Interactions between cationic vesicles and Candida albicans

Dioctadecyldimethylammonium bromide (DODAB), a bilayer-forming synthetic am phiphile with antibacterial properties, also affects viability of Candida a lbicans. For C albicans, simultaneous determination of cell viability and e lectrophoretic mobility as a function of DODAB concentration yields a very good correlation between cell surface charge and cell viability. Upon incre asing DODAB concentration, the cell surface charge decreases and changes it s sign to yield positively charged cells. However, in contrast to the DODAB bactericidal property, the amphiphile effect on fungus over 1 h of interac tion time is only fungistatic at 1 mM DODAB and ca. 10(6) cells/mL. Neverth eless, solubilization of fungicides in DODAB dispersions prepared by sonica tion causes complete loss of cell viability. Amphotericin B (AB) or miconaz ole (M) solubilization in the DODAB bilayer leads to 100% cell death, thoug h the drug and DODAB effects are independent. Cell and DODAB bilayer membra nes compete for AB or M solubilization with the amphiphile bilayer controll ing drug release to the cell membrane. 0.1 mM DODAB plus AB or M concentrat ion of 2 and 20 mug/mL, respectively, yielded 0% of cell viability for C al bicans (2 x 10(6) cells/mL) over an interaction time of 24 h. The cationic liposomes by themselves yielded ca. 20% viability under similar conditions. The full potential of these cytotoxic cationic bilayers to control release and cytotoxicity of drugs remains hitherto unexplored.