Optimizing the microbial synthesis of silver nanoparticles using Gloeophyllum striatum and their antimicrobial potential evaluation

The search for new sources of silver nanoparticles (AgNPs) is highly relevant in many fields. Mycosynthesis seems to be advantageous for large-scale production, and using brown rot fungi might be a promising solution. In this study, AgNP synthesis using Gloeophyllum striatum DSM 9592 was performed under various process conditions. The resulting AgNPs were characterized using UV/Vis, FT-IR, SEM and NTA techniques and their biological activities were determined. It was found that different synthesis conditions changed the production efficiency, which was the highest in 28 s AgNPs. Moreover, temperature and shaking conditions slightly affected the activity of the resulting AgNP types. Gram-negative bacteria were generally more susceptible to the action of AgNPs with MIC values two- or three-fold lower compared to Gram-positive strains. Pseudomonas aeruginosa was the most sensitive among tested strains with a MIC value of 1.56 µg/ml. The research was additionally extended by the biofilm formation assay for this strain. It was found that AgNPs of all types led to a reduction in biofilm-forming capability of P. aeruginosa over the tested concentration range. Haemolytic and cytotoxic activity assays showed that synthesis conditions also affected AgNP toxicity. For instance, 4 ns AgNPs were the least cytotoxic and cause less than 50% reduction of fibroblast viability in the concentration that inhibits the growth of P. aeruginosa completely. These results highlight the possible utility of mycogenic silver nanoparticles as an antibacterial agent in antiseptics or other external treatments.