Recent advances of Au@Ag core-shell SERS-based biosensors

Abstract

The methodological advancements in surface-enhanced Raman scattering (SERS) technique with nanoscale materials based on noble metals, Au, Ag, and their bimetallic alloy Au-Ag, has enabled the highly efficient sensing of chemical and biological molecules at very low concentration values. By employing the innovative various type of Au, Ag nanoparticles and especially, high efficiency Au@Ag alloy nanomaterials as substrate in SERS based biosensors have revolutionized the detection of biological components including; proteins, antigens antibodies complex, circulating tumor cells, DNA, and RNA (miRNA), etc. This review is about SERS-based Au/Ag bimetallic biosensors and their Raman enhanced activity by focusing on different factors related to them. The emphasis of this research is to describe the recent developments in this field and conceptual advancements behind them. Furthermore, in this article we apex the understanding of impact by variation in basic features like effects of size, shape varying lengths, thickness of core-shell and their influence of large-scale magnitude and morphology. Moreover, the detailed information about recent biological applications based on these core-shell noble metals, importantly detection of receptor binding domain (RBD) protein of COVID-19 is provided.

Keywords: Au@Ag core–shell nanoparticles; SERS probes; biosensors.

FIGURE 1

A schematic representation of three processes: (A) fabrication process, (B) enhancement study, (C) functionalization with antibody and receptor binding domain detection by SERS. Reproduced under the terms of the CC BY 4.0 license.^{[ 117c ]} Copyright 2021, The Authors.

FIGURE 2

Schematic illustration of the operating procedures for bacterial detection via a SERS sandwich strategy, in which AMP modified magnetic Fe₃O₄ NPs were utilized in the bacteria capture and 4‐MPBA modified Au@Ag‐GO nanocomposites were used as SERS tags. (A) AMP modified Fe₃O₄ NPs were cultured with a bacterial sample matrix, which included bacteria, blood cells, or other interference. (B) The Fe₃O₄ NPs@bacteria complex was magnetically separated from the sample matrix. (C) Blood cells or any other interference were removed. (D) 4‐MPBA modified Au@Ag‐GO nanocomposite SERS tags were cultured with the Fe₃O₄ NPs@bacteria complex to form a sandwich structure. (E) The Fe₃O₄ NPs/bacteria/SERS tags sandwich structure was magnetically separated and detected by the Raman spectrometer. (F) Different kinds of bacteria were discriminated according to their Raman “fingerprints.” (G) 4‐MPBA can be used as an IS to correct the SERS intensities. Reproduced under the terms of the CC BY‐NC 3.0 license.^{[ 130 ]} Copyright 2018, Kaisong Yuan et al.

FIGURE 3

Schematic description of the proposed integrated multiple nano‐platform. (A) Fabrication of UCNPs@QAS by grafting quaternary ammonium salt (QAS) onto up‐conversion nanoparticles (UCNPs) via an amidation reaction. (B) Fabrication process of MAu@Ag@MPBA. (C) Isolation and detection of E. coli, S. aureus, and Salmonella via dual‐mode sensing. Reproduced with permission.^{[ 134 ]} Copyright 2021, Elsevier

FIGURE 4

Schematic illustration of the proposed SERS sensor based on Au@Ag NPs solid‐phase substrate. (A) Preparation of Au@Ag NPs by seed‐mediated two‐step growth method. (B) Bacterial SERS spectral processing and quantification. Reproduced with permission.^{[ 137 ]} Copyright 2022, Elsevier

FIGURE 5

Illustration of Au NBP@Ag NR‐MBA‐rBSA‐FA nanoprobes for SERS detection of living cancer cell. (A) Fabrication of Au NBP @ Ag NR‐MBA‐rBSA‐FA nanoprobes; (B) target cancer cells detection. Reproduced with permission.^{[ 142 ]} Copyright 2019, Elsevier

FIGURE 6

The workflow of operating on the platform for (A) add samples, (B) circulating tumor cells capture, (C) add SERS aptamer‐vectors, (D) gather SRES spectrum, (E) profiling of cell phenotype classification based on SERS signatures. Reproduced with permission.^{[ 145 ]} Copyright 2018, John Wiley & Sons

FIGURE 7

Schematic illustrations (A) for the fabrication of three different PEGylated Ag–Au hollow nanospheres which are environmentally stable under various pH values, temperatures, and salt concentrations, and (B) for simultaneous detection of three different biomarkers expressed in breast cancer cells using SERS mapping techniques. Reproduced with permission.^{[ 147 ]} Copyright 2020, Elsevier

FIGURE 8

(A) Synthetic route for dual dye‐loaded SERS tags. (B) Schematic illustration of quantitative detection of human IgM using SERS‐based. Reproduced under the terms of the CC BY 3.0 license.^{[ 154 ]} Copyright 2018, Xiaofei Jia et al.

FIGURE 9

Schematic illustration of ultrasensitive determination of AFB1 based on combining multifunctional capture probes (Fe₃O₄@Au NFs‐cDNA) with strong Raman signals of reporter probes. (A) Functionalization of Fe₃O₄@Au NFs with Cdna. (B) Synthesis of reported probe 1 (Au‐4MBA@Ag NSs‐Apt) and reporter probe 2 (Cy3‐Apt). (C) SERS detection of AFB1 at different concentrations using the laser confocal Raman microscope. Reproduced with permission.^{[ 170 ]} Copyrights 2020, Elsevier

FIGURE 10

Schematic representation of the universal surface‐enhanced Raman scattering (SERS) aptasensor platform for trace detection. PEI, polyethyleneimine; AA, ascorbic acid. (A) Fabrication of monodispersed Fe₃O₄@Au MNPs and functionalization it with SH‐cDNA. (B) Synthesis of Au@DTNB@Ag CS and functionalization it with SH‐Apt. (C) Preparation of the SERS aptasensor for ZEN detection. Reproduced with permission.^{[ 175 ]} Copyrights 2021, Elsevier

FIGURE 11

The methodological approach for melanoma biomarker detection using microchip‐SERS platform. (A) Extraction of protein lysate and immunoprecipitation of pure MCSP protein. (B) ac‐EHD induced nanofluidic mixing for specific MCSP protein capture. (C) SERS labeling of target MCSP with the anti‐MCSP conjugated SERS nanotags with ac‐EHD nanomixing. (D) The molecules are excited with laser for Raman scattering and a characteristic peak is obtained at 1075 cm1, peak height corresponds to the concentration of the target antigen. Reproduced under the terms of the CC BY‐NC 3.0 license.^{[ 184 ]} Copyright 2020, Aswin Raj Kumar et al.

FIGURE 12

Principle diagram of the colorimetric and SERS dual‐mode probe for determination of Hg²⁺ based on controllable etching unmodified Au@Ag NPs. Reproduced with permission.^{[ 196 ]} Copyright 2021, Elsevier

FIGURE 13

Schematic diagrams of (A) the formation of major allergenic determinant (penicilloyl) and P protein from penicillin drugs, (B) the mechanism of antibody‐mediated hypersensitivity reaction, and (C) the alkyne response‐based SERS immunoassay for P‐protein. Reproduced with permission.^{[ 209 ]} Copyright 2021, Elsevier

FIGURE 14

Schematic illustration of microRNA SERS detection based on DSN‐assisted target recycling signal amplification. (A) The synthesis process of Fe₃O₄@Ag‐SERS tags. (B) DSN‐assisted SERS detection of microRNA. Reproduced with permission.^{[ 213 ]} Copyright 2019, Elsevier