Different optimization conditions required to enhance the reduction potential of silver nanoparticle biosynthesis via the Mycelia-free filtrate step using the fungus Aspergillus flavus

Abstract

Introduction: Fungi are one of the main approaches for synthesis of metallic nanoparticles (NPs), which can have medical and biotechnological applications such as their role in anti-bacterial, anti-cancer and various industrial activities. Objective: The current research focused on the biosynthesis of silver nanoparticles (AgNPs) using airborne fungi isolated from Al-karak general hospital operation rooms. Materials and Methods: The fungal isolate was identified at the species level by sequencing ITS as Aspergillus flavus. The confirmation and characterization of biosynthesized AgNPs were conducted using UV-Vis spectrophotometer, Zeta potential, Zeta sizer, FT-IR, XRD and transmission electron microscope (TEM) analyses. Results: The average diameter of the resulting AgNPs was 499.3 nm with a PDI value of 0.28. The zeta potential was -34.9 mV which reflects the ability of these nanoparticles to have a sufficient charge, because it is electrostatically stable and therefore resists self-assembly. TEM revealed that these biosynthesized AgNPs were regular and spherical in shape. The images of TEM showed that the size of AgNPs were smaller than those that were observed by DLS examination due the drying process that caused particle shrinkage. The average size of AgNPs were less than 40 nm. AgNPs exhibit different minimal inhibitory concentrations (MIC) against seven different bacteria (K. pneumonia, E. coli, E. cloacae, S. aureus, S. epidermidis, and Shigella sp.). The MICs ranged between 0.025 and 0.075 mg/mL with P. aeruginosa an exception which was the most resistant one, showing its MIC as   ˃ 0.125 mg/mL. Discussion and Conclusion: The results indicate that these molecules can be used as an important source for the treatment of many diseases caused by bacteria, in addition to testing these molecules in various fields such as cancer treatment and even in various biotechnological applications.