Biocompatibility of Complementary Polymer/Epoxy-Sterilant Combinations for an Implantable Bioartificial Kidney Bioreactor
By: Eleazar DeAlmeida, Alonso Torres, Ana Santandreu, Caressa Chen, Eun Jung Kim, William H. Fissell, and Shuvo Roy
Department: Cellular & Molecular Biology
Faculty Advisors: Dr. Shuvo Roy and Alonso Torres (UCSF)
Implantable medical devices undergo rigorous testing to demonstrate proper functionality and biocompatibility. Devices are meticulously processed and sterilized to ensure the materials, fabrication/assembly process, and sterilization methods do not adversely impact the functionality and biocompatibility of the final product. Our lab is fabricating a bioartificial kidney bioreactor that combines human renal proximal tubule epithelial cells (hRPTEC) with Silicon Nanopore Membranes (SNM) to recapitulate key functions of the renal nephron. Currently, the device requires biocompatible adhesives to bond a polycarbonate bioreactor housing to an SNM stack. In this study, we investigated three ISO10993-certified adhesive materials and their capacity for sustained bonding upon direct and indirect exposure to hRPTEC under different sterilization conditions.
In the first experiment, cells (100,000 cells/cm2) were seeded directly on 48-well suspension plates and cultured for three days in the supernatant media exposed to the adhesive to investigate cytotoxicity. In the second experiments, cells were seeded directly on the sterilized epoxy to study the impact on cell adhesion. We used 3.5% (v/v) glutaraldehyde and 70% (v/v) ethanol as sterilants. The adhesives used included polydimethylsiloxane (PDMS) (Dow Corning Sylgard 184), EP30MED (MasterBond), and MED-302-3M (EPO-TEK). PrestoBlue Cell Viability Reagent (Thermo Fisher Scientific) and Live/Dead Cell Imaging Kit (Thermo Fisher Scientific) were used to evaluate cell metabolic activity and viability, respectively, after three days in experimental conditions. We hypothesized that 3.5% glutaraldehyde would provide excellent cell metabolic activity across all adhesive-sterilant experimental groups.
MED-302-3M performed the best with 70% ethanol and provided the most favorable results. Cell metabolic activity was similar to controls when exposed to epoxy supernatant and 3x higher than control when the cells were in direct contact with the epoxies. Future studies evaluating alternative candidates will be performed to improve device integrity and safety. Our results will inform future kidney bioreactor development as it is scaled toward clinical implementation.