Biogenic Synthesis of Selenium Nanoparticles: Structure-Activity Relationships and Antioxidant Mechanisms

Abstract

Selenium nanoparticles (SeNPs) have emerged as redox-active nanomaterials that combine the biological relevance of selenium with size-dependent physicochemical properties. This review examines biogenic SeNP production, the relationships between structural attributes and biological performance, and the mechanisms underlying antioxidant activity. Plants, bacteria, fungi, yeasts, algae, and isolated biomolecules can reduce selenium oxyanions to elemental selenium while simultaneously generating a surface corona that influences nucleation, growth, colloidal stability, cellular interactions, and toxicity. Synthesis variables—including pH, temperature, reaction time, precursor concentration, extract composition, and biomass ratio—govern particle size, morphology, crystallinity, charge, aggregation, and dissolution. These characteristics determine protein adsorption, membrane interaction, cellular uptake, intracellular selenium availability, and ultimately the balance between antioxidant and pro-oxidant effects.
At appropriate exposures, biogenic SeNPs may support glutathione peroxidase and thioredoxin reductase systems, increase glutathione, activate Nrf2–Keap1–ARE signaling, limit reactive oxygen and nitrogen species, preserve mitochondrial function, and reduce lipid, protein, and DNA oxidation. Reported applications include protection in metabolic, inflammatory, neurodegenerative, hepatic, renal, and reproductive models, as well as antimicrobial and anticancer strategies in which controlled oxidative stress may be desirable. Translation remains limited by inconsistent biological starting materials, incomplete nanoparticle characterization, variable dose reporting, insufficient pharmacokinetic evidence, and a lack of standardized long-term safety studies. Future progress requires quality-by-design synthesis, reference materials, mechanistically linked structure–activity datasets, physiologically relevant models, and transparent reporting. Biogenic SeNPs are promising antioxidant platforms, but their clinical value depends on reproducible manufacture and exposure-specific safety evaluation.