Immunosensors fragments

K. Grennan, G. Strachan, A.J. Porter, A.J. Killard, and M.R. Smyth, Atrazine analysis using an amperometric immunosensor based on single-chain antibody fragments and regeneration-free multi-calibrant measurement. Anal Chim. Acta 500, 287-298 (2003). 

I. Vikholm, W.M. Albers, H. Valimaki, and H. Helle, In situ quartz crystal microbalance monitoring of Fab-fragment binding to hnker lipids in a phosphatidylcholine monolayer matrix application to immunosensors. Thin Solid Films 327, 643-646 (1998). 

A reversible, direct fluoroimmunosensor for human serum albumin (HS A) measurement has been described by Bright et al.(m> Antibody Fab fragments are first immobilized on small quartz plates by hinge-region thiols, and then dansylated. The immunosensor is formed by attaching the quartz plates with bound Fab to the distal end of a bifurcated fiber-optic probe, which transmits both the excitation and emission. Binding of ffSA to the immunosensor results in a three- to five-fold enhancement of dansyl fluorescence. The sensor can be reused up to 50 times, with a detection limit of about 1.8 x 10-8 M, and a somewhat limited dynamic range. 

One of the most important features in the immunosensor design is the proper choice of the immobilization method for keeping the affinity of the antibodies. As was previously demonstrated for Protein A, when the antibodies are immobilized through their Fc fragment to Protein A (or G), their Fab binding sites are mostly oriented away from the solid phase. As Protein A is able to link the Fc region of different antibodies, there is no need to modify the antibody with biotin. As an antecedent, we have previously demonstrated the utility of Protein A biocomposite (ProtA-GEB) for the universal attachment of antibodies with different specificities [54]. 

Those procedures that allow an oriented immobilization of intact antibodies, or antibody fragments, on solid supports have been the most applied in the fabrication of different immunosensors. 

Romanazzo, D., Ricci, F., Volpe, G. et al. (2010) H. vanEgmond, M. Vehniainen, G. Palleschi, Development of a recombinant Fab-fragment based electrochemical immunosensor for deoxynivalenol detection in food samples. Biosens. Bioelectron., 25,2615-2621. 

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