ABSTRACT
A surface plasmon resonance (SPR)-immunosensor for detection of the low molecular weight compound 2,4-dinitorophenol (DNP) at ultra-low concentration has been developed. The sensor strategy is based on a competitive immunoreaction between DNP and a DNP-protein conjugate, namely DNP-bovine serum albumin conjugate (DNP-BSA). Anti-DNP monoclonal antibody was immobilized on a gold thin-film coated SPR-sensor chip by means of a chemical coupling process. DNP-BSA, on contact with the anti-DNP antibody immobilized SPR-immunosensor chip causes an increase in the resonance angle of the sensor chip. The optimum concentration of immobilized antibody on the SPR-sensor chip is 100 microg mL(-1). The SPR-immunosensor response for free DNP determination using the competitive immunoreaction had a response time of ca. 15 min. Using this method, DNP could be determined in the concentration range 1 ppt to 1 ppb. The SPR signal for ppt levels of DNP was enhanced by a factor of three by subsequently treating immuno-bound DNP-BSA with a secondary anti-DNP antibody.
Subject(s)
2,4-Dinitrophenol/analysis , 2,4-Dinitrophenol/immunology , Antibodies, Monoclonal/immunology , Antigens/immunology , Immunoassay , Serum Albumin, Bovine/immunology , Surface Plasmon Resonance/methodsABSTRACT
We developed a conventional immunosensor for fibrinogen and fibrin degradation products (FDP) to combine a quartz crystal microbalance (QCM) with the agglutination reaction of immunized latex beads. FDP induced an immunoreaction due to anti-FDP antibody immobilized latex particles. We successfully measured FDP concentration of in human serum within 10 min by QCM method. The detection range of QCM immunosensor is covered with screening concentration of FDP in serum (<10 microg/ml of FDP). The time course of latex agglutination obtained from QCM immunosensor is synchronized to that of latex photometric immunoassay. SEM was used to observe the surface of QCM that applied FDP serum. The size of latex particles agglutinated on the QCM electrode increased concomitant with FDP concentration. Frequency shift on immunoreaction explains the increased adsorption amount of agglutinated latex on QCM.
