Sensitive Surface Plasmon Resonance Immunosensor Research Articles

Surface plasmon resonance immunosensor for fast, highly sensitive, and in situ detection of the magnetic nanoparticles-enriched Salmonella enteritidis

A highly sensitive surface plasmon resonance (SPR) immunosensor combining antibody-functionalized Fe3O4 magnetic nanoparticles (immunoMNPs) separation is reported for rapid detection of Salmonella enteritidis (S. enteritidis) based on the sandwich immunoassay. Here, immunoMNPs simultaneously served not only as “vehicles” for rapid delivery of analyte from a sample to the sensor surface, but also as labels increasing the measured refractive index changes associated with the binding of analyte. S. enteritidis can be detected at the concentration as low as 14cfu/mL with a good linear signal range at 1.4×101–1.4×109cfu/mL. Moreover, the use of immunoMNPs gives 4 orders of magnitude improvement in the sensitivity toward S. enteritidis compared with regular SPR immunosensor with direct detection format. The selectivity of proposed SPR approach was examined with Escherichia coli K12 ER2738 and Lactobacillus LJ-3. The recovery of 92.76–113.25% was obtained in eggshell. The developed SPR immunosensor has potential to provide a simple, low-cost and sensitive method for in situ detection of foodborne pathogens.

Surface plasmon resonance immunosensor for ErbB2 breast cancer biomarker determination in human serum and raw cancer cell lysates

A highly sensitive surface plasmon resonance (SPR) immunosensor for the important ErbB2 breast cancer biomarker has been developed. Optimization of the assay has been carried out, including signal enhancement employing gold nanoparticles (GNPs). The effect of the signal amplification of the GNPs has been also studied. The assay has been tested with clinically relevant matrices. Results in 50% human serum yielded a LOD of 180 pg mL−1 which is a concentration 83 times lower than the clinical cut-off. Raw lysates from model breast cancer cell lines (SK-BR-3, MCF-7 and MDA-MB-436) have been also assayed and higher quantities of the ErbB2 protein were clearly observed in the ErbB2 over-expressing case (SK-BR-3). The results confirmed that the simple and highly sensitive SPR immunosensor represents a feasible tool for ErbB2 detection.

Surface plasmon resonance based immunosensor for the detection of the cancer biomarker carcinoembryonic antigen

An immunoassay in optimised conditions with a highly sensitive surface plasmon resonance (SPR) based biosensor was developed for the detection of the cancer biomarker carcinoembryonic antigen (CEA). Different formats of the immunoassay were initially investigated on the surface of the gold sensor chip. A self-assembled monolayer (SAM) was formed on the gold chip using 11-mercaptoundecanoic acid (MUDA), before the immobilisation of the antibodies was conducted. The assay was then formed in a direct capture and a sandwich assay. In order to increase the sensor signal the CEA antigen was incubated with the detection/capture antibody before it was injected to the sensor chip surface and the results were recorded in real-time using the Biacore 3000 instrument. A detection limit of 3ngml−1 CEA was obtained with a dynamic detection range from 3ngml−1 to 400ngml−1 with correlation coefficients of 1.00 and 0.99 for the sandwich and rabbit anti-mouse (RAM) capture assay. Kinetic data analysis was performed for the standard capture test and subsequently for the developed assays and Rmax showed an increase from 215 RU for the standard capture test to 428 RU for the RAM-capture assay and 734 RU for the sandwich assay, respectively. The developed SPR immunosensor using the sandwich assay format showed high sensitivity and reproducibility for CEA detection which makes it a promising procedure for cancer biomarker analysis.

Development of a sensitive surface plasmon resonance immunosensor for detection of 2,4-dinitrotoluene with a novel oligo (ethylene glycol)-based sensor surface

A surface plasmon resonance (SPR) immunosensor for detection of 2,4-dinitrotoluene (2,4-DNT), which is a signature compound of 2,4,6-trinitrotoluene-related explosives, was developed by using a novel oligo (ethylene glycol) (OEG)-based sensor surface. A rabbit polyclonal antibody against 2,4-DNT (anti-DNPh-KLH-400 antibody) was prepared, and the avidity for 2,4-DNT and recognition capability were investigated by indirect competitive ELISA. The sensor surface was fabricated by immobilizing a 2,4-DNT analog onto an OEG-based self-assembled monolayer formed on a gold surface via an OEG linker. The fabricated surface was characterized by Fourier-transform infrared-refractive absorption spectrometry (FTIR-RAS). The immunosensing of 2,4-DNT is based on the indirect competitive principle, in which the immunoreaction between the anti-DNPh-KLH-400 antibody and 2,4-DNT on the sensor surface was inhibited in the presence of free 2,4-DNT in solution. The limit of detection for the immunosensor, calculated as three times the standard deviation of a blank value, was 20 pg mL −1, and the linear dynamic range was found to be between 1 and 100 ng mL −1. Additionally, the fabricated OEG-based surface effectively prevented non-specific adsorption of proteins, and the specific response to anti-DNPh-KLH-400 antibody was maintained for more than 30 measurement cycles.

Development of an oligo(ethylene glycol)-based SPR immunosensor for TNT detection

This paper describes the development of novel biosensor surfaces supported by robust self-assembled monolayers (SAMs) of aromatic alkanedithiol and oligo(ethylene glycol) (OEG) linker for highly sensitive surface plasmon resonance (SPR) detection of 2,4,6-trinitrotoluene (TNT). Aromatic alkanedithiol SAMs were firstly formed on Au sensor surface and TNT analogues were immobilized on it through OEG chain. Two kinds of OEG containing amine compounds, where H2N(C2H4O)11C2H4NHCOOC(CH3)3 served as a linker to react with carboxyl groups of TNT analogues while H2N(C2H4O)3C2H4OH served as a protein non-fouling background, were covalently bound to carboxyl terminal groups of SAMs with a certain ratio. Optimal ratio of them was also examined. Three kinds of TNT analogues, namely TNP-glycine, DNP-glycine, and DNP-acetic acid were used as immobilized ligands. Highly sensitive TNT detection by indirect competitive assay was conducted on the fabricated sensor surfaces; we examined how structural variations of them affect sensitivity in order to choose optimal hapten as well to improve sensitivity. The DNP-acetic acid immobilized surface, which had the lowest affinity to the TNT antibody among the three, showed the best limit of detection (LOD) value (ca. 80ppt (pgml−1)). On the other hand, the TNP-glycine immobilized surface, which had the highest affinity, showed the worst LOD value (ca. 220ppt). The LOD got lower to ca. 50ppt by the use of the secondary antibody on the DNP-acetic acid immobilized surface. The sensor surfaces are durable for more than 100 times repeated use without any noticeable deterioration by their chemical stability and rather mild regeneration condition.

Surface Plasmon Resonance Immunosensor for Anionic Surfactants Based on an Indirect Competitive Immunoreaction

A highly sensitive surface plasmon resonance immunosensor for the determination of linear alkylbenzene sulfonate (LAS) was fabricated. The method is based on an indirect competitive reaction of an anti‐LAS antibody in a sample solution with LAS immobilized on a sensor chip and with LAS in the sample solution. A sensor chip immobilized with LAS was prepared by utilizing an electrostatic interaction between an LAS conjugate, LAS–horseradish peroxidase (LAS‐HRP), and a self‐assembled monolayer of 11‐amino‐1‐undecanethiol hydrochloride, which was preliminary prepared on a gold thin film of the sensor chip. The quantitative determination of LAS in the concentration range 10–1000 ppb was achieved by using the proposed immunosensor.

Highly sensitive surface plasmon resonance immunosensor for parts-per-trillion level detection of 2,4,6-trinitrophenol

A new surface plasmon resonance (SPR) immunosensor has been demonstrated for the determination of 2,4,6-trinitrophenol (TNP) based on the principle of indirect competitive immunoreaction using trinitrophenol–bovine serum albumin (TNP–BSA) conjugate and anti-TNP antibody. TNP–BSA conjugate was immobilized on a SPR chip by physical adsorption. TNP in solution competes with the immobilized TNP–BSA conjugate for binding with anti-TNP antibody, which inhibit the immunoreaction between TNP–BSA conjugate and anti-TNP antibody. The dependence of the inhibition to the concentration of TNP was utilized for quantification of TNP. Regeneration of the sensing surface for multiple analyses can be effected using pepsin solution. The sensor exhibited excellent sensitivity for the detection of TNP in a wide concentration range from 10 ppt to 100 ppb and has promising analytical characteristics, which can be extended to the determination of nitroaromatic explosive compounds for application to on-site detection of landmines.