Sustainable synthesis of mono-, bi- and tri-metallic nanoparticles using endophytic fungi: characterization and...

Endophytic fungi represent an emerging and promising biological platform for the sustainable biosynthesis of nanoparticles within the rapidly developing field of green nanotechnology. Conventional physicochemical methods for nanoparticle production often require toxic chemicals, high energy consumption, and complex processing conditions, which raise environmental and biomedical safety concerns. In contrast, fungal endophyte-mediated synthesis provides an eco-friendly, cost-effective, and scalable alternative for generating metal and metal oxide nanoparticles. Endophytic fungi inhabit internal plant tissues without causing disease and possess diverse metabolic pathways capable of reducing metal ions into stable nanoparticles through enzymatic and biochemical processes. Various biomolecules produced by these fungi, including reductases, proteins, phenolics, flavonoids, and other secondary metabolites, act simultaneously as reducing and stabilizing agents during nanoparticle formation. As a result, nanoparticles synthesized via endophytic fungi often exhibit controlled size and morphology and improved stability. Recent studies have demonstrated the ability of different fungal endophytes to biosynthesize monometallic nanoparticles, such as silver, gold, zinc oxide, iron oxide, copper oxide, and magnesium oxide, as well as more complex bimetallic and trimetallic nanostructures. These biologically synthesized nanoparticles display remarkable functional properties that enable their applications in diverse fields. In biomedicine, they show potent antimicrobial, anticancer, antioxidant, and anti-inflammatory activities. In agriculture, they contribute to plant growth promotion, disease management, nano-fertilization, and induction of systemic resistance in crops. Furthermore, these nanomaterials demonstrate significant potential in environmental remediation, including heavy-metal removal, pollutant degradation, and wastewater treatment. This review highlights the diversity and ecological roles of fungal endophytes, their mechanisms in nanoparticle biosynthesis, the characterization of produced nanomaterials, and their advanced applications. The integration of endophytic fungi with nanotechnology offers a sustainable pathway for developing multifunctional nanomaterials capable of addressing critical challenges in medicine, agriculture, and environmental management.