Author/Editor		Gabrijelčič, V; Šentjurc, M; Schara, M
Title		The measurement of liposome entrapped molecules' penetration into the skin: a 1D-EPR and EPR kinetic imaging study
Type		članek
Source		International journal of pharmaceutics
Vol. and No.		Letnik 102
Publication year		1994
Volume		str. 151-8
Language		eng
Abstract		One-dimensional electron paramagnetic resonance imaging (ID-EPRI) and EPR reduction kinetics were used to follow continuously the transport of liposome entrapped substances into the skin. Through 1D-EPRI the concentration distribution of the paramagnetic probe, which was applied to the skin entrapped in liposomes, could be followed, while through EPR reduction kinetics the chemical transformation of the paramagnetic probe, after it had been released from the liposomes, to an EPR-invisible form could be measured. Through the combination of both methods, and with the application of a model, in which the heterogeneity of different skin layers and the metabolism of the released substance was taken into account, liposome decay in the skin, as well as the time evolution of concentration distribution profiles for ASL in skin, was followed separately for both the entrapped substance and that released from liposomes. MLV (multilamellar vesicles) and REV (reverse-phase evaporation vesicles) obtained from egg lecithin and cholesterol (7:3 mol/mol) with the entrapped spin probe ASL (N-(1-oxyl-2,2,6,6-tetraethyl-4-piperidinyl)-N-dimethyl-N-hydroxyethylammonium iodide), which does not penetrate the liposome membrane easily, were applied to pig ear skin and the results were compared with those obtained for ASL dissolved in water and applied to the skin. The rapid decay of liposomes in the stratum corneum was measured, being much faster for MLV than for REV. In addition, a rate of transport 100-times faster was observed for ASL applied to the skin in REV than that observed for ASL applied in MLV or in solution. Our observations show that the rapid decay of liposomes takes place in the stratum corneum, however, some of the ASL molecules remain protected from the reducing agents in the skin, which indicates that some REV liposomes can penetrate deeper into the skin, or at least their lipids protect the entrapped substance from metabolic transformation.
Descriptors		LIPOSOMES ELECTRON SPIN RESONANCE SPECTROSCOPY ADMINISTRATION, CUTANEOUS DRUG CARRIERS EGG YOLK