SPARK - Sensor platform for affinity recognition of paraquat

The extensive use of paraquat (PQT) in agriculture has led to considerable environmental pollution and has raised serious health issues. Rapid, sensitive, and on-site detection tools are crucial for monitoring paraquat residue and preventing its toxic effect. This study focused on demonstrating a portable, label-free electrochemical sensor platform (SPARK) for the direct detection of paraquat using edamame soybean as food matrix. The sensor platform was fabricated using the excellent substrate property of a reduced graphene oxide (rGO), which was immobilized with the anti-paraquat antibody (PQT-Ab, specific to recognize the herbicide paraquat) using a linker molecule 1-pyrenebutanoic acid succinimidyl ester (Pyr-BASE). The rate of crosslinker adsorption on rGO was evaluated and demonstrated for the first time using electrochemistry, with the calculated monolayer adsorption of the pyrene-based crosslinker found to be 244 μC/cm². The sensor performance was tested using portable device platform (SPARK) to confirm its feasibility, which showed a limit of detection (LOD) of 0.3 ng/mL (0.3 ppb), dynamic range of PQT from 0.3 to 72.9 ng/mL and an r² value of 0.98. The cross-reactivity study demonstrates high selectivity for the target PQT antigen, in presence of non-specific antigen such as glyphosate and chlorpyrifos. Pearson's correlation of r = 0.99 indicated a strong positive correlation between SPARK platform and the third-party gold standard method. Developed SPARK platform provides sensitive data comparable to traditional analytical methods in a simplified manner, thereby opening the possibility for electrochemical sensor platform to be used as on-site testing devices for various other food matrices.