Fabrication of Au@Ag core–shell NPs as enhanced CT contrast agents with broad antibacterial properties

• We develop a novel kind of m-PEG-Au@Ag core–shell nanoparticles.
• m-PEG-Au@Ag nanoparticles showed tunable optical properties.
• m-PEG-Au@Ag nanoparticles exhibited low cytotoxicity and significant CT contrast ability both in vitro and in vivo.
• These nanoparticles showed remarkable antibacterial properties to both GN and GP bacteria.

Au@Ag core–shell nanoparticles (NPs) integrating both antibacterial and X-ray attenuation capabilities were facilely synthesized in aqueous solution. These NPs modified with methoxy-PEG-SH (m-PEG) on the surface rendered them favorable dispersity and stability in water, resulting in enhancement of their blood circulation time. X-ray photoelectron spectroscope (XPS) and high-resolution transmission electron microscope (HRTEM) results confirmed the core–shell structure of m-PEG-Au@Ag NPs. The m-PEG-Au@Ag NPs showed low cytotoxicity and strong X-ray absorption potency in vitro. Further in vivo study showed that as-synthesized NPs offered a pronounced contrast and prolonged their circulation time in the blood stream with negligible toxic effect in vivo. Besides, m-PEG-Au@Ag NPs had significant bacteriostatic effect toward common bacteria like Escherichia coli and Staphylococcus aureus as demonstrated by broth dilution assay. Given their low-cytotoxicity and high CT attenuation efficacy, m-PEG-Au@Ag NPs had a promising potential for use as CT enhancing and antibacterial agents.

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