U.S. patent application number 11/107230 was filed with the patent office on 2005-09-01 for filamentary means for introducing agents into tissue of a living host.
This patent application is currently assigned to Aderans Research Institute, Inc.. Invention is credited to Barrows, Thomas H..
Application Number | 20050191748 11/107230 |
Document ID | / |
Family ID | 34437121 |
Filed Date | 2005-09-01 |
United States Patent
Application |
20050191748 |
Kind Code |
A1 |
Barrows, Thomas H. |
September 1, 2005 |
Filamentary means for introducing agents into tissue of a living
host
Abstract
The present invention provides a filamentary structure for the
introduction of agents into a living host, comprising a filament
comprising a solid core and a porous sheath which coats at least a
portion of the solid core. When the filamentary structure is to be
permanently implanted into a living host, both the solid core and
the porous sheath are bioabsorbable. When the filamentary structure
is to be temporarily implanted into the skin of a living host to
deliver agents, such as cells, therein, the porous sheath is
preferably bioabsorbable but the core need only be biocompatable,
not bioabsorabable. The devices and methods of the present
invention enable one to regenerate hair follicles, to introduce
genetically altered cells or encapsulated cells to a living host
transdermally, to regenerate bones, and to deliver drugs
transdermally.
Inventors: |
Barrows, Thomas H.;
(Austell, GA) |
Correspondence
Address: |
MICHAEL BEST & FRIEDRICH, LLP
ONE SOUTH PINCKNEY STREET
P O BOX 1806
MADISON
WI
53701
|
Assignee: |
Aderans Research Institute,
Inc.
Beverly Hills
CA
|
Family ID: |
34437121 |
Appl. No.: |
11/107230 |
Filed: |
April 15, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11107230 |
Apr 15, 2005 |
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09890888 |
Aug 7, 2001 |
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6884427 |
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09890888 |
Aug 7, 2001 |
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PCT/US00/03488 |
Feb 8, 2000 |
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60119082 |
Feb 8, 1999 |
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Current U.S.
Class: |
435/459 ;
435/371 |
Current CPC
Class: |
A61L 27/3847 20130101;
A61L 27/3804 20130101; A61F 2250/0068 20130101; A61F 2/10
20130101 |
Class at
Publication: |
435/459 ;
435/371 |
International
Class: |
C12N 005/08; C12N
015/87 |
Claims
1-34. (canceled)
35. A method of facilitating the growth of new bone comprising the
steps of: a) providing an implantable device comprising a plurality
of filaments, wherein each filament comprises a solid core and a
porous sheath of a bioabsorbable material which coats at least a
portion of the core; b) seeding the implantable device osteogenic
substance; and c) implanting the device in a site where bone
regeneration is desired.
36. (canceled)
37. The method of claim 35, wherein the core is removed from the
implantable device before the device is implanted.
38. The method of claim 35 wherein the plurality of filaments forms
a three-dimensional porous matrix.
39. The method of claim 35, wherein the bioabsorbable sheath
polymer is selected from the group consisting of poly(lactic acid),
poly(glycolic acid), poly(trimethylene carbonate), poly(amino
acid)s, tyrosine-derived poly(carbonate)s, poly(carbonate)s,
poly(caprolactone), poly(para-dioxanone), poly(ester)s,
poly(ester-amide)s, poly(anhydride)s, poly(ortho ester)s, proteins,
carbohydrates, poly(ethylene glycol)s, poly(propylene glycol)s,
poly(acrylate ester)s, poly(methacrylate ester)s, poly(vinyl
alcohol), and copolymers, blends and mixtures of said polymers.
40. The method of claim 39, wherein the bioabsorbable sheath
polymer is poly(lactic acid).
41. The method of claim 35, wherein the core comprises a
ceramic.
42. The method of claim 35, wherein the core comprises a glass.
43. The method of claim 35, wherein the core comprises a metal.
44. The method of claim 35, wherein the osteogenic substance
comprises a cell selected from the group consisting of an
osteoblast and a chondrocyte.
45. The method of claim 35, wherein the implantable device is
sculpted prior to implanting the device.
46. The method of claim 35, wherein the site is an intervertebral
space in the spine where fusion is desired.
47. The method of claim 35, wherein the site is a bone defect or
gap.
48. The method of claim 35, wherein the implantable device is
stored in a frozen state prior to implanting the device.
49. An implantable device comprising a plurality of filaments and
an osteogenic substance, wherein each filament comprises a solid
core and a porous sheath of a bioabsorbable material which coats at
least a portion of the core.
50. The device of claim 49, wherein the plurality of filaments
forms a three-dimensional porous matrix.
51. The device of claim 49, wherein the bioabsorbable sheath
polymer is selected from the group consisting of poly(lactic acid),
poly(glycolic acid), poly(trimethylene carbonate), poly(amino
acid)s, tyrosine-derived poly(carbonate)s, poly(carbonate)s,
poly(caprolactone), poly(para-dioxanone), poly(ester)s,
poly(ester-amide)s, poly(anhydride)s, poly(ortho ester)s, proteins,
carbohydrates, poly(ethylene glycol)s, poly(propylene glycol)s,
poly(acrylate ester)s, poly(methacrylate ester)s, poly(vinyl
alcohol), and copolymers, blends and mixtures of said polymers.
52. The device of claim 51, wherein the bioabsorbable sheath
polymer is poly(lactic acid).
53. The device of claim 49, wherein the core comprises a
ceramic.
54. The device of claim 49, wherein the core comprises a glass.
55. The device of claim 49, wherein the core comprises a metal.
56. The device of claim 49, wherein the osteogenic substance
comprises a cell selected from the group consisting of an
osteoblast and a chondrocyte.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/119,082, filed Feb. 8, 1999.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not Applicable.
BACKGROUND OF THE INVENTION
[0003] This invention relates to means for the delivery of agents
into a living body. More specifically it relates to filaments
comprising porous bioabsorbable polymers, which facilitate the
implantation of living cells and other agents, such as drugs, into
specific tissues, including skin and bone, for the purposes of
site-specific drug or cell release, gene therapy, and the
facilitation of the regeneration of tissue, including the
regeneration of bone and hair tissue.
[0004] Current means for the delivery of agents such as drugs,
growth factors, genetically modified cells, and the like into a
living body include various pharmaceutical dosage forms, such as
ingestable tablets, patches designed to deliver agents
transdermally, and surgically implantable devices designed to
deliver agents to an implant site. Early implantable devices were
not bioabsorbable, and had to be surgically removed after they had
been used for their intended purpose. More recently, implants of
bioabsorbable polymers have been developed. Such implants are
absorbed by the host in which they are implanted after, or in the
course of serving their intended purpose. One such device,
disclosed by Dunn et al. in U.S. Pat. No. 5,599,552 ("Dunn et al.
'552"), is an implant of a porous core of a bioabsorbable polymer,
surrounded by a non-porous surface skin of the bioabsorbable
polymer. That particular device is designed for use in delivering a
biologically active agent to a living host when implanted therein.
The device disclosed by Dunn et al. '552 is also designed so that
it can act as a matrix to promote tissue regeneration at an implant
site. (Id.)
[0005] Two other types of implantable devices of bioabsorbable
polymers are disclosed in U.S. Pat. No. 5,847,012 ("Shalaby et al.
'012"). One such device consists of a bioabsorbable microporous
polymeric foam with open-cell pores. The other such device consist
of an implant with a modified surface, consisting of a surface
layer of bioabsorbable microporous polymeric foam with open-cell
pores. (Id.) The implants of Shalaby et al. '012 are designed to
accept the agent to be delivered, such as a medicament or growth
factor, and to deliver the agent to a living patient after
implantation therein.
[0006] Textile technologies have also been adapted for use in
making biodegradable woven fabrics as tissue engineering scaffolds.
See Introduction of Peter X. Ma and Ruiyun Zhang in J. Bionied.
Materials Res. 46(1):60-72 (July 1999). The diameter of the
biodegradable fibers used to produce such woven scaffolds is about
15 .mu.m. Ma and Zhang demonstrated that fibers with a considerably
smaller diameter, ranging from 50 to 500 nm could be created from
biodegradable aliphatic polyesters. The woven scaffolds of Ma and
Zhang, and those described therein were designed for use as
scaffolds, and not as means for delivery of agents to tissue.
[0007] The advantage of all the bioabsorbable devices described
above was that they could be implanted into a living host and left
in place to do what they were designed to do, without the necessity
of removal therefrom. The devices would be absorbed by the host
over time. Of the bioabsorbable devices disclosed in the references
described above, only the device of Dunn et al. '552 is designed to
act as both scaffolding and delivery agent. That device has limited
flexibility, because of the way it is designed. What is needed is a
bioabsorbable fiber or composite thereof, which is capable of being
processed into a scaffolding for tissue formation, and which is
capable of delivering agents to a living host when implanted
therein. The present invention meets that need.
[0008] The present invention also meets a need for an inexpensive
and relatively painless means for regenerating hair. Plastic
surgery is one of the few means available to correct male pattern
baldness, today. In that particular surgical procedure, the amount
of permanently hair-bearing donor tissue available can
significantly affect the feasibility and outcome of the procedure.
In vitro growth techniques have been developed to increase the
amount of hair follicle cells available for use in such procedures.
See, e.g., Seigi Arase, et al. Tokushima J. exp. Med 36: 87-95
(1989); and Edoardo Raposio, et al. Plastic and Reconstructive
Surgery pp. 221-226 (July 1998). What is needed is a relatively
painless and inexpensive means for the regeneration of hair, one
which does not involve plastic surgery or other painful and
expensive implantation techniques, preferably, a technique which
produces hair which looks realistic and similar to other hair on
the same host. The present invention utilizes a modified form of
the bioabsorbable polymeric means developed for use in implantable
devices, as described above, to deliver hair follicle cells
transdermally and to promote the regeneration of hair therein.
[0009] As is shown in the next section, below, the present
invention provides a new means for the introduction of agents into
a living host, a means which offers several advantages over known
means in use today, such as those described briefly above.
BRIEF SUMMARY OF THE INVENTION
[0010] The present invention provides a filamentary means for the
introduction of agents into a living host, comprising a filament
comprising a solid core and a porous sheath which coats at least a
portion of the solid core. When the filamentary means is to be
permanently implanted into a living host, both the solid core and
the porous sheath are bioabsorbable. When the filamentary means is
to be temporarily implanted into the skin of a living host to
deliver agents, such as cells, therein, the porous sheath is
preferably bioabsorbable but the core need only be biocompatable,
not bioabsorabable.
[0011] The solid core is preferably wire when the filamentary means
is designed to be used to deliver an agent, such as hair follicle
cells, into the skin of a living host. The solid core is preferably
glass or ceramic when the filamentary means is to be used to
deliver an agent, such as cells or pharmaceutical agents, into bone
through implantation of the filamentary means into the body of the
host.
[0012] The porous sheath is preferably in the form of reticulated
foam that is well adhered to the core but is capable of separating
from the core after a period of several days in vivo. When the
agent to be delivered with the filamentary means is a drug, the
porous sheath is preferably in the form of a hydrogel and the
porosity is on a molecular size scale.
[0013] The filamentary means of the present invention provides
means for delivery of cells or other agents from outside the body
of a living host into the skin of the host, such as a mammal, with
minimal trauma to the host. When the filamentary means is comprised
of a bioabsorbable core with a bioabsorbable porous sheath which
coats at least a portion of the core, the filamentary means can be
implanted into specific tissue within a living host and used to
deliver agents to the specific tissue when implanted therein. The
implantable embodiment of the filamentary means can serve as a
surface for osteoblast attachment and as a scaffold for bone
regeneration upon implantation into the bone tissue of a living
host. The above-cited features of the filamentary means of the
present invention enable it to be used for a variety of purposes
including, but not limited to, hair follicle regeneration, gene
therapy and encapsulated cell delivery, bone regeneration, and
trans-dermal drug delivery.
[0014] Another embodiment of the present invention is a method of
making a filamentary means for introducing an agent into a living
host, comprising providing a solid filament, a bioabsorbable
polymer, and a pore-forming agent, mixing the bioabsorbable polymer
with the pore-forming agent, coating the resulting mixture onto at
least a portion of the filament, and substantially removing or
decomposing the pore-forming agent.
[0015] Other embodiments of the present invention include devices
designed to enable one to use the filamentary means of the
invention to deliver various agents into a living host, methods for
making such devices, and methods for using the devices of the
present invention to deliver agents into a living host. The devices
and methods of the present invention enable one to regenerate hair
follicles, to introduce genetically altered cells or encapsulated
cells to a living host transdermally, to regenerate bones, and to
deliver drugs transdermally. The devices and methods of the present
invention are described briefly below.
[0016] One embodiment of the present invention is a hair follicle
cell implant device designed to implant hair follicle cells into
the skin of a living host. Another embodiment of the hair follicle
cell implant device of the present invention is a method of making
the implant device. Yet another embodiment is a method of using the
implant device to deliver hair follicle cells to implant such cells
into the skin of a living host, preferably into the scalp of a
human being suffering from male pattern baldness. The hair follicle
cell implant device of the present invention comprises a plurality
of filaments, each of which has a first end and a second end and
comprises a solid core and a bioabsorbable porous sheath which
coats the solid core, and a semi-rigid backing with the second end
of each filament embedded therein such that the first end of each
filament protrudes therefrom. The first end of each filament
protrudes from the semi-rigid backing a sufficient length to
penetrate the skin of a living host when the device is in contact
therewith. The filaments are preferably spaced the same distance
apart as hairs on the normal surface of skin of the living
host.
[0017] The hair follicle cell implant device of the present
invention is preferably made by the steps comprising: providing a
plurality of filaments, each of which has a first end and a second
end and comprises a solid core and a bioabsorbable porous sheath
which coats the solid core; and fixing the second end of each of
the plurality of filaments in a semi-rigid backing such that the
filaments are spaced the same distance apart as hairs on the skin
of a normal living host, and such that the second end of each of
the plurality of filaments protrudes from the semi-rigid backing at
a depth sufficient to penetrate the skin of the living host when
placed into contact therewith.
[0018] The hair follicle cell implant device is used to stimulate
hair growth according to a method comprising: seeding the
boabsorbable porous sheath at the first end of each filament with
hair follicle cells, introducing the cells into the skin of a
living host by puncturing the skin with the first end of each
filament, and removing the device from the skin after sufficient
time has passed to allow the porous coating within the skin to
separate from the solid core of each filament, leaving the porous
coating and hair follicle cells in the skin.
[0019] One advantage of the hair follicle cell implant device and
methods of making and using the same is that they provide means for
delivering cultured cells harvested from hair follicles into the
skin of a host, such as the bald scalp of a human male, such that
said cells are able to generate new hair follicles. The new hair
follicles, once generated, will continue to grow and be maintained
in the dermis of the host. Another advantage of these embodiments
of the present invention is that they provide a means for the
simultaneous implantation of hair follicle cells into multiple
sites in the skin such that the spacing between each individual
implant is approximately the same as the spacing between the hair
follicles in the normal scalp. Regenerated hair grown from follicle
cells implanted in such a pattern have a natural, cosmetically
appealing look. Thus, the present invention provides an efficient
device and method of restoring a normal density of normally
functioning hair follicles in the hairless scalp as an effective,
natural, and permanent remedy for baldness.
[0020] In another aspect, the present invention is a method of
using the filamentary means of the present invention to deliver
genetically modified cells into normal healthy skin, such that the
cells deliver a therapeutically efficacious systemic level of the
desired gene product. In this embodiment, a filamentary means
comprising a filament comprising a solid core having a first end
and a second end and a porous sheath which coats at least the first
end of the solid core, wherein the porous sheath is bioabsorbable,
is used to deliver genetically modified cells into the skin of a
living host, according to the steps comprising: providing the
filament, seeding the porous sheath at the first end of the
filament with the genetically transformed cells, introducing the
cells into the skin of the living host by puncturing the skin with
the first end of the filament, and removing the filament from the
skin after sufficient time has passed to allow the porous coating
to separate from the filament at the first end of the solid core of
the filament, leaving the porous coating and genetically
transformed cells in the skin.
[0021] An advantage of this embodiment of the present invention is
that it provides a means for the delivery of encapsulated or
otherwise immunoprotected cells into normal healthy skin such that
the cells delivered therewith take over the function of cells in
other organs that have lost their required function due to disease
such as diabetes. Another advantage of this embodiment of the
invention is that it also provides a means for the delivery of
genetically modified cells into diseased or ulcerated skin to treat
the disease or provide growth factors to heal the ulcers.
[0022] An advantage of another embodiment of the present invention
is that it provides that a rigid scaffold with a highly porous
surface, which can be implanted into a living host, and maintained
for a long enough period of time to facilitate new bone formation.
The porous surface enables this embodiment of the invention to be
used as a means for the delivery of osteoblasts and/or other
osteoinductive substances into bone defects, gaps, or fusion
devices.
[0023] Another embodiment of the present invention is a device for
delivery of a drug through the skin, comprising: a plurality of
filaments each of which has a fist end and a second end and
comprises a solid core and a bioabsorbable polymer sheath in which
the drug is soluble and permeable; a semi-rigid backing having a
first side and a second side, wherein the second side of the
semi-rigid backing defines a reservoir, wherein each of the
plurality of filaments is fixed in the semi-rigid backing such that
the first end of each filament protrudes from the first side of the
semi-rigid backing and the second end of each filament extends to
the second side of the semi-rigid backing such that it is in
contact with the reservoir. An advantage to the device of delivery
of a drug through the skin of the present invention is that it
provides a means for the continuous delivery of drugs through the
skin that normally do not penetrate skin from a reservoir placed on
the surface of the skin.
[0024] Other advantages of the filamentary means for the delivery
of agents into a living body of the present invention will become
apparent upon disclosure of the invention as described below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] FIG. 1a is a schematic view of the filament in longitudinal
section, showing the solid core (1) and the porous sheath (2),
without details of the porous structure.
[0026] FIG. 1b is a schematic view of the filament in transverse
section, showing the solid core (1) and porous sheath (2).
[0027] FIG. 2 is a schematic sectional view of a hair implant
device with an array of the core-sheath filaments (3) shown
imbedded in a semi-rigid backing (4) which maintains the filaments
in a stable, rigid parallel configuration.
[0028] FIG. 3 is a schematic sectional view of the hair implant
device with the array of filaments (3) imbedded in the semi-rigid
backing (4), immersed in a vessel (5) containing a tissue culture
broth of free floating cells (6) derived from the hair follicles of
a living host.
[0029] FIG. 4a depicts a sectional view of a single filament with
cultured cells (6) contained within the porous sheath (2)
surrounding the solid core (1) of a filament, which has been
implanted in the skin through the full thickness of the dermis (7).
The filament has been present in the skin for several days during
which time the epidermis (8) has begun to grow down the outside of
the filament.
[0030] FIG. 4b depicts a sectional view of the implant site after
the filament core (1) has been removed by pulling out the
semi-rigid backing (4) to which it is attached out of the dermis
(7) and epidermis (8). Note the resulting separation of the porous,
cultured cell laden sheath (2) from the core. As shown in this
figure, the implanted sheath has been present for a long enough
time that new matrix cells (9) are beginning to elongate a new hair
shaft (10).
[0031] FIG. 5a depicts a sectional view of a single filament with
cultured cells (6) contained within the porous sheath (2)
surrounding the solid core (1) of the filament, which has been
implanted in the skin through the full thickness of the dermis (7).
In this case the filament is shown in the state in which it would
be if it had been present in the skin only long enough for the
porous coating to soften and detach from the solid core, but not
long enough for the epidermis (8) to grown down the outside of the
filament.
[0032] FIG. 5b depicts the implant site after the filament core has
been removed by pulling out the semi-rigid backing to which it was
attached as shown in FIG. 5a. In this case, pulling out the
semi-rigid backing and core has resulted in separation of the cell
laden porous sheath (2) from the solid core. Sufficient time has
elapsed that the epidermis (8) has grown over the implant site, the
porous bioabsorbable coating has resorbed, and the implanted
cultured cells (6) have survived and are functioning properly.
[0033] FIG. 6 is a schematic representation of filaments comprised
of a solid core (1) and a porous coating (2) that are bonded
together. The process that is utilized to create the bonds between
the filaments, for example by heating and cooling, preferably is
the same process that is used to create porosity in the coating
[0034] FIG. 7 is a scanning electron micrograph (SEM) of the device
described in Example 1, at a scale of 1 mm.
[0035] FIG. 8 is an SEM of the device described in Example 1,
viewing the wires on end showing the exposed tips of the wires and
the surrounding coatings of porous, bioabsorbable polymer, at a
scale of 100 .mu.m.
[0036] FIG. 9 is an SEM of the end of a single wire of the device
described in Example 1, showing the morphology of the porous
coating, at a scale of 20 .mu.m.
DETAILED DESCRIPTION OF THE INVENTION
[0037] The present invention provides filamentary means for
delivery of various agents into a living host, a means comprising a
filament comprising a solid core and a bioabsorbable porous sheath.
When the solid core is made of bioabsorbable material, it is
preferably material selected from the group consisting of glass,
ceramic, and polymeric material. When the solid core is made of a
biocompatable material, it is preferably material selected from the
group consisting of metals or alloys containing the elements of
iron, nickel, aluminum, chromium, cobalt, titanium, vanadium,
molybdenum, gold, and platinum. The core of the filamentary means
is preferably made of bioabsorbable material when the filamentary
means is to be used as or as part of an implant to be permanently
implanted into the body of a living host. The core of the
filamentary means is preferably made of biocompatable material when
the filamentary means is to be used in the transdermal delivery of
an agent. The bioabsorbable nature of the material of the core and
sheath of the preferred permanent implant devices of the present
invention enable the living host into which they are implanted to
absorb the implant over time.
[0038] The bioabsorbable porous sheath is preferably comprised of a
bioabsorbable polymer, more preferably a bioabsorbable polymer
selected from the group consisting of poly(lactic acid),
poly(glycolic acid), poly(trimethylene carbonate), poly(amino
acid)s, tyrosine-derived poly(carbonate)s, poly(carbonate)s,
poly(caprolactone), poly(para-dioxanone), poly(ester)s,
poly(ester-amide)s, poly(anhydride)s, poly(ortho ester)s, collagen,
gelatin, serum albumin, proteins, carbohydrates, poly(ethylene
glycol)s, poly(propylene glycol)s, poly(acrylate ester)s,
poly(methacrylate ester)s, poly(vinyl alcohol), and copolymers,
blends and mixtures of said polymers.
[0039] A particularly preferred bioabsorbable polymer for use as a
bioabsorbable porous sheath coating on the solid core is
poly(lactic acid) or any of the various known copolymers of lactic
and glycolic acids such as a copolymer of L-lactide with dl-lactide
known as poly(L/DL-lactide). Such bioabsorbable polymers have a
long history of safe clinical use in the form of synthetic
absorbable suture materials and have been utilized successfully in
a number tissue engineering research experiments. Moreover, these
polymers are thermoplastic and soluble in a variety of organic
solvents enabling their use in coating wires by known extrusion and
solution based processes.
[0040] An advantageous feature of the filamentary means of the
present invention is the porosity of the bioabsorbable porous
sheath. Here again the application of proven technology can be
beneficial in achieving the desired pore size and void volume of
the porous sheath. A preferred method for creating porosity in the
bioabsorbable polymer coating involves the use of "blowing agents".
These are chemical additives that decompose at known temperatures
with the liberation of gases that cause foaming in the molten
polymer and porosity in the resultant cooled material. A number of
useful blowing agents are commercially available under the trade
name of Celogen.TM. (Uniroyal Chemical Co.). One example of a
traditional blowing agent is azodicarbonamide. Another blowing
agent that may be especially useful in the present invention due to
its compatibility with bioabsorbable polymers is urea dicarboxylic
acid anhydride, described in U.S. Pat. No. 4,104,195, the teachings
of which are incorporated herein. The use of blowing agents can
produce both open cell and closed cell foams. In the present
invention open cells are desired and closed cells are to be
avoided. Thus the conditions used in the manufacture of the porous
coating are preferably optimized to achieve an open cell structure
known as "reticulated" foam.
[0041] The filamentary means of the present invention can be
designed to deliver a variety of different agents, depending upon
the porosity and composition of the porous sheath. The agent
delivered with the filamentary means of the present invention is
preferably selected from the group consisting of: cells, growth
factors, drugs, recombinant molecules, cell recognition factors,
cell binding site molecules, cell attachment molecules, cell
adhesion molecules, proteins, glycoproteins, carbohydrates,
naturally occurring polymers, synthetic polymers, semi-synthetic
polymers, and recombinant polymers.
[0042] The porous sheath of the filamentary means is designed to
deliver the agent into a living host when the agent is coated on
the outer surface of the sheath, or mixed, dissolved, or imbedded
within the porous sheath. The porous sheath preferably defines
pores which are substantially interconnected and large enough to
admit the agent. The pores of the porous sheath are preferably open
pores produced using blowing agents, as described below. The pores
are preferably large enough to admit molecules ranging in molecular
weight from about 100 to about 3,000,000 Daltons, more preferably
ranging from about 500 to about 100,000 Daltons. Alternatively, the
porous sheath preferably defines pores which range in size from
about 0.1 micrometers to about 500 micrometers, more preferably
which range in size from about 10 to 200 micrometers.
[0043] The extent to which the porous sheath coats the core of the
filamentary means varies according to the application in which the
filamentary means is to be used. For example, when only one end of
a filament is to be combined with an agent before being used to
implant the agent into a living host by puncture the skin of the
host, only that end of the filament need include the porous sheath.
In contrast, when an entire filament is to be used to deliver an
agent to a host, such as happens when the entire filament is
implanted into the host, the entire length of the core of the
filament is preferably coated with the porous sheath.
[0044] A discussion of more specific preferred features of the
filamentary means of the present invention, as used in additional
embodiments of the present invention follows. It is contemplated
that additional advantages and features of the present invention
will become evident to one of ordinary skill in the art of the
present invention upon review of the present disclosure.
[0045] Hair Follicle Regeneration.
[0046] One of the embodiments of the present invention provides
materials and methods for a tissue engineering approach to hair
follicle regeneration. Tissue engineering is generally defined as
the technology of restoring defective or missing tissues or organs
by the implantation of living cells that have been cultured and
multiplied outside the body. A more detailed description of the
philosophy and techniques of tissue engineering has been published
by C. W. Patrick Jr., A. G. Mikos and L V. McIntire, eds.,
Frontiers in Tissue Engineering, Elsevier Science, Inc., New York,
1998, the teachings of which are incorporated herein.
[0047] In a preferred embodiment of the present invention, cells
harvested from a few hair follicles are multiplied in vitro by
tissue culture techniques and re-implanted into bald skin, thereby
generating hundreds of hairs from each hair that is harvested to
seed the tissue cultures. A remarkable feature of the present
invention is the means by which the appropriate cells are
introduced into the skin and the unique ability of the implants to
facilitate regeneration of the cellular architecture of normal hair
follicles.
[0048] The hair follicle cell implant device of the present
invention is comprised of three preferred parts: (1) a fine
stainless steel or other suitably biocompatible wire or stiff fiber
that is capable of easily penetrating the skin; (2) a porous
coating on said wire comprised of a bioabsorbable polymer that is
suitable as a support for cell attachment and growth; and (3) a
means for the semi-rigid backing of multiple coated wires in an
array to facilitate the implantation of said multitude of wires
into the skin and their subsequent removal at an appropriate time
post-implantation. The stainless steel wire is the core, and the
porous coating the porous sheath of this particular embodiment of a
filament of the present invention. The wire and filament produced
therefrom have a first end and a second end.
[0049] The porous bioabsorbable coating on the wire can be selected
from a variety of known polymers and the process of applying the
coating and forming the porous structure can be selected from a
variety of known processes. Similarly, the degree of porosity, the
thickness of the coating, and the diameter of the wire can be
varied as desired to obtain the optimum performance of the implant
and the most efficient neogenesis of hair follicles. In general,
the wire diameter will be similar to the diameter of the hair that
is to be regenerated for each individual patient. The thickness of
the coating will be equivalent to the sum of the various cellular
layers comprising the hair follicle that surround a normal hair
shaft. The preferred coating will not cover the entire length of
the wire. Instead, the coating will begin at a position distal to
the first end of the wire, depending on the desired depth at which
the cells are to be delivered from that end of the wire.
[0050] The first end of the filament is preferably sharp to
facilitate entry into the skin of the living host. The sharp shape
of the first end can be produced by cutting the first end of the
wire off at an angle after the wire is coated with the porous
bioabsorbable polymer. However, it is more preferably produced by
cutting the first end of the wire at an angle prior to coating the
first end with the porous bioabsorbable polymer. The coating
preferably does not cover the most distal end of the first end of
the wire, in order to allow first end of the wire to enter the skin
of a living host using the lowest possible injection force.
[0051] A preferred wire for use as the core of the filamentary
means of hair follicle cell implant device of the present invention
is 316L stainless steel. This particular metal alloy has been
widely used clinically in the form of surgical skin staples. A
typical diameter of wire for use in this invention that is similar
to the diameter of human hair is about 3 to 5 thousandths of an
inch. Although such a fine wire might seem too flexible for use in
penetration of the skin, the depth of penetration needed is shallow
enough to permit the implant to have a relatively low aspect ratio
(length divided by diameter) such that bending of the wire is
unlikely to occur. In addition, penetration of the skin by such a
fine wire sharpened by cutting the end off at an angle will be
relatively atraumatic. As an aid to penetration and patient
comfort, the skin can first be anesthetized and softened by the
application of an analgesic lotion and covered with an occlusive
dressing for about an hour prior to implantation of the wires.
[0052] A novel method of creating the porous sheath on the wire
core to create the filaments used to make the device of the present
invention is to select a wire core that can be heated electrically,
such as nickel-chromium alloy wire. The wire core is then coated
with a mixture of polymer and blowing agent below the decomposition
temperature of the blowing agent. The porous coating is then formed
by connecting the wire to an electrical current to obtain the
precise rate of heating, duration of heating time, and ultimate
temperature to produce the desired effect. Conducting this
operation under the flow of an inert atmosphere of nitrogen or
argon, or submerged in oil, is beneficial in protecting the polymer
from oxidation and providing rapid cooling and solidification of
the highly porous structure created at the instant of blowing agent
decomposition.
[0053] Upon obtaining a plurality of fibers, each comprising a
desired wire coated with a bioabsorbable porous sheath, the fibers
are imbedded in a semi-rigid backing as follows. The first end of
each fiber is placed in a mold. The mold is comprised of a block of
any suitable material, such as Teflon.TM., with defining holes in a
surface of the block that are just sufficiently large in diameter
to accommodate the coated wires, and of a depth that corresponds to
at least the desired depth that the first end of each fiber is to
penetrate the skin when the hair follicle implant device is used to
implant hair follicle cells into the skin of a living host. The
spacing between the holes preferably corresponds to the spacing
between hair follicles in the normal scalp. When the first end of
each fiber is placed in the mold, the second end of each fiber
protrudes from the surface of the mold. Once the plurality of
fibers has been placed into the mold, a layer of silicone resin or
other suitable liquid pre-polymer is then coated over the
protruding second end of each filament and cured. The resulting
implant device is preferably removed from the mold by placing a
layer of adhesive tape with a backing that is puncture resistant
over the cured resin, and then removing the tape therefrom. Removal
of the tape pulls out the wires from the mold to yield the finished
implant device (see FIG. 2). The implant device is preferably
packaged in an appropriate container for protection of the delicate
wires until use, and sterilized by ethylene oxide or other suitable
means prior to use.
[0054] In order to use the above hair follicle cell implant device
to regenerate hair follicles, a suspension of follicle progenitor
cells is obtained. These cells can be harvested from some of the
patient's normal follicles. Alternatively, progenitor cells can be
obtained from the follicles of living donors or recently deceased
organ donors. The finding that follicle progenitor cells were not
rejected by an unrelated human recipient has been published by A.
J. Reynolds, C. Lawrence, P. R. Caerhalmi-Friedman, A. M.
Christiano, and C. A. B. Jahoda, Nature 402: 33-34, Nov. 4, 1999,
the teachings of which are incorporated herein.
[0055] Cells multiplied in a growth medium are loaded into the
array of coated wires by seeding the porous sheath of the first end
of each filament with the cells, preferably by wicking the growth
medium containing the cells into the porous coatings. The cells
optionally can be further multiplied by continuing the tissue
culture process after seeding the porous sheath of each filament
with the cells, to ensure that cell attachment and spreading within
the porous matrix has occurred. The first end of each filament is
then implanted into the dermis by pressing the seeded implantation
device onto the skin, preferably after softening and anesthetizing
the skin with the use of an analgesic lotion under an occlusive
dressing such as Tegaderm.TM. (3M Company). After several days the
bioabsorbable coating separates from the wire. The wires and
semi-rigid backing can then be removed by pulling off the tape to
which they are attached, thereby leaving the porous bioabsorbable
matrix and attached follicle cells in the dermis. New hair
follicles are generated in the implant sites as the transplanted
cells multiply and sort themselves into the appropriate functional
layers under the influence of the follicular stem cells carried
through from the original donor follicles. Each new hair follicle
will then grow a hair shaft in the space that was formerly occupied
by the wire. The hair will have the same color and consistency as
the donor hair that was used to create the cell culture. The hair
follicle cell donor is preferably the living host, and the hair
regenerated thereby has the same color and consistency as that of
the host.
[0056] Gene Therapy and Encapsulated Cell Delivery.
[0057] In a related embodiment of the present invention, the cells
that are obtained from hair follicles of a living host can be
genetically modified to express gene products that benefit the
living host when implanted therein. Because the hair follicle cells
are rapidly multiplying and renewing themselves as hair grows, the
genetically modified cells implanted as described above will serve
as a permanent and continuous source of needed substances. An
example of such a substance is factor IX which would provide a cure
for hemophilia B. In this case, new hair growth may not be needed
on the scalp and instead could be established on other parts of the
body such as on the back or the legs. The follicles harvested to
produce the genetically engineered cultured cells can be taken from
the same skin in which the new hair will be created. Thus the
cosmetic effect of the presence of this superfluous new hair growth
will be insignificant.
[0058] In another embodiment, cells that do not produce hair such
as dermal fibroblasts can be similarly implanted in the skin. These
cells would be suitable for achieving a temporary therapeutic
effect. For example, bed sores, also known as decubitus ulcers, are
a significant cause of patient discomfort, infection risk, and
health care cost in nursing homes. Another major medical problem is
non-healing skin ulcers primarily found on the lower extremities of
patients with poor circulation due to disease such as diabetes. It
is well known that growth factors such as platelet derived growth
factors are capable of facilitating rapid wound healing but cannot
heretofore be conveniently administered to ulcers that are exuding
fluid. In this embodiment of the present invention, fibroblasts or
other suitable cells are genetically modified to express the
desired growth factors and are implanted into the ulcer, thereby
stimulating tissue regeneration and healing the ulcers.
[0059] Other disorders and diseases of the skin that can be treated
with similar embodiments include lamellar ichthyosis, a disfiguring
skin disease characterized by abnormal epidermal differentiation
and defective cutaneous barrier function. This skin disorder is
caused by the deficiency of an enzyme known as keratinocyte
transglutaminasel (Tgasel), the replacement of which is a potential
future approach to therapeutic gene delivery in human skin. Thus
dermal keratinocytes can be genetically engineered to express the
needed enzyme and implanted into the skin by the methods of the
present invention.
[0060] In another embodiment, cells that have a very slow rate of
division but provide an essential function can be transplanted from
one part of the body of a donor into the skin of a living host.
Once transplanted, the cells will benefit from the high vascularity
of the surrounding tissue. An important example is the
transplantation of pancreatic islet cells as a treatment for
diabetes. When the donor and host are not the same individual, as
is the case when pancreatic islet cells are transplanted into a
living host suffering from diabetes, the cells must typically be
immunoprotected by encapsulation prior to transplantation.
Encapsulation prevents the patient's antibodies from destroying the
foreign cells, while allowing lower molecular weight substances
including insulin and glucose to diffuse in and out of the capsules
containing the donor cells.
[0061] A serious deficiency of methods of the prior art of
introducing such encapsulated cells into the patient is the
difficulty of both delivering a large number of cells and providing
a high surface area implant to ensure good exchange with the blood
supply. Thus, encapsulated cells of the prior art have been
implanted in a manner that resulted in an inadequate survival rate
and an insufficient output of insulin to cure diabetes. The present
invention solves these problems by providing a more effective means
for the delivery of encapsulated cells. Thus a multitude of small
implants each comprising only a few layers of encapsulated cells
delivered by the methods of the present invention ensures that the
donor cells receive optimal nutrition from the vasculature of the
dermis and provide an efficacious, glucose responsive release of
insulin into the blood stream.
[0062] Bone Regeneration.
[0063] In another embodiment of the present invention, fibers of
the present invention are fused together in a three dimensional
structure which provides a highly porous matrix for bone
regeneration (see FIG. 6). In addition to the porosity created by
the spaces between the fibers which is beneficial for bone
ingrowth, the high surface area of the porous coating on the fibers
facilitates osteoblast attachment. This allows the option of
seeding the material with osteoblasts to provide a tissue
engineered implant. In this case the porous coating is preferably
selected from polycarbonates such as poly(trimethylene carbonate)
and tyrosine-desaminotyrosine derived polycarbonates due to their
excellent compatibility with new bone and the absence of acidic
degradation products that may contribute to bone resorption or
inflammation late in the bioabsorption process. The core fiber is
preferably a biocompatible, osteoconductive ceramic or glass such
as those known as "bioglass". The fiber may also be selected from a
number of slowly dissolvable or bioabsorbable glasses such as
calcium metaphosphate glasses.
[0064] The process for making the bone regeneration matrix involves
providing an osteoconductive ceramic or glass fiber and coating
said fiber with a mixture of polymer and blowing agent. The coated
fibers are then cut into short lengths and formed into a nonwoven
web by any of several known methods. The web is then formed into
the desired shape and heated at a temperature that both melts and
fuses the coating on the fibers and decomposes the blowing agent to
yield a reticulated foam structure. The solid inorganic fibers are
unaffected by this process other than becoming glued together to
form a rigid structure. The device can then be sterilized, seeded
with cells, and stored in a frozen state until needed for
implantation to regenerate bone. The surgeon can then sculpt the
material just prior to implantation so that it fits into the bone
defect. If the material is to be used to regenerate bone within a
spinal fusion device, such as an interbody fusion "cage", the
matrix can be pre-formed to fit exactly the dimensions of the
cage.
[0065] Trans-Dermal Drug Delivery.
[0066] Another embodiment of the present invention is a
trans-dermal drug delivery device, and a method of using the
device. Many drugs could benefit from trans-dermal delivery but
lack the properties that are required for penetration of the skin.
The present invention overcomes this problem by providing a
physical path through the stratum corneum and into the dermis.
[0067] The trans-dermal drug delivery device of the present
invention comprises a semi-solid backing with a plurality of
filaments fixed therein, wherein each filament comprises a wire
core coated by a porous polymer sheath in which the drug is soluble
and permeable. Each filament has a first end and a second end. The
second end of each filament is fixed in the semi-solid backing,
such that the first end of each filament protrudes from one surface
of the semi-solid backing. The semi-solid backing further comprises
a drug reservoir which is in contact with the second end of each
filament.
[0068] When the trans-dermal drug delivery device of the present
invention is applied to the skin of a living host, the first end of
each filament penetrates the outermost barrier layer of the skin
and allow the drug to diffuse slowly through the porous sheath of
each filament into the blood stream of the living host.
[0069] The trans-dermal drug delivery device of the present
invention is preferably made according to a method similar to the
method described above for producing the hair follicle cell
implantation device of the present invention, disclosed above. In
the present case, the second ends of each of the plurality of
filaments are set in holes in a release liner film corresponding to
mold cavity holes that are not as deep as those used to make the
hair follicle cell implantation device. The polymer resin that is
used to cover the protruding wire ends is a pressure sensitive
adhesive with drug blended in, and the puncture resistant backing
has adequate moisture vapor transmission for long term coverage of
the skin. The device is then sterilized and packaged. To use the
device the patient simply separates the protective release liner
from the backing, thereby exposing the coated wires and
drug/adhesive surface, and applies this to the skin in the same
manner as with other trans-dermal drug delivery patches.
[0070] Alternatively, when the drug to be delivered with the
trans-dermal drug delivery device of the present invention has a
very low solubility in the polymer used to make the porous sheath
of the filaments, the drug can be mixed with the coating polymer as
a suspension prior to formation of the porous sheath. In this case
a slow release of the drug is provided directly to the dermis from
the drug loaded coating and from there into the blood stream.
Suitable coating polymers for use in the drug delivery application
include bioabsorbable hydrogels that have porosity on a molecular
scale.
EXAMPLE 1
Porous Coated Wires for Implantation of Follicle Progenitor
Cells
[0071] An array of 21 wires, 0.0035 inches in diameter
(nickel-chromium alloy, California Fine Wire Co., Grover Beach,
Calif. 93433), was made by imbedding the wires in epoxy resin
contained in the cut-off end of a tuberculin syringe. The wires
were first placed in a 2 mm thick disc with 0.0063 inch diameter
holes arranged in a pattern of one surrounded by 7 surrounded by
13. The wires were pushed into the disc until flush with the
surface. The opposite surface had various lengths of wire
protruding. This surface was placed in contact with the liquid
epoxy resin mixture such that the protruding wires became imbedded.
The surface of the disc in contact with the epoxy was first coated
with a thin layer of petrolatum to prevent adhesion. Upon curing of
the epoxy resin, the disc was pulled off to expose 21 wires
extending exactly 2 mm from the surface of the 4.5 mm diameter plug
of epoxy resin.
[0072] A mixture of poly(dl-lactide-co-50%-glycolide) (Resomer.TM.
RG504, Boehringer Ingelheim, D-55216 Ingelheim am Rhein, Germany)
and 5% by weight of azodicarbonamide (Aldrich Chemical Co.,
Milwaukee, Wis. 53201) was melt blended by stirring in a test tube
immersed in an oil bath maintained at a temperature of 180.degree.
C. A small amount of this mixture was placed in the bottom of a 50
ml beaker and re-heated to give a viscous liquid. The above epoxy
resin plug was inverted and the wires dipped into the molten
polymer mixture to a depth of about 0.3 mm and quickly removed.
This produced a thin coating of polymer mixture on the tips of the
wires and fine filaments pulled away from the melt and attached to
the tips.
[0073] Crystals of sodium chloride (Morton Popcom Salt) were placed
in an electric coffee bean grinder and milled into a fine powder. A
1/2 inch diameter hex bolt was placed on end and a nut threaded
onto the bolt just far enough to engage the threads. The cavity
formed by the nut and bolt was filled with powdered salt. A
thermometer was lowered into the salt and clamped in a vertical
position with clamps on a ring stand. The surface of the salt was
smoothed out with a spatula. The bolt was heated with a propane
torch until the temperature of the salt reached 240.degree. C. The
polymer-coated wires were then dipped into the hot salt, pushed
about half way in and then quickly pulled out. The adherent salt
was removed by dipping the wires in water until the salt dissolved.
The water was removed from the device by gently blotting with
tissue paper. The device was placed back in a tuberculin syringe
barrel for protection and stored in a desiccator. Scanning electron
micrographs of device are shown in FIGS. 7-9.
EXAMPLE 2
Use of the Device of Example 1 to Produce New Hair Follicles
[0074] The device of Example 1 is soaked in ethanol for 5 minutes
and then rinsed with sterile water. The excess water is removed
from the porous structure by blotting with a sterile, lint-fee
surgical sponge. This process serves both to sterilize the polymer
and to improve the ability of cells to be wicked rapidly and
completely into the porous polymer.
[0075] Human dermal papilla cells that have been multiplied in
culture are collected and resuspended in an isotonic buffer
solution at approximately ten million cells per cubic centimeter.
The pre-wet implant is then dipped into the suspension of cells and
immediately injected into human skin where the growth of hair is
desired.
[0076] Prior to implantation, the skin is wiped with gauze soaked
in 70% isopropanol and then wiped with gauze soaked in
Betadine.TM.. Lidocaine cream is then applied to the skin and
covered with a Tegaderm.TM. dressing for a minimum of one hour.
This pre-implantation procedure serves to kill bacteria and to
soften and anesthetize the skin. After implanting the device, the
exposed epoxy resin plug is covered with a dressing to prevent it
from being disturbed or dislodged.
[0077] Approximately 48 hours after implantation, the dressing is
removed. The wires are then removed from the skin by pulling on the
epoxy resin plug. The cell-laden porous bioabsorbable polymer tips
remain under the skin, having separated from the wires as a result
of tissue attachment to the porous polymer and moisture induced
loosening of the polymer attachment to the metal.
[0078] During the next period of several weeks the implanted cells
multiply and organize into a new hair follicle as the bioabsorbable
polymer degrades and is bioabsorbed. The growth of new hair
indicates that the restoration process is complete.
EXAMPLE 3
Porous Scaffold for Tissue-Engineered Bone
[0079] Poly(70%-L-lactide-co-30%-d,l-lactide) obtained from Purac
Biochem, b.v. (Gorinchem, Holland) is melt blended at about
170.degree. C. with 5% by weight azodicarbonamide (Aldrich Chemical
Co.) and pelletized. A proprietary bioabsorbable glass fiber
produced by MO-SCI Corp. (Twitty Industrial Park, Rolla, Mo. 65401)
is obtained as a monofilament single strand that is 100 microns in
diameter.
[0080] A cladding extrusion die is made such that the 100 micron
diameter fiber can pass through the die while polymer is extruded
to cover and clad the moving fiber. The polymer/azodicarbonamide
blend is extruded as a cladding on the glass to give a
cross-sectional area ratio of 2:1 core to sheath.
[0081] The fiber is cut into 3 to 5 millimeter lengths and added to
a beaker of water with stirring. The resultant slurry is then
poured onto a Buchner funnel equipped with a coarse glass frit and
the water allowed to drain. This produces a "wet-laid" non-woven
web of fibers. The web is dried under vacuum and carefully
transferred into a wire basket. The basket is lowered into a beaker
of peanut oil heated to 240.degree. C. for about one second and
then immersed in a beaker of hexane. The hot oil causes the polymer
to melt and the azodicarbonamide to decompose into gas, thereby
converting the polymer into an open-cell foam. The cool hexane
causes the polymer to solidify, thereby preserving the porous
structure and adhering the glass fibers together at every point
that they touch. The hexane also dissolves and removes the oil from
the structure without affecting the polymer.
[0082] Chondrocytes are seeded onto the structure from an aqueous
suspension causing the cells to wick into the porous polymer
coating on the glass fibers. The structure can then be implanted in
a bone defect immediately or allowed to mature in culture prior to
implantation. In either case the cells will be retained in the
microporous structure of the coating while the macroporous
structure of the adhered fibers will allow ample room for Lissue
ingrowth and osteoinduction of new bone due to the seeded
cells.
[0083] While the present invention has now been described with some
detail and specificity, those skilled in the art will appreciate
the various modifications, including variations, additions, and
omissions, that may be made in what has been described.
Accordingly, it is intended that the scope of the present invention
be limited solely by the broadest interpretation that lawfully can
be accorded the appended claims.
* * * * *