INFLUENCE OF HYDROGELS ON LIPOSOME STABILITY AND ON THE TRANSPORT OF LIPOSOME-ENTRAPPED SUBSTANCES INTO THE SKIN

Different liposome-hydrogel formulations, which are used for topical application of liposomes, have been prepared and the role of hydrophilic polymers on the transport of liposome-entrapped hydrophilic substance into pig ear skin was investigated by one-dimensional electron paramagnetic resonance imaging (1D-EPRI) and reduction kinetic imaging methods. Using conventional EPR the influence of polymers on liposome stability was also determined. Multilamellar liposomes composed basically of hydrogenated soya lecithin and cholesterol, with the entrapped hydrophilic paramagnetic probe ASL (N-(1-oxyl-2,2,6,6-tetramethyl-4-piperidinyl)-N-dimethyl-N- hydroxyethylammonium iodide), were prepared in water solution and then mixed into hydrogels with different concentrations of hydrophilic polymers: carboxymethylcellulose or xanthan gum. It was found that the polymers examined do not prevent efficient transport of liposome-entrapped substances into the skin. From the on-going stability study of liposomes in hydrogel formulations, it follows that carboxymethycellulose does not influence the stability of liposomes during the time course of 6 weeks, while in xanthan hydrogels leakage of liposome-entrapped hydrophilic substance was observed already after 10 days. The results support the use of hydrogels in liposome dermatics, but it should be taken into account that some hydrophilic polymers can influence the physical stability of liposomes appreciably.