Acetylcholinesterase-free colorimetric sensing platform for carbosulfan detection based on hollow PDA/MnO₂ nanozyme

Rapid and accurate detection of carbosulfan residues in vegetables is important for ensuring food safety. Herein, based on the unique hydrolysis behavior of carbosulfan, a nanozyme-based colorimetric sensing platform was proposed for detection of carbosulfan. Hollow polydopamine/MnO₂ nanoparticles (H-PDA/MnO₂ NPs) with excellent oxidase-like activity were synthesized, which can promote the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) into blue oxidative product (oxTMB). Under acidic conditions, carbosulfan can be decomposed and produce reductive sulfide species (-SH), which are capable to disintegrate MnO₂ NPs, resulting in decreased oxidase-like activity of H-PDA/MnO₂ NPs. Based on the inhibitory effect on oxidase activity of H-PDA/MnO₂ NPs, an acetylcholinesterase-free colorimetric assay was proposed for detection of carbosulfan with low limit of detection of 0.63 ng mL^-1. Integrating test swabs with smartphone, a portable colorimetric sensor was constructed, showing great potential for on-site detection. To demonstrate the feasibility of this method, carbosulfan in real vegetable samples were determined.