Triple-Function Au–Ag-Stuffed Nanopancakes for SERS Detection, Discrimination, and Inactivation of Multiple Bacteria

Abstract

New strategies combining sensitive pathogenic bacterial detection and high antimicrobial efficacy are urgently desirable. Here, we report smart triple-functional Au–Ag-stuffed nanopancakes (AAS-NPs) exhibiting (1) controllably oxidative Ag-etching thickness for simultaneously obtaining the best surface-enhanced Raman scattering (SERS) enhancement and high Ag-loading antibacterial drug delivery, (2) expressive Ag+-accelerated releasing capability under neutral phosphate-buffered saline (PBS) (pH ∼ 7.4) stimulus and robust antibacterial effectiveness involving sustainable Ag+ release, and (3) three-in-one features combining specific discrimination, sensitive detection, and inactivation of different pathogenic bacteria. Originally, AAS-NPs were synthesized by particle growth of the selective Ag-etched Au@Ag nanoparticles with K3[Fe­(CN)6], followed by the formation of an unstable Prussian blue analogue for specifically binding with bacteria through the cyano group. Using specific bacterial “fingerprints” resulting from the introduction of dual-function 4-mercaptophenylboronic acid (4-MPBA, serving as both the SERS tag and internal standard) and a SERS sandwich nanostructure that was made of bacteria/SERS tags/AAS-NPs, three bacteria (E. coli, S. aureus, and P. aeruginosa) were highly sensitively discriminated and detected, with a limit of detection of 7 CFU mL–1. Meanwhile, AAS-NPs killed 99% of 1 × 105 CFU mL–1 bacteria within 60 min under PBS (pH ∼ 7.4) pretreatment. Antibacterial activities of PBS-stimulated AAS-NPs against S. aureus, E. coli, and P. aeruginosa were extraordinarily increased by 64-fold, 72-fold, and 72-fold versus PBS-untreated AAS-NPs, respectively. The multiple functions of PBS-stimulated AAS-NPs were validated by bacterial sensing, inactivation in human blood samples, and bacterial biofilm disruption. Our work exhibits an effective strategy for simultaneous bacterial sensing and inactivation.

Well-Ordered Au Nanoarray for Sensitive and Reproducible Detection of Hepatocellular Carcinoma-Associated miRNA via CHA-Assisted SERS/Fluorescence Dual-Mode Sensing

“…Metal-based nanoarrays were considered as an ideal plasmonic substrate because of their favorable signal reproducibility and intense localized plasmon fields. Herein, based on our nanotechnology expertise, − we fabricated uniform and ordered Au NAs as activated biosensors for HCC-related miR-224 detection. This biosensor realized the Raman/FL dual-modal detection based on the SERS and MEF mechanism and was integrated with the CHA amplification strategy for improving the sensitivity and reliability of detection.…”

Recent Progress of Surface-Enhanced Raman Spectroscopy for Bacteria Detection

“…For example, Krishnan et al [ 76 ] synthesized bimetallic Ag@Au nanodisks, which showed greatly enhanced SERS performance with an enhancement factor up to 0.47 × 10 5 ( Figure 2 A). Zhou et al [ 77 ] reported smart triple-functional Au–Ag-stuffed nanopancakes (AAS-NPs) with multiple functions for bacteria sensing, inactivation in human blood samples and bacterial biofilm disruption ( Figure 2 B). SERS substrates made of magnetic nanocomposites can be used to separate and enrich target analytes in complex samples with the help of an external magnetic field, which not only achieves the pretreatment of complex matrix samples but also improves the SERS detection sensitivity of target analytes.…”

“… ( A ) The preparation method for Ag@Au nanodisks as SERS substrate [ 76 ]. Reproduced with permission from American Chemical Society Copyright (2022); ( B ) SERS substrate made of smart, triple-functional Au-Ag-stuffed nanopancakes for discrimination, sensitive detection and inactivation of different pathogenic bacteria [ 77 ]. Reproduced with permission from American Chemical Society Copyright (2022); ( C ) SERS substrate made of magnetic-based, flower-like silver composite microspheres (Fe 3 O 4 @SiO 2 @Ag microflowers).…”

Recent advances of Au@Ag core–shell SERS‐based biosensors

“…[ 125 ] Many different strategies have been developed for the detection of bacteria. [ 126 ] Currently, two different SERS techniques have been in use for bacterial detection. First is a label‐based SERS detection technique that uses SERS‐tags.…”