Biotransformation and applications of selenium nanoparticles for sustainable agriculture

Selenium (Se) is an essential trace element for human and plant health, yet its deficiency affects nearly one billion people globally due to low soil availability and inefficient dietary supplementation. Conventional inorganic and organic Se forms face significant challenges, including low bioavailability, potential toxicity, and poor assimilation by plants. Selenium nanoparticles (SeNPs) have emerged as a promising nano-formulation that combines the advantages of both inorganic and organic forms while mitigating their drawbacks, offering higher bioavailability, controlled release, and reduced toxicity.

This review examines the biotransformation and multifaceted applications of SeNPs in agricultural systems, with an emphasis on their synthesis, mechanisms of action, and efficacy in enhancing crop productivity, metabolite profile, nutritional quality, and stress resilience. Furthermore, we highlight the new and promising avenues of SeNPs and their application potential in modern agriculture.

This review systematically examines; 1) biological synthesis routes using bacteria, fungi, microalgae, and plants with physicochemical methods, highlighting challenges in scalability and reproducibility. 2) the mechanism of SeNPs uptake, transport, and assimilation in plants, and their efficiency in Se biofortification. 3) the role of SeNPs in promoting plant growth, photosynthesis, phytohormone modulation, and biosynthesis of primary and secondary metabolites. 4) the efficacy of SeNPs in mitigating abiotic stresses such as heavy metal toxicity, salinity, drought, heat and biotic stresses from pathogens and pests. Finally, key bottlenecks in large-scale production, environmental fate, toxicological considerations, and future directions for the sustainable integration of SeNPs into agriculture are critically discussed.