title: Optimization of cellular uptake of zinc(II) 2,9,16,23-tetrakis[4-(N-methylpyridyloxy)]phthalocyanine for maximal photoinactivation of Candida albicans.
abstract: Cellular uptake and photodynamic action of zinc(II) 2,9,16,23-tetrakis[4-(N-methylpyridyloxy)]phthalocyanine (ZnPPc⁴⁺) was examined in Candida albicans. In vitro investigations showed that ZnPPc⁴⁺ was rapidly bound to C. albicans cells. The binding of phthalocyanine to cells was dependent on ZnPPc⁴⁺ concentrations (1-10 μM) and cells densities (10⁶-10⁸ cells mL⁻¹). A high amount of ZnPPc⁴⁺ retained in the cells after two washing steps, indicating a strong interaction between the photosensitizer and C. albicans. The uptake was temperature dependent, although the difference between 37 °C and 4 °C was about 10 %. Also, the amount of ZnPPc bound to C. albicans was affected when the cells were incubated for a longer time with azide and 2,4-dinitrophenol (DNP) prior to treatment with ZnPP⁴⁺. Cell survival after irradiation was dependent on the irradiation period, ZnPPc⁴⁺ concentration and cells density. Photoinactivation of C. albicans cells was elevated even after two washing steps. The strong dependence of uptake on cell density reveals the strength and avidity of the binding of ZnPPc⁴⁺ to C. albicans cells. The accumulation behaviour of ZnPPc⁴⁺ suggests that mainly an affinity-mediated binding mechanism can be involved. Therefore, ZnPPc⁴⁺ is an interesting phthalocyanine for photodynamic inactivation (PDI) of yeasts in liquid suspensions.
authors.affiliation: Departamento de Química, Facultad de Ciencias Exactas Físico-Químicas y Naturales, Universidad Nacional de Río Cuarto, Agencia Postal Nro 3, X5804BYA Río Cuarto, Córdoba, Argentina.
authors.forename: María A
authors.initials: MA
authors.lastname: Di Palma
authors.forename: María G
authors.initials: MG
authors.lastname: Alvarez
authors.forename: Ana L
authors.initials: AL
authors.lastname: Ochoa
authors.forename: María E
authors.initials: ME
authors.lastname: Milanesio
authors.forename: Edgardo N
authors.initials: EN
authors.lastname: Durantini
mesh_terms: D000935:Antifungal Agents / Q000378:metabolism / Q000494:pharmacology*; D002176:Candida albicans / Q000187:drug effects* / Q000502:physiology; D003624:Darkness; D008027:Light; D050296:Microbial Viability / Q000187:drug effects*; D017319:Photosensitizing Agents / Q000378:metabolism / Q000494:pharmacology*; D011166:Porphyrins / Q000378:metabolism / Q000494:pharmacology*; D013696:Temperature
chemical_list: D000935:Antifungal Agents; D017319:Photosensitizing Agents; D011166:Porphyrins; C416848:RLP 024
keywords: Antifungal; Cationic phthalocyanine; Photodynamic inactivation; Photosensitizer; Yeast