Sensitive detection of tuberculosis using nanoparticle-enhanced surface plasmon resonance

We show that the antigen CFP-10 (found in tissue fluids of tuberculosis patients) can be used as a marker protein in a surface-plasmon resonance (SPR) based method for early and simplified diagnosis of tuberculosis. A sandwich SPR immunosensor was constructed by immobilizing the CFP-10 antibody on a self-assembled monolayer on a gold surface, this followed by blocking it with bovine serum albumin. Following exposure of the sensor surface to a sample containing CFP-10, secondary antibody immobilized on nickel oxide nanoparticles are injected which causes a large SPR signal change. The method has a dynamic range from 0.1 to around 150 ng per mL of CFP-10, and a detection limit as low as 0.1 ng per mL. This is assumed to be due to the high amplification power of the NiO nanoparticles.

Rapid analysis of coumarins using surface plasmon resonance

Coumarin molecules are ubiquitous in nature. Several have come to prominence as potential clinical therapeutic candidates. The principal example is warfarin, which is a very widely prescribed anticoagulant. Other coumarin derivatives, such as aflatoxin B1, are insidious contaminants in crop-derived foodstuffs. Extreme potency is a common feature of all biochemically active coumarins and, thus reliable methods for their rapid and sensitive detection are of paramount importance. Accordingly, this review examines the current methods used in the analysis of these molecules and compares them with immunoassay-based strategies. As a case study, we report on our experiences with using coumarin-specific polyclonal, monoclonal, and recombinant antibodies in conjunction with a surface plasmon resonance-based biosensor for analysis of coumarins. We chart the assay development process and demonstrate high sensitivity and reproducibility that compares favorably with established methodologies.     

Detection of lectin-glycan interaction using high resolution surface plasmon resonance

We report the real-time and label-free detection of direct disaccharide binding to a lectin using a differential surface plasmon resonance detection method that allows for measurement of nanomolar concentrations of disaccharides.     

Label-free detection of cancer biomarker candidates using surface plasmon resonance imaging

In this work, we present an antibody array for the detection of cancer biomarker candidates by a surface plasmon resonance (SPR) imaging sensor with polarization contrast. Responses from the SPR imaging sensor are shown to be similar to those from a conventional spectroscopy-based SPR sensor. Antibodies are spotted onto a self-assembled monolayer (SAM) composed of oligo(ethylene glycol) (OEG)-containing alkanethiol chains. Detection of two cancer biomarker candidates, activated leukocyte cell adhesion molecule/CD 166 (ALCAM) and transgelin-2 (TAGLN2), is demonstrated. Limits of detection for ALCAM and TAGLN2 are established at 6 ng/mL and 3 ng/mL, respectively, in buffer. No cross-reactivity is observed between immobilized antibodies and nonspecific antigen. Biomarker candidates are also detected in a 10% human serum solution. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Inhibition binding studies of glycodendrimer/lectin interactions using surface plasmon resonance

Understanding protein/carbohydrate interactions is essential for elucidating biological pathways and cellular mechanisms but is often difficult due to the prevalence of multivalent interactions. Here, we evaluate the multivalent glycodendrimer framework as a means to describe the inhibition potency of multivalent mannose-functionalized dendrimers using surface plasmon resonance (SPR). Using highly robust, mannose-functionalized dithiol self-assembled monolayers on gold surfaces, we found that glycodendrimers were efficient inhibitors of protein/carbohydrate interactions. IC₅₀ values ranging from 260 nM to 13 nM were obtained for mannose-functionalized dendrimers with Concanavalin A.     

Non-linear plasmon response to protein binding at a nanostructured gold particle plasmon resonance surface

Rapid adsorption kinetics have been observed for protein binding to a 800 nm aggregated nanoparticle, showing extreme sensitivity resulting from a non-linear particle plasmon response.     

Rapid detection of nivalenol and deoxynivalenol in wheat using surface plasmon resonance immunoassay

A surface plasmon resonance (SPR) immunoassay using a monoclonal antibody was developed to measure nivalenol (NIV) and deoxynivalenol (DON) contamination in wheat. A highly sensitive and stable DON-immobilized sensor chip was prepared, and an SPR detection procedure was developed. The competitive inhibition assay used a monoclonal antibody that cross-reacts with NIV and DON. The half maximal inhibitory concentration (IC₅₀) values of the SPR assay were 28.8 and 14.9 ng mL⁻¹ for NIV and DON, respectively. The combined responses of NIV and DON in wheat were obtained using a simultaneous detection assay in a one-step cleanup procedure. NIV and DON were separated using a commercial DON-specific immunoaffinity column (IAC) and their responses were obtained using an independent detection assay. Spiked tests using these toxins revealed that recoveries were in the range 91.5-107% with good relative standard deviations (RSDs) (0.40-4.1%) and that detection limits were 0.1 and 0.05 mg kg⁻¹ for NIV and DON, respectively. The independent detection using IAC showed detection limits of 0.2 and 0.1 mg kg⁻¹ for NIV and DON, respectively. SPR analysis results were correlated with those obtained using a conventional LC/MS/MS method for wheat co-contaminated with NIV and DON. These results suggested that the developed SPR assay is a practical method to rapidly screen the NIV and DON co-contamination of wheat and one of a very few immunoassays to detect NIV directly.     

用表面等离子共振仪进行生物分子相互作用研究的评述

表面等离子共振仪是测量生物分子问交互作用最为有效的手段之一，但多数实验数据是在不精确的实验设计下获得的，通过对用传统方法来优化试验设计、提高仪器灵敏度进行了总结，并对获得精确蛋白质相互作用动力学信息的新方法进行了讨论。     

A novel detection of single-stranded DNA binding protein based on ss-DNA modified chip using surface plasmon resonance microscopy

An ss-DNA gold chip was prepared based on self-assembly of the thiol-derivatized oligonucleotide,and used for thedetermination of single-stranded binding protein(SSB)by surface plasmon resonance microscopy(SPR).The experiment resultsshowed that SSB binds ss-DNA with high specificity,and relative signal of SPR response is proportional to the concentration of SSBin the range of 0.1-100 ng/mL with a detection limit(S/N=3)of 0.07 ng/mL.     

Screening nucleotide binding to amino acid-coated supports by surface plasmon resonance and nuclear magnetic resonance

Here, we describe a rapid and efficient screening method using surface plasmon resonance (SPR) and saturation transfer difference–nuclear magnetic resonance (STD-NMR) spectroscopy to yield information regarding the residues involved in nucleotide binding to amino acid-coated supports. The aim of this work was to explore the use of these spectroscopic techniques to study amino acid–nucleotide interactions in order to improve the binding specificity of the amino acid ligands used to purify plasmid DNA. For SPR, we present a strategy that immobilizes arginine and lysine on a surface as model supports, and we analyze binding responses when synthetic homo-deoxyoligonucleotides are injected over the amino acid surface. The binding responses are detectable and reproducible despite the small size of the immobilized amino acids. Using STD-NMR, we performed epitope mapping of homo-deoxyoligonucleotides bound to l-arginine–bisoxyran–Sepharose and l-lysine–Sepharose supports. Polynucleotide binding preferences differed; for example, polyC interacted preferentially through its backbone with the two supports, whereas polyT bound the supports through its thymine moiety. STD-NMR combined with SPR measurements was successfully used to screen amino acid–nucleotide interactions and determine the binding affinities of the complexes.     

Sensitive spectrophotometric detection of dopamine,levodopa and adrenaline using surface plasmon resonance band of silver nanoparticles

A simple and effective procedure is proposed for spectrophotometric determination of catecholamines; Dopamine (1), L-Dopa (2) and Adrenaline (3). It was found that the reduction of Ag⁺ to silver nanoparticles (Ag-NPs) by these catecholamines in the presence of polyvinylpyrrolidone (PVP) as a stabilizing agent produced very intense surface plasmon resonance peak of Ag-NPs. The plasmon absorbance of the Ag-NPs allows the quantitative spectrophotometric detection of the catecholamines. The calibration curves derived from the changes in absorbance at λ = 440 nm were linear with concentration of Dopamine, Levodopa and Adrenaline in the range of 3.2×10^?6? 2.0×10^?5 M, 1.6×10^?7 ? 1.0×10^?5 M, 1.5×10^?6? 4.0×10^?5 M, respectively. The detection limits (3σ) were 1.2×10^?6 M, 8.6 ×10^?8 M, 9.7 ×10^?7 M for the Dopamine, L-Dopa and Adrenaline, respectively. The method was applied successfully to the determination of catecholamines in Ringer’s injection serum.     

Rapid evaluation of nickel binding properties of His-tagged lactate dehydrogenases using surface plasmon resonance

The use of surface plasmon resonance (SPR), for the comparison of metal binding properties of polyhistidine tags, was evaluated. Six different tags containing various number of histidines, either none (tags n and t), three (tags H3A3 and HA2HA2H) or six (tags H6 and His6), were genetically fused to the N-terminal of lactate dehydrogenase (LDH). The binding ability of these constructs to nickel ions, immobilised with nitrilotriacetic acid (NTA), was tested both by conventional immobilised metal ion affinity chromatography (IMAC) and SPR. The relative binding strengths of the tags to nickel were identical using both methods (n approximately t < HA2HA2H < H3A3 < His6 < H6), confirming the value of the SPR technique for investigating metal-protein interactions. Protein modelling has also proved to be useful in supporting the experimental results.     

Chemically immobilized T4-bacteriophage for specific Escherichia coli detection using surface plasmon resonance

A bioassay platform using T4 bacteriophage (T4) as the specific receptor and surface plasmon resonance (SPR) as the transduction technique has been developed for the detection of Escherichia coli K12 bacteria. The T4 phages have been covalently immobilized onto gold surfaces using a self-assembled monolayer of dithiobis(succinimidyl propionate) (DTSP). Substrates of BSA/EA-T4/DTSP/Au prepared using different T4 phage concentrations have been characterized using scanning electron microscopy (SEM). The studies reveal that the use of DTSP results in a uniform binding of T4 phages onto the surface. The SPR analysis demonstrates that these BSA/EA-T4/DTSP/Au interfaces can detect the E. coli K12 with high specificity against non-host E. coli NP10 and NP30. Results of SEM and SPR studies indicate that the maximum host bacterial capture is obtained when 1.5 × 10(11) pfu ml(-1) concentration of T4 phages was used for immobilization. The surface of these chemically anchored phage substrates can be regenerated for repeated detection of E. coli K12 and can be used for detection in 7 × 10(2) to 7 × 10(8) cfu ml(-1) range. The results of these studies have implications for the development of online bioassays for the detection of various food and water borne pathogens using the inherent selectivity of bacteriophage recognition.     

Immobilization of Escherichia coli for detection of phage T4 using surface plasmon resonance

Phage contamination is a very serious and unavoidable problem in modern fermentation industry.It is necessary to develop sensitive and rapid phage detection methods for the early detection of phage contamination.In the present work,a real-time,rapid,specific and quantitative phage T4 detection method based on surface plasmon resonance(SPR) technique has been introduced.Escherichia coli was immobilized onto the preformed MPA self-assembled monolayer(SAM) through the widely used EDC/NHS cross-linking reaction as the recognition element.The bacteria immobilization was verified efficiently through the electrochemical measurements and fluorescence microscopy observations.The specific adsorption was much stronger than the non-specific adsorption of phage T4 binding to the biosensor surface modified by E.coli,and the latter could be neglected.The detection sensitivity reached 1×10 7 PFU/mL within 10 min.Within the experimental phage concentrations,the linear correlation between the SPR response and the phage concentration was good.The results suggest that the SPR technique is a potentially powerful tool for the phage or other virus detections,as a label-free,real-time,and rapid method.     

A gold nanoparticle labeling strategy for the sensitive kinetic assay of the carbamate-acetylcholinesterase interaction by surface plasmon resonance

The article presents a novel strategy for a sensitive investigation of the interaction between acetylcholinesterase (AChE) and its small molecular carbamate inhibitors. Two carbamate inhibitors with different ether linkages and the terminal lipoate were synthesized and labeled with gold nanoparticles (AuNPs). With the signal amplification of AuNPs, the specific interactions between the AuNPs labeled carbamate inhibitors (ALC1 and ALC2) and the immobilized AChE on sensor chip surface were readily examined. The detection sensitivities of ALC1 and ALC2 were 176 and 121 m°/nM, respectively, with the detection limits of 7.0 and 12 pM at a signal-to-noise ratio of 3. The association/dissociation constants for the binding interaction between carbamate inhibitors and AChE were reported for the first time. The affinity constants were estimated to be 3.13 × 10⁶ and 6.39 × 10⁵ M⁻¹ for ALC1 and ALC2 respectively. This AuNPs labeling strategy is versatile and may be applicable for the direct or competitive SPR kinetic assay of the interaction between small molecule inhibitors and their target proteins with a high sensitivity.     

A surface plasmon resonance immunosensor for detecting a dioxin precursor using a gold binding polypeptide

A surface plasmon resonance (SPR) based biosensor was developed for monitoring 2,4-dichlorophenol, a known dioxin precursor, using an indirect competitive immunoassay. The SPR sensor was fabricated by immobilizing a gold-thin layer on the surface of an SPR sensor chip with an anti-(2,4-dichlorophenol) antibody using a gold binding polypeptide (GBP) and protein G. The SPR response based on the antigen-antibody reaction in a flow system was measured by injecting a 2,4-dichlorophenol sample solution into the flow system in which the SPR sensor was located. In a direct immunoassay system using the modified sensor chip, no significant SPR angle shift less than 0.001° was observed when a 25 ppm of 2,4-dichlorophenol solution was injected. In order to improve the sensitivity of the SPR sensor, an indirect competitive immunoassay method was used in conjunction with the SPR sensor system using 2,4-dichlorophenol conjugated with bovine serum albumin (BSA). In the competitive assay, a 350 ppm 2,4-dichlorophenol-BSA conjugate solution containing 2,4-dichlorophenol at various concentrations (10-250 ppb) were injected into the SPR sensor system. The sensitivity of this indirect immunoassay was found to be extremely sensitive, compared to the direct one, and a detection limit of 20 ppb was estimated. Verification that the use of GBP for immobilizing the antibody on the sensor chip enhanced the sensitivity to 2,4-dichlorophenol was obtained by comparing the procedure with another modification, in which BSA was used instead of GBP for immobilizing the antibody on the sensor chip. The affinity constant of 2,4-dichlorophenol and its conjugate to the antibody were estimated form the SPR response.     

Modeling protein binding and elution over a chromatographic surface probed by surface plasmon resonance

Surface plasmon resonance (SPR) spectroscopy is used as a scaled-down, analytical, pseudo-chromatography tool for analyzing protein binding and elution over an ion-exchange surface under cyclic sorption conditions. A micrometric-scale adsorption surface was produced by immobilizing a typical ion exchange ligand – diethylaminoethyl (DEAE) – onto commercially available planar gold sensor chip surfaces pre-derivatized with a self-assembled monolayer of 11-mercaptoundecanoic acid with known density. An explicit mathematical formulation is provided for the deconvolution and interpretation of the SPR sensorgrams. An adsorption rate model is proposed to describe the SPR sensorgrams for bovine serum albumin, used here as model protein, when the DEAE surface is subjected to a cyclic series of binding and elution steps. Overall, we demonstrate that the adsorption rate model is capable of quantitatively describing BSA binding and elution for protein titers from dilute conditions up to overloaded conditions and a broad range of salt concentrations.     

Nucleic acid sensor for M. tuberculosis detection based on surface plasmon resonance

Cysteine modified NH(2)-end peptide nucleic acid (PNA) (24-mer) probe and 5'-thiol end labeled deoxyribonucleic acid (DNA) probes specific to Mycobacterium tuberculosis have been immobilized onto BK-7 gold coated glass plates for the detection of complementary, one-base mismatch, non-complementary targets and complementary target sequence in genomic DNA of Mycobacterium tuberculosis using a surface plasmon resonance (SPR) technique. The DNA/Au and PNA/Au bio-electrodes have been characterized using contact angle, atomic force microscopy (AFM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetric (CV) techniques, respectively. It is revealed that there is a 252 millidegrees SPR angle change in the case of PNA immobilization and 205 millidegrees for DNA immobilization, indicating increased amount of immobilized PNA molecules. Hybridization studies reveal that there is no binding of the non-complementary target to DNA/Au and PNA/Au electrode. Compared to the DNA/Au bioelectrode, PNA/Au electrode has been found to be more efficient for detection of one-base mismatch sequence. The PNA/Au bioelectrode shows better detection limit (1.0 ng ml(-1)) over the DNA-Au bioelectrode (3.0 ng ml(-1)). The values of the association (k(a)) and dissociation rate constant (k(d)) for the complementary sequence in case of the PNA/Au bioelectrode have been estimated as 8.5 x 10(4) m(-1) s(-1) and 3.6 x 10(-3) s(-1), respectively.