Immunosensors cross-reactivity

Two immunosensors developed by O Regan et al. [89,90] have demonstrated their usefulness for the early assessment of acute myocardial infarction (AMI). Human heart fatty-acid binding protein (H-FABP) is a biochemical marker for the early assessment of AMI. The authors constructed an amperometric immunosensor for the rapid detection of H-FABP in whole blood. The sensor is based on a one-step, direct sandwich assay in which the analyte and an alkaline phosphatase (AP) labelled antibody are simultaneously added to the immobilized primary antibody, using two distinct monoclonal mouse anti-human H-FABP antibodies. The substrate p-amino-phenyl phosphate is converted to p-aminophenol by AP, and the current generated by its subsequent oxidation at +300 mV vs. Ag/AgCl is measured. The total assay time is 50 min, and the standard curve was linear between 4 and 250 ng ml . The intra- and inter-assay coefficients of variation were below 9%. No cross-reactivity of the antibodies was found with other early cardiac markers, and endogenous substances in whole blood did not have an... 

Pseudohomogenous amperometric displacement immunosensors have also been developed. The displacement assay is performed on a disposable screen printed carbon electrode and takes advantages of the cross-reactivity of some monoclonal antibodies. As an example, the monoclonal anti-2,4-D antibody exhibits a relative cross-reactivity toward immobilized MCPA. In the presence of the target analyte (2,4-D) a displacement effect is observed. Consequently, the peroxidase label of the remaining anti-2,4-D antibodies is detected at the carbon electrode, when adding hydrogen peroxide and potassium iodide as redox mediator, at OV versus Ag/AgCl. 

PAHs are always found as a mixture of individual compounds with similar molecular structure, similar electron density, and a lack of side groups. Therefore, an immunosensor based on SPEs was developed for PAH detection using a co-exposure competition assay. The immunosensor displayed cross-reactivities of varying degrees towards 16 important PAH compounds. ... 

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