Photodynamic therapy with Pc 4 induces apoptosis of Candida albicans.
ABSTRACT The high prevalence of drug resistance necessitates the development of novel antifungal agents against infections caused by opportunistic fungal pathogens, such as Candida albicans. Elucidation of apoptosis in yeast-like fungi may provide a basis for future therapies. In mammalian cells, photodynamic therapy (PDT) has been demonstrated to generate reactive oxygen species, leading to immediate oxidative modifications of biological molecules and resulting in apoptotic cell death. In this report, we assess the in vitro cytotoxicity and mechanism of PDT, using the photosensitizer Pc 4, in planktonic C. albicans. Confocal image analysis confirmed that Pc 4 localizes to cytosolic organelles, including mitochondria. A colony formation assay showed that 1.0 μM Pc 4 followed by light at 2.0 J cm(-2) reduced cell survival by 4 logs. XTT (2,3-bis[2-methoxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxyanilide) assay revealed that Pc 4-PDT impaired fungal metabolic activity, which was confirmed using the FUN-1 (2-chloro-4-[2,3-dihydro-3-methyl-(benzo-1,3-thiazol-2-yl)-methylidene]-1-phenylquinolinium iodide) fluorescence probe. Furthermore, we observed changes in nuclear morphology characteristic of apoptosis, which were substantiated by increased externalization of phosphatidylserine and DNA fragmentation following Pc 4-PDT. These data indicate that Pc 4-PDT can induce apoptosis in C. albicans. Therefore, a better understanding of the process will be helpful, as PDT may become a useful treatment option for candidiasis.
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ABSTRACT: Evaluation of fungal biofilm formation can be performed using several techniques. In this protocol, we describe methods used to form Candida biofilms on three different medical device substrates (denture strips, catheter disks and contact lenses) to quantify them and to evaluate their architecture and drug susceptibility. Biofilm formation involves adhesion of fungal cells to pretreated substrates, followed by growth in medium. Formed biofilms are quantified by determining their metabolic activity and dry weight, whereas their gross morphology and architecture are evaluated using fluorescence microscopy, scanning electron microscopy and confocal scanning laser microscopy techniques. Susceptibility of biofilms is determined by comparing their metabolic activity in the presence of antifungal agents with that in their absence. The methods described here can be completed in a typical laboratory with minimum involvement of software. Evaluation of the growth of fungal biofilms and their analyses can be completed using the described methods in approximately 15 d.Nature Protocol 02/2008; 3(12):1909-24. · 8.36 Impact Factor