Microneedles Integrated with ZnO Quantum-Dot-Capped Mesoporous Bioactive Glasses for Glucose-Mediated Insulin Delivery

A self-responsive insulin delivery system is highly desirable because of its high sensitivity dependent on blood glucose levels. Herein, a smart pH-triggered and glucose-mediated transdermal delivery system, insulin-loaded and ZnO quantum dots (ZnO QDs) capped mesoporous bioactive glasses (MBGs) integrated with microneedles (MNs), was developed to achieve control and painless administration. ZnO QDs as a promise pH-responsive switch were employed to cap the nanopores of MBGs via electrostatic interaction. The drug (insulin) and glucose-responsive factor (glucose oxidase/catalase, GOx/CAT) were sealed into the pores of MBGs. GOx/CAT in the MBGs could catalyze glucose to form gluconic acid, resulting decrease in the local pH. The ZnO QDs on the surface of the MBGs could be dissolved in the acidic condition, leading to disassembly of the pH-sensitive MBGs and then release of preloaded insulin from the MBGs. As a result of administration in a diabetic model, an excellent hypoglycemic effect and lower hypoglycemia risk were obtained. These results indicate that as-prepared pH-triggered and glucose-mediated transdermal delivery systems have hopeful applications in the treatment of diabetes.