In comparison with gold nanoparticles, the antimicrobial activity of MHA-AuNCsis attributed to their ultra-small size for the improvement of interaction with bacteria. After theinternalization of MHA-AuNCs in bacteria, the interaction between MHA-AuNCs and bacteriacould cause a metabolic imbalance to result in the increase of intracellular ROS production toeventually kill bacteria (Figure 1)