November 26, 2021 11:00
Title: Electrochemical immunosensor for pesticide residue detection in food matrices
Directors: M.-Pilar Marco and Roger Galve
Thesis Committee: César Fernández Sánchez, Davide Migliorelli and Maria Isabel Pividori Gurgo
The present doctoral thesis has been developed in the framework of the European FoodSmartphone (Smartphone analyzers for on-site testing of food quality and safety) project with the main objective of developing user-friendly smartphone-connected electrochemical immunosensors for pesticide residue detection in different food matrices. The thesis describes the production of several different typologies of carbon-based screen printed electrodes (SPE) that were later applied for pesticide residue detection. Different materials were investigated during the printing process and the working electrode was modified with the nanomaterial carbon black in different ways. After an electrochemical characterization, the best performing SPE was selected and its performance was evaluated by using it directly as a platform for the development of an immunosensor for the detection of the herbicide atrazine in orange juice, achieving a limit of detection (LOD) value around 0.5 µg kg-1. Additionally, the development of an electrochemical immunosensor for the detection of the insecticide chlorpyrifos in wheat flour samples, achieving LOD values around 5 µg kg-1 is described. The feasibility of the developed sensor as a screening method for food safety monitoring was confirmed by the analysis of naturally contaminated samples and their validation by ELISA and a chromatographic reference method (GC-MS).Furthermore, electrochemical immunosensors were developed in PBST buffer for the detection of the herbicide paraquat and for the first time for the insecticide bromopropylate, achieving LOD values (0.24 µg kg-1 and 4.32 µg kg-1 respectively) well below the European Commission’s maximum residue limits. In the case of bromopropylate, the matrix effects of different juice (apple and peach) and jam (apricot and strawberry) samples were also studied in the ELISA format. 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.