TRACER TECHNIQUE TO MEASURE IN-VIVO CHEMICAL-TRANSPORT RATES WITHIN AN IMPLANTABLE CELL TRANSPLANTATION DEVICE

An in vivo tracer technique that uses radiolabeled inulin as the trace r molecule has been developed to assess the rate of chemical transport between the cell transplantation chamber of an implantable bioartific ial device and the host's circulatory system, The device considered he re employs site-directed neovascularization of a porous matrix to indu ce capillary growth adjacent to an immunoisolated cell implantation ch amber. This device design is being investigated as a vehicle for thera peutic cell transplantation, with the advantages that it allows the ce lls to perform their therapeutic function without the danger of immune rejection and it avoids damaging contact of blood flow with artificia l surfaces, A pharmacokinetic model of the mass transport between the implantation chamber, the vascularized matrix, and the body has been d evised to allow proper analysis and understanding of the experimental tracer results. Experiments performed in this study have been principa lly directed at evaluation of the tracer model parameters, but results also provide a quantitative measure of the progression of capillary g rowth into a porous matrix, Measured plasma tracer levels demonstrate that chemical transport Fates within the implanted device increase wit h the progression of matrix vascular ingrowth, Agreement between the f itted model curves and the corresponding measured concentrations at di fferent levels of capillary ingrowth demonstrate that the model provid es a realistic representation of the actual capillary-mediated transpo rt phenomena occurring within the device.