Razi University

  Cholesterol is an essential component of cell membranes and a precursor of several biologically important molecules; however, elevated serum cholesterol is a major risk factor for atherosclerosis and cardiovascular disease. Although conventional enzymatic assays are widely used for cholesterol determination, their dependence on costly and environmentally sensitive enzymes limits their stability, reproducibility, and long-term application. Therefore, non-enzymatic electrochemical sensors based on synthetic recognition elements, particularly molecularly imprinted polymers (MIPs), have attracted increasing attention as stable, selective, and cost-effective alternatives.This thesis focuses on the development and evaluation of two complementary MIP-based electrochemical platforms for the non-enzymatic determination of cholesterol. In the first approach, a carbon paste electrode (CPE) was modified with an ionic liquid to improve conductivity and electron-transfer properties, followed by in-situ formation of a cholesterol-imprinted polymer layer. The sensor exhibited a linear response over 5–50 nM cholesterol, with an LOD of 3.62 nM and an LOQ of 10.98 nM using the ferri/ferrocyanide redox couple as an electrochemical probe. Its analytical performance was successfully validated using human serum samples and compared with the standard enzymatic-colorimetric method.In the second approach, a flexible carbon cloth (CC) electrode was modified with in-situ synthesized CuS nanostructures to provide an enlarged electroactive surface, followed by electropolymerization of a cholesterol-imprinted polymer. This architecture combines the flexibility and conductivity of carbon cloth, the electrochemical properties of CuS nanostructures, and the molecular selectivity of MIPs. The developed sensor showed dual linear responses in the ranges of 5–100 nM and 105–210 µM, with an LOD of 8.11 nM and an LOQ of 27.0 nM in the lower range. The sensor also demonstrated good selectivity, reproducibility, stability, and successful application to human serum samples.Overall, this thesis demonstrates two effective enzyme-free electrochemical strategies for cholesterol detection, progressing from a CPE/IL/MIP platform to an advanced flexible CC/CuS/MIP architecture. Both sensors combine molecular recognition with simple and cost-effective electrochemical detection and demonstrate promising potential for reliable cholesterol monitoring in point-of-care applications.