Formulation, characterization and permeability study of nano particles of lipo-endomorphin-1 for oral delivery.

Three different formulations of a lipid-modified endomorphin-1 peptide (C₁₀LAA-Endo-1) were prepared, characterized, and evaluated for their permeability through Caco-2 cell membranes. Solid lipid nanoparticles (SLN), enteric coated (EC), and the EC-SLN of C₁₀LAA-Endo-1 is a modified structure of endomorphin-1 for oral delivery. Physico-chemical characterization of the formulations showed that among all formulations, EC-[C₁₀LAA-Endo-1] had the lowest particle size and the highest EE% and absolute zeta potential. Release of drug from SLN, EC-SLN and EC-[C₁₀LAA-Endo-1] in acid media was 14.30 (±2.7)%, 3.0 (±1.0)% and 10.2 (±3.0)%, respectively. Release data in buffer media (pH = 7.4) showed that enteric coated formulations released C₁₀LAA-Endo-1 more slowly than uncoated formulations. It was also demonstrated that direct coating of C₁₀LAA-Endo-1 with Eudragit® S100 significantly enhanced the permeability of the compound through Caco-2 cell membranes with a 39-fold higher P(app) compared to C₁₀LAA-Endo-1. These findings indicated that EC-C₁₀LAA-Endo-1 is a promising candidate to promote the oral delivery of the previously modified endomorphin-1 peptide analogue and is worthy of future animal investigations.