Tri-functional SERS nanoplatform with tunable plasmonic property for synergistic antibacterial activity and antibacterial process monitoring

Abstract

Strategies integrating synergistic high-efficiency bacterial killing and antibacterial process monitoring capability are desirable. Herein, a tri-functional surface-enhanced Raman spectroscopy (SERS) nanoplatform, namely 4-mercaptobenzoic acid-encoded gold nanorods@silver coated with a layer of bovine serum albumin (AuNRs@Ag@4-MBA@BSA), with excellent biocompatibility, stability, tunable plasmonic property and activatable photothermal effect is introduced for Ag⁺/photothermal therapy (PTT) synergistic antibacterial activity and antibacterial process monitoring. An exogenous etchant is used to controllably model the physiological process of metallic silver biodegradation. Ag shell etching causes the surface plasmon resonance band of SERS nanotags to red-shift to near-infrared region, activates the photothermal conversion capability, and triggers PTT, which in turn accelerates Ag shell etching. The antibacterial rates for Staphylococcus aureus and Escherichia coli after 10 min treatment can achieve 99.5% and 99.9%, respectively. Furthermore, the near-field effect and ultrasensitive property render the SERS intensity decrease ratio is dependent on Ag shell etching as well as temperature rising and thus relevant to antibacterial activity. We have demonstrated a strong correlation between SERS signal and antibacterial effect, and have verified the possibility of antibacterial process monitoring in vitro using SERS-based methodology. We envision that our integrated strategy being used for in vivo high-efficiency bacterial killing and antibacterial process monitoring.

Keywords: Monitoring; Photothermal therapy; SERS; Synergistic antibacterial activity; Tri-functional; Tunable plasmonic property.