Biosynthesis of gold nanoparticles of distinct geometric shapes with highly functional protein coats without additional capping steps is rarely reported. This study describes green synthesis of protein-coated gold nanoparticles for the first time from the edible, mycorrhizal fungus Tricholoma crassum (Berk.) Sacc. The nanoparticles were of the size range 5-25 nm and of different shapes. Spectroscopic analysis showed red shift of the absorption maxima with longer reaction period during production and blue shift with increase in pH. These were characterized with spectroscopy, SEM, TEM, AFM, XRD, and DLS. The particle size could be altered by changing synthesis parameters. These had potent antimicrobial activity against bacteria, fungi, and multi-drug-resistant pathogenic bacteria. These also had inhibitory effect on the growth kinetics of bacteria and germination of fungal spores. These showed apoptotic properties on eukaryotic cells when tested with comet assays. Moreover, the particles are capped with a natural 40 kDa protein which was utilized as attachment sites for genes to be delivered into sarcoma cancer cells. The present work also attempted at optimizing safe dosage of these nanoparticles using hemolysis assays, for application in therapy. Large-scale production of the nanoparticles in fermentors and other possible applications of the particles have been discussed.
