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 2mg/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.
Keywords: Dimyristoyl phosphatidylglycerol; Insulin; Ionic complexation; Mucus; Oral delivery; SNEDDS.
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