Fig. 1. (A) A schematic diagram of this study. GNCs with a specific P12/C5 composition aggregate planktonic bacteria by interacting with the bacterial cell envelope while maintaining good biocompatibility. Local interactions of GNCs with bacteria cause cell content leakage and structural deformation, which induce cell death. The distribution of GNCs is tracked using NIR fluorescence upon excitation with an 808 nm laser. Golden spheres indicate gold atoms, red spheres indicate the P12 ligands, and blue spheres indicate the C5 ligands. (B) Time-dependent evolution of the UV-vis spectra of the 100% C5-capped GNC (representative species) during the synthesis process. (C) NIR fluorescence excitation (black line, monitored with λEM = 1100 nm) and emission (red line, λEX = 810 nm) spectra of the 100% C5-capped GNC. (D) Double spherical aberration-corrected TEM image (scale bar: 10 nm) of the 100% C5-capped GNC prepared on an ultra-thin carbon film supported copper grid. The UV-vis spectra, NIR fluorescence spectra and TEM images of GNCs with other P12/C5 compositions show no obvious differences from those of this representative species. (E) A plot of the GNC surface P12 capping ratio versus the P12 feed ratio. The red line indicates the theoretical output, assuming no ligand affinity difference, while the black dots represent the actual P12 ratio. (F) HD5/MIC values for dual-ligand GNCs prepared under different P12 feed ratios. The greater the HD5/MIC, the higher the biosafety and antibacterial ability of the material. A sudden change in haemolytic potency occurs as the feed ratio approaches 50% (the MIC value is from anti-S. aureus results). (G) Comparison of the cytotoxicity of the 45%- and 50%-P12 GNCs toward human umbilical vein endothelial cells (HUVECs) with 24 h incubation.
