Sustained release of exendin-4 from tannic acid/Fe (III) nanoparticles prolongs blood glycemic control in a mouse model of type II diabetes.

Exendin-4 has been clinically adopted as an effective drug for treating type 2 diabetes (T2D), but its short circulation half-life in the blood requires two injections per day to maintain effective glycemic control. This significantly limits its clinical application. In this study, we developed a tannic acid/exendin-4/Fe ternary nanoparticle system to provide sustained release of exendin-4 in vivo. The formation of these nanoparticles relies on TA/exendin-4 complexation and stabilization through TA-Fe coordination, where the rapid reaction kinetics can benefit from efficient mixing of all three components. Adapting our recently developed flash nanocomplexation (FNC) method, we formulated nanoparticles with high encapsulation efficiency (~ 100%) of exendin-4, high payload capacity, and high degrees of uniformity and stability because the rapid turbulent mixing facilitated a homogeneous distribution of all three components in the complexation process. Intraperitoneal injection in mice showed that exendin-4 released from the nanoparticles had an AUC 7.2-fold higher than the free exendin-4 injection. Efficacy study in a T2D mouse model showed that the optimized formulation achieved a rapid reduction of the blood glucose level to the normal range within <12 h and maintained the same level for 72 h following a single intraperitoneal dose. The blood glucose level was maintained to below the therapeutic level (< 15 mmol/L) for 6 days, and the treatment led to reduced body weight with pathological and functional improvements in the kidney and liver. This tannic acid/exendin-4/Fe ternary nanoparticle system holds translational potential in treating T2D, due to its improved treatment outcomes in terms of extended release of exendin-4, prolonged control of blood glucose level, reduced dosing frequency, and improved pathological indicators.