Surface-enhanced Raman Scattering Labels Research Articles

Surface-Enhanced Raman Scattering Nanosensing and Imaging in Neuroscience.

Monitoring neurochemicals and imaging the molecular content of brain tissues in vitro, ex vivo, and in vivo is essential for enhancing our understanding of neurochemistry and the causes of brain disorders. This review explores the potential applications of surface-enhanced Raman scattering (SERS) nanosensors in neurosciences, where their adoption could lead to significant progress in the field. These applications encompass detecting neurotransmitters or brain disorders biomarkers in biofluids with SERS nanosensors, and imaging normal and pathological brain tissues with SERS labeling. Specific studies highlighting in vitro, ex vivo, and in vivo analysis of brain disorders using fit-for-purpose SERS nanosensors will be detailed, with an emphasis on the ability of SERS to detect clinically pertinent levels of neurochemicals. Recent advancements in designing SERS-active nanomaterials, improving experimentation in biofluids, and increasing the usage of machine learning for interpreting SERS spectra will also be discussed. Furthermore, we will address the tagging of tissues presenting pathologies with nanoparticles for SERS imaging, a burgeoning domain of neuroscience that has been demonstrated to be effective in guiding tumor removal during brain surgery. The review also explores future research applications for SERS nanosensors in neuroscience, including monitoring neurochemistry in vivo with greater penetration using surface-enhanced spatially offset Raman scattering (SESORS), near-infrared lasers, and 2-photon techniques. The article concludes by discussing the potential of SERS for investigating the effectiveness of therapies for brain disorders and for integrating conventional neurochemistry techniques with SERS sensing.

SERS detection platform based on a nucleic acid aptamer-functionalized Au nano-dodecahedron array for efficient simultaneous testing of colorectal cancer-associated microRNAs

A surface-enhanced Raman scattering (SERS) detection platform was constructed based on Au nano-dodecahedrons (AuNDs) functionalized with nucleic acid aptamer-specific binding and self-assembly techniques. SERS labels were prepared by modifying Raman signaling molecules and complementary aptamer chains and were bound on the aptamer-functionalized AuNDs array. Using this protocol, the limits of detection (LODs) of miR-21 and miR-18a in the serum were 6.8 pM and 7.6 pM, respectively, and the detection time was 5 min. Additionally, miR-21 and miR-18a were detected in the serum of a mouse model of colorectal cancer. The results of this protocol were consistent with quantitative real-time polymerase chain reaction (qRT-PCR). This method provides an efficient and rapid method for the simultaneous testing of miRNAs, which has great potential clinical value for the early detection of colorectal cancer (CRC).

Exploring the generality of ligands for Silica-Encapsulated nanoclusters as SERS labels

The surface enhanced Raman scattering (SERS) reporters are rather limited, and the Raman peaks still overlap in varying degrees, making SERS multiplex coding a critical bottleneck in the exploration of SERS nanotechnology. Herein, we design a general strategy to expand the SERS probe scope to 26 probes of six types, which can be further expanded within a limited range, with stable performance and structure. By constructing (Au-aggregate)@Ag@silica and (Au-aggregate)@silica nanocomposites, we develop optimal enhancement strategies for each Raman molecules. Mixed signal-ligand SERS probes improve the complexity of Raman spectra and expand the coding capacity. By integrating the strategies, SERS inks are produced and applied in anti-counterfeiting. With these improvements, this work breaks the constrains of probe selection, bringing SERS one step closer to the sensor or anti-counterfeiting application.

Recent Progress in SERS‐Based Anti‐counterfeit Labels

AbstractAnti‐counterfeit labels protect many commercial goods, drugs, and currencies from counterfeiting activities. Recently, the designs of anti‐counterfeit labels have emerged utilizing surface‐enhanced Raman scattering (SERS) as a powerful technique, in which SERS‐active materials provide strong Raman signals of probe molecules. These signals are unique and, so far, have rarely been used in practical anti‐counterfeit labels applications. In this review, the general methodology of using Raman and SERS in designing anti‐counterfeit labels is first introduced. Then, two types of secret information in SERS labels, spectroscopic information and graphical information, are detailed and discussed with a focus on how the molecular information is encoded with SERS labels. Later, several advanced SERS labels are presented which combine existing security features such as barcode, quick response code, fluorescence, and unclonable features. Finally, the challenges in building usable SERS anti‐counterfeit labels are discussed and possible research directions are described.

Combination of bacitracin-based flocculant and surface enhanced Raman scattering labels for flocculation, identification and sterilization of multiple bacteria in water treatment

Bacteria, especially antibiotic-resistant bacteria, in water threaten public health in countries. Simultaneous flocculation, sterilization and identification of bacteria are great challenge in water treatment. Herein we presented a three-in-one compound through combining a novel Bacitracin-based flocculant (B-g-PAMDAC) and surface enhanced Raman scattering (SERS) labels, the modified Au@AgNPs using graphene oxide (GO) and 4-mercaptophenylboronic acid (4-MPBA). B-g-PAMDAC with bactericidal groups and microblock structure was synthesized via copolymerization and self-assembly. Its functional groups and microblock structure contributed to the excellent performance in flocculation of bacteria. 4-MPBA as bacterial capture bound to the bacterial cell membrane and contributed to recognition of bacteria in flocculation. Bacteria aggregating around Au@AgNPs resulted in abundant “hot spots” and strong Raman signals. SERS labels obviously improved the sensitivity, accuracy and stability of bacteria identification even at low bacterial concentration of 1 × 103 CFU mL−1. They presented distinct fingerprints of bacteria, Escherichia coli, Pseudomonas aeruginosa, Bacillus cereus and Enterococcus faecalis, in Raman mappings. Bacitracin improved sterilization efficiency of B-g-PAMDAC in four bacteria treatment in terms of sterilization rate and time. β-galactosidase and respiratory activity of bacteria revealed sterilization mechanism of B-g-PAMDAC that changed permeability of cell membrane before it reduced the respiration activity of bacteria and ruptured cell wall.

Improving the sensitivity of immunoassay based on MBA-embedded Au@SiO2 nanoparticles and surface enhanced Raman spectroscopy

Traditional “sandwich” structure immunoassay is mainly based on the self-assembly of “antibody on solid substrate-antigen-antibody with nanotags” architectures, and the sensitivity of this strategy is critically depended on the surface enhanced Raman scattering (SERS) activities and stability of nanotags. Therefore, the rational design and fabrication on the SERS nanotags attracts the common interests to the bio-related detecting and imaging. Herein, silica encapsulated Au with mercaptobenzoic acid (MBA) core-shell nanoparticles (Au-MBA@SiO2) are fabricated instead of the traditional naked Au or Ag nanoparticles for the SERS-based immunoassay on human and mouse IgG antigens. The MBA molecules facilitate the formation of continuous pinhole-free silica shell and are also used as SERS labels. The silica shell is employed to protect MBA labels and to isolate Au core from the ambient solution for blocking the aggregation. This shell also played the similar role to BSA in inhibiting the nonspecific bindings, which allowed the procedures for constructing “sandwich” structures to be simplified. All of these merits of the Au-MBA@SiO2 brought the high performance in the related immunoassay. Benefiting from the introduction of silica shell to encapsulate MBA labels, the detection sensitivity was improved by about 1–2 orders of magnitude by comparing with the traditional approach based on naked Au-MBA nanoparticles. This kind of label-embedded core-shell nanoparticles could be developed as the versatile nanotags for the bioanalysis and bioimaging.

Surface-Enhanced Raman Scattering Dye-Labeled Au Nanoparticles for Triplexed Detection of Leukemia and Lymphoma Cells and SERS Flow Cytometry

The labeling of cell surface receptors by fluorescent markers is an established method for the identification of cell phenotype in both research and clinical settings. Fluorescence dye labeling has inherent constraints, most notably the upper limit of labels per cell that may be probed using a single excitation source, in addition to a physical limit to the number of broad emission spectra that can be distinctly collected within the visible wavelength region. SERS labeling has the potential to mitigate these shortfalls. Herein, antibody-targeted, PEG-coated surface-enhanced Raman scattering (SERS) Au nanoparticles are used simultaneously to label three cell surface markers of interest on malignant B cells from the LY10 lymphoma cell line. The SERS probes were characterized by multiple methods to confirm their monodispersity and functionalization with both PEG and monoclonal antibodies. The specificity of the particles' cell labeling was demonstrated on both primary chronic lymphocytic leukemia and LY10 cells using SERS from cell suspensions and confocal Raman mapping, respectively. Fluorescence flow cytometry was employed to confirm the binding of SERS probes to LY10 over large cell populations, and the particles' SERS was collected directly from labeled cells using a commercial flow cytometer. To the best of our knowledge, this is the first demonstration of SERS flow cytometry from cells tagged with targeted SERS probes.

Medical applications of surface-enhanced Raman scattering

This perspective article provides an overview of selected medical applications of surface-enhanced Raman scattering (SERS), highlighting recent developments and trends. The use of SERS for detection, analysis and imaging has attracted great interest in the past decade owing to its high sensitivity and molecular fingerprint specificity. SERS can deliver chemical and structural information from analytes rapidly and nondestructively in a label-free manner. Alternatively, SERS labels or nanotags, when conjugated to target-specific ligands, can be employed for the selective detection and localization of the corresponding target molecule. Biomedical applications based on both approaches are highlighted.

Synthesis of Peptide Mediated Au Core–Ag Shell Nanoparticles as Surface-Enhanced Raman Scattering Labels

As the fundamental understanding of metal-light interactions gains solid grounds, further research has been devoted to construct novel structures that take full advan- tage of such unique interactions, which is called plas- monics. In this report, the preparation of Au-Ag core-shell structures obtained by coating the Au surface with peptide and Raman reporter molecule and depositing an Ag layer on it is reported. The prepared Au-Ag NPs are tested for their surface-enhanced Raman scattering (SERS) perfor- mance. The negatively charged peptides with three different lengths, which are 3 (P1), 15 (P2), and 21 (P3) amino acid long, were chemically attached to 13 nm AuNPs along with Raman reporter molecule, carboxytetramethylrhodamine, and these modified AuNPs were coated with three different shell thickness of Ag metal. The prepared Au-Ag NPs were tested for their SERS performance and found that the Au- Ag NPs prepared with P2 and thickest shell performs best as SERS label.

Competitive surface-enhanced Raman scattering assay for the 1,25-dihydroxy metabolite of vitamin D3

This paper describes the development and preliminary testing of a competitive surface-enhanced Raman scattering (SERS) immunoassay for calcitriol, the 1,25-dihydroxy metabolite (1,25-(OH)(2)-D(3)) of vitamin D(3). Deficiencies in 1,25-(OH)(2)-D have been linked to renal disease, while elevations are linked to hypercalcemia. Thus, there has been a sharp increase in the clinical demand for measurements of this metabolite. The work herein extends the many attributes of SERS-based sandwich immunoassays that have been exploited extensively in the detection of large biolytes (e.g., DNA, proteins, viruses, and microorganisms) into a competitive immunoassay for the low level determination of a small biolyte, 1,25-(OH)(2)-D(3) (M(w) = 416 g mol(-1)). The assay uses surface modified gold nanoparticles as SERS labels, and has a dynamic range of 10-200 pg mL(-1) and a limit of detection of 8.4 ± 1.8 pg mL(-1). These analytical performance metrics match those of tests for 1,25-(OH)(2)-D(3) that rely on radio- or enzyme-labels, while using a much smaller sample volume and eliminating the disposal of radioactive wastes. Moreover, the SERS-based data from pooled-patient sera show strong agreement with that from radioimmunoassays. The merits and potential utility of this new assay are briefly discussed.

Multiplexing with SERS labels using mixed SAMs of Raman reporter molecules

Surface-enhanced Raman scattering (SERS) offers a tremendous multiplexing capacity for the selective detection of biomolecules in targeted research. SERS labels comprising self-assembled monolayers (SAMs) of Raman reporter molecules on the surface of metal nanoparticles are sensitive and robust probes. Advantages of a SAM include maximum sensitivity, minimal unwanted co-adsorption of molecules from the surroundings, and reproducible SERS spectra with only few dominant Raman bands--all of these independent of a particular SERS substrate. We demonstrate experimentally how to increase the multiplexing capacity of SERS labels by using mixed SAMs with up to three different Raman reporter molecules on the surface of the metal colloid. Type and stoichiometry of a particular Raman label in a multi-component SAM are additional parameters compared with one-component SAMs. All one-, two-, and three-component SAMs on gold nanospheres can be easily discriminated, either by their original SERS spectra or the corresponding bar codes.