The effect of the saturation degree of phospholipid on the formation of a novel self-assembled nano-micellar complex carrier with enhanced intestinal permeability.

The aim of this research was to formulate a novel nano-micellar complex carrier with intrinsically enhanced intestinal permeability for rosuvastatin calcium (RSV); as a model of BCS class III active pharmaceutical ingredients (APIs). The model drug is used primarily for treating hypercholesterolemia. Three phospholipid types with different degrees of saturation were chosen for the study. The saturation degree of the phospholipids was calculated accurately by proton NMR. A D-optimal statistical design was utilized to correlate the saturation degree of the phospholipids with the physico-chemical characteristics of the prepared nano-micellar carrier. The nature of the interaction between the phospholipids and the model drug was studied by proton NMR, photon correlation spectroscopy (PCS) and transmission electron microscopy (TEM). Molecular docking and molecular dynamics simulations were performed to understand the formation mechanism of the complex micelles on a molecular level. The results demonstrated that the interaction of the hydrophilic drug molecule with the polar head of a saturated phospholipid induces an intramolecular self-coiling of phospholipid saturated acyl chain leading to a structural transformation from a two-tailed cylindrical configuration into a one-tailed, surfactant-like configuration owing to the flexibility of the saturated chains. This transformation leads to the construction of a novel nano-micellar structure in which the drug has lower water solubility but higher lipophilicity than in traditional micelles. Permeability studies conducted on Caco-2 cells demonstrated that the novel nano-micellar carrier had superior permeability to that of the un-complexed hydrophilic drug. The optimized nano-micellar formulation showed significantly (P < 0.5) superior bioavailability in rats to that of the aqueous drug solution in terms of both the rate and extent of drug absorption. Overall, the results confirmed that the formation of the phospholipid nano-micellar complex increased the permeability of the hydrophilic BCS class III drug and converted it to a class BCS I drug by a simple and effective formulation technique.