A portable surface plasmon resonance sensor system for real-time monitoring of small to large analytes (original) (raw)
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Portable 24-analyte surface plasmon resonance instruments for rapid, versatile biodetection
Biosensors and Bioelectronics, 2007
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 × 22 cm × 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 × 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.
Analytical Biochemistry, 2009
Three sensitive and original transduction techniques have been used to monitor the immobilization of anti-rabbit immunoglobulins (anti-rIgGs) and the detection of rIgGs on gold transducers. Polarization modulation-reflection absorption infrared spectroscopy (PM-RAIRS), quartz crystal microbalance with dissipation measurements (QCM-D), and Fourier transform-surface plasmon resonance (FT-SPR) were combined to achieve the best sensitivity and a large dynamic range in the target detection step. Their performances were compared after having checked that the layers adsorbed on the three different gold substrates were identical. The studied immunosensors were elaborated by building a thiolamine layer on gold surface, followed by its derivatization by glutaraldehyde and covalent binding of a monoclonal secondary IgG. The antibody attachment step was monitored in a wide range of concentrations (1-50 lg/ ml). Then the built immunosensors were used to detect the rIgG recognition. PM-RAIRS analyses, performed under air, supplied ex situ data, whereas FT-SPR and QCM techniques were used in situ, enabling on-line detection of recognition processes. Interestingly, the three techniques suggested that the antibody coverage gets saturated for approximately 20 lg/ml in solution. In the very low concentration range (1 lg/ml), antibody binding was detected by the three techniques, but FT-SPR leads to an intense signal with a wavenumber shift of approximately 30 cm À1 ; one may expect, by FT-SPR, a detection limit of the order of a few tenths of lg/ml. Ongoing experiments aim at determining the limit of detection and dynamic range of the very promising FT-SPR technique.
Biosensors and Bioelectronics, 2007
A simple and versatile miniaturized surface plasmon resonance (SPR) immunosensor enabling parallel analysis of multiple analytes or multiple samples of an analyte has been investigated for detection of a low-molecular-weight (lmw) toxin, 2,4-dichlorophenoxyacetic acid (2,4-D). A specially designed multi-microchannel SPR sensor module, integrating an optical-prism coated with an array of thin Au-films, a multi-microchannel plate (eight channels) and a flow-cell together, has been fabricated. The sensing surface was fabricated simply by physical adsorption of a protein conjugate of 2,4-D, and an indirect competitive immunoassay principle has been applied for the quantification of 2,4-D. Multiple 2,4-D samples were analyzed in a single step and a low-detection-limit (LDL) of 0.1 ppb (ng ml −1) 2,4-D was established. Competence of the portable SPR immunosensor for selective detection of 2,4-D despite the presence of various structurally resemblant interferents and from river-water samples has been demonstrated. The independent all-in-one sensor module highly favors shelf-storage between multiple determinations, and reusability of a same multi-microchannel flow-module for more than 35 days with intermittent storage (4-8 • C) has been confirmed. The LDL of 2,4-D could be enhanced further by introducing a simple avidin-biotin interaction-based sandwich immunoassay, with which the sensor signal multiplied enormously by a factor of ca. 10 and the LDL enhanced to 0.008 ppb. The miniature SPR sensor demonstrated here for simultaneous analysis of multiple samples with reusability and good storage ability is an important consideration for the advancement of biosensor technology.
Talanta, 2003
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 goldthin 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 Á/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 0.0018 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 2,4dichlorophenol conjugated with bovine serum albumin (BSA). In the competitive assay, a 350 ppm 2,4-dichlorophenol Á/ BSA conjugate solution containing 2,4-dichlorophenol at various concentrations (10 Á/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.
Applied Optics, 1990
The most sensitive existing assays used to determine antibody levels in blood serum samples require a tracer material, e.g., radioisotope, fluorofore, or enzyme, to identify the specific analyte. Surface plasmon spectroscopy has been applied recently as a no-label technique for the assay of specific antibody solutions with the antigen proteins immobilized on a metal surface. It is found that the metal surface configuration originally proposed for the surface plasmon immunoassay (SPI) is unstable and unsuitable for the assay of specific antibodies in a large mixture of proteins such as in a blood serum. Nevertheless, by properly designing the metal surface structure, the SPI can be made an extremely practical device. Preliminary results for the assay of dinitrophenyl (DNP) and keyhole limpet hemocyanin (KLH) antibodies in blood serum samples, indicate that the SPI, in addition to providing a simple and fast measurement, is comparable with existing approaches, such as radioimmunoassy or enzyme-linked immunosorbent assay both in sensitivity and specificity.
Once viewed solely as a tool to analyse biomolecular interactions, biosensors are gaining widespread interest for diagnostics, biological defense, environmental and quality assurance in agriculture/food industries. Advanced micro fabrication techniques have facilitated integration of microfluidics with sensing functionalities on the same chip making system automation more convenient1. Biosensor devices relying on lab-on-a-chip technologies and nanotechnology has attracted much of attention in recent years for biological defense research and development. However, compared with the numerous publications and patents available, the commercialization of biosensors technology has significantly lagged behind the research output. This paper reviews the reasons behind the slow commercialisation of biosensors with an insight to the critical stages of a biosensor development from the sensor chip fabrication to surface chemistry applications and nanotechnology applications in sensing with case studies. In addition, the paper includes the description of a new biodetection platform based on Real-time Electrochemical ProfilingTM (REPTM) that comprises novel electrode arrays and nanoparticle based sensing. The performance of the REPTM platform has been tested for the detection of Planktothrix agardhii, one of the toxic bloom-forming cyanobacteria, usually found in shallow fresh water sources that can be used for human consumption. The optimised REPTM assay allowed the detection of P. agardhii DNA down to 6 pM. This study, showed the potential of REPTM as a new biodetection platform for toxic bacteria and hence further studies will involve the development of a portable multi-analyte biosensor based on REPTM technology for on-site testing.
Biosensors and Bioelectronics, 2003
A surface plasmon resonance (SPR)-immunosensor for detection of benzo[a]pyrene (BaP) is developed by using a model BaPhapten compound, BaP-bovine serum albumin conjugate (BaP Á/BSA), and an anti-BaP Á/BSA monoclonal antibody. BaP Á/BSA conjugate is immobilized on a gold thin-film sensor chip by means of simple physical adsorption. The number of BaP-hapten units in BaP Á/BSA conjugate is estimated to be 28 from the difference in molecular weight (MW) between BaP Á/BSA conjugate and BSA based on the results of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) measurement. Anti-BaP Á/BSA antibody on contact with the BaP Á/BSA conjugate immobilized sensor chip causes an increase in the incident angle of the sensor chip. Binding of anti-BaP Á/BSA antibody with surface-immobilized BaP Á/BSA conjugate is inhibited by the presence of BaP in analyte solution, because of the inhibition effect of BaP. The SPR immunosensor for BaP functioning with the indirect competitive immunoreaction of anti-BaP Á/BSA antibody between the analyte (BaP) in testing solution and the BaP Á/ BSA conjugate immobilized on the sensor chip provides a rapid determination (response time: ca. 15 min) of BaP in the concentration range of 0.01 Á/1000 ppb. The antibody anchored to the sensor chip by antigen Á/antibody binding is removed on treatment with a pepsin solution (pH 2.0) for few minutes. The SPR sensor chip is found to be reusable for more than 20 times with a little decrease (B/7%) in the sensor response. Detection of BaP by direct competitive immunoreactions is also carried out by enzymelinked immunosorbent assay (ELISA). The concentration of BaP could be determined as low as 0.01 ppb and 2 ppb using the SPR sensor and the ELISA method, respectively. The SPR sensor is found to detect BaP selectively in the presence of 2-hydroxybiphenyl (HBP); the incident angle shift of the SPR sensor for BaP is found to be same irrespective to the presence or the absence of a same concentration (as much as 30 ppb) of HBP together.
A portable automated multianalyte biosensor
Talanta, 2005
The array biosensor employs an array of capture molecules on a planar optical waveguide to interrogate multiple samples simultaneously for multiple targets. In assay development and demonstration studies published previously, we have quantified this biosensor's capability for rapid identification of a wide variety of targets in complex sample media. This paper describes the miniaturization and automation of the array biosensor for portability and on-site use. The fluidics have been redesigned and constructed with reliability and commercial production of disposable components in mind. To demonstrate the automated operation, simultaneous assays were automatically conducted on samples containing both ovalbumin and staphylococcal enterotoxin B. Results demonstrate the capability of the biosensor for detection and quantification.