Magnetic Molecularly Imprinted Polymer (MMIP) Mediated Bacterial Esterase-Based Assay for Captan Detection in Milk

In the current investigation, attempts were made to develop magnetic molecularly imprinted polymer (MMIP) conjugated with esterase inhibition-based detection method for selective extraction, concentration followed by detection of captan pesticide from the milk samples. The MMIP was synthesized based on iron magnetite (Fe3O4) encapsulated in the polymer of methacrylate (monomer) and ethyleneglycoldimethacrylate (monomer-cross-linker). It is the first time MMIP-based extraction method conjugated with the enzyme inhibition-based detection method. Different parameters like pH, temperature, and solvent for binding, washing, and elution were optimized. The MMIP was tested for binding with other related pesticides, i.e., maneb, atrazine, carbendazim, and thiram, and results showed an excellent selective binding performance for captan. The precision and accuracy of the extraction method were satisfactory for milk samples at the 20 ppm of captan spiking achieved a good recovery (%R) of 83.97 +/- 1.15% with a high relative standard deviation (RSD) of 1.93% (n= 5) for captan spiked skim milk sample and recovery (R%) of 72.8 +/- 2.11% with an RSD of 2.44% (n= 5) for captan spiked pasteurized milk sample. MMIPs were employed with developed esterase inhibition-based microtiter assay for pesticide detection and achieved an excellent limit of detection (LOD) up to 1 ppb. The extraction followed by detection of pesticide could be completed in 3.30-4.0 h. It would be a cost-effective option as compared to conventional techniques as it exploits the use of bacterial cells as an inexpensive source of enzyme, eliminating the need for expensive sample treatments as MMIP can be reused and has a long shelf-life.