Adhesion of pancreatic beta cells to biopolymer films

Dramatic reversal of Type 1 diabetes in patients receiving pancreatic islet transplants continues to prompt vigorous research concerning the basic mechanisms underlying patient turnaround. At the most fundamental level, transplanted islets must maintain viability and function in vitro and in vivo and should be protected from host immune rejection. Our previous reports showed enhancement of islet viability and insulin secretion per tissue mass for small islets (<125 μm) as compared with large islets (>125 μm), thus, demonstrating the effect of enhancing the mass transport of islets (i.e. increasing tissue surface area to volume ratio). Here, we report the facile dispersion of rat islets into individual cells that are layered onto the surface of a biopolymer film towards the ultimate goal of improving mass transport in islet tissue. The tightly packed structure of intact islets was disrupted by incubating in calcium-free media resulting in fragmented islets, which were further dispersed into individual or small groups of cells by using a low concentration of papain. The dispersed cells were screened for adhesion to a range of biopolymers and the nature of cell adhesion was characterized for selected groups by quantifying adherent cells, measuring the surface area coverage of the cells, and immunolabeling cells for adhesion proteins interacting with selected biopolymers. Finally, beta cells in suspension were centrifuged to form controlled numbers of cell layers on films for future work determining the mass transport limitations in the adhered tissue constructs.