基于表面等离子体共振和电化学联用的DNA传感器研究进展

表面等离子共振(surface plasmon resonance,SPR)技术旨在检测物体表面附近折射率的变化,其特点是无标记、实时、灵敏和快速,该技术多用于研究分子的相互作用,包括动力学、效率常数和大分子构象变化等。电化学(electrochemical,EC)技术是一项用于定性定量研究电子转移、物质氧化还原、界面吸附等过程的成熟技术,具有简单、低成本和设备小型化的优点。现有的DNA杂交技术,例如光学、电化学或压电转导技术,主要关注于提高DNA杂交检测系统的选择性和灵敏度。传统的SPR在DNA分析方面,由于无法测量折射率的极小变化而在超灵敏检测中的应用受到限制。因此,随着纳米材料的研发和联用技术的飞速发展,SPR与EC联用的生物传感器研究越来越成为人们关注的热点。近年来,关于SPR和EC联用在DNA检测方面的综述鲜有报道。对SPR和EC检测DNA的技术原理、联用方法、应用进展等方面作出了简要的介绍,以期为表面等离子共振和电化学联用的DNA传感器相关研究提供参考。     

Collection mode surface plasmon fibre sensors: a new biosensing platform

Sensors based on surface plasmon resonance (SPR) allow rapid, label-free, highly sensitive detection, and indeed this phenomenon underpins the only label-free optical biosensing technology that is available commercially. In these sensors, the existence of surface plasmons is inferred indirectly from absorption features that correspond to the coupling of light into a thin metallic film. Although SPR is not intrinsically a radiative process, when the metallic coating which support the plasmonic wave exhibits a significant surface roughness, the surface plasmon can itself couple to the local photon states, and emit light. Here we show that using silver coated optical fibres, this novel SPR transducing mechanism offers significant advantages compare to traditional reflectance based measurements such as lower dependency on the metallic thickness and higher signal to noise ratio. Furthermore, we show that more complex sensor architectures with multiple sensing regions scattered along a single optical fibre enable multiplexed detection and dynamic self referencing of the sensing signal. Moreover, this alternative approach allows to combine two different sensing technologies, SPR and fluorescence sensing within the same device, which has never been demonstrated previously. As a preliminary proof of concept of potential application, this approach has been used to demonstrate the detection of the seasonal influenza A virus.     

Comparative studies with surface plasmon resonance and free oscillation rheometry on the inhibition of platelets with cytochalasin E and monoclonal antibodies towards GPIIb/IIIa

In the haemostatic system a multitude of processes are intertwined in fine-tuned interactions that arrest bleeding, keep the circulatory system open, and the blood flowing. The occurrence of both surface and bulk interactions adds an additional dimension of complexity. These insights have led to the belief that global overall procedures can inform on the likely behaviour of the system in health and disease. Two sensing procedures: surface plasmon resonance (SPR), which senses surface interactions, and free oscillation rheometry (FOR), which senses interactions within the bulk, have been combined and evaluated. The contribution of blood cells, mainly platelets, to the SPR and FOR signals was explored by simultaneous SPR and FOR measurement during native whole blood coagulation, accelerated via the platelets through addition of SFLLRN peptide and inhibition of platelet aggregation with abciximab (ReoPro) and of shape change with cytochalasin E. The SPR technique was found to be sensitive to inhibition of blood cell functions such as adhesion to and spreading on surfaces, as well as platelet aggregation. SPR seemed not to be directly sensitive to fibrin polymerisation in coagulating whole blood. The FOR technique detected the coagulation as a bulk phenomenon, i.e. the gelation of the blood due to fibrin formation was detected. The combination of SPR and FOR may therefore be suitable for studies on blood cell functions during coagulation.     

Rapid and label-free bacteria detection by surface plasmon resonance (SPR) biosensors

Surface Plasmon Resonance (SPR) biosensor technology has been successfully used for the detection of various analytes such as proteins, drugs, DNA, and microorganisms. SPR-based immunosensors that coupled with a specific antigen-antibody reaction, have become a promising tool for the quantification of bacteria as it offers sensitive, specific, rapid, and label-free detection. In this paper, we review the important issues in the development of SPR-based immunoassays for bacteria detection, concentrating on instrumentation, surface functionalization, liquid handling, and surface regeneration. In addition, this review touches on the recent advances in SPR biosensing for sensitivity enhancement.     

Novel immunoassay for carcinoembryonic antigen based on protein A-conjugated immunosensor chip by surface plasmon resonance and cyclic voltammetry

In this study, an immunosensor chip utilizing surface plasmon resonance (SPR) and cyclic voltammetry (CV) was fabricated for detecting carcinoembryonic antigen (CEA). Specifically, we applied in parallel an SPR instrument and a CV device to monitor the assembly of carcinoembryonic antibody (anti-CEA) on a protein A-conjugated surface and the subsequent ligand reaction. The immunosensor chips were constructed by various concentrations of protein A. To determine the surface characteristics of different self-assembly monolayers (SAMs), several quantitative and kinetic measurements were carried out. The extent of immobilization of anti-CEA and the immune response of anti-CEA antibody against CEA were measured using the SPR instrument and CV device. The terminal functional groups of protein A have different effects on the adsorption and covalent binding of immunoprotein depending on the steric hindrance. Through the parallel measurements, we demonstrate that SPR and CV are sensitive to measure the antigen–antibody binding capacity.     

Rapid method for detection of Salmonella in milk by surface plasmon resonance (SPR)

The Plasmonic surface plasmon resonance (SPR) device was used to develop a rapid, simple and specific immunoassay for detection of Salmonella in milk. Rapid detection of Salmonella contamination is a major challenge for the food industry. Salmonella contamination is well known in all foods including pasteurised milk. The SPR assay was developed as a sandwich model using a polyclonal antibody against Salmonella as capture and detection antibody. Milk spiked with Salmonella typhimurium cells, killed by thimerosal (1%, w/w) treatment was used. Using the Plasmonic SPR assay it was possible to detect S. typhimurium down to a concentration of 1.25 x 10(5) cells ml(-1) in both milk and buffer system. The results obtained are comparable with existing, approved rapid Salmonella detection techniques. No negative effects on the sensitivity of the assay are encountered due to the milk matrix. Hence, no sample preparation or clean-up steps are required. The sample volume requirement for the assay is only 10 microl. Using the assay S. typhimurium was detected in milk within 1h, whereas the cultural techniques require 3-4 days for presumptive positive isolates and further time for confirmation. The rapid tests require at least 24h for the results. The Plasmonic SPR device operates on the Kretschmann configuration and is a cuvette-based system with the advantage of having eight channels on one single SPR chip.     

Tin Halide Perovskites: Progress and Challenges

The chemical composition engineering of lead halide perovskites via a partial or complete replacement of toxic Pb with tin has been widely reported as a feasible process due to the suitable ionic radius of Sn and its possibility of existing in the +2 state. Interestingly, a complete replacement narrows the bandgap while a partial replacement gives an anomalous phenomenon involving a further narrowing of bandgap relative to the pure Pb and Sn halide perovskite compounds. Unfortunately, the merits of this anomalous behavior have not been properly harnessed. Although promising progress has been made to advance the properties and performance of Sn‐based perovskite systems, their photovoltaic (PV) parameters are still significantly inferior to those of the Pb‐based analogs. This review summarizes the current progress and challenges in the preparation, morphological and photophysical properties of Sn‐based halide perovskites, and how these affect their PV performance. Although it can be argued that the Pb halide perovskite systems may remain the most sought after technology in the field of thin film perovskite PV, prospective research directions are suggested to advance the properties of Sn halide perovskite materials for improved device performance.     

Surface Plasmon Coupling Effect of Gold Nanoparticles with Different Shape and Size on Conventional Surface Plasmon Resonance Signal

The labeling strategy with gold nanoparticles for the conventional surface plasmon resonance (SPR) signal enhancement has been frequently used for the sensitive determination of small molecules binding to its interaction partners. However, the influence of gold nanoparticles with different size and shape on SPR signal is not known. In this paper, three kinds of gold nanoparticles, namely nanorods, nanospheres, and nanooctahedrons with different size, were prepared and used to investigate their effects on the conventional SPR signal at a fixed excitation wavelength 670 nm. It was found that the SPR signal (i.e., resonant angle shift) was varied with the shapes and sizes of gold nanoparticles in suspension at a fixed concentration due to their different plasmon absorbance bands. For gold nanorods with different longitudinal absorbance bands, three conventional SPR signal regions could be clearly observed when the gold nanorod suspensions were separately introduced onto the SPR sensor chip surface. One region was the longitudinal absorbance bands coinciding with or close to the SPR excitation wavelength that suppressed the SPR angle shift. The second region was the longitudinal absorbance bands at 624 to 639 and 728 to 763 nm that produced a moderate increase on the SPR resonant angle shift. The third region was found for the longitudinal absorbance bands from 700 to 726 nm that resulted in a remarkable increase in the SPR angle shift responses. This phenomenon can be explained on the basis of calculation of the correlation of SPR angle shift response with the gold nanorod longitudinal absorbance bands. For nanospheres and nanooctahedrons, the SPR angle shift responses were found to be particle shape and size dependent in a simple way with a sustaining increase when the sizes of the nanoparticles were increased. Consequently, a guideline for choosing gold nanoparticles as tags is suggested for the SPR determination of small molecules with binding to the immobilized interaction partners.     

Synthesis of hydrophobic nanoparticles for real‐time lysozyme detection using surface plasmon resonance sensor

Diagnostic biomarkers such as proteins and enzymes are generally hard to detect because of the low abundance in biological fluids. To solve this problem, the advantages of surface plasmon resonance (SPR) and nanomaterial technologies have been combined. The SPR sensors are easy to prepare, no requirement of labelling and can be detected in real time. In addition, they have high specificity and sensitivity with low cost. The nanomaterials have also crucial functions such as efficiency improvement, selectivity, and sensitivity of the detection systems. In this report, an SPR‐based sensor is developed to detect lysozyme with hydrophobic poly (N‐methacryloyl‐(L)‐phenylalanine) (PMAPA) nanoparticles. The SPR sensor was first characterized by attenuated total reflection‐Fourier transform infrared, atomic force microscope, and water contact angle measurements and performed with aqueous lysozyme solutions. Various concentrations of lysozyme solution were used to calculate kinetic and affinity coefficients. The equilibrium and adsorption isotherm models of interactions between lysozyme solutions and SPR sensor were determined and the maximum reflection, association, and dissociation constants were calculated by Langmuir model as 4.87, 0.019 nM⁻¹, and 54 nM, respectively. The selectivity studies of SPR sensor were investigated with competitive agents, hemoglobin, and myoglobin. Also, the SPR sensor was used four times in adsorption/desorption/recovery cycles and results showed that, the combination of optical SPR sensor with hydrophobic ionizable PMAPA nanoparticles in one mode enabled the detection of lysozyme molecule with high accuracy, good sensivity, real‐time, label‐free, and a low‐detection limit of 0.66 nM from lysozyme solutions. Lysozyme detection in a real sample was performed by using chicken egg white to evaluate interfering molecules present in the medium.     

Use of a novel micro-fluidic device to create arrays for multiplex analysis of large and small molecular weight compounds by surface plasmon resonance

There is an increasing demand to develop biosensor monitoring devices capable of biomarker profiling for predicting animal adulteration and detecting multiple chemical contaminants or toxins in food produce. Surface plasmon resonance (SPR) biosensors are label free detection systems that monitor the binding of specific biomolecular recognition elements with binding partners. Essential to this technology are the production of biochips where a selected binding partner, antibody, biomarker protein or low molecular weight contaminant, is immobilised. A micro-fluidic immobilisation device allowing the covalent attachment of up to 16 binding partners in a linear array on a single surface has been developed for compatibility with a prototype multiplex SPR analyser. The immobilisation unit and multiplex SPR analyser were respectively evaluated in their ability to be fit-for-purpose for binding partner attachment and detection of high and low molecular weight molecules. The multiplexing capability of the dual technology was assessed using phycotoxin concentration analysis as a model system. The parent compounds of four toxin groups were immobilised within a single chip format and calibration curves were achieved. The chip design and SPR technology allowed the compartmentalisation of the binding interactions for each toxin group offering the added benefit of being able to distinguish between toxin families and perform concentration analysis. This model is particularly contemporary with the current drive to replace biological methods for phycotoxin screening.     

Microfluidic systems integrated with two-dimensional surface plasmon resonance phase imaging systems for microarray immunoassay

This study reports a microfluidic chip integrated with an arrayed immunoassay for surface plasmon resonance (SPR) phase imaging of specific bio-samples. The SPR phase imaging system uses a surface-sensitive optical technique to detect two-dimensional (2D) spatial phase variation caused by rabbit immunoglobulin G (IgG) adsorbed on an anti-rabbit IgG film. The microfluidic chip was fabricated by using micro-electro-mechanical-systems (MEMS) technology on glass and polydimethylsiloxane (PDMS) substrates to facilitate well-controlled and reproducible sample delivery and detection. Since SPR detection is very sensitive to temperature variation, a micromachine-based temperature control module comprising micro-heaters and temperature sensors was used to maintain a uniform temperature distribution inside the arrayed detection area with a variation of less than 0.3 degrees C. A self-assembled monolayer (SAM) technique was used to pattern the surface chemistry on a gold layer to immobilize anti-rabbit IgG on the modified substrates. The microfluidic chip is capable of transporting a precise amount of IgG solution by using micropumps/valves to the arrayed detection area such that highly sensitive, highly specific bio-sensing can be achieved. The developed microfluidic chips, which employed SPR phase imaging for immunoassay analysis, could successfully detect the interaction of anti-rabbit IgG and IgG. The interactions between immobilized anti-rabbit IgG and IgG with various concentrations have been measured. The detection limit is experimentally found to be 1 x 10(-4)mg/ml (0.67 nM). The specificity of the arrayed immunoassay was also explored. Experimental data show that only the rabbit IgG can be detected and the porcine IgG cannot be adsorbed. The developed microfluidic system is promising for various applications including medical diagnostics, microarray detection and observing protein-protein interactions.     

The Surface Plasmon Resonance Polarizing Management in Helical Microstructure Fiber

Plasmonics - Surface plasmon resonance (SPR) is a useful phenomenon in many application fields, such as communication and sensing field. In this paper, for the first time, the SPR phenomenon in...     

Combination of Digital Image Processing and Statistical Data Segmentation to Enhance SPR and SPRi Sensor Responses

The work reports the combination of basic digital image processing (DIP) techniques and statistical segmentation strategy (SDS) to improve surface plasmon resonance curve (SPRc) and SPR imaging (SPRi) sensors' performance. The SPR image is used for sensing and monitoring biological events in the so-called SPR imaging process. In the traditional SPR process based on the attenuated total reflection (ATR) method, the image is used to create the SPR curve, and the curve features tracking is employed on sensing applications. The SPR curve features are enhanced after the pixels of the SPR image have been processed with low-complexity filters in the spatial domain (brightness, contrast, threshold, and morphological). The bootstrap was used as a statistical processing approach, selecting lines and columns from the image that was less affected by imperfections and noises in the image detector, and consequently reducing the SPR sensor instrumentation disturbances. Experimental tests with reversible binding water-mixture were performed, and both image and statistical processing were reported. The combination of DIP and SDS approaches improves the extraction of the curve features, increasing the performance in terms of resonance position sensitivity to 81%.

     

Liquid phase SPR imaging experiments for biosensors applications

Surface plasmon resonance (SPR) has recently gained attention as a label-free method for the detection of biological molecules binding onto functionalised surfaces. It is one of the most sensitive detection method for monitor variations in the thickness and refractive index in ultra-thin films. Here, the adsorption processes of oligonucleotides onto gold substrates have been investigated in aqueous buffer solution using SPR imaging measurements. The hybridization of a thiol-modified, single stranded oligonucleotide anchored to a gold surface via thiol group, with its complementary sequence has been observed and characterised monitoring the hybridization process by SPR equipment. In situ investigation of smallest changes in SPR imaging measurements dynamically performed in liquid phase in the presence of DNA complementary probes was performed. Infrared spectroscopy and scanning electron microscopy characterisation of the functionalised gold surfaces of the biosensor were compared with the images obtained by SPR experimental apparatus.     

Portable 24-analyte surface plasmon resonance instruments for rapid, versatile biodetection

Field use of surface plasmon resonance (SPR) biosensors for environmental and defense applications such as detection and identification of biological warfare agents has been hampered by lack of rugged, portable, high-performance instrumentation. To meet this need, we have developed compact multi-analyte SPR instruments based on Texas Instruments' Spreeta sensing chips. The instruments weigh 3 kg and are built into clamshell enclosures measuring 28 cm x 22 cm x 13 cm. Functions are divided between an electronics unit in the base of the box and a fluidics assembly in the lid. Automated valves and pumps implement an injection loop flow system that allows sensors to be exposed to sample, rinsed, and treated with additional reagents (such as secondary antibodies) under computer control. Injected samples flow over the surfaces of eight sensor chips fastened into a temperature-controlled silicone flowcell. Each chip has 3 sensing regions, for a total detection of 24 areas that can be simultaneously monitored by SPR. Coating these areas with appropriate antibodies or other receptors allows a sample to be screened for up to 24 different substances simultaneously. The instruments report refractive index (RI) values every second, with a typical noise level of 1-3 x 10(-6) RI units. The design of the device is described, and performance is illustrated with detection of six distinct analytes ranging from small molecules to whole microbes during the course of a single experiment.     

Hierarchical Structures Based on Two‐Dimensional Nanomaterials for Rechargeable Lithium Batteries

Two‐dimensional (2D) nanomaterials (i.e., graphene and its derivatives, transition metal oxides and transition metal dichalcogenides) are receiving a lot attention in energy storage application because of their unprecedented properties and great diversities. However, their re‐stacking or aggregation during the electrode fabrication process has greatly hindered their further developments and applications in rechargeable lithium batteries. Recently, rationally designed hierarchical structures based on 2D nanomaterials have emerged as promising candidates in rechargeable lithium battery applications. Numerous synthetic strategies have been developed to obtain hierarchical structures and high‐performance energy storage devices based on these hierarchical structure have been realized. This review summarizes the synthesis and characteristics of three styles of hierarchical architecture, namely three‐dimensional (3D) porous network nanostructures, hollow nanostructures and self‐supported nanoarrays, presents the representative applications of hierarchical structured nanomaterials as functional materials for lithium ion batteries, lithium‐sulfur batteries and lithium‐oxygen batteries, meanwhile sheds light particularly on the relationship between structure engineering and improved electrochemical performance; and provides the existing challenges and the perspectives for this fast emerging field.     

Mapping the Progress in Surface Plasmon Resonance Analysis of Phytogenic Silver Nanoparticles with Colorimetric Sensing Applications

Nanotechnology is gaining enormous attention as the most dynamic research area in science and technology. It involves the synthesis and applications of nanomaterials in diverse fields including medical, agriculture, textiles, food technology, cosmetics, aerospace, electronics, etc. Silver nanoparticles (AgNPs) have been extensively used in such applications due to their excellent physicochemical, antibacterial, and biological properties. The use of plant extract as a biological reactor is one of the most promising solutions for the synthesis of AgNPs because this process overcomes the drawbacks of physical and chemical methods. This review article summarizes the plant-mediated synthesis process, the probable reaction mechanism, and the colorimetric sensing applications of AgNPs. Plant-mediated synthesis parameters largely affect the surface plasmon resonance (SPR) characteristic due to the changes in the size and shape of AgNPs. These changes in the size and shape of plant-mediated AgNPs are elaborately discussed here by analyzing the surface plasmon resonance characteristics. Furthermore, this article also highlights the promising applications of plant-mediated AgNPs in sensing applications regarding the detection of mercury, hydrogen peroxide, lead, and glucose. Finally, it describes the future perspective of plant-mediated AgNPs for the development of green chemistry.     

Molecularly imprinted polymer sensors for detection in the gas, liquid, and vapor phase

Fast, reliable, and inexpensive analytical techniques for detection of airborne chemical warfare agents are desperately needed. Recent advances in the field of molecularly imprinted polymers have created synthetic nanomaterials that can sensitively and selectively detect these materials in aqueous environments, but thus far, they have not been demonstrated to work for detection of vapors. The imprinted polymers function by mimicking the function of biological receptors. They can provide high sensitivity and selectivity but, unlike their biological counterparts, maintain excellent thermal and mechanical stability. The traditional imprinted polymer approach is further enhanced in this work by the addition of a luminescent europium that has been introduced into the polymers to provide enhanced chemical affinity as well as a method for signal transduction to indicate the binding event. The europium in these polymers is so sensitive to the bound target; it can distinguish between species differing by a single methyl group. The imprinted polymer technology is fiber optic-based making it inexpensive and easily integratable with commercially available miniature fiber optic spectrometer technologies to provide a shoebox size device. In this work, we will describe efforts to apply these sensors for detection of airborne materials and vapors. Successful application of this technology will provide accurate low level vapor detection of chemical agents or pesticides with little to no false positives.     

Structure Design and Composition Engineering of Carbon‐Based Nanomaterials for Lithium Energy Storage

Carbon‐based nanomaterials have significantly pushed the boundary of electrochemical performance of lithium‐based batteries (LBs) thanks to their excellent conductivity, high specific surface area, controllable morphology, and intrinsic stability. Complementary to these inherent properties, various synthetic techniques have been adopted to prepare carbon‐based nanomaterials with diverse structures and different dimensionalities including 1D nanotubes and nanorods, 2D nanosheets and films, and 3D hierarchical architectures, which have been extensively applied as high‐performance electrode materials for energy storage and conversion. The present review aims to outline the structural design and composition engineering of carbon‐based nanomaterials as high‐performance electrodes of LBs including lithium‐ion batteries, lithium–sulfur batteries, and lithium–oxygen batteries. This review mainly focuses on the boosting of electrochemical performance of LBs by rational dimensional design and porous tailoring of advanced carbon‐based nanomaterials. Particular attention is also paid to integrating active materials into the carbon‐based nanomaterials, and the structure–performance relationship is also systematically discussed. The developmental trends and critical challenges in related fields are summarized, which may inspire more ideas for the design of advanced carbon‐based nanostructures with superior properties.     

Theoretical Differential Phase Analysis for Characterization of Aqueous Solution Using Surface Plasmon Resonance

Surface plasmon resonance (SPR)-based differential phase analysis has been presented. Real as well as complex plane analysis of resonance parameters have been undertaken for the optimum selection of metal thicknesses in a bimetallic SPR configuration working under both angular and spectral regime. Theoretically, we can characterize the aqueous solution in terms of this differential phase variation due to the variation of sample parameters such as concentration and temperature. In this respect, two case studies, namely, concentration of hemoglobin in human blood and sensing of temperature of water have been demonstrated and proposed theoretically. By monitoring the change of differential phase, proposed approach leads to a very sensitive measurement of concentration and temperature.