Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Implant or insert
Reexamination Certificate
1998-02-27
2001-03-13
Kulkosky, Peter F. (Department: 1615)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Implant or insert
C424S487000, C424S486000, C435S180000
Reexamination Certificate
active
06200589
ABSTRACT:
TECHNICAL FIELD
The present invention generally relates to implantable biological devices. More particularly, the present invention relates to biological devices that can encase cells and selectively regulate the passage of biological material in and out of the device. Specifically, the device is a geometric structure of a polymeric amphiphilic network having encased therein biological cells.
BACKGROUND OF THE INVENTION
Graft rejection of biological cells, organs, devices and the like that are placed into living organisms severely limits many medical treatments. For example, pancreatic transplantation, which is the only treatment of Type I diabetes that is capable of consistently inducing insulin independence and normalizing blood glucose is severely limited by graft rejection and the need for toxic immunosuppression.
One theory advanced to overcome the limitation caused by graft rejection is to place pancreatic islets in an immuno protected device that would allow the diffusion of insulin generated by the islet cells. Heretofore in the art, the term immunoisolation has been used to describe the state of being protected from immune rejection by enclosure within a membrane. It has been advanced that semipermeable membranes would be highly desirous for this task.
Semipermeable membranes are known. For example, Kennedy et al. in U.S. Pat. Nos. 4,942,204 and 5,073,381 teach amphiphilic networks that are employed as pharmaceutical carries capable of controlled drug release. More specifically, the amphiphilic networks are copolymeric compositions having hydrophobic and hydrophilic segments. Although these networks are synthesized for controlled drug release devices, implants for enzyme immobilization, artificial arteries, blood-contacting applications, and various implantable reservoirs for drugs and metabolites for veterinary and human applications, the amphiphilic networks taught therein are not synthesized to prevent the diffusion of molecules, and moreover, prevent the diffusion of molecules having a certain molecular weight while allowing the diffusion of molecules of a different molecular weight. In other words, a need still exists to synthesize and employ a semipermeable membrane to create an implantable device capable of immunoisolating cells.
SUMMARY OF INVENTION
It is therefore, an object of the present invention to provide implantable biological devices that immunoisolate foreign biological matter.
It is another object of the present invention to provide implantable biological devices that are biocompatible and hemocompatible.
It is yet another object of the present invention to provide implantable biological devices that can encase biological matter or cells and selectively regulate the passage of biological material in and out of the device.
It is another object of the present invention to provide implantable biological devices that can be implanted in the body by employing a relatively non-invasive medical procedure.
It is still another object to provide a method for the treatment of diabetes by providing to a diabetic an implantable biological device having encased therein pancreatic islets that are immunoisolated.
At least one or more of the foregoing objects, together with the advantages thereof over the known art relating to implantable biological devices, which shall become apparent from the specification which follows, are accomplished by the invention as hereinafter described and claimed.
In general the present invention provides a biological device comprising a semipermeable membrane formed into a geometric shape capable of encapsulating biological cells and capable of immunoisolating the biological cells upon introduction into the body, the semipermeable membrane comprising an amphiphilic copolymer network having hydrophobic segments and hydrophilic segments, wherein the hydrophobic segments include polyolefins capped with radicals selected from the group consisting of acryloyl groups, methacryloyl groups and mixtures thereof and wherein the hydrophilic segments include polyacrylates derived from an acrylate selected from the group consisting of formulas (II), (III) and (IV)
where R
2
is hydrogen or methyl, R
3
is an alkylene group having from about 2 to about 4 carbon atoms, and R
4
and R
5
may be the same or different and selected from the group consisting of hydrogen and an alkyl radicals having from 1 to about 4 carbon atoms.
The present invention also includes a method for a method of treating diabetes comprising the step of implanting in a living organism at least one biocompatible device having encased therein pancreatic islet cells, the device comprising a semipermeable membrane formed into a geometric structure that encases and immunoisolates the islet cells, wherein the semipermeable membrane is a amphiphilic copolymer network having hydrophobic segments and hydrophilic segments, the hydrophobic segments including polyolefins capped with radicals selected from the group consisting of acryloyl groups, methacryloyl groups and mixtures thereof and the hydrophilic segments include polyacrylates derived from an acrylate selected from the group consisting of formulas (II), (III) and (IV)
where R
2
is hydrogen or methyl, R
3
is an alkylene group of about 2 to about 4 carbon atoms, and R
4
and R
5
may be the same or different and each is hydrogen or an alkyl radical of 1 to about 4 carbon atoms.
The present invention further includes a method of encapsulating and immunoisolating cells using a semipermeable membrane comprising an amphiphilic copolymer network having hydrophobic segments and hydrophilic segments, wherein the hydrophobic segments include polyolefins capped with radicals selected from the group consisting of acryloyl groups, methacryloyl groups and mixtures thereof and wherein the hydrophilic segments include polyacrylates derived from an acrylate selected from the group consisting of formulas (II), (III) and (IV)
where R
2
is hydrogen or methyl, R
3
is an alkylene group having from about 2 to about 4 carbon atoms, and R
4
and R
5
may be the same or different and selected from the group consisting of hydrogen and an alkyl radicals having from 1 to about 4 carbon atoms; and wherein the semipermeable membrane is impermeable to molecules having a molecular weight greater than about 50,000.
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“Maintenance of Normogylcemia in Diabetic Mice by Subcutaneous Xenografts of Encapsulated Islets” by Lacy et al.,Science Journal, vol. 254, pp. 1782-1784, Sep. 27, 1991.
“Application of AN69 Hydrogel to Islet Encapsulation: Evaluation in the Streptozotocin-Induced Diabetic Rat Model” by Prevost et al. Transplantation Proceedings, vol. 27, No. 6, pp. 3393-3395, Dec. 1995.
“Novel Synthetic Membranes for Immunoisolation of Islet Cells” by Shamlou et al., Abstract Only, Jun., 1996 poster presentation.
“Amphiphilic networks: II. Biocompatibility and Controlled Drug Release of Poly[isobutylene-co-2(dimethylamino)ethyl methacrylate]” by Chen et al.,Journal of Biomedical Materials Research, vol. 23, 1327-1342 (1989).
“Tailoring Polymers for Biological Uses” by J.P. Kennedy.
S. Shamlou et al J. of Biomed. Materials Res., vol. 35 157-163 (1997).
Kennedy Joseph P.
Levy Richard P.
Shamlou Shahram
Kulkosky Peter F.
Renner Kenner Greive Bobak Taylor & Weber
The University of Akron
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