Fluorescence of Amphotericin B-deoxycholate (Fungizone) monomers and aggregates and the effect of heat-treatment

Fluorescence excitation and emission spectra are reported for the polyene macrolide antifungal agent Amphotericin B formulated as micellar dispersion Fungizone (FZ) and its modified counterpart heat-treated Fungizone. The addition of sodium dodecyl sulfate or sodium deoxycholate surfactant to modulate the aggregation state of Amphotericin B confirms that the monomer and dimer states have different fluorescence spectra. Energy transfer from excited dimer to monomer is observed. Both FZ and heat-treated FZ (HTFZ) show expected S-1 -> S-0 fluorescence emission as well as anti-Kasha fluorescence emission fromthe S-2 state. The excitation and S-1 -> S-0 emission spectra of HTFZ are similar to those of FZ, while the S-2 -> S-0 fluorescence differs in intensity between them. The variation in the rate constant for internal conversion from S-2 to S-1 as the surfactant concentration is increased differs for FZ and HTFZ; we propose that this may form a new basis for examining the super-aggregated character of AmB preparations. FZ and HTFZ have a similar stability to disaggregation by added sodium dodecyl sulfate surfactant. These findings provide the groundwork for future fluorescence characterization of FZ or HTFZ interactions with cell membranes.