U.S. patent application number 17/568790 was filed with the patent office on 2022-08-04 for variable-size hydrophobically-modified polymers.
The applicant listed for this patent is Medcura, Inc.. Invention is credited to Matthew DOWLING.
Application Number | 20220243039 17/568790 |
Document ID | / |
Family ID | 1000006289249 |
Filed Date | 2022-08-04 |
United States Patent
Application |
20220243039 |
Kind Code |
A1 |
DOWLING; Matthew |
August 4, 2022 |
VARIABLE-SIZE HYDROPHOBICALLY-MODIFIED POLYMERS
Abstract
In various aspects, the invention provides compositions of
variable-length hydrophobically-modified polymers. These
variable-length hydrophobes decorated along the hydrophilic polymer
backbone provide advanced properties and allow for precise control
over the behavior of the resulting amphiphilic polymer, including
in aqueous solution. Such control allows for enhanced functionality
of the amphiphilic polymer relative to standard single-length
hydrophobe grafting designs, including for hemostasis.
Inventors: |
DOWLING; Matthew;
(Riverdale, MD) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Medcura, Inc. |
Riverdale |
MD |
US |
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|
Family ID: |
1000006289249 |
Appl. No.: |
17/568790 |
Filed: |
January 5, 2022 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16603933 |
Oct 9, 2019 |
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PCT/US2018/027637 |
Apr 13, 2018 |
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17568790 |
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62484985 |
Apr 13, 2017 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61L 15/28 20130101;
A61L 24/08 20130101; C08L 71/00 20130101; A61L 15/26 20130101; C08L
5/08 20130101; C08B 37/003 20130101 |
International
Class: |
C08L 5/08 20060101
C08L005/08; A61L 15/26 20060101 A61L015/26; A61L 15/28 20060101
A61L015/28; C08L 71/00 20060101 C08L071/00; A61L 24/08 20060101
A61L024/08; C08B 37/08 20060101 C08B037/08 |
Claims
1. A hydrophobically-modified polymer or composition thereof,
wherein the modified polymer has hydrophobic groups of at least two
different sizes attached to the polymer backbone.
2. The polymer or composition of claim 1, wherein the modified
polymer is amphiphilic.
3. The polymer or composition of claim 2, wherein the polymer is
chitosan, alginate, or cellulosic biopolymer.
4. (canceled)
5. The polymer or composition of claim 3, wherein the polymer is
chitosan, and hydrophobic groups are incorporated by anhydride
chemistry.
6. The polymer or composition of claim 1, wherein the polymer has
from about 10% to about 50% of functional groups occupied by a
hydrophobic group.
7. The polymer or composition of claim 6, wherein the modified
polymer has about 5 to about 100 moles of hydrophobic group per
mole of polymer.
8. The polymer or composition of claim 7, wherein the molecular
weight of the polymer is from about 40,000 to about 500,000
Daltons.
9. The polymer or composition of claim 1, having from 2 to about 10
different hydrophobic groups.
10. The polymer or composition of claim 9, wherein the hydrophobic
groups are independently selected from linear, branched, or cyclic
hydrocarbon groups.
11. The polymer or composition of claim 10, wherein the hydrophobic
groups include at least one saturated hydrocarbon, which is
optionally a conjugated fatty acid.
12. (canceled)
13. (canceled)
14. The polymer or composition of claim 1, wherein the hydrophobic
groups each have from 1 to about 28 carbon atoms, or from 1 to 18
carbon atoms.
15. The polymer or composition of claim 9, having at least one or
two of: (a) a C1 to C5 hydrocarbon group, which may be substituted;
(b) a C6 to C12 hydrocarbon group, which may be substituted; (c) a
C13 to C28 hydrocarbon group, which may be substituted; (d) a
hydrophobic group having a size greater than C28.
16. The polymer or composition of claim 15, wherein the hydrophobic
groups comprise a C1 to C4 hydrocarbon and a hydrocarbon greater
than C6.
17. (canceled)
18. The polymer or composition of claim 16 or 17, comprising a
hydrocarbon group of from C6 to C12 and a hydrocarbon group of from
C16 or C18.
19. The polymer composition of claim 15, wherein the hydrophobic
groups comprise a C6 to C12 hydrocarbon and a C16 to C28
hydrocarbon.
20. (canceled)
21. (canceled)
22. The polymer or composition of claim 15, wherein the hydrophobic
groups comprise a C1 to C4 hydrocarbon, a C6 to C12 hydrocarbon,
and a C16 to C28 hydrocarbon.
23. The polymer or composition of claim 1, formulated as a solid,
liquid, gel, foam, or putty.
24-28. (canceled)
29. The polymer or composition of claim 23, wherein the modified
polymer is present at 0.1 to about 5% by weight.
30-36. (canceled)
37. A method for treating a wound, comprising, applying the polymer
or composition of claim 1 to a bleeding wound.
38-46. (canceled)
Description
PRIORITY
[0001] This application claims the benefit of U.S. Provisional
Application No. 62/484,985, filed Apr. 13, 2017, the contents of
which are hereby incorporated by reference in its entirety.
BACKGROUND
[0002] A vast array of hydrophobically-modified (hm) polymers has
been created for various uses, such as: paints, industrial
thickeners, drug delivery matrices, and hemostasis. The
associations between the hydrophobic groups in water allow the
polymers to self-assemble into 3-dimensional networks. These
associations tend to thicken the resulting aqueous solutions
created by these biopolymers.
[0003] However, hydrophobically-modified (hm) polymers generally
have one length of hydrophobic grafts to the backbone of the
polymer. Properties of polymers having variable graft structures,
sizes, and densities have not been investigated.
SUMMARY OF THE INVENTION
[0004] In various aspects, the invention provides compositions of
variable-length hydrophobically-modified polymers. These
variable-length hydrophobes decorated along the hydrophilic polymer
backbone provide advanced properties and allow for precise control
over the behavior of the resulting amphiphilic polymer, including
in aqueous solution. Such control allows for enhanced functionality
of the amphiphilic polymer relative to standard single-length
hydrophobe grafting designs.
[0005] In various embodiments, the invention provides a hm polymer
or composition thereof, wherein the modified polymer has
hydrophobic groups of at least two different sizes attached to the
polymer backbone. These variable-length hm polymers are a new class
of associating polymers, including for uses in water-treatment,
cosmetics and personal care compositions, drug delivery, wound
care, hemostasis, industrial paints/coatings, and other uses.
[0006] In some embodiments, the polymer or composition is a
modified polymer that is amphiphilic. In some embodiments, the
polymer is based on a polysaccharide backbone, such as chitosan,
alginate, cellulosics, pectins, gellan gums, xanthan gums,
dextrans, and hyaluronic acids, among others. In some embodiments,
the polymer is a synthetic (i.e., non-natural) polymer, such as
polyethylene glycol, poly-lactic acid, poly-glycolic acid, poly
lactic co-glycolic acid, poly .epsilon.-caprolactone, polyurethane,
polymethylmethacrylate, and silicone, among others. In some
embodiments, the polymer is chitosan.
[0007] The polymer may have from 2 to about 10 different
hydrophobic groups, and optionally from 2 to about 5 different
hydrophobic groups (e.g., 2, 3, or 4 different hydrophobic groups).
The hydrophobic groups may be independently selected from linear,
branched, or cyclic hydrocarbon groups. For example, the
hydrophobic groups may include at least one saturated hydrocarbon,
which is optionally an acyl group (e.g., fatty aldehyde or fatty
acid anhydride).
[0008] In some embodiments, the polymer has at least one or at
least two of:
[0009] (a) a C1 to C5 hydrocarbon group, which is optionally
substituted by non-hydrocarbon moieties;
[0010] (b) a C6 to C12 hydrocarbon group, which is optionally
substituted with non-hydrocarbon moieties;
[0011] (c) a C13 to C28 hydrocarbon group, which is optionally
substituted with non-hydrocarbon moieties;
[0012] (d) a hydrophobic group having a size greater than C28,
which is optionally substituted with non-hydrocarbon moieties.
Non-hydrocarbon moieties include heteroatoms or groups comprising
heteroatoms such as O, N, S, or halogen.
[0013] The polymer composition may be formulated as a solid,
liquid, gel, foam, or putty. For example, the polymer may be a
solid, which may be lyophilized or may be a dehydrated solution or
dehydrated foam. In some embodiments, the polymer is formulated
with one or more solvents. The solvents may comprise water. In some
embodiments, the solvent comprises an industrial solvent, which may
be an organic solvent. In some embodiments, the solvent is paint or
industrial coating.
[0014] In some embodiments, the modified polymer is present at 0.1
to about 5% by weight in the composition, or in some embodiments,
from 0.5 to 2.0% (e.g., about 0.5%, about 1.0%, 1.5%, or about 2%).
In some embodiments, the polymer is formulated with at least one
synthetic polymer. Exemplary synthetic polymers include polythene,
polystyrene, polyacrylate, polyamide, polyester, polyurethane,
polysulfide, and polycarbonate. In some embodiments, the synthetic
polymer is polyvinyl alcohol.
[0015] The modified polymer may provide anti-bacterial and/or
anti-fungal properties, which is desirable for many types of
garments and fabrics, as well as cosmetic and personal care
composition.
[0016] In some embodiments, the composition is a hemostatic device
or dressing for bleeding control. There are a myriad of material
characteristics that are desired for a well-functioning hemostatic
material. For example, the material should be easy to apply
(ideally flowable to conform to surfaces, cavities, and/or small
areas), able to create a rapid seal when in contact with bleeding
tissue, retain its mechanical integrity in the face of high
pressure bloodflow, be easy to remove, and be safely bioresorbable
if left inside the body after use. The present application provides
a framework to create specific hydrophobic designs that employ
multiple different grafting lengths and density of hydrophobic
groups to achieve optimized properties in flowability, tissue
adhesion, cohesion, biodegradation, and removability.
[0017] In some embodiments, the modified polymer (e.g., chitosan or
other polymer disclosed herein) has both C8 and C18 acyl groups
covalently attached to the backbone of the biopolymer, which is
both adhesive to tissues, due to the C8 groups, and also cohesive
under exudate flow, due the C18 groups. The C8 groups are fluid at
room and body temperature, allowing the polymer to spread onto the
cell surfaces more effectively, whereas the C18's on neighboring
polymer chains hold the polymer molecules together strongly even in
the presence of high exudate or blood flow. These embodiments can
thus balance adhesive and cohesive properties.
[0018] Alternatively, or in addition, incorporation of small
hydrophobic groups, such as C1 to C4 acyl chains, allows the
chitosan to degrade more predictably from lysozyme activity in the
body. This is very important for creating a material which can be
left inside the body after treatment of the wound. More
specifically, hydrophobic groups below the length of C6 do not
contribute towards improved hemostatic effect. However, hydrophobic
modification in the range of C1 to C6 allow for a framework to
optimize the degradation of the material inside the body via
lysozymes. Particularly in the case of surgical-use hemostats, it
is ideal for the hemostatic biomaterial to degrade quickly after
achieving hemostasis.
[0019] In some aspects, the invention provides a method for
treating a wound, comprising, applying the polymer or composition
with hemostatic properties to a bleeding wound. In some
embodiments, the wound has high exudate or blood flow. In some
embodiments, the polymer composition provides advantages in tissue
adhesion as well as material cohesion (for creating a barrier even
with high blood flow). In some embodiments, the material degrades
in the body within two months, within one month, within two weeks,
or within one week, or with about 2 days. In some embodiments, the
material is mechanically removable from the wound without damaging
the underlying tissue. In various embodiments, the modified polymer
(in the amount employed) is soluble in aqueous environment.
[0020] A hydrophobically-modified (hm) biopolymer material for
incorporation into aqueous or organic solutions or suspensions can
be based on a solution of the hm-biopolymer that is about 0.1% to
about 5.0% by weight relative to the total weight of the
composition, or in some embodiments, about 0.5% to about 4%, or
about 0.5% to about 3% of the total weight of the composition, or
about 0.5% to about 2% of the total weight of the composition.
[0021] Hydrophobic moieties can be independently selected from
saturated hydrocarbons (e.g., alkanes) and unsaturated hydrocarbons
(e.g., alkenes, alkynes), which may be linear, branched or cyclic.
In some embodiments, the hydrophobic moieties include aromatic
hydrocarbons. In some embodiments, the hydrophobic moieties are
fatty acids conjugated to polymer functional groups, including
amines or hydroxyl groups. An exemplary conjugation chemistry is a
fatty acid anhydride.
[0022] Other aspects and embodiments of the invention will be
apparent from the following detailed description.
DESCRIPTION OF THE FIGURES
[0023] FIG. 1 illustrates variable-sized hydrophobically-modified
(hm) chitosans, including from the top: native chitosan (zero-order
(0th Order) hm-chitosan), chitosan having C8 hydrophobes at a
grafting density of 5 mol % of available amines along the backbone
(a first-order (1st Order) hm-chitosan), and second-order (2nd
Order), third-order (3rd Order) and fourth-order (4th Order)
hm-chitosans, meaning that two, three and four types of hydrophobic
species, of differing sizes and structures, are found along the
backbone of the polymer.
[0024] FIG. 2 illustrates variable-sized hydrophobically-modified
polymers applied to differently sized polymer backbones.
[0025] FIG. 3 shows the effect of variable length grafted vs single
length grafted hm-chitosan on heparinized bovine blood. (Left) 5
mol % C6, 5 mol % C10 variable length hydrophobically modified
chitosan (gel). (Right) 10 mol % C8 single length hydrophobically
modified chitosan (flowable). Both polymers have same hydrophobic
density, but significantly different gelation properties,
highlighting the importance of hydrophobic grafting design with
respect to hemostatic or wound treatment functionality.
[0026] FIG. 4 shows blood gelation experiments. A 1.0 mL sample of
each hm-chitosan solution (2 wt %) was mixed with 0.5 mL of each
blood fraction and vortexed thoroughly. Modified polymer
compositions include 5 mol % C12, 1 mol % C18, 1.5 wt %; 5 mol %
C12, 1 mol % C18, 1.0 wt %; and 5 mol % C12, 1.0 wt %.
[0027] FIG. 5 shows the results of blood gelling capability of
various hydrophobic grafting designs along chitosan backbone. All
hydrophobic design grafts are attached to a medium molecular weight
chitosan (Primex hqg 400). Solutions of hm-chitosans were 1.5 wt %
of polymer dissolved in 0.2 M acetic acid in water. Several 2nd,
3rd and 4th order grafting designs are described via % mol of
amines along the chitosan backbone. Gelling is defined as an
ability for a mixture of polymer and blood (citrated bovine blood
(Lampire)) as a ratio of 2:1 (v/v) to hold its own weight upon vial
inversion.
[0028] FIG. 6 shows blood gelation experiments with 5 different
hm-chitosan constructs at different wt % (0.5 and 1.0 wt %) and at
different ratios with blood. Samples 4 and 5, incorporating C12 and
C18 hydrophobic grafts, showed the strongest gelation
properties.
[0029] FIG. 7 shows an evaluation of steady shear rheology of
hm-chitosan foams. The addition of blood to hm-chitosan (triangles)
greatly increases the viscosity over the foam itself (circles).
This is apparent for unmodified chitosan as well. The saline foam
was also mixed with blood as a control.
[0030] FIG. 8 shows an evaluation of steady shear rheology of
hm-chitosan foams, including foams based on low and high molecular
weight chitosans.
[0031] FIG. 9 shows a logarithmic plot of initial degradation rates
of chicken egg white lysozyme on hm-chitosans (chitosan backbone is
medium molecular weight (Primex hgq 400)). Samples A through G are
distinct hydrophobic grafting designs along the chitosan backbone.
Samples E, F and G initially degrade much faster due to the
presence of large amounts of C1 included in the hydrophobic
grafting design.
DETAILED DESCRIPTION OF THE INVENTION
[0032] In various aspects, the invention provides compositions of
variable-length hydrophobically-modified polymers for use in
applications such as wound treatment, drug delivery, cosmetics,
textiles, and others. Known hydrophobically-modified polymers
generally have one length of hydrophobic grafts to the backbone of
the polymer, albeit at various grafting densities. In accordance
with embodiments of the present invention, variable-length
hydrophobes decorated along the hydrophilic polymer backbone allow
for precise control over the behavior of the resulting amphiphilic
polymer. Such control allows for enhanced functionality of the
amphiphilic polymer relative to standard single-length hydrophobe
grafting designs. The enhanced functionalities can result from
novel three dimensional structures created by these polymers.
[0033] In various embodiments, the invention provides a
hydrophobically-modified polymer or composition thereof, wherein
the modified polymer has hydrophobic groups of at least two
different sizes attached to the polymer backbone. These
variable-length hydrophobically-modified polymers are a new class
of associating polymers. These polymers provide a greater level of
control over how these polymers interact with themselves and with
other entities in an aqueous or organic environment. This results
in a new regime of functionality which may have uses in
water-treatment, cosmetics and personal care compositions, drug
delivery, wound care, hemostasis, industrial paints/coatings, and
other uses.
[0034] In some embodiments, the polymer or composition is a
modified polymer that is amphiphilic. In some embodiments, the
polymer is based on a polysaccharide backbone, such as chitosan,
alginate, cellulosics, pectins, gellan gums, xanthan gums,
dextrans, and hyaluronic acids, among others. In some embodiments,
the polymer is a synthetic (i.e., non-natural) polymer, such as
polyethylene glycol, poly-lactic acid, poly-glycolic acid, poly
lactic co-glycolic acid, poly lactic co-glycolic acid,
polymethylmethacrylate, poly .epsilon.-caprolactone, polyurethane,
silicone, among others.
[0035] In some embodiments, the polymer is chitosan having a level
of deacetylation of from about 40 to about 90%, or from about 50 to
about 80%, with from about 10% to about 50% of functional groups
occupied by a hydrophobic group. As used herein, the term "mol %"
of a hydrophobic group refers to the % of available amines occupied
by a hydrophobic group, assuming a level of deacetylation (e.g., in
the case of chitosan) of 85%. For example, the modified polymer may
have about 5 to about 100 moles of hydrophobic group per mole of
polymer. The molecular weight of the polymer is from about 40,000
to about 500,000 Daltons.
[0036] The polymer may have from 2 to about 10 different
hydrophobic groups, and optionally from 2 to about 5 different
hydrophobic groups (e.g., 2, 3, or 4 different hydrophobic groups).
The hydrophobic groups may be independently selected from linear,
branched, or cyclic hydrocarbon groups. For example, the
hydrophobic groups may include at least one saturated hydrocarbon,
which is optionally an acyl group. In some embodiments, the
hydrophobic groups include at least one unsaturated, aromatic, or
polyaromatic hydrocarbon.
[0037] In various embodiments, the hydrophobic groups each have
from 1 to about 100 carbon atoms, or from 1 to about 50 carbon
atoms. In some embodiments, the hydrophobic groups each have from 1
to about 28 carbon atoms. In some embodiments, the polymer (e.g.,
chitosan) has at least one or at least two of:
[0038] (a) a C1 to C5 hydrocarbon group, which is optionally
substituted by non-hydrocarbon moieties;
[0039] (b) a C6 to C12 hydrocarbon group, which is optionally
substituted with non-hydrocarbon moieties;
[0040] (c) a C13 to C28 hydrocarbon group, which is optionally
substituted with non-hydrocarbon moieties;
[0041] (d) a hydrophobic group having a size greater than C28,
which is optionally substituted with non-hydrocarbon moieties.
Non-hydrocarbon moieties include heteroatoms or groups comprising
heteroatoms such as O, N, S, or halogen.
[0042] In some embodiments, the hydrophobic groups comprise C8
hydrocarbon groups, which are present along with at least one of
C14, C16, or C18 hydrocarbon groups at a ratio of from 5:1 to 20:1,
such as from 5:1 to 15:1, or about 10:1 in some embodiments (C8 to
C14/C16/C18).
[0043] In some embodiments, the hydrophobic groups comprise C10 or
C12 hydrocarbon groups, which are present along with at least one
of C14, C16, or C18 hydrocarbon groups at a ratio of from 2:1 to
10:1, such as from 2:1 to 8:1, or about 5:1 in some embodiments
(C10/C12 to C14/C16/C18).
[0044] In some embodiments, the hydrophobic groups comprise a C1 to
C4 hydrocarbon and a C6 to C12 hydrocarbon. In some embodiments,
the hydrophobic groups comprise a C6 to C12 hydrocarbon and a C16
to C28 hydrocarbon. In some embodiments, the hydrophobic groups
comprise a C1 to C4 hydrocarbon, a C6 to C12 hydrocarbon, and a C16
to C28 hydrocarbon.
[0045] In some embodiments, the C1 to C4 hydrocarbon groups (e.g.,
C1) is present at 5:1 to 25:1 with respect to other larger
hydrophobic grafts (e.g., C6 or greater). In some embodiments, C1
to C4 hydrocarbon groups are present at from about 5:1 to about
20:1, or about 5:1 to about 15:1, or about 5:1 to about 10:1 with
regard to larger hydrophobic grafts (C6 or greater). In some
embodiments, C1 to C4 hydrocarbon groups (e.g., C1) is incorporated
into the polymer along with C6 to C12 (e.g., C8 or C10 or C12), and
C13 to C28 hydrocarbon groups (e.g., C16 or C18).
[0046] The polymer composition may be formulated as a solid,
liquid, gel, foam, or putty. For example, the polymer may be a
solid, which may be lyophilized or may be a dehydrated solution or
dehydrated foam. Thus, the polymer may form a solid matrix. In some
embodiments, the polymer is formulated with one or more solvents.
The solvents may comprise water. In some embodiments, the solvent
comprises an industrial solvent, which may be an organic solvent.
In some embodiments, the solvent is paint or industrial
coating.
[0047] In some embodiments, the modified polymer is present at 0.1
to about 5% by weight in the composition, or in some embodiments,
from 0.5 to 2.0% (e.g., about 0.5%, about 1.0%, 1.5%, or about 2%).
In some embodiments, the polymer is formulated with at least one
synthetic polymer. Exemplary synthetic polymers include polythene,
polystyrene, polyacrylate, polyamide, polyester, polyurethane,
polysulfide, and polycarbonate. In some embodiments, the synthetic
polymer is polyvinyl alcohol.
[0048] The modified polymer may provide anti-bacterial and/or
anti-fungal properties, which provide unique advantages. For
example, the composition may be a fiber or textile as described in
PCT/US2017/56887, which is hereby incorporated by reference in its
entirety. For example, antimicrobial properties are desirable for
many types of garments and fabrics. In some embodiments, the
composition is a cosmetic, personal care composition, or drug
delivery matrix, as described in WO 2017/177027, which is hereby
incorporated by reference in its entirety.
[0049] In some embodiments, the composition is paint, industrial
coating, or industrial thickener. In such embodiments, the polymer
provides unique physical properties to the composition which can
provide for improved functionality.
[0050] In some embodiments, the composition is a hemostatic device
or dressing for bleeding control. There are a myriad of material
characteristics that are desired for a well-functioning hemostatic
material, including: (1) the material should be easy to apply
(ideally flowable to conform to surfaces, cavities, and/or small
areas), (2) able to create a rapid seal when in contact with
bleeding tissue, (3) retain its mechanical integrity in the face of
high pressure bloodflow, (4) be easy to remove, and (5) be safely
bioresorbable if left inside the body after use. Traditionally,
these attributes are evaluated by mixing a number of different
components together (e.g. polymer, nanoparticles, and proteins),
due to the assumption that a single material cannot provide all
critical characteristics. While a single material that provides
tenability in each of these categories would be ideal, such a
material is difficult to design, because often chemistries which
result in a favorable attribute in one area (e.g. adhesion), result
in the detuning of attributes in another area (e.g. cohesion).
Here, we describe a framework, utilizing the available chemistry
along the chitosan backbone via free amine groups (for example) to
create specific hydrophobic designs that employ multiple different
grafting lengths and density of hydrophobic groups to achieve
optimized properties in flowability, tissue adhesion, cohesion,
biodegradation, and removability.
[0051] In some embodiments, the modified polymer (e.g., chitosan or
other polymer disclosed herein) has both C8 and C18 acyl groups
covalently attached to the backbone of the biopolymer, which is
both adhesive to tissues, due to the C8 groups, and also cohesive
under exudate flow, due the C18 groups. The C8 groups are fluid at
room and body temperature, allowing the polymer to spread onto the
cell surfaces more effectively, whereas the C18's on neighboring
polymer chains hold the polymer molecules together strongly even in
the presence of high exudate or blood flow. These embodiments can
thus balance adhesive and cohesive properties. Traditional chitosan
dressings fail due to either lack of adherence to the wound site or
lack of coherence once an initial seal has been achieved. More
specifically, native chitosan is particularly good at adhering to
wet, bleeding tissue. However, chitosan generally has a limited
ability to hold together under high-pressure blood flow.
[0052] In accordance with embodiments of the invention, certain
hydrophobes provide advantages for optimizing adherence (e.g., to
the tissue or wound site), and other hydrophobes are more
advantageous for improving coherence (e.g., coherence of the
artificial clot). As used herein, the term "artificial clot" refers
to physical networks of hydrophobically-modified polymers, blood
cells, and surrounding tissue cells which effectively act as a
solid barrier to prevent further blood loss. In the range of C6-C12
lengths, the hydrophobic grafts are useful in improving adhesion of
the dressings. In the range of C13-C22 lengths, the hydrophobic
grafts are useful in improving the cohesion of the dressings. By
mixing hydrophobic grafts, for example, C12 and C18 attached to a
composition has improved characteristics as compared to native
chitosan, 5% C12 chitosan only, or 1% C18 chitosan only. In some
embodiments, the polymer has from 1 mol % to 20 mol % C12
hydrophobic groups, or from 2 mol % to about 10 mol % C12
hydrophobic groups, or about 5 mol % C12 hydrophobic groups. In
some embodiments, the polymer has from 0.5 mol % to 5 mol % C18
hydrophobic groups, such as from 0.5 mol % to 2 mol % (e.g., about
1 mol %) C18 hydrophobic groups. These may be present for example
on medium molecular weight chitosan (MW-250 kDa).
[0053] For example, in some embodiments, the hemostat composition
is a syringeable gel. The C12 component allows for robust
attachment of the gel to the mucosal surface, whereas the C18
component allows for cohesive matrix properties as the blood begins
to infiltrate the gel.
[0054] In some embodiments, the hemostat composition is a
lyophilized sponge. The dressing not only adheres strongly to the
bleeding tissue (relative to native chitosan), but also holds
together in the presence of significant blood pressure. While a
single-length 5 mol % C12 adheres significantly more than native
chitosan to wet tissue, it fails upon application of blood
pressures much greater than 100 mmHg. Particularly during
resuscitation after trauma, there can be a significant risk of
re-bleeding at resuscitation pressures.
[0055] In some embodiments, the hemostat composition is a clear
film. The film not only adheres strongly to the bleeding tissue
(relative to native chitosan), but also holds together in the
presence of significant blood pressure. While a single-length 5 mol
% C12 adheres significantly more than native chitosan to wet
tissue, it fails upon application of blood pressures much greater
than 30 mmHg. An ability to stand up to such pressures creates an
issue in most clinical bleeding scenarios.
[0056] In some embodiments, the hemostat composition is a powder.
The powder not only adheres strongly to bleeding tissue (relative
to native chitosan), but also holds together in the presence of
significant blood pressure. While a single-length 5 mol % C12
powder adheres significantly more than native chitosan to wet
tissue, it fails upon application of blood pressures much greater
than 100 mmHg. Again, during resuscitation after trauma, there can
be a significant risk of re-bleeding at resuscitation
pressures.
[0057] In some embodiments, the hemostat composition is a foam,
including a sprayable foam created by mixing the hm-chitosan
solution with liquefied gas under pressure in a canister. Upon
opening the canister valve to atmospheric pressure, the gas causes
rapidly expulsion of the hm-chitosan from the canister. The C12
component of the formulation allows for large expansion of the foam
relative to the initial gel volume, whereas the C18 component
allows for a mechanically integral final foam product. The foam
described herein may also be a syringeable foam, where a
double-barrel syringe system connected to a mixing tip is utilized.
Gas is released upon mixing the material in one barrel, hm-chitosan
dissolved in dilute acetic acid in water, with the material in the
other barrel, a neutrally or negatively charged polymer dissolved
in water containing a low concentration of sodium bicarbonate. Upon
mixing with the acetic acid, the bicarbonate released carbon
dioxide gas, causing the foaming and expansion of the hm-chitosan.
These and related embodiments are disclosed in PCT/US2018/025742,
which is hereby incorporated by reference in its entirety.
[0058] In some embodiments, the hemostat composition is a moldable
putty. Hydrophobically-modified chitosan in the form of a moldable
putty composition is described in U.S. Pat. No. 9,616,088, which is
hereby incorporated by reference in its entirety. For example, the
gel at 1.0 wt % (in aqueous 0.15 M lactic acid) is thick, but has
an ability to mix with polyvinyl alcohol and sodium tetraborate to
create a putty-like mechanical characteristic. The C12 component of
the formulation allows for robust attachment of the putty to the
mucosal surface, whereas the C18 component allows for cohesive
matrix properties as the blood begins to infiltrate the putty.
[0059] Alternatively, or in addition, incorporation of small
hydrophobic groups, such as C1 to C4 acyl chains, allows the
chitosan to degrade more predictably from lysozyme activity in the
body. This is very important for creating a material which can be
left inside the body after treatment of the wound. More
specifically, hydrophobic groups below the length of C6 do not
contribute towards improved hemostatic effect. However, hydrophobic
modification in the range of C1 to C6 allow for a framework to
optimize the degradation of the material inside the body via
lysozymes. Particularly in the case of surgical-use hemostats, it
is ideal for the hemostatic biomaterial to degrade quickly after
achieving hemostasis. For example, 5 mol % C12 and 30 mol % C1
attached to a medium molecular weight chitosan (MW-250 kDa) creates
a composition having improved biodegradation characteristics
relative to either native chitosan, 5 mol % C12 chitosan only, or
30 mol % C1 chitosan only. Other variations, including with C6 to
C12 (e.g., C8 or C10 or C12) and C13 to C28 (e.g., C16 or C18)
hydrocarbon groups are described herein. In some embodiments, C1 to
C4 acyl chains are incorporated at from 10 mol % to 80 mol %, such
as from 10 mol % to 60 mol %. In some embodiments, the C1 to C4
acyl chains are incorporated at 20 mol % to 60 mol %, or from 20
mol % to 50 mol %, or from 20 mol % to 40 mol %.
[0060] In some aspects, the invention provides a method for
treating a wound, comprising, applying the polymer or composition
with hemostatic properties to a bleeding wound. In some
embodiments, the wound has high exudate or blood flow. In some
embodiments, the polymer composition provides advantages in tissue
adhesion as well as material cohesion (for creating a barrier even
with high blood flow). In some embodiments, the material degrades
in the body within about two months, within about one month, or
within about two weeks, or within about one week, or with about two
days. In some embodiments, the material is mechanically removable
from the wound without damaging the underlying tissue. In various
embodiments, the modified polymer (in the amount employed) is
soluble in aqueous environment.
[0061] In some embodiments, the composition has antimicrobial
properties. While the mechanism of action of chitosan as an
anti-microbial is a not well understood, two key contributing
mechanisms likely play a role: (1) penetration into the bacterial
cells and intercalation with plasmid DNA, thus preventing
replication, and (2) physical immobilization of cells due to
physical binding of bacteria into a robust cohesive network.
Smaller hydrophobes (e.g., C1-C12) assist with interfacing with the
cell membrane and/or cell wall, and larger hydrophobes (e.g.,
C13-C22) may assist with physical binding of the bacteria into
immobilized networks. Hence, the variable-length design framework,
along a wide span of polymer (e.g., chitosan) backbone lengths,
allows for the creation of many unique molecules which can amplify
a given mechanism towards bacterial death depending upon the
clinical circumstances. Certain bacteria are more susceptible to
penetration through the cell well (typically gram negative);
infections caused robust bacteria may be limited to treatment via
molecules that work only by physical bacteriostasis (e.g.
multi-drug resistant bacteria).
[0062] In some embodiments, and as illustrated in FIG. 1, the
polymer composition is a second-order (2nd Order), third-order (3rd
Order) or fourth-order (4th Order) hm-polymer, such as a
hm-chitosan. Further, and as shown in FIG. 2, the 2nd Order, 3rd
Order, or 4th Order biopolymer can be based on a low molecular
weight polymer (e.g., 50-200 kDa), a medium molecular weight
biopolymer (200-400 kDa), or high molecular weight polymer (400 to
1,500 kDa).
[0063] An exemplary hm-polymer material is hm-chitosan. Chitosan is
the common name of the linear, random copolymer that consists of
.beta.-(1-4)-linked D-glucosamine and N-acetyl-D-glucosamine. The
molecular structure of chitosan consists of a linear backbone
linked with glycosidic bonds. Chitosan is the major component of
crustacean shells such as crab, shrimp, krill and crawfish shells.
Additionally, chitosan is the second most abundant natural
biopolymer after cellulose. Commercial chitosan samples are
typically prepared by chemical de-N-acetylation of chitin under
alkaline conditions. Depending on the source of the natural chitin
(extracted from shells) and its production process, chitosan can
differ in size (average molecular weight Mw) and degree of
N-acetylation (% DA). While the poor solubility of chitosan in
water and in common organic solvents restricts its applications,
reactive amino groups in the chitosan backbone make it possible to
chemically conjugate chitosan with various molecules and to
modulate its properties for use in textiles.
[0064] The degree of deacetylation of chitin may range from about
40-100%, or in some embodiments, from 60 to 100%, which determines
the charge density. The structure of chitosan (deacetylated), and
is depicted in Formula 1:
##STR00001##
[0065] These repeating monomeric units include a free amino group,
which makes molecules or compounds containing chitosan or its
derivatives readily reactive. The hydrophobic modification of the
chitosan backbone is through the association of an amphiphilic
compound with the amino group, such that the hydrophobic tail of
the amphiphilic compound is bound with the hydrophilic backbone
structure.
[0066] In some embodiments, the polymer is one or more
hm-polysaccharides, including but not limited to cellulosics,
chitosans, alginates, pectins, gellan gums, xanthan gums, dextrans,
and hyaluronic acids, all of which are abundant, natural
biopolymers. In some embodiments, the hm-biopolymer contains
cationic groups. hm-chitosan, for example, is a stable, robust, and
durable biopolymer which is capable of retaining its functionality
for extremely long storage periods at room temperature. The natural
origin of these polysaccharides varies; cellulosics are found in
plants, whereas chitosans and alginates are found in the
exoskeleton or outer membrane of a variety of living organisms. In
some embodiments, the hm-chitosan is derived from a deacteylated
chitin, which may be derived from one or more of crab, shrimp,
krill, and crawfish.
[0067] The form of the natural polymers used may vary to include
standard states, derivatives and other various formulations. For
example, the hm-cellulosics may be formed from, without limitation,
hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose,
hydroxypropyl methyl cellulose, and/or hydroethyl methyl cellulose.
Hm-chitosans may be prepared from, without limitation, the
following chitosan salts: chitosan lactate, chitosan salicylate,
chitosan pyrrolidone carboxylate, chitosan itaconate, chitosan
niacinate, chitosan formate, chitosan acetate, chitosan gallate,
chitosan glutamate, chitosan maleate, chitosan aspartate, chitosan
glycolate and quaternary amine substituted chitosan and salts
thereof. Hm-alginates may be prepared from, without limitation,
sodium alginate, potassium alginate, magnesium alginate, calcium
alginate, and/or aluminum alginate. It is to be understood that
various other forms of any of these natural polysaccharides that
provide the proper functional capabilities may be employed without
departing from the scope and spirit of the present invention.
[0068] In some embodiments, the polymeric component is a mixture of
polysaccharides. For instance, the mixture may be of various
different sub-classes of a single polymer class. Alternatively, the
mixture may include two or more different classes of polymer, for
instance a cellolusic and a chitosan, an alginate and a chitosan,
and an alginate and a cellulosic.
[0069] In various embodiments, the biopolymer is a hm-chitosan,
which may be prepared from a chitosan having a degree of
deacetylation of from about 40% to about 90%, such as from about
50% to about 80%, such as from about 60% to about 75%. In some
embodiments, the degree of substitution of the hydrophobic
substituent on the biopolymer (e.g., chitosan) is from about 1 to
about 100 moles of the hydrophobic substituent per mole of the
biopolymer. In some embodiments, the degree of substitution of the
hydrophobic substituent on the polysaccharide is from about 20 to
about 100 moles of the substituent per mole of the biopolymer, or
from about 40 to about 100 moles of the substituent per mole of the
biopolymer, or from about 40 to about 65 moles of the hydrophobic
substituent per mole of the biopolymer. In some embodiments, the
degree of substitution of the hydrophobic substituent on the
biopolymer is from about 1 to about 30 moles of the hydrophobic
substituent per mole of the biopolymer (e.g., chitosan). In some
embodiments, the molecular weight of the polymer is from about
25,000 to about 1,500,000 grams per mole. In various embodiments,
the molecular weight of the biopolymer ranges from about 40,000 to
about 500,000 grams per more, or from about 50,000 to about 250,000
grams per mole, or from about 50,000 to about 100,000 grams per
mole. As used herein, the term "molecular weight" means weight
average molecular weight. Methods for determining average molecular
weight of bio-polymers include low angle laser light scattering
(LLS) and Size Exclusion Chromatography (SEC). In performing low
angle LLS, a dilute solution of the polysaccharide, typically 2% or
less, is placed in the path of a monochromatic laser. Light
scattered from the sample hits the detector, which is positioned at
a low angle relative to the laser source. Fluctuation in scattered
light over time is correlated with the average molecular weight of
the polysaccharide in solution. In performing SEC measurements,
again a dilute solution of biopolymer, typically 2% or less, is
injected into a packed column. The polysaccharide is separated
based on the size of the dissolved polymer molecules and compared
with a series of standards to derive the molecular weight.
[0070] A hydrophobically-modified biopolymer material for
incorporation into aqueous or organic solutions or suspensions can
be based on a solution of the hm-biopolymer that is about 0.1% to
about 5.0% by weight relative to the total weight of the
composition, or in some embodiments, about 0.5% to about 4%, or
about 0.5% to about 3% of the total weight of the composition, or
about 0.5% to about 2% of the total weight of the composition. In
some embodiments, the biopolymer is about 1.0% to about 5.0% by
weight relative to the total weight of the composition of the
biopolymer, or in some embodiments, about 1.5% to about 5%, or
about 2.0% to about 4% of the total weight of the composition. In
some embodiments, the hm-biopolymer solution is dried or
lyophilized.
[0071] Hydrophobic moieties can be independently selected from
saturated hydrocarbons (e.g., alkanes) and unsaturated hydrocarbons
(e.g., alkenes, alkynes), which may be linear, branched or cyclic.
In some embodiments, the hydrophobic moieties include aromatic
hydrocarbons. In some embodiments, the hydrophobic moieties are
selected from hydrocarbons having from 1 to about 100 carbon atoms,
or from about 1 to about 60 carbon atoms, or from about 1 to about
28 carbon atoms, or from about 1 to about 18 carbon atoms.
[0072] The hydrophobic substituents may comprise at least one
hydrocarbon group having from about 8 to about 18 carbon atoms
attached to the backbone of the one biopolymer, and in some
embodiments the C8 to C18 group is an alkyl group. In some
embodiments, the hydrocarbon group comprises an arylalkyl group. As
used herein, the term "arylalkyl group" means a group containing
both aromatic and aliphatic structures.
[0073] The modified biopolymer comprises a biopolymer backbone
(such as chitosan) that includes a hydrophilically reactive
functional group (e.g., amino groups) that binds with the
hydrophilically reactive head groups (e.g., carbonyl functional
group) of an amphiphilic compound (e.g., aldehyde), to form the
hm-chitosan or other hm-polymer. The head group is further
associated with a hydrophobic tail group. In the current
embodiment, the hydrophobic tail may be, for example, a
hydrocarbon. Thus, a hydrophobic tail is associated with the
biopolymer backbone providing the hydrophobic modification to the
molecule that extends from the backbone and may interact with a
surrounding environment in numerous ways, such as through
hydrophobic interaction with materials.
[0074] Examples of procedures for modifying polymers are as
follows.
[0075] Alginates can be hydrophobically modified by exchanging
their positively charged counterions (e.g. Na+) with tertiary-butyl
ammonium (TBA) ions using a sulfonated ion exchange resin. The
resulting TBA-alginate is dissolved in dimethylsulfoxide (DMSO)
where reaction occurs between alkyl (or aryl) bromides and the
carboxylate groups along the alginate backbone. Alginate can also
be modified by fatty amine groups (e.g. dodecyl amine), followed by
addition of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, via EDC
coupling.
[0076] Cellulosics can be hydrophobically modified by first
treating the cellulosic material with a large excess highly basic
aqueous solution (e.g. 20 wt % sodium hydroxide in water). The
alkali cellulose is then removed from solution and vigorously mixed
with an emulsifying solution (for example, oleic acid) containing
the reactant, which is an alkyl (or aryl) halide (e.g. dodecyl
bromide).
[0077] Chitosans can be hydrophobically modified by reaction of
alkyl (or aryl) aldehydes with primary amine groups along the
chitosan backbone in a 50/50 (v/v) % of aqueous 0.2 M acetic acid
and ethanol. After reaction, the resulting Schiff bases, or imine
groups, are reduced to stable secondary amines by dropwise addition
of the reducing agent sodium cyanoborohydride. Alternatively, fatty
acid anhydride chemistry may be used, as described herein.
[0078] The degree of substitution of the hydrophobic substituent on
the polymer is up to 50% of available functional groups, for
example, amines in the case of chitosan. For example, the
hydrophobic substituent can be added to from 10 to 50% of available
amines, or from 20 to 50% of available amine, or from 30 to 50% of
available amines.
[0079] In some embodiments, the hydrophobic substituent is derived
from an amphiphilic compound, meaning it is composed of a
hydrophilic Head group and a hydrophobic Tail group. The Head group
binds with the polymer and positions the Tail group to extend from
the backbone of the polymer scaffold. This makes the hydrophobic
Tail group available for hydrophobic interactions. The Tail group
is a hydrocarbon of various forms.
[0080] Hydrocarbons that find use in accordance with this
disclosure may be classified as saturated hydrocarbons, unsaturated
hydrocarbons, and aromatic hydrocarbons. From this basic
classification system there exist many derivatives and further
types of compounds that build therefrom. For example, numerous and
varied compounds include more than one aromatic ring and are
generally referred to as polyaromatic hydrocarbons (PAH). In some
embodiments, the hydrophobic moiety is aliphatic. Aliphatic
compounds, carbon atoms can be joined together in straight chains,
branched chains, or rings (in which case they are called
alicyclic). They can be joined by single bonds (alkanes), double
bonds (alkenes), or triple bonds (alkynes). Besides hydrogen, other
elements can be bound to the carbon chain, the most common being
oxygen, nitrogen, sulfur, and chlorine. Those of ordinary skill in
the art will recognize that other molecules may also be bound to
the carbon chains and that compounds of such heteroatomic structure
are contemplated as falling within the scope of the current
invention.
[0081] The hydrophobic tail group of the amphiphilic compound bound
to the polymer backbone of the current invention is capable of
branching and/or allowing the inclusion of side chains onto its
carbon backbone. It may be understood that the strength of the
hydrophobic interaction is based upon the available amount of
"hydrophobes" that may interact amongst themselves or one another.
Thus, it may further promote the hydrophobic effect by increasing
the amount of and/or hydrophobic nature of the hydrophobic Tail
group that is interacting. For instance, a hydrophobic Tail group,
which in its original form may include a hydrocarbon chain, may
promote an increase in its hydrophobicity (ability to
hydrophobically bond and strength of hydrophobic interaction) by
having a hydrophobic side chain attach to one of the carbons of its
carbon backbone.
[0082] The side chains may be linear chains, aromatic, aliphatic,
cyclic, polycyclic, or any various other types of hydrophobic side
chains as contemplated by those skilled in the art. Some of the
contemplated hydrophobic side chains may include the following.
TABLE-US-00001 TABLE 1 Linear Alkanes Number of C Atoms Formula
Common Name 1 CH.sub.4 Methane 2 C.sub.2H.sub.6 Ethane 3
C.sub.3H.sub.8 Propane 4 C.sub.4H.sub.10 n-Butane 5 C.sub.5H.sub.12
n-Pentane 6 C.sub.6H.sub.14 n-Hexane 7 C.sub.7H.sub.16 n-Heptane 8
C.sub.8H.sub.18 n-Octane 9 C.sub.9H.sub.20 n-Nonane 10
C.sub.10H.sub.22 n-Decane 11 C.sub.11H.sub.24 n-Undecane 12
C.sub.12H.sub.26 n-Dodecane 13 C.sub.13H.sub.28 n-Trideacane 14
C.sub.14H.sub.30 n-Tetradecane 15 C.sub.15H.sub.32 n-Pentadecane 16
C.sub.16H.sub.34 n-Hexadecane 17 C.sub.17H.sub.36 n-Heptadecane 18
C.sub.18H.sub.38 n-Octadecane 19 C.sub.19H.sub.40 n-Nonadecane 20
C.sub.20H.sub.42 n-Eicosane 21 C.sub.21H.sub.44 n-Heneicosane 22
C.sub.22H.sub.46 n-Docosane 23 C.sub.23H.sub.48 n-Tricosane 24
C.sub.24H.sub.50 n-Tetracosane 25 C.sub.25H.sub.52 n-Pentacosane 26
C.sub.26H.sub.54 n-Hexacosane 27 C.sub.27H.sub.56 n-Heptacosane 28
C.sub.28H.sub.58 n-Octacosane 29 C.sub.29H.sub.60 n-Nonacosane 30
C.sub.30H.sub.62 n-Triacontane 31 C.sub.31H.sub.64
n-Hentraiacontane 32 C.sub.32H.sub.66 n-Dotriacontane 33
C.sub.33H.sub.68 n-Tritriacontane 34 C.sub.34H.sub.70
n-Tetratriacontane 35 C.sub.35H.sub.72 n-Pentatriacontane 36
C.sub.36H.sub.74 n-Hexatriacontane 37 C.sub.37H.sub.76
n-Heptatriacontane 38 C.sub.38H.sub.78 n-Octatriacontane 39
C.sub.39H.sub.80 n-Nonactriacontane 40 C.sub.40H.sub.82
n-Tetracontane 41 C.sub.41H.sub.84 n-Hentatetracontane 42
C.sub.42H.sub.86 n-Dotetracontane 43 C.sub.43H.sub.88
n-Tritetracontane 44 C.sub.44H.sub.90 n-Tetratetracontane 45
C.sub.45H.sub.92 n-Pentatetracontane 46 C.sub.46H.sub.94
n-Hexatetracontane 47 C.sub.47H.sub.96 n-Heptatetracontane 48
C.sub.48H.sub.98 n-Octatetracontane 49 C.sub.49H.sub.100
n-Nonatetracontane 50 C.sub.50H.sub.102 n-Pentacontane 51
C.sub.51H.sub.104 n-Henpentacontane 52 C.sub.52H.sub.106
n-Dopentacontane 53 C.sub.53H.sub.108 n-Tripentacontane 54
C.sub.54H.sub.110 n-Tetrapentacontane 55 C.sub.55H.sub.112
n-Pentapentacontane 56 C.sub.56H.sub.114 n-Hexapentacontane 57
C.sub.57H.sub.116 n-Heptapentacontane 58 C.sub.58H.sub.118
n-Octapentacontane 59 C.sub.59H.sub.120 n-Nonapentacontane 60
C.sub.60H.sub.122 n-Hexacontane 61 C.sub.61H.sub.124
n-Henhexacontane 62 C.sub.62H.sub.126 n-Dohexacontane 63
C.sub.63H.sub.128 n-Trihexacontane 64 C.sub.64H.sub.130
n-Tetrahexacontane 65 C.sub.65H.sub.132 n-Pentahexacontane 66
C.sub.66H.sub.134 n-Hexahexacontane 67 C.sub.67H.sub.136
n-Heptahexacontane 68 C.sub.68H.sub.138 n-Octahexacontane 69
C.sub.69H.sub.140 n-Nonahexacontane 70 C.sub.70H.sub.142
n-Heptacontane 71 C.sub.71H.sub.144 n-Henheptacontane 72
C.sub.72H.sub.146 n-Doheptacontane 73 C.sub.73H.sub.148
n-Triheptacontane 74 C.sub.74H.sub.150 n-Tetraheptacontane 75
C.sub.75H.sub.152 n-Pentaheptacontane 76 C.sub.76H.sub.154
n-Hexaheptacontane 77 C.sub.77H.sub.156 n-Heptaheptacontane 78
C.sub.78H.sub.158 n-Octaheptacontane 79 C.sub.79H.sub.160
n-Nonaheptacontane 80 C.sub.80H.sub.162 n-Otcacontane 81
C.sub.81H.sub.164 n-Henoctacontane 82 C.sub.82H.sub.166
n-Dooctacontane 83 C.sub.83H.sub.168 n-Trioctacontane 84
C.sub.84H.sub.170 n-Tetraoctacontane 85 C.sub.85H.sub.172
n-Pentaoctacontane 86 C.sub.86H.sub.174 n-Hexaoctacontane 87
C.sub.87H.sub.176 n-Heptaoctacontane 88 C.sub.88H.sub.178
n-Octaoctacontane 89 C.sub.89H.sub.180 n-Nonaoctacontane 90
C.sub.90H.sub.182 n-Nonacontane 91 C.sub.91H.sub.184
n-Hennonacontane 92 C.sub.92H.sub.186 n-Dononacontane 93
C.sub.93H.sub.188 n-Trinonacontane 94 C.sub.94H.sub.190
n-Tetranonacontane 95 C.sub.95H.sub.192 n-Pentanonacontane 96
C.sub.96H.sub.194 n-Hexanonacontane 97 C.sub.97H.sub.196
n-Heptanonacontane 98 C.sub.98H.sub.198 n-Octanonacontane 99
C.sub.99H.sub.200 n-Nonanonacontane 100 C.sub.100H.sub.202
n-Hectane 101 C.sub.101H.sub.204 n-Henihectane 102
C.sub.102H.sub.206 n-Dohectane 103 C.sub.103H.sub.208 n-Trihectane
104 C.sub.104H.sub.210 n-Tetrahectane 105 C.sub.105H.sub.212
n-Pentahectane 106 C.sub.106H.sub.214 n-Hexahectane 107
C.sub.107H.sub.216 n-Heptahectane 108 C.sub.108H.sub.218
n-Octahectane 109 C.sub.109H.sub.220 n-Nonahectane 110
C.sub.110H.sub.222 n-Decahectane 111 C.sub.111H.sub.224
n-Undecahectane
II. Cyclic Compounds
[0083] a. Alicyclic Compound/Cycloalkane/Cycloalkene: An organic
compound that is both aliphatic and cyclic with or without side
chains attached. Typically include one or more all-carbon rings
(may be saturated or unsaturated), but NO aromatic character. b.
Aromatic hydrocarbon/Polycyclic aromatic hydrocarbon/Heterocyclic
compound: Organic compounds with a ring structure containing atoms
in addition to carbon, such as nitrogen, oxygen, sulfur, chloride,
as part of the ring. May be simple aromatic rings, non-aromatic
rings. Some examples are pyridine (C5H5N), Pyrimidine (C4H4N2) and
Dioxane.
TABLE-US-00002 TABLE 2 Cyclic Compounds Example Polycyclic
Compounds Sub-Types Compounds Bridged Compound - Bicyclo compound
adamantine compounds which contain amantadine interlocking rings
biperiden memantine methenamine rimantadine Macrocyclic Compounds
Calixarene Crown Compounds Cyclodextrins Cycloparaffins Ethers,
Cyclic Lactans, macrocyclic Macrolides Peptides, Cyclic
Tetrapyrroles Trichothecenes Polycyclic Hydrocarbons, Acenaphthenes
Aromatic. Anthracenes Azulenes Benz(a)anthracenes
Benzocycloheptenes Fluorenes Indenes Naphthalenes Phenalenes
Phenanthrenes Pyrenes Spiro Compounds Steroids Androstanes Bile
Acids and Salts Bufanolides Cardanolides Cholanes Choestanes
Cyclosteroids Estranes Gonanes Homosteroids Hydroxysteroids
Ketosteroids Norsteroids Prenanes Secsteroids Spirostans Steroids,
Brominated Steroids, Chlorinated Steroids, Fluorinated Steroids,
Heterocyclic
Examples
Materials and Methods
Hydrophobic Modification of Chitosan; Synthesizing Hm-Chitosan
Using Dodecandoic Anhyride and Palmitic Anhydride
[0084] The following describes the general method of the creation
of variable-length hm-chitosan via anhydride chemistry. Two grams
of chitosan was dissolved in 100 mL of 0.2 M acetic acid by
stirring for 30 minutes in a beaker covered with aluminum foil. The
solution was filtered using a vacuum filter. Once the chitosan
solution was poured from the flask into a 600 mL beaker, 100 mL of
ethanol was added to the flask gradually and swirled around to
remove the remaining chitosan on the sides of the flask. The
ethanol and remaining chitosan was poured into the beaker with the
rest of the chitosan and the solution was heated to 60.degree. C.;
the pH was adjusted to 6.0 by dropwise addition of 0.5 M NaOH. In a
separate beaker, 20 mL of ethanol was added to a mixture of
dodecanoic anhydride (0.24 g for 5% modification) and palmitic
anhydride (0.061 g for the 1% modification); the solution was also
heated to 60.degree. C. to fully dissolve the fatty anhydrides, and
it was then slowly poured into the chitosan solution. The mixture
was stirred for 24 hours under heat and the hm-chitosan was then
precipitated from the solution by adding 0.2 M sodium hydroxide
dropwise.
Rheology of Blood and Chitosan Solution
[0085] An AR2000 advanced rheometer with a cone and plate geometry
was used to measure the dynamic viscoelastic properties for the
experiments of this disclosure. The cone had a 40 mm diameter with
a 2-degree angle. In order to ensure that all the measurements were
within the linear viscoelastic regions, first stress amplitude
sweeps were performed. After the human blood was drawn into the
test tubes with the heparin, a pipette was used to add 1 mL of
blood onto the plate of the rheometer. Then 1 mL of the chitosan
(or hm-chitosan) solution (or foam) was added to the blood on the
plate. Once the solutions were combined, the parameters for the
rheometer were set up and the run was started. The cone lowered
into contact with the solution and a sinusoidal strain was
subjected to the subject with increasing frequency of oscillations.
The elastic and viscous moduli were obtained over the frequency
range of 0.01 to 10 Hz. Dynamic rheology experiments were performed
using unmodified chitosan and variable length
hydrophobically-modified chitosans.
Foam Canisters
[0086] Variable length hm-chitosan was produced by attaching
dodecyl anhydride (5 mol % of available amines) and oleic anhydride
(1 mol % of available amines) to the chitosan backbone (using a
process similar to that described above). All of the hm-chitosan
solutions used contained 1.25% modified chitosan with C-12 tails
and either a high or a low concentration C-18 tails in a lactate
solution. The hm-chitosan, unmodified, and saline solutions were
then loaded into spray canisters with AB-46 propellant and a
mixture of propane and butane gas before they were ready for use.
The canister was approximately in a 70/30 ratio of solution to
propellant, which was used in calculating the ratio of blood and
saline to add during testing.
[0087] Foam samples were sprayed directly onto the rheometer test
plate to a mass of approximately 500 g. The blood tests were all
performed using a 1 .mu.g:1.mu.L ratio of solution (70% of the can
mass difference) to heparinized bovine whole blood. The tests using
saline were performed by adding 400.mu.L of 0.9 wt % NaCl solution
to the mixture per 500.mu.L of blood that was added, or by adding
400 .mu.L of saline solution per 500 .mu.L of blood, if blood was
to be added (in the case of no blood tests). The tests using
.alpha.-CD used the same ratio as the saline: 400.mu.L of 100 .mu.M
.alpha.-CD in 0.9 wt % NaCl solution were added per 500.mu.L of
blood. After addition of blood or treatment to the foam, the
mixture was then stirred using a micropipette tip in order to
ensure even distribution of the blood or treatment throughout the
foam mixture.
[0088] All steady and dynamic rheology was performed on a TA
Instruments AR2000 rheometer with a cone and plate geometry of 40
mm diameter and 4.degree. cone angle. All tests were performed at
the physiological temperature of 37.degree. C. and using a test gap
of 118 .mu.m. A dynamic strain sweep was used to determine the
linear viscoelastic region of the sample in order to outline the
spectrum for the dynamic frequency test.
Biodegradation
[0089] To measure initial degradation rates of material, we
measured the viscosity of an aqueous solution of 1 wt % hm-chitosan
solution (0.2M acetic acid) exposed to chicken egg lysozyme (1 wt
%) after one hour. Before addition of lysozyme, the pH of the
hm-chitosan solution was adjusted to 5.5 pH via dropwise addition
of NaOH (1.0M) under stirring. The zero-shear viscosity at time=0
was compared to the zero shear viscosity at time=1 h via AR 2000
Stress controlled rheometer. The initial degradation rate is
expressed as (Viscosity initial-Viscosity final)/(Viscosity
final).
Results
[0090] In FIG. 3, 0.5 mL of a 1.5 wt % solution of modified
hm-chitosan was mixed with 0.5 mL of heparinized bovine blood. In
the left vial shown in FIG. 3, a variable-length design of 5 mol %
C6, 5 mol % C10 variable length hydrophobically modified chitosan
was mixed with the blood. The resulting mixture was a gel that
holds its own weight upon vial inversion. In the right vial, a 1.5
wt % solution of 10 mol % C8 hydrophobically modified chitosan was
mixed with heparinized bovine blood. The native chitosan was a
medium molecular weight chitosan (hqg 400 from Primex
(Iceland)).
[0091] This was a single-length grafting design in this experiment,
which had the exact same hydrophobic density as the previously
described variable-length composition. However, the gelation
properties of the two solutions are distinctly different when mixed
with blood. While both polymers have the same hydrophobic density,
they have significantly different gelation properties. This is a
fundamental example of how variable length designs along the
chitosan backbone allow for optimized outcomes with respect to
ultimate material handling and performance characteristics. The
hydrophobically-modified polymers disclosed herein could be useful
as hemostatic biomaterials for treatment of bleeding, from minor
oozing in surgeries to severe lacerations in a traumatic event.
[0092] Foams (prior to gelling experiment) were compared to gelled
foam to ensure that the results of the rheology were because of the
gelling of the blood and not a result of the foams initial
properties. As shown in FIG. 7, the hm-chitosan foam appears to
have some structure prior to the addition of blood. In order to
show that the foam structure was not affecting the gelling of the
blood, the steady-shear viscosities were compared for both the
hm-chitosan (C12 (5 mol %) and C18 (1 mol %) attached) and the
unmodified chitosan. FIG. 7 shows that while the modified and
unmodified foams (both at initial concentration of 1.25 wt % in the
canister) have viscosities greater than that of a saline solution,
the addition of blood greatly increases the viscosity because of
the gelation of the chitosan polymers.
[0093] FIG. 8 also demonstrates how the addition of the variable
length hydrophobically modified tails improves the ability of
chitosan to gel blood. The addition of hydrophobic tails to the
chitosan backbone (C12 (5 mol %) and C18 (2.5 mol %) attached)
significantly increased the viscosity and yield stress of the foam
and blood mixture. Without the addition of the tails, the chitosan
foam was unable to successfully gel the blood, similar to the
results of the variable length hm-chitosan solution. Both the
chitosan and hm-chitosan had initial concentrations of 1.25 wt % in
the canister.
[0094] Other preferred multi-variable embodiments for gelation of
blood are shown below in Table 3. "%" refers to mol % as described
elsewhere herein. All hydrophobic design grafts are attached to a
medium molecular weight chitosan (Primex hqg 400). Preferred
concentrations of the below variable-length hm-chitosans are 0.1 to
2.5 wt %. Preferred counteracids are acetic acid, hydrochloric
acid, L-lactic acid, citric acid and glutamic acid, each acid
concentration being 1 to 2 wt % in water. Grafting of different
sizes are randomly distributed along the backbone due to a free
reaction of a mixture of fatty anhydrides.
TABLE-US-00003 TABLE 3 Exemplary embodiments for blood gelation %
C6 % C8 % C10 % C12 % C14 % C16 % C18 Order 5 5 2.degree. 4 4
2.degree. 10 1 2.degree. 8 1 2.degree. 6.5 1 2.degree. 5 1
2.degree. 3 1 2.degree. 5 2 1 3.degree. 2 1 2.degree. 1 1 1
3.degree. 5 1 2.degree. 5 2.5 2.degree. 10 3 1 3.degree. 1 2 1 0.5
4.degree. 1 1 2 1 4.degree.
[0095] Hydrophobically-modified polymers that balance tissue
adhesive properties with material cohesive properties were
constructed. In general, biopolymer hemostatic dressings, including
chitosan-based dressings, must first adhere quickly and strongly to
the site of bleeding in order to create a robust seal. Furthermore,
in order to hold back bleeding, the dressings must also be cohesive
enough to avoid collapse under high-pressure blood flow. Typically,
chitosan dressings fail due to either a lack of adherence to the
wound site or a lack of coherence once an initial seal has been
achieved. Native chitosan is particularly good at adhering to wet,
bleeding tissue. However, native chitosan generally has a limited
ability to hold together under high-pressure blood flow.
[0096] According to this disclosure, it was discovered that certain
hydrophobes are more advantageous for optimizing adherence, and
other hydrophobes are more advantageous for improving coherence.
For example, in the range of C6-C12 lengths, the hydrophobic grafts
are useful in improving adhesion of the chitosan dressing, and in
the range of C13-C22 lengths, the hydrophobic grafts are useful in
improving the cohesion of the dressings. By mixing hydrophobic
grafts, for example in a preferred embodiment of 5 mol % C12 and
1.0 mol % C18 attached to a medium molecular weight chitosan
(MW-250 kDa), a composition was created which had improved
characteristics compared to either: (1) native chitosan; (2) 5% C12
chitosan only; or (3) 1.0% C18 chitosan only. This composition
allowed for the following improvements over a single length
hydrophobically modified chitosan:
[0097] (A) In a syringeable gel format: A gel was produced at 1.0
wt % solution of variable length modified hm-chitosan (5 mol % C12
and 1.0 mol % C18) (in aqueous 0.15 M lactic acid). This gel was
thick, but had flowability through syringe dispensing. The C12
component of the formulation allowed for robust attachment of the
gel to the mucosal surface, and the C18 component allowed for
cohesive matrix properties as the blood began to infiltrate the
gel.
[0098] (B) In a lyophilized sponge format: A sponge was created by
lyophilizing a 1.0 wt % solution of variable length modified
hm-chitosan (5 mol % C12 and 1.0 mol % C18) (in aqueous 0.2M acetic
acid) at -40.degree. C. and 50 microbar (.mu.bar), which had a
similar look and feel to a native chitosan lyophilized sponge, or a
single length hydrophobically modified chitosan sponge. However,
when contacted with a bleeding wound, the dressing not only adhered
strongly to the bleeding tissue (relative to native chitosan), but
also held together even in the presence of significant blood
pressure. Thus, while a single-length 5 mol % C12 adheres
significantly more than native chitosan to wet tissue, it fails
upon application of blood pressures much greater than 100 mmHg.
Particularly during resuscitation after trauma, there can be a
significant risk of re-bleeding at resuscitation pressures.
[0099] (C) In a clear film format: A clear film was created by
oven-drying a 1.0 wt % solution of variable length modified
hm-chitosan (5 mol % C12 and 1.0 mol % C18) (in aqueous 0.2M acetic
acid) at 60.degree. C. and 1 atm, which had a similar look and feel
to a native chitosan film, or a single length hydrophobically
modified chitosan film. However, when contacted with a bleeding
wound, the film not only adhered strongly to the bleeding tissue
(relative to native chitosan), but also held together in the
presence of significant blood pressure. Thus, while a single-length
5 mol % C12 adheres significantly more than native chitosan to wet
tissue, it fails upon application of blood pressures much greater
than 30 mmHg. An ability to stand up to such pressures creates an
issue in most clinical bleeding scenarios.
[0100] (D) In a powderized format: A powder was created by milling
a lyophilized sponge produced at 1.0 wt % solution of variable
length modified hm-chitosan (5 mol % C12 and 1.0 mol % C18) (in
aqueous 0.2M acetic acid) at -40.degree. C. and 50 .mu.bar, which
had a similar look and feel to a native chitosan powder, or a
single length hydrophobically modified chitosan powder. However,
when contacted with a bleeding wound, the powder not only adhered
strongly to the bleeding tissue (relative to native chitosan), but
also held together in the presence of significant blood pressure.
Thus, while a single-length 5 mol % C12 powder adheres
significantly more than native chitosan to the wet tissue, it fails
upon application of blood pressures much greater than 100 mmHg.
Again, during resuscitation after trauma, there can be a
significant risk of re-bleeding at resuscitation pressures.
[0101] (E) In a sprayable foam format: A sprayable foam was created
using a gel at 1.0 wt % solution of variable length modified
hm-chitosan (5 mol % C12 and 1.0 mol % C18) (in aqueous 0.15 M
lactic acid), which was thick, but had dispensability into an
aluminum canister. The canister was then pressurized with a
liquefied gas (e.g. isobutene, isopentane, dimethyl ether), and
crimped with a valve that allowed the canister to be opened to the
atmosphere. The C12 component of the formulations allowed for a
large expansion of the foam relative to the initial gel volume,
whereas the C18 component allowed for a mechanically integral final
foam product.
[0102] (F) In an injectable foam format: An injectable foam was
created using a gel at 1.0 wt % solution of variable length
modified hm-chitosan (5 mol % C12 and 1.0 mol % C18) (in aqueous
0.2 M acetic acid), which was thick, but was Tillable into one side
of double-barrel syringe. In the other side of the syringe, an
aqueous solution of 0.3M sodium bicarbonate. The material in both
sides are mixed via a mixing tip, which intakes output from both
barrels simultaneously. Upon mixing, carbon dioxide gas is
generated due to reaction between the acetic acid and sodium
bicarbonate. The C12 component of the formulations allowed for a
large expansion of the foam relative to the initial gel volume,
whereas the C18 component allowed for a mechanically integral final
foam product.
[0103] (G) In moldable putty format: The gel at 1.0 wt % solution
of variable length modified hm-chitosan (5 mol % C12 and 1.0 mol %
C18) (in aqueous 0.15 M lactic acid) was thick, but had an ability
to mix with polyvinyl alcohol and sodium tetraborate to create a
putty-like mechanical characteristic. The C12 component of the
formulations allowed for robust attachment of the putty to the
mucosal surface, whereas the C18 component allowed for cohesive
matrix properties as the blood began to infiltrate the putty.
[0104] In accordance with this disclosure, hydrophobically-modified
chitosans were prepared with altered biodegradation profiles.
Hydrophobic groups below the length of C6 do not contribute towards
improved hemostatic effect of the chitosan polysaccharide. However,
hydrophobic modification in the range of C1 to C6 do allow for a
framework to optimize the degradation of the material inside the
body via lysozymes. Particularly in the case of surgical-use
hemostats, it is ideal for the hemostatic biomaterial to degrade
quickly after achieving hemostasis.
[0105] By mixing hydrophobic grafts, for example in a preferred
embodiment of 5% C12 and 30% C1 attached to a medium molecular
weight chitosan (MW-250 kDa), a composition was created which had
improved biodegradation characteristics relative to either: (1)
native chitosan, (2) 5% C12 chitosan only, or (3) 30% C1 chitosan
only.
[0106] In other embodiments, chitosan-based materials can be useful
as anti-microbial agents due to their bacteriostatic effect. While
the mechanism of action of chitosan as an anti-microbial is not
well understood, two key contributing mechanisms likely play a
role: (1) penetration into the bacterial cells and intercalation
with plasmid DNA, thus preventing replication; and, (2) physical
immobilization of cells due to physical binding of bacteria into a
robust cohesive network. Smaller hydrophobes C1-C12 assist with
interfacing with the cell membrane and/or cell wall; larger
hydrophobes C13-C22 assist with physical binding of the bacteria
into immobilized networks. Hence, the variable-length design
framework, along a wide span of chitosan backbone lengths, allows
for the creation of many unique molecules which can amplify a given
mechanism towards bacterial death depending upon the clinical
circumstances. Certain bacteria are more susceptible to penetration
through the cell wall (typically gram negative); and infections
caused by robust bacteria may be limited to treatment via molecules
that work only by physical bacteriostasis (e.g. bacteria which have
genetically mutated to become resistant to traditional small
molecule antibiotic agents).
* * * * *