Electrochemical Determination of Clofazimine Using A Carbon Dot Polythionine Nanocomposite-Modified Screen-Printed Electrode

Abstract

Multi-drug resistant tuberculosis (MDR-TB) treatment presents significant challenges for diagnosed patients, primarily due to the harsh side effects associated with treatment coupled with time-consuming diagnostic techniques used to assess emergencies that arise from drug toxicity. Monitoring the antibiotics used in these treatments is vital to better understand the dosage requirements for affected patients. This study focuses on the fabrication, characterisation and sensor application of carbon dot polythionine (CDPTh) nanocomposites for the electrochemical detection of clofazimine (CFZ), a drug used in MDR-TB treatment. CDPTh nanocomposites were electrochemically fabricated on a screen-printed carbon electrode (SPCE) and demonstrated optimal performance at pH 4.00, which provided the highest current response compared to other pH values. The sensor was further characterised using ultraviolet–visible light spectroscopy (UV–Vis), Fourier transform infrared spectroscopy (FTIR), high-resolution scanning electron microscopy (HR-SEM) and energy-dispersive X-ray spectroscopy (EDX). Electrochemical techniques, such as cyclic voltammetry (CV) and square-wave voltammetry (SWV), were employed to optimise the sensor parameters. The surface concentration and diffusion coefficient of the CDPTh-modified electrodes were determined to be 2.125 × 10⁻⁷ mol cm⁻² and 2.063 × 10⁻⁸ cm² s⁻¹, respectively. Stability testing using CV indicated that the nanocomposite remained 60% stable for 12 h, with a noticeable decrease in current observed thereafter. CFZ was effectively detected after the sensor fabrication within the linear range of 100–1300 nM. Interference studies were performed with chlorine ions and oxygen that were present in the phosphate buffer solution (PBS), as oxygen is always available and chlorine ions are commonly found in the water used to prepare PBS. The CDPTh sensor successfully determined CFZ using SWV anodic scans, achieving a limit of detection (LOD) of 24.4 nM and a limit of quantification (LOQ) of 81.4 nM.