Surfactant effects on the physical characteristics of Amphotericin B-containing nanostructured lipid carriers

In the present study, we investigate the effects of various surfactants/lipid combinations and processing variables on the physical properties of Amphotericin B-loaded nanostructured lipid carriers (NLCs). The lipids comprised of theobroma oil and beeswax as solid lipids, whilst oleic acid was used as liquid lipid. Tween 80 (non-ionic), Pluronic F-127 (non-ionic), sodium cholate (ionic), sodium lauryl sulphate (ionic) and lecithin (neutral) were the surfactants involved. Low to moderate concentrations of the ionic surfactants produced NLCs with higher zeta potential, lower polydispersity and lower size. Electrostatic repulsions (derived from ionic surfactants), rather than stearic hindrance are necessary for imparting stability to the NLC during storage. NLC formulated by probe-ultrasonication expelled significant amounts of Amphotericin B expulsion during storage; being most apparent in lecithin-containing NLC matrices of beeswax as opposed to beeswax matrices without lecithin or lecithin-containing theobroma oil NLC. Aptly, modification of the NLC crystal lattice was observed with the inclusion of oleic acid but this did not result in a high Amphotericin B loading. There appears to be a cut-off concentration of liquid lipid needed to improve the drug loading, beyond which, leaching of the drug occurs.