Simultaneous development of both competitive and noncompetitive immunoassays for 2,2',4,4'-tetrabromodiphenyl ether using phage-displayed peptides.

Twenty-five phages that selectively bind to a monoclonal antibody (Mab) 1H2 specific to 2,2',4,4'-tetrabromodiphenyl ether (BDE47) in the absence or presence of BDE47 have been selected from phage-display libraries containing cyclic 7-mer, linear 7-mer, and linear 12-mer randomized peptides. Competitive and noncompetitive enzyme-linked immunosorbent assays (ELISA) for BDE47 were developed by using a clone C7-1 specific to the BDE47-free Mab 1H2 and a clone XC7-8 specific to the BDE47-bound Mab 1H2, respectively. The half-maximum signal inhibition concentration (IC50) of the competitive phage ELISA and the half-maximum signal enhancement concentration (EC50) of the noncompetitive phage ELISA for BDE47 were 6.8 ng mL(-1) and 4.2 ng mL(-1), respectively. The noncompetitive phage ELISA showed higher cross-reactivity with BDE28, BDE99, and BDE100 than the competitive one, ranging between 1.3 and 6.5 % versus 0.3 and 0.8 %. Recoveries of the competitive and the noncompetitive phage ELISAs for BDE47 in sewage sludge and fillet samples were 96-124 % and 97-120 %, respectively. The results of the two types of phage ELISAs for BDE47 in the real-world samples agreed well with a gas chromatography/electron capture detector-ion trap mass spectrometer method.