Phenylboronic acid-based nanogels for onset-controllable glucose-regulated insulin delivery

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Development of a closed-loop insulin delivery system capable of self-regulating the insulin doses for diabetic care with minimum patient efforts remains a formidable challenge. The inherent instabilities of protein-based systems have hindered a successful clinical translation. This proposal aims to develop a new class of phenylboronic acid (PBA)-bearing nanogel insulin formulation that can mimic the natural function of pancreatic -cells to sense the glucose levels in real time and deliver the right amount of insulin spontaneously. Specifically, the glucose-imprinted nonlinear poly(ethylene glycol) (PEG) matrixed nanogels will be prepared from the precipitation polymerization of oligo(ethylene glycol) (OEG) macromonomer, PEG crosslinker, and glucose-complexed PBA monomer in water. We expect that the nanogels composed of crosslinked neutral hydrophilic PEG matrix and glucose-imprinted PBA domains with specific recognition to glucose molecules will repel plasma proteins and offer long circulation in vivo. We design to use (1) the OEG/PBA molar ratio in the nanogels to control the onset and sensitivity of the glucose-responsive gel swelling to trigger insulin retention and release; (2) the PEG crosslinker density to control the pore size, structure, and swelling degree of the nanogels to optimize the insulin loading and release behavior; and (3) the dispersing agent/monomer ratio to control the size of nanogels to increase the circulation time. We propose to immobilize the highly fluorescent carbon dots (CDs) into the nanogels as an optical label for simultaneous glucose monitoring. We plan to fine tune four synthetic parameters including the OEG/PBA molar ratio, PEG crosslinker density, dispersing agent/monomer ratio, and CDs content to optimize the size, structure, and glucose-responsive swelling and optical properties of the nanogels and test in vitro the insulin loading capacities, kinetics of glucose responsive insulin release, insulin retention/release controllability, the bioactivity of released insulin, and cytotoxicity of the resultant nanogels. The optimized nanogels with desirable size, high loading capacity, accurate insulin retention and release, and good optical property will be then tested in vivo on diabetic mouse models, including biodistributions, toxicology, glycemic control, and glucose tolerance ability. Successful completion of this project will pave the way to free the patients from the frequent painful glucose monitoring and substantially reduce the frequency of insulin injections, thus improve the life quality of diabetic patients. This project will be carried out by a team of three scientists with complementary expertise, including an endocrinologist to advise clinical requirement in diabetes care. This project will also provide an excellent platform to train undergraduate researchers successively in both PI's and co-I's laboratories. They will fine tune the synthetic parameters to optimize the compositions of nanogels and then use the nanogels to test the in vitro insulin delivery properties and in vivo glycemic control efficacy on diabetic mice.