Development of Eudragit/gelatin-based microparticles for oral insulin delivery for diabetes treatment

Purpose: To prepare Eudragit® S100/gelatin-based insulin-loaded microparticles for improved oral delivery of insulin in diabetes management. Methods: Eudragit® S100 and gelatin were employed in the formulation of insulin microparticles (EGel-MPs) for oral delivery at different ratios (0:1, 1:0, 1:1, 1:3, and 3:1 for Y1, Y2, Y3, Y4, and Y5, respectively) using double emulsion technique. A 1:1 ratio of Eudragit® S100 and gelatin microparticles not loaded with insulin (Y0) was used as a negative control, while aqueous insulin dispersion was used as a positive control. EGel-MPs were characterized for encapsulation efficacy (EE), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). In vitro drug release and in vivo antidiabetic activity in rats were also determined. Results: Encapsulation efficacy ranged from 78.84 ± 0.24 to 89.43 ± 1.13 %, with Y4 as the highest, while SEM indicated spherical shapes and rough surfaces with pores. Particle sizes ranged from 6.22 ± 3.07 to 18.27 ± 0.02 μm. Batch Y3 depicted the broadest peak and lowest enthalpy, indicating an amorphous state and enhanced drug entrapment. In vitro insulin release exhibited a characteristic slow-release pattern, which may be attributed to mucoadhesiveness, leading to slow hydration, swelling, and gelling of particles within the buffer system. The in vivo antidiabetic activity was significantly better (p < 0.05) than that of both the negative and positive controls. Conclusion: Bioavailability of orally delivered insulin has been improved using co-polymers of Eudragit® S100/gelatin microparticles (EGel-MPs). However, further studies are needed to quantify the bioavailability, rate of absorption and duration of glycaemic control.