Plasmonics nanoprobes: detection of single-nucleotide polymorphisms in the breast cancer BRCA1 gene

This paper describes the application of plasmonics-based nanoprobes that combine the modulation of the plasmonics effect to change the surface-enhanced Raman scattering (SERS) of a Raman label and the specificity of a DNA hairpin loop sequence to recognize and discriminate a variety of molecular target sequences. Hybridization with target DNA opens the hairpin and physically separates the Raman label from the metal nanoparticle thus reducing the plasmonics effect and quenching the SERS signal of the label. We have successfully demonstrated the specificity and selectivity of the nanoprobes in the detection of a single-nucleotide polymorphism (SNP) in the breast cancer BRCA1 gene in a homogenous solution at room temperature. In addition, the potential application of plasmonics nanoprobes for quantitative DNA diagnostic testing is discussed.     

SERS-based plasmonic nanobiosensing in single living cells

In this paper, we describe the development and application of a pH-sensitive plasmonics-active fiber-optic nanoprobe suitable for intracellular bioanalysis in single living human cells using surface-enhanced Raman scattering (SERS) detection. The effectiveness and usefulness of SERS-based fiber-optic nanoprobes are illustrated by measurements of intracellular pH in HMEC-15/hTERT immortalized “normal” human mammary epithelial cells and PC-3 human prostate cancer cells. The results indicate that fiber-optic nanoprobe insertion and interrogation provide a sensitive and selective means to monitor cellular microenvironments at the single cell level.     

Study on urinary metabolic profile of phenylketonuria by micellar electrokinetic capillary chromatography with dual electrochemical detection--potential clinical application in fast diagnosis of phenylketonuria

In this report, we present a novel approach to detect clenbuterol based on competitive surface-enhanced Raman scattering (SERS) immunoassay. Herein, a SERS nanoprobe that relies on gold nanoparticle (GNP) is labeled by 4,4'-dipyridyl (DP) and clenbuterol antibody, respectively. The detection of clenbuterol is carried out by competitive binding between free clenbuterol and clenbuterol-BSA fastened on the substrate with their antibody labeled on SERS nanoprobes. The present method allows us to detect clenbuterol over a much wider concentration range (0.1-100 pg mL(-1)) with a lower limit of detection (ca. 0.1 pg mL(-1)) than the conventional methods. Furthermore, by the use of this new competitive SERS immunoassay, the clenbuterol-BSA (antigen) is chosen to fasten on the substrate instead of the clenbuterol antibody, which could reduce the cost of the assay. Results demonstrate that the proposed method has the wide potential applications in food safety and agonist control.     

Adenine and RNA in mineral samples. Surface-enhanced Raman spectroscopy (SERS) for picomole detections

Studies on the interactions of biological macromolecules with mineral surfaces are crucial for the detecting biomarkers. But before this can be done for real samples like rocks or sediments, rational methods based on mineral models plus known amounts of nucleic acids must be developed. The methods must be very sensitive, as the amount of bound macromolecule may be very small. Surface-enhanced Raman spectroscopy (SERS) is perfect for detecting picomolar amounts of nucleic acid materials. In this study, the models used were adenine and GAAA hairpin for nucleic acids materials and a clay (montmorillonite) plus colloidal silver (used for SERS detection) for mineral supports. We have shown that OH(-) anions compete with adenine and the adenyl residues in the GAAA loop for adsorption onto nano-sized silver particles in basic medium. The GAAA adenyl moieties are less well adsorbed onto either clay or silver than is adenine. Also, the transfer of either adenine or the RNA hairpin from the clay to the silver aggregates is pH-dependent. Contact between adenine and the montmorillonite also seems to disperse adenine aggregates. The clay could also increase the flexibility of the RNA hairpin so that it is released from the clay at pH 10, and the affinity of its adenyl moieties for the metallic substrate is enhanced.     

Micro-competition system for Raman quantification of multiple glycans on intact cell surface

A micro-competition system is designed for simultaneous quantification of multiple glycans on intact cell surfaces, by integrating two-surface–one-molecule competition with surface enhanced Raman scattering (SERS). The micro-competition is achieved among multiple-polysaccharide-coated gold nanostars functionalized silica bubbles, target cells and gold nanoprobes at a micron scale. The gold nanoprobes are prepared by coating distinct Raman molecules and lectins on gold nanoparticles for signal resolution and glycan recognition, respectively. The silica bubble surface serves as an artificial glycan surface and a SERS substrate. Upon the competitive recognition of lectin to the corresponding glycan, the gold nanoprobes can be specifically captured by the bubbles and cells in a homogeneous system, and the amounts of different gold nanoprobes on bubbles are simultaneously detected by SERS to reflect the corresponding glycan amounts on the cell surface. This micro-competition system with multiple quantification capability provides a powerful tool for investigation of the complex glycan-related biological processes.     

Magnetic field induced aggregation of nanoparticles for sensitive molecular detection

A molecular detection method utilizing the magnetically induced aggregation of silver nanoparticle (NP)-embedded silica NPs for SERS activation is described. Here, silver embedded magnetic NPs (Ag-M-dots) composed of a magnetic core and silica shells, on whose surface silver NPs were formed, were used. Because the magnetic field induced aggregated Ag-M-dots exhibit a strong SERS signal compared to the dispersed Ag-M-dots, the system allows for the detection of adsorbed Raman label compound even at the 100 fM level. Adenine was tested as a model biocompound and its Raman spectrum could be observed at concentrations as low as 1 pM. The experimental results were supported by the theoretical calculations.     

Plasmonic nanoprobes for intracellular sensing and imaging

Recent advances in integrating nanotechnology and optical microscopy offer great potential in intracellular applications with improved molecular information and higher resolution. Continuous efforts in designing nanoparticles with strong and tunable plasmon resonance have led to new developments in biosensing and bioimaging, using surface-enhanced Raman scattering and two-photon photoluminescence. We provide an overview of the nanoprobe design updates, such as controlling the nanoparticle shape for optimal plasmon peak position; optical sensing and imaging strategies for intracellular nanoparticle detection; and addressing practical challenges in cellular applications of nanoprobes, including the use of targeting agents and control of nanoparticle aggregation.

Ultrasensitive SERS Detection of Lysozyme by a Target‐Triggering Multiple Cycle Amplification Strategy Based on a Gold Substrate

An ultrasensitive surface enhanced Raman scattering (SERS) method has been designed to selectively and sensitively detect lysozyme. The gold chip as the detection substrate, the aptamer‐based target‐triggering cascade multiple cycle amplification, and gold nanoparticles (AuNPs) bio‐barcode Raman probe enhancement on the gold substrate are employed to enhance the SERS signals. The cascade amplification process consists of the nicking enzyme signaling amplification (NESA), the strand displacement amplification (SDA), and the circular‐hairpin‐assisted exponential amplification reaction (HA‐EXPAR). With the involvement of an aptamer‐based probe, two amplification reaction templates, and a Raman probe, the whole circle amplification process is triggered by the target recognition of lysozyme. The products of the upstream cycle (NESA) could act as the “DNA trigger” of the downstream cycle (SDA and circular HA‐EXPAR) to generate further signal amplification, resulting in the immobility of abundant AuNPs Raman probes on the gold substrate. “Hot spots” are produced between the Raman probe and the gold film, leading to significant SERS enhancement. This detection method exhibits excellent specificity and sensitivity towards lysozyme with a detection limit of 1.0×10^?15 M . Moreover, the practical determination of lysozyme in human serum demonstrates the feasibility of this SERS approach in the analysis of a variety of biological specimens.     

Simultaneous and multiplex detection of exosomal microRNAs based on the asymmetric Au@Au@Ag probes with enhanced Raman signal

Simultaneous and quantitative detection of multiple exosomal micro RNAs(miRNAs) was successfully performed by a surface-enhanced Raman scattering(SERS) assay consisting of Raman probes and capture probes. In this design, the asymmetric core-shell structured Au@Au@Ag nanoparticles were first synthesized by layer-by-layer self-assembly method and modified with different Raman molecules and recognition sequences(poly A-DNA) to prepare the surface-enhanced Raman probes. Then, the streptavidinmodifie...     

Nanostructured DNA Microarrays for Dual SERS and Electrochemical Read‐out

We present a strategy to fabricate nanostructured microarrays ready to perform a dual read‐out, namely electrochemical (EC) as well as surface‐enhanced Raman spectroscopy (SERS) based detection of DNA hydridization. A polystyrene nanobeads monolayer assembly, obtained by means of a Langmuir Blodgett type technique, followed by electrochemical Au deposition, was employed to construct homogeneous nanostructures in the form of inverse‐opal nanovoids on a 32‐electrode Au microarray chip. Characterization of the obtained nanostructured electrodes of the array by means of cyclic voltammetry demonstrated high reproducibility of the surface modification process. The performance of the obtained array platform was investigated by modifying the microarray electrodes with three different oligonucleotide capture probes using a previously developed potential‐assisted surface modification protocol. Two ferrocene‐labeled target DNA sequences and one target RNA sequence with a Texas red label were detected electrochemically and via SERS, respectively.     

A SERS DNAzyme biosensor for lead ion detection

SERS biosensor for sensitive and selective detection of lead ions (Pb(2+)) based on DNAzyme was developed by taking advantage of the specific catalytic reaction of DNAzyme upon binding to Pb(2+) ions. Detection was accomplished by SERS nanoprobe labeled with DNA and Raman reporters for signal amplification.     

SERS标记的金纳米棒探针用于免疫检测

报道了基于金纳米棒表面增强拉曼散射(SERS)的免疫检测. 将拉曼活性分子对巯基苯甲酸吸附于金纳米棒表面, 制备出SERS标记的金纳米棒探针. 该探针和蛋白抗体结合形成SERS标记抗体. 通过SERS标记抗体、待测抗原和俘获抗体(固体基底上修饰的抗体, 即俘获抗体)之间的免疫应答反应, 将金纳米棒探针组装到固体基底上, 形成SERS标记抗体-抗原-俘获抗体 “三明治”夹心复合体. 待测抗原浓度越大, 固体基底上俘获的金纳米棒探针的数目越多, 从而可通过SERS信号的强弱来检测待测抗原的浓度. 由于金纳米棒的表面等离子体共振(SPR)峰位置可以在较宽的范围内调控, 可通过激发光和SPR的耦合来提高SERS信号, 从而提高免疫检测的灵敏度. 单组分抗原可检出的浓度范围高于1×10－8 mg/mL.     

Single-step multiplex detection of toxic metal ions by Au nanowires-on-chip sensor using reporter elimination

We have developed a Au nanowires (NWs)-on-chip surface-enhanced Raman scattering (SERS) multiplex sensor that can sensitively detect multiple toxic metal ions. Most importantly, the reporter elimination method simplified the detection procedure to a single step, which has been much desired for remote environmental monitoring. This sensor has several notable features. First, it shows high reproducibility based on well-defined single-crystalline Au NWs. Second, single-NW-sensors that can detect a specific metal ion are combined for multiplex sensing of metal ions. Third, when a sample solution is put onto the NWs-on-chip sensor, a decrease in the SERS signal of a specific NW-sensor identifies the target metal ion. Simple, rapid, sensitive and quantitative detection of metal ions becomes possible through the measurement of the SERS signals. We successfully detected ions of mercury (Hg(2+)), silver (Ag(+)), and lead (Pb(2+)) coexisting in the same solution by using this sensor.     

A SERS-based immunoassay for porcine circovirus type 2 using multi-branched gold nanoparticles

We report on a facile immunoassay for porcine circovirus type 2 (PCV2) based on surface enhanced Raman scattering (SERS) using multi-branched gold nanoparticles (mb-AuNPs) as substrates. The mb-AuNPs in the immunosensor act as Raman reporters and were prepared via Tris base-induced reduction and subsequent reaction with p-mercaptobenzoic acid (pMBA). They possess good stability and high SERS activity. Subsequently, the modified mb-AuNPs were covalently conjugated to the monoclonal antibody (McAb) against the PCV2 cap protein to form SERS immuno nanoprobes. These were captured in a microtiterplate via a immunoreaction in the presence of target antigens. The effects of antibody concentration, reaction time and temperature on the sensitivity of the immunoassay were investigated. Under optimized assay conditions, the Raman signal intensity at 1,076 cm^?1 increases logarithmically with the concentrations of PCV2 in the concentration ranging from 8?×?10² to 8?×?10⁶ copies per mL. The limit of detection is 8?×?10² copies per mL. Compared to conventional detecting methods such as those based on PCR, the method presented here is rapid, facile and very sensitive.

Bioorthogonal SERS Nanoprobes for Mulitplex Spectroscopic Detection,Tumor Cell Targeting,and Tissue Imaging

A surface‐enhanced Raman scattering (SERS) technique shows extraordinary features for a range of biological and biomedical applications. Herein, a series of novel bioorthogonal SERS nanoprobes were constructed with Gold nanoflower (AuNF) and Raman reporters, the signals of which were located in a Raman‐silent region of biological samples. AS1411 aptamer was also co‐conjugated with AuNF through a self‐assembled monolayer coverage strategy. Multiplex SERS imaging using these nanoprobes with three different bioorthogonal small‐molecule Raman reporters is successfully achieved with high multiplexing capacity in a biologically Raman‐silent region. These Raman nanoprobes co‐conjugated with AS1411 showed high affinity for tumor cells with overexpressed nucleolin and can be used for selective tumor cell screening and tissue imaging.     

水汽界面二维银颗粒表面上的单分子拉曼光谱检测

随着各种超灵敏分析仪器的发展 ,已经可以在低温固体中、室温液体中和电介质表面检测、鉴定单分子及其动力学行为 .这种新进展为科学家在分析化学、分子生物学和纳米结构材料等各种学科的应用开辟了许多新的视窗 .单分子谱学的研究在基础科学和应用科学方面引起了人们广泛的兴趣 .人们不仅希望能够“看到”单分子 ,而且希望了解单分子的物理化学行为 .在各种超灵敏检测技术中 ,拉曼光谱成为一种重要的技术 .由于原子力显微等微区技术的发展 ,并结合高灵敏度检测技术的进步 ,拉曼光谱已经发展成为一种检测灵敏度可以达到分子级的检测技术 [1,…     

表面增强拉曼光谱检测联苯胺

采用柠檬酸钠还原法制备了具有表面增强拉曼散射(SERS)活性的银纳米溶胶, 利用透射电子显微镜、 扫描电子显微镜和紫外-可见光谱仪对银纳米溶胶进行了表征. 对水相的联苯胺进行了SERS研究, 并对联苯胺的拉曼谱带进行了归属. 考察了团聚剂氯化镁的浓度对检测的影响, 发现随着氯化镁浓度的变大, SERS信号呈现出先增大后减弱的趋势, 即氯化镁的浓度存在一个最佳值, 此时联苯胺的检测限可达到10^-8 mol/L.     

几种卟啉在化学还原沉积银膜上的表面增强拉曼光谱特征

应用 Ｊｏｂｉｎ－Ｙｖｏｎ Ｕ—１０００型拉曼光谱仪和ＬＡＢＲＡＭＩ型拉曼光谱系统研究了 ３种卟啉ＴＯＨＰＰ、ＴａｍＰＰ和ＴＳＰＰ在化学还原沉积法制备的银膜上的ＲＳ和ＳＥＲＳ光谱特征。结果表明：化学还原法制备的银膜可以作为这几种卟啉的拉曼增强活性载体。这３种卟啉在获谱的过程中都形成二聚态化合物和发生银离子搀和作用，较长的放置和测谱时间有利于银离子的搀和。     

双金属双硅层核-壳纳米结构Au@SiO2@Ag@SiO2用于葡萄糖检测

制备了一种灵敏度高、 稳定性强的双金属双硅层核-壳结构纳米材料Au@SiO₂@Ag@SiO₂. 由于双金属之间的硅层促进了远程等离子体的激发转移, 使该纳米粒子具有良好的表面增强拉曼散射(SERS)的特性及优异的稳定性. 利用这种SERS活性材料能直接检测出人体尿液的主要成分, 且该材料呈现出对低浓度(10^-6 mol/L)葡萄糖的无标记高效检出能力. 此外, 还实现了人工尿液中等浓度(10^-3 mol/L)葡萄糖和尿素分子的同时检测, 以及实际尿液中10^-3 mol/L葡萄糖的检测. Au@SiO₂@Ag@SiO₂纳米粒子具有在多种生物分子存在时快速检测葡萄糖的实际应用潜力.