Molecular Recognition-Based Detection: Antibody Dipsticks for Cyclic Organochlorine Chemicals

Cyclic organochlorine chemicals (COCs), including dieldrin, endrin, endosulfan, aldrin, heptachlor, chlordane, and toxaphene, persist globally as carcinogenic and neurotoxic persistent organic pollutants, posing bioaccumulation risks. In this study, we designed two haptens based on the common hexachlorocyclopentadiene and norbornane structural scaffolds shared by these seven COCs. The design rationale was evaluated using computational chemistry assistance and validated through animal immunization, followed by immunological analysis data. Based on the predicted hapten H1, a broad-spectrum monoclonal antibody (2A11) was prepared with a sensitivity as low as 14.91 ng/mL. Through the molecular recognition mechanism, the key amino acid residues, HIS-31 and TYR-33, responsible for the broad-spectrum binding and sensitivity to COCs were elucidated. Subsequently, a rapid and broad-spectrum colloidal gold immunochromatographic assay (GICA) was developed. The visual detection limits for the seven COCs were determined to be 10-100 ng/mL in water and 50-500 ng/g in both fish and soil, respectively. Furthermore, results from the analysis of unknown samples showed a good agreement between GICA and gas chromatography-tandem mass spectrometry. The computer-aided chemistry-based hapten prediction strategy effectively guided the preparation of antibodies for broad-spectrum recognition of COCs, enabling their rapid screening and detection.