Integrated Electrochemical Aptasensor-Polymer Inclusion Membrane Platform for Detecting Oxytetracycline in Raw Milk

We introduce a novel integrated analytical platform for detecting antibiotic residues in raw milk. Unlike conventional approaches, this system uniquely combines polymer inclusion membrane-based extraction with an aptamer-based electrochemical sensor built on a gold-coated screen-printed graphite electrode transducer. The extraction module provides selective separation of the target analyte from the complex milk matrix, while the sensor exploits a methylene blue-tagged aptamer whose target-induced conformational change generates a measurable electrochemical signal. The integrated sensor exhibits a limit of detection of 0.267 ± 0.016 μM for oxytetracycline, below the maximum residue limit established by the U.S. Food and Drug Administration for tetracyclines. Real-time data acquisition was demonstrated in spiked raw milk samples. This approach establishes a new strategy for antibiotic monitoring in complex liquid samples, offering online detection and point-of-use capabilities.