Development of an amperometric immunosensor based on flow injection analysis for the detection of red blood cells

An amperometric immunosensor, based on a non-competitive sandwich assay and flow injection analysis (FIA), was developed for the detection of human red blood cells (RBCs). A dual working electrode, on which specific IgM and non-specific IgM were chemically immobilised to form sensing and blank electrodes, respectively, was employed to determine the binding of specific blood cells and non-specific adsorption in one determination. Horseradish peroxidase (HRP)-labelled anti-blood group A IgM was used in the assay, Sensor preparation involved chemical immobilisation of the IgMs on glassy carbon electrodes using 1-ethyl-3(3-dimethyl aminopropyl)carbodiimide (EDC) as a coupling reagent in the presence of N-hydroxysuccinimide (NHS). The interference contributions, such as the non-specific adsorption of the enzyme conjugate and the blood cells, were determined and removed. A quantitative relationship between the cell binding response and its concentration was obtained in the region 1-30 x 10(8) cells ml(-1).