U.S. patent application number 11/255922 was filed with the patent office on 2006-02-23 for suturable adhesion-preventing membrane.
Invention is credited to Kazuhisa Matsuda.
Application Number | 20060041320 11/255922 |
Document ID | / |
Family ID | 26348255 |
Filed Date | 2006-02-23 |
United States Patent
Application |
20060041320 |
Kind Code |
A1 |
Matsuda; Kazuhisa |
February 23, 2006 |
Suturable adhesion-preventing membrane
Abstract
A suturable adhesion-preventing membrane has high suture
strength, good biocompatibility, decomposition and absorption in a
living body, sufficient adhesion-preventing effect, and desirable
guided tissue regeneration. The membrane is composed of at least
one non-woven fabric layer made of collagen fibers, or a laminated
membranous substance consisting of at least one non-woven fabric
layer made of collagen fibers and at least one sponge layer made of
collagen, and a coating layer of gelatin or hyaluronic acid on the
surface or surfaces of the above membrane. Preferably, the membrane
comprises one to six compressed cross-linked collagen non-woven
fabric layers wherein a layer has a fibers having a fiber diameter
of 0.05 mm to 1.0 mm, a bulk density of 5.0.times.10.sup.-4 to 5
g/cm.sup.3 and a thickness of 0.1 mm to 50 mm, and a coating layer
containing gelatin or hyaluronic acid and having a thickness of
0.05 mm to 20 mm, wherein the coating layer covers one or both
sides or a part or whole of the surface of the membrane.
Inventors: |
Matsuda; Kazuhisa;
(Osaka-shi, JP) |
Correspondence
Address: |
KUBOVCIK & KUBOVCIK
SUITE 710
900 17TH STREET NW
WASHINGTON
DC
20006
US
|
Family ID: |
26348255 |
Appl. No.: |
11/255922 |
Filed: |
October 24, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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09489473 |
Jan 21, 2000 |
6977231 |
|
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11255922 |
Oct 24, 2005 |
|
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Current U.S.
Class: |
623/23.76 ;
435/397; 435/399 |
Current CPC
Class: |
B32B 5/022 20130101;
Y10T 442/2525 20150401; Y10T 442/647 20150401; B32B 9/02 20130101;
A61L 15/325 20130101; A61L 31/10 20130101; A61L 31/044 20130101;
Y10T 442/652 20150401; C08L 5/08 20130101; B32B 27/12 20130101;
A61L 31/10 20130101; B32B 2262/08 20130101; Y10T 442/651 20150401;
B32B 9/047 20130101 |
Class at
Publication: |
623/023.76 ;
435/397; 435/399 |
International
Class: |
A61F 2/02 20060101
A61F002/02; C12N 5/08 20060101 C12N005/08 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 21, 1999 |
JP |
11-12625 |
Mar 29, 1999 |
JP |
11-85477 |
Claims
1. A suturable adhesion-preventing membrane for guided tissue
regeneration comprising: a compressed non-woven fabric layer
composed of cross-linked collagen fibers wherein the layer has
fibers having a fiber diameter of 20 to 100 .mu.m, a bulk density
of 1.0.times.10.sup.-3 to 2.0 g/cm.sup.3 and a thickness of 0.2 mm
to 1.0 mm; and a coating layer containing gelatin or hyaluronic
acid covering each surface of the compressed collagen non-woven
fabric layer; and wherein the membrane has a thickness of 0.5 mm to
2.0 mm.
2. A suturable adhesion-preventing membrane for guided tissue
regeneration comprising: a laminate of two or three compressed
non-woven fabric layers each composed of cross-linked collagen
fibers wherein each layer has fibers having a fiber diameter of 150
to 250 .mu.m, a bulk density of 0.05 to 2.0 g/cm.sup.3 and a
thickness of 0.5 mm to 2.0 mm; and a coating sponge layer
containing gelatin or hyaluronic acid covering each surface of the
laminate of non-woven fabric layers; and wherein the membrane has a
thickness of 1.0 mm to 4.0 mm and is heat cross-linked.
3. A suturable adhesion-preventing membrane for guided tissue
regeneration comprising a laminated membranous substance having at
least one non-woven fabric layer made of collagen fibers and at
least one sponge layer made of collagen, characterized in that a
surface of the laminated membranous substance is provided with at
least one layer containing gelatin or hyaluronic acid.
4. A suturable adhesion-preventing membrane according to claim 3,
wherein the coating layer containing gelatin or hyaluronic acid is
a sponge or film.
5. A suturable adhesion-preventing membrane according to claim 3,
wherein the coating layer containing gelatin or hyaluronic acid
comprises cross-linked gelatin or hyaluronic acid.
6. A suturable adhesion-preventing membrane according to claim 3,
wherein the layer containing gelatin or hyaluronic acid is formed
by lyophilization.
7. A suturable adhesion-preventing membrane according to claim 3,
wherein either the at least one non-woven fabric layer or at least
one sponge layer in the laminated membranous substance is
compressed, or the membranous substance is compressed.
8. A suturable adhesion-preventing membrane for guided tissue
regeneration according to claim 3, wherein the coating layer
containing gelatin or hyaluronic acid has a thickness of 0.05 mm to
20 mm.
9. A suturable adhesion-preventing membrane according to claim 3,
wherein the collagen of the collagen fibers-and the collagen of the
at least one sponge layer are independently selected from
enzyme-solubilized collagen, acid-solubilized collagen,
alkali-solubilized collagen or neutral solubilized collagen.
10. A suturable adhesion-preventing membrane according to claim 3,
wherein a part or all of the laminated membranous substance
comprising at least one non-woven fabric layer made of collagen
fibers and at least one sponge layer made of collagen comprises a
cross-linked collagen.
11. A suturable adhesion-preventing membrane according to claim 3,
wherein the at least one non-woven fabric layer made of collagen
fibers is a layer obtained by coagulating collagen fibers which are
extruded and crossed over in multiple folds, or extruded and wound
on a plate in a certain direction to have parallel lines of fibers,
and compressing the coagulated fibers.
12. A suturable adhesion-preventing membrane according to claim 3,
wherein the at least one non-woven fabric layer made of collagen
fibers is a layer in which the fibers are joined together using a
binder comprised of solubilized collagen solution.
13. A suturable adhesion-preventing membrane according to claim 3,
wherein the at least one non-woven fabric layer made of collagen
fibers has a thickness of 0.05 mm to 10 mm, the at least one sponge
layer made of collagen has a thickness of 0.05 mm to 20 mm and the
coating layer containing gelatin or hyaluronic acid has a thickness
of 0.05 mm to 20 mm.
14. A suturable adhesion-preventing membrane according to claim 3,
wherein one to six layers of the at least one non-woven fabric
layer made of collagen fibers are laminated with one to four layers
of the at least one sponge layer made of collagen, and further, one
to four layers of gelatin or hyaluronic acid layer are laminated
thereon, and as a whole, three to fourteen layers are
contained.
15. A suturable adhesion-preventing membrane according to claim 3,
wherein the at least one non-woven fabric layer made of collagen
fibers has fibers having a fiber diameter of 5 .mu.m to 1 mm and a
bulk density (fiber density) of 5.times.10.sup.-4 to 5
g/cm.sup.3.
16. A suturable adhesion-preventing membrane for guided tissue
regeneration according to claim 3, wherein the overall thickness of
the membrane is 0.1 mm to 50 mm.
17. A suturable adhesion-preventing membrane according to claim 3,
wherein the at least one sponge layer made of has a porosity area
of 10 to 90%.
18. A suturable adhesion-preventing membrane for guided tissue
regeneration, comprising: a laminated membranous substance that has
a first layer of a compressed collagen sponge layer, a second layer
of a chemically cross-linked and compressed collagen non-woven
fabric layer, and a third layer of a compressed collagen sponge
layer; and a coating layer containing gelatin or hyaluronic acid,
covering each surface of the laminated membranous substance.
19. A suturable adhesion-preventing membrane for guided tissue
regeneration comprising: a laminated membranous substance that has
a first layer and a second layer of a chemically cross-linked and
compressed collagen non-woven fabric; compressed collagen sponge
layers provided on both sides of the laminated membranous
substance; and a coating layer containing gelatin or hyaluronic
acid, covering each sponge layer.
Description
[0001] This application is a division of application Ser. No.
09/489,473 filed Jan. 21, 2005, which claims priority of Japanese
patent application Nos. 11-12625 filed Jan. 21, 1999, and 11-85477
filed Mar. 29, 2005, which are incorporated herein by
reference.
FIELD OF THE INVENTION
[0002] This invention relates to a suturable adhesion-preventing
membrane, and more particularly to a suturable adhesion-preventing
membrane based on collagen and used for guided tissue regeneration.
Even more particularly, the invention relates to a membrane that is
utilized in a living body as an adhesion-preventing membrane for a
prosthesis; to repair, augment or replace parts of tissues and
organs that have been destroyed or weakened by disease or trauma or
surgical operation such as abdominal wall defects or excised,
transected, ablated or resected sites in tissues within a living
body such as the pleura, pericardium, cerebral dura mater and
chorion, and various organs. The membrane of the present invention
is characterized by, in particular, being suturable, having good
biocompatibility, and further, promoting tissue regeneration
BACKGROUND OF THE INVENTION
[0003] In various surgical operations, an ablation of affected
parts, a repair of damaged sites and surfaces or the like is very
often conducted. Especially, in the surgical operations for various
organs such as the lungs, heart, liver, brain, digestive organs and
gallbladder, unless the resected site or defective part of the
organs or the like is replaced or repaired or augmented (i.e.,
compensated) with a membranous substance covering the tissue of
such organs, the fundamental functions of the organ will be damaged
in many cases. If the treatment is not completely performed, the
patient will die due to a malfunction of the organ or, even if the
patient passes the crisis, an often observed tendency is that the
prognosis is quite bad. Also, with respect to an insufficient
suture fixation of the membranous substance in a prosthetic or
compensated part, even if the function of the treated organ itself
manages to be maintained, body fluids, digestive juices or contents
which are exuded or leak from the organ may cause infection, or
cause an attack or an erosion of other organs to eventually
jeopardize life.
[0004] Further, there happens highly frequently an adhesion of the
membranous substance at these prosthetic or compensated parts, and
consequently, a malfunction of the organ may be induced in the
course of time. In order to solve such problems, membranous
substances or adhesion-preventing membranes made of various
materials have been developed to cover the organ or the tissue of
the organ.
[0005] Conventionally, a surgical wound dressing material is known
in which a non-woven fabric layer made of collagen fibers is
treated with aldehydes to have water resistance and the fibers are
bonded mutually with collagen (Japanese Unexamined Patent
Publication No. 141190/1975). However, because the surface of the
dressing material is treated with a cross-linking agent, the
material has inferior biocompatibility or is inferior in guiding
tissue regeneration. Further, it is uncertain whether the dressing
material can function to have sufficient suture strength or prevent
an adhesion of a wound although it covers the wound.
[0006] In the above conventional technique, the adhesion-preventing
membrane exhibits insufficient adhesion-preventing effects, suture
strength, biocompatibility and decomposition and absorption
capability in a living body, and particularly, the membrane can not
simultaneously exhibit these characteristics. Therefore, the aim of
the present invention is to resolve simultaneously the conventional
problems of adhesion-preventing membranes that include insufficient
suture strength, insufficient biocompatibility or decomposition and
absorption capability in a living body, and insufficient
adhesion-preventing effects as well.
[0007] The present inventor has already proposed as an improved
medical membrane utilizing only animal collagen, a medical collagen
membrane of non-woven fabric layer which comprises cross-linked
collagen in which at least one surface of a membrane is covered
with a-collagen coating (Japanese Patent Application No.
264891/1998). Because the surface of the membrane is not
cross-linked with a cross-linking agent, the membrane is superior
in biocompatibility, guiding tissue regeneration and the like as
compared to a surgical wound dressing material in which a non-woven
fabric layer made of collagen fibers is treated with aldehydes to
have water resistance and the fibers are bonded mutually with
collagen (Japanese Unexamined Patent Publication No.141190/1975).
Also, another characteristic of the membrane is to have a wide
variety of applications for surgical procedures as in,
particularly, compensation or prothesis of various organs, since
the membrane can be fixed directly to the organs by means of a
suture. Additionally, the membrane especially has strength enough
to withstand suture fixation compared to a patch for visceral
surgery which is comprised of two layers of (1) porous fibrous
collagen layer and (2) collagen and/or a gelatin membrane (Japanese
Patent No. 2775115). Therefore, it is possible for the membrane to
be fixed more firmly to application sites with a general and
inexpensive surgical suture thread as compared to fixation with
only a biological adhesive, and a wide range of surgical
applications are characteristically provided.
[0008] However, the above improved membrane has a difficulty in
obtaining a sufficient adhesion-preventing property because the raw
material of the membrane is collagen derived from an animal, which
promotes adhesion, proliferation and extension of cells. Therefore,
it is an object of the present invention to provide a suturable and
adhesion-preventing membrane for guided tissue regeneration which
is superior in suture strength, biocompatibility and guiding tissue
regeneration, and further has an adhesion-preventing property.
SUMMARY OF THE INVENTION
[0009] As a result of intensive research to solve such problems,
the present inventor has found that when at least one non-woven
fabric layer made of collagen fibers is used to form a membrane, or
a non-woven fabric layer made of collagen fibers and a sponge layer
made of collagen are used to form a membranous substance having a
laminated structure, and a coating layer containing gelatin or
hyaluronic acid is provided on the surface of the membrane or the
membranous substance, a desired membrane is formed that has
sufficient suture strength, good biocompatibility, a property for
promoting tissue regeneration and a sufficient adhesion-preventing
effect, thus completing the present invention.
[0010] The present invention is directed to a suturable
adhesion-preventing membrane for guided tissue regeneration
comprising a membrane having at least one non-woven fabric layer
made of collagen fibers, or a laminated membranous substance having
at least one non-woven fabric layer made of collagen fibers and at
least one sponge layer made of collagen, characterized in that at
least one surface of the membrane or laminated membranous substance
is provided with at least one coating layer containing gelatin or
hyaluronic acid.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIGS. 1 to 4 are flow charts illustrating the processes
described in Examples 1, 2, 6 and 7, respectively, for preparing
suturable adhesion-preventing membranes of the present
invention.
DETAILED DESCRIPTION
[0012] Now, the most simple and effective way to prevent adhesion
is to avoid contact between tissues damaged by injury or deficit
and other tissues that have possibility of physically contacting
the damaged tissue by means of barrier. However, a barrier made of
synthetic fibers and the like causes various disadvantages such as
excessive calcification, xenobiotic reaction, an inflammatory
response and the like because of insufficient biocompatibility.
Accordingly, the barrier material itself should not mediate the
adhesion of damaged or defective tissues to other tissues
corresponding thereto. Hyaluronic acid, gelatin and the like are
enumerated as materials that satisfy such a requirement. Both
hyaluronic acid and gelatin are capable of being treated as viscous
aqueous solutions and utilized as a gel by various processing
methods.
[0013] As these materials are extracted and purified from mainly
the living body of an animal or the like, their good
biocompatibility has already allowed them to be put to practical
use in medical drugs and other various medical fields. Further,
when the materials are implanted in a living body, gelatin or
hyaluronic acid molecules are continuously released during
decomposition and absorption processes, to exert viscosity and
maintain the hydrophilic property. As a result, even if the
materials are in contact with parts of the damaged or deficient
tissues, they also have a characteristic to make it difficult to
cause physically binding or adhesion.
[0014] Exemplified as techniques to produce, by applying these
characteristics, an adhesion-preventing membrane, medical material
or the like utilizing hyaluronic acid are ones disclosed in
Japanese Unexamined Patent Publication Nos.73103/1994 and Japanese
Examined Patent Publication No. 30124/1995, Japanese Registered
Patent No. 2670996, Japanese Unexamined Patent Publication Nos.
333402/1986 and 234864/1986, Japanese Registered Patent No.
2648308, Japanese Unexamined Patent Publication Nos. 157378/1996,
296005/1997, 102002/1995, and 509386/1995 and the like. However, a
technique to provide not only an adhesion-preventing effect but
also induction of tissue regeneration and mechanical strength
sufficient to withstand suturing can not be found in the disclosed
techniques, nor in other existing techniques.
[0015] Examples of techniques that utilize gelatin with the
expectation of an adhesion-preventing effect, as in the case where
hyaluronic acid is used, include ones disclosed in Japanese
Unexamined Patent Publication Nos. 103479/1997 and 52204/1996.
However, similar to the technique using hyaluronic acid, neither of
the techniques disclosed in these publications has succeeded in
providing a medical material that can concurrently satisfy the
three requirements consisting of adhesion-preventing effect,
mechanical strength capable of suture fixation and guiding tissue
regeneration.
[0016] The term "suturable" in the present invention means such a
state that a membrane can be fixed at a part of the membrane, for
instance, two or more points thereof to an implanted part in a
living body, for example, defective sites in the pericardium,
cerebral dura mater, pleura, intestinal chorion and the like, or a
resected part in the lungs, liver or the like, using a general
suture thread for surgery. Further, it also means that the membrane
can be maintained in a state that the membrane does not easily
deviate, drop, or move from the suture-fixed position or deform for
a certain period of time.
[0017] The term "guided tissue regeneration" means that the
adhesion-preventing membranes transplanted into defective sites in
a tissue or organ have a property to induce regeneration of the
tissue. Specifically, such property refers to a state that natural
healing and a regeneration process take place smoothly without
showing an inhibition of normal regeneration of body tissues, which
is often observed when using an artificial composition such as a
synthetic high molecular compound.
[0018] The term "biocompatibility" in the present invention means
the degree of immunological and histological reactions in a living
body when an artificial product is implanted into the body and is
determined by an inflammatory response or the like observed by the
naked eye.
[0019] The term "adhesion" means an agglutination or adhesion
between organs or tissues that should be essentially separated from
each other. This adhesion is determined by observation with the
naked eye.
[0020] The adhesion-preventing membrane in the present invention
does not contain any synthetic material such as synthetic fibers,
but uses as main raw materials collagen and gelatin, or collagen
and hyaluronic acid, which are materials derived from an animal,
processes them into a form of a non-woven fabric or sponge, and
layers the processed materials to provide a laminated structure of,
mostly, 2 to 10 layers, preferably 3 to 5 layers.
[0021] In the adhesion-preventing membrane, it seems that the
non-woven fabric layer mainly provides sufficient suturable
membrane strength, the collagen sponge layer mainly provides
biocompatibility and promotion of tissue regeneration, and the
coating layer formed from gelatin or hyaluronic acid exerts
biocompatibility and an adhesion-preventing effect with surrounding
tissues.
[0022] The adhesion-preventing membrane of the present invention is
entirely composed of collagen and gelatin or hyaluronic acid each
of which is derived from an animal, so that it is excellent in
compatibility and, moreover, can be gradually decomposed and
absorbed in a living body to be totally decomposed and absorbed
where it is. In the decomposition and absorption process, the
collagen sponge layer mainly exerts characteristic properties of
collagen, such as hemostatic reaction and adhesion, proliferation
and extension of cells, thereby promoting tissue regeneration in a
tissue or organ where the membrane is implanted.
[0023] Also, the collagen non-woven fabric layer remains as a basis
to compensate, for prosthesis, or to seal defective parts or the
like in a living body until the parts complete regeneration of the
tissue. The collagen non-woven fabric layer maintains its strength
for a certain period after the suture fixation of the membrane, and
then is decomposed and absorbed similar to the collagen sponge
layer. Certainly, as this non-woven fabric layer is also composed
of collagen, the layer can not only maintain its strength but can
also significantly exhibit characteristics similar to the above
collagen sponge. Further, the outermost layer containing gelatin or
hyaluronic acid can prevent adhesion between damaged or defective
parts and surrounding tissues, owing to its viscosity and
sustained-release action.
[0024] Incidentally, the prevention of this adhesion lasts for a
period during which tissues of the damaged or defective parts are
regenerated and healed to an extent that adhesion between the
tissues thereof and the surrounding tissues does not take place
under the natural state. Since the adhesion-preventing membrane in
the present invention is especially capable of being sutured, it
can be directly fixed to a defective or damaged part in a living
body. Therefore, it is possible to certainly separate a part to be
adhered and a defective or damaged part and exert a good
adhesion-preventing effect without moving, dropping out or
deviating from the implanted part in a living body, which property
has been observed in conventional adhesion-preventing
membranes.
[0025] Representative collagen used for the present invention
includes solubilized collagen such as enzyme solubilized collagen,
acid solubilized collagen, alkali solubilized collagen or neutral
solubilized collagen. The solubilized collagen is one that is
solubilized with a proteolytic enzyme, for example, pepsin,
trypsin, or with an alkali, and is obtained by performing, at the
same time as solubilization, a treatment for removing telopeptide,
which is an antigenic determinant of collagen. Usually,
atelo-collagen applicable for medical use is especially suitable.
The solubilized collagen can be readily obtained from animals by
following publicly known techniques (Japanese Examined Patent
Publication Nos. 15033/1969, 259839/1968, 27513/1968 and
others).
[0026] Further, the source of the collagen used in the present
invention is not specially limited, but generally includes bovines,
swine, fowls, fishes, lapin, ovine, urine and humans. The collagen
is produced from skin, tendon, bone, cartilage, organs and the like
of these sources by means of various known extraction methods.
Additionally, no particular limitation is put on collagen that can
be classified into type I, type III or the like, but type I is most
suitable from the view of handling. The solvent to solubilize the
collagen is preferably water from the view point of handling.
[0027] Usual gelatin according to the Pharmacopoeia of Japan is
usable.
[0028] Either one of hyaluronic acids derived from animals or from
bacterium may be used but hyaluronic acid of medical grade is
particularly suitable.
[0029] In order to obtain the non-woven fabric layer having
sufficient suturable membrane strength, the above collagen solution
is extruded into a coagulating bath to form fibers, and the fibers
are crossed over one another in multiple layers at the bottom of
the coagulating bath. Otherwise, the extruded fibers are wound on a
plate in a certain direction to form a non-woven fabric layer
having parallel lines of fibers. A fibrous aggregation in which the
fibers have a diameter of 5 .mu.m to 1.0 mm, preferably 10 .mu.m to
1.0 mm, and more preferably 20 to 300 .mu.m, is obtained. The bulk
density (fiber density) of the fibrous aggregation is
5.times.10.sup.-4 to 5 g/cm.sup.3, preferably 1.0.times.10.sup.-3
to 2.0 g/cm.sup.3. That is, the above solubilized collagen solution
is continuously wet spun, and the long fibers obtained are
transferred to an appropriate vessel, and disposed to cross over
one another but not in a single direction, for example, at
approximately a 90.degree. angle.
[0030] Alternatively, the long fibers continuously extruded through
the orifices and coagulated in the spinning bath may be wound on a
plate in a certain direction to form a non-woven fabric having
parallel lines of fibers.
[0031] Then, non-woven fabric (fibrous material) is obtained which
is made flocculent by vacuum drying, natural drying,
low-temperature drying, blast drying or the like. It is important
for the collagen to be dried at a denatured temperature or lower of
the used collagen in each drying method in order to prevent
denaturing of the collagen. Therefore, the temperature is
preferably within a temperature range of about 35 to 45.degree. C.,
which depends on the types of used collagen. Low-temperature drying
or vacuum drying is especially preferable.
[0032] In another way, a fibrous material having short staples is
manufactured in a method of either continuous spinning or
non-continuous spinning, in which the fiber obtained is cut after
intermittent extruding of the non-continuous spinning, or usual
continuous spinning. It is also possible to obtain the non-woven
fabric (fibrous material) by drying the staples, in a uniformly
dispersed state in an appropriate size of vessel, through vacuum
drying, natural drying or the like.
[0033] The concentration of collagen solution used for spinning is
optional depending on the type of collagen used, and any
concentration is useful if it is spinnable. Usually, the
concentration is 0.1 to 20 wt %, of which a concentration of about
1 to 10 wt % is especially suitable for wet spinning. Further, the
extruding speed of solubilized collagen in the spinning thereof,
and the winding speed of obtained fibers are also optional as long
as they are a speed within a spinnable range.
[0034] The equipment usable for spinning the solubilized collagen
solution may be a gear-pump or dispenser for general purposes, or
various extruding equipment and the like, but is preferably
equipment which can extrude the collagen solution in a fixed amount
stably with minimum pulsation in order to provide uniform
spinning.
[0035] Additionally, the diameter size of the orifice of a spinning
head or needle used for spinning is not particularly limited as
long as spinning is possible. An extensively large orifice is
disadvantageous because it is difficult to make a membranous
substance from the fibrous material because the non-woven fabric
will be too bulky and-an extremely narrow orifice is also
disadvantageous because it is difficult to obtain sufficient
membrane strength. Accordingly, the diameter of the orifice is
usually in a range of 5 .mu.m to 1 mm, preferably 50 to 700 .mu.m.
The orifice number of a spining head is one or more. Further, the
shape of the orifice is also especially not limited, but a
slit-like shape or other various shapes may be used as long as
spinning is possible. Further, the length of the spinning head
orifice is also not limited but a longer orifice is preferred in
order to orient the collagen molecules in the solubilized collagen
molecules as much as possible.
[0036] The coagulating bath in wet spinning is not limited if it is
possible to generally coagulate collagen, and useful baths include
an aqueous solution of an inorganic salt, an organic solvent
containing solubilized inorganic salt therein, alcohols, ketones,
and a combination of these components. Among these coagulating
baths, for example, an aqueous solution of an inorganic salt
includes sodium sulfate, sodium chloride, ammonium sulfate, calcium
chloride, magnesium chloride, and the like, but sodium chloride,
sodium sulfate or ammonium sulfate is especially suitable for
spinning. These inorganic salts may be dissolved or dispersed in
alcohol or acetone to make an organic solvent containing
solubilized inorganic salts, which may also be utilized as the
bath. In particular, a solution in which sodium chloride is
dissolved or dispersed in ethanol is preferable.
[0037] Further, suitable alcohols include methanol, ethanol,
isopropanol, amylalcohol, and the like, and especially, ethanol is
preferable for medical use. Ketones include acetone,
methylethylketone and the like.
[0038] When combined with various cross-linking agents as described
below, the solution for coagulating ceases from serving simply as a
coagulating bath and is useful for a cross-linking treatment as
well as collagen coagulation. For example, when a mixed solution of
ethanol and glutaraldehyde is used for a bath for both coagulation
and cross-linking, both processes can be concurrently carried out,
and cross-linking can be done by immersing the spun collagen fiber
as it stands. These concurrent processes not only simplify the
overall process but also are highly beneficial for spinning of
dilute collagen solutions or spinning of fibers with a thin
diameter.
[0039] Of the methods for forming the above non-woven fabric layer,
a specific example particularly preferred is described below. A
spinning head for extruding a collagen has an orifice diameter of
about 200 .mu.m and an orifice length of about 15 to 20 mm, and a
solubilized collagen solution is extruded without pulsation through
the spinning head by means of a dispenser or the like, and then
desirably wet-spun in a 99.5 vol % ethanol coagulating bath. When
the solubilized collagen is extruded into the 99.5 vol % ethanol
coagulating bath, the extrusion mouthpiece is moved whenever
necessary so as to extrude continuously the fibers that are spun
out and cross or lay the fibers over one another in an arbitrary
direction to form layers of the fibers. After the fibers are
multi-layered, the coagulation solution is removed, and the fibers
are washed with ethanol again and then subjected to vacuum drying
to obtain excellent soft fibrous materials. This method is
beneficial especially in simplification or shortening of the
process and in economy because of concurrent spinning and formation
of a non-woven fabric.
[0040] The above example is representative, but the invention is
not limited thereto as long as the fibrous materials can be
obtained. For example, the staple short fiber mentioned above may
be used. It is possible to change, without causing any
inconvenience, conditions such as the sort of coagulating bath, to
use or not to use a mixed bath of coagulating bath and
cross-linking agent, or a drying method, or to change the
combination of conditions.
[0041] Preferably, the non-woven fabric layer obtained in the above
method is further cross-linked in order to obtain a sufficient
suture strength. This is because cross-linking improves physical
strength especially under wet conditions, so that strength
necessary for suturing can be sufficiently secured. Additionally,
cross-linking also prolongs markedly the time the membrane takes to
be discomposed and absorbed after it is implanted in a living body,
as compared with the case where cross-linking is not performed.
[0042] Owing to the cross-linking treatment, the membrane can
remain in a living body while maintaining a necessary membrane
strength until reconstruction of an injured surface and tissue
regeneration are completed after a defective part of the body is
repaired, augmented or replaced, and organ or tissue malfunction
due to the defect is prevented.
[0043] Cross-linking methods are roughly classified into a physical
cross-linking method and a chemical cross-linking method. The
physical cross-linking method includes a cross-linking by means of
.gamma.-ray, ultraviolet ray, electron beam, plasma, thermal
dehydration, etc. On the other hand, a representative example of
the chemical cross-linking method includes a treatment with
aldehydes such as dialdehyde and polyaldehyde, epoxy compounds,
carbodiimides, isocyanate compounds, tannin, chromium, etc. Of
these, useful aldehydes include formaldehyde, glutaraldehyde,
glyoxal, malondialdehyde, succinyl dialdehyde, phthalaldehyde,
dialdehyde starch, polyacrolein, polymethacrolein, and the like,
but any aldehyde can be used as long as it causes a cross-linking
reaction with collagen. Epoxy compounds include
glycerol-diglycidylether, sorbitol-diglycidylether,
ethyleneglycol-diglycidylether, polyethyleneglycol-diglycidylether,
polyglycerol-polyglycidylether and the like. Other epoxy compounds
that can cause a cross-linking reaction with collagen are also
usable. Though a particularly suitable example of carbodiimides is
a water soluble carbodiimide, any carbodiimide can be used as long
as a similar reaction is caused. Representative examples of
isocyanate compounds include hexamethylene diisocyanate, tolylene
diisocyanate and the like. However, useful isocyanates are not
limited thereto and any isocyanate that has two or more isocyanate
groups involved with a cross-linking reaction can be used, for it
can perform cross-linking on collagen.
[0044] The non-woven fabric (fibrous material) obtained by spinning
and so forth according to the above method may be further
compressed in order to obtain a higher suture strength. The
compression allows the non-woven fabric layer to increase the fiber
density, producing a preferable membranous substance with more
strength.
[0045] The collagen non-woven fabric can be compressed by means of
a general press, but because of its intended medical use, it is
preferable to compress the fabric while it is aseptically packaged
with a sufficiently tough sterilized package material, for example,
an aluminum package or a high-strength resinous packaging
material.
[0046] On this occasion, a pressure for compressing the non-woven
fabric is not limited if it does not tear down the body of the
non-woven fabric layer, and usually a preferable pressure is 10
kgf/cm.sup.2 to 1000 kgf/cm.sup.2.
[0047] The non-woven fabric layer is preferably compressed and
thinned as much as possible not only to increase the bulk density
(fiber density) for the purpose of improving strength, but also
from the view of handling in medical use when the non-woven fabric
layer is processed into its final form of an adhesion-preventing
membrane that has a layered structure. The non-woven fabric layers
thus thinned are laminated to have a multi-layered structure so
that an adhesive-preventing membrane with even higher suture
strength can be obtained. The bulk density after compression (fiber
density) is preferably 0.1 to 5 g/cm.sup.3.
[0048] To improve the physical strength of the non-woven fabric
layer or compressed non-woven fabric layer obtained by the above
method, a binder treatment can be carried out. The binder is
preferably a solubilized collagen solution. This is a method in
which the non-woven fabric layer or the compressed non-woven fabric
layer is immersed in a solubilized collagen solution and then dried
by a suitable drying method such as natural drying, air drying,
vacuum drying, or drying under low temperature so that the fibers
in the non-woven fabric layer are combined with each other to make
them membranous.
[0049] The physical strength of the membranous substance obtained
by this binder treatment is much more improved over that of a
simple non-woven fabric layer, and therefore, the suture strength
is also remarkably improved. In addition, these immersion and
drying processes can be repeated several tens of times or more,
without any inconvenience, depending on the required physical
strength.
[0050] However, unless the non-woven fabric layer or compressed
non-woven fabric layer is cross-linked, the non-woven fabric layer
itself may be dissolved in the solubilized collagen solution when
it is immersed therein in the binder treatment. Therefore, the
fabric layer is preferably cross-linked previously by the above or
other methods. In addition, along with an immersion treatment,
there are a method in which the solubilized collagen solution is
charged in a suitable vessel or mold containing the non-woven
fabric layer and a method in which the solubilized collagen
solution is directly applied to the non-woven fabric layer for
improving the physical strength of the fabric layer.
[0051] A sponge layer made of collagen in the present invention is
a micro-porous collagen layer, and the pore diameter varies
depending on the type of collagen, producing method, etc. The
percentage of the pores in the sponge layer (the pore rate) is
usually 10 to 90%.
[0052] In one embodiment of the present invention the membranous
substance has one to six, preferably one to three layers of a
collagen non-woven fabric layer. Said membranous substance has a
thickness of 0.05 mm to 100 mm, preferably 0.1 mm to 50 mm, more
preferably 0.2 mm to 40 mm. The surface of the membranous substance
is a gelatin or hyaluronic acid layer. Preferably, one to four
layers of the gelatin or hyaluronic acid are contained, and each
layer is in a form of a film or sponge having a thickness of 0.05
mm to 20 mm.
[0053] Another embodiment of the present invention is a membranous
substance that has a laminated structure comprising a non-woven
fabric layer made of collagen fibers and a sponge layer made of
collagen. In particular, the collagen non-woven fabric layer has a
thickness of 0.05 mm to 100 mm, preferably 0.1 mm to 50 mm, more
preferably 0.2 mm to 40 mm, the collagen sponge layer has a
thickness of 0.05 mm to 20 mm, preferably 0.1 mm to 20 mm, and the
present membranous substance has one to six layers of collagen
non-woven fabric layer and one to four layers of collagen sponge
layer. The surface of the membranous substance is a gelatin or
hyaluronic acid layer. Preferably, one to four layers of the
gelatin or hyaluronic acid are contained, and each layer is in a
form of a film or sponge having a thickness of 0.05 mm to 20 mm,
preferably 0.1 to 10 mm.
[0054] Though the non-woven fabric layer in the membranous
substance in the present invention has enough membrane strength to
withstand suturing by itself, the membrane strength can be further
improved by a binder treatment. There are two binder treatment
methods. One is such that the membranous substance is obtained by
sandwiching a non-woven fabric layer between collagen layers
previously dried to assure a sponge form. The membranous substance
is put under normal pressure or reduced pressure in the presence of
a dilute collagen solution or water to dissolve the solubilized
collagen sponge layer, the dissolved layer is sufficiently absorbed
into the non-woven fabric layer, and then the substance is dried by
various drying methods. According to another method, the sponge
layer and the non-woven fabric layer are simultaneously compressed,
burying the non-woven fabric layer into the sponge layer to obtain
the membranous substance. The membranous substance is also treated
similarly to the above binder treatment.
[0055] In the binder treatment using this sponge layer, the time
expended in drying in a later process is short because only a very
small amount of a solvent component such as water is required
relative to the amount of collagen that is actually used, owing to
the combined fibers of the non-woven fabric layer. Further,
contractive deformation or the like upon drying takes place much
less frequently, which is a great merit. In a usual immersion
process, a substantial amount of collagen in the solubilized
collagen solution for immersion is about a few percent maximum from
a practical solution viscosity, and the rest, i.e., 90% or more of
the solution is a solvent component such as water. The usual
immersing process is simple but unreasonable because immersion and
drying operations not only take much time but also have to be
repeated. Needless to say, the above are merely representative
examples and are not intended to limit the invention thereto. Any
method is usable as long as the fibers of the non-woven fabric
layer or the compressed non-woven fabric layer are combined with
each other using the solubilized collagen, to lo form them into a
membranous substance.
[0056] In the present invention, it is optionally required that the
collagen non-woven fabric layer obtained by the above method in the
present invention further has the collagen sponge layer, and
required that the gelatin or hyaluronic acid layer is formed on the
surface of the laminated membranous substance. Following a
conventional method, the gelatin or hyaluronic acid layer is
readily formed by lyophilization or other method. A specific method
for manufacturing the membranous substance comprises: (1) immersing
the non woven fabric layer treated with the binder in a vessel
filled with a collagen solution; (2) adjusting the position of the
fabric layer so that it stays in the middle depth of the collagen
solution; (3) freezing the vessel; (4) performing lyophilization to
obtain a collagen sponge layer; (5) compressing the resultant
layers to obtain the membranous substance; (6) immersing the
membranous substance in a vessel filled with a hyaluronic acid
solution; (7) performing freezing, lyophilization, and compression
as in a hyaluronic acid sponge layer; and, finally, (8) performing
thermal dehydration cross-linking on the adhesion-preventing
membrane.
[0057] The processes of forming the collagen sponge layer and the
gelatin or hyaluronic acid sponge layer are not limited in their
order, way or the like. A method is given by way of example, which
comprises producing each sponge layer separately, and then, joining
them with the collagen non woven fabric layer using solubilized
collagen as an adhesive.
[0058] Additionally, there is a method in which the collagen
non-woven fabric layer is immersed in a solubilized collagen
solution, frozen, similarly again immersed in the gelatin or
hyaluronic acid solution and these are frozen to be integrated and
lyophilized so as to simultaneously obtain the collagen layer and
the gelatin or hyaluronic acid layer, which are layered to form the
sponge laminate. However, since these methods are for maintaining
the sponge layer integrated with the non-woven fabric layer without
being peeled off or separated easily when the laminated product is
transplanted into a living body, any method may be used if the
purpose is accomplished.
[0059] As to manufacture of the sponge layer, the solubilized
collagen solution, gelatin solution, hyaluronic acid solution, or
other solution is poured into a vessel or charged in the vessel
until a desired depth is obtained, frozen sufficiently by a general
freezer and then, dried by a lyophilizer to produce a uniform
sponge layer. The diameters of minute pores formed in the sponge
depend upon various conditions such as the concentration of the
solubilized collagen solution, gelatin solution or hyaluronic acid
solution, the solvent thereof, the temperature of freezing and the
freezing time.
[0060] The thickness of the respective sponge layer and total
amounts of the substances used for the sponge layer can be suitably
controlled in consideration of the decomposition and absorption
time when the sponge is transplanted into a living body and of the
effects on the guided tissue regeneration. In view of these
considerations, the concentration of solubilized collagen solution
is generally 0.5 to 5 wt %, and preferably, 1 to 3 wt %. The
concentration range of the gelatin solution is 0.5 to 60 wt %, and
preferably, 5 to 40 wt %. Further, the concentration range of the
hyaluronic acid solution is preferably 0.1 to 50 wt %.
[0061] The freezing temperature is -196.degree. C. to -10.degree.
C., and preferably, -80.degree. C. to -10.degree. C. This is a
temperature capable of being provided by a general freezer or
deep-freezer. The lyophilizer is not particularly limited as long
as it is capable of stable drying.
[0062] Further, the solubilized collagen solution, gelatin solution
or hyaluronic acid solution is charged in the vessel in such an
amount that the thickness of the finished sponge is about 1 mm to
20 mm in general. This thickness may be changed whenever necessary
according to the purposes of their usage, and is not limited to
these exemplifications.
[0063] The total amount of the respective substances and the
thickness of the respective sponge layers for the collagen sponge
layer, gelatin sponge layer and hyaluronic acid sponge layer are
desirably determined such that each sponge layer remains in a
living body for about one to four weeks in general, so as not to
interfere with the adhesion-preventing effect on an implanted part,
repair of a damaged or cut part, or induction of tissue
regeneration and the like.
[0064] Incidentally, the hyaluronic acid or gelatin layer exerting
an adhesion-preventing effect is not limited to the shape of the
sponge but may be manufactured as, for example, a film obtained by
a usual casting method. When the gelatin or hyaluronic acid layer
is formed in order to provide an adhesion-preventing effect,
various modes may be selected to suit the intended purpose. For
example, the gelatin or hyaluronic acid layer covers one surface or
both surfaces of the membrane, or covers a part of the surface or
the entire surface. The forming method of the gelatin or hyaluronic
acid layer or where to form the layer is not particularly
limited.
[0065] Throughout the adhesion-preventing membrane of the present
invention, collagen and gelatin or hyaluronic acid, compose the
membrane. Therefore, cross-linking is performed by the above
various cross-linking methods on the sponge layer, the non-woven
fabric layer and the gelatin or hyaluronic acid layer which compose
the membrane, and on a part of or the entirety of the
adhesion-preventing membrane in which these layers are laminated
and integrated.
[0066] The order and the way of cross-linking can be freely
combined and is not particularly limited. Most desirably, the
collagen non-woven fabric layer is treated with an aldehyde such as
glutaraldehyde, the collagen sponge layer and the gelatin or
hyaluronic acid layer are formed and integrated with the collagen
non-woven fabric layer and, lastly, thermal dehydration
cross-linking is carried out. In these methods, the process of
mixing coagulating agents such as ethanol with cross-linking agents
represented by glutaraldehyde to simultaneously carry out spinning
and cross-linking is also included.
[0067] The adhesion-preventing membrane finally obtained through
the method according to the present invention is excellent in the
effects of suture strength, biocompatibility, and induction of
tissue regeneration.
[0068] In addition, when the binder treatment is carried out in the
collagen non-woven fabric layer, it is preferable that the collagen
layer formed in the binder treatment is also subjected to thermal
dehydration cross-linking. This, however, is merely an example and,
for example, thermal dehydration cross-linking may be performed on
all of the layers without causing any inconvenience. Also, the
layers may be irradiated with gamma rays for both sterilization and
cross-linking. That is, the combination of cross-linking, and the
order in the manufacturing process of the present
adhesion-preventing membrane are not limited as long as the
cross-linking can be sufficiently carried out to an extent that the
above purpose of the cross-linking is established.
[0069] The adhesion-preventing membrane having the non-woven fabric
layer and the respective sponge layers obtained by the above method
can be further compressed. After the respective sponge layers or
the non-woven fabric layers are separately compressed, they may be
integrated with non-woven fabric layers or respective sponge layers
which are not compressed. It is particularly preferable that the
non-woven fabric layers integrated with respective sponge layers
are simultaneously compressed in the final process of the
production of the membrane. The compression causes a decrease in
thickness of the membrane, and the compressed membrane brings about
improvement in handling, for example, penetrability of a suturing
needle during suturing and desired-shape cutting when the
adhesion-preventing membrane is used in a surgical operation or the
like. Therefore, transplant surgery and others can be carried out
smoothly. The compression can be carried out by a general
compressor in the same manner as the compression of the non-woven
fabric layer. However, it is desirable that the compression is made
while the membrane is aseptically wrapped with a sufficiently tough
sterilized packaging material such as an aluminum package or a
high-strength resinous packaging material, because of the intended
medical use. Further, the pressure when compressing the
adhesion-preventing membrane is not limited if it is within a range
that does not destroy the membrane itself, and a normally preferred
pressure is 10 to 1000 kgf/cm.sup.2.
EXAMPLES
[0070] The following examples are given to further illustrate in
detail the present invention.
Example 1
[0071] First, in an Erlenmeyer flask (Corning Company), while
chicken-derived atelo-collagen was gently stirred with a magnetic
stirrer, distilled water for injection, i.e., water suitable for
injection according to Japanese Pharmacopoeia, was added thereto to
prepare two kinds of collagen solutions having concentrations of 3
wt % and 5 wt %, respectively. The procedure was carried out
aseptically in a clean bench.
[0072] Then, 40 ml of a 5 wt % collagen solution was continuously
extruded into a 99.5 vol % ethanol solution (Wako Pure Chemical
Industry Co., Ltd., special grade), as a coagulation bath, under a
constant pressure condition of 4.0 bar using a dispenser
(manufactured by Scientific Co.: EFD 900 type) equipped with a
syringe and 27 gauge needle (orifice diameter=200 .mu.m) to conduct
spinning.
[0073] In the continuous extrusion spinning, the needle tip was
allowed to move over the surface of the ethanol coagulation bath in
a random manner so that spinning was carried out such that the
settled and coagulated collagen filament crossed over itself in
multiple folds to obtain a non-woven fabric (a mass of fibrous
collagen). Then the non-woven fabric (mass) was left to stand for 1
hour to allow sufficient coagulation. Thereafter, in the 99.5%
ethanol solution, the coagulation solution was exchanged twice to
effect washing.
[0074] The above non-woven fabric (a mass of fibrous collagen) was
dried as it was in a vacuum dry oven (manufactured by EYELA CO.:
VOS-300VD type) for 4 hours at room temperature under reduced
pressure (below 1 Torr) using an oil rotary vacuum pump
(manufactured by ULVAC CO.: GCD135-XA type) to obtain the non-woven
fabric (fibrous collagen non-woven fabric). The diameter of the
fiber was 60 m and the bulk density of the non-woven fabric was
4.0.times.10.sup.-2 g/cm.sup.3.
[0075] Then, the non-woven fabric was charged in a sterilized
aluminum wrapping material and compressed at a pressure of 100
kgf/cm.sup.2 using a High Pressure Jack (manufactured by Iuchi
Seieido: 15 t press machine) to obtain compressed non-woven fabric
of about 8 cm.times.5 cm having fibers having a diameter of 60
.mu.m, a thickness of 0.6 mm and a bulk density of 0.9
g/cm.sup.3.
[0076] Then, the compressed non-woven fabric was immersed for 4
hours in a 5% glutaraldehyde solution (manufactured by Wako Pure
Chemical Industry Co., Ltd.: 25% first-grade glutaraldehyde
solution diluted with distilled water for injection) to carry out a
cross-linking treatment. After completion of the cross-linking
reaction, the non-woven fabric was washed sufficiently with
distilled water for injection and then immersed in a bath of
distilled water for injection for 1 hour, followed by three
exchanges of water during the dipping to remove excess
glutaraldehyde. The non-woven fabric after completion of the
cross-linking treatment was dried again, and compressed at a
pressure of 100 kgf/cm.sup.2 using a High Pressure Jack
(manufactured by Iuchi Seieido: 15 t press machine) to obtain a
compressed non-woven fabric of about 8 cm.times.5 cm which has
fibers having a fiber diameter of 60 Jim, a thickness of 0.6 mm,
and a bulk density of the non-woven fabric of 0.91 g/cm.sup.3.
[0077] Separately, a lyophilized collagen sponge was prepared for
binder treatment by the following method.
[0078] First, a 3 wt % solubilized collagen solution was charged in
a square container made of polystyrene to fill it to a depth of
about 17 mm and then subjected to a freezing treatment at
-20.degree. C. for 12 hours in a freezer (manufactured by SANYO
CO.: MEDICAL FREEZER). Then, the above frozen solubilized collagen
as contained in the above container was transferred into a
lyophilizer (manufactured by EYELA Co.: FDU-830 type), and
lyophilized for about 24 hours under a reduced pressure (below 0.05
Torr) using an oil rotary vacuum pump (manufactured by ULVAC CO.:
GCD200-XA type) to obtain a collagen sponge. After completion of
the lyophilization, the sponge had a film thickness of about 15 mm
and a porosity of about 80%.
[0079] One sheet of the above compressed non-woven fabric
(thickness of 0.6 mm) that had been subjected to the cross-linking
treatment together with one sheet of the above collagen sponge
(thickness of 15 mm) that had been separately prepared were
compressed again at a pressure of 100 kgf/cm.sup.2 to obtain a
collagen membranous substance having a size of about 7 cm.times.4.5
cm and a thickness of 1 mm having a two-layer structure in which
the non-woven layer was embedded in the sponge layer.
[0080] Then, the above membranous substance was immersed in 15 ml
of an aqueous 3 wt % solubilized collagen solution and in this
state was introduced in a vacuum drying oven (manufactured by EYELA
Co.: VOS-300VD type) where the pressure was reduced to remove the
air in the membranous substance to forcibly impregnate the
solubilized collagen solution into the sponge layer of the above
membranous substance. The sponge layer in the collagen membranous
substance was dissolved in water derived from the aqueous
solubilized collagen solution so as to form a one layer membranous
substance.
[0081] The membranous substance obtained was dried at a low
temperature (4.degree. C.) for 24 hours to obtain a collagen
membranous substance treated with the binder and having thickness
of 0.18 mm, and a size of about 7 cm.times.4.5 cm.
[0082] The obtained collagen membranous substance was transferred
to a square polystyrene container and a 30 wt % gelatin solution
was poured onto the membranous substance and the position of the
membranous substance adjusted with a sterile pincette, so that the
membranous substance was substantially positioned intermediately,
and frozen at -20.degree. C. for about 12 hours in a freezer
(manufactured by SANYO CO.: MEDICAL FREEZER). A membrane in a
lyophilized state having a three-layer laminated structure of
gelatin layer/compressed non-woven fabric layer/gelatin layer was
obtained.
[0083] This membrane having a three-layer laminated structure was
lyophilized in the container at -20.degree. C. for 24 hours
similarly to the above freezing method. Then the membrane having a
compressed collagen non-woven fabric layer combined with gelatin
sponge layers was compressed again under a pressure of 400
kgf/cm.sup.3 to obtain a membrane of a three-layer laminated
structure having a thickness of about 1.6 mm (compressed non-woven
fabric, 0.18 mm thick, and gelatin coatings, each 0.71 mm thick)
and a size of about 7 cm.times.5 cm.
[0084] Then, the obtained membrane was subjected to a heat
dehydration cross-linking treatment at 135.degree. C. under reduced
pressure (below 1 Torr) for 12 hours using a vacuum drying oven and
an oil rotary vacuum pump (manufactured by ULVAC CO.: GCD135-XA
type). Thus, an adhesion preventing membrane was obtained in which
only the fibers in the collagen non-woven fabric layer were
subjected to the glutaraldehyde cross-linking treatment and the
respective surfaces each have a gelatin sponge layer having a
thickness of 0.4 mm. The suture strength, biocompatibility, tissue
regeneration induction and adhesion prevention properties of the
obtained adhesion preventing membrane are shown in Examples 3 and 4
below.
[0085] FIG. 1 is a flow chart illustrating the steps in this
example.
Example 2
[0086] In the same manner as in Example 1, chicken-derived
atelo-collagen was dissolved into distilled water for injection to
prepare a 5 wt % collagen solution. The procedure was carried out
aseptically in a clean bench.
[0087] The 5 wt % collagen solution was continuously extruded in
the same manner as in Example 1 into a mixed spinning bath
containing 1000 ml of 99.5 vol % ethanol (manufactured by Wako
Chemicals, special grade) and 42 ml of 25% glutaraldehyde under the
condition of a constant pressure of 2.0 barr using a dispenser
(manufactured by Scientific Co.: EFD900 type) equipped with a 20
gauge needle tip (orifice diameter 600 .mu.m). A non-woven fabric
made of fibers having a diameter of 200 .mu.m and having a bulk
density of 0.01 g/cm.sup.3 was obtained.
[0088] Then, the above non-woven fabric was reacted with
glutaraldehyde in a coagulation and cross-linking bath containing a
mixture of about 1% glutaraldehyde and ethanol for 4 hours in the
same manner as in Example 1. Then, the mixed solution containing
glutaraldehyde and ethanol was removed from the bath, and the
non-woven fabric was washed three times with a 99.5% ethanol
solution to remove the residual glutaraldehyde.
[0089] This collagen non-woven fabric was dried under reduced
pressure in the same manner as in Example 1, and compressed at a
pressure of 100 kgf/cm.sup.2 to obtain a compressed non-woven
fabric having a thickness of 0.7 mm and a size of about 7
cm.times.5 cm (the fiber diameter was 200 .mu.m and the bulk
density of the non-woven fabric was 0.8 g/cm.sup.3). Two sheets of
the obtained compressed non-woven fabric were overlaid to form a
laminated structure.
[0090] Then, two sheets of the compressed non-woven fabric were
charged in a square polystyrene container and a 20 wt % hyaluronic
acid solution was filled into the container from the top, frozen at
-20.degree. C. for 12 hours in a freezer (manufactured by SANYO
CO.: MEDICAL FREEZER) and then lyophilized for about 24 hours.
Thus, a membranous substance of a 4-layer structure having the
collagen non-woven fabric layers between hyaluronic acid sponge
layers was obtained.
[0091] The thus-obtained membranous substance was compressed at a
pressure of 500 kgf/cm.sup.2 to obtain an adhesion preventing layer
having a thickness of about 1.9 mm and a size of about 7 cm.times.5
cm. Then, the obtained membrane was subjected to a heat dehydration
cross-linking treatment at 135.degree. C. under reduced pressure
(below 1 Torr) for 12 hours using a vacuum drying oven and an oil
rotary vacuum pump (manufactured by ULVAC CO.: GCD135-XA type).
Thus, a 4-layer structure of an adhesion preventing membrane
(having a thickness of about 1.9 mm and a size of about 7
cm.times.5 cm) was obtained in which two laminated layers of
non-woven fabric (each layer having a 0.7 mm thickness) were
cross-linked with glutaraldehyde and both surfaces of the laminated
layers were combined with a hyaluronic acid sponge layer having a
thickness of about 0.25 mm and heat cross-linked. The suture
strength, biocompatibility, induction of tissue regeneration and
adhesion-preventing properties of the obtained adhesion preventing
membrane are shown in Examples 3 and 4 below.
[0092] FIG. 2 is a flow chart illustrating the steps in this
example.
Example 3
[0093] Measurement of Suture Strength
[0094] The suture strength of the adhesion preventing membranes
prepared in Examples 1 and 2 were measured. As control samples,
Goretex pericardium (manufactured by Goretex Co.: Goretex EPTFE
Patch II (sheet for pericardium)), porcine extracted pericardium,
and porcine extracted cerebral dura mater were used. The porcine
extracted pericardium and extracted cerebral dura mater were
extracted from an about 20 kg pig by an extraction operation under
anesthesia and then, after extraction of each membrane, immersed in
physiological saline and immediately measured in a fresh state.
[0095] The measurement method was as follows. First, sample
membranes and control membranes were all cut out as plate-like
sections of 1 cm.times.2.5 cm and in a central part of each
membrane at a distance of 5 mm from an end in the direction of a
longer side a suture (4-0 proline thread, manufactured by ETHICON,
INC.) was passed and bound to form a ring. The section to which a
suture was bound was immersed in physiological saline for 30
minutes and then taken out quickly, followed by measuring its
tensile strength using a tensile strength meter (Autograph S-S500D,
manufactured by Shimadzu Seisakusho Co., Ltd.). The measurement was
carried out under conditions where the end opposite to the end in
which the suture was passed was fixed to a distance of about 10 mm
from the end, and the ring-like suture at one end was engaged with
a hook for measurement, which was pulled at a constant speed of 10
mm/minute to carry out the measurement. In this case, a change in
strength until the section was cut by the 4-0 proline thread or the
proline thread departed from the section was measured. Among the
recorded strength values, the highest value was defined as a suture
strength (N: Newton) of the adhesion preventing membrane.
[0096] The results are shown in Table 1. TABLE-US-00001 TABLE 1
Goretex Porcine Porcine peri- peri- cerebral Example Example
cardium cardium dura mater 1 2 Measured 8.5 4.0 8.3 8.5 5.1 value
(N)
[0097] As can be seen from Table 1, the adhesion preventing
membrane of the present invention has suture strength enough to
endure the usual suturing fixation.
Example 4
[0098] Implant Test
[0099] The adhesion preventing membrane obtained in Example 1 was
implanted in the back muscle of rabbits (n=8) and tissue reaction
was observed with the naked eye and using an optical microscope to
evaluate its biocompatibility.
[0100] The implanted sample used was obtained by cutting the
adhesion preventing membrane obtained in Example 1 to a size of 1.5
mm.times.10 mm. As a control, a high density polyethylene plate was
used cut to the same size as the sample. The control was subjected
to ethylene oxide gas sterilization before use. The sample membrane
was used for the implanting test after sterilization by irradiation
with 25 kGy .gamma. rays.
[0101] For implanting, first, a rabbit (body weight about 2.5 kg to
3.0 kg) was subjected to ordinary inhalation anesthesia and then
the control and the sample were implanted aseptically so that they
sandwiched the back spine of the rabbit such that the control was
on the left hand side and the sample was on the right hand side of
the back spine of the rabbit. The implanting method was such that a
sterilized 15 gauge syringe punctured obliquely the surface of skin
at an angle of about 30 degrees, and the sample membrane and
control were pushed out, thus implanting them in the muscle of
rabbit. After this, four rabbits were used after 1 week and another
four rabbits were used after 4 weeks from the implanting as objects
of observation.
[0102] At each observation time, only two out of the four rabbits
were incised at the implanted part under anesthesia and observation
of the implanted portion and peripheral tissues was made visually
centered on an inflammatory reaction, etc. The remaining two
rabbits were sacrificed with excessive anesthesia and after the
peripheral tissue containing the implanted portion was extracted,
ordinary formalin fixation was conducted and then a section was
prepared, which was observed under a microscope.
[0103] From the results of these observations, the sample membrane
showed no significant inflammatory reaction, etc. as compared with
the control at any observation time for all rabbits, thus revealing
that the adhesion-preventing membrane obtained by the present
invention has good biocompatibility. In the case where 4 weeks
elapsed from the implanting, it was observed that the sample
membrane was decomposed and absorbed.
Example 5
[0104] Study of Adhesion Preventing Effect
[0105] Ten rats (body weight 250 g to 300 g) were divided into two
groups each consisting of 5 rats, one group being a control and the
other a sample group which used the adhesion preventing membrane
prepared in Example 1. For each of the control group and sample
group, the rats were narcotized intramuscularly and thereafter the
narcotized state was retained by inhalation anesthesia. For the
control group, the rats were incised at the abdomen under
anesthesia to expose the cecum and then the chorion of a size of
about 5 mm square was peeled off. The abdominal portion
corresponding to the cecum chorion was peeled off similarly and an
adhesion model in which the injured surface of the cecum and the
injured abdominal surface served as connection surfaces was
prepared. Thereafter, for the control group, the abdomen was
stitched without any further treatment.
[0106] On the other hand, for the sample group, an adhesion model
was prepared in the same manner as the control group and thereafter
the injured cecum surface was covered with the adhesion preventing
membrane prepared in Example 1 and fixed. The size of the fixed
adhesion preventing membrane was on the order of about 10
mm.times.10 mm and the membrane was sutured and fixed at the four
corners thereof being lightly hung on the intestinal tract with a
suture (5-0 bicryl thread). For both the sample group and the
control group, the rats were reoperated after two weeks for
celiotomy to visually observe the respective states of
adhesion.
[0107] The degree of adhesion upon visual observation was judged
based on the criteria in Table 2 below and assigned score to
comparatively evaluate the sample group and control group. Rank 3
or higher was adopted for concluding that adhesion occurred.
TABLE-US-00002 TABLE 2 State/Condition Score Rank Degree of No
adhesion 0 1 adhesion Membranous adhesion (readily 1 2 manually
peelable) Fibrous adhesion (readily peelable 2 3 by incision, etc.)
Restiform adhesion (Peeling by 3 4 incision is needed) Membranous
adhesion (Difficult to 4 5 peel without giving injury to the
tissue)
[0108] TABLE-US-00003 TABLE 3 Control group Sample group Average
score 3.2 0.6 Number of adhesion confirmed 5 cases 0 case
[0109] As a result of the comparative study between the sample
group and the control group based on the criteria in Table 3, there
was in the sample group no case in which adhesion was observed
while in the control group adhesion at Rank 3 or higher was
observed for all cases. In the sample group, the adhesion
preventing membrane remained at the fixed part but did not move to
other parts for almost all of the cases so that it served to
separate the injured surfaces from each other. Further, the
remained adhesion preventing membrane was carefully peeled off and
the injured surface of the cecum was visually observed. As a
result, it was observed that the injured surface started to
heal.
Example 6
[0110] First, in an Erlenmeyer flask, while chicken-derived
atelo-collagen was gently stirred with a magnetic stirrer,
distilled water for injection was added thereto to prepare two
kinds of collagen solutions having concentrations of 3 wt % and 5
wt %, respectively. The procedure was carried out aseptically in a
clean bench.
[0111] Then, 40 ml of a 5 wt % collagen solution was continuously
extruded into a 99.5 vol % ethanol liquid (Wako Pure Chemical
Industry Co., Ltd., special grade), which is a coagulation bath,
under a constant pressure condition of 4.0 bar using a dispenser
(manufactured by Scientific Co.: EFD 900 type) equipped with a
syringe and a 27 gauge needle to conduct spinning.
[0112] In the continuous extrusion spinning, the needle tip was
allowed to move over the surface of the ethanol coagulation bath in
a random manner so that spinning was carried out such that the
settled and coagulated collagen filament crossed over in multiple
folds to obtain a non-woven fabric (a mass of fibrous collagen).
Then the non-woven fabric (mass) was left to stand for 1 hour to
allow sufficient coagulation. Thereafter, in the 99.5% ethanol
solution, the coagulation solution was exchanged twice to effect
washing. The diameter of the fiber was 60 .mu.m and the bulk
density of the non-woven fabric was 0.9 g/cm.sup.3.
[0113] The above non-woven fabric (a mass of fibrous collagen) was
dried as it was in a vacuum drying oven (manufactured by EYELA CO.:
VOS-300VD type) for 4 hours at room temperature--under reduced
pressure (below 1 Torr) using an oil rotary vacuum pump
(manufactured by ULVAC CO.: GCD135-XA type) to obtain a non-woven
fabric (fibrous collagen non-woven fabric). Then, the non-woven
fabric was charged in a sterilized aluminum wrapping material and
compressed at a pressure of 100 kgf/cm.sup.2 using a High Pressure
Jack (manufactured by Iuchi Seieido: 15 t press machine) to obtain
a compressed non-woven fabric of about 8 cm.times.5 cm (the
diameter of fibers was 60 .mu.m, the bulk density of non-woven
fabric was 0.9 g/cm.sup.3).
[0114] Then, the compressed non-woven fabric was immersed for 4
hours in a 5% glutaraldehyde solution (manufactured by Wako Pure
Chemical Industry Co., Ltd.: 25% first-grade glutaraldehyde
solution diluted with distilled water for injection) to carry out a
cross-linking treatment. After completion of the cross-linking
reaction, the non-woven fabric was washed sufficiently with
distilled water for injection and then immersed in a bath of
distilled water for injection for 1 hour, followed by three
exchanges of water during the dipping to remove excess
glutaraldehyde. The non-woven fabric after completion of the
cross-linking treatment was dried, charged in a sterilized aluminum
wrapping material, and compressed at a pressure of 100 kgf/cm.sup.2
using a High Pressure Jack (manufactured by Iuchi Seieido: 15 t
press machine) to obtain a compressed non-woven fabric of about 8
cm.times.5 cm (the diameter of fibers was 60 .mu.m, the bulk
density of the non-woven fabric was 0.9 g/cm.sup.3).
[0115] Separately, a lyophilized collagen sponge was prepared by
the following method.
[0116] First, a 3 wt % solubilized collagen solution was charged in
a square polystyrene container to fill it to a depth of about 17 mm
and then subjected to a freezing treatment at -20.degree. C. for 12
hours in a freezer (manufactured by SANYO CO.: MEDICAL
FREEZER).
[0117] Then, the above frozen solubilized collagen as contained in
the above container was transferred into a lyophilizer
(manufactured by EYELA Co.: FDU-830 type), and lyophilized for
about 24 hours under a reduced pressure (below 0.05 Torr) using an
oil rotary vacuum pump (manufactured by ULVAC CO.: GCD200-XA type)
to obtain a collagen sponge. After completion of the lyophilization
the sponge had a film thickness of about 15 mm and a porosity of
about 70%.
[0118] One sheet of the above compressed non-woven fabric (0.6 mm
thick) that had been subjected to the cross-linking treatment
together with two sheets of the above collagen sponge (15 mm thick)
that had been separately prepared was compressed again at a
pressure of 100 kgf/cm.sup.2 to obtain a collagen membranous
substance having a size of about 8 cm.times.5 cm having a
three-layer structure in which the non-woven layer was embedded in
the sponge layers. The surface layers of the (sponge
layer/non-woven layer/sponge layer) are collagen sponge layers.
[0119] Then, the above membranous substance was immersed in 15 ml
of an aqueous 3 wt % solubilized collagen solution and in this
state was introduced in a vacuum drying oven (manufactured by EYELA
Co.: VOS-300VD type) where the pressure was reduced to remove the
air in the membranous substance to forcibly impregnate the
solubilized collagen solution into the sponge layers of the above
membranous substance. The obtained membranous substance of which
the sponge layers were dissolved was dried at a low temperature
(4.degree. C.) for 24 hours.
[0120] The dry membranous substance was transferred to a square
polystyrene container and a 3 wt % solubilized collagen solution
was poured onto the dry membranous substance to a depth of 15 mm.
After adjustment of the position of the membranous substance with a
sterile pincette, etc. so that the membranous substance was
substantially positioned intermediately in the solution, it was
frozen at -20.degree. C. for about 12 hours in a freezer
(manufactured by SANYO CO.: MEDICAL FREEZER). Further,
lyophilization was conducted to obtain a membrane in a lyophilized
state having a three-layer laminated structure of collagen sponge
layer/non-woven fabric layer/collagen sponge layer.
[0121] The above collagen membranous substance in a lyophilized
state was compressed at a pressure of 200 kgf/cm.sup.2 and then
immersed in a 30 wt % gelatin solution. Similarly, a freezing
treatment was conducted at -20.degree. C. for 12 hours. Thus, a
membrane in a lyophilized state having a 5-layer laminated
structure of gelatin layer/collagen sponge layer/collagen non-woven
fabric layer/collagen sponge layer/gelatin layer was obtained.
[0122] Then, the obtained collagen membranous substance in which
the compressed non-woven fabric layer and various sponge layers
were integrated was compressed again similarly at a pressure of 400
kgf/cm.sup.2 to obtain a collagen membranous substance of a 5-layer
structure (gelatin layer/collagen sponge layer/collagen non-woven
fabric layer/collagen sponge layer/gelatin layer) having a
thickness of about 1.6 mm and a size of about 8 cm.times.5 cm. The
total thickness of collagen sponge layers and non-woven fabric
layers is 1.0 mm and the thickness of each gelatin layer is 0.3
mm.
[0123] Then, the obtained membrane was subjected to a heat
dehydration cross-linking treatment at 135.degree. C. under reduced
pressure (below 1 Torr) for 12 hours using a vacuum drying oven and
an oil rotary vacuum pump (manufactured by ULVAC CO.: GCD135-XA
type). Thus, an adhesion preventing membrane was obtained in which
only the fibers in the collagen non-woven layer were subjected to
the glutaraldehyde cross-linking treatment and the heat dehydration
cross-linking. The suture strength, biocompatibility, tissue
regeneration induction and adhesion prevention properties of the
obtained adhesion preventing membrane are shown in Examples 8 to 10
below.
[0124] FIG. 3 is a flow chart illustrating the steps in this
example.
Example 7
[0125] Non-woven fabric was obtained in the same manner as in
Example 6 except that spinning was conducted under the condition of
a constant pressure of 2.0 bar using a dispenser (manufactured by
Scientific Co.: EFD900 type) equipped with a 20 gauge needle
(orifice diameter 600 .mu.m). Then, the obtained non-woven fabric
was subjected to glutaraldehyde treatment in the same manner as in
Example 6 for 4 hours and compressed again.
[0126] Two sheets of the obtained compressed non-woven fabric were
overlaid to form a laminated structure. Then, two sheets of the
compressed non-woven fabric were charged in a square polystyrene
container and a 3 wt % collagen solution was filled to a depth of
15 mm, freezing was conducted at -20.degree. C. for 12 hours in a
freezer (manufactured by SANYO CO.: MEDICAL FREEZER) and then
lyophilization was conducted for about 24 hours.
[0127] The obtained collagen sponge membrane containing the
non-woven fabric was again impregnated with about 20 ml of a 3 wt %
collagen solution to render the collagen sponge layer completely
gel-like and was then dried for about 12 hours in a clean bench
under ventilation. Thus, a plate-like collagen membrane was
obtained in which the non-woven fabric had been subjected to binder
treatment with a collagen solution.
[0128] The plate-like collagen membrane was immersed for 4 hours in
a 5% glutaraldehyde solution (manufactured by Wako Pure Chemical
Industry Co., Ltd.: 25% first-grade glutaraldehyde solution diluted
with distilled water for injection) to carry out cross-linking.
After completion of the reaction, the plate-like collagen membrane
was washed sufficiently with distilled water for injection and then
immersed in a bath of distilled water for injection for 2 hours,
followed five exchanges of water during the dipping to remove
excess glutaraldehyde.
[0129] The membranous substance after completion of the washing was
dried at 4.degree. C. for 24 hours and then transferred to a square
polystyrene container and a 3 wt % solubilized collagen solution
was poured onto the dry membranous substance to a depth of 15 mm.
After adjustment of the position of the membranous substance with a
sterile pincette, etc. so that the membranous substance was
substantially positioned intermediately in the solution, it was
frozen at -20.degree. C. for about 12 hours in a freezer. The
lyophilized collagen membrane together with the square polystyrene
container was subjected to lyophilization for about 24 hours.
[0130] Then, the obtained collagen membranous substance in which
the compressed non-woven fabric layers and sponge layers were
integrated was compressed again at a pressure of 400 kgf/cm.sup.2
to obtain a collagen membranous substance of a 4-layer structure
having a thickness of about 1.7 mm and a size of about 8 cm.times.5
cm.
[0131] The membranous substance was transferred to a square
polystyrene container and a 3 wt % hyaluronic acid solution was
filled therein to a depth of about 10 mm and
freezing/lyophilization was carried out to obtain a membranous
substance having a sponge layer of hyaluronic acid.
[0132] Thus, a sponge layer of hyaluronic acid was formed on the
entirety of the outer surfaces of the collagen sponge layer. The
thus-obtained laminated membrane was compressed again at a pressure
of 400 kgf/cm.sup.2 to obtain an adhesion preventing layer of a
6-layer structure having a thickness of about 1.9 mm and a size of
about 8 cm.times.5 cm. The total thickness of the non-woven fabric
layers and sponge layers was 1.7 mm and the thickness of each
hyaluronic acid layer was 0.1 mm.
[0133] Then, the obtained membrane was subjected to heat
dehydration cross-linking treatment at 135.degree. C. under reduced
pressure (below 1 Torr) for 12 hours using a vacuum drying oven and
an oil rotary vacuum pump (manufactured by ULVAC CO.: GCD135-XA
type). Thus, an adhesion preventing membrane was obtained in which
the non-woven fabric layer and binder layer had been subjected to
the glutaraldehyde cross-linking treatment and the collagen sponge
layer and hyaluronic acid sponge layer had been subjected to the
heat dehydration cross-linking. The suture strength of the obtained
adhesion preventing membrane is shown in Example 8 below.
[0134] FIG. 4 is a flow chart illustrating the steps in this
example.
Example 8
[0135] Measurement of Suture Strength
[0136] The suture strength of the adhesion preventing membranes
prepared in Examples 6 and 7 were measured. As control samples
Goretex pericardium (manufactured by Goretex Co.: Goretex EPTFE
Patch II (sheet for pericardium)), porcine extracted pericardium,
and porcine extracted cerebral dura mater were used. The porcine
extracted pericardium and extracted cerebral dura mater were
extracted from an about 20 kg pig by an extraction operation under
anesthesia and then, after extraction of each membrane, immersed in
physiological saline and immediately measured in a fresh state.
[0137] The measurement method was as follows. First, sample
membranes and control membranes were all cut out as plate-like
sections of 1 cm.times.2.5 cm and in a central part of each
membrane at a distance of 5 mm from an end in the direction of a
longer side a suture (4-0 proline thread, manufactured by ETHICON,
INC.) was passed and bound to form a ring. The section to which a
suture was bound was immersed in physiological saline for 30
minutes and then taken out quickly, followed by measuring its
tensile strength using a tensile strength meter (Autograph S-500D,
manufactured by Shimadzu Seisakusho Co., Ltd.). The measurement was
carried out under conditions where the end opposite to the end in
which the suture was passed was fixed to a distance of about 10 mm
from the end, and the ring-like suture at one end was engaged with
a hook for measurement, which was pulled at a constant speed of 10
mm/minute to carry out the measurement. In this case, a change in
strength until the section was cut by the 4-0 proline thread or the
proline thread departed from the section was measured. Among the
recorded strength values, the highest value was defined as a suture
strength (N: Newton) of the adhesion preventing membrane of the
present invention.
[0138] The results are shown in Table 4. TABLE-US-00004 TABLE 4
Goretex Porcine Porcine peri- peri- cerebral Example Example
cardium cardium dura mater 6 7 Measured 8.5 4.0 8.3 8.5 8.8 value
(N)
[0139] As can be seen from Table 4, the adhesion preventing
membrane of the present invention is equivalent to Goretex
pericardium (manufactured by Goretex Co.: Goretex EPTFE Patch II
(sheet for pericardium)) in suture strength, and superior to
porcine extracted pericardium and porcine cerebral dura mater.
Example 9
[0140] Implant Test
[0141] The adhesion preventing membrane obtained in Example 6 was
implanted in the back muscle of rabbits (n=8) and tissue reaction
was observed with naked eyes and using an optical microscope to
evaluate its biocompatibility.
[0142] The implanted sample used was obtained by cutting the
adhesion preventing membrane obtained in Example 6 to a size of 1.5
mm.times.10 mm. As a control a high density polyethylene plate was
used cut to the same size as the sample. The control was subjected
to ethylene oxide gas sterilization before use. The sample membrane
was used for the implanting test after sterilization by irradiation
with 25 kGy .gamma. rays.
[0143] For implanting, first a rabbit (body weight about 2.5 kg to
3.0 kg) was subjected to ordinary inhalation anesthesia and then
the control and the sample were implanted aseptically so that they
sandwiched the back spine of the rabbit such that the control was
on the left hand side and the sample was on the right hand side of
the back spine of the rabbit. The implanting method was such that a
sterilized 15 gauge syringe punctured obliquely the surface of skin
at an angle of about 30 degrees, and the sample membrane and
control were pushed out, thus implanting them in the muscle of
rabbit. After this, four rabbits were used after 1 week and another
four rabbits were used after 4 weeks from the implanting as objects
of observation.
[0144] At each observation time, only two out of the four rabbits
were incised at the implanted part under anesthesia and observation
of the implanted portion and peripheral tissues was made visually
centered on an inflammatory reaction, etc. The remaining two
rabbits were sacrificed with excessive anesthesia and after the
peripheral tissue containing the implanted portion was extracted,
ordinary formalin fixation was conducted and then a section was
prepared, which was observed under a microscope.
[0145] From the results of these observations, the sample membrane
showed no significant inflammatory reaction, etc. as compared with
the control at any observation time for all rabbits, thus revealing
that the adhesion-preventing membrane obtained by the present
invention has good biocompatibility. In the case where 4 weeks
elapsed from the implanting, it was observed that the sample
membrane was decomposed and absorbed.
Example 10
[0146] Study of Adhesion Preventing Effect
[0147] Ten rats (body weight 250 g to 300 g) were divided into two
groups each consisting of 5 rats, one group being a control and the
other a sample group which used the adhesion-preventing membrane
prepared in Example 6. For each of the control group and sample
group, the rats were narcotized intramuscularly and thereafter the
narcotized state was retained by inhalation anesthesia. For the
control group, the rats were incised at the abdomen under
anesthesia to expose the cecum and then the chorion of a size of
about 5 mm square was peeled off. The abdominal portion
corresponding to the cecum chorion was peeled off similarly and an
adhesion model in which the injured surface of cecum and the
injured abdominal surface served as connection surfaces was
prepared. Thereafter, for the control group, the abdomen was
stitched without any further treatment.
[0148] On the other hand, for the sample group, an adhesion model
was prepared in the same manner as the control group and thereafter
the injured cecum surface was covered with the adhesion preventing
membrane prepared in Example 6 and fixed. The size of fixed
adhesion preventing membrane was on the order of about 10
mm.times.10 mm and the membrane was sutured and fixed at the four
corners thereof being lightly hung on the intestinal tract with a
suture (5-0 bicryl thread). For both the sample group and the
control group, the rats were reoperated after 4 weeks for celiotomy
to visually observe the respective states of adhesion.
[0149] The degree of adhesion upon visual observation was judged
based on the criteria in Table 2 above and assigned score to
comparatively evaluate the sample group and control group. Rank 3
or higher was adopted for concluding that adhesion occurred.
[0150] As a result of comparative study between the sample group
and the control group based on these criteria, there was in the
sample group no example case in which adhesion was observed while
in the control group adhesion at Rank 3 or higher was observed for
all cases. In the sample group, the adhesion preventing membrane
remained at the fixed part but did not move to other parts for
almost all of the cases so that it served to separate the injured
surfaces from each other. Further, the adhesion preventing membrane
which remained was carefully peeled off and the injured surface of
the cecum was visually observed. As a result, it was observed that
the injured surface healed. Detailed evaluation results with
respect to the adhesion preventing effect are as shown in Table 5
below. Thus, it was shown that the adhesion preventing membrane of
the present invention is effective in adhesion preventing effect
and tissue regeneration effect. TABLE-US-00005 TABLE 5 Control
group Sample group Average score 3 0.4 Number of adhesion confirmed
5 cases 0 case
[0151] As will be apparent from Table 5, the adhesion preventing
membrane of the present invention has a cover layer of gelatin or
hyaluronic acid over its surface so that it is excellent in
adhesion preventing effect and tissue regenerating effect.
[0152] The adhesion preventing membrane of the present invention is
excellent in suture strength, biocompatibility, induction of tissue
regeneration and further has an adhesion-preventing property.
Therefore, it is useful as an artificial biomembrane capable of
preventing adhesion of an injured part or a bleeding part after
operation, etc. or of adhesion of such parts with a normal
part.
* * * * *