Surface-enhanced Raman Scattering Assay Research Articles

Construction of selectively enhanced MOF-SERS sensor and highly sensitive detection of hCE1 in HepG2 cells

In this paper, a surface-enhanced Raman scattering (SERS) magnetic immunosensor for human carboxylesterase 1 (hCE1) assay was developed using a sandwich structure consisting of a magnetic support substrate, a SERS tag, and a target. The objective was to investigate the correlation between changes in hCE1 levels and liver injury. The utilization of Co-MOF-74@Au@methylene blue (MB) magnetic support substrate facilitated the expedient separation of biological samples while uniformly distributing the AuNPs, thereby enhancing the SERS intensity and improving the reproducibility. The introduction of Co-MOF-74 metal–organic frameworks (MOFs), endowed with its own selective SERS-enhancing properties, into the Co-MOF-74@Au@MB SERS tag further enhances the SERS sensing capability. The proposed SERS sensor exhibited good linearity over the concentration range of hCE1 from 10−2 to 102 μg·mL−1, with a correlation coefficient (R2) of 0.990 and a limit of detection (LOD) of 8.3 ng·mL−1. This demonstrates the potential of this strategy for the detection of trace proteins or enzymes in complex biological samples. In the meantime, the selective SERS enhancement mechanism of MOFs on Raman reporter molecules was preliminarily explored. This provides a new idea for the development of SERS substrates and SERS assays.

Hydrophilic-hydrophobic polymer strip with intrinsic signal and chemical-electromagnetic synergistic enhancement for non-metallic SERS-based identification of SARS-CoV-2 antigen

The formulation of substrates with reliable quantitative detection and robust molecular anchoring is crucial for surface-enhanced Raman scattering (SERS) technique. In this context, an appealing hydrophilic-hydrophobic polymer strip with Raman internal standard (IS) was generated by in-situ growing hydrophilic non-metallic black phosphorus/metal-organic frameworks (BP/ZIF-67) onto special regions of hydrophobic polydimethylsiloxane (PDMS) matrix, which dramatically promoted the concentration of target molecules. Furthermore, a specific detection of coronavirus disease 2019 (SARS-CoV-2) N-protein with a limit of 6.4 × 10−6 mg/mL was facilitated, benefiting from the selective capture rendered by the mesoporous surface of ZIF-67 and the ultra-high enhancement effect arose from BP/ZIF-67 hybrid structure-triggered charge transfer resonance process. Moreover, the extent of quantification in the SERS assay was significantly remedied due to the IS strategy. Especially, the slight local surface plasmon resonance (LSPR) capability of BP could readily provoke additional electromagnetic field to complement its powerful chemical enhancement, which was significantly superior to other non-metallic substrates. Such an upgraded platform may deliver another prospering technology for dependable virus monitoring.

Design, Rationalization, and Automation of a Catalytic Sensing Mechanism for Homogeneous SERS Biosensors

The current pandemic has shown that we need sensitive and deployable diagnostic technologies. Surface-enhanced Raman scattering (SERS) sensors can be an ideal solution for developing such advanced point-of-need (PON) diagnostic tests. Homogeneous (reagentless) SERS sensors work by directly responding to the target without any processing step, making them capable for simple one-pot assays, but their limitation is the achievable sensitivity, insufficient compared to what is needed for sensing of viral biomarkers. Noncovalent DNA catalysis mechanisms have been recently exploited for catalytic amplification in SERS assays. These advances used catalytic hairpin assembly (CHA) and other DNA self-assembly processes to develop sensing mechanisms with improved sensitivities. However, these mechanisms have not been used in OFF-to-ON homogeneous sensors, and they often target the same biomarker, likely due to the complexity of the mechanism design. There is still a strong need for a catalytic SERS sensor with a homogeneous mechanism and a rationalization of the catalytic sensing mechanism to translate this sensing strategy to different targets and applications. We developed and investigated a homogeneous SERS sensing mechanism that uses catalytic amplification based on DNA self-assembly. We systematically investigated the role of three domains in the fuel strand (internal loop, stem, and toehold), which drives the catalytic mechanism. The thermodynamic parameters determined in our studies were used to build an algorithm for automated design of catalytic sensors that we validated on target sequences associated with malaria and SARS-CoV-2 strains. With our mechanism, we were able to achieve an amplification level of 20-fold for conventional DNA and of 36-fold using locked nucleic acids (LNAs), with corresponding improvements observed in the sensor limit of detection (LOD). We also show a single-base sequence specificity for a sensor targeting a sequence associated with the omicron variant, tested against a delta variant target. This work on catalytic amplification of homogeneous SERS sensors has the potential to enable the use of this sensing modality in new applications, such as infectious disease surveillance, by improving the LOD while conserving the sensor's homogeneous character.

Vertically aligned Ag-decorated MoS2 nanosheets supported on polyvinyl alcohol flexible substrate enable high-sensitivity and self-cleaning SERS devices

The fabrication of stable and reproducible surface-enhanced Raman scattering (SERS) active substrates is a prerequisite for the ultra-sensitive SERS detection and sensing, but remains a great challenge. Herein, we present a facile yet efficient strategy for creating a flexible hybrid substrate by assembling Ag nanoparticles on vertical MoS2 nanosheets followed by spin-coating with polyvinyl alcohol (PVA) hydrogels. Combining the advantages of noble metal, 2D nanosheet, and hydrogel, the as-prepared SERS substrates exhibit superior detection ability and stability. Taking Rhodamine 6 G as a probing molecule, the lowest detectable concentration can be down to 1.0 × 10−12 M, and an enhancement factor is estimated to the order of 107. The finite-difference time-domain simulations reveal that the hybrid substrates provide strong electromagnetic enhancement and can generate more SERS “hot spots”, therefore effectively amplify the Raman signal. Furthermore, the developed flexible MoS2 @Ag-PVA hybrid not only has a great SERS effect, but it also has outstanding catalytic characteristics due to its remarkable self-cleaning ability when exposed to visible light. Specifically, the formation of MoS2 nanosheets by chemical vapor deposition is remarkably homogenous, resulting in long-term stability and repeatability of the substrates. Additionally, the PVA coverage guarantees the flexibility and stability of the substrate, overcoming the complex handling in SERS assays. Such features make the present SERS platform to be reused for a minimum of five cycles with tolerable intensity degradation. This flexible and self-cleaning SERS technique offers a great potential for high-sensitivity detection of organic contaminants and could develop an in-situ SERS sensing platform.

Rapid magnetic separation: An immunoassay platform for the SERS-based detection of subarachnoid hemorrhage biomarkers.

The blood-brain barrier (BBB) is of vital importance to the progression and prognosis of subarachnoid hemorrhage (SAH). The construction of a simple, sensitive, and accurate detection assay for measuring the biomarkers associated with BBB injury is still an urgent need owing to the complex pathogenesis of SAH and low expression levels of pathological molecules. Herein, we introduced surface-enhanced Raman scattering (SERS) label-embedded Fe3O4@Au core-shell nanoparticles as ideal SERS sensors for quantitative double detection of MMP-9 and occludin in SAH patients. Meanwhile, utilizing the SERS signals to dynamically estimate MMP-9 and occludin concentration in the rat SAH model is the first application in exploring the relationship of pathological MMP-9 and occludin molecular levels with neurobehavioral score. This method warrants reliable detection toward MMP-9 and occludin with a wide recognition range and a low detection limit in blood samples. Furthermore, the results monitored by the SERS assay exactly matched with those obtained through a traditional enzyme-linked immunosorbent assay (ELISA). The aforementioned results demonstrated this novel biosensor strategy has extensive application prospects in the quantitative measurement of multiple types of biomolecules in body fluid samples.

SERS Multiplex Profiling of Melanoma Circulating Tumor Cells for Predicting the Response to Immune Checkpoint Blockade Therapy.

Immune checkpoint blockade (ICB) therapy has achieved remarkable success in many cancers including melanoma. However, ICB therapy benefits only a small proportion of patients and produces severe side effects for some patients. Thus, there is an urgent need to identify patients who are more likely to respond to ICB therapy to improve outcomes and minimize side effects. To predict ICB therapy responses, we design a surface-enhanced Raman scattering (SERS) assay for multiplex profiling of circulating tumor cells (CTCs) under basal and interferon-γ (IFN-γ) stimulation. Through simultaneous ensemble and single-cell measurements of CTCs, the SERS assay can reveal tumor heterogeneity and offer a comprehensive CTC phenotype for decision-making. Anisotropic gold-silver alloy nanoboxes are utilized as SERS plasmonic substrates for improved signal readouts of CTC surface biomarkers. By generating a unique CTC signature with four surface biomarkers, the developed assay enables the differentiation of CTCs from three different patient-derived melanoma cell lines. Significantly, in a cohort of 14 melanoma patients who received programmed cell death-1 blockade therapy, the changes of CTC signature induced by IFN-γ stimulation to CTCs show the potential to predict responders. We expect that the SERS assay can help select patients for receiving ICB therapy in other cancers.

A comparative study based on serum SERS spectra in and on the coffee ring for high precision breast cancer detection

AbstractHuman blood contains a variety of biomolecules that are highly related to the occurrence, progression, and prognosis of diseases, including cancer. The development of rapid and accurate methods for the detection of these biomarkers with extremely low concentration is vital for improving cancer screening. Herein, a label‐free surface‐enhanced Raman scattering (SERS) technology was employed to detect human serum samples from healthy volunteers (n = 51) and breast cancer patients (n = 58) with the aim of exploring the differences in bio‐components between them. Moreover, the influence of measurement location during SERS assay was evaluated due to the occurrence of “coffee‐ring (CR)” effect associated with this work. Results showed that the SERS spectra obtained from the CR area can better reflect the overall biochemical information of serum samples and exhibited excellent diagnostic sensitivity (94.8%) and specificity (98%) for identifying breast cancer from healthy groups using principal component analysis and linear discriminant analysis (PCA‐LDA) algorithm. This work showed a preliminary study of the serum SERS method for breast cancer detection, providing a potential rapid and accurate liquid biopsy strategy for clinical cancer screening.

ZnO Tips Dotted with Au Nanoparticles-Advanced SERS Determination of Trace Nicotine.

Long-term exposure to nicotine causes a variety of human diseases, such as lung damage/adenocarcinoma, nausea and vomiting, headache, incontinence and heart failure. In this work, as a surface-enhanced Raman scattering (SERS) substrate, zinc oxide (ZnO) tips decorated with gold nanoparticles (AuNPs) are fabricated and designated as ZnO/Au. Taking advantage of the synergistic effect of a ZnO semiconductor with morphology of tips and AuNPs, the ZnO/Au-based SERS assay for nicotine demonstrates high sensitivity and the limit of detection 8.9 × 10−12 mol/L is reached, as well as the corresponding linear dynamic detection range of 10−10–10−6 mol/L. Additionally, the signal reproducibility offered by the SERS substrate could realize the reliable determination of trace nicotine in saliva.

Capture of Phenylalanine and Phenylalanine-Terminated Peptides Using a Supramolecular Macrocycle for Surface-Enhanced Raman Scattering Detection.

The cucurbit[n]uril (CB[n]) family of macrocycles are known to bind a variety of small molecules with high affinity. These motifs thus have promise in an ever-growing list of trace detection methods. Surface-enhanced Raman scattering (SERS) detection schemes employing CB[n] motifs exhibit increased sensitivity due to selective concentration of the analyte at the nanoparticle surface, coupled with the ability of CB[n] to facilitate the formation of well-defined electromagnetic hot spots. Herein, we report a CB[7] SERS assay for quantification of phenylalanine (Phe) and further demonstrate its utility for detecting peptides with an N-terminal Phe. The CB[7]-guest interaction improves the sensitivity 5-25-fold over direct detection of Phe using citrate-capped silver nanoparticle aggregates, enabling use of a portable Raman system. We further illustrate detection of insulin via binding of CB[7] to the N-terminal Phe residue on its B-chain, suggesting a general strategy for detecting Phe-terminated peptides of clinically relevant biomolecules.

Fabrication of superhydrophobic Ag@ZnO@Bi2WO6 membrane disc as flexible and photocatalytic active reusable SERS substrate

Nowadays, there is a great influence of the innovated semiconductor heterojunction on the improvement of photocatalysis in organic pollutants elimination and the Raman signals multiplexing towards quantitative determination. Here, it was an attempt to develop a heterostructure membrane-based platform employing a filtration system to degrade and detect various target molecules at trace level in liquid samples. Herein, the ZnO nanorods/Bi2WO6 nanocomposites (ZBW) were prepared by a moderate temperature hydrothermal method; thereafter ZBW was encrusted with in-situ photoreduced silver nanoparticles (AgNPs) to form AgNPs@ZBW (Ag@ZnO@Bi2WO6) platform. The superhydrophobic AgNPs@ZBW platform encompasses both photocatalytic degradation of rhodamine B (RhB) under UV-irradiation and label-free surface-enhanced Raman scattering (SERS) evaluated for rhodamine 6G (R6G) and RhB. The AgNPs@ZBW exhibited superior photocatalytic and SERS activities for organic dyes degradation. As a result, the photocatalytic efficiency for dyes was 97.95% in 140 min. From the recycling experiment, it was manifested that AgNPs@ZBW maintained superb photocatalytic activity and stability after five cycles of use for SERS analysis. As-prepared platform displayed a scalable SERS response from 100 µM to 1 nM and enhancement factor of 3.2 × 105 and 1.2 × 105 for R6G and RhB, respectively, using an excitation wavelength of 532 nm, laser power of 3.2 mW and time of exposure of 10 s. Displayed trending of superhydrophobic membrane-based SERS substrates is assumed to lead abounds of change in the field of photocatalytic materials, SERS assay, and organic chemical analysis.

Rapid simultaneous adsorption and SERS detection of acid orange II using versatile gold nanoparticles decorated NH2-MIL-101(Cr)

Acid orange II (AO II), a typical azo pigment, is strictly controlled by legislation and prohibited in foodstuffs. Herein, we prepared gold nanoparticles decorated amino-functionalized Cr-based metal-organic frameworks [NH2-MIL-101(Cr)@Au] via an in-situ reduction method as a surface-enhanced Raman scattering (SERS) substrate for simultaneous adsorption and detection of AO II. Gold nanoparticles are uniformly dispersed on the surface of NH2-MIL-101(Cr) owing to its three-dimensional (3D) structure and the interaction between –NH2 and Au ions, providing more SERS-active “hot spots”. These NH2-MIL-101(Cr)@Au nanocomposites exhibited selective and high adsorption performance (419.85 mg g−1) for AO II, and could be used as superior SERS substrates for the detection of AO II with a low limit of detection (LOD) of 0.05 mg L−1 and wide detection range of 0.05–50 mg L−1 using portable Raman spectrometer. Furthermore, this SERS assay has been successfully used to determine AO II in orange juice and chili powder with good sensitivities.

Highly sensitive detection of tryptophan (Trp) in serum based on diazo-reaction coupling with Surface-Enhanced Raman Scattering and colorimetric assay

Tryptophan plays an important role in the metabolic pathway and tryptophan metabolism is abnormal in tumor tissues. Therefore, Trp and its metabolites in body fluids can be used as tumor markers for cancer monitoring. However, the traditional tryptophan detection method has many shortcomings, such as low sensitivity, time-consuming and so on, which is difficult to meet the clinical needs. Herein, a rapidly, sensitive and reliable method for indirectly detecting Tryptophan (Trp) in serum was proposed by combining diazo-coupling reaction mechanism with surface-enhanced Raman scattering (SERS). The limit of detection (LOD) of Trp can be as low as 20 nM, which is much lower than existing detection methods. In addition, because of obvious change in color in diazo-coupling reaction, a colorimetric detection was applied for convenient determination of Trp in the concentration ranged from 3 × 10−5 - 10−3 M. Furthermore, with the support of good results by SERS assay, the presented method was successfully carried out for the determination of Trp in serum that came from healthy people and colorectal cancer patients. Comparing the difference of Trp content in serum between the two groups, it was found that tryptophan metabolism disorder exists in colorectal cancer patients, which suggested that the accurate detection of tryptophan content may provide important reference for the pathogenesis, prediction and prevention of colorectal cancer.

SAT-144 AN ULTRASENSITIVE SURFACE ENHANCED RAMAN SCATTERING (SERS)-BASED ASSAY FOR KIDNEY INJURY MOLECULE-1 (KIM-1)

Kidney injury molecule-1 (KIM-1) is a biomarker of acute and chronic kidney injury. However, dilution of urine samples to minimize the impact of pH and solute on results can push the concentration levels to below the lower limits detection of conventional ELISAs. Additionally, small samples from infants, children or from non-human renal injury models such as mice limits analyte detection. Here we develop an ultrasensitive (sub-pg/ml) assay utilizing surface enhanced Raman scattering (SERS) to measure KIM-1. Capture and detection antibodies of a commercially available KIM-1 ELISA kit (R&D Systems) were utilized. [email protected] nanocuboids ([email protected]) with 16 nm shell thickness, assembled on silicon wafers, were derivatized with cysteamine followed by glutaraldehyde to covalently attach the capture antibody. Separately, [email protected] were derivatized with the Raman reporter 4-aminothiophenol (pATP), glutaraldehyde followed by the detection antibody. After analyte capture on the silicon wafer, washing, incubating with the derivatized detection antibody and washing, the silicon wafers were subject to SERS. Among several prominent Raman bands, the intensity band at 1080 cm-1 of pATP was proportional to the concentration of human recombinant KIM-1 spiked into artificial urine. The urine of control individuals and patients with kidney disease was diluted prior to assay and the results compared to that using the conventional ELISA. The Raman intensity band at 1080 cm-1 of pATP was proportional to the KIM-1 concentration from to 400 pg/ml. As little as 1fg/ml above background could be reliably detected. The KIM-1 concentration, determined in patient urine using both the conventional ELISA and the SERS assay, was found to be synonymous with a correlation coefficient of 0.93 ( p<0.002). A similar strategy was used to develop a sub-pg/ml assay for the pro-inflammatory/myokine molecule IL-6. Using the power of SERS, capture and detection antibodies of a conventional ELISA kit were modified to measure sub-pg/ml amounts of KIM-1. This sensitivity allows dilution of samples to eliminate the influence of pH and/or solute concentration that would otherwise affect conventional ELISA results. Also the sensitivity of the assay allows the use of small samples of urine or plasma from infants, small children or from small animals such as mice with experimental renal diseases. It would be possible to detect preclinical changes in KIM-1 prior to disease manifestation. This assay strategy can be adapted to multiplexing to measure two or more analytes simultaneously in one sample by utilizing different Raman reporter molecules on different detection antibodies, an appropriate mix of capture antibodies on the silicon wafer, and monitoring non-overlapping Raman bands specific for each reporter.

Quantitative and specific detection of cancer-related microRNAs in living cells using surface-enhanced Raman scattering imaging based on hairpin DNA-functionalized gold nanocages.

Variations in the intracellular expression level of cancer-related microRNAs (miRNAs) are connected with worsening tumor progression. A simple, accurate, and sensitive analytical method for the imaging and detection of intracellular miRNA is still a great challenge due to the low abundance of miRNAs and the complexity of intracellular environments. In this work, target miRNA (miRNA)-mediated catalytic hairpin assembly (CHA)-induced gold nanocage (GNC)-hairpin DNA1 (hpDNA1)-hpDNA2-GNC nanostructures were designed for surface-enhanced Raman scattering (SERS) detection and imaging of the specific miR-125a-5p in the normal lung epithelial cell line (BEAS-2B cells) and lung cancer cell line (A549 cells). The finite difference time domain (FDTD) simulations showed that the polymer of GNCs possessed a much stronger electromagnetic field in nanogaps than that of single GNC, theoretically confirming the rational design of the CHA assembly strategy. Using this method, miR-125a-5p can be detected in a wide linear range with a detection limit of 43.96 aM and high selectivity over other miRNAs in vitro. Moreover, SERS imaging successfully detected and distinguished the expression levels of intracellular miR-125a-5p in BEAS-2B cells and A549 cells. The results obtained by the SERS assay were consistent with those obtained by the real-time quantitative polymerase chain reaction (qRT-PCR). This method can offer a powerful strategy for the imaging and quantitative detection of various types of biomolecules in vitro as well as in living cells.

AuNS@Ag core-shell nanocubes grafted with rhodamine for concurrent metal-enhanced fluorescence and surfaced enhanced Raman determination of mercury ions

Mercury ion (Hg2+) is a highly hazardous and widespread pollutant with bio-accumulative properties. Although the existing Hg2+ detection methods have high sensitivity and reliability, whereas there have few reports concerning bimodal detection for Hg2+ with one sensor. Toward this goal, a novel sensor based on rhodamine derivatives (RhD) grafted AuNS@Ag core-shell nanocubes (CSN) has been synthesized and shown the bimodal detection capabilities with metal enhanced fluorescence (MEF) and surface enhanced Raman scattering (SERS) for Hg2+. Herein, resultant CSN acts as the signal enhancing material; RhD was modified on the outside of the shell to ensure the signal sensitive of the CSN-RhD hybrids. In this work, we investigate the size- and shape-dependent SERS activity of plasmonic CSN comprised of AuNS as cores and Ag cuboids as shells. The SERS activity of CSN with spherical core was found to increase with the increasing thickness of the Ag cubic shell. Sequel, under an optimized condition, a display of strong MEF and SERS signals of the resulting mixtures with increasing of Hg2+ concentrations was observed. The proposed bimodal sensor showed excellent performances for Hg2+ along with wide linear range of 0.001–1000 ppm and 0.01–1000 ppm as well as the relatively low detection limit of 0.94 and 5.16 ppb for MEF and SERS assays, respectively. Furthermore, the ability of the sensor to detect Hg2+was also confirmed in adulterated milk samples.

Live-Cell Pyrophosphate Imaging by in Situ Hot-Spot Generation.

Controlling the electromagnetic hot-spot generation is essential for surface-enhanced Raman scattering (SERS) assays. Current hot-spot-based SERS assays have been extensively studied in solutions or on substrates. However, probing biospecies by controlling the hot-spot assembly in living systems has not been demonstrated thus far. Herein, we report a background-free SERS probe for imaging pyrophosphate (PPi), a biochemically significant anion, in living cells. Intracellular PPi is able to induce the nanoparticle dimerization, thus creating an intense electromagnetic hot spot and dramatically enhancing the signal of the Raman reporters residing in the hot spot. More impressively, the reporter we used in this study provides a strong and sharp single peak in the cellular Raman-silent region (1800-2800 cm-1), thus eliminating the possible background interference. This strategy could be readily extended to detect other biomarkers by only replacing the recognition ligands.

Ultrasensitive SERS detection of Bacillus thuringiensis special gene based on Au@Ag NRs and magnetic beads

Highly sensitive and selective detection of specific DNA sequences is of great importance in clinical diagnosis, environmental and food monitoring, but it still remains challenges to develop a facile method for real sample detection in aqueous solution. Here, a simple and recyclable surface enhanced Raman scattering (SERS) sensor was constructed for Bacillus thuringiensis (Bt) special gene fragment detection by Fe3O4 magnetic beads (MBs) and Au-Ag core-shell nanorods (Au@Ag NRs). A hairpin DNA with sulfhydryl and biotin was attached to Au@Ag NRs as indicator, and MBs with streptavidin (SA) were acted as the capture probe. On the basis of the biotin-SA specific interaction, target sequences were first hybridized with the hairpin DNA and exposed the biotin. Subsequently, the Au@Ag NRs were captured by the streptavidin modified MBs, which reduced the suspended NRs and led to the change of Raman intensity. Under the optimal conditions, the SERS intensity revealed a good linearity with Bt transgene fragment ranging from 0.1pM to 1nM with a detection limit of 0.14pM (S/N=3). To demonstrate the specificity of the strategy, the single-base mismatch in DNA was discussed in the SERS assay. The results showed that the sensitivity and accuracy of the proposed method was acceptable in DNA detection, revealing a great potential in special gene detection.

Novel surface-enhanced Raman scattering-based assays for ultra-sensitive detection of human pluripotent stem cells.

Human pluripotent stem cells (hPSCs) are a promising cell source for regenerative medicine, but their derivatives need to be rigorously evaluated for residual stem cells to prevent teratoma formation. Here, we report the development of novel surface-enhanced Raman scattering (SERS)-based assays that can detect trace numbers of undifferentiated hPSCs in mixed cell populations in a highly specific, ultra-sensitive, and time-efficient manner. By targeting stem cell surface markers SSEA-5 and TRA-1-60 individually or simultaneously, these SERS assays were able to identify as few as 1 stem cell in 10(6)cells, a sensitivity (0.0001%) which was ∼2000 to 15,000-fold higher than that of flow cytometry assays. Using the SERS assay, we demonstrate that the aggregation of hPSC-based cardiomyocyte differentiation cultures into 3D spheres significantly reduced SSEA-5(+) and TRA-1-60(+) cells compared with parallel 2D cultures. Thus, SERS may provide a powerful new technology for quality control of hPSC-derived products for preclinical and clinical applications.

Detection of Hepatitis B virus antigen from human blood: SERS immunoassay in a microfluidic system

A highly sensitive immunoassay utilizing surface-enhanced Raman scattering (SERS) has been developed with a new Raman reporter and a unique SERS-active substrate incorporated into a microfluidic device. An appropriately designed Raman reporter, basic fuchsin (FC), gives strong SERS enhancement and has the ability to bind both the antibody and gold nanostructures. The fuchsin-labeled immuno-Au nanoflowers can form a sandwich structure with the antigen and the antibody immobilized on the SERS-active substrate based on Au–Ag coated GaN. Our experimental results indicate that this SERS-active substrate with its strong surface-enhancement factor, high stability and reproducibility plays a crucial role in improving the efficiency of SERS immunoassay. This SERS assay was applied to the detection of Hepatitis B virus antigen (HBsAg) in human blood plasma. A calibration curve was obtained by plotting the intensity of SERS signal of FC band at 1178cm−1 versus the concentration of antigen. The low detection limit for Hepatitis B virus antigen was estimated to be 0.01IU/mL. The average relative standard deviation (RSD) of this method is less than 10%. This SERS immunoassay gives exact results over a broad linear range, reflecting clinically relevant HBsAg concentrations. It also exhibits high biological specificity for the detection of Hepatitis B virus antigen

Target triggered self-assembly of Au nanoparticles for amplified detection of Bacillus thuringiensis transgenic sequence using SERS

The research methods for DNA detection have been widely extended since the application of nanotechnology, but it remains a challenge to detect specific DNA sequences or low abundance genes in the biological samples with accuracy and sensitivity. Here we developed a SERS biosensing platform by target DNA (tDNA) triggered self-assembly of Au nanoparticles (Au NPs) probes on DNA nanowires for signal amplification in DNA analysis. Based on the hybridization chain reactions (HCR) and surface enhanced Raman scattering (SERS) technology, the SERS intensity reveals a good linearity with tDNA ranging from 50pM to 500pM under optimal conditions. The specific detection of tDNA sequence was realized with a detection limit of 50pM (S/N=3). To demonstrate the specificity and universality of the strategy, the single-base mismatches in DNA and the Bacillus thuringiensis (Bt) transgenic sequence were successively applied in the SERS assay. The results showed that the sensitivity and accuracy of the SERS-based assay were comparable with real-time PCR. Besides, the method would provide precise and ultra-sensitive detection of tDNA but also informative supplement to the SERS biosensing platform.