摘要：

Candida albicansis the most common pathogenic fungus isolated in bloodstream infections in hospitalized patients, and candidiasis represents the fourth most common infection in United States hospitals, mostly due to the increasing numbers of immune- and medically-compromised patients.C. albicanshas the ability to form biofilms and morphogenetic conversions between yeast and hyphal morphologies contribute to biofilm development and represent an essential virulence factor. Moreover, these attached communities of cells are surrounded by a protective exopolymeric matrix that effectively sheltersCandidaagainst the action of antifungals. Because of dismal outcomes, novel antifungal strategies, and in particular those targeting biofilms are urgently required. As fungi are eukaryotic, research and development of new antifungal agents has been difficult due to the limited number of selective targets, also leading to toxicity. By microwave-assisted techniques we obtained pure 1nm spherical silver nanoparticles ideal for their potential biological applications without adding contaminants. A phenotypic assay ofC. albicansdemonstrated a potent dose-dependent inhibitory effect of silver nanoparticles on biofilm formation, with an IC50of 0.089ppm. Also silver nanoparticles demonstrated efficacy when tested against pre-formedC. albicansbiofilms resulting in an IC50of 0.48ppm. The cytotoxicity assay resulted in a CC50of 7.03ppm. The ultrastructural differences visualized under SEM with silver nanoparticles treatment were changes in the surface appearance of the yeast from smooth to rough thus indicating outer cell wall damage. On the fungal pre-formed biofilm true hyphae was mostly absent, as filamentation was inhibited. TEM measurement of the cell-wall width ofC. albicansafter treatment resulted in significant enlargement (206±11nm) demonstrating membrane permeabilization. Our results demonstrate that silver nanoparticles are potent inhibitors ofC. albicansbiofilm formation. SEM observations are consistent with an overall loss of structure of biofilms mostly due to disruption of the outer cell membrane/wall and inhibition of filamentation.TEM indicates the permeabilization of the cell wall and subsequent disruption of the structural layers of the outer fungal cell wall. The anti-biofilm effects are via cell wall disruption. The online version of this article (doi:10.1186/s12951-015-0147-8) contains supplementary material, which is available to authorized users.

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