34 Among other factors, successful check details PDT depends on the pre-irradiation time (PIT),35 which is the time required by the PS to remain in contact with the
target cells before irradiation. This period will enable the PS to bind to the cytoplasmic membrane and/or penetrate into the cells.33 and 34 The following exposure to light will allow the PSs to exert their function in promoting cell death. Many researchers have focused their attention on effective PSs for the photoinactivation of microorganisms.26, 27, 29, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44 and 45 Curcumin (Cur) is a yellow-orange dye extracted from the rhizomes of the plant Curcuma longa. 46 It is commonly used as a spice in traditional Asian cookery, and has been shown to exhibit a variety of pharmacological properties such as antitumor, anticancer, anti-inflammatory, antioxidants, and antimicrobial activities, 18, 46 and 47 some of which can be enhanced by light application. 44 and 48 Cur has been used as a PS in antimicrobial PDT, mainly on photoinactivation of Candida species, with positive results. 41 However, some studies have stated that in contrast to that which occurs with several PSs, Cur does not bind to cells, or binds to them weakly, leaving about 90% in an extracellular bulk phase. 37 The removal
of the non-associated Cur promotes a substantial reduction in its phototoxic effects. 36 and 41 The aim of this study was to evaluate Selleck AG-14699 the effects of PIT on curcumin-mediated PDT in the Sulfite dehydrogenase inactivation of planktonic and biofilm cultures of three Candida species: C. albicans, C. glabrata, and C. dubliniensis. Two Candida strains obtained from American Type Culture Collection (ATCC) and one from the Centraal bureau voon Schimmelcultures (CBS) were evaluated in this study: C. albicans (ATCC 90028), C. glabrata (ATCC 2001), and C. dubliniensis (CBS 7987). All three Candida strains were maintained in a freezer
at −70 °C until the assay. Curcumin (Sigma–Aldrich, Saint Louis, Missouri, USA) was prepared with 10% of Dimethyl Sulfoxide (DMSO) to originate a stock solution, from which other solutions were prepared at final concentrations of 5.0, 10.0, 20.0, 30.0 and 40.0 μM. A light emitting diode (LED) was used to activate the PS. The LED device emitted 22.0 mW/cm2 of light intensity and 455 nm of predominant wavelength, and was designed at São Carlos Physics Institute, University of São Paulo, Brazil. Aliquots of 25 μL of each microorganism were spread in Petri dishes containing Sabouraud Dextrose Agar with chloramphenicol (SDA) and were incubated for 48 h at 37 °C. After this, a loopful of each cultivated yeasts was individually subcultured in 5 mL of Tryptic Soy Broth (TSB) and grown aerobically overnight at 37 °C. Each culture tube was centrifuged at 4000 rpm for 7 min and the supernatants were discarded.