Performance determinates and mechanism of metallic nanoparticles as antimicrobial agents: a review

Antimicrobial resistance (AMR) is one of the most serious global public health problems, and contributes to poor treatment outcomes for bacterial infections. Experimental platforms such as metallic and metal-oxide nanoparticles have been picked up as potential antimicrobial agents, as they can damage bacterial membranes, release metal ions, induce oxidative stress, disrupt proteins and nucleic acids, and interfere with biofilm formation. This is a narrative review; representative studies were selected to illustrate mechanistic diversity and performance determinants rather than through a systematic search protocol. This review summarizes commonly used nanoparticle synthesis routes such as chemical reduction, green synthesis, microwave-assisted synthesis, hydrothermal, sol–gel and biological synthesis and also discusses physicochemical determinants of antibacterial performance. Representative studies are included in this review that illustrate that antibacterial activity of nanoparticles substantially changes with size and formulation. However, the comparison among the studies remains limited due to differences in bacterial strain, assay format, inoculum, medium composition, exposure time and characterization of particles. The available literature supports the in-vitro antibacterial and antibiofilm activity for some metallic nanomaterials. Antibacterial efficacy and biocompatibility are important considerations in evaluating the potential of metallic and metal-oxide nanoparticles for antimicrobial applications. Key parameters that primarily impact these qualities and determine their overall effectiveness include shape, size, surface-to-volume ratio, surface modification, and the inhibition of biofilm formation. Nevertheless, findings summarized in this review should not be interpreted as evidence of established clinical efficacy. Key barriers could be host cell toxicity, aggregation effects, protein-corona, uncertain distribution and pharmacokinetics, nanoparticles tolerance, environmental persistence, dose standardization, production and incomplete regulatory frameworks.