Curcuminoids-loaded liposomes: influence of lipid composition on their physicochemical properties and efficacy as delivery systems

An extract of Curcuma longa containing mainly curcumin was included in liposomes formulated with phospholipids differing for the length of the acyl chains, the charge of the polar headgroup or the degree of unsaturation in the presence and in the absence of cholesterol. In fact, even if it is well known that liposomal curcuminoids are more stable and can be solubilized in aqueous media, a systematic approach that correlates the molecular structure of liposomes components to the physicochemical and biological behavior of the vescicles including curcumin and its derivatives is not described. Size and zeta potential of liposomes, the location and the antioxidant activity of the solute in the bilayer and its effect on lipid packing were evaluated and correlated to the pharmacological activity of liposomal extract against a methicillin susceptible Staphylococcus Aureus strain ATCC 29213. The relation between the physicochemical and biological features of formulations points out that the rigidity of the bilayer and liposomes charge are crucial parameters in the interactions of liposomes with the biological environment. In particular, the synergism between curcumin antibacterial properties and the positive liposomes surface brings to a significant reduction of the minimal inhibitory concentration of the liposomal drug with respect to the one of the free extract thus enlarging the prospectives of its pharmacological exploitation.