Assay sensors

An immunoassay for the detection of PSA in PBS buffer based on a dualchannel SPR instrument with angular modulation (IBIS II) has been reported [24]. This work compared direct and sandwich detection of PSA on planar- and hydrogel-type sensor surfaces. Amplification with colloidal gold and latex microspheres, respectively, was employed in the sandwich assay. Sensor chips with carboxylated matrices of different thicknesses were used. Mouse monoclonal antibodies against PSA were immobilized on the both... 

Hofmann, O., Miller, P, SuUivan, P., Jones, T.S., deMello, J.C., Bradley, D.D.C., and deMello, A.J., Thin-film organic photodiodes as integrated detectors for microscale chemiluminescence assays. Sensors and Actuators B—Chemical, 106, 878-884, 2005. 

Other simulation experiments performed in our laboratory include design of MIP adsorbents for solid-phase extraction of atrazine [77], DDT, lindane, aflatoxin Bl, ochratoxin A, and tylosin (unpublished data) and the development of assay/ sensor recognition elements for biotin (unpublished data) and creatinine [78]. In all these cases, molecular modeling proved to be a useful tool for MIP design. It would... 

James has used alizarin red S in the design of a o-glucose-selective fluorescent assay.Sensor 62 and alizarin red S show a sixfold enhancement over PBA for o-glucose. Sensor 62 can also be used at a concentration 10 times lower than PBA. The observed stability constants (/fobs)... 

Ye, L. Haupt, K. (2004). Molecularly imprinted polymers as antibody and receptor mimics for assays, sensors and drug discovery. Analytical and Bioanalytical Chemistry, 378, 1887-1897. 

Figure 8.11 Fabrication of a boronic acid based immune-assay sensor on a screen printed electrode platform. (Reproduced from ref. 83 with the permission of Elsevier.)...

Enzyme Immunosensors. Enzyme immunosensors are enzyme immunoassays coupled with electrochemical sensors. These sensors (qv) require multiple steps for analyte determination, and either sandwich assays or competitive binding assays maybe used. Both of these assays use antibodies for the analyte of interest attached to a membrane on the surface of an electrochemical sensor. In the sandwich assay type, the membrane-bound antibody binds the sample antigen, which in turn binds another antibody that is enzyme-labeled. This immunosensor is then placed in a solution containing the substrate for the labeling enzyme and the rate of product formation is measured electrochemically. The rate of the reaction is proportional to the amount of bound enzyme and thus to the amount of the analyte antigen. The sandwich assay can be used only with antigens capable of binding two different antibodies simultaneously (53). 

Enzyme electrodes for other substrates of analytical significance have been developed. Representative examples are listed in Table 6-1. Further advances in enzyme technology, and particularly the isolation of new and more stable enzymes, should enhance the development of new biocatalytic sensors. New opportunities (particularly assays of new environments or monitoring of hydrophobic analytes) derive from the finding that enzymes can maintain then biocatalytic activity in organic solvents (31,32). 

The development of DNA sensors and high-density DNA arrays has been prompted by the tremendous demands for innovative analytical tools capable of delivering the genetic information in a faster, simpler, and cheaper manner at the sample source, compared to traditional nucleic acid assays. Nanoparticle-biopolymer conjugates offer great potential for DNA diagnostics and can have a profound impact upon bioanalytical chemistry. Nanoparticle/polynucleotide assemblies for advanced electrical detection of DNA sequences have been reviewed by Wang [145]. 

Electrogenerated chemiluminescence (ECL) has proved to be useful for analytical applications including organic analysis, ECL-based immunosensors, DNA probe assays, and enzymatic biosensors. In the last few years, the electrochemistry and ECL of compound semiconductor nanocrystallites have attracted much attention due to their potential applications in analytical chemistry (ECL sensors). 

Applicability in biological ion assay is an important factor for biocompatible potentio-metric ion sensors. Attempts were made to determine Na" " concentrations in human blood sera by using silicone-rubber membrane Na+-ISFETs based on (5) [Fig. 17(a)] [29]. The found values for Na concentration in undiluted, 10-fold diluted, and 100-fold diluted serum samples are in good agreement with the Na" " calibration plots. Even in the undiluted serum samples, only a slight potential shift was observed from the calibration. This indicates that the calixarene-based silicone-rubber-membrane Na+-ISFETs are reliable on serum Na assay. For comparison with the silicone-rubber membrane, Na -ISFETs with corresponding plasticized-PVC membrane containing (2) or (5) were also tested for the Na assay. The found values of Na" " concentration... 

The bioeompatible potentiometric ion sensors have been successfully applied for ion assay in biological systems such as human blood. They might be used in in-vivo cation assay in biological systems such as intra-arterial assay in the near future. 

Operational schematic of discontinuous biosensing system (assay), 16 3-3 Key characteristics of sensor systems, 17... 

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