Preparação e caracterização de magnetolipossomas para aplicações em processos de absorção por afinidade

AUTOR(ES)
DATA DE PUBLICAÇÃO

1998

RESUMO

Magnetoliposomes are vesicles which are made by adsorption of phospholipids in the surface of particles of the colIoidal magnetic fluid, like magnetite. These particles have structures formed by phospholipids in bilayer which encapsule magnetite inside of them. These liposomes preserve almost alI properties of lipidic bilayer, besides to be captured from solution or take to specific sites, by action of high gradient magnetic field. Nowadays, the research in the field of magnetic particles increases because their applications are important in various areas of science. However, the literature about magnetoliposomes is still not long. The studies are mainly about the preparation and characterization of the vesicles made by one lipidic component only, without chemical modifications in the surface. The main applications of the magnetoliposomes are in the medical area, as vehicles to the encapsulating of therapeutic drugs and their control release. In this work, magnetoliposomes were prepared and characterized for applications in process of adsorption by affinity. These applications lead to the use of liposomes in extrabody therapy, as biosensor, in diagnostic, and to the encapsulating and controlled release of drugs. The potenciality of the system was analyzed in the adsorption of the trypsin by the use of paminobenzamidine, PAB, like affinity ligand. The magnetoliposomes were prepared using dimyristoil phosphatidyl ethanolamine, DMPE, and dimyristoil phosphatidyl choline, DMPC phospholipids, on the surface of colIoidal magnetite, which are made from iron chlorides and stabilized by lauric acid. These vesicles were captured ITomthe medium through a high gradient magnetophoresis system. The affinity magnetoliposomes were prepared by covalently attaching PAB, a trypsin inhibitor, to the surface of vesicles. Vesicles were characterized by diameter measurements phospholipids, magnetite, and PAB concentrations, and by their stability in the presence of surfactant. The obtained results showed that the relation of saturation of the adsorbed phopholipids on the magnetite was 1,29 ± 0,04 mmol of phospholipids/g of magnetite, obtained in about 40 hours of dialysis. The concentration of the phospholipids in the monolayer was 0,4 mmol of phospholipids/g of magnetite. The association constant, obtained by adjustment of the results to the Langmuir Equation was 11,3 ?mM POT. ?1?I. The results of the kinetic of adsorption obeyed to the modelof pseudo firstorder, witha reactionrate of 0,066 ± ?0,002 POT. h-1?, and a time of 10,5 ± 0,3 hours to reaches 50% of the saturation. The retention of the particles by the system of magnetophoresis was 100% and the magnetoliposomes showed good stability and ability to reutilization. A adsorption of 13% of the trypsin, which was quantified by its activity, was obtained to a concentration of 8,9 nmol /ml of the PAB in the surface ofvesicles. These characteristics show that there is a large potenciality to applications of the magnetoliposomes in several processes which use adsorption by affinity

ASSUNTO(S)

campos magneticos absorção lipossomos

ACESSO AO ARTIGO

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