*3.1. Silver Nanoparticles (AgNPs)*

AgNPs play a significant character in the areas of biological and medical sciences. These NPs could be synthesized by various methods, such as physical, chemical, ionizing radiation methods, etc. [70]. However, all of these methods possess potential drawbacks; particularly, the chemicals utilized in AgNP synthesis through wet chemistry routes are less eco-friendly, expensive, and have high toxicity [46,77,78]. However, fabrication of AgNPs by green synthesis methods can be a better alternative as it is cost effective, non-toxic, and ecologically safe than the other synthesis methods [79]. Various studies on the biosynthesis of AgNPs using powdered basidiocarps and mycelia of different oyster mushroom species, such as *P. ostreatus, P. sajor-caju, P. florida, P. cornucopiae var. citrinopileatus, P. giganteus, P. platypus,* and *P. eous* have been reported. These basidiocarps and mycelia were soaked in distilled water, boiled, and then filtered [23–33]. The filtrate was freeze-dried to prepare aqueous extract. Various concentrations of this aqueous extract were incubated with AgNO<sup>3</sup> solution to synthesize AgNPs by the reduction of Ag<sup>+</sup> ions to Ag◦ (metal). Unboiled mycelia extract of *Pleurotus* has also been used to synthesize AgNPs [38]. In their report, they crushed the fruiting bodies and mixed them with deionized water. The content was filtered with filter paper, and then the filtrate was used to synthesize

AgNPs, with a size of 6–10 nm, with a spherical shape. Moreover, the synthesized AgNPs were further assessed for antibacterial potential against *Escherichia coli* and *Staphylococcus aureus*.

Synthesis of AgNPs was carried using *P. tuber-regium* mushroom extract and 1 mM AgNO<sup>3</sup> solution. The mixture of solutions was stirred at 90 ◦C for 2 h. Cubical and spherical shaped AgNPs, with an average size of 50 nm, were obtained as a black powder [61]. Debnath et al. synthesized spherical shaped AgNPs with the help of aqueous extract of mushroom (5 mL) and mixed with 95 mL silver nitrate (1 mM, AgNO3) solution to reduce Ag<sup>+</sup> to Ag<sup>o</sup> . This solution was kept in an incubator for 3 days at 37 ◦C, resulting in color change from light yellow to yellowish-brown. The obtained AgNPs were crystalline with a size ranging from 5 to 25 nm. Authors evaluated the antibacterial activity of AgNPs against *E. coli*, *B. subtilis*, *P. aeruginosa*, and *S. aureus* [51]. Similarly, the synthesis of predominantly spherical shaped AgNPs with a size ranging from 2 to 100 nm was carried by various researchers using mushroom extract and AgNO<sup>3</sup> solution [34,37,52,57,80].
