Fungal endophytes: Treasure trove for green synthesis of metallic nanoparticles and their biological applications

In the past years, metal nanoparticles have received considerable attention in medicine and pharmaceutical science, especially in treatment, diagnosis, and drug delivery. The synthesis, stability, and production cost of these nanoparticles have always been challenging. Green synthesis is a biological and environmentally friendly method that overcomes many limitations of old methods of producing metal nanoparticles. Using fungi is one of the best choices for green synthesis due to the high secretion of enzymes and proteins, simple cultivation, and availability. Among them, endophytic fungi are of great importance. Fungal endophytes are mainly symbionts of plants that not only help the survival of the plant but also have significant potential in the field of natural products and act as small factories producing metal nanoparticles. In this review article, an attempt has been made to investigate the ability of the most common endophytic fungal genera to synthesize metal nanoparticles such as gold, copper, zinc, iron, etc. Furthermore, different methods for characterization of the physicochemical and biological properties of synthesized nanoparticles have been discussed.