Interaction of rifampicin and isoniazid with large unilamellar liposomes: spectroscopic location studies

The location of isoniazid and rifampicin, two tuberculostatics commonly used for the treatment of Mycobacterium tuberculosis and Mycobacterium avium complex infectious diseases, in bilayers of dimyristoyl-L-alpha-phosphatidylcholine (DMPC) and dimyristoyl-L-a-phosphatidylglycerol (DMPG) have been studied by H-1 NMR and fluorimetric methods. Steady-state fluorescence intensity and fluorescence energy transfer studies between rifampicin and a set of functionalized probes {n-(9-anthroyloxy)stearic acids, n = 2, 12} reveal that, in both systems, isoniazid is located at the membrane surface whereas rifampicin is deeply buried inside the lipid bilayers. Steady-state fluorescence anisotropy studies performed with the probes 1,6-diphenyl-1,3,5-hexatriene (DPH) and trimethylammonium-diphenylhexa-triene (TMA-DPH), not only corroborate the above results, but also show that no changes in membrane fluidity were detected in either liposome. The H-1 NMR results, in DMPC liposomes, confirm the location of rifampicin near the methylene group of the acyl chains of the lipid bilayers. (C) 2002 Elsevier Science B.V. All rights reserved.