Fabrication of an atrazine acoustic immunosensor based on a drop-deposition procedure

Among the various novel analytical systems, immunosensors based on acoustic waves are of emerging interest because of their good sensitivity, real-time monitoring capability, and experimental simplicity. In this work, piezoelectric immunosensors were constructed for the detection of atrazine through the immobilization of specific monoclonal anti-atrazine antibodies on thiolated modified quartz crystal microbalances (QCMs). The immunoassay was conducted by a novel drop-deposition procedure using different atrazine dilutions in phosphate buffer solution ranging from 10^-10 to 10^-1 mg/mL. The immunoreactions between varying contents of atrazine and its antibody were dynamically exhibited through in situ monitoring of the frequency and motional resistance changes over 20 min. Thus, atrazine recognition by the anti-atrazine antibody leads to a decrease of the resonant frequency that is proportional to a given atrazine concentration. Interestingly, the motional resistance also increased proportionally during the measurements, which could be attributed to the specific viscoelastic properties and/or conformation changes of the antibodies once the immunoreactions occurred. By combining the measurements of frequency with those of motional resistance, additional information was provided about the interaction between the atrazine-named antigen and its respective antibody. Finally, the analytical specificity of the immunosensor to atrazine was evaluated through the response to a nonspecific anti-human IgG antibody-modified QCM crystal under the same drop conditions.