Characterization of monoclonal antibodies to 2,4-dichlorophenoxyacetic acid using a piezoelectric quartz crystal...

Piezoelectric quartz crystals (resonance frequency 10 MHz) were used for an investigation of the immunochemical reaction between 2,4-dichlorophenoxyacetic acid (2,4-D) herbicide and several monoclonal antibodies prepared against 2,4-D. The herbicide was immobilized on the gold electrodes of the crystals silanized with 3-aminopropyltriethoxysilane. The activated carboxylic group of 2,4-D was linked either directly to the silanized surface or through hexamethylenediamine or albumin as a macromolecule. The interaction of the immobilized antigen with monoclonal antibody in solution was followed as a change in the resonant frequency of the crystals. The best results were achieved using 2,4-D attached to albumin. The affinity binding of five monoclonal antibodies was characterized by association (ka) and dissociation (kd) kinetic rate constants and by equilibrium association constants (KA) which were obtained from the experimental frequency vs. time curves.