Atomic-engineering Au-Ag nanoalloys for screening antimicrobial agents with low toxicity towards mammalian cells.

Silver nanoparticles (AgNPs) have shown potent antibacterial activity against numerous bacteria strains. However, their toxicity against mammalian cells is still a big challenge, limiting their in vivo applications. Here, we found that alloying Ag and Au in an atomic level to form Au-Ag nanoalloys (NAs) could effectively reduce the cytotoxicity of AgNPs, and the antimicrobial activity of NAs could be well maintained by tuning the composition of Ag. By means of a facile and robust laser-based technique, which involves the laser ablation of metal films toward water (LATW), we fabricated a series of Au-Ag NAs with different elemental compositions. Precise control over the compositions of Au and Ag was achieved via adjusting the thickness ratio of ablated Au/Ag films. Following the systematic examinations of these NAs on their antibacterial performance and the toxicity against the normal mammalian cells, we found that significant bactericidal effect with negligible cytotoxicity could be achieved with the NAs bearing 40 % of Au and 60 % Ag. Furthermore, Au-Ag NAs displayed a lower cytotoxicity than their corresponding monometallic NP mixtures due to the decreased Ag+ release from alloying structures of Au-Ag. This work showed the great potential of Au-Ag NAs in in vivo applications to fight against bacterial infections.