Injectable self-assembled peptide hydrogels for glucose-mediated insulin delivery

Closed-loop glucose-responsive insulin delivery with excellent biocompatibility has the potential to improve the health and quality of life of diabetic patients. Herein, we developed an excellent glucose-responsive insulin delivery system using a pH-sensitive peptide hydrogel loaded with insulin and a glucose-specific enzyme. The designed peptide can be used as a carrier that is loaded with insulin and enzyme via a self-assembly process under physiological conditions. When hyperglycemia is encountered, the enzymatic conversion of glucose into gluconic acid leads to a decrease in the local pH, and the hydrogel is disassembled because of the strong inter- and intramolecular electrostatic repulsions between ornithine (Orn) residues; this is followed by the release of insulin. The glucose-responsive hydrogel system was characterized by studying its structure, conformation, rheology, morphology, acid sensitivity and the amounts of consistent release of insulin in vitro and in vivo. In vivo experiments indicated that the closed-loop insulin glucose-responsive system could efficiently regulate blood glucose in streptozocin-induced (STZ-induced) type 1 diabetic rats for 8 days.