Bacterial infection has continued to be a leading cause of death or disability worldwide because of antibiotic resistance. Antibiotic agents specific to certain taxa of bacteria, i.e., narrow-spectrum antibiotics, have become useful because they can kill bacteria without resulting in broad-spectrum drug resistance. In this study, we describe a series of antibiotics based on combining gold nanoparticles (AuNPs) with aminosaccharides, even though these AuNPs or aminosaccharides by themselves are ineffective against any bacteria. The AuNP-based multivalent aminosaccharides can effectively and selectively inhibit the growth of Gram-positive bacteria (including drug-resistant superbacteria). In particular, aminosaccharide-modified AuNPs are effective against methicillin-resistant Staphylococcus aureus (MRSA), a particularly hard-to-treat strain. This report carves out a way to explore antibiotics by combining AuNPs and an aminosaccharide as multivalent nanostructures, neither of which by itself is effective as an antibiotic.

In the light of the current problems of silver nanoparticles (Ag NPs) in terms of antibacterial performance, we have designed a novel trimetallic core/shell nanostructure with AgPt alloy nanodots epitaxially grown on gold nanorods (Au@PtAg NRs) as a potential antibacterial agent. Both Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were studied. The antibacterial activity exhibits an obvious composition-dependence. On increasing the Ag fraction in the alloy shell up to 80%, the antibacterial activity gradually increases, demonstrating a flexible way to tune this activity. At 80% Ag, the antibacterial activity is better than that of a pure Ag shell. The improved antibacterial ability mainly results from the high exposure of silver on the shell surface due to the dot morphology. We thus demonstrate that forming alloys is an effective way to improve antibacterial activity while retaining high chemical stability for Ag-based nanomaterials. Furthermore, due to the tunable localized surface plasmonic response in the near-infrared (NIR) spectral region, additional control over antibacterial activity using light—such as photothermal killing and photo-triggered silver ion release—is expected. As a demonstration, highly enhanced antibacterial activity is shown by utilizing the NIR photothermal effect of the nanostructures. Our results indicate that such tailored nanostructures will find a role in the future fight against bacteria, including the challenge of the increasing severity of multidrug resistance.