Resumo

Introduction: Silver nanoparticles play an important role in different areas, such as eletronic and medicine. However, due to the drawbacks presented by the physical and chemical approaches of synthesizing Ag NP, there has been a bias towards the so-called “eco-friendly” synthesis method. Objectives: Biological synthesis of Ag NP by three fungi isolated from São Paulo State’s (Brazil) mangrove and evaluation of its antimicrobial activity on pathogenic microorganisms important in hospital infections. Methods: The fungi coded as L-2-2, R-2BI-4 and MGE-201were cultivated in Potato Dextrose Broth at 28°C and 150 rpm for 72 h. Thereafter, the biomass was filtered and incubated at the same conditions with water (0.1 g/mL). The synthesis of Ag NP was carried out dissolving 1 mM AgNO3 into the fungal filtrate. The suspensions were kept in the dark at 25ºC and the nanoparticles formation was confirmed by Plasmon Resonance Band at 440 nm. The silver nanoparticles were characterized by TEM, size and zeta potential analysis. Antimicrobial activity was evaluated against Gram-negative and Gram-positive bacteria, as well as on Candida sp common in hospital infection, using microdilution assays. Results: Ag NP were obtained with quasi-spherical morphology and size in the range of 10-30 nm. The fungus MGE-201 showed Ag NP with positive zeta potencial. The Ag NP showed antimicrobial activity with minimal inhibitory concentrations ranging from 1 to 125 µM on both bacteria and on pathogenic fungi. Discussion and Conclusions: The Ag NP synthesized by the three fungi showed promising antimicrobial activity, and surprisingly the fungus MGE-201 induced nanoparticles formation with positive zeta potencial value , what could have novels applications, besides that proposed in the current research.