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Ultrasensitive and simultaneous detection of two cytokines secreted by single cell in microfluidic droplets via magnetic-field amplified SERS
摘要： A surface-enhanced Raman scattering (SERS)-microfluidic droplet platform for the rapid, ultrasensitive and simultaneous detection of vascular endothelial growth factor (VEGF) and interleukin-8 (IL-8) secreted by a single cell is presented. The high throughput water-in-oil droplets containing individual cell along with four kinds of immune-particles (antibody-conjugated silver nanoparticles or magnetic beads, AgNPs@Ab1 and MNs@Ab2) in each were achieved by a cross-typed microfluidic chip, and then they were captured by a collection channel array for SERS measurements. In the appearance of cytokines secreted by one cell, AgNPs@Ab1 can be linked onto the surface of MNs@Ab2 through the immune-recognition to form an immune-sandwich, which makes the 'turn on' SERS signal of the Raman reporters previously laid on the surface of MNs due to the adjacent AgNPs. Furthermore, the second SERS signal amplification is from the magnetic field-induced spontaneous collection effect, which brings 75 times enhancement for SERS signal. Additionally, the encapsulation of cytokines in an isolated droplet permits an accumulation effect of targets with time. Owing to the dual signal enhancement and the accumulation effect, such few cytokines secreted by single cell become detectable and a limit of detection is achieved as 1.0 fg/mL in one droplet. By using this ultrasensitive SERS-microdroplet method, the VEGF and IL-8 secretions from several cells in one droplet were explored and the data show that the cell–cell interactions may promote angiogenesis of cancer cells through the up-regulation of VEGF and IL-8.
关键词： surface-enhanced Raman scattering,VEGF,magnetic field amplification,single-cell analysis,IL-8,cytokines,microfluidic droplets
更新于2025-09-23 15:23:52
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Determination of Saxitoxin by Aptamer-Based Surface-Enhanced Raman Scattering
摘要： Saxitoxin is one of the most harmful paralytic shellfish toxins due to its high toxicity and adverse effects on the environment and human health. Aptasensors provide simple detection procedures because they have the advantages of chemical stability, easy synthesis and modification, and high convenience in signal transformation. Surface-enhanced Raman scattering (SERS) is an analytical technique that amplifies the analytical signals of molecules at extremely low concentrations, or even at the single molecule level, when the analyte is very close to rough metal surfaces or nanostructures. In this study, an SERS aptasensor is reported for the determination of saxitoxin for the first time. The optimized saxitoxin aptamer (M-30f) was modified on gold nanoparticles and served as the recognition element. Crystal violet was used as the Raman reporter without chemical bounding. The analytical principles of the aptasensor are that saxitoxin destabilized the conformations of the aptamer at high temperature conditions and altered the binding of crystal violet on the gold nanoparticles. In the presence of saxitoxin, the conformation of aptamer containing the G-quadruplex that selectively bound crystal violet unfolded to a large extent and hence the crystal violet molecules were released from gold nanoparticles with a reduced SERS signal. The effects of the gold nanoparticle size, the amount of DNA, aptamer density, sodium chloride concentration, and operation temperature upon the SERS determination were optimized. The resulting simple SERS aptasensor was developed with a satisfactory limit of detection (11.7 nM) and selectivity. The application for the analysis of real shellfish samples with simple procedures demonstrates that this SERS aptasensor is promising for on-site applications.
关键词： saxitoxin,paralytic shellfish toxin,surface-enhanced Raman scattering (SERS),Aptamer
更新于2025-09-23 15:23:52
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Hierarchical assembly of gold nanorods stripe patterns for sensing and cells alignment
摘要： Hierarchical assemblies of nano-material superstructure with controlled orientation affords a multitude of novel properties of plasmonics and broadly applications. Yet constructing multi-functional superstructures with positioning nanoparticles in desired locations remain challenges. Herein, gold nanorods (GNRs) assembled in stripe patterns with controlled orientation and structures in millimetre scale for versatile application are achieved. Applications of patterned GNRs in sensing enhancement and engineering mammalian cells alignment are investigated experimentally. The performance of patterned GNRs in surface enhanced Raman scattering (SERS) and electrical sensing are found in orientational dependence. The SERS signals of vertically arranged GNRs arrays exhibit double folder intensity than horizontally arranged. In contrast, the horizontally arranged GNRs exhibit twice high electrical conductivity. The system is further explored to pattern mammalian cells, for the first time, we reveal nanostructured topography of GNRs confine cells to specific region, direct the adhesion and extension of living cells, which open up a broad application in tissue engineering and biosensing.
关键词： Gold nanorods,Cell patterns,Surface enhanced Raman scattering,Controllable orientation
更新于2025-09-23 15:23:52
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Ultrasensitive detection of avian influenza A (H7N9) virus using surface-enhanced Raman scattering-based lateral flow immunoassay strips
摘要： The development of biosensors that are portable, low-cost, and quantitative has long been sought for rapid, on-site, and timely detection of avian influenza virus (AIV). In this study, an antibody-based Raman lateral flow immunoassay strip was developed to detect AIV H7N9. This LFIA strip used a novel core-shell structure material, AuAg4(cid:3)ATP@AgNPs, as a Raman probe. An antibody specific for AIV and goat anti-mouse IgG antibody were immobilized on a nitrocellulose membrane as the test and control lines, respectively. Accumulation of antibody-virus-antibody-Raman probe complex at the test line could be visualized by the naked eye, and the Raman signal could be quantified using a portable Raman instrument. The testing process for the SERS-based LFIA strips could be completed in 20 min, which avoided the time-cost of current methods for AIV analysis. In our SERS-based biosensor, we estimated the limit of detection (LOD) for H7N9 to be 0.0018 HAU. This value is approximately three orders of magnitude more sensitive than the corresponding HA assays. When testing real sample, the results of the strip test were in accordance with those from real-time PCR testing. In conclusion, the SERS-based LFIA strip proposed in this study shows tremendous potential to detect targets quickly and sensitively using an elegantly simple method.
关键词： AuAg4(cid:3)ATP@AgNPs,Surface-enhanced Raman scattering,Avian influenza virus,Lateral flow immunoassay strips
更新于2025-09-23 15:23:52
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Ordered Array of Metal Particles on Semishell Separated with Ultrathin Oxide: Fabrication and SERS Properties
摘要： Metal particles in gap cavities provide an interesting system to achieve hybrid local surface plasmon modes for local field enhancement. Here, we demonstrate a relatively simple method to fabricate Ag nanoparticles positioned on Ag semishells separated by a thin (~5 nm) dielectric layer. The obtained structure can provide strong local electric field enhancement for surface-enhanced Raman scattering (SERS). The fabrication of the ordered array structure was realized by nanosphere self-assembly, atomic layer deposition, and metal thin-film dewetting. Numerical simulation proved that, compared to the conventional metal semishell arrays, the additional Ag particles introduce extra hot spots particularly in the valley regions between adjacent Ag semishells. As a result, the SERS enhancement factor of the metal semishell-based plasmonic structure could be further improved by an order of magnitude. The developed novel plasmonic structure also shows good potential for application in plasmon-enhanced solar water-splitting devices.
关键词： particle in cavity,nanosphere lithography,surface-enhanced Raman scattering (SERS),surface plasmonic,monolayer self-assembly
更新于2025-09-23 15:22:29
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Growth of Spherical Gold Satellites on the Surface of Au@Ag@SiO <sub/>2</sub> Core–Shell Nanostructures Used for an Ultrasensitive SERS Immunoassay of Alpha-Fetoprotein
摘要： The identification and detection of cancer biomarkers in early stages is an important issue for the therapy of cancer. However, most methods are time-consuming, limited sensing sensitivity and specificity. In this work, we prepared a novel plasmonic multilayered core–shell-satellite nanostructure (Au@Ag@SiO2-AuNP) consisting of an gold nanosphere with silver coating core (Au@Ag), an ultrathin continuous silica (SiO2) shell and high coverage of gold nanospheres (AuNPs) satellites. Au@Ag core is prominent surface enhanced Raman scattering (SERS) platform and the thin SiO2 layer exhibits a long-range plasmon coupling between Au@Ag core to AuNPs satellites further leading to enhanced Raman scattering. Meanwhile, the outer AuNPs satellites have a high biocompatibility and long-term stability. Combining the above advantages, the well-designed metallic nanoassemblies would be a promising candidate for SERS-based applications in biochemistry. For specific detection of alpha-fetoprotein (AFP), we utilized the SERS-active core-shell-satellite nanostructures modified with AFP antibody as immune probes and nitrocellulose membrane (NC) stabilized captured anti-AFP antibodies as solid substrate. To improve the detection performance, we further systematically optimized the parameters, including silver coating thickness of Au@Ag core, the density and size of satellite AuNPs. Under the optimized conditions, AFP could be detected by the SERS-based sandwich immunoassay with an ultralow detection limit of 0.3 fg/mL, and the method exhibited a wide linear response from 1 fg/mL to 1 ng/mL. The limit of detection (LOD) was considerably lower than conventional methods in literature. This work relies on the unique Au@Ag@SiO2-AuNP nanostructures as immune probe develops a new outlook for the application of multilayered nanoassemblies and demonstrates the great potential in early tumor markers detection.
关键词： surface enhanced Raman scattering (SERS),Au-Ag bimetallic nanospheres,alpha-fetoprotein,core-shell-satellite nanostructure,gold nanospheres
更新于2025-09-23 15:22:29
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Octadecyltrichlorosilane Capped Au Nanodot Arrays as Hydrophobic Surface Enhanced Raman Scattering Substrate for Biomedical Applications
摘要： Plasmonic nanostructures provide as a highly active-SERS substrate that can potentially achieve biomolecules detection. However, the detection of highly diluted, small volume analyte detection remains an urgent problem, due to the diffuse over the hydrophilic surfaces, which far from the plasmonic sensitive areas and limits the SERS detection sensitivity. In this study, we describe the fabrication and characterization of octadecyltrichlorosilane (OTS) capped gold nanodot (Au ND) arrays, the combination of hydrophobic surfaces and nanoplasmonics, and demonstrates their suitability as hydrophobic SERS active substrate for biomedical application. The activity of OTS capped Au ND arrays as SERS substrate was experimentally verified using Rhodamine B as an analyte. This substrate showed 3-fold signal enhancement compared to the ordinary hydrophilic Au ND arrays due to the hydrophobic condensation effect. It is expected that the OTS capped Au ND arrays can be lead to development of a highly sensitive and selective tool for biomedical applications using SERS detection.
关键词： Gold Nanodot Arrays,Octadecyltrichlorosilane,Surface Enhanced Raman Scattering,Hydrophobic,Plasmonic Structure,Biomedical Application
更新于2025-09-23 15:22:29
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Surface-Enhanced Raman Scattering (SERS) With Silver Nano Substrates Synthesized by Microwave for Rapid Detection of Foodborne Pathogens
摘要： Rapid and sensitive methods have been developed to detect foodborne pathogens, a development that is important for food safety. The aim of this study is to explore Surface-enhanced Raman scattering (SERS) with silver nano substrates to detect and identify the following three foodborne pathogens: Escherichia coli O157: H7, Staphylococcus aureus and Salmonella. All the cells were resuspended with 10 mL silver colloidal nanoparticles, making a concentration of 107 CFU/mL, and were then exposed to 785 nm laser excitation. In this study, the results showed that all the bacteria can be sensitively and reproducibly detected directly by SERS. The distinctive differences can be observed in the SERS spectral data of the three food-borne pathogens, and the silver colloidal nanoparticles can be used as highly sensitive SERS-active substrates. In addition, the assay time required only a few minutes, which indicated that SERS coupled with the silver colloidal nanoparticles is a promising method for the detection and characterization of food-borne pathogens. At the same time, principle component analysis (PCA) and hierarchical cluster analysis (HCA) made the different bacterial strains clearly differentiated based on the barcode spectral data reduction. Therefore, the SERS methods hold great promise for the detection and identification of food-borne pathogens and even for applications in food safety.
关键词： silver nanoparticles,rapid detection,food safety,Surface-enhanced Raman scattering,foodborne pathogens,bioanalysis
更新于2025-09-23 15:22:29
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Simultaneous detection of different probe molecules using silver nanowires as SERS substrates
摘要： Metallic silver nanowires with high yield were synthesized using a modified seed mediated approach at room temperature. Ribbon-like nanostructures were obtained when the concentration of NaOH was lower and further increase of NaOH transformed it into long nanowires. These nanowires possess high aspect ratio, with length and diameter ~ 6.5 μm and 17 nm respectively. The surface enhanced Raman scattering activity of these nanowires was tested with three different probe molecules viz., crystal violet, malachite green and nile blue chloride using visible (514.4 nm) and near-infrared (784.8 nm) excitation lines. The minimum detection limits for crystal violet and nile blue chloride molecules were found to be down to 10-7 M with good linear responses, as evidenced by values of correlation coefficients, indicating their potential for a variety of applications such as sensing. Principal component analysis was performed with the surface enhanced Raman spectra in order to discriminate the dye molecules and their mixture, simultaneously. The first two principal components, which provided 69.80 and 27.93% of the total data variance, could be conveniently represented as a two dimensional PCA score plot. The score plot showed clear clustering of probe molecules and their mixture. The relative contribution of wavenumbers to each of the two principal components was identified by plotting the PCA loading matrix. These results further promote possibilities of quantification of multiplexed SERS detection and analysis.
关键词： Surface enhanced Raman Scattering,Loading Plot.,Principal component analysis,Score plot,Silver nanowires
更新于2025-09-23 15:22:29
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Ultrasensitive detection of diclofenac in water samples by a novel surface-enhanced Raman scattering (SERS)-based immunochromatographic assay using AgMBA@SiO2-Ab as immunoprobe
摘要： In the last years, surface-enhanced Raman scattering based immunochromatographic assay (SERS-ICA) has been getting great attention and been applied for the detection of different target analytes. In this study, a novel SERS-ICA using AgMBA@SiO2-Ab as an immunoprobe has been developed for rapid, quantitative and ultrasensitive detection of a pharmaceutical diclofenac (DCF) residue in water samples. Ag, Ag@SiO2 and AgMBA@SiO2 nanoparticles (NPs) were synthesized and characterized. The immunoprobe was prepared by sandwiching the Raman reporter mercaptobenzoic acid (MBA) between the core-shell layers and immobilizing the monoclonal antibody (mAb) against DCF on the surface of the Ag@SiO2 NPs. Under optimal conditions, the sensitivity and limit of detection (LOD) of the SERS-ICA for DCF were found to be 9 pg mL-1 and 0.07 pg mL-1, respectively. The detection of the SERS-ICA for DCF was completed within 15 min. AgMBA@SiO2-Ab was stable within four months without significant loss of SERS intensity. The key to success of the SERS-ICA was the employment of the Ag@SiO2 NPs as the SERS substrate, which possessed gorgeous SERS enhancement capability, predominant biocompatibility and excellent stability. This SERS-ICA is potential as an ultrasensitive analytical method in point-of-care testing, clinical diagnosis, food inspecting and environmental monitoring.
关键词： Surface-enhanced Raman scattering (SERS),SERS-ICA,Diclofenac,Ag@SiO2 core-shell nanoparticles,Immunochromatographic assay (ICA)
更新于2025-09-23 15:22:29