Comparative studies of in vitro and in vivo function of three different shaped bioartificial pancreases made of agarose hydrogel.

Various kinds of bioartificial pancreas (BAP) have been developed in the past. There have been many disputes about the advantages and disadvantages of each BAP. However, little attention has been paid to the shape of the devices. In this study, three different shaped BAPs were made of the same material, agarose hydrogel. These are microbead-, rod- and disc-shaped BAPs, which are comparable to microcapsules, hollow fibre diffusion chambers and disc-shaped diffusion chambers, respectively, in shape. Their performances were studied by in vitro culture, mathematical simulations and in vivo implantation into diabetic animals. The islets in the BAPs could survive and release insulin for more than 100 d regardless of the BAP shape during in vitro culture. Numerical analyses showed that insulin release kinetics depended greatly on the thickness of the gel membrane but not on the shape of the agarose hydrogel. The microbead BAP normalized blood glucose levels of all five recipients for more than 100 d. Three of eight recipients of the rod BAP and only one of six recipients of the disc BAP demonstrated long normoglycaemia. These results suggest that the shape of the BAPs determines the in vivo functioning period of the BAPs and that the microbead is the most suitable shape for the BAP.