EFFECTIVENESS OF PROTEIN-A FOR ANTIBODY IMMOBILIZATION FOR A FIBER OPTIC BIOSENSOR

The fiber optic biosensor performs fluoroimmunoassays at the surface o f multimode optical fibers. The effectiveness of protein A, an immunog lobulin binding protein, for antibody immobilization on the surface of these fiber probes has been investigated. No difference was observed in the binding of fluorescently-labeled goat-IgG by rabbit anti-goat I gG regardless of whether the capture antibody was bound to the probe s urface via protein A or covalently attached. However, in a sandwich im munoassay for the F1 antigen of Yersinia pestis, probes with rabbit an ti-plague IgG bound to the surface via protein A generated twice the s ignal as probes with the antibody covalently attached. Assay regenerat ion was also examined with protein A probes since antibody-antigen com plexes have been successfully eluted from protein A under low pH condi tions. Protein A probes coated with rabbit anti-goat IgG obtained near ly identical signal levels at 500 and 5000 ng/ml of Cy5.5 goat IgG fiv e consecutive times following regeneration with glycine-HCl, 2% acetic acid, pH 2.5. (C) 1997 Elsevier Science Limited.