Electrochemical immunosensors for pesticide residue detection in food matrices

Abstract

This thesis has been developed in the framework of the European FoodSmartphone project with the objective to develop user-friendly smartphone-connected electrochemical immunosensors for pesticide residue detection in different food matrices. The target pesticides selected were atrazine, paraquat, bromopropylate and chlorpyrifos, based on their significant impact in the field of food safety. In order to achieve this objective, first the performance of the immunoreagents necessary for the detection of the selected target pesticides (atrazine, chlorpyrifos, bromopropylate and paraquat) was evaluated by Enzyme-linked immunosorbent assays (ELISA). Afterwards, several different typologies of carbon-based screen printed electrodes (SPEs) were produced, modified and characterized. The modification of the electrodes was carried out with the nanomaterial carbon black and the electrode with the best electrochemical properties was used as a platform for the development of different electrochemical immunosensors. The direct use of the SPE’s surface was proven to be successful in the detection of the herbicide atrazine in buffer and in orange juice, achieving limit of detection (LOD) values of 2.09 (0.45 µg L-1) and 2.47 nM (0.53 µg L-1) respectively. An electrochemical immunosensor was also developed for the detection of the insecticide chlorpyrifos in wheat flour samples achieving LOD values around 5 µg kg-1. The feasibility of the developed sensor as a screening method for food safety monitoring was confirmed by the analysis of real samples and their validation by ELISA and a chromatographic reference method (GC-MS). Furthermore, electrochemical immunosensors were developed in buffer for the detection of the pesticides paraquat and bromopropylate, achieving LOD values of 0.24 µg L-1 and 4.32 µg L-1 respectively. All of the achieved LOD values were well below the maximum residue limits (MRLs) established by the European Commission.

Finally, the multiplexation capabilities of the developed individual immunosensors were demonstrated with a proof-of-concept study of a smartphone-connected multiplexed sensor. The developed sensor has the potential to be integrated in an easy-to-use and affordable device, which could be used by farmers and inspectors (e.g. at borders) for at-line measurements in order to ensure food safety and quality in the coming years.