Ultra-selective colorimetric sensor based on molecularly imprinted polymer for proline detection in food samples

For the first time, this work reports a colorimetric sensing platform based on MIPs for the selective determination of amino acids, with a particular focus on proline. Proline is an essential amino acid and a biomarker for many physiological states; hence, its accurate estimation is highly relevant in food quality testing and clinical diagnostics. First, precipitation polymerization was carried out to synthesize the proline-selective polymers. This polymer was then used as the recognition element in constructing a proline colorimetric sensor. In an attempt to achieve maximum sensitivity, improvements in the performance of the developed sensor were attained through systematic variations in pH, temperature, and extraction time. In this sensor, the chromogenic reagent employed was ninhydrin. This reagent undergoes a specific color change in the presence of proline, which using the colorimetric analysis via RGB factor measurements can be related to the analyte concentration. This sensor demonstrates a wide linear range of 0.5 to 700 µM for proline concentrations, with a low detection limit of 0.07 µM indicating its potential for practical applications. This platform was successfully employed to measure proline in plant samples. Moreover, the sensor exhibits excellent selectivity against other amino acids, affirming its applicability in complex real samples.