Biogenic nanosilver synthesized in Metarhizium robertsii waste mycelium extract – As a modulator of Candida albicans morphogenesis, membrane lipidome and biofilm

Abstract

Due to low efficacy of classic antimicrobial drugs, finding new active preparations attracts much attention. In this study an innovative, cost-effective and environmentally friendly method was applied to produce silver nanoparticles (AgNPs) using filamentous fungi Metarhizium robertsii biomass waste. It was shown that these NPs possess prominent antifungal effects against C. albicans, C. glabrata and C. parapsilosis reference strains. Further detailed studies were performed on C. albicans ATCC 90028. AgNPs kill curve (CFU method and esterase-mediated reduction of fluorescein diacetate); fractionally inhibitory concentration index (FICI) with fluconazole (FLC); effect on fungal cell membrane permeability (propidium iodide (PI) staining), membrane lipids profile (HPLC-MS), yeast morphotypes and intracellular reactive oxygen species level (H2DCFDA probe) were investigated. Anti-adhesive and anti-biofilm properties of AgNPs (alone and in combination with FLC) were also tested. Biosafety of AgNPs use was assessed in vitro in cytotoxicity tests against L929 fibroblasts, pulmonary epithelial A549 cell line, and red blood cells. Significant reduction in the viability of yeast cells treated with AgNPs was shown within 6 h. The proportion of C. albicans PI-positive cells increased in a dose and time-dependent manner. Changes in the qualitative and quantitative profile of cell membrane lipids, including significant decline in the quantity of most phospholipid species containing C18:2 and an increase in the amount of phospholipids containing C18:1 acyl species were observed after yeast exposure to AgNPs. CLSM images showed an enhancement in ROS intracellular accumulation in C. albicans treated with biogenic nanosilver. C. albicans transformation from yeast to hyphal forms was also reduced. AgNPs decreased adhesion of yeast to abiotic surfaces, as well as acted synergistically with FLC against sessile population. At fungicidal and fungistatic concentrations, they were non-toxic to mammalian cells. Obtained results confirm suitability of our “green synthesis” method to produce AgNPs with therapeutic potential against fungal infections.

Effective Inhibition of Candidiasis Using an Eco-Friendly Leaf Extract of Calotropis-gigantean-Mediated Silver Nanoparticles

“…Our results showed that AgNPs/CG was more efficient at suppressing the adhesion and biofilm formation of C. albicans than plant extract or AgNPs alone. Similar to our finding, several other studies demonstrated the inhibitory effect of AgNPs on C. albicans biofilm formation [8,61,66]. In addition, AgNPs biosynthesized by Dodonaea viscosa and Hyptis suoveolens leaf extracts were shown to suppress the biofilm formation of Candida spp.…”

“…Our data demonstrated the blocking of hyphal growth using AgNPs/CG. Similarly, several studies demonstrated the suppression of the C. albicans morphogenesis using AgNPs [6,8,53,61] in a mechanism that involved targeting the Ras-mediated signal transduction pathways in C. albicans through the downregulation of the expression of cell elongation gene (Ece1), hyphal inducer gene (Tec), and yeast to hyphal transition genes (Tup1 and Rfg1), which are key genes for the morphological transition [62].…”

“…The mechanism underlying the suppression of biofilm formation using AgNPs was reported to include the anti-adhesive action of AgNPs that regulate the growth of living microbial cells and the suppression of microbial adhesions gene expression [27,67,68]. In addition, AgNPs were shown to suppress blastospores and to disrupt the cell wall of both the yeast and the filamentous forms in order to cause the inhibition of biofilm formation in Candida [61,66].…”

<p>Anticandidal activity of biosynthesized silver nanoparticles: effect on growth, cell morphology, and key virulence attributes of Candida species</p>

“…Różalska et al 54 suggested that antibiofilm activity was due to the extremely easy binding and enhanced penetration of the AgNPs into the biofilm structure which disturb the lipidome of cell membranes. 54 Another possible mechanism of antibiofilm activity of AgNPs could be due to inhibition of yeast morphogenesis. Inhibition of blastospores and hyphae forms by AgNPs also lead to the suppression of biofilm formation in Candida.…”

“…Inhibition of blastospores and hyphae forms by AgNPs also lead to the suppression of biofilm formation in Candida. 54 Lara et al 55 reported that the antibiofilm effect of AgNPs was mainly due to the disruption of the cell wall and survival of both the yeast and the filamentous forms of the Candida spp.…”