A ruthenium-coordinated sodium alginate hydrogel-based electroluminescent sensor for highly sensitive analysis of Paraquat.

Abstract

Paraquat (PQ) attracts significant attention in agricultural and clinical fields due to its high herbicidal efficiency and extreme toxicity at low concentrations. Given these risks, accurate quantification of PQ is essential for effective therapeutic management and clinical intervention in poisoning incidents. In this work, a novel electrochemiluminescence (ECL) system was developed based on a ruthenium-coordinated sodium alginate (SA) hydrogel matrix. The three-dimensional porous architecture of the SA hydrogel not only provides efficient transport pathways for co-reactants and electrons, but also offers a large specific surface area for the immobilization of a greater amount of cis-dichlorobis (2,2'-bipyridine) ruthenium (II) hydrate (cis-Ru(bpy)2Cl2). Moreover, the abundant carboxyl and hydroxyl groups within the SA framework create a coordination-confined microenvironment that facilitates electron transfer, thereby significantly enhancing the ECL emission efficiency and intensity. In the presence of target PQ, it competes with the PQ-conjugated DNA strands to bind with anti-PQ antibodies, thereby reducing the frequency of catalytic hairpin assembly (CHA) and consequently decreasing the extent of ECL signal recovery. Consequently, the proposed ECL biosensor exhibited excellent sensitivity (limit of detection = 0.805 pg/mL) and wide linear range (1 pg/mL to 1 μg/mL), with considerable promise for clinical PQ analysis. Significantly, this strategy can be readily generalized to the detection of a wide range of small molecules by simply substituting the corresponding antibody, thereby expanding the available analytical arsenal for small-molecule analysis and showing strong applicability in fields like agrochemical residue surveillance and clinical testing.

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