, compounds of similar molecular weight are expected to
have similar boiling points. However, dimethyl ether, which has
exactly the same molecular weight as ethanol but which is not
capable of hydrogen bonding between molecules of itself, has a
boiling point of -24.degree. C., almost 100 degrees lower than
ethanol. Hydrogen bonding between the ethanol molecules has made
ethanol act as if it were substantially higher in molecular
weight.
[0062] As used herein, an "excipient" refers to an inert substance
added to a pharmaceutical composition to facilitate its
administration. Examples, without limitation, of excipients include
calcium carbonate, calcium phosphate, various sugars and types of
starch, water-soluble polymers, cellulose derivatives, gelatin,
vegetable oils and polyethylene glycols. A "pharmaceutically
acceptable excipient" refers to an excipient that does not cause
significant irritation to an organism and does not abrogate the
biological activity and properties of the administered
compound.
[0063] As used herein, the phrase "useful in the treatment of"
means that the pharmaceutical agent is known to either directly or
indirectly inhibit, preferably destroy or deactivate, the causal
agent of the disease indicated or to at least ameliorate,
preferably eliminate, the symptoms of that disease. With regard to
wound healing, the agent is known to at least decrease the time to
wound closure.
[0064] As used herein, the term "cancer" refers to malignant
neoplasms, which, in turn relate to a large group of diseases that
can arise in virtually any tissue composed of potentially dividing
cells. The basic characteristic of cancer is a transmissible
abnormality of cells that is manifested by reduced control over
growth and function leading to serious life-threatening effects on
the host through invasive growth and metastases.
[0065] As used herein, "ocular disease" refers to a disease in
which the eyes do not function properly so that vision is affected.
Examples of ocular diseases include, without limitation, glaucoma,
macular degeneration, diabetic retinopathy, and cataracts. Examples
of pharmaceutical agents useful in the treatment of ocular diseases
include, without limitation, anti-inflammatory agents, antibiotics,
antimicrobials and pressure reducing agents.
[0066] As used herein, an "infection" refers to a disease state
caused by a microorganism such as, without limitation, a bacterium,
a virus, a prion, a fungus, an amoeba or a protozoon. Examples of
pharmaceutical agents useful in the treatment of infections
include, without limitation antimicrobials, antibiotics and
bacteriostatic agents.
[0067] The shape-retentive aggregate dressings or biomaterials of
this invention may be manipulated using the disclosures herein so
as to be capable of occluding and/or entrapping virtually any
pharmaceutical agent presently known, or that may become known, to
those skilled in the art as being effective in the treatment and/or
prevention of any of the above diseases and all such pharmaceutical
agents are within the scope of this invention.
[0068] As used herein, the term "about" means.+-.15% of the value
modified with the term.
[0069] As used herein, the term "in situ" refers to the process or
procedure of forming a wound dressing directly in place on or in a
mammal, in particular a human being.
[0070] As used herein, the term "biomaterial" refers to the
shape-retentive and shape-conforming material formed when hydrogel
nanoparticle powder is introduced in vivo to a wet wound tissue in
a mammal, in particular a human being.
[0071] As used herein, the term "hydrophilic/hydrophobic
interactions" refers to the inter- or intra-molecular association
of chemical entities through physical forces, whereby hydrophilic
compounds or hydrophilic regions of compounds tend to associate
with other hydrophilic compounds or hydrophilic regions of
compounds, and hydrophobic compounds or hydrophobic regions of
compounds tend to associate with other hydrophobic compounds or
hydrophobic regions of compounds.
[0072] As used herein, the term "occlude" has the meaning generally
understood by those skilled in the chemical art, that is, to absorb
and retain a substance for a period of time. With regard to this
invention, substances may be absorbed by and retained in, i.e.
occluded by, gel particles of this invention during their
formation.
[0073] As used herein, the term "entrapped" refers to the retention
for a period of time of a substance in the voids between the gel
particles comprising shape-retentive aggregate dressings or
biomaterials of this invention.
[0074] As used herein, the term "average molecular weight" refers
to the weight of individual polymer strands or cross-linked polymer
strands of this invention. For the purpose of this invention,
average molecular weight is determined by gel permeation
chromatography with laser light scattering detection.
[0075] As used herein, "growth factors" refer to certain
polypeptides that, when bound by growth factor receptors on the
surface of cells, stimulate the cells to grow in size and to
divide. Growth factor receptors are specific to each growth factor
so that only cells that express the exact receptor for a particular
growth factor will be stimulated by that growth factor. Examples of
growth factors include, without limitation, vascular endothelial
growth factor (VEGF), insulin-like growth factor (IGF), fibroblast
growth factor (FGF), epidermal growth factor (EGF), hepatocyte
growth factor (HGF) and platelet-derived growth factor (PDGF).
[0076] As used herein, "tissue scaffold" refers to a highly porous,
artificial, three-dimensional extra-cellular matrix that is used in
vivo as a framework to which cells can attach and grow to
regenerate tissues lost through injury or disease.
[0077] As used herein, "wet wound" refers to any wound in which
fluid is exiting the wound site, which may be blood or exudate.
[0078] As used herein, "bodily fluid" refers to any liquid present
in the bodily tissues of mammals, preferably man.
[0079] As used herein, "exudate" refers to the fluid present in a
wound site substantially composed of water and other biological
materials, such as white blood cells, fibrin, and serum.
[0080] As used herein, "working substance/particulate powder
composite" refers to a mixture of the nanoparticle dry powder and
any working substance and/or pharmaceutical excipient.
EMBODIMENTS
[0081] This invention provides a dry powder of polymeric
nanoparticles; methods of forming a shape-conforming,
shape-retentive aggregate dressing in situ on a wet wound site;
methods of forming a shape-conforming, shape-retentive aggregate
biomaterial in vivo in or on a wet bodily tissue and uses of the
dry powder in the treatment of wounds. These and further
embodiments are discussed below in details.
[0082] In an embodiment, this invention provides a dry powder of
polymeric nanoparticles prepared by polymerizing an effective
amount of a monomer or two or more monomers, at least one of which
is a 2-alkenoic acid, a hydroxy (2C-4C) alkyl 2-alkenoate, a
dihydroxy (2C-4C) alkyl 2-alkenoate, a hydroxy (2C-4C) alkoxy
(2C-4C) alkyl 2-alkenoate, a (1C-4C) alkoxy (2C-4C) alkoxy (2C-4C)
alkyl 2-alkenoate or a vicinyl epoxy (1C-4C) alkyl 2-alkenoate, in
a polar liquid or a mixture of two or more miscible liquids, at
least one of which is polar, and an effective amount of a
surfactant to produce a suspension of a plurality of polymeric
nanoparticles wherein the polymeric nanoparticles have an average
diameter of less than 1.times.10.sup.-6 m. After polymerization,
the liquid(s) are from the suspension such that the amount of
liquid(s) remaining in the dry powder is less than 10% by weight
wherein the percentage is based on the total weight of the dry
powder.
[0083] In some embodiments, the gel particles of the methods
described above have an average diameter of from about 1 nanometer
to about 1 micrometer, while in others the gel particles have an
average diameter of from about 20 to about 800 nanometers. In
alternative embodiments, the average diameter of the gel particles
is from about 100 to about 700 nanometers, or alternatively from
about 40 to about 300 nanometers, or alternatively from about 100
to about 800 nanometers, or alternatively from about 300 to about
800 nanometers, or alternatively from about 600 to about 800
nanometers, or alternatively from about 50 to about 700 nanometers.
In a yet further embodiments, the average diameter of the gel
particles is greater than about 35 nanometers, or yet further 55
nanometer, or yet further greater than about 75 nanometers, or yet
further greater than about 100 nanometers, or yet further greater
than about 150 nanometers, or yet further greater than about 200
nanometers, or yet further greater than about 250 nanometers, 300
nanometers, or yet further greater than about 350 nanometers, or
yet further greater than about 400 nanometers.
[0084] In some embodiments, the gel particles of the methods
described above, are about the same average diameter, are formed
from one or more monomers and are of a narrow polydispersity. In
some embodiments, the plurality of gel particles of the methods
described above is at a concentration in the range of 5-20% that
results in cluster formation. Alternative concentrations within the
scope of this invention include the range of about 5-10%, or
alternatively about 5-15%, or alternatively about 10-20%, or
alternatively about 15-20%, or alternatively about 10-15%, or
alternatively about 6-19%, or alternatively about 7-18%, each of
which results in cluster formation. In some embodiments, the
pluralities of gel particles of the methods described above, are of
differing average diameter, are formed from one or more monomers
and are of a narrow polydispersity while in others they are of a
broad polydispersity.
[0085] In another embodiment, the dry powder is obtained by adding
one or more first working substance(s) in an amount effective to
give a first working substance-containing liquid, wherein after
polymerization, a portion of the first working substance-containing
liquid is occluded by the polymeric nanoparticles and then adding
one or more second working substance(s) in an effective amount to
the dry polymeric nanoparticles and dry blending to give a second
working substance-containing particulate powder, wherein the first
working substance(s) may be the same as or different than the
second working substance(s).
[0086] In another embodiment, the dry powder is obtained by adding
from 0.01 to 10 mol percent of a surfactant to a polymerization
system comprising a monomer, or two or more different monomers,
wherein the monomer or at least one of the two or more monomers
comprise(s) one or more hydroxy and/or one or more ester groups, in
a polar liquid or mixture of polar liquids, wherein the polar
liquid or at least one of the two or more polar liquids comprise(s)
one or more hydroxy groups and polymerizing the monomer(s) to form
a plurality of polymeric nanoparticles, each particle comprising a
plurality of polymer strands, wherein the addition is in the
absence of a cross-linking agent and the resulting non-cross-linked
polymer or copolymer is water insoluble but water swellable, and
drying the nanoparticles to obtain the dry powder. In alternative
embodiments, the effective amount of the surfactant is from about
0.01 weight percent to about 0.1 weight percent, or alternatively
from about 0.01 weight percent to about 0.2 weight percent, or
alternatively from about 0.01 weight percent to about 0.3 weight
percent, or alternatively from about 0.01 weight percent to about
0.4 weight percent, or alternatively from about 0.1 weight percent
to about 1.0 weight percent, or alternatively from about 0.1 weight
percent to about 3.0 weight percent, or alternatively from about
0.1 weight percent to about 5.0 weight percent, or alternatively
from about 0.1 weight percent to about 7.0 weight percent, or
alternatively from about 0.1 weight percent to about 9.0 weight
percent, or alternatively from about 0.02 weight percent to about
9.5 weight percent.
[0087] In another embodiment, the monomer(s) for the process
described above, are selected from the group consisting of a
2-alkenoic acid, a hydroxy(2C-4C)alkyl 2-alkenoate, a
dihydroxy(2C-4C) alkyl 2-alkenoate, a
hydroxy(2C-4C)alkoxy(2C-4C)alkyl 2-alkenoate, a
(1C-4C)alkoxy(2C-4C)alkoxy(2C-4C)alkyl 2-alkenoate and a vicinyl
epoxy(1C-4C)alkyl 2-alkenoate and a combination of two or more
thereof. In a further embodiment, the monomer(s) are selected from
the group consisting of acrylic acid, methacrylic acid,
2-hydroxyethyl acrylate, 2-hydroxyethylmethacrylate,
diethyleneglycol monoacrylate, diethyleneglycol monomethacrylate,
2-hydroxypropyl acrylate, 2-hydroxypropyl methyacrylate,
3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, dipropylene
glycol monoacrylate, dipropylene glycol monomethacrylate,
2,3-dihydroxypropyl methacrylate, glycidyl acrylate, glycidyl
methacrylate and a combination of two or more thereof. In another
embodiment, the monomer(s) are selected from the group comprising
methacrylic acid, 2-hydroxyethyl methacrylate, 2-hydroxypropyl
methacrylate, 3-hydroxypropyl methacrylate, glycerol methacrylate
and a combination of two or more thereof.
[0088] In another embodiment, the liquid(s) for the process
described above, are selected from the group consisting of water, a
(1C-10C) alcohol, a (2C-8C)polyol, a (1C-4C)alkyl ether of a
(2C-8C)polyol, a (1C-4C)acid ester of a (2C-8C)polyol, a
hydroxy-terminated polyethylene oxide, a polyalkylene glycol and a
hydroxy(2C-4C)alkyl ester of a mono, di- or tricarboxylic acid. In
a further embodiment, the liquid(s) are selected from the group
consisting of water, methanol, ethanol, isopropyl alcohol, ethylene
glycol, diethylene glycol, triethylene glycol, polyethylene glycol
200-600, propylene glycol, dipropylene glycol, 1,4-butanediol,
2,3-butanediol, 1,6-hexanediol, 2,5-hexanediol, ethylene glycol
monomethyl ether, ethylene glycol monoethyl ether, methylcellosolve
ether, ethylene glycol monoacetate, propylene glycol monomethyl
ether, glycerine, glycerol monoacetate, tri(2-hydroxyethyl)citrate,
di(hydroxypropyl)oxalate, glyceryl diacetate, and glyceryl
monobutyrate. In a particular embodiment, the liquid is water.
[0089] In another embodiment, the dry powder is obtained by a
process comprising adding from 0.01 to 10 mol percent of a
surfactant to a polymerization system comprising a monomer, or two
or more different monomers, wherein the monomer or at least one of
the two or more monomers comprise(s) one or more hydroxy and/or one
or more ester groups, in a polar liquid or mixture of polar
liquids, wherein the polar liquid or at least one of the two or
more polar liquids comprise(s) one or more hydroxy groups; adding
from 0.01 to 10 mol percent of a surfactant to the polymerization
system; polymerizing the monomer(s) to form a plurality of gel
nanoparticles, each particle comprising a plurality of polymer
strands, such that the resulting non-cross-linked polymer or
copolymer is water insoluble but water swellable and drying the
nanoparticles to obtain the dry powder, wherein the process further
comprises adding from about 0.1 to about 15% mol percent of a
cross-linking agent to the polymerization system which results in
cross-linking of the polymer strands. The cross-linking agent is
selected from the group consisting of ethylene glycol diacrylate,
ethylene glycol dimethacrylate, 1,4-dihydroxybutane dimethacrylate,
diethylene glycol dimethacrylate, propylene glycol dimethacrylate,
diethylene glycol dimethacrylate, dipropylene glycol
dimethacrylate, diethylene glycol diacrylate, dipropylene glycol
diacrylate, divinyl benzene, divinyltoluene, diallyl tartrate,
diallyl malate, divinyl tartrate, triallyl melamine, N,N'-methylene
bisacrylamide, diallyl maleate, divinyl ether, 1,3-diallyl
2-(2-hydroxyethyl) citrate, vinyl allyl citrate, allyl vinyl
maleate, diallyl itaconate, di(2-hydroxyethyl) itaconate, divinyl
sulfone, hexahydro-1,3,5-triallyltriazine, triallyl phosphite,
diallyl benzenephosphonate, triallyl aconitate, divinyl
citraconate, trimethylolpropane trimethacrylate and diallyl
fumarate.
[0090] In another embodiment, the cross-linked polymer strands have
an average molecular weight of from about 3,000 to about 2,000,000.
In alternative embodiments, the cross-linked polymer strands have
an average molecular weight of from about 3,000 to about 200,000,
or alternatively from about 3,000 to about 20,000, or alternatively
from about 30,000 to about 2,000,000, or alternatively from about
300,000 to about 2,000,000, or alternatively from about 100,000 to
about 1,000,000, or alternatively from about 50,000 to about
1,500,000.
[0091] In another embodiment, the process described above further
comprises adding an effective occluding amount of one or more
working substance(s) to the polar liquid(s) of the polymerization
system prior to polymerization. In another embodiment, the
effective amount of the working substance-containing gel
nanoparticles occlude from about 0.1 to about 90 weight percent
working substance(s)-containing liquid. In alternative embodiments,
the effective amount of the working substance-containing gel
particles occlude from about 1 to about 90 weight percent working
substance-containing liquid, or alternatively from about 10 to
about 90 weight percent, or alternatively from about 0.1 to about
70 weight percent, or alternatively from about 0.1 to about 50
weight percent, or alternatively from about 0.1 to about 20 weight
percent, or alternatively from about 10 to about 50 weight
percent.
[0092] In another embodiment, the method comprises adding an
effective amount of one or more first working substance(s) to the
polymerization system to give a first working substance-containing
liquid, wherein after polymerization, a portion of the first
working substance-containing liquid is occluded by the polymeric
nanoparticles; and adding an effective amount of one or more second
working substance(s) to the particulate powder and dry blending to
give a second working substance-containing particulate powder,
wherein the first working substance(s) may be the same as or
different than the second working substance(s). In a further
embodiment, from 0.1 to 90 weight percent of the first working
substance(s) is occluded by the plurality of hydrogel particles and
from 0.1 to 90 weight percent of the second working substance(s) is
entrapped between the nanoparticles.
[0093] In another embodiment, one or more working substance(s) is
added to the dry powder and blending to provide a working
substance(s)/particulate powder composite. In another embodiment,
the working substance(s)/particulate powder composite contains from
about 1 to 90 weight percent of working substance(s).
[0094] In another embodiment, the working substance(s) comprise one
or more biomedical agent(s), which may be the same or different. In
another embodiment, the biomedical agent(s) comprise(s) cells,
platelets or one or more tissue-growth scaffold materials. In a
further embodiment, one or more of the biomedical agent(s)
comprise(s) one or more pharmaceutical agent(s). In another
embodiment, the pharmaceutical agent(s) further comprises/comprise
one or more pharmaceutically acceptable excipient(s). In a further
embodiment, the pharmaceutical agent(s) comprises/comprise a
peptide, a protein or a poly-saccharide. In another embodiment, the
pharmaceutical agent(s) is/are useful for the treatment of wounds,
cancer, pain, infection or diseases of the eye. In another
embodiment, the pharmaceutical agent(s) is/are growth factors.
[0095] In another embodiment, the method further comprises adding
one or more pharmaceutically acceptable excipients to the dry
powder. In an embodiment, one or more pharmaceutically acceptable
excipients are from about 1 to about 50 weight percent of the dry
powder. In alternative embodiments, one or more pharmaceutically
acceptable excipients is from about from about 10 to about 50
weight percent weight percent of the dry powder, or alternatively
from about 20 to about 50 weight percent, or alternatively from
about 30 to about 50 weight percent, or alternatively from about 40
to about 50 weight percent, or alternatively from about 1.0 to
about 40 weight percent, or alternatively from about 1.0 to about
30 weight percent, or alternatively from about 1.0 to about 20
weight percent, or alternatively from about 1.0 to about 10 weight
percent, or alternatively from about 5.0 to about 45 weight
percent.
[0096] In another embodiment, the pharmaceutically acceptable
excipient(s) is/are a water soluble filler material(s).
[0097] The invention also provides a method of forming a
shape-conforming, shape-retentive aggregate dressing in situ on a
wet wound site by applying a dry powder of polymeric nanoparticles
to the wet wound site wherein the dry powder comprises a plurality
of gel particles having an average diameter of less than
1.times.10.sup.-6 m, wherein the gel particles comprise an
effective amount of a plurality of polymeric strands obtained by
polymerization of an effective amount of a monomer or two or more
monomers, at least one of which is a 2-alkenoic acid, a hydroxy
(2C-4C) alkyl 2-alkenoate, a dihydroxy (2C-4C) alkyl 2-alkenoate, a
hydroxy (2C-4C) alkoxy (2C-4C) alkyl 2-alkenoate, a (1C-4C) alkoxy
(2C-4C) alkoxy (2C-4C) alkyl 2-alkenoate or a vicinyl epoxy (1C-4C)
alkyl 2-alkenoate, in a polar liquid or a mixture of two or more
miscible liquids, at least one of which is polar, and an effective
amount of a surfactant to stabilize the plurality of gel
particles.
[0098] In another embodiment, this invention provides a method of
forming a shape-conforming, shape-retentive aggregate biomaterial
in vivo in or on a wet bodily tissue, by applying a dry powder of
polymeric nanoparticles to the wet bodily tissue wherein the dry
powder comprises a plurality of gel particles having an average
diameter of less than 1.times.10-6 m, wherein the gel particles
comprise an effective amount of a plurality of polymeric strands
obtained by polymerization of an effective amount of a monomer or
two or more monomers, at least one of which is a 2-alkenoic acid, a
hydroxy (2C-4C) alkyl 2-alkenoate, a dihydroxy (2C-4C) alkyl
2-alkenoate, a hydroxy (2C-4C) alkoxy (2C-4C) alkyl 2-alkenoate, a
(1C-4C) alkoxy (2C-4C) alkoxy (2C-4C) alkyl 2-alkenoate or a
vicinyl epoxy (1C-4C) alkyl 2-alkenoate, in a polar liquid or a
mixture of two or more miscible liquids, at least one of which is
polar, and an effective amount of a surfactant to stabilize the
plurality of gel particles. Claim 41 The polymeric nanoparticles
absorb bodily fluid and coalesce into a shape-conforming
biomaterial held together by non-covalent forces comprising
hydrophilic-hydrophobic particle interactions and hydrogen bonding
between the particles and the bodily fluid in the voids between the
particles.
[0099] The compositions of this invention are useful to treat
wounds by applying the dry powder of polymeric nanoparticles
prepared by a method comprising polymerizing an effective amount of
a monomer or two or more monomers, at least one of which is a
2-alkenoic acid, a hydroxy (2C-4C) alkyl 2-alkenoate, a dihydroxy
(2C-4C) alkyl 2-alkenoate, a hydroxy (2C-4C) alkoxy (2C-4C) alkyl
2-alkenoate, a (1C-4C) alkoxy (2C-4C) alkoxy (2C-4C) alkyl
2-alkenoate or a vicinyl epoxy (1C-4C) alkyl 2-alkenoate, in a
polar liquid or a mixture of two or more miscible liquids, at least
one of which is polar, and an effective amount of a surfactant and
lyophilizing for removal of liquids such that the amount of liquid
remaining in the polymeric nanoparticles is less than 10% w/w. In a
further embodiment, the dry powder further comprises one or more
tissue-growth scaffold materials or pharmaceutical agent(s). In a
further embodiment, the dry powder further comprises collagen,
hyaluronic acid, pharmaceutical agent(s) useful for the treatment
of wounds, for the treatment of cancer, for the treatment of pain,
for the treatment of ocular disease, or the pharmaceutical agent(s)
that are growth factors and antibiotics. In a further embodiment,
the pharmaceutical agent is lidocaine, erythromycin, doxycycline or
rifampin. In a further embodiment, the pharmaceutical agents are
VEGF and PDGF polypeptides.
[0100] The wound dressings and biomaterials of this invention can
be formed by first polymerizing specific monomers in a suspension
system comprising a liquid or a mixture of polar, miscible liquids
and a surfactant resulting in discrete gel nanoparticles, wherein
the particles are then purified, isolated, dried and applied to a
wet wound forming in situ dressings that are integral,
shape-conforming and shape-retentive. The unique chemical and
physical properties of these hydrogel nanoparticles absorb some of
the blood or exudate from the wound, causing them to coalesce and
be held together as an integral dressing. That is, the particles of
this invention, once exposed to a polar liquid such as blood or
exudate, which is primarily water, white blood cells, fibrin, and
other biological compounds, absorb some of the fluid, coalesce and
are held together by strong inter-particle and particle-liquid
interactions such as, without limitation, hydrophobic-hydrophilic
interactions and hydrogen bonding, the latter by virtue of the fact
that the at least one of the monomers used to produce the polymer
strands that make up the gel particle of this invention must
comprise one or more hydroxy groups and/or one or more ester
groups. In addition, some of the non-absorbed exudate remains
trapped in the void spaces between the particles after they
coalesce, and since the exudate is a polar material, strong
hydrogen bonding occurs between the particles and the exudate. An
important requirement for the formation of the wound dressings in
situ using dry, nanoparticulate powder is that the wound site must
be wet, that is wound fluid must be present otherwise particle
aggregation cannot occur in situ.
[0101] However, it is also possible to form a shape-retentive
aggregate wound dressing, with or without a medicinal agent, on a
bodily tissue that is not wet or releasing a minimum amount of
exudate. In this case, using the teachings of the previous cited
U.S. Patent Application Publ. No.: US 2004/0086548A1 and the
teachings of this invention disclosure, the dry nanoparticulate
powder is mixed with a polar liquid or mixture thereof and
immediately applied to a bodily tissue. The nanoparticles coalesce
into a shape-retentive and shape-conforming aggregate dressing, by
virtue of the strong particle-particle and particle-liquid
interactions as previously discussed. The only requirements to
utilize these types of dressings is that the polar solvent or
mixtures thereof are safe, non toxic and approved by the FDA for
topical and systemic applications.
[0102] In addition, one can also add a volatile solvent to a
mixture of the dry nanoparticle powder and polar, plasticizing
liquid or mixture thereof, homogenize the components and package
the resulting mixture in a sealable container to prevent
evaporation of the solvent. Upon application to a non-exuding wound
surface or intact skin, the volatile solvent evaporates leaving a
shape-retentive aggregate dressing on the application site.
[0103] The gel nanoparticles are prepared in a polymerization
system that consists of one or more monomers selected generally
from those monomers that, on polymerization, provide a polymer that
is water insoluble, whether crosslinked or not, and capable of
hydrogen bonding. General classes of monomers that have this
capability include, without limitation, a hydroxy(2C-4C)alkyl
2-alkenoate, a dihydroxy(2C-4C) alkyl 2-alkenoate, a
hydroxy(2C-4C)alkoxy(2C-4C)alkyl 2-alkenoate, a
(1C-4C)alkoxy(2C-4C)alkoxy(2C-4C)alkyl 2-alkenoate and a vicinyl
epoxy(1C-4C)alkyl 2-alkenoate and combinations thereof.
[0104] The monomers include 2-hydroxyethyl acrylate, 2-hydroxyethyl
methacrylate, diethylene glycol monoacrylate, diethylene glycol
monomethacrylate, 2-hydropropyl acrylate, 2-hydroxypropyl
methacrylate, 3-hydroxypropyl acrylate, 3-hydroxypropyl
methacrylate, glycerol methacrylate, dipropylene glycol
monomethacrylate, dipropylene glycol monoacrylate, glycidyl
methacrylate, 2,3-dihydroxypropyl methacrylate, and mixtures
thereof. Particular monomers are 2-hydroxyethyl methacrylate
(HEMA), 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate,
and glycerol methacrylate.
[0105] Co-monomers that are not capable of hydrogen bonding may be
added to the polymerization system to modify the physical and
chemical characteristics of the resulting gel particles. Examples
of co-monomers that may be used in conjunction with the above
monomers are, without limitation, acrylamide,
N-methylmethacrylamide, N,N-dimethacrylamide,
methylvinylpyrrolidone, N,N-dimethylaminoethyl methacrylate
N,N-dimethylaminoethyl acrylate. Other co-monomers capable of
hydrogen bonding, without limitation, such as acrylic acid and
methacrylic acid may also be added to the polymerization system to
modify the ionic character and pH of the resulting gel
nanoparticles if desired.
[0106] In addition, non-polymerizing additives such as, without
limitation, alkyl alkanoates as exemplified by methyl butyrate,
butyl acetate, etc. may be added to the polymerization reaction to
further modify the physical and chemical characteristics of the
resulting gel particles.
[0107] A cross-linking agent also may be added to the
polymerization system to strengthen the three-dimensional structure
of the resulting gel particles. The cross-linking agent can be
non-degradable, such as, without limitation, ethylene glycol
diacrylate or dimethacrylate, 1,4-butylene dimethacrylate,
diethylene glycol dimethacrylate, propylene glycol dimethacrylate,
diethylene glycol dimethacrylate, dipropylene glycol
dimethacrylate, diethylene glycol diacrylate, dipropylene glycol
diacrylate, divinyl benzene, divinyltoluene, triallyl melamine,
N,N'-methylene bisacrylamide, diallyl maleate, divinyl ether,
diallyl monoethylene glycol citrate, vinyl allyl citrate, allyl
vinyl maleate, divinyl sulfone, hexahydro-1,3,5-triallyltriazine,
triallyl phosphite, diallyl benzene phosphonate, a polyester of
maleic anhydride with triethylene glycol, diallyl aconitrate,
divinyl citraconate, trimethylolpropane trimethacrylate and diallyl
fumarate. Other non-degradable cross-linking agents will become
apparent to those skilled in the art based on the disclosures
herein and are within the scope of this invention.
[0108] The chemical composition of the polymers making up the
individual gel particles comprising the resulting wound dressing
aggregates formed in situ are stable and do not readily degrade
under a wide range of environmental or physiological conditions.
The aggregate dressings formed in situ remain in place until the
wound heals and/or the wound dries out. On the other hand, the
aggregate dressings and/or biomaterials formed in vivo can be
designed, based on the specific application, such they will lose
strength or integrity under selected conditions in a controllable
fashion. For example, without limitation, by selecting appropriate
additives, they can be entrapped in the aggregate matrix as it is
being formed such that the resulting aggregate dressings will
become more porous as the additive(s) change(s) structure,
composition and/or reactivity upon exposure to variety of
environmental and/or physiological conditions.
[0109] When the liquid for use in the polymerization system of this
invention is water, the particles are hydrogel particles.
[0110] Certain organic liquids may also be used in the
polymerization system of this invention. In general, they should
have boiling points above about 60.degree. C., or alternatively
above about 80.degree. C., 100.degree. C., 120.degree. C.,
140.degree. C. 160.degree. C., 180.degree. C. or about 200.degree.
C. Presently organic liquids that may be used are biologically
inert, non-toxic, polar, water-miscible organic liquids such as,
without limitation, ethylene glycol, propylene glycol, dipropylene
glycol, butanediol-1,3, butanediol-1,4,
hexanediol-2,5,2-methyl-2,4-pentanediol,
heptanediol-2,4,2-ethyl-1,3-hexanediol, diethylene glycol,
triethylene glycol, tetraethylene glycols, and the higher
polyethylene glycols and other water-soluble oxyalkylene
homopolymers and copolymers having a molecular weight up to about
2000, preferably up to about 1600. For example, without limitation,
hydroxy-terminated polymers of ethylene oxide having average
molecular weights of 200-1000, water-soluble
oxyethyleneoxypropylene polyol (especially glycol) polymers having
molecular weights up to about 1500, preferably up to about 1000,
monoacetin, glycerine, tri(hydroxyethyl) citrate, ethylene glycol
monomethyl ether, di(hydroxypropyl) oxalate, hydroxypropyl acetate,
glyceryl triacetate, glyceryl tributyrate, liquid sorbitol ethylene
oxide adducts, liquid glycerine ethylene oxide adducts, diethylene
glycol monoethyl ether, and ethylene glycol diacetate, may be
used.
[0111] In an embodiment of this invention, hydrogel particles,
having nominal sizes in the 10.sup.-9 meters to the 10.sup.-6 m
range are produced by redox, free radical or photo-initiated
polymerization in water containing a surfactant. In this manner,
particles of relatively narrow polydispersity can be produced. If,
for a particular application, such as, without limitation, release
of biologically active substances over an extended period of time
is desired, it may be advantageous to produce and isolate particles
of broad polydispersity that comprise a medicated wound dressing
formed in situ or therapeutic biomaterial produced in vivo.
[0112] If, on the other hand, the goal is sequential release of a
drug or burst release at different times rather than continuous
release, two or more groups of particles of different sizes but
narrow polydispersity within each size may be used. For example,
without limitation, gel particles of different sizes but narrow
polydispersity may be formed using the techniques described herein
in separate polymerization systems that contain a particular
biologically active substance. The substance-containing particles,
after isolation and drying, may then be combined as a single powder
and applied to a wound to produce a medicated shape-retentive
dressing. Due to the difference in size of the particles, the
biologically active substance will be burst-released at different
times. Similarly, using the same technique but adding a first
biologically active substance to one of the polymerization systems
and a different biologically active substance to the second
polymerization system will result in particles that will release
their particular active substance at different times, i.e.,
sequential release.
[0113] Biologically active substances can also be introduced to the
wound dressings and biomaterials described in this invention by
mixing isolated and dried nanoparticles with these various active
substances. After application to a wet wound, the dressing forms in
situ and some of the active(s) is trapped between the void spaces
between the particles comprising the dressing. These actives will
be released from the dressing over a prolonged period of time, to
enhance wound healing, and the release rate(s) will be affected by
the physical properties of the active, such as molecular weight and
water solubility, in addition to the size of the nanoparticles
comprising the dressing. It is clear to one skilled in the art that
a variety of medicated dressings and/or biomaterials can be
produced, for example, using dry nanoparticles of various sizes
containing occluded actives in combination with or without other
biologically active compounds that are blended together in powder
form and applied to a wound, and all such dressings are within the
scope of this invention disclosure.
[0114] Numerous factors will affect the chemical and physical
characteristics of the aggregates of this invention. One is the
molecular weight of the polymer used to form the individual
hydrogel nanoparticles. It has been found that hydrogel particles
consisting of low molecular weight polymers will generally not form
stable, strong aggregate wound dressings in situ. Thus, higher
molecular weight polymers are used in this invention. While the use
of cross-linking agents can ameliorate some of the problems
associated with low molecular weight polymers, too much
cross-linking agent may be detrimental. If the hydrogel particles
contain a large amount of cross-linking agent and/or if the
cross-linking agent is highly hydrophobic, the resulting polymeric
network may not permit optimal absorption and occlusion of blood or
exudate resulting in less desirable wound dressings. So, the
polymers that comprise the gel particles of this invention have
molecular weights in the range of about 3,000 to about 2,000,000
Da. This may be accomplished by selecting an appropriate commercial
monomer, by using a polymerization system that gives polymers of in
the desired molecular weight range or by including a cross-linker
in the polymerization system to join together short polymer strands
to reach the desired molecular weight range.
[0115] Particle size will also affect the characteristics of the
aggregate wound dressings. It has been determined that smaller gel
particles will generally absorb and trap liquid more easily and
faster due to surface area and will give a more resilient dressing
matrix. Gel particles having sizes, again as characterized by their
average diameters, in the range of about 1 to about 1,000 nm, or
alternatively from about 10 to about 800 nm, can be used.
[0116] If a cross-linking agent is used, its chemical composition
and the amount used, i.e., the resulting cross-linking density,
will affect the characteristics of the particles as previously
discussed and thereupon will affect the characteristics of the
wound dressings formed. For example, too much crosslinker would
provide polymer strands of a higher molecular weight, however may
also create too much hydrophobic character and hydrophobic domains
throughout the hydrogel nanoparticles, thus preventing the critical
strong inter-particle and particle-liquid interactions such as,
without limitation, hydrophobic-hydrophilic interactions and
hydrogen bonding to occur during the formation of the wound
dressings prepared in situ on a wound or biomaterials formed in
vivo. The amount of cross-linking agent used in preparing gel
particles of this invention is preferably in the range of about
0.001 to about 10, preferably about 0.1 to about 2 mol percent of
monomer.
[0117] The chemical composition and amount of surfactant present in
the isolated, dry nanoparticle powder will affect the aggregation
rate when exposed to a polar liquid and the physical and chemical
characteristics of the resulting aggregate wound dressings of this
invention. During the isolation process, a certain amount of
surfactant is required to prevent self aggregation of the particles
as they become concentrated during the drying cycle. However, too
much surfactant would prevent the dry particles from forming
optimum wound dressing aggregates upon exposure to blood, wound
exudate or other polar liquids. The amount of surfactant present in
the nanoparticulate powder is preferably in the range of about 0.1
to 6 weight percent of the nanoparticle powder. It is also
important to note that the isolation and drying processes performed
on these gel nanoparticles must be such to prevent or minimize the
particles from concentrating and self-aggregating, at which point
the strong particle-particle and particle-liquid interactions
overpower the inherent ability for the surfactant to keep the
particles from coalescing. Isolation and drying processes such as
spray drying and lyophilization are used, whereas direct
evaporation is not since self-aggregation occurs extensively and
the resulting dry powder will not form a viable dressing in situ
when applied to a wet wound site. It is clear to one skilled in the
art that other isolation and drying processes can be used as long
as self-aggregation is minimized or prevented. The various
parameters discussed above are, of course, inter-dependent.
[0118] In one embodiment of this invention, hydrogel nanoparticles
are produced by polymerizing non-ionic monomers in water containing
a surfactant. The suspension of hydrogel particles is treated to
remove unreacted monomer and other impurities. The particles are
isolated, dried and the particulate powder is applied to a wound or
to a bodily tissue in vivo, which absorbs some exudates, blood or
other bodily fluid and coalesces into a shape-retentive,
shape-conforming wound dressing or biomaterial. The dressing
remains integral and shape-retentive by virtue of the strong
inter-particle and particle-liquid interactions such as, without
limitation, hydrophobic-hydrophilic interactions and hydrogen
bonding. That is, by applying the nanoparticle hydrogel powder into
a medium of higher ionic strength, e.g. PBS, serum, wound exudate
or other bodily fluid, the particles self-assemble into a compact
elastic, shape-retentive aggregate dressing. In an embodiment, the
medium is in vivo, that is, a bodily tissue, and the
shape-retentive aggregate assumes and retains the shape of the
region of the body into which the powdered is applied. If the
medium is ex vivo, it may be, without limitation, be further
pressure-shaped, extruded, or molded into a desired shape, which it
will retain so long as the aggregate is maintained in the hydrated
state.
[0119] The aggregate wound dressings of this invention have many
applications including, without limitation, delivery of a
biologically active substance or substances to a predetermined
location such as a wound site. The target may be veterinary,
involving delivery of medicaments to animals such as reptiles,
mammals and birds. In particular, the target may be a human
involving the controlled, directed delivery of pharmaceutical
agents to the patient.
[0120] Another embodiment of this invention involves dissolving or
suspending the biologically active agent in the polymerization
system prior to polymerization. As the polymerization reaction
proceeds and hydrogel nanoparticles form, liquid containing the
biologically active substance is occluded by the forming particles.
Un-occluded biologically active agent is then removed when the
particles are treated to remove excess monomer and surfactant. The
suspension of biologically active substance-containing particles is
then isolated and dried to produce nanoparticulate powder. The
drying process is done by traditional means including, without
limitation, spray drying and lyophilization. The powder may then be
introduced either ex vivo or in vivo, in the latter case
introduction preferably being by applying the powder to a wound
site whereupon the particles coalesce into a shape-retentive,
shape-conforming aggregate medicated dressing.
[0121] It is also an embodiment of this invention to remove
non-occluded biologically active agent from the suspension system
along with the excess monomer and with the surfactant, isolate and
dry the nanoparticles containing the occluded biologically active
agent, and then add an entirely different biologically active
substance to the nanoparticulate powder prior to forming a wound
dressing in situ so as to entrap the latter during aggregate
formation. The substance entrapped in the voids in the aggregate
will normally be released at a very different rate from the
substance occluded by the particles. In this manner, a broad range
of delivery rates can be achieved. Diversity in delivery profile
can also be achieved by varying the chemical composition and
particle size of the individual hydrogel particles comprising the
wound dressing aggregates.
[0122] If the biomaterial aggregate is produced in vivo, a certain
amount of biologically active substance will be entrapped in the
void spaces between the particles, depending upon the physical
properties such as type and size of the biologically active
substance and the rate of aggregate formation. The rate of
aggregate formation is a function of the particle size and
composition of the gel nanoparticles, the type and amount of
surfactant or combination of surfactants present in the dry
nanoparticulate powder, the polar medium to which the powder is
applied and the temperature of the medium.
[0123] In addition to the above, other water soluble substances may
be added to the dry gel nanoparticles of this invention to alter
the aggregation and rate of the shape-retentive aggregate formed on
introduction into a medium and, therefore, the amount and
subsequent release rate of the entrapped active agent can be
further controlled. In addition, these water soluble excipients can
be used to alter the porosity over time of the wound dressing
formed in situ, as they dissolve away from the aggregate upon
exposure to wound exudates or blood. Using one or more of the above
procedures, zero-order, or at least pseudo-zero order, release
rates should be attainable for a wide range of biologically active
agents.
[0124] The type and amount of an agent that can be occluded by a
gel particle or entrapped in a shape-retentive aggregate dressing
or biomaterial of this invention depends upon a variety of factors.
First and foremost, the agent cannot interfere, due to its size,
surface charges, polarity, steric interactions, etc., with the
formation of discrete gel particles or the coalescence of the gel
particles into a shape-retentive aggregate after introduction into
a medium, such as a wound, either of which would defeat the purpose
of this invention. Once it is determined that the foregoing is not
a problem, the size of the hydrogel particles most directly affects
the quantity of substance that can be incorporated within the
particle. The size of the particles themselves will dictate the
maximum amount of agent that can be occluded while the
polydispersity of the particles will affect the resulting pore size
of aggregate dressings formed in situ. Relatively small agents,
such as individual antibiotic molecules, antimicrobial agents and
analgesics may be occluded in small gel nanoparticles and easily
entrapped in aggregates formed from small these gel particles,
while substantially larger agents such as monoclonal antibodies,
proteins, peptides, polysaccharides and other macromolecules may be
difficult to occlude within these nanoparticles and will require
aggregate dressings comprised of much larger particles and/or
broader polydispersity to entrap them efficiently.
[0125] Using the methods herein, precise control of delivery
kinetics can be achieved. That is, gel particles of differing sizes
and chemical compositions can be loaded with a particular agent and
the agent can be released over various timeframes. In addition,
some of the substance might be occluded in the gel particles and
some might be entrapped in the voids between particles of the
shape-retentive wound dressing aggregate to provide even more
delivery flexibility.
[0126] Using the above methods, different agents, even normally
incompatible agents, can be loaded into gel particles of this
invention and sequentially or simultaneously released. Sequential
release will prevent incompatible agents from encountering one
another. Simultaneous release permits delivery of two or more non-
or minimally active bioactive agents that, when combined, form a
potent drug. In this manner, the formation of the active species
can be postponed until the aggregate containing the precursors has
been formed at the wound site when the nanoparticles combine with
blood or exudate and coalesce to provide prolonged active release
to the underlying wound bed.
[0127] In another aspect of this invention, gel particles of two or
more different sizes and narrow polydispersity with regard to each
other are used at a to form shape-retentive wound dressing
aggregates of this invention. The trapping efficiency of substances
and their subsequent release rate should be substantially different
than those of aggregates formed using single size narrow
polydispersity particles. Without being held to any particular
theory, it is believed that this may be due to the possibility
that, during aggregation in the presence of a substance to be
entrapped, the voids between the particles comprising the wound
dressing aggregate are more efficiently filled by mixed
polydispersity particles. The examples which follow demonstrate
that, for a specific agent of a given size, the size and ratio of
sizes of particles comprising an aggregate dramatically affect a
forming aggregate's efficiency in trapping an agent and its
subsequent release rate. Using this approach, the release rate of a
particular substance might be tailored to approach pseudo-zero
order kinetics using appropriate particle sizes and ratio of
sizes.
[0128] Thus, the present invention provides an extremely versatile
substance delivery platform for wound dressings formed in situ, in
particular with regard to biologically active agent delivery and
most particularly with regard to pharmaceutical agent delivery. In
a particular embodiment, wound dressings for decubitus ulcers,
vascular ulcers, second, third and fourth degree burns and skin
donor site with or without incorporated antibiotics, pain killers,
growth factors or vascular signaling agents could be formed
directly at a wound site in situ by introducing the nanoparticulate
powder into or onto a wet wound and a skin donor site. A
pharmaceutical agent or combination of agents may be delivered
continuously over an extended time period, in bursts at specific
time intervals, simultaneously after a predetermined delay time so
that two or more agents can interact synergistically only after
formation of the aggregate dressing containing them at a desired
target site, or sequentially so that one agent can act at a target
site before the next agent is released or so that two or more
agents can synergistically interact.
[0129] Another embodiment of this invention is the use of the
shape-retentive aggregate materials formed in situ by introducing
powdered nanoparticles to bodily fluid, as biomaterials useful in
orthopedic applications such as tissue scaffolding. The macroporous
structure of the shape-retentive and shape-conforming aggregates of
this invention provides a composition that should permit
substantial ingrowth, a property not found in typical microporous
bulk hydrogels. In addition, the aggregates of this invention
exhibit physical properties, such as elastic, shear and bulk
moduli, that are significantly improved over those of conventional
bulk hydrogels. Possible orthopedic applications of the methods of
this invention include, without limitation, cartilage and bone
repair, meniscus repair/replacement, artificial spinal discs,
artificial tendons and ligaments, and bone defect filler.
[0130] The shape retentive property of the aggregate materials of
this invention and their ability to be formed in situ and retain
water suggest numerous other in vivo uses. For example, a medicated
or unmedicated aggregate could be molded into a soft contact lens.
A soft, pliable, biocompatible drug delivery device to treat
serious eye diseases could be formed in situ placing the powdered
hydrogel nanoparticles in which an ocular pharmaceutical agent has
been occluded or entrapped behind the eye. A shape-retentive
aggregate could be formed in a periodontal pocket by introducing
the nanoparticulate powder in which a bone growth factor is either
occluded by the particles or entrapped in the forming aggregate.
The aggregate might also have within it occluded or entrapped
antibiotic for control of infection by sustained delivery of the
antibiotic while bone regeneration is being stimulated through the
controlled release of the bone growth factor. As an added benefit,
the soft, biocompatible shape-retentive aggregate would provide
comfort at the site due to its inherent softness and
conformability.
[0131] The aggregates of this invention produced by the methods
hereof might be used as carriers for a host of materials other than
biomedical agents. For example, without limitation, metals or metal
ions could be occluded in the gel particles, entrapped by the
aggregate or both. The metals and/or ions would confer varying
degrees of conductivity and radiopacity of the aggregates that
could have other uses such as in the electrical stimulation of
wound healing.
[0132] These and may other uses for the shape-retentive,
shape-conforming aggregate wound dressings and biomaterials of this
invention will become apparent to those skilled in the art based on
the disclosures herein. Such uses are within the scope of this
invention.
Example 1
Hydrogel Nanoparticle Synthesis Using HEMA
[0133] A 500 mL media bottle equipped with a stir bar was charged
with 4.52 g (34.8 mmol) hydroxyethyl methacrylate(HEMA) monomer,
77.74 mg (0.428 mmol) ethylene glycol dimethacrylate (EGDM), 0.2123
g (0.634 mmol) sodium dodecyl sulfate (SDS) and 240 mL milli-Q
H.sub.2O. The bottle was closed with a sparging cap and purged with
N.sub.2 for 1 hr at room temperature while stirring. Then, 0.166 g
potassium persulfate (K.sub.2S.sub.2O.sub.8) was dissolved into 21
mL of milli-Q H.sub.2O and added to the media bottle while
stirring. The bottle was transferred to a 40.degree. C. water bath
and held there for 12 hours. The resulting suspension of hydrogel
particles had an opalescent blue color. The particles were analyzed
by dynamic light scattering and found to have an average radius of
36.5 nm as shown in FIG. 1. The particles were purified by
tangential flow filtration and are stored in an aqueous suspension.
No flocculation was observed over several months.
Example 2
Hydrogel Nanoparticle Synthesis Using HPMA
[0134] A 150 mL media bottle equipped with a stir bar was charged
with 2.532 g (17.5 mmol) of hydroxypropyl methacrylate (HPMA)
monomer, 52.73 mg (0.266 mmol) of ethylene glycol
dimethacrylate(EGDM) crosslinker, 107.6 mg (0.3730 mmol) sodium
dodecylsulfate (SDS), and 118 mL of nitrogen degassed Milli-Q
H.sub.2O. The bottle was closed and stirred to form a clear
solution. In a separate vial, 83 mg of K.sub.2S.sub.2O.sub.8 was
dissolved into 2 mL of Milli-Q H.sub.2O and added to the media
bottle while stirring. The media bottle with clear solution was
transferred into a 40.degree. C. water bath and held at constant
temperature for 12 hours. The resulting suspension of hydrogel
nanoparticles had an opalescent blue color. The particles were
analyzed by laser light scattering and found to have an average
particle size of 21.3 nm and a size range from 14 nm to 41 nm. The
suspension had approximately 1% solid polymer by mass. To date, the
suspension of hydrogel nanoparticles resisted flocculation or
aggregation for two years at room temperature.
Example 3
Hydrogel Nanoparticle Copolymer Synthesis Using HEMA and HPMA
[0135] Using the synthetic method of Example 1, copolymer
nanoparticles were produced using HEMA monomer and HPMA monomer.
Table 1 shows the relative masses and mmol of monomers added to the
150 mL media bottles:
TABLE-US-00001 TABLE 1 Mass mmol Mass mmol Sample HEMA HEMA HPMA
HPMA 95:5 4.30 g 33.06 0.251 g 1.74 pHEMA:HPMA 90:10 4.07 g 31.32
0.501 g 3.48 pHEMA:HPMA 85:15 3.85 g 29.58 0.752 g 5.22 pHEMA:HPMA
75:25 3.40 g 26.10 1.25 g 8.70 pHEMA:HPMA 50:50 2.26 g 17.40 2.51 g
17.40 pHEMA:HPMA
[0136] Each media bottle was then charged with 52.73 mg (0.266
mmol) EGDM, 107.6 mg (0.3730 mmol) sodium dodecylsulfate (SDS), and
118 mL of nitrogen degassed Milli-Q H.sub.2O. The bottles were
capped and stirred for 30 minutes at room temperature. In 5
separate vials, 83 mg of K.sub.2S.sub.2O.sub.8 was dissolved into 2
mL of Milli-Q H.sub.2O respectively and added to each media bottle
while stirring. The media bottles with clear solutions were
transferred into a 40.degree. C. water bath and held at constant
temperature for 12 hours. The resulting suspension of hydrogel
nanoparticles had an opalescent blue color.
Example 4
Hydrogel Nanoparticle Synthesis Using GMA
[0137] A 2000 mL media bottle equipped with a stir bar was charged
with 44.5 g (277 mmol) of glycerol methacrylate (GMA) monomer, 92
mg (0.464 mmol) of ethylene glycol dimethacrylate(EGDM)
crosslinker, 2.04 g (0.3730 mmol) sodium dodecylsulfate (SDS), and
118 mL of nitrogen degassed Milli-Q H.sub.2O. The bottle was closed
and stirred to form a clear solution. In a separate vial, 83 mg of
K.sub.2S.sub.2O.sub.8 was dissolved into 2 mL of Milli-Q H.sub.2O
and added to the media bottle while stirring. The media bottle with
clear solution was transferred into a 40.degree. C. water bath and
held at constant temperature for 12 hours. The resulting suspension
of hydrogel nanoparticles had an opalescent blue color. The
particles were analyzed by laser light scattering and found to have
an average particle size of 21.3 nm and a size range from 14 nm to
41 nm. The suspension had approximately 1% solid polymer by mass.
To date, the suspension of hydrogel nanoparticles resisted
flocculation or aggregation for two years at room temperature.
Example 5
Hydrogel Nanoparticle Copolymer Synthesis Using HEMA and GMA
[0138] Using the synthetic methods as above, nanoparticles were
produced using HEMA and glycerol methacrylate monomers. Table 2
shows the relative masses and mmol of monomers added to the 2000 mL
media bottles.
TABLE-US-00002 TABLE 2 Mass mmol Mass mmol Sample HEMA HEMA GMA GMA
90:10 40.0 g 307.36 4.47 g 27.78 pHEMA:GMA 75:25 33.35 256.30 11.11
g 69.46 pHEMA:GMA
[0139] Each media bottle was then charged with 80 mg (0.404 mmol)
of EGDM crosslinker, 20.4 g (7.09 mmol) sodium dodecylsulfate
(SDS), and 2000 mL of nitrogen-degassed Milli-Q H.sub.2O. The
bottles were closed and stirred to form clear solutions. In two
separate vials, 1.44 g (6.31 mmol) of
(NH.sub.4).sub.2S.sub.2O.sub.8 was dissolved into 20 mL of Milli-Q
H.sub.2O and added to the 2000 mL media bottles while stirring. The
media bottles with clear solution were transferred into a
50.degree. C. water bath and held at constant temperature for 12
hours. The resulting suspensions of hydrogel nanoparticles were
opalescent blue in color. The particles were analyzed by laser
light scattering and Table 4 shows the average particle sizes and
size ranges.
Example 6
Lyophilization of Nanoparticle Suspensions
[0140] The nanoparticle suspensions of examples 1-5 were frozen at
-80.degree. C. The solid suspensions were dried under vacuum at
room temperature in a VIRTIS lyophilization system to produce a
white powder. The powder was milled or sieved to produce particles
of uniform sizes. The density of the milled powder was
approximately 200 mg/mL and the density of the sieved particles was
approximately 120 mg/mL. The particles remained as a stable powder
with no change in appearance or bulk density for 6 months at room
temperature.
Example 7
Redispersion of Dry Nanoparticle Powder
[0141] The lyophilized powders of example 6 were exposed to various
solvents to determine whether the powders from milling or sieving
could be redispersed as suspensions. The following solvents showed
the ability to redisperse the particles:
[0142] Water, ethanol, methanol, isopropanol, and butanol.
Non-polar solvents such as hexane or ethyl acetate would not allow
the powder to redisperse and formed insoluble masses of wetted
powder when combined with the lyophilized powder.
Example 8
Aggregation of Poly-HEMA Nanoparticle Powder in PBS
[0143] Poly-2-hydroxyethyl methacrylate lyophilized powder from
example 6 was added to phosphate buffered saline solution at
physiological pH and ionic strength. Within several seconds, the
powder coalesced forming an integral, strong aggregate film. FIG. 1
shows a photograph of the nanoparticle powder, the powder applied
to phosphate buffered saline and the resulting aggregate after
formation.
Example 9
Rate of Water Loss after Hydration and Aggregation of Copolymer
Nanoparticle Powders in PBS
[0144] Several nanoparticle powders of different chemical
compositions were exposed to phosphate buffered saline. FIG. 2
shows the results of the plots for water loss for these copolymer
aggregates composed of varying ratios of HEMA monomer, glycerol
methacrylate and hydroxypropyl methacrylate.
[0145] In FIG. 2, the plots show the average weight for a hydrogel
nanoparticle aggregate formed using 500 mg of powder in phosphate
buffered saline at pH=7.4. The aggregates were weighed and returned
and allowed to dry in an environmental chamber at 37.degree. C. The
plot shows that the aggregate materials containing GMA have the
highest initial water adsorption, due to its inherent higher
hydrophilic character than HEMA or HPMA. However, the loss of water
over time is more rapid for these aggregates. The copolymers of
pHEMA:HPMA have a lower initial solution adsorption but do not lose
water mass as rapidly.
Example 10
Rheology Data for Various Aggregate Films Formed from Nanoparticle
Powders and PBS
[0146] Table 3 below shows relative elasticities for different
types of nanoparticle aggregates. For a given study, tension was
placed on a nanoparticle aggregate after formation from a powder
and PBS while hydrated using a Duofield tensiometer actuating the
aggregate at a rate of 1 mm/second. Aggregates were cut to a
dogbone shape 1 cm in length and having a neck with dimensions of 1
mm.times.2 mm. Aggregates were stretched until failure and the
maximum tension at failure was observed and recorded for three
replicate trials.
TABLE-US-00003 TABLE 3 Elongation (mm) Tension at Failure (g)
Sample (StDev) (StDev) pHEMA 54 mm (3.54) 0.58 g (1.21) 90:10
pHEMA:GMA 98 mm (4.32) 0.12 g (1.13) pHPMA 6 mm (2.17) 5.9 g (1.98)
90:10 pHPMA:GMA 69 mm (7.83) 0.19 g (3.34) 95:5 pHEMA:HPMA 46 mm
(8.21) 0.71 g (1.31) 90:10 pHEMA:HPMA 41 mm (3.59) 1.3 g (2.91)
85:15 pHEMA:HPMA 38 mm (3.42) 2.7 g (1.83) 75:25 pHEMA:HPMA 22 mm
(4.31) 3.8 g (1.95) 50:50 pHEMA:HPMA 11 mm (3.11) 5.1 g (0.61)
[0147] General trends in the above data show that the materials
containing GMA coalesce to form aggregates, which have a high
elasticity but very low breaking strengths under elongation. Ratios
of higher GMA (15% or more) resulted in aggregates which were very
elastic but had little structural integrity; the materials
stretched beyond the limits of the actuator, however sharp changes
in pressure resulted in fracture and failure of the material. The
addition of the comonomer HPMA to the HEMA resulted in stronger,
less elastic materials, which maintained some of the elasticity of
the pHEMA but increased the breaking strength as the more
hydrophobic HPMA comonomer was increased. This reduction of
elasticity is due to the lower amount of absorption and adsorption
of PBS by the powder when the aggregate forms.
Example 11
Dry Blending of Bioactive Compounds with Nanoparticle Powder to
Produce Medicated Biomaterials
[0148] Poly-HEMA nanoparticle powder and HEMA/GMA copolymer
nanoparticle powders were dry blended with lidocaine or
erythromycin powder and upon exposure to PBS, aggregates formed
trapping the active between the particles comprising the aggregate.
The active is then released at a controlled rate, dependent upon
the particle size, the hydrophilic/hydrophobic character of the
polymer or copolymer nanoparticles comprising the aggregate and the
physical properties of bioactive compound used. As shown in FIGS. 3
and 4, the release rate can be tailored to provide a specific level
of active over a prolonged period of time. FIG. 3 shows the release
of lidocaine from three different aggregates and FIG. 4 shows the
release of erythromycin.
[0149] The FIGS. 3 and 4 show that for compositionally identical
aggregates, the molecule that is trapped and subsequently released
can have different release profiles. This is due to the physical
properties of the molecule that is entrapped between the
nanoparticles comprising an aggregate and the
hydrophilic/hydrophobic character of the aggregate. For example,
the relatively hydrophobic lidocaine molecule is released at a
slower rate as the amount of the hydrophilic glycerol methacrylate
comonomer is increased in the copolymer nanopartilce powder and the
rate of erythromycin increases since it is a more hydrophilic
active.
Example 12
Incorporation of 1,10 phenanthroline in PHEMA/PHPMA Nanoparticle
Aggregates
[0150] 1,10 phenanthroline, a hydrophobic protease inhibitor that
coordinates to metals in metalloproteases and interferes with
enzyme kinetics, was incorporated into nanoparticle aggregates
composed of mixtures of HEMA and HPMA nanoparticle powders. The
effective concentration of the metalloprotease is 0.1 mmol/L and it
has a UV-Vis absorption spectrum with a maximum absorbance at 510
nm (McCarty, R. E. Analytical Biochem., 205, 371-372, 1992). A
controlled release study was performed by milling 1 mg of 1,10
phenanthroline with 100 mg of hydrogel nanoparticle powder and
adding this to 100 mL of phosphate buffered saline to produce the
respective aggregate. The aggregates were transferred to 100 mL of
PBS and placed in a water bath at 37.degree. C. The amount of 1,10
phenanthroline eluting into PBS was spectophotometrically
determined at different time intervals. Poly-HEMA nanoparticles and
pHPMA nanoparticles were each produced with the following different
average diameters as shown in Table 4
TABLE-US-00004 TABLE 4 Sample Diameter pHEMA (A) 100 nm pHEMA (B)
42 nm pHPMA (A) 96 nm pHPMA (B) 38 nm
[0151] The particles were combined in the ratio of 85:15
pHEMA:pHPMA weight to weight and the mixed powders were milled with
1:10 phenanthroline to form composites containing 1 milligram of
1:10 phenanthroline per 100 mg of powder.
[0152] FIG. 5 shows the in vitro release of 1,10 phenanthroline
from aggregate biomaterials composed of mixtures of nanoparticles.
The plot demonstrates that it is possible to regulate the release
of 1,10 phenanthroline from nanoparticle aggregates using different
sizes and chemical compositions of nanoparticles to give controlled
doses in time periods from 1 day to 13 days.
Example 13
In Vivo Bacteria Killing Study
[0153] A study was designed to determine the effectiveness of
controlled release doxycycline and rifampin from nanoparticle
aggregates in cultures of infectious bacteria commonly found in
burns. The initial study was designed to determine if the
controlled release of the drugs was sufficient to perform effective
killing of the bacteria over a 14-day period. To simulate a
continuous infection, three bacterial strains, Staph Aureus,
Enterococcus, and Pseudomonas were each plated out onto separate
agar plates. 150 mg of nanoparticle aggregate containing 3 mg of
doxycycline and 1.5 mg of rifampin were prepared by dry blending
the antibiotics with nanoparticle powders and then adding the
powder to 5 mL of phosphate buffered saline. The intact aggregate
was allowed to form for 5 minutes. The aggregate was carefully
transferred to colonies of bacteria on dishes and the zone of
inhibition was photographed as shown below. Every 24 hours, a fresh
colony of bacteria was incubated and the same aggregate was
transferred to the new plate to determine the inhibition of the
bandage with antibiotic over time. The nanoparticle aggregate with
controlled released antibiotics was compared to a commercial,
non-controlled release, silver impregnated antibiotic bandage.
Bacteria Tested in Project:
[0154] Staphylococcus aureus ATCC 25923 (referred to as SA)
[0155] Pseudomonas aeruginosa ATCC 27853 (referred to as Ps)
[0156] Enterococcus faecalis ATCC 51299 (referred to as EF)
Material Used:
[0157] BBL Prompt Inoculation System for use with disc diffusion
susceptibility tests
Mueller Hinton Agar
[0158] Protocol: Place 20 mm punch of Aquacel Ag commercial bandage
or the aggregate containing both actives on the surface of the
inoculated disc. Transfer each respective dressing to newly
inoculated disc every 24 hours for duration of study and observe
the zone of inhibition. In this study, bacterial inhibition was
measured as the zone of inhibition around the disc formed in 24
hours for a new plate with colonies incubated for 6 hours. The
total inhibition for each included the 20 mm disc of either the
Aquacel material or aggregate dressing. Samples tested on Mueller
Hinton agar inoculated with separate strains of bacterium (BBL
Prompt method used for diluting the bacteria to the appropriate
1.5.times.10.sup.8 colony forming units per ml(CFU/mL). The plot of
inhibition for each bacteria is shown in FIG. 8.
[0159] From the above studies, the aggregate dressing material
provides inhibition of Staphylococcus aureus, Pseudomonas
aeruginosa, and Enterococcus faecalis over 18-21 days. A commercial
bandage of 1% silver impregnated hydrogel gauze provides inhibition
for 10-12 days for the same strains of bacteria.
Example 14
Wound Healing Studies
[0160] The images in FIG. 9 show the non-medicated nanoparticle
powder (a mixture of 85% poly-HEMA nanoparticles and 15% poly-HPMA
nanoparticles) applied to wounds of different diameters (2 cm, 4 cm
and 6 cm respectively) which were partial thickness (2 cm deep) at
different time points during healing. The powder is applied
directly on a wound and utilizes the exudates to form an aggregate
dressing.
[0161] In this study, the nanoparticle powder was applied to the
exuding wound surface and pressed into place. No secondary dressing
was applied. The standard of care commercial hydrogel dressing was
applied to the surface of the wound and required a secondary
dressing and daily changing. The nanoparticle aggregate dressing
required no changing of the dressing during wound healing and
showed no evidence of inflammation such as redness at the margin or
elevated TNF-.alpha. levels.
[0162] The dressing has also been applied to skin graft donor sites
in a porcine animal model. FIG. 10 shows the healing results over
seven days after forming an aggregate dressing on a porcine skin
graft donor site as compared to Aquacel.
[0163] FIG. 10 shows that the Aggregate material can be used as an
effective bandage for skin graft donor sites with healing
equivalent to or better than a commercial bandage.
Example 15
Incorporation of Growth Factors with Nanoparticle Powders and
Application of Growth Factor Releasing Bandages in a Wound Healing
Model
[0164] Hydrogel nanoparticle powders composed of 85:15 pHEMA:pHPMA
nanoparticles were combined with the growth factors, vascular
endothelial growth factor (VEGF) and platelet derived growth factor
(PDGF) and applied to wounds. Powders were prepared as follows:
[0165] A. 105 mL of a suspension of 85:15 pHEMA:pHPMA nanoparticles
in water were combined with 5 micrograms of VEGF protein. The
suspension was mixed thoroughly to insure homogeneity and
lyophilized yielding 2 g of powder which was divided into 5, 400
milligram fractions. Each fraction contained 1 microgram of
VEGF.
[0166] B. 105 mL of a suspension of 85:15 pHEMA:pHPMA nanoparticles
in water were combined with 20 micrograms of PDGF protein. The
suspension was mixed thoroughly to insure homogeneity and
lyophilized to yield 2 g of powder which was divided into 5, 400
milligram fractions. Each fraction contained 4 micrograms of PDGF
protein.
[0167] C. 105 mL of a suspension of 85:15 pHEMA:pHPMA nanoparticles
in water were combined with 5 micrograms of VEGF protein and 20
micrograms of PDGF protein. The suspension was mixed thoroughly to
insure homogeneity and lyophilized to yield 2 g of powder which was
divided into 5, 400 milligram fractions. Each fraction contained 1
microgram of VEGF and 4 micrograms of PDGF protein.
[0168] 1 inch by 1 inch full thickness wounds were formed on a pig
in a grid of 4 wounds.times.4 wounds for a total of 16 wounds. Each
wound was covered with one of the four types of bandages: [0169]
Nanoparticle powder containing 1 microgram of VEGF per 400
milligrams of bandage. [0170] Nanoparticle powder containing 4
micrograms of PDGF per 400 milligrams of bandage. [0171]
Nanoparticle powder containing both 1 microgram of VEGF and 4
micrograms of PDGF per 400 mg of bandage. [0172] Control
nanoparticle powder without growth factors.
[0173] The wounds were not covered with secondary bandages.
Biopsies were taken at 2, 7, 14 and 21 days from each wound site
and the samples were studied for histology.
[0174] Histology of Control and PDGF-Treated Wound is shown in FIG.
11. In the histology images shown, the biopsy on the right was from
a wound treated with the control bandage containing no active
growth factor. The biopsy on the left was from a wound treated with
PDGF-loaded nanoparticle aggregate bandage
[0175] Both biopsies are at day 7. In the control, the wound bed is
much deeper at 7 days and shows much less granulation. In addition,
there was greater fibroblast recruitment in the PDGF loaded wound.
The wound area is shown with the box in each histology image while
the right side of each image shows healthy tissue removed at the
wound margin in the biopsy. Similar results were found on day 14
and 21, with a significant increase in granulation.
[0176] Histology of Control and VEGF-Treated Wound is shown in FIG.
12. In the histology images shown, the biopsy on the right was from
a wound treated with the control bandage containing no active
growth factor. The biopsy on the left was from a wound treated with
VEGF-loaded nanoparticle aggregate bandage. The bandage contained 1
microgram of VEGF per gram of dressing. Both biopsies are at day
7.
[0177] In the control the wound is much deeper at 7 days and shows
much less granulation. In contrast, the VEGF treated wound shows a
dramatic increase in vasculature within the wound bed. The wound
area is shown with the box in each histology image while the right
side of each image shows healthy tissue removed at the wound margin
in the biopsy.
[0178] Histology of control and combined VEGF and PDGF-treated
wound is shown in FIG. 13. In the histology images shown, the
biopsy on the right was from a wound treated with the control
bandage containing no active growth factor. The biopsy on the left
was from a wound treated with combined PDGF and VEGF-loaded
nanoparticle aggregate bandage. Both biopsies are at day 7.
[0179] In the control the wound is much deeper at 7 days and shows
much less granulation. In addition, there is a drastic increase in
vasculature within the wound bed and an increased rhett formation
in the wound margin. The wound area is shown with the box in each
histology image while the right side of each image shows healthy
tissue removed at the wound margin in the biopsy. It is clear from
the above experiments that the incorporation of a growth factor or
combination thereof in the nanoparticle powder can have a
significant affect in wound healing.
Example 16
Producing a Nanoparticle Aggregate Dressing In Situ on a
Non-Exuding Skin Surface
[0180] A flowable gel formulation comprising nanoparticle powder,
ethanol and polyethylene glycol-400 was produced as follows:
[0181] An amount of pHEMA nanoparticle suspension as prepared
according to example 1 is mixed with an amount of pHPMA
nanoparticle suspension prepared according to Example 2 such that
the combined suspension represents 85% pHEMA and 15% pHPMA. The
combined suspension is lyophilized, and the resulting powder is
brushed through a 150 micron sieve and bagged for storage.
[0182] 1.15 g of the sieved nanoparticle powder is placed in a 100
ml beaker and a mixture of 1 g of PEG400, 3 g of ethanol and 0.10 g
of deionized water is poured into the beaker containing the powder.
This powder is mixed thoroughly with the liquid and initially forms
a paste. The paste transitions into a viscous gel within 30
seconds. The gel is placed into heat sealable dispensing tubes for
storage.
[0183] Upon application to intact skin, the alcohol evaporates
leaving behind a plasticized, dressing aggregate that conforms to
every irregular surface and adheres intimately to the underlying
skin.
[0184] It is to be understood that while the invention has been
described in conjunction with the above embodiments, that the
foregoing description and examples are intended to illustrate and
not limit the scope of the invention. Other aspects, advantages and
modifications within the scope of the invention will be apparent to
those skilled in the art to which the invention pertains.
* * * * *