Effective incorporation of insulin in mucus permeating self-nanoemulsifying drug delivery systems

Abstract The development of a novel, mucus permeating SNEDDS formulation for oral insulin delivery containing a hydrophobic ion pair of insulin/dimyristoyl phosphatidylglycerol (INS/DMPG) is presented. Three oil/surfactant/cosurfactant combinations and 27 weight ratios of oil, surfactant and cosurfactant for each combination were evaluated with the aid of ternary phase diagrams, for the incorporation of the protein/phospholipid complex. The developed formulation was characterized by an average droplet diameter of 30–45 nm. Depending on the initial protein concentration, the loading of insulin in SNEDDS varied between 0.27 and 1.13 wt%. The therapeutic protein was found to be efficiently protected from enzymatic degradation by intestinal enzymes (i.e., trypsin, α-chymotrypsin). The SNEDDS formulation exhibited increased mucus permeability and did not appear to be affected by ionic strength. The incorporation of INS/DMPG in SNEDDS prevented an initial burst release of insulin. INS/DMPG loaded SNEDDS were found to be non-cytotoxic up to a concentration of 2 mg/ml. According to the reported results, the incorporation of the hydrophobic ion pair of INS/DMPG in SNEDDS could be regarded as a promising strategy for the oral delivery of insulin.