Green-synthesized cobalt-based nanoparticles: antimicrobial performance and mechanistic insights

Antimicrobial resistance poses an emerging threat to global health, compelling researchers to explore novel therapeutic approaches that overcome the limitations of conventional antibiotics. Among these alternatives, cobalt-based nanoparticles (Co-NPs) have attracted considerable interest due to their unique properties and a wide range of applications in clinical and biomedical fields, including their vigorous antimicrobial activity, drug delivery, multifunctional capabilities, and highly tunable physicochemical properties. This review discusses the antimicrobial activity of green-synthesized Co-NPs and how various synthesis parameters, such as particle size, morphology, surface functionalization, precursor selection, and reactant concentrations, affect their antimicrobial performance. Insights drawn from comparative evaluations of minimum inhibitory concentrations and zones of inhibition demonstrate clear correlations with activity against Gram-positive and Gram-negative bacteria and fungal strains. The review further examines the multifaceted mechanisms underpinning antimicrobial effects, encompassing reactive oxygen species generation, oxidative stress cascade, membrane destabilization, cobalt ion release, DNA interference, enzyme inactivation, and disruption of efflux pump systems. In addition to their antimicrobial promise, cobalt nanoparticles exhibit substantial potential in broader biomedical contexts, including targeted drug delivery, magnetic hyperthermia cancer therapy, biosensing, and medical imaging. By integrating current evidence and highlighting pivotal research gaps, this review establishes a robust foundation for the deliberate engineering of green-synthesized cobalt nanoparticles as advanced antimicrobial agents and versatile platforms for future biomedical applications.