Theoretical analysis of the effect of convective flow on solute transport and insulin release in a hollow fiber bioartificial pancreas.

The bioartificial pancreas, in which transplanted pancreatic tissue or isolated cells are cultured on a hollow fiber membrane, is an attractive approach to restore physiologic insulin delivery in the treatment of diabetes. Insulin response in prototype devices has been unacceptable due to the large mass transport limitations associated with the membrane and the surrounding shell region. Although available theoretical analyses provide some insight into the combined effects of transport and reaction in the bioartificial pancreas, they cannot quantitatively account for the effects of convective recirculation flow, complex intrinsic insulin secretory kinetics, and non-uniform distribution of pancreatic cells. We have developed a detailed model for glucose and insulin transport and insulin secretion in the hollow fiber bioartificial pancreas based on the solution of the mass and momentum conservation equations describing flow and transport in the lumen, matrix, and shell. Model predictions are in good agreement with literature data obtained in a hollow fiber device with minimal radial convective flow. Although no quantitative data are available for a device with significant radial convection, model simulations demonstrate that convective recirculation flow can dramatically improve insulin response, allowing the device to accurately capture the bi-phasic insulin secretion characteristic of the normal physiologic response. Results provide fundamental insights into the coupling between kinetics and transport in the hollow fiber system and a rational basis for the design of clinical devices.