Water soluble octa-imidazolium zinc phthalocyanine for nucleus/nucleolus cell fluorescence microscopy and photodynamic therapy.

A poly-cationic theranostic macrocycle was developed to perform confocal microscopy imaging and photodynamic therapy studies on a model of melanoma cancer, one of the most aggressive cancer. Hence, an octa-imidazolium zinc phthalocyanine was conveniently synthesized in large amount in three steps in a 44% overall yield: upon double nucleophilic aromatic substitution, cyclo-tetramerization and quaternization reactions. Such an octa-cationic molecule was readily soluble in physiological media, reaching concentrations beyond 1 mM. It showed fluorescence properties in aqueous medium (ΦF = 0.31) with no noticeable aggregation, spectroscopy studies showed. In vitro confocal fluorescence microscopy studies carried out on murine melanoma model (B16F10 cells) showed that the fluorophore was mainly located in the cell nucleolus, an organelle of interest for the treatment of cancer. The anticancer photodynamic potential of the octa-cationic photosensitizer could be measured (IC50 = 5.4 µM) using the MTS viability assay. Both fluorescence microscopy studies and photodynamic studies demonstrate the octa-cationic molecule is theranostic and could be further developed for future photodynamic diagnosis (PDD) and photodynamic inactivation of micro-organisms (PDI).