Liposil, a promising composite material for drug storage and release

Preliminary tests in the field of drug storage and release of composite materials known as liposils were described. These silica-based particles were obtained via liposome templating. The non-porous amorphous silica cladding of liposils protected the liposomes which retained the fundamental properties of their phospholipid bilayer. In an improved synthesis, two formulations were used, one with and the other without cholesterol in the phospholipid bilayer. Stability tests were done using carboxylluorescein as a model hydrophilic drug loaded in the liposornes aqueous phase before the templating process. The stability of the loaded liposils was analyzed at two different pH (1.2 and 7.4) in a flow cell, according to the USP 28 norm. At pH 1.2, the silica shell was stable and prevented their rapid degradation. Interestingly, at PH 7.4 the analysis of the release kinetics revealed that the hydrolysis of the silica shell initially released intact liposomes. Characterizations of liposils were done at various steps of these processes. The stability observed for liposils make them good starting material for drug storage and release schemes. For instance, functionalization of their external surface should improve their capture by cells whereby drug release could then be induced by external stimuli, such as ultrasounds or microwaves. (c) 2006 Elsevier B.V. All rights reserved.