Immunodetection of Herbicide 2,4-Dichlorophenoxyacetic Acid by Field-Effect Transistor-Based Biosensors

Abstract An immunosensor method for determination of herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) was developed. It is based on the use of the competition between 2,4-D in analyzed probes and 2,4-D-peroxidase conjugate for binding with antibodies being immobilized on porous photo-activated cellulose membranes. These membranes were attached to the gate region of pH-sensitive field transistor (FET) and electrochemical detection of enzyme activity was carried out. Mixture of ascorbic acid (0.1 mM), o-phenylenediamine (1.0 mM), hydrogen peroxide (1.0 mM) was used as substrate solution. The initial rate of pH-shift of the FETs gate region was recorded as measured parameter. The developed system permits to determine 2,4-D in water solutions for concentrations down to 1 ng/ml. This portable and inexpensive immunosensor meets modern requirements as analytical system for ecological monitoring.