A Nanocomposite Vehicle Based on Metal–Organic Framework Nanoparticle Incorporated Biodegradable Microspheres for Enhanced Oral Insulin Delivery

Oral insulin delivery has revolutionized diabetes treatment, but challenges including degradation in the gastrointestinal environment and low permeation across the intestinal epithelium remain. Herein, to overcome these barriers, we developed a novel biodegradable nanocomposite microsphere embedded with metal–organic framework (MOF) nanoparticles. An iron-based MOF nanoparticle (NP) (MIL-100) was first synthesized as a carrier with an insulin loading capacity of 35%. The insulin-loaded MIL-100 nanoparticles modified with sodium dodecyl sulfate (Ins@MIL100/SDS) promoted insulin permeation across Caco-2 monolayer models in vitro. To improve resistance to the gastric acid environment, Ins@MIL100/SDS nanoparticles were embedded into a biodegradable microsphere to construct the nanocomposite delivery system (Ins@MIL100/SDS@MS). The microspheres effectively protected the MOF NPs from rapid degradation under acidic conditions and could release insulin-loaded MOF NPs in the simulated intestinal fluid. After the oral administration of Ins@MIL100/SDS@MS into BALB/c nude mice, increased intestinal absorption of the insulin was detected compared to the oral administration of free insulin or Ins@MIL100/SDS. Furthermore, significantly enhanced plasma insulin levels were obtained for over 6 h after oral administration of Ins@MIL100/SDS@MS into diabetic rats, leading to a remarkably enhanced effect in lowering blood glucose level with a relative pharmacological availability of 7.8%. Thus, the MOF-nanoparticle-incorporated microsphere may provide a new strategy for effective oral protein delivery.