Growing oyster mushrooms (Pleurotus djamor and P. sajor-caju) on wheat straw spiked with zinc and selenium nanoparticles — made from the mushrooms' own cell extracts — significantly boosted their antioxidant and antibacterial potency. Zinc-treated P. djamor showed the strongest antioxidant activity and fought off Staph aureus, while selenium-treated versions of both species were most effective against E. coli. The method is self-contained: the mushroom makes the compounds that make it more powerful, with clear applications for food safety and natural medicine.