Membranes affinity of 10-hydroxycamptothecin and SN-38, anticancer agents, determined by fluorescence spectra analysis

摘要

Camptothecins are fluorescent compounds which exhibit anticancer properties. A disadvantage which seriously limits application of camptothecins in antitumor chemotherapy is the hydrolysis of these compounds. They convert into inactive carboxylate forms. The process of hydrolysis is inhibited when the molecules of camptothecin are bound to cell membranes. So it is desirable that camptothecins molecules bind easily to membranes. A quantitative measure of drugs affinity to membranes is the association constant. To determine this parameter the small unilamellar lipids vesicles i.e. unilamellar liposomes are used as model membranes. The affinities of 10-hydroxycamptothecin and SN-38 to model membranes are determined in this work. Fluorescence spectra of these analogues change in presence of liposomes: the fluorescence intensity increases and besides green band the blue band appears. The spectra of 10-hydroxycamptothecins and SN-38 change over lipids concentration. On the basis of these changes the association constants to membranes are determined.