Hollow-adjustable polymer microneedles for prolonged hypoglycemic effect on diabetic rats

Maintaining blood glucose levels within a safe range is critical for diabetic management. In recent decades, microneedles (MNs) have emerged as a potential method for delivering drugs to treat diabetes. However, insufficient drug loading and the complexity of achieving long-acting release have presented challenges that research has not addressed well. In this study, the hollow-adjustable biocompatible polymer MNs with varying cavity volumes were developed by cyclic freeze-thawing technique. The structure of shell-layer of hollow MNs was optimized with a sequential casting approach for regulating drug release kinetics. This design can ensure the sufficient mechanical strength of MNs and help to improve the drug-loading capacity, thereby solving the problem of low drug-loading capacity and short pharmacodynamic action time of traditional polymer MNs. In vivo experiments performed on diabetic rat models revealed the potential of the as-fabricated MNs to effectively pierce into the skin, leading to a notable hypoglycemic effect lasting up to 14 h without inducing the risk of hypoglycemia. These results indicate that the fabricated hollow-adjustable polymer MNs is a potential candidate for transdermal delivery of high-dose drugs.