Molecular imprinted lipid membranes towards the fabrication of electrochemical sensor for methylene blue

Abstract

In this work, we present for the first time an electrochemical sensor based on molecularly imprinted lipid membranes (MIM) for selective detection of methylene blue (MB) dye. The novelty is found in the use of a phospholipid (1,2-Dipalmitoyl-sn-3-Glycero-Phosphatidylcholine) (DPPC) mixed with a cationic polyelectrolyte poly(allylamine hydrochloride) (PAH) as the matrix to manufacture a thin film membrane. PAH was added to improve membrane stability acting as a crosslinker in analogy to a molecularly imprinted polymer (MIP) system. For the sensor fabrication, Langmuir monolayers of DPPC with PAH and MB (template molecules) were investigated to further transfer to indium tin oxide (ITO) electrodes by the Langmuir-Schaefer (LS) technique. After the removal of the template molecules by simply cycling in KCl electrolyte, differential pulse voltammetry was applied to quantify MB analyte. A limit of detection of 3.4 × 10−7 mol/L was calculated and the selectivity of the ITO/MIM electrode for MB was confirmed in solutions of quercetin and equimolar mixtures of them. This work introduces a highly selective, and stable sensor design, advancing the surface science application of molecular imprinting in lipid membranes and offering improvements over existing detection methods.