Extracellular mycosynthesis of gold nanoparticles using Trichoderma hamatum: optimization, characterization and antimicrobial activity

Abstract

Synthesis of gold nanoparticles (AuNPs) has become a needed domain of applied science. Biological method for synthesis of AuNPs by Trichoderma hamatum SU136 aqueous mycelial extract was achieved. The culture filtrate of the fungus was exposed to three different concentrations of gold chloride. The culture filtrate of the fungus was exposed to three different concentrations of gold chloride (0·25, 0·5 and 1·0 mmol l^-1 ). In all cases, the gold ions (Au³⁺ ) were reduced to Au⁰ , leading to the formation of stable AuNPs. The AuNPs were identified by UV-visible spectrometry, TEM and FT-IR. The presence of a surface plasmon band around 530 nm indicates AuNPs synthesis. Trichoderma hamatum SU136 synthesized 5-30 nm sized; spherical, pentagonal and hexagonal morphologies of AuNPs by TEM. The existence and binding of proteins with nanoparticles was approved by FT-IR study. Parameters optimization showed the smallest size of AuNPs was obtained with (0·5 mmol l^-1 gold chloride, pH 7 at 38°C). Interestingly, AuNPs exhibited antimicrobial activity against four pathogenic bacterial strains in the presence of the standard antibiotic, streptomycin.

Significance and impact of the study: Mycosynthesis of AuNPs by Trichoderma hamatum would provide some useful data for oriented biosynthesis of AuNPs. In addition, the applications of mycosynthesized AuNPs were studied against some pathogenic bacteria. Therefore, the gained results detect that these antimicrobial nanoparticles could be explored as hopeful candidates for a variety of biomedical and pharmaceutical applications. This study should provide a further prudence for the fungal-mediated synthesis of AuNPs.

Keywords: Trichoderma hamatum; pH; antimicrobial activity; gold nanoparticles; temperature, reaction time.