Advanced, high sensitivity QCM piezoelectric immunosensors for pesticide analysis, based on the measurement of phase changes at high fundamental frequency (HFF)

Authors: A. Montoya, J.J. Manclús, A. Arnau, Y. Jiménez, J.V. García-Narbón, C. March

Event:  8th MGPR International Symposium of Pesticides in Food and the Environment in Mediterranean Countries. Cappadocia,  Turkey (2013)


The detection of very small mass changes by means of the Quartz Crystal Microbalance (QCM) is a very popular transduction technique in biosensor design for analytical applications. In fact, QCM biosensors for pesticide analysis in fruit and derived products have recently been reported. Despite their interesting analytical performance, these biosensors still need a thorough optimization of several essential analytical parameters. In particular, sensitivity and limit of detection should be significantly improved, so that pesticide biosensors could extend their applicability to more demanding applications, such as the analysis of drinking water. In order to overcome these limitations, a new concept of piezoelectric biosensor is proposed. Unlike classic QCM, where frequency changes are detected as the response to small mass changes, the new biosensor is based on the detection of phase changes, working at high constant frequency (high fundamental frequency: HFF). On this basis, a new 100 MHz QCM immunosensor based on monoclonal antibodies for pesticide analysis has been developed. A completely new device including a dedicated PEEK chip support to attach the HFF functionalized crystals, the automatic injection system, and the electronic characterization system, has been designed and built. Carbaryl and Thiabendazole were chosen as model pesticides to assess the immunosensor performance. Specific monoclonal antibodies were used as biorecognition molecules, working in competitive immunoassays in the conjugate-coated format. Specific hapten conjugates were covalently attached to the gold surfaces of the sensor electrodes by alkanethiol self-assembled monolayers (SAM). As compared to the previous low-frequency QCM immunosensors, the sensitivity was improved by more than a one order of magnitude (I50 values in the sub-µg I-1 range), whereas the limits of detection improved by around two orders of magnitude (LODs around 0.16 µg I-1). Immunoregent consumption was decreased by 5 times (antibody) and 1000 times (assay conjugate). The high sensitivity reached by these immunosensors allows pesticide analysis at concentrations near the European MRLs for drinking water.