Dual Enzyme Immunoassay with Amperometric Detection

2 Dual Enzyme Immunoassay with Amperometric Detection 

3 Dual Enzyme Immunoassay Using Electrochemical Microscopy Detection 

This is another non-competitive immunoassay using a detection antibody labeled with POD, and ferrocenyl methanol as a redox mediator, but here the detection method makes use of the electrochemical scanning microscope [91] which, as shown in Fig. 8.22, involves using a micro-electrode of 3 g in diameter to scan a smooth solid phase on which are distributed distinct microzones (50 g x 50 g) of the specific antibodies of the substances to be assayed (here HCG and PL). The micro-electrode acts as a microprobe able to identify and quantify locally the electrochemical reactions generated at the surface of the solid phase. 

Using an x-y scan, a three-dimensional image is obtained of the electrochemical phenomena occurring at the surface. In this way it is possible to obtain a quantitative image of the enzyme conjugate fixed at the surface of the antibody microzones, and thus indirectly to assay the analytes sandwiched between them. Analytical detection limits of 0.1 lU mL and 3 ng mL were established for HCG and PL respectively. 

In Europe immimoassays represented a market of 1.76 bUhon Euros in 2003 

---