ELECTROCHEMICAL SENSOR FOR ANTIBIOTIC DETECTION

Abstract

The research work presented in this thesis discusses the fabrication of an electrochemical sensor utilizing a molecularly imprinted polymer approach, which provides quantitative information for detecting antibiotic residues in various fields. Antibiotics are a class of chemical compounds that are extensively used to cure and prevent infectious diseases in humans, animals, and aquaculture due to their bacteriostatic and bactericidal actions. However, most of these antibiotics are non-biodegradable and can be excreted in the form of metabolites in the environment through human or animal excreta, wastewater discharge, and agricultural land runoff. Additionally, the misuse of veterinary medicine can lead to residues in animal-derived foods, including milk, eggs, meat, and fish. These residual antibiotics or their metabolites can lead to several problems, including bacterial resistance, allergic reactions, liver damage, and cancer, thus posing a huge threat to human and animal health. Therefore, developing a sensitive and effective detection technique is crucial and necessary to accurately monitor trace amounts of antibiotic contamination, thereby protecting living beings from its injurious effects. The analytical methods commonly used for antibiotic detection are based on spectroscopic and chromatographic techniques, which have certain limitations, including long analysis times, complexity, and high expenses associated with operating highly specialized equipment, as well as low sensitivity. To overcome these limitations, we require a new method that is simple, costeffective, has a low detection limit, and is easy to use. Recently, electrochemical sensors have emerged as an attractive alternative to these conventional techniques due to their fast response, high sensitivity, the possibility of real-time analysis, and cost-effectiveness. However, natural receptors, such as antibodies, enzymes, and hormones, are utilized by these electrochemical sensors as their recognition components. Despite their high selectivity and sensitivity, they remain costly and sensitive to environmental factors. In this context, a molecularly imprinted polymer (MIP) is a suitable alternative due to x its ease of preparation, high selectivity and low cost. MIPs are synthetic materials with high recognition binding cavities that target the analyte. MIP films are fabricated via the electropolymerization of functional monomers in presence of template molecules (analyte) on the surface of electrode. Following electropolymerization, the embedded template molecules are extracted from the polymer matrix, leaving behind the cavities that resemble the template molecules’ size, shape, and functional groups. Although MIPs have garnered considerable attention due to their unique recognition ability and high selectivity efficiency, they have several drawbacks, including low sensitivity, poor adhesion to the electrode surface, and high diffusion barriers. In this regard, incorporating 2D materials with the MIP electrochemical sensor can enhance the imprinted cavities and facilitate electron transfer. Further, a novel two-dimensional material, MXene, an emerging transition metal carbide or carbonitrides, has been recognized for its electrochemical applications due to its high surfaceto-volume ratio, superior hydrophilicity, good electrical conductivity, large specific area, and superior electron transport ability. Integrating MXene with other components or functionalizing its surface can impart additional advantageous properties to the resulting composites through synergistic effects, thus enhancing the overall biosensing capabilities. This work mainly focuses on the synthesis, characterization and application of MXene (Ti3C2Tx) and its composites with TiO2, CuS, and Ag for the fabrication of a highly sensitive and selective MIP-based electrochemical sensor for the detection of antibiotic, i.e., levofloxacin. The synthesized material was electrophoretically deposited on the ITO-glass surface and then the modified electrode was coupled with the MIP film through electropolymerization. Furthermore, electrochemical response studies were performed using DPV and EIS techniques. Finally, the applicability of the fabricated platforms was validated with spiked real samples which prove their efficiency.