Study of antimicrobial effects of laser-engineered SERS-active Cu@Cu₂O nanostructures and their compatibility with...

In this work, we have nanoengineered clean and nontoxic Cu@Cu₂O core-shell nanoparticles by the pulsed-laser-ablation technique and systematically evaluated their antibacterial efficacy, biocompatibility, and surface-enhanced Raman scattering (SERS) performance. The structural, optical, morphological, and elemental characterization studies were conducted using X-ray diffraction, UV-vis absorption spectroscopy, transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy. The TEM confirms the formation of Cu@Cu₂O core-shell nanoparticles with an average particle size of 5.6 nm. The quantitative assessment of antibacterial efficacy, namely, two-way ANOVA followed by post-hoc test and analysis, reveals concentration-dependent activity of the nanocomposites against both Escherichia coli and Bacillus pumilus and indicates that inhibition of bacterial growth was strong even at a concentration as low as 5 μg mL^-1. On the other hand, cell viability assays with a comprehensive 48 hour temporal study, suggest that the nanoparticles are biocompatible with human embryonic kidney (HEK-293) cells and safe for clinical applications with an appropriate dose. Furthermore, we also present SERS activity of Congo red dye molecules using the laser-synthesized Cu@Cu₂O core-shell nanoparticle substrate, for the first time, improving the limit of detection by three orders of magnitude down to a concentration of 10^-8 M. These results establish the Cu@Cu₂O core-shell nanoparticles as ideal medicinal candidates with combined antibacterial efficacy, good cellular biocompatibility, and excellent SERS activity, which are beneficial for their applications in therapeutics, sensing, and environmental monitoring.