Abstract: Aspects of the disclosure generally relate to insulin delivery systems and compositions having a insulin secreting ? cell line or insulin secreting recombinant non-? cells sequestered in a glucose-responsive material. The disclosed insulin delivery systems can be surgically implanted in a host and can provide a continuous source of insulin from the cells contained in the device. The combination of living cells with a glucose-responsive material provides a hybrid insulin delivery system that delivers physiologically relevant amounts of insulin in response to physiologically relevant glucose levels. In some aspects, the disclosed devices have a biphasic release of insulin in response to sudden increases in glucose concentrations in the fluids bathing the device.