Direct Piezoelectric Immunosensors for Pesticides

Abstract

Immunochemical biosensors for pesticides based on piezoelectric quartz crystals as transducers are described. The changes of resonant frequency of the crystal placed in a flow cell allow to measure mass changes on its surface resulting from binding of biomolecules. In this way, no labeling procedures are required. The biospecific interactions can be followed directly in real time using an inexpensive measuring system — frequency counter, and valuable kinetic characteristics can be obtained. The construction of immunosensors for 2,4-dichlorophenoxyacetic acid (2,4-D), atrazine and parathion uses competitive measuring procedures. The modified analyte is immobilized as a ligand on the transducer. The mixture of antibody and sample containing free analyte is injected and mass changes are recorded. The limits of detection of piezoelectric immunosensors for pesticides are close to 0.1 μg/l. A typical measurement lasts 15 min, one sensor can be used 20 to 50 times. The initial experience regarding the use of immunosensors in the presence of organic solvents is discussed.