U.S. patent application number 11/105963 was filed with the patent office on 2007-01-04 for system and method for forming bioengineered tubular graft prostheses.
Invention is credited to Ginger Abraham, Kristen Billiar, Maury D. Cosman, Ryan Mercer, Bruce Miller.
Application Number | 20070003633 11/105963 |
Document ID | / |
Family ID | 23343450 |
Filed Date | 2007-01-04 |
United States Patent
Application |
20070003633 |
Kind Code |
A1 |
Abraham; Ginger ; et
al. |
January 4, 2007 |
System and method for forming bioengineered tubular graft
prostheses
Abstract
An apparatus for forming a tube construct from a planar sheet
matrix includes a stand supporting two opposing mounts and spanning
between the opposing mounts are a mandrel, a porous rod, and a
spring-loaded roller held in parallel arrangement; a guide for
aligning and engaging the mandrel on the opposing mounts; and a
means for imparting a tangential force on the planar sheet matrix
to prevent wrinkling. The porous rod has a lumen running its length
and has pores that communicate between the lumen of the porous rod
through to the surface of the rod for water to uniformly pass
through. The spring-loaded roller runs along the length of the
porous rod creating a line of contact between the roller and the
mandrel. The mandrel is contacted with a planar sheet of matrix and
is rotated such that successive portions of the matrix contact the
porous rod and become lightly moistened by the water passing
through the pores of the porous rod and become wrapped around the
mandrel to form a tube construct.
Inventors: |
Abraham; Ginger; (Hanover,
MA) ; Cosman; Maury D.; (Medfield, MA) ;
Billiar; Kristen; (Jamaica Plain, MA) ; Mercer;
Ryan; (Richmond, CA) ; Miller; Bruce; (Quincy,
MA) |
Correspondence
Address: |
KRAMER LEVIN NAFTALIS & FRANKEL LLP;INTELLECTUAL PROPERTY DEPARTMENT
1177 AVENUE OF THE AMERICAS
NEW YORK
NY
10036
US
|
Family ID: |
23343450 |
Appl. No.: |
11/105963 |
Filed: |
April 14, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10325444 |
Dec 19, 2002 |
6978815 |
|
|
11105963 |
Apr 14, 2005 |
|
|
|
60342831 |
Dec 21, 2001 |
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Current U.S.
Class: |
424/551 |
Current CPC
Class: |
A61F 2/062 20130101;
B29C 53/562 20130101 |
Class at
Publication: |
424/551 |
International
Class: |
A61K 35/38 20060101
A61K035/38; A61K 35/37 20060101 A61K035/37 |
Claims
1. A method for forming a tube construct from a planar sheet
matrix, comprising: flagging a planar sheet matrix by aligning a
mandrel along one edge of the sheet and contacting it to the sheet
so that the planar sheet matrix and the mandrel adhere, rolling the
flagged planar sheet matrix around the mandrel while maintaining
even tension on the sheet and smoothing out bubbles or creases
using a roller as it is rolled onto the mandrel until the sheet
contacts and overlaps itself to a degree to form a bonding region
that keeps the tissue in a tubular form.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a Divisional Application of U.S. patent
application Ser. No. 10/325,444, filed Dec. 19, 2002, which claims
the benefit of U.S. Provisional Application Ser. No. 60/342,831
entitled "SYSTEM AND METHOD FOR FORMING BIOENGINEERED TUBULAR GRAFT
PROSTHESES" filed on Dec. 21, 2001, which is incorporated herein by
reference in its entirety.
FIELD OF THE INVENTION
[0002] This invention is in the field of tissue engineering. The
invention is directed to a system and a method for preparing
bioengineered graft prostheses prepared from cleaned tissue
material derived from animal sources. The bioengineered graft
prostheses made using the invention are tubular, of small diameter,
and have a uniform geometry along their entire length. The
bioengineered graft prostheses are used for implantation, repair,
or for use in a mammalian host.
BACKGROUND OF THE INVENTION
[0003] The present invention overcomes the difficulties in forming
a fine gauge tube of uniform geometry from processed tissue matrix
or reconstituted matrix.
SUMMARY OF THE INVENTION
[0004] The invention is a system for fabricating tubular constructs
from planar sheet-like processed tissue matrices or reconstituted
matrices. The system comprises two devices: a flagging device and a
rolling device. Each device accommodates a mandrel on which the
tubular construct is formed. First, a matrix is flagged on the
mandrel using the flagging device. Second, the matrix is then
rolled onto the mandrel using the rolling device.
[0005] Therefore, the method of the invention comprises: (a) a
method for flagging a sheet of processed tissue matrix by aligning
a mandrel along one edge of the sheet and contacting it to the
sheet so that the sheet and the matrix adhere, and (b) rolling the
flagged sheet around the mandrel while maintaining even tension on
the sheet and smoothing out bubbles or creases as it is rolled onto
the mandrel. Rolling continues until the sheet contacts and
overlaps itself to a degree. The overlap is the bonding region that
keeps the tissue in a tubular form.
BRIEF DESCRIPTION OF THE FIGURES
[0006] FIG. 1 shows a view of the flagging apparatus of the
invention.
[0007] FIG. 2 shows a side cross-sectional view of the rolling
apparatus of the invention.
[0008] FIG. 3 shows a three-dimensional view of the rolling
apparatus of the invention.
DETAILED DESCRIPTION
[0009] The invention is directed toward a system and methods for
making tubular-shaped tissue engineered prostheses from thin planar
materials where the system and methods do not require adhesives,
sutures, or staples to bond the tissue in a tubular form and
consequently maintain the bioremodelability of the prostheses.
[0010] Advantages provided by the invention are that the apparatus
can make constructs faster and more consistently than if made
manually. The system devices of the invention aid in even
circumferential tensioning and radial compression of the tissue
which smoothes out air or water bubbles or creases that can occur
under the mandrel or between the layers of the tube. Because the
constructs are used as medical devices, minimal variations can
potentially affect the functional performance of the constructs
when implanted in a patient.
[0011] The terms "processed tissue matrix" and "processed tissue
material" mean native, normally cellular tissue that has been
procured from an animal source, preferably a mammal, and
mechanically cleaned of attendant tissues and chemically cleaned of
cells, cellular debris, and rendered substantially free of
non-collagenous extracellular matrix components. The processed
tissue matrix, while substantially free cellular debris, maintains
much of its native matrix structure, strength, and shape. Preferred
compositions for preparing the bioengineered grafts of the
invention are animal tissues comprising collagen, including, but
not limited to: intestine, fascia lata, pericardium, dura mater,
and other flat or planar structured tissues that comprise a fibrous
tissue matrix. The planar structure of these tissue matrices makes
them able to be easily manipulated and assembled using the devices
and methods of the invention. A more preferred composition for
preparing the bioengineered grafts of the invention is an
intestinal collagen layer derived from the tunica submucosa of
small intestine. Suitable sources for small intestine are mammalian
organisms such as human, cow, pig, sheep, dog, goat, or horse while
small intestine of pig is the preferred source. The most preferred
composition for preparing tubular prostheses using the invention is
a processed intestinal collagen layer derived from the tunica
submucosa of porcine small intestine. To obtain the processed
intestinal collagen layer, the small intestine of a pig is
harvested and attendant mesenteric tissues are grossly dissected
from the intestine. The tunica submucosa is preferably separated,
or delaminated, from the other layers of the small intestine by
mechanically squeezing the raw intestinal material between opposing
rollers to remove the muscular layers (tunica muscularis) and the
mucosa (tunica mucosa). The tunica submucosa of the small intestine
is tougher than the surrounding tissue, hence the rollers squeeze
the more friable components from the submucosa. In the examples
that follow, the tunica submucosa was mechanically harvested from
porcine small intestine using a Bitterling gut cleaning machine and
then chemically cleaned to yield a cleaned tissue matrix as
described in U.S. Pat. No. 5,993,844, the disclosure of which is
incorporated herein by reference. This mechanically and chemically
cleaned intestinal collagen layer is herein referred to as "ICL".
ICL is used to prepare tubular constructs that are used as
bioengineered medical devices such as those described in
International PCT Application Publication Nos. WO 95/22301, WO
99/62424, WO 99/62425, and WO 99/62427, the teachings of which are
incorporated herein by reference.
[0012] The terms, "reconstituted matrix" and "reconstituted
material", mean animal-derived or cell-derived matrix components
that have been extracted and purified from either tissues or cell
cultures. The matrix may be formed from solubilized matrix
components, principally collagen such that the matrix has
tissue-like properties with regard to structure and physical
properties. The reconstituted matrix may be highly purified and may
have other components added to the matrix when the matrix is
reformed. Other suitable collagenous tissue sources or other native
tissue, reconstituted matrix sheets, or synthetic materials with
the same flat sheet structure may be identified by the skilled
artisan in other animal sources.
[0013] In the description of the devices and methods of the
invention, and in the examples that follow, a sheet-like material,
preferably either a processed tissue matrix or a reconstituted
matrix, is used to make the tubular constructs. While not intending
to be so limited but for simplicity in illustration of the
apparatus and methods of the invention, and to describe the most
preferred embodiment, the fabrication of a tube from a sheet of ICL
will be described.
[0014] In the first aspect of the system of the invention, a
flagging device is employed. Flagging introduces the ICL to be
tubulated to a mandrel on which the tubular construct is formed.
Referring to FIG. 1, shown is the flagging device of the invention.
The flagging device 10 comprises a base platform 12 with legs 14.
The platform incorporates a hollow chuck 16 with a plurality of
machined holes 18 on its top facing surface, that communicate
between the inside and outside of the chuck, and a port 20. The
port 20 is connected to a vacuum source. Running along the surface
of the platform 12 and along one edge of the hollow chuck 16 is a
groove 22. The groove 22 accommodates a cylindrical mandrel 24 that
is covered with an elastic sleeve and supported at each end by
mandrel holders 25. The starting material, either a processed
tissue matrix, such as ICL, or a reconstituted matrix, has a
sheet-like geometry, preferably with at least one straight edge,
more preferably rectangular. The ICL is dried in air before use.
The sleeve on the mandrel is wetted with sterile water. The ICL is
placed on the top surface of the platform with one edge of the
material aligned along the center of the mandrel. The vacuum source
is turned on to pull air through the machined holes 18 in the top
of the hollow chuck 16. Because the vacuum is on, the ICL is held
flat and even against the platform. The material is then contacted
to the sleeve on the mandrel by raising the mandrel holders 25 so
that only one edge of the ICL is contacted to the mandrel and is
moistened by the water on the sleeve. The ICL, sticky when
moistened, adheres to the mandrel. The ICL is allowed to dry to a
point where it will remain adhered to the mandrel when the mandrel
is lifted from the groove in the platform. A rectangular piece of
ICL, when adhered to the mandrel along one edge, will resemble a
flag.
[0015] The second aspect of the system of the invention is a device
for forming a tube from flagged ICL. Referring to FIG. 2, shown is
the rolling device of the invention. The rolling device 50
comprises a stand 51 that supports two opposing mounts 52. Passing
between and held in parallel arrangement by the opposing mounts are
a porous tubular ceramic rod 55, a hollow chuck 57, and a
spring-loaded roller 60. The ceramic rod 55 has a lumen running its
length with one end of the ceramic rod is closed and the other end
extending beyond the mount and open to serve as a port. Pores
communicate between the lumen of the rod through to the surface for
water to uniformly pass through. Above the level of the ceramic rod
a hollow chuck 57 with machined holes that communicate between the
interior and exterior of the chuck. The hollow chuck has a
plurality of holes on the face towards the roller 60 and a port at
one end for the attachment of a vacuum source. The spring-loaded
roller 60 runs along the length of the ceramic rod creating a line
of contact between the roller 60 and the ICL on mandrel 24. In each
mount, the spring-loaded roller 60 is contacted by an end of a
perpendicular rod 62 loaded by a coil spring contained in the
mount. The perpendicular rod 62 passes through the mount via an
extender rod 67. The perpendicular rods 62 can be disengaged from
the roller 60 by engaging a solid bar 68 between the ends of the
extender rods 67 and the spring housings 64. In each of the
opposing mounts is a guide member 70 having an L-shaped groove
where the top of the guide is open to accommodate one end of the
mandrel and the bottom of the guide aligns the mandrel to engage it
against the ceramic rod. When the spring-loaded roller is
disengaged, the guides are open for the insertion of a mandrel
between the opposing mounts. When the guides are loaded with a
mandrel and the spring-loaded roller is engaged, the roller presses
against the mandrel on one side such that the mandrel contacts the
ceramic rod on the opposite side.
[0016] Before loading the guide with a mandrel, the vacuum and
water sources are activated so that air is pulled through the
machined holes in the hollow chuck to the interior of the chuck and
the water is slowly passing from the lumen of the ceramic tube to
its surface. The ends of the mandrel with the flagged ICL are
placed in the guides with the free end of the flagged ICL upright
and away from the rolling device. The spring-loaded roller is
actuated against the mandrel forcing the mandrel to contact the
porous ceramic rod. The mandrel is then rotated to wrap the ICL
around the mandrel. The ICL is held taught by the vacuum from the
hollow chuck 57. As the mandrel is rotated, successive portions of
the ICL contact the porous ceramic rod and are lightly moistened by
the water flowing out of the ceramic rod. The mandrel is rotated
until the entire piece of ICL is wrapped around the mandrel.
[0017] The bioengineered constructs produced by the devices and
methods of the invention are tubular in shape and may be formed to
any length or thickness. The length of the construct is limited
only by the size of the devices of the system and the length of the
mandrel and the longest dimension of a sheet of material. The
thickness of the construct may be chosen so that the final
construct is one or more layers, depending on the number of times
the mandrel that holds the sheet of material is rotated, with the
limitation being the maximum thickness that the apparatus can
manage. For a single layer construct, there will be some overlap
where a bonding region is formed to maintain the tubular shape of
the final construct. The diameter of the tube is determined by the
diameter of the mandrel chosen.
[0018] To form a tubular construct, a mandrel is chosen with a
diameter measurement that will determine the final inner diameter
of the formed tube construct. The mandrel is preferably cylindrical
or oval in cross section and made of glass, stainless steel,
ceramic, or plastic and preferably of a nonreactive, medical grade
composition. The number of layers intended for the tubular
construct to be formed corresponds with the number of times an ICL
is wrapped around a mandrel and over itself. The number of times
the ICL can be wrapped depends on the width of the processed ICL
sheet. For a two layer tubular construct, the width of the sheet
must be sufficient for wrapping the sheet around the mandrel at
least twice. Similarly, the length of the mandrel will dictate the
length of the tube that can be formed on it. For ease in handling
the construct on the mandrel, the mandrel should be longer than the
length of the construct so the mandrel, and not the construct being
formed, is contacted when handled.
[0019] It is preferred that the mandrel is provided with an elastic
sleeve. The sleeve may be a nonreactive, medical grade quality,
elastomeric material. While a tubular ICL construct may be formed
directly on the mandrel surface, the sleeve facilitates the removal
of the formed tube from the mandrel and does not adhere to, react
with, or leave residues on the ICL. To remove the formed construct,
the sleeve may be pulled off from one end of the mandrel and carry
the construct from the mandrel with it. Because the processed ICL
only lightly adheres to the sleeve and is more adherent to other
ICL layers, fabricating ICL tubes is facilitated as the tubulated
construct may be removed from the mandrel without stretching or
risking damage to the tube construct. In the most preferred
embodiment, the elastic sleeve comprises KRATON.RTM. (Shell
Chemical Company), a thermoplastic rubber composed of
styrene-ethylene/butylene-styrene copolymers with a very stable
saturated midblock.
[0020] For illustration, a two-layer tubular construct with a 4 mm
inner diameter and an additional 20% overlap is formed on a mandrel
having about a 4 mm diameter. The mandrel is provided with a
KRATON.RTM. sleeve approximately as long as the length of the
mandrel and longer than the construct to be formed on it. A sheet
of ICL is trimmed so that the width dimension is about 28 mm and
the length dimension may vary depending on the desired length of
the construct. In the sterile field of a laminar flow cabinet, the
ICL is then formed into an ICL collagen tube by the following
process. The ICL is moistened along one edge and is aligned with
the sleeve-covered mandrel and, leveraging the adhesive nature of
the ICL, it is "flagged" along the length of the sleeve-covered
mandrel and dried in position for at least 10 minutes. The flagged
ICL is then hydrated and wrapped around the mandrel and then over
itself one full revolution plus 20% of the circumference, for a
120% total overlap, to serve as a bonding region and to provide a
tight seam. To obtain a tubular construct with the mucosal side of
the ICL as the lumen of the formed construct, the mucosal side of
the ICL is moistened along one edge, flagged on the mandrel, and
wrapped so that the mucosal side of the ICL faces the mandrel.
Using the method above, a tubular construct can be made with the
mucosal side of the ICL as the lumen or, alternatively, the serosal
side of the ICL as the lumen by orienting the ICL appropriately
during flagging.
[0021] For the formation of single layer tubular construct, the ICL
must be able to wrap around the mandrel one full revolution and at
least about a 5% additional revolution as an overlap to provide a
bonding region that is equal to about 5% of the circumference of
the construct. For a two-layer construct, the ICL must be able to
wrap around the mandrel at least twice and preferably an additional
5% to 20% revolution as an overlap. While the two-layer wrap
provides a bonding region of 100% between the ICL surfaces, the
additional percentage for overlap ensures a minimum of 2 layers
throughout the graft. For a three-layer construct, the ICL must be
able to wrap around the mandrel at least three times and preferably
an additional 5% to 20% revolution as an overlap. The construct may
be prepared with any number of layers depending on the
specifications for a graft required by the intended indication.
Typically, a tubular construct will have 10 layers or less,
preferably between 2 to 6 layers and more preferably 2 or 3 layers
with varying degrees of overlap. During and after wrapping, any air
bubbles, folds, and creases are smoothed out from under the
material and between the layers.
[0022] The layers of the wrapped ICL are then bonded together by
dehydrating them while in wrapped arrangement on the sleeve-covered
mandrel. While not wishing to be bound by theory, dehydration
brings the extracellular matrix components, such as collagen
fibers, in the layers together when water is removed from the
spaces between the fibers in the matrix. Dehydration may be
performed in air, in a vacuum, or by chemical means such as by
acetone or an alcohol such as ethyl alcohol or isopropyl alcohol.
Dehydration may be done to room humidity, normally between about
10% RH to about 50% RH. Dehydration may be performed by placing the
mandrel with the ICL layers into the oncoming airflow of a laminar
flow cabinet for at least about 1 hour up to 24 hours at ambient
room temperature, approximately 20.degree. C., and at room
humidity. At this point the wrapped dehydrated ICL constructs may
be then pulled off the mandrel via the sleeve or left on for
further processing. The constructs may be rehydrated in an aqueous
solution, preferably water, by transferring them to a room
temperature container containing rehydration agent for at least
about 10 to about 15 minutes to rehydrate the layers without
separating or delaminating them. The thus formed collagen tube
construct is then used to form a prosthesis, preferably a
bioremodelable prosthesis.
[0023] The constructs are then preferably crosslinked together by
contacting them with a crosslinking agent, preferably a chemical
crosslinking agent that preserves the bioremodelability of the ICL
material. As mentioned above, the dehydration brings the
extracellular matrix components of adjacent ICL layers together for
crosslinking those layers of the wrap together to form chemical
bonds between the components and thus bond the layers together.
Alternatively, the constructs may be rehydrated before crosslinking
by contacting an aqueous solution, preferably water, by
transferring them to a room temperature container containing
rehydration agent for at least about 10 to about 15 minutes to
rehydrate the layers without separating or delaminating them.
Crosslinking the bonded prosthetic device also provides strength
and durability to the device to improve handling properties.
Various types of crosslinking agents are known in the art and can
be used such as ribose and other sugars, oxidative agents and
aldehydes. A preferred crosslinking agent is
1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC).
In an another preferred method, sulfo-N-hydroxysuccinimide is added
to the EDC crosslinking agent as described by Staros, J. V.,
Biochem, 21, 3950-3955, 1982. Besides chemical crosslinking agents,
the layers may be bonded together by physical means such as
dehydrothermal (DHT) and ultraviolet (UV) methods or by other
methods such as with fibrin-based glues or medical grade adhesives
including cyanoacrylate, polyurethane, vinyl acetate or polyepoxy.
In the most preferred method, EDC is solubilized in water at a
concentration preferably between about 0.01 mM to about 100 mM,
more preferably between about 0.1 mM to about 10 mM, most
preferably at about 1.0 mM. Besides water, phosphate buffered
saline or (2-[N-morpholino]ethanesulfonic acid) (MES) buffer may be
used to dissolve the EDC. In addition, other agents may be added to
the solution such as acetone or an alcohol may be added up to 99%
v/v in water to modulate the crosslinking. EDC crosslinking
solution is prepared immediately before use as EDC will lose its
activity over time. To contact the crosslinking agent to the ICL,
the hydrated, ICL tubular constructs are transferred to a container
such as a shallow pan and the crosslinking agent gently decanted to
the pan ensuring that the ICL layers are both covered and
free-floating and that no air bubbles are present under or within
the layers of ICL constructs. The pan is covered and the layers of
ICL are treated with crosslinking agent for between about 4 to
about 24 hours after which time the crosslinking solution is
decanted and disposed of.
[0024] Constructs are rinsed in the pan by contacting them with a
rinse agent to remove residual crosslinking agent. A preferred
rinse agent is water or other aqueous solution. Preferably,
sufficient rinsing is achieved by contacting the chemically bonded
constructs three times with equal volumes of sterile water for
about five minutes for each rinse. If the constructs have not been
removed from the mandrels, they may be removed at this point by
pulling the sleeves from the mandrels. The constructs are then
allowed to dry and when dry, the sleeve may be removed from the
lumen of the constructs simply by pulling it out by one of the free
ends.
[0025] In embodiments where the construct will be used as a
vascular graft, the luminal surface of the construct may be
rendered less thrombogenic by applying a deposited collagen layer
or heparin, or both, to the lumen of the formed tube. Heparin can
be applied to the prosthesis by a variety of well-known techniques.
For illustration, heparin can be applied to the prosthesis in the
following three ways. First, benzalkonium heparin (BA-Hep)
isopropyl alcohol solution is applied to the prosthesis by
vertically filling the lumen or dipping the prosthesis in the
solution and then air-drying it. This procedure treats the collagen
with an ionically bound BA-Hep complex. Second, EDC can be used to
activate the heparin and then to covalently bond the heparin to the
collagen fiber. Third, EDC can be used to activate the collagen,
then covalently bond protamine to the collagen and then ionically
bond heparin to the protamine. Many other coating, bonding, and
attachment procedures are well known in the art that could also be
used.
[0026] The following examples are provided to better elucidate the
practice of the present invention and should not be interpreted in
any way to limit the scope of the present invention. Those skilled
in the art will recognize that various modifications can be made to
the methods described herein while not departing from the spirit
and scope of the present invention.
EXAMPLES
Example 1
Method for Making an ICL Tube Construct
[0027] In the sterile field of a laminar flow cabinet, the ICL was
formed into ICL collagen tubes by the following process. Lymphatic
tags were trimmed from the serosal surface of the ICL. The ICL was
blotted with sterile absorbent towelettes to absorb excess water
from the material and then spread on a porous polycarbonate sheet
and dried in the oncoming airflow of the laminar flow cabinet. Once
dry, ICL was cut into 28.5 mm.times.10 cm pieces for a 2 layer
graft with approximately a 20% overlap. To support the ICL in the
formation of the tubes, a cylindrical stainless steel mandrel with
a diameter of about 4 mm was covered with KRATON.RTM., an elastic
sleeve material that facilitates the removal of the formed collagen
tube from the mandrel and does not adhere or react with the
ICL.
[0028] The flagging apparatus of the invention was used to contact
and adhere the edge of a sheet of ICL to a mandrel. The long edge
of the ICL was moistened with sterile water on the sleeve around
the mandrel and adhered to the mandrel and allowed to dry for about
15 minutes to form a "flag".
[0029] The rolling machine of the invention was used to roll a
flagged sheet of ICL around the mandrel to form a tube of ICL. The
ICL was rolled around the mandrel and over itself one complete
revolution. After rolling was complete, air bubbles, folds, and
creases were smoothed out from under the material and between the
layers. The mandrels and rolled constructs were allowed to sit in
the oncoming airflow of the laminar flow cabinet and allowed to dry
for about an hour in the cabinet at room temperature, approximately
20.degree. C.
[0030] Chemical crosslinking solution of either crosslinked 1 mM
EDC or 10 mM EDC/25% acetone v/v in water, in volumes of about 50
mL crosslinking solution per tube, was prepared immediately before
crosslinking. The hydrated ICL tubes were then transferred to
either of two cylindrical vessels containing either crosslinking
agent. The vessel was covered and allowed to sit for about 18.+-.2
hours in a fume hood, after which time the crosslinking solution
was decanted and disposed. ICL tubes were then rinsed three times
with sterile water for about 5 minutes per rinse.
[0031] The crosslinked ICL tubes were then removed from the mandrel
by pulling the Kraton sleeve off the mandrel from one end. Once
removed, the ICL tubes containing the Kraton were allowed to dry
for an hour in a laminar air flow hood. Once dried, the sleeve was
removed from the lumen of each ICL tube by pulling it out from one
end.
[0032] ICL tubes were sterilized in 0.1% peracetic acid at
approximately pH 7.0 overnight according to the methods described
in commonly owned U.S. Pat. No. 5,460,962, the disclosure of which
is incorporated herein in its entirety. The ICL tubes were then
rinsed of sterilization solution three times with sterile water for
about 5 minutes per rinse. The peracetic acid sterilized ICL
collagen tubes were then dried in a laminar flow hood and then
packaged in sterile 15 mL conical tubes until implantation.
[0033] Although the foregoing invention has been described in some
detail by way of illustration and example for purposes of clarity
and understanding, it will be obvious to one of skill in the art
that certain changes and modifications may be practiced within the
scope of the appended claims.
* * * * *