Biogenic Approaches to Metal Nanoparticle Synthesis and Their Application in Biotechnology

Metal and metal oxide nanoparticles (NPs) synthesized through biologically mediated reduction of metal ions using biomolecules derived from microorganisms, algae, or plants are attracting growing attention in plant biotechnology due to their multifunctional properties and environmental advantages compared with conventional physicochemical synthesis. This review provides a comprehensive analysis of biological approaches for NP production using bacteria, fungi, algae, cyanobacteria, whole plants, and in vitro plant cell cultures. The main biosynthetic mechanisms, types of reducing and capping metabolites, metal specificity, and typical NP characteristics are described for each system, with emphasis on their relative productivity, scalability, reproducibility, and biosafety. Special consideration is given to plant cell and tissue cultures as highly promising platforms that combine the metabolite diversity of whole plants with precise control over growth conditions and NP parameters. Recent advances highlight the significance of bioengineering of reductive capacity as a novel strategy to enhance the efficiency and controllability of NP biosynthesis. Since NP formation is driven by key biomolecules, targeted modification of biosynthetic pathways through metabolic and genetic engineering can substantially increase NP yield and allow fine-tuning of their structural and functional properties. The applications of biogenic NPs in plant biotechnology are systematically evaluated, including their use as environmentally safe disinfectants for explants and seed sterilization, modulators of callus induction and morphogenesis, and abiotic elicitors that enhance the accumulation of economically valuable secondary metabolites. Remaining challenges, such as variability in NP characteristics, limited scalability, and insufficient data on phytotoxicity and environmental safety, are discussed to outline future research priorities. The synthesis-function relationships highlighted here provide a foundation for developing sustainable NP-based technologies in modern agriculture.