Raman Tags Research Articles

High-efficiency enzyme-free catalyzed hairpin assembly-mediated homogeneous SERS and naked-eyes dual-mode assay for ultrasensitive and portable detection of mycotoxin

We developed an aptamer recognition-trigged enzyme-free catalyzed hairpin assembly (CHA) assisted signal amplification homogeneous naked-eyes and surface-enhanced Raman scattering (SERS) dual-mode sensor for highly sensitive and portable detection of Aflatoxin B1 (AFB1) in food samples. The recognition of AFB1 by aptamer induced the generation of HP1-AFB1 complexes, which hybridized with Ag+-labeled hairpin DNA (HP2) and released Ag+, subsequently initiating the enzyme-free CHA reaction by a designed helper DNA (HP3) to form double-stranded DNA (HP2-HP3) and accompanied by the release of HP1-AFB1 complexes. The released HP1-AFB1 complexes were recognized by HP2 and HP3 again to trigger cascade recycling amplification and resulted in the generation of a larger number of free Ag+ and dsDNA. Then, methylene blue as Raman tag to intercalate into dsDNA and generating strong SERS signal with the assistance of Fe3O4@Au. Meanwhile, the free Ag+ induced the AuNPs aggregation and resulted in naked-eye distinguishable color transitions from red to black blue. Benefitting from the efficiently enzyme-free CHA assisted signal amplification and portably dual-mode detection system, this work successfully proposed a novel homogeneous biosensing strategy for highly sensitive and portable detection of AFB1. The SERS intensity and visualization signals were linearly correlated with the concentration of AFB1 ranging from 0.0156 to 31.2 ng mL−1 and 0.61–39 ng mL−1, and the limit of detections were 1.6 pg mL−1 and 152 pg mL−1, respectively. This strategy was successfully applied to real samples and provided an alternative approach for the highly sensitive detection of mycotoxins.

Low background interference SERS aptasensor for highly sensitive multiplex mycotoxin detection based on polystyrene microspheres-mediated controlled release of Raman reporters

Mycotoxin contamination is a serious global issue in food safety. The accurate detection of mycotoxins in complex samples, particularly via a portable detection system that realizes multi-analyte detection, remains a great challenge. Here, a polystyrene (PS)-mediated surface-enhanced Raman scattering (SERS) aptasensor was designed for ultrasensitive and simultaneous detection of multiple mycotoxins in food samples. First, the novel Raman tags were prepared using PS as nanocontainer to encapsulate abundant Raman reporters. The PS nanocontainer with Raman reporters was then functionalized by aptamer as an effective target-recognition platform. Second, the single-strand binding protein modified magnetic nanoparticles (MNPs@SSB) were used as a magnetic capture substrate. When the target mycotoxin was present and recognized by its aptamer, the combination of PS-Apt and mycotoxins can hinder the binding between PS-Apt and MNPs@SSB. Consequently, after the magnetic separation and treatment by THF solution, fewer biological-silent reporter probes were released from PS, causing the reduction of SERS signal as a function of target mycotoxins concentration. Due to the high loading capacity of PS and the excellent signal conversion and amplification of aptamer-assisted SERS assay, the proposed strategy is reliable and ultrasensitive for the determination of multiple mycotoxins. The limit of detection was as low as 0.159 fg L−1, 2.015 fg L−1, and 1.561 fg L−1 for ZEN, OTA and AFB1, respectively. This strategy not only raises a new idea for designing novel Raman tag, but also broadens the application of SERS for multiple detection of trace target.

Gap-enhance Raman tags (GERTs) competitive immunoassay based Raman imaging for the quantitative detection of trace florfenicol in milk

Surface Enhanced Raman Spectroscopy (SERS) is a highly sensitive detection method, however, it is still challenging to directly detect florfenicol due to its low Raman activity. To solve this problem, we present a novel sensor for selective detection of florfenicol residue in milk using gap-enhance Raman tags (GERTs) competitive immunoassay. In this nanosensor, Raman reporters 4-mercaptobenzoic acid (4MBA) were embedded in the 1 nm gap of Au core-gap-Au shell nanoparticles, which can protect 4MBA molecules from unwanted external environments and provide a high enhancement. The parameters affecting the detection sensitivity were discussed and optimized. The limit detection of florfenicol in milk can reach 0.1 μg/kg. To evaluate the performance of GERTs immunoassay, Ag@4MBA tags immunoassay was conducted and the results were compared. Moreover, Raman mapping was investigated to improve the quantitative prediction model with R2 of 0.981 achieved, by eliminating the signal fluctuations caused by the inhomogeneous distribution of GERTs.

Patterned Liquid-Infused Nanocoating Integrating a Sensitive Bacterial Sensing Ability to an Antibacterial Surface.

The slippery liquid-infused surfaces show a great antibacterial property. However, most liquid-infused surfaces cannot detect whether or not the unknown aqueous samples contain microorganisms. Therefore, it is highly necessary but a challenge to integrate bacterial sensing capability into antibacterial surface. In this work, we prepared a slippery patterned liquid-infused nanocoating on the glass substrate for integrating bacterial sensing capability into the bacterial repellence surface. Dendritic mesoporous silica nanoparticles (DMSNs) with a suitable particle size of ca. 128 nm were employed as a building block to fabricate the multifunctional nanocoating with a superhydrophilic microwell and hydrophobic periphery by a dip-coating strategy, hydrophobic treatment, photomask-mediated plasma etching, and liquid infusion. Dendritic porous silica nanoparticles (DPSNs) with a larger particle size of ca. 260 nm were uniformly loaded with Au nanoparticles (NPs), providing large surface area for the modification of Raman reporter (4-mercaptobenzoic acid (4-MBA)) and aptamer. Thus, as a Raman tag, the formed DPSNs-Au-MBA-aptamer could achieve sensitive surface-enhanced Raman spectroscopy (SERS) detection of target bacteria. Combined with the Raman tag, the patterned liquid-infused nanocoating not only completely repelled bacteria on the hydrophobic area but also enabled sensitive SERS detection of Staphylococcus aureus in a very low sample volume (1 μL) with a low detection limit of 2.6 colony formation units (CFU)/mL on the antibody-modified superhydrophilic microwell. This research provided a novel and reliable strategy to construct a multifunctional nanocoating with microbial repellence and sensing capabilities.

Highly Stable, Graphene-Wrapped, Petal-like, Gap-Enhanced Raman Tags.

Gap-enhanced Raman tags (GERTs) were widely used in cell or biological tissue imaging due to their narrow spectral linewidth, weak photobleaching effect, and low biological matrix interference. Here, we reported a new kind of graphene-wrapped, petal-like, gap-enhanced Raman tags (GP-GERTs). The 4-Nitrobenzenethiol (4-NBT) Raman reporters were embedded in the petal-like nanogap, and graphene was wrapped on the surface of the petal-like, gap-enhanced Raman tags. Finite-difference time-domain (FDTD) simulations and Raman experimental studies jointly reveal the Raman enhancement mechanism of graphene. The SERS enhancement of GP-GERTs is jointly determined by the petal-like “interstitial hotspots” and electron transfer between graphene and 4-NBT molecules, and the total Raman enhancement factor (EF) can reach 1010. Mesoporous silica was grown on the surface of GP-GERTs by tetraethyl orthosilicate hydrolysis to obtain Raman tags of MS-GP-GERTs. Raman tag stability experiments showed that: MS-GP-GERTs not only can maintain the signal stability in aqueous solutions of different pH values (from 3 to 12) and simulated the physiological environment (up to 72 h), but it can also stably enhance the signal of different Raman molecules. These highly stable, high-signal-intensity nanotags show great potential for SERS-based bioimaging and multicolor imaging.

Orthogonal gap-enhanced Raman tags for interference-free and ultrastable surface-enhanced Raman scattering

Abstract Spectral interference from backgrounds is not negligible for surface-enhanced Raman scattering (SERS) tags and often influences the accuracy and reliability of SERS applications. We report the design and synthesis of orthogonal gap-enhanced Raman tags (O-GERTs) by embedding alkyne and deuterium-based reporters in the interior metallic nanogaps of core–shell nanoparticles and explore their signal orthogonality as optical probes against different backgrounds from common substrates and media (e.g., glass and polymer) to related targets (e.g., bacteria, cancer cells, and tissues). Proof-of-concept experiments show that the O-GERT signals in the fingerprint region (200–1800 cm−1) are likely interfered by various backgrounds, leading to difficulty of accurate quantification, while the silent-region (1800–2800 cm−1) signals are completely interference-free. Moreover, O-GERTs show much higher photo and biological stability compared to conventional SERS tags. This work not only demonstrates O-GERTs as universal optical tags for accurate and reliable detection onto various substrates and in complex media, but also opens new opportunities in a variety of frontier applications, such as three-dimensional data storage and security labeling.

Highly sensitive multiplex detection of foodborne pathogens using a SERS immunosensor combined with novel covalent organic frameworks based biologic interference-free Raman tags

Rapid and reliable multiplex detection of foodborne pathogens is in great demand for ensuring food safety and preventing foodborne diseases. In this study, we developed a highly sensitive SERS immunosensor for the simultaneous detection of multiple foodborne pathogens. Novel biologic interference-free Raman tags synthesized by using the covalent organic frameworks (COF) TBDP as nanocontainer to load biologic interference-free Raman reporters and specific antibodies for interested targets were used to convert and amplify signals of foodborne pathogens. In addition, lectin functionalized magnetic nanoparticles (MNPs@Con A) which could efficiently bind to the carbohydrate constituents on the surface of pathogens were prepared to capture and isolate multiple pathogens simultaneously. The recognition of the target foodborne pathogen impels the generation of sandwich-like composites of MNPs@Con A/pathogen/TBDP@Raman tags, and these composites could be quickly separated from the sample matrix with the assistance of an external magnet. Besides, a mass of Raman reporters was released by eluting the collected MNPs@Con A/pathogen/TBDP@Raman tags composites. Combined with a portable Raman system, characteristic Raman signals (2271 and 2113 cm−1) of the occupied reporters located at the biologic interference-free region were observed and used for the simultaneous detection of two different foodborne pathogenic strains. And an equal limit of detection of 101 CFU/mL was achieved for each strain. This strategy provides new insight into the application of SERS in the detection of pathogenic bacteria.

Surface Plasmon Coupled Directional Emission for Integrated Fluorescence‐Raman Biodetection: A Proof‐of‐Concept Study

AbstractThe development of multi‐functional nanoplatforms has attracted much attention. The realization of fluorescence and Raman dual‐mode bio‐detection typically needs complicated switching procedures or algorithm processes. In this work, we propose that a surface plasmon coupled emission (SPCE) technique could be used to break the bottleneck. Our approach enabled Raman spectra which would normally suffer interfered by strong fluorescence signal to be distinguished, simply by respective measurements at different angles. As a proof of concept, we prepared dual‐mode nano‐composites for measurement. Herein, in SPCE, fluorescence was sharply distributed at 46° and Raman at 50°. Attributed to the unique directional radiation feature, collection efficiency increased dramatically, with nearly 5‐fold and 14‐fold absolute intensity enhancement compared to conventional fluorescence and Raman method. Meanwhile, Raman detectability could be improved dramatically in SPCE detection in contrast to free space measurement in one single wavelength excitation device, for serious fluorescence interference to Raman tags could be eliminated.

A CRISPR-Cas12a integrated SERS nanoplatform with chimeric DNA/RNA hairpin guide for ultrasensitive nucleic acid detection.

Background: CRISPR-Cas12a has been integrated with nanomaterial-based optical techniques, such as surface-enhanced Raman scattering (SERS), to formulate a powerful amplification-free nucleic acid detection system. However, nanomaterials impose steric hindrance to limit the accessibility of CRISPR-Cas12a to the narrow gaps (SERS hot spots) among nanoparticles (NPs) for producing a significant change in signals after nucleic acid detection.Methods: To overcome this restriction, we specifically design chimeric DNA/RNA hairpins (displacers) that can be destabilized by activated CRISPR-Cas12a in the presence of target DNA, liberating excessive RNA that can disintegrate a core-satellite nanocluster via toehold-mediated strand displacement for orchestrating a promising “on-off” nucleic acid biosensor. The core-satellite nanocluster comprises a large gold nanoparticle (AuNP) core surrounded by small AuNPs with Raman tags via DNA hybridization as an ultrabright Raman reporter, and its disassembly leads to a drastic decrease of SERS intensity as signal readouts. We further introduce a magnetic core to the large AuNPs that can facilitate their separation from the disassembled nanostructures to suppress the background for improving detection sensitivity.Results: As a proof-of-concept study, our findings showed that the application of displacers was more effective in decreasing the SERS intensity of the system and attained a better limit of detection (LOD, 10 aM) than that by directly using activated CRISPR-Cas12a, with high selectivity and stability for nucleic acid detection. Introducing magnetic-responsive functionality to our system further improves the LOD to 1 aM.Conclusion: Our work not only offers a platform to sensitively and selectively probe nucleic acids without pre-amplification but also provides new insights into the design of the CRISPR-Cas12a/SERS integrated system to resolve the steric hindrance of nanomaterials for constructing biosensors.

Multifunctional theranostic nanoparticles for multi-modal imaging-guided CAR-T immunotherapy and chemo-photothermal combinational therapy of non-Hodgkin's lymphoma.

Accurate and effective tumor diagnosis, detection, and treatment are key for improving the survival rates of patients. Chimeric antigen receptor T (CAR-T) cell therapy has shown remarkable clinical success in eradicating hematologic malignancies. However, the hostile microenvironment in solid tumors severely prevents CAR-T cells from migrating and from infiltrating and killing malignant cells. Tumor microenvironment modulation strategies have attracted much attention in the field of cancer immunotherapy. Multifunctional nanoplatforms that integrate the advantages of different therapeutic techniques can allow for the multimodal synergistic treatment of tumors. In this study, a biocompatible, tumor-targeting, on-demand approach combining CAR-T cell immunotherapy and a chemo-photothermal therapy nanoplatform (FA-Gd-GERTs@Ibrutinib) based on gadolinium-loaded gap-enhanced Raman tags (Gd-GERTs) has been developed for multimodal imaging, and it provides a reliable treatment strategy for solid tumor immunotherapy via microenvironment reconstruction. In our study, folate (FA) receptor targeted molecules are used to improve the accuracy and sensitivity of computed tomography/magnetic resonance/Raman multimodal tumor imaging. The photothermal effect of the nanoprobe can promote the angiogenesis of lymphoma tissue, destroy the extracellular matrix, loosen compact tissue, stimulate chemokine secretion, and effectively enhance the infiltration ability in the case of non-Hodgkin's lymphoma, without dampening the CD19 CAR-T cell activity. The treatment results in tumor-bearing mice proved the existence of excellent synergistic therapy; photothermal therapy improves the accumulation and effector function of CAR-T cells within solid tumors. It is believed that multifunctional nanomaterials with targeted multi-modal imaging capabilities that support combination therapy can provide an efficient route for accurate diagnosis and efficient treatment.

Five-dimensional unclonable anticounterfeiting orthogonal Raman labels

We present rapid and high-throughput mass production of five-dimensional unclonable security labels consisting of alkyne-decorated Raman tags embedded inside resin-based micropatterns for high-level anticounterfeiting by microfluidic SlipChip.

Dual-enhancement and dual-tag design for SERS-based sandwich immunoassays: evaluation of a metal\u2013metal effect in 3D architecture

The design of a sandwich-type SERS immunoassay (surface-enhanced Raman spectroscopy) is demonstrated operating in dual surface enhancement and dual-tag paradigm. The capture and detection antibodies are linked to two SERS-active substrates and form together the three-dimensional (3D) structure after specific binding to interleukin 6. A variety of metal combinations is tested (Au–Ag, Au–Au, and Ag–Ag), but an enhanced electromagnetic field is generated only due to coupling of Ag and Au nanoparticles with an Au hexagonal nanoarray. The amplified in that way Raman signals improve the limit of detection over 3 times in comparison to the assay with only one SERS-active substrate. It is also shown that the proper readout of the true-positive signal can be achieved in assays with two Raman tags, and this approach also improves LOD. For the optimal combination of the metal–metal junction and Raman tags, a linear relationship between the Raman signal and the concentration of IL-6 is obtained in the range 0–1000 pg⋅mL−1with LOD of 25.2 pg mL−1and RSD < 10%. The presented proof-of-concept of the SERS immunoassay with the dual-enhancement and dual-tag opens additional opportunities for engineering reliable SERS biosensing.Graphical abstract

Improving SERS bioimaging of subcutaneous phantom in vivo with optical clearing.

Surface-enhanced Raman scattering (SERS) has proven to be a promising technique for different types of imaging including preoperative and intraoperative in vivo tumor visualization. However, the strong scattering of the turbid tissue limits its use in subcutaneous areas. In this article, we used an optical clearing technique to improve the SERS signal from a subcutaneous tumor phantom. The phantom is a 2 mm sphere of calcium alginate with incorporated petal-like gap-enhanced Raman tags. The use of optical clearing increases the SERS signal target-to-background ratio for 5 times and allow to decrease the total imaging time for at least 10 times. In addition, SERS imaging assisted with optical clearing made it possible to more precisely determine the shape and boundaries of the implanted phantom. The combination of optical clearing and SERS is a promising strategy for the clinical imaging of subcutaneous objects that are usually shielded by dermal tissue.

Changes of C≡C Triple Bond Vibration that Disclosed Non-Canonical Cytosine Protonation in i-Motif-Forming Oligodeoxynucleotides.

Non-canonical protonation at cytosine (C) in DNA is related to a formation of second order DNA structures such as i-motif, which has a role in gene regulation. Although the detailed structural information is indispensable for comprehension of their functions in cells, the protonation status of C in complicated environments is still elusive. To provide a reporter system of non-canonical protonation, we focused on the molecular vibration that could be monitored using the Raman spectroscopy. We prepared a cytosine derivative (PC) with an acetylene unit as a Raman tag, and found that the Raman signal of acetylene in PC in oligodeoxynucleotides (ODNs) changed due to protonation at the cytosine ring which shortened an acetylene bond. The signal change in i-motif-forming ODNs was also observed in crowded environments with polyethylene glycol, evidencing protonation in i-motif DNA in complicated environments. This system would be one of tracking tools for protonation in DNA structures.

Raman spectra of deuterated hydrocarbons for labeling applications

AbstractRaman spectroscopy is used for studying the composition of cell lipidome. However, the Raman approach suffers from limited distinguish power for different lipids. In recent years, isotopically labeled molecules are increasingly used to enhance the Raman resolution of similar compounds in biological samples. Here, we present Raman study of fully deuterated stearic acid (stearic‐d35), semi‐deuterated oleic acid (oleic d‐9), arachidonic acid with deuterated methine groups (arachidonic‐d8), and their hydrogenated analogs. Polarization properties and temperature dependences of CD stretching modes were investigated to reveal the capability of the isotopically shifted Raman peaks in molecular characterization. Sensitivity of Raman peaks to order–disorder transition corresponding was demonstrated for deuterated methine, methylene, and methyl groups. It was found that the isotopically shifted Raman peaks provide information about the orientation of deuterated Raman tags and their surroundings.

Raman Nanotags-Guided Intraoperative Sentinel Lymph Nodes Precise Location with Minimal Invasion.

The accurate positioning of sentinel lymph node (SLN) by tracers during surgery is an important prerequisite for SLN biopsy. A major problem of traditional tracers in SLN biopsy is the short surgery window due to the fast diffusion of tracers through the lymphatics, resulting in a misjudgment between SLN and second echelon lymph node (2nd LN). Here, a nontoxic Raman nanoparticle tracer, termed gap‐enhanced Raman tags (GERTs), for the accurate intraoperative positioning of SLNs with a sufficient surgical time window is designed. In white New Zealand rabbit models, GERTs enable precise identification of SLNs within 10 min, as well as provide the surgeon with a more than 4 h time window to differentiate SLN and 2nd LN. In addition, the ultrahigh sensitivity of GERTs (detection limit is 0.5 × 10−12 m) allows detection of labeled SLNs before surgery, thereby providing preoperative positioning information for minimally invasive surgery. Comprehensive biosafety evaluations carried out in the context of the Food and Drug Administration and International Standard Organization demonstrate no significant toxicity of GERTs, which supports a promising clinical translation opportunity of GERTs for precise SLN identification in breast cancer.

Cellular SERS structures for non-invasive study of living cells

Surface-enhanced Raman spectroscopy (SERS) is a potent and highly selective tool to chemically identify and determine the structure of molecules and materials. However, the large biomolecules and living cells are still difficult to study using modern SERS-substrates. Here we present a new approach to the geometry of the surface of plasmon nanostructures (cellular surfaces), which makes it possible to efficiently work with volumetric objects as cells or organelles. We use the scanning Raman microscope to map the SERS from the specially prepared microcapsules formed with a Layer-by-Layer deposition method and with built-in Raman tags (Indocyanine green). It demonstrated the possibility to detect SERS signal from Indocyanine green in microcapsules located in cavities, while the signal from the Raman dye in microcapsules located on a flat surface is not detected. The obtained results can be useful in biosensors applications.

Development of Bio-Functionalized, Raman Responsive, and Potentially Excretable Gold Nanoclusters.

Gold nanoparticles (AuNPs) are used experimentally for non-invasive in vivo Raman monitoring because they show a strong absorbance in the phototherapeutic window (650–850 nm), a feature that is accompanied by a particle size in excess of 100 nm. However, these AuNPs cannot be used clinically because they are likely to persist in mammalian systems and resist excretion. In this work, clustered ultrasmall (sub-5 nm) AuNP constructs for in vivo Raman diagnostic monitoring, which are also suitable for mammalian excretion, were synthesized and characterized. Sub-5 nm octadecyl amine (ODA)-coated AuNPs were clustered using a labile dithiol linker: ethylene glycol bis-mercaptoacetate (EGBMA). Upon clustering via a controlled reaction and finally coating with a polymeric amphiphile, a strong absorbance in the phototherapeutic window was demonstrated, thus showing the potential suitability of the construct for non-invasive in vivo detection and monitoring. The clusters, when labelled with a biphenyl-4-thiol (BPT) Raman tag, were shown to elicit a specific Raman response in plasma and to disaggregate back to sub-5 nm particles under physiological conditions (37 °C, 0.8 mM glutathione, pH 7.4). These data demonstrate the potential of these new AuNP clusters (Raman NanoTheranostics—RaNT) for in vivo applications while being in the excretable size window.

Simultaneous detection of dual food adulterants using graphene oxide and gold nanoparticle based surface enhanced Raman scattering duplex DNA biosensor

Development of a facile, fast, sensitive and multiplex DNA detection for the quantitative verification of food adulterant is of high significance these days. RT-PCR, and nanoparticle based fluorescence and electrochemical detection techniques have been successfully used in clinical medicine. However, requirements of pre-conditioning steps and fluorescence dye labeling in RT-PCR, inherent photobleaching and overlapping spectra of fluorescent probe in fluorescent assay, are the few drawbacks that urge to find a suitable alternative. Surface-enhanced Raman scattering (SERS) provides molecule specific fingerprint spectra, could be a strategic to resolve the limitations. Here, we report a SERS based duplex DNA detection strategy for simultaneous and quantitative detection of a meat adulterant (pork) and an endangered species – Malayan Box Turtle (MBT). In the biosensing strategy, SERS active dual platforms – graphene oxide-gold nanoparticles (GO-AuNPs) and AuNPs, and uniquely designed Raman tag intercalated short-length signal probe (SP) sequences are used. The sensing principle relies on the covalent linking of SP sequences functionalized AuNPs and capture probe (CP) functionalized GO-AuNPs via hybridization with corresponding target DNA. Coupling of multi-component platforms contributes in huge SERS signal enhancement due to electromagnetic and charge transfer mechanism. The biosensor showed an improved sensitivity in simultaneous detection of both adulterants with limit of detection (LOD) is 1 × 10−14 M. Moreover, efficiency of SERS biosensor was validated by the DNA extracted from real samples with a LOD of 1 × 10-13 M. Furthermore, the biosensing approach showed excellent sequence specificity in discriminating DNA sequences of five non-target species and specificity towards single nucleotide differentiation.

Interfacial hydration determines orientational and functional dimorphism of sterol-derived Raman tags in lipid-coated nanoparticles

Lipid-coated noble metal nanoparticles (L-NPs) combine the biomimetic surface properties of a self-assembled lipid membrane with the plasmonic properties of a nanoparticle (NP) core. In this work, we investigate derivatives of cholesterol, which can be found in high concentrations in biological membranes, and other terpenoids, as tunable, synthetic platforms to functionalize L-NPs. Side chains of different length and polarity, with a terminal alkyne group as Raman label, are introduced into cholesterol and betulin frameworks. The synthesized tags are shown to coexist in two conformations in the lipid layer of the L-NPs, identified as "head-out" and "head-in" orientations, whose relative ratio is determined by their interactions with the lipid-water hydrogen-bonding network. The orientational dimorphism of the tags introduces orthogonal functionalities into the NP surface for selective targeting and plasmon-enhanced Raman sensing, which is utilized for the identification and Raman imaging of epidermal growth factor receptor-overexpressing cancer cells.