(MeOPhSe)2, a synthetic organic selenium compound, inhibits virulence factors of Candida krusei: Adherence to cervical epithelial cells and biofilm formation.

BACKGROUND: Systemic candidiasis is produced by Candida albicans or non-albicans Candida species, opportunistic fungi that produce both superficial and invasive infections. Despite the availability of a wide range of antifungal agents for the treatment of candidiasis, failure of therapy is observed frequently, which opens new avenues in the field of alternative therapeutic strategies. METHODS: The effects of p,p'-methoxyl-diphenyl diselenide [(MeOPhSe)2], a synthetic organic selenium (organochalcogen) compound, were investigated on virulence factors of C. krusei and compared with its antifungal effects on the virulence factors related to adhesion to cervical epithelial cell surfaces with C. albicans. RESULTS: (MeOPhSe)2, a compound non-toxic in epithelial (HeLa) and fibroblastic (Vero) cells, inhibited the growth in a dose-dependent manner and changed the kinetics parameters of C. krusei and, most importantly, extending the duration of lag phase of growth, inhibiting biofilm formation, and changing the structure of biofilm. Also, (MeOPhSe)2 reduced C. albicans and C. krusei adherence to cervical epithelial cells, an important factor for the early stage of the Candida-host interaction. The reduction was 37.24 ± 2.7 % in C. krusei (p = 0.00153) and 32.84 ± 3.2 % in C. albicans (p = 0.0072) at 20 µM (MeOPhSe)2, and the effect is in a concentration-dependent manner. Surprisingly, the antifungal potential on adhesion was similar between both species, indicating the potential of (MeOPhSe)2 as a promising antifungal drug against different Candida infections. CONCLUSION: Overall, we demonstrated the potential of (MeOPhSe)2 as an effective antifungal drug against the virulence factors of Candida species.

Diphenyl diselenide suppresses key virulence factors of Candida krusei, a neglected fungal pathogen.

Candida krusei is a candidiasis etiological agent of relevance in the clinical setting because of its intrinsic resistance to fluconazole. Also, it has opened up new paths in the area of alternative therapeutic techniques. This project demonstrated the effects of diphenyl diselenide (PhSe)2 and p-cloro diphenyl diselenide (pCl-PhSe)2, two organochalcogen compounds, on relevant virulence factors for the early stage of the C. krusei host interaction and infection process. Both compounds inhibited adherence of C. krusei to both polystyrene surfaces and cervical epithelial cells and biofilm formation; the structure of the biofilm was also changed in a dose-dependent manner. In addition, both compounds inhibited C. krusei growth, but (PhSe)2 significantly increased the time duration of the lag phase and delayed the start of the exponential phase in growth kinetics. (PhSe)2 has more potential antifungal activity than (pCl-PhSe)2 in inhibiting the adherence to epithelial cells, biofilm formation, and growth of C. krusei.

BSA nanoparticles loaded-methylene blue for photodynamic antimicrobial chemotherapy (PACT): effect on both growth and biofilm formation by Candida albicans.

It has been demonstrated an increase in resistance of Candida albicans to conventional therapies, probably, due the indiscriminate use of the conventional antifungal drugs. In this aspect, the nanotechnology generates the possibility of creating new therapeutic agents. Thus, the objective of this paper was to produce and characterize a bovine serum albumin (BSA) nanoparticle encapsulated with Methylene Blue (MB). In addition, the effect of BSA nanoparticles encapsulated with MB (BSA-MB) was evaluated on both growth and biofilm formation by C. albicans by Photodynamic Antimicrobial Chemotherapy (PACT) protocols. The BSA-MB nanoparticles were prepared by the desolvation process. The nanoparticulate system was studied by steady-state techniques, scanning electron microscopy and their biological activity was evaluated in vitro both growth and biofilm formation by C. albicans. The synthetized BSA-MB nanoparticles were spherical in shape exhibiting a 100-200 nm diameter with a low tendency to aggregate (PDI values < 0.2). MB photophysical properties were shown to be preserved after BSA encapsulation. A significant reduction in C. albicans growth, after PACT was observed, in a dependent manner on MB-loaded in BSA nanoparticles concentration used. It was observed an inhibition of 23, 65 and 83% in the presence of MB-loaded in BSA nanoparticles 0.1, 0.5 and 1.0 µg.mL-1, respectively. In addition, MB-loaded BSA nanoparticles 0.5 µg.mL-1 were able to reduce both biofilm formation (80%) and the transition from yeast to filamentous form by C. albicans. The results presented here demonstrated a potentiation of the phototoxic effect of MB after BSA encapsulation, since the concentrations of MB-loaded BSA nanoparticles necessary to inhibits ∼50% of C. albicans development was 10 times minor than that observed for free MB. Taken together, these results suggest the potential of PACT, using MB-loaded BSA nanoparticles in inhibiting C. albicans development. The synthesis and design of BSA nanoparticles can be successfully applied for MB encapsulation and offer the possibility to drive the toxicity effect to a specific target, as an evaluation on both growth and biofilm formation by Candida albicans.

Gelatin nanoparticles loaded methylene blue as a candidate for photodynamic antimicrobial chemotherapy applications in Candida albicans growth.

Gelatin nanoparticles (GN) with an intrinsic antimicrobial activity maybe a good choice to improve the effectiveness of photodynamic antimicrobial chemotherapy (PACT). The aim of this study was to development gelatin nanoparticles loaded methylene blue (GN-MB) and investigate the effect of GN-MB in the Candida albicans growth by PACT protocols. The GN and GN-MB were prepared by two-step desolvation. The nanoparticulate systems were studied by scanning electron microscopy and steady-state techniques, the in vitro drug release was investigated, and we studied the effect of PACT on C. albicans growth. Satisfactory yields and encapsulation efficiency of GN-MB were obtained (yield = 76.0% ± 2.1 and EE = 84.0% ± 1.3). All the spectroscopic results presented here showed excellent photophysical parameters of the studied drug. Entrapment of MB in GN significantly prolongs it's in vitro release. The results of PACT experiments clearly demonstrated that the photosensitivity of C. albicans was higher when GN-MB was used. Gelatin nanoparticles loaded methylene blue-mediated photodynamic antimicrobial chemotherapy may be used against Candida albicans growth.

Photodynamic antimicrobial chemotherapy (PACT) using toluidine blue inhibits both growth and biofilm formation by Candida krusei.

Among non-albicans Candida species, the opportunistic pathogen Candida krusei emerges because of the high mortality related to infections produced by this yeast. The Candida krusei is an opportunistic pathogen presenting an intrinsic resistance to fluconazol. In spite of the reduced number of infections produced by C. krusei, its occurrence is increasing in some groups of patients submitted to the use of fluconazol for prophylaxis. Photodynamic antimicrobial chemotherapy (PACT) is a potential antimicrobial therapy that combines visible light and a nontoxic dye, known as a photosensitizer, producing reactive oxygen species (ROS) that can kill the treated cells. The objective of this study was to investigate the effects of PACT, using toluidine blue, as a photosensitizer on both growth and biofilm formation by Candida krusei. In this work, we studied the effect of the PACT, using TB on both cell growth and biofilm formation by C. krusei. PACT was performed using a light source with output power of 0.068 W and peak wavelength of 630 nm, resulting in a fluence of 20, 30, or 40 J/cm2. In addition, ROS production was determined after PACT. The number of samples used in this study varied from 6 to 8. Statistical differences were evaluated by analysis of variance (ANOVA) and post hoc comparison with Tukey-Kramer test. PACT inhibited both growth and biofilm formation by C. krusei. It was also observed that PACT stimulated ROS production. Comparing to cells not irradiated, irradiation was able to increase ROS production in 11.43, 6.27, and 4.37 times, in the presence of TB 0.01, 0.02, and 0.05 mg/mL, respectively. These results suggest that the inhibition observed in the cell growth after PACT could be related to the ROS production, promoting cellular damage. Taken together, these results demonstrated the ability of PACT reducing both cell growth and biofilm formation by C. krusei.

Photodynamic Antimicrobial Chemotherapy (PACT), using Toluidine blue O inhibits the viability of biofilm produced by Candida albicans at different stages of development.

BACKGROUND: Candida albicans is an opportunistic fungus producing both superficial and systemic infections, especially in immunocompromised individuals. It has been demonstrated that C. albicans ability to form biofilms is a crucial process for colonization and virulence. Furthermore, a correlation between the development of drug resistance and biofilm maturation at Candida biofilms has been shown. Photodynamic Antimicrobial Chemotherapy (PACT) is a potential antimicrobial therapy that combines visible light and a non-toxic dye, known as a photosensitizer, producing reactive oxygen species (ROS) that can kill the treated cells. The objective of this study was to investigate the effects of PACT, using Toluidine Blue O (TBO) on the viability of biofilms produced by C. albicans at different stages of development. METHODS: In this study, the effects of PACT on both biofilm formation and viability of the biofilm produced by C. albicans were studied. Biofilm formation and viability were determined by a metabolic assay based on the reduction of XTT assay. In addition, the morphology of the biofilm was observed using light microscopy. RESULTS: PACT inhibited both biofilm formation and viability of the biofilm produced by C. albicans. Furthermore, PACT was able to decrease the number of both cells and filamentous form present in the biofilm structure. This inhibitory effect was observed in both early and mature biofilms. CONCLUSIONS: The results obtained in this study demonstrated the potential of PACT (using TBO) as an effective antifungal therapy, including against infections associated with biofilms at different stages of development.