Biodirected Synthesis of Silver Nanoparticles Using Aqueous Honey Solutions and Evaluation of Their Antifungal Activity against Pathogenic Candida Spp.

Grzegorz Czernel,Monika Kędzierska-Matysek,Jolanta Cieśla,Mariusz Florek,Mariusz Gagoś,Dominika Bloch,Arkadiusz Matwijczuk

doi:10.3390/ijms22147715

Abstract

Silver nanoparticles (AgNPs) were synthesized using aqueous honey solutions with a concentration of 2%, 10%, and 20%—AgNPs-H2, AgNPs-H10, and AgNPs-H20. The reaction was conducted at 35 °C and 70 °C. Additionally, nanoparticles obtained with the citrate method (AgNPs-C), while amphotericin B (AmB) and fluconazole were used as controls. The presence and physicochemical properties of AgNPs was affirmed by analyzing the sample with ultraviolet–visible (UV–Vis) and fluorescence spectroscopy, scanning electron microscopy (SEM), and dynamic light scattering (DLS). The 20% honey solution caused an inhibition of the synthesis of nanoparticles at 35 °C. The antifungal activity of the AgNPs was evaluated using opportunistic human fungal pathogens Candida albicans and Candida parapsilosis. The antifungal effect was determined by the minimum inhibitory concentration (MIC) and disc diffusion assay. The highest activity in the MIC tests was observed in the AgNPs-H2 variant. AgNPs-H10 and AgNPs-H20 showed no activity or even stimulated fungal growth. The results of the Kirby–Bauer disc diffusion susceptibility test for C. parapsilosis strains indicated stronger antifungal activity of AgNPs-H than fluconazole. The study demonstrated that the antifungal activity of AgNPs is closely related to the concentration of honey used for the synthesis thereof.

Highlights

IntroductionCandidiasis is one of the most common infections in the world
In this study, we investigated their activity against two opportunistic pathogenic C. albicans and C. parapsilosis species
The present study focused on the synthesis of AgNPs with the use of aqueous honey solutions in the specified concentration and temperature conditions

Summary

Introduction

Candidiasis is one of the most common infections in the world. The disease is caused by the Candida albicans and Candida non-albicans groups. C. albicans is the most prevalent yeast species in oral, genital, and skin infections (≥90%). It is responsible for severe systemic mycoses in immunosuppressed patients. Candida parapsilosis is an important factor in catheter-related yeast bloodstream infections. The main factor in C. parapsilosis virulence is its ability to colonize artificial surfaces, which is associated with the ability of this yeast to form biofilms. The species is regarded as an important etiological factor of nosocomial infections in patients undergoing medical procedures that require the use of vascular catheters and tubing [1]. The administration of a wide range of antifungal drugs (e.g., amphotericin B and azoles) has been found to increase drug resistance [2]

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Conclusion