In Vitro Photodynamic Inactivation of Cryptococcus neoformans Melanized Cells with Chloroaluminum Phthalocyanine Nanoemulsion

Abstract

The selection of fungi resistant to currently used fungicides and the emergence of new pathogenic species make the development of alternative fungus-control techniques highly desirable. Photodynamic antimicrobial chemotherapy (PACT) is a promising method which combines a nontoxic photosensitizer (PS) with visible light to cause selective killing of microbial cells. The development of PACT to treat mycoses or kill fungi in the environment depends on identifying effective PS for the different pathogenic species and delivery systems able to expand and optimize their use. In the present study, the in vitro susceptibility of Cryptococcus neoformans melanized cells to the photodynamic effects of the PS agent ClAlPc in nanoemulsion (ClAlPc/NE) was examined. Cells were killed in a PS concentration- and light dose-dependent manner. Treatment with ClAlPc/NE, using PS concentrations (e.g. 4.5 μm) and light doses (e.g. 10 J cm(-2)) compatible with PACT, resulted in a reduction of up to 6 logs in survival. Washing the cells to remove unbound PS before light exposure did not inhibit fungal photodynamic inactivation. Internalization of ClAlPc by C. neoformans was confirmed by confocal fluorescence microscopy, and the degree of uptake was dependent on PS concentration.

In vitro susceptibilities of Neoscytalidium spp. sequence types to antifungal agents and antimicrobial photodynamic treatment with phenothiazinium photosensitizers

“…Arthroconidia of N. dimidiatum isolates were more tolerant to APDT with all the four phenothiazinium PS than the hyaline isolates (see Table 5). The protective effect of melanins and melanin-like pigments against conventional antifungal drugs [61][62][63] and also to APDT [64][65][66][67] was observed previously both in conidia and in vegetative yeast cells. Pigmented conidia of Penicillium and Metarhizium are much more resistant to APDT with different PS than the colorless mutants [65][66].…”

“…Pigmented conidia of Penicillium and Metarhizium are much more resistant to APDT with different PS than the colorless mutants [65][66]. In yeasts, Cryptococcus neoformans melanized cells are more resistant to APDT than the nonmelanized cells [64,67]. Unfortunately the mechanisms responsible for increasing resistance due the presence of pigments appear to be diverse and are not yet fully understood.…”

In Vitro Photodynamic Inactivation of Plant-Pathogenic Fungi Colletotrichum acutatum and Colletotrichum gloeosporioides with Novel Phenothiazinium Photosensitizers

“…Previous studies have reported the use of APDT with different PSs to kill fungi of several genera, including Aspergillus, Candida, Cryptococcus, Metarhizium, and Trichophyton (15)(16)(17)20). Data regarding the photodynamic inactivation of plant-pathogenic fungi are scarce, and most of those studies were performed by using natural compounds as PSs.…”

“…Antimicrobial photodynamic treatment (APDT) is an alternative and promising antifungal discovery platform that can be used to control localized mycoses in animal hosts or to kill fungi in the environment (12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22). The approach is based on the use of a photosensitizer (PS) that binds to the surface or preferentially accumulates in the target fungal cell (13,14,17,20). Subsequent exposure of the PS to light of an appropriate wavelength starts a photochemical process that produces several reactive oxygen species (ROS), such as peroxides and singlet oxygen, leading to nonspecific oxidative damage and causing the subsequent death of the fungal cells without significant harm to the host (14,19,20).…”

Isolamento, caracterização e avaliação da atividade fotossensibilizadora de cumarinas e furanocumarinas extraídas de espécies de Citrus

“…Sin embargo, las soluciones de 8-MOP expuestas durante 6 y 12 h também fueron capaces de matar um 99,978% y 95,591% de conídios de C. acutatum, respectivamente. (De MENEZES et al, 2014a,b;RODRIGUES et al, 2012;GOMES et al, 2011;GONZALES et al, 2010).…”