Mechanochemical approaches to self-regulating insulin pump design

Wearable and implantable insulin delivery devices have been proposed by many groups to replace periodic subcutaneous insulin injection. The rationale behind this work lies in the lack of correspondence between insulin and glucose disposition resulting from subcutaneous administration compared with that occurring after pancreatic insulin release. We briefly review features of insulin and glucose disposition processes that impact the design of artificial insulin delivery systems, enabling advantages and disadvantages of currently pursued strategies (electromechanical, biochemical, chemical, mechanochemical) to be identified. We also propose two implantable self-regulating insulin pumps whose action depends on the expansion and contraction of certain pH-sensitive hydrogel membranes that respond to changes in glucose concentration via enzymatic conversion of glucose to gluconic acid. It is shown that the dynamics of pH-sensitive volume changes favor one pump design, based on direct conversion of changes in glucose concentration to mechanical force, over the other, which is an osmotic pump whose semipermeable membrane's permeability to water is sensitive to glucose concentration.