Microbial secretome-mediated nanotechnology: an antibacterial strategy for future.

Biological synthesis of nanoparticles has been widely explored as a sustainable alternative to physical and chemical routes. Nevertheless, the majority of current methods are based on intact microbial cells or crude plant extracts, which leads to lack of reproducibility, biomolecular interference, and difficulties in mechanistic interpretation and scale-up. We present microbial secretome-mediated nanotechnology as a new and under researched paradigm in this review, which separates nanoparticle synthesis from cellular complexity and preserves biological precision. We quantitatively analyze the composition of microbial secretomes, redox enzymes, extracellular proteins, peptides, polysaccharides, and membrane-derived vesicles and map their respective functions in nanoparticle nucleation, growth, stabilization, and functionalization. Emerging biochemical and mechanistic evidence is creating a direct understanding of how the composition of the secretome relates to the nanoparticle morphology, surface chemistry, and bioactivity, moving beyond organism-specific reports. Notably, we critically assess secretome-mediated synthesis by comparing and contrasting it with whole-cell and plant-extract techniques, highlighting specific benefits including; enhanced batch-to-batch reproducibility, minimized polysaccharide and biomass contamination, better control over particle size and shape, reduced toxicity hazards, and increased feasibility of downstream processing and scale-up. Emerging approaches, such as secretome fractionation, omics-inspired secretome engineering, and vesicle-mediated nano-delivery, are mentioned as directions for developing tunable and application-specific nanomaterials. Altogether, the given review offers a mechanistic and translational roadmap of the microbial secretome-mediated nanotechnology, which cannot be regarded as the extension of green synthesis, but rather as a controllable bio-nanoengineering platform with significant potential in medical, agrarian, and environmental cleanup fields.