Silver nanoparticle production by the fungus Fusarium oxysporum: nanoparticle characterisation and analysis of antifungal activity against pathogenic yeasts

Kelly Ishida,Sonia Rozental,Gustavo Miranda Rocha,Talita Ferreira Cipriano,Gilberto Weissmüller,Fabio Gomes,Kildare Miranda

doi:10.1590/0074-0276130269

Abstract

The microbial synthesis of nanoparticles is a green chemistry approach that combines nanotechnology and microbial biotechnology. The aim of this study was to obtain silver nanoparticles (SNPs) using aqueous extract from the filamentous fungus Fusarium oxysporum as an alternative to chemical procedures and to evaluate its antifungal activity. SNPs production increased in a concentration-dependent way up to 1 mM silver nitrate until 30 days of reaction. Monodispersed and spherical SNPs were predominantly produced. After 60 days, it was possible to observe degenerated SNPs with in additional needle morphology. The SNPs showed a high antifungal activity against Candida and Cryptococcus , with minimum inhibitory concentration values ≤ 1.68 µg/mL for both genera. Morphological alterations of Cryptococcus neoformans treated with SNPs were observed such as disruption of the cell wall and cytoplasmic membrane and lost of the cytoplasm content. This work revealed that SNPs can be easily produced by F. oxysporum aqueous extracts and may be a feasible, low-cost, environmentally friendly method for generating stable and uniformly sized SNPs. Finally, we have demonstrated that these SNPs are active against pathogenic fungi, such as Candida and Cryptococcus .

Highlights

Nanotechnology is a rapidly expanding field and have been potentially used in a wide assortment of commercial products worldwide
The characteristics and stability of the silver nanoparticles (SNPs) were evaluated by electron and atomic force microscopy and the antifungal activity against pathogenic species of Candida and Cryptococcus was evaluated by broth microdilution and agar diffusion tests
Darkening of the medium colour occurred during the 60 days of the reaction for different silver ion concentrations compared to aqueous extract from F. oxysporum without AgNO3 solution and sterile distilled water

Summary

Introduction

Nanotechnology is a rapidly expanding field and have been potentially used in a wide assortment of commercial products worldwide. Silver nanoparticles (SNPs) have attracted specific attention due to their potential use in a range of applications, such as electronics, biosensing, clothing manufacture, food storage, paints, sunscreens, cosmetics and medical devices (Ahamed et al 2010). The fungus Fusarium oxysporum can reduce aqueous silver ions extracellularly to generate SNPs (Ahmad et al 2003). This process likely occurs through the action of both reductase enzymes and electron shuttle quinones (Durán et al 2005). Fusarium spp are filamentous fungi that are widely distributed in soil, water, subterranean and aerial plant parts, plant debris and other organic substrates (Nelson et al 1994). The characteristics and stability of the SNPs were evaluated by electron and atomic force microscopy and the antifungal activity against pathogenic species of Candida and Cryptococcus was evaluated by broth microdilution and agar diffusion tests

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