In vitro photosensitizing efficacy of cationic phthalocyanine derivatives against C.albicans:: effect of serum albumins

The effect of serum albumins (as Fetal Calf Serum) on in vitro photosensing efficacy against C.albicans of three cationic Zn(II) phthalocyanine derivatives was evaluated. A clearly structure-dependent reduction in the antifungine activity was observed. For this reason the binding of the photosensitizers with albumins (as bovine serum albumin, BSA) at pH 7.4 was studied. Because of aggregation phenomena, the phthalocyanine derivatives showed little fluorescence in aqueous solutions and fluorescence intensity increased as a function of protein concentration. Titration plots were built and binding constant were determined. The obtained binding parameters and the hydro-lipophilic properties of the studied molecules (octanol/water partition coefficient P-O/W, number of cationic charges, amphipilicity) were correlated with the observed biological effect. Copyright (c) 2005 Society of Porphyrins & Phthalocyanines.