Design and fabrication of large area nano-structured substrates for use in pancreatic beta-cell engineering

Islet transplantation has great potential in restoring normoglycemia in diabetic patients. However, current clinical islet transplantation is associated with high graft failure the reasons of which still remain obscure. It is noteworthy that the process of islet isolation exposes the islet to a variety of cellular stresses, including disruption of the cell-matrix relationship, an event associated with induction of apoptotic pathways. This may adversely affect islet viability and function leading to the observed failure of islet transplantation. The cell-matrix relationship, characterised by adhesion interactions between membrane integrin receptors and the extracellular matrix molecules at the nanoscale, is known to modulate cell survival and growth. The aim of this study is to present a unique method of fabricating large area artificial substrates with biomimetic nanoscale surface topography. The substrates were realised by thermal evaporation of tin on silicon wafers to form randomly assembled nano-islands. Using the nano-islands as masks, the wafers were plasma etched to transfer the pattern onto silicon. We then examined the hypothesis of whether beta-cell function and survival can be enhanced by optimized restoration of cell-matrix adhesion. The results of in vitro cell cultures show that insulinoma cells significantly adhered and enhanced insulin secretion when cultured on these nano-structured substrates compared to planar controls. With this unique fabrication process we propose a simple, robust and accessible technology for fabricating platforms for potential use in the investigation and modulation of early pancreatic beta-cell behaviour which may find utility in the development of strategies for pancreatic islet engineering and transplantation.