Antigen-antibody affinity surface plasmon

FIG. 7.30 Electronic and optical transduction of the formation of antigen-antibody affinity complexes on transducers (A) Amperometric transduction at an electrode (R /K Is a redox label In the electrolyte solution). (B) Transduction by faradic Impedance spectrosco . (C) Microgravimetric quartz crystal microbalance (QCM) transduction in the presence of a piezoelectric quartz crystal. (D) Surface plasmon resonance transduction. 

The biosensing devices focus mainly on affinity principles such as antibody -antigen reactions and are based on surface plasmon resonance [25], grating couplers[26] or interferometers [27]. It seems possible to get stable and highly sensitive devices based on these principles [28], and further investigations can lead to miniaturized sensor modules with reduced cost, size and complexity. 

Englebienne, P. Use of colloidal gold surface plasmon resonance peak shift to infer affinity constants from the interactions between protein antigens and antibodies specific for single or multiple epitopes. Ana/yst 123, 1599-1603 (1998). 

Once phage or scFv which specifically bind the antigen of interest have been identified it may be necessary to cany out further screening tests to assess which antibodies fiom the positive population have the highest affinities. There are a variety of wtq of achieving this including surface plasmon resonance (BlAcore) screening, fluorescence quench measmement, and competition ELISAs. Descriptions of these protocols are beyond the scope of this chapter. 

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