Suitability of cellulose molecular dialysis membrane for bioartificial pancreas: in vitro biocompatibility studies

The success of immunoisolation devices for islet transplantation depends on the properties and biocompatibility of semipermeable immunobarrier membranes. In the present study, we have evaluated the in vitro biocompatibility of the cellulose membrane Spectra/Por 2 (MW no larger than 12- 14,000) for its possible application in islet immunoisolation. The membrane was found to be hydrophilic (octane contact angle: 153.2+/-0.66 degrees) and exhibited decreased protein adsorption. It showed mechanical stability after 1 month of storage in PBS (pH 7.4) with tensile strength, percent elongation, and Young's modulus of 88.88 MPa, 36.22, and 291.8 MPa, respectively. It allowed regulated transport of glucose and insulin in an in vitro diffusion assay. The high viability of NIH3T3 fibroblasts and the inability of lymphocytes to proliferate in vitro on exposure to the membrane leach-out products suggested its noncytotoxic and nonimmunogenic nature. Macrophages, when cultured on membranes, did not show increased expression of inflammatory surface marker such as CD11b/CD18, CD45, CD14, and B 7.2. Image analysis studies showed integrity and intact morphology of mouse islets cultured on and inside the membranes with high viability (91%, 89.7%). These islets also retained their functionality, as judged by insulin secretion. The present study provides sufficient documentation to consider cellulose molecular dialysis membrane Spectra/Por 2 (MW no larger than 12-14,000) as a potential candidate for immunoisolation of islets.