SERS Tags for Biomedical Detection and Bioimaging

Abstract

Surface-enhanced Raman scattering (SERS) has emerged as a valuable technique for molecular identification. Due to the characteristics of high sensitivity, excellent signal specificity, and photobleaching resistance, SERS has been widely used in the fields of environmental monitoring, food safety, and disease diagnosis. By attaching the organic molecules to the surface of plasmonic nanoparticles, the obtained SERS tags show high-performance multiplexing capability for biosensing. The past decade has witnessed the progress of SERS tags for liquid biopsy, bioimaging, and theranostics applications. This review focuses on the advances of SERS tags in biomedical fields. We first introduce the building blocks of SERS tags, followed by the summarization of recent progress in SERS tags employed for detecting biomarkers, such as DNA, miRNA, and protein in biological fluids, as well as imaging from in vitro cell, bacteria, tissue to in vivo tumors. Further, we illustrate the appealing applications of SERS tags for delineating tumor margins and cancer diagnosis. In the end, perspectives of SERS tags projecting into the possible obstacles are deliberately proposed in future clinical translation.

Keywords: SERS tag; bioimaging; biomarkers; theranostics; tumor.

Scheme 1

Building blocks and preparation process of a SERS tag.

Figure 1

A) Optical properties of spherical plasmonic nanoparticles. (a) Extinction spectra of AuNPs with diameters ranging from 10-100 nm. (b) Extinction spectra of AgNPs with diameters ranging from 10-100 nm. (c) Extinction spectra of Au@Ag core-shell nanospheres and (d) extinction spectra of AuAg alloy nanospheres with different Ag/Au ratios. Adapted with permission from Ref. , , copyrights 2017 Elsevier, 2014 American Chemical Society. B) Optical properties of non-spherical plasmonic nanoparticles. (a) The schematic illustration of the synthesis of AuNSs and the UV-vis spectra of different AuNSs during the overgrowing process. (b) Normalized UV-vis-NIR extinction spectra of the AuTNPs with different average edge lengths. (c) Extinction spectra of AuNRs with different aspect ratios. (d) Extinction spectra of Au@Ag core-shell nanocubes with different thicknesses of Ag shells. Adapted with permission from Ref. , , , , copyrights 2018 American Chemical Society, 2009 Wiley-VCH, 2010 American Chemical Society, 2014 Royal Society of Chemistry.

Figure 2

A) The relative intensity of bioorthogonal Raman reporters with typical groups. Adapted with permission from Ref. , copyright 2012 American Chemical Society. B) The design protocol of click SERS by nanoparticle dimerization, as well as the chemical structures and Raman shifts of the used four triple bonds-based Raman reporters. Adapted with permission from Ref. , copyright 2018 American Chemical Society. C) (a) and (b) Schematic representation of a plasmonic nanocapsule encoded with five different Raman reporters and their representative SERS spectra. (c) 3D PCA score plots for the first three PCs from 26 SERS tags obtained by the combination of five different Raman reporters. Adapted with permission from Ref. , copyright 2020 American Chemical Society.

Figure 3

Representative protective coating shells: A) Schematic diagram of silica as protective to coated on the surface of plasmonic nanoparticles. B) Schematic one-step synthesis of SERS tags with PDA as protective shells. Adapted with permission from Ref. , copyright 2018 Royal Society of Chemistry. C) Schematic diagram of BSA on the surface of plasmonic nanoparticles. Adapted with permission from Ref. , copyright 2019 American Chemical Society. D) Lipid bilayer-assisted synthesis of SERS tags. Adapted with permission from Ref. , copyright 2018 American Chemical Society. E) The preparation process of Au@PB. Adapted with permission from Ref. , copyright 2017 American Chemical Society.

Figure 4

A) Schematic diagram of the sandwich-type assay for detection of nucleic acids. Adapted with permission from Ref. , copyright 2020 Elsevier. B) The schematic illustration of DNA detection with sandwich hybridization of MB, target sequence, and ultrabright SERS tags. Adapted with permission from Ref. , copyright 2016 Elsevier. C) Schematic illustration of the lateral flow strip biosensor for the simultaneous detection of two nucleic acids. (a) The strip is composed of two test lines and one control line. (b) SERS tags were captured by the specific region. (c) Corresponding DNA hybridizations for test and control lines. Adapted with permission from Ref. , copyright 2017 American Chemical Society. D) Schematic diagram of an RNase HII-mediated signal amplification platform for DNA detection based on frequency shift. Adapted with permission from Ref. , copyright 2019 American Chemical Society. E) The mechanism scheme of signal amplification by increasing the turnover rate of the SERS signal. Adapted with permission from Ref. , copyright 2019 Royal Society of Chemistry.

Figure 5

A) (a) Schematic of CHA amplification and (b) the SERS platform for quantitative detection of miRNA. Adapted with permission from Ref. , copyright 2019 Elsevier. B) Target-triggered SERS tag aggregation for miRNAs detection. (a) LNA sequences and miRNA-21 as hybridized in the Y-shaped dimers. (b) the calculated electromagnetic fields distribution of AuNPs individual and dimer. (c) Raman spectra of individuals, linear dimers, and Y-shaped dimers in the presents of target miRNA. Adapted with permission from Ref. , copyright 2017 American Chemical Society. C) (a) Schematic illustration of the multiplex SERS assay for multi-target miRNAs detection. (b) SERS spectra of the nanoprobes obtained in the presence of multiple miRNAs. Adapted with permission from Ref. , copyright 2017 American Chemical Society.

Figure 6

A) (a) Schematic diagram of the fabrication of SERS tags and (b) Schematic illustration of simultaneous detection of dual PSA with SERS-based immunoassay. Adapted with permission from Ref. , copyright 2017 American Chemical Society. B) Schematic illustration of PSA detection using an aptamer-assisted SERS sensing platform. Adapted with permission from Ref. , copyright 2021 Royal Society of Chemistry. C) Detection of protein biomarkers related to inflammation. (a) Schematic illustration of CRP detection using an optimally anti-CRP-immobilized Au nanoplate. (b) Schematic illustration of SERS-based multiplex vertical flow assay for the detection of four inflammatory biomarkers. (c) Digital single-molecule nanopillar SERS platform for parallel counting of four types of cytokines. Adapted with permission from Ref. , , , copyrights 2021 Springer Nature, 2019 American Chemical Society, 2020 Wiley-VCH.

Figure 7

A) Sandwich-type structure formed via immune recognition between the exosome, magnetic nanobead, and SERS nanoprobe. Adapted with permission from Ref. , copyright 2016 Royal Society of Chemistry. B) SERS tag-based exosomal PD-L1 detection. (a) Fe₃O₄@TiO₂/exosome, (b) Fe₃O₄@TiO₂/exosome/SERS tag, (c) scatter plots of the log [intensity] in the serum samples from the controls and the early-stage (stage I/II) and advanced (stage III/IV) patients. Adapted with permission from Ref. , copyright 2020 Elsevier. C) The principle of the SERS-based detection method of multiple exosomes. Adapted with permission from Ref. , copyright 2018 Royal Society of Chemistry. D) Phenotypic signature of Panc-1-, C3-, and SW480-derived small EVs in PBS and plasma detected by SERS assay. Adapted with permission from Ref. , copyright 2020 American Chemical Society. E) Schematic for EV phenotyping by EPAC. (a) A melanoma cell with a BRAF V600E mutation secretes EVs into circulation or cell culture medium. (b) The sample is directly injected into EPAC, where a nanomixing strategy was applied to increases EV collisions with the capture antibody and SERS nanotags and shears off non-target molecules and free SERS nanotags. (c) The characterization of EV phenotypes is performed by SERS mapping. The false-color SERS spectral images are established on the basis of the characteristic peak intensities of SERS nanotags. (d) By analyzing EV samples before, during, and after BRAF inhibitor treatment, the phenotypic evolution can be tracked to provide information on treatment responses and early signs of drug resistance. Adapted with permission from Ref. , copyright 2021 American Association for the Advancement of Science.

Figure 8

A) Different designs of SERS tags. (a) The aptamer-conjugated AuNC/SiO₂ core-shell Raman nanoprobe. (b) The gapped DIPs. (c) Schematic of in-situ hot spots formation through self-assembly of sGFP-and M3 peptide-modified AuNPs, and GFP complementation. Adapted with permission from Ref. , , . copyrights 2019 American Chemical Society, 2018 American Chemical Society, 2018 Springer Nature. B) The structure of Au@PB NPs and the Raman spectra of Au@PB NPs and HepG2 cells. Adapted with permission from Ref. , copyright 2017 American Chemical Society. C) Schematic illustration of the synthesis process and enhancement mechanism of the MGT substrate. Right panel: Raman mapping images toward PD-L1 obtained from HCC38 cells incubated with IFN-γ. Adapted with permission from Ref. , copyright 2018 American Association for the Advancement of Science. D) The sensing mechanism of the PB-caged SERS probe, and the real-time pH imaging of a single cell. Adapted with permission from Ref. , copyright 2020 American Chemical Society. E) (a) The molecular structures of 4-ethynylbenzenethiol derivatives and the corresponding Raman shift and a three-color SERS image of a single live Hela cell. (b) Synthesis strategy as well as the SERS spectra of multiplexed SERS tags by tuning the ratiometric composition of C13 and C12. Adapted with permission from Ref. , , copyrights 2016 American Chemical Society, 2018 Royal Society of Chemistry.

Figure 9

A) (a) Schematic demonstration of the conception of the combined SERS emissions (c-SERS). (b) Representative decoding image of four common bacteria by means of c-SERS. Adapted with permission from Ref. , copyright 2019 American Chemical Society. B) (a) Schematic illustration of GP-Ce6/MB-AgNPs. 4-MBN was introduced on the surface of AgNPs during the PDA polymerization process. (b) Raman mapping images in the nitrile channel (2228 cm^-1) for GP-Ce6/MB-AgNPs on MRSA, EC, 3T3 cell, MRSA + 3T3 cell, and EC + 3T3 cell. Adapted with permission from Ref. , copyright 2021 Ivyspring. C) (a) Fabrication of SERS NPs, consisting of AuNP core, IR dye coating, and silica shell, and MUC1 DNA aptamers. (b) Left: photograph of a nude athymic mouse with MDA-MB-468 tumor (R) and MDA-MB-453 (L) xenograft. Middle: Bright field image of the excised tumors. Scale bar 5 mm. Right: Ex vivo Raman image of the tumors. Adapted with permission from Ref. , copyright 2017 Wiley-VCH. D) Multiplexed Raman imaging of tumor biomarkers in breast cancer biopsies from three patients. (a) Schematic of the multiplexed biomarker imaging. (b) Raman mapping images of four pseudo-color (red, green, magenta, and blue) channels correspond to SERS tags targeting HER2, ER, PR, and EGFR, respectively. Scale bar = 50 µm. Adapted with permission from Ref. , copyright 2018 Royal Society of Chemistry. E) (a) The synthesis process of Gd-loaded GERTs (Gd-GERTs). (b) their application for in vivo CT/MRI/Raman multimodality tumor imaging. Adapted with permission from Ref. , copyright 2020 Elsevier. F) Schematic diagrams (a) and representative TEM image (b) of p-GERTs. (c) High-contrast and wide-area in vivo Raman image (3.2 × 2.8 cm²) of the hind-limb popliteal lymph node after injection of P-GERTs. Adapted with permission from Ref. , copyright 2019 Springer Nature.

Figure 10

A) (a) Illustration and the corresponding TEM image of the SERS NPs. MRI, photograph, and in vivo SERS image of liver tumors (b, genetic Myc-driven HCC mouse model) and microscopic liver tumors (c, histiosarcomas; genetic Ink4A/Arf^-/- mouse model). Adapted with permission from Ref. , copyright 2016 American Chemical Society. B) (a) Illustration and the corresponding TEM image of the SERRS nanostar. (b) In situ photograph of the exposed upper abdomen in a mouse with a pancreatic ductal adenocarcinoma in the head of the pancreas (outlined with white dotted line). Corresponding Raman images, showing SERRS nanostar signal in the macroscopically visible tumor in the head as well as small scattered foci of SERRS signal in other normal-appearing regions of the pancreas, are also shown. (c) Photographic and high-resolution Raman images of the excised pancreas from (b). Adapted with permission from Ref. , copyright 2015 American Association for the Advancement of Science. C) (a) A depiction of the structure of the targeted and nontargeted SERS NPs and (b) the Raman spectra of the SERS NPs (targeted and nontargeted) used in this study. (c) Schematic of an intraoperative imaging technique to rapidly identify residual tumors at the margins of freshly resected tissues for guiding breast-conserving surgeries. Adapted with permission from Ref. , copyright 2016 Springer Nature. D) (a) Synthesis of pH-responsive SERRS probe AuS-IR7p and the control probe AuS-IR7. (b) Illustration presenting the acidic margin-guided brain tumor surgery by intra-operatively determining tissue pH values/malignancies in tumor cutting edges. Adapted with permission from Ref. , copyright 2020 Royal Society of Chemistry.

Figure 11

A) Schematic illustration of GERTs for intraoperative detection and eradication of residual microtumors. Adapted with permission from Ref. , copyright 2018 American Chemical Society. B) starPART probes for image-guided surgical resection and intraoperative SERS-guided thermosurgical elimination of microtumors. (a) Schematic representation of starPART probes. (b) Targeted delivery of starPART probes via EPR effect in tumor. (c) Schematic illustration of image-guided surgical resection of tumors and real-time intraoperative SERS-guided thermosurgical elimination of residual microtumors. Adapted with permission from Ref. , copyright 2021 American Chemical Society. C) Schematic of ratiometric dual-spectrum assay of microRNA and multimodal collaborative tumor therapy. (a) Design of the fTDN-assisted DNA walking nanomachine for simultaneous ratiometric SERS-FL assay of miRNA-21. (b) Illustration of the developed nanodevice for miRNA detection and imaging in live cells and ACSPs-mediated multimodal synergistic therapy. Adapted with permission from Ref. , copyright 2021 American Chemical Society.