Photophysical, photochemical and antibacterial photosensitizing properties of a novel octacationic Zn(II)-phthalocyanine

A. SEGALLA; C. D. BORSARELLI; S. E. BRASLAVSKY; J. D. SPIKES; G. RONCUCCI; D. DEI; G. CHITI; G. JORI; E. REDDI

Photochemical and Photobiological Sciences

Royal Society of Chemistry

Año: 2002 vol. 1 p. 641 - 648

1474-905X

A novel Zn(II)-phthalocyanine (1), peripherally substituted with four di(N,N,N-trimethyl)amino-2-oxypropyl groups prepared by chemical synthesis, is shown to be an efficient photodynamic sensitizer with a quantum yield of 0.6 for singlet oxygen generation in neat water, which is reduced to about 0.3 in phosphate-buffered saline. The physico-chemical properties of 1 in both the ground and the electronically excited states strongly depend on the nature of the medium; in particular, aggregation of 1 was favoured by polar media of high ionic strength. Compound 1 exhibited an appreciable affinity for a typical Gram‑positive bacterium (Staphylococcus aureus) and a typical Gram‑negative bacterium (Escherichia coli). Both bacterial strains were extensively inactivated upon 5 min-irradiation with 675 nm light in the presence of 1 mM photosensitizer, even though the binding of 1 to the two bacterial cells appears to occur according to different pathways. In particular, E. coli cells underwent an initial photodamage at the level of specific proteins in the outer wall, thus promoting the penetration of the photosensitizer to the cytoplasmic membrane where some enzymes critical for cell survival were inactivated.