A molecularly imprinted polymer-based electrochemical sensor for the detection of colistin in milk

Colistin, a peptide-based antibiotic, is widely used as a last-resort therapeutic agent against multidrug-resistant Gram-negative bacterial infections. In addition, colistin is extensively used as a growth promoter in livestock. The indiscriminate use of colistin and its widespread occurrence in food commodities, including milk and dairy products, pose severe risks of antimicrobial resistance and toxicity in humans, as well as environmental contamination. Various analytical methods and immunosensors have been reported for the detection of colistin and its residues; however, reliable and sensitive analytical sensors for on-site detection of colistin in food matrices are not yet explored. Owing to the improved stability and sensitivity, molecularly imprinted polymer (MIP)-based electrochemical sensors have immense potential in point-of-care detection of colistin. In the present study, an MIP-based sensor has been developed for the detection of colistin in milk, where a polypyrrole-based MIP film was synthesized electrochemically on a screen-printed gold electrode (AuSPE) using colistin as the template. The electrode was characterized morphologically and electrochemically, and the developed sensor demonstrated selective detection of colistin in the range of 0.001-100 µg mL^-1, with an LOD of 0.23 ng mL^-1. The developed colistin sensor was validated using spiked milk samples and the results were compared with those of the standard LC-MS/MS method. This MIP-based approach offers significant potential for use by food industries and regulatory agencies for rapid colistin detection to ensure food safety and human health.