Green synthesis of hawthorn polysaccharide-stabilized Pd@Ru nanozymes for sensitive colorimetric detection of organophosphorus pesticides

Organophosphorus pesticides (OPs) pose a significant threat to food safety due to their high toxicity and tendency to bioaccumulate. Conventional detection methods are constrained by reliance on specialized equipment and complex procedures, hindering rapid, on-site screening. In this study, a green synthesis approach was employed using hawthorn polysaccharide (HP) as a natural stabilizer to fabricate bimetallic Pd@Ru nanozymes (HP-Pd_mRu_n NPs). The synergistic effect between palladium and ruthenium markedly enhanced the nanozymes' peroxidase-like catalytic activity and stability. Their catalytic behavior followed typical Michaelis-Menten kinetics, exhibiting a strong affinity for the substrate 3,3',5,5'-tetramethylbenzidine (TMB). A colorimetric biosensor based on HP-Pd₁₀Ru₂₀ NPs enabled rapid and sensitive detection of glyphosate, with a detection limit as low as 0.179 ng/mL and a linear range of 0.0002-200 μg/mL. The biosensor demonstrated excellent selectivity and recovery, offering promising potential for bioanalytical applications and contributing to the development of environmentally friendly, cost-effective technologies for detecting OPs residues.