Myrrh Oil-Based Nanoemulsion Loaded with Curcumin and Insulin: Development, Characterization, and Evaluation of Enhanced Antibacterial and Diabetic Wound-Healing Activity

Abstract

Background/Objectives: Curcumin (CUR) has shown promising potential as a wound-healing agent for diabetic wounds; however, its efficacy is hindered by poor aqueous solubility and limited skin permeability. To overcome these limitations, CUR was loaded into myrrh oil-based nanoemulsions (NEs). Methods: The NEs were optimized using a three-factor two-level D-optimal mixture design, and characterized for droplet size, polydispersity index, and zeta potential. The optimized NE was subjected to various stability testing and incorporated into a gel base containing insulin (INS) to form CUR-INS nanoemulgel (CUR-INS-NEG). The antibacterial efficacy of CUR-INS-NEG was tested against various bacterial strains, while its wound-healing effects were evaluated in a diabetic rat wound model. Results: The surfactant/co-surfactant concentration had a greater influence on the NE properties than the oil and aqueous phase concentrations. The optimal NE had a droplet size of 155.2 ± 0.8 nm, a polydispersity index of 0.28, and a zeta potential of −31.4 ± 0.8 mV. It demonstrated sustained drug release, with further release control upon incorporation into the gel base. CUR-INS-NEG demonstrated higher in vitro antibacterial efficacy compared with blank NEG, CUR gel, and INS gel. It also showed 2- and 4-fold reduction in the MIC against S. aureus and E. coli, respectively, compared with CUR gel. In a diabetic wound model, CUR-INS-NEG outperformed both CUR gel and INS gel by enhancing anti-inflammatory and antioxidant effects, as well as collagen deposition and endothelial cell proliferation. Conclusions: The CUR-INS-NEG emerges as an effective system for diabetic wound management, delivering complementary anti-inflammatory, antioxidant, and tissue-regenerative effects of myrrh oil, CUR, and INS.