Chemometrics-assisted electrochemical biosensing of cholesterol as the sole precursor of steroids by a novel electrochemical biosensor.

This project was performed with the aims of increasing the sensitivity of differential pulse voltammetry (DPV) which itself is a sensitive electroanalytical technique, and also to compare the area under peak (univariate calibration), height of peak (univariate calibration) and whole of vector (multivariate calibration) for calibration purposes. These topics were investigated by fabrication of a novel electrochemical biosensor for determination of cholesterol (CHO). The procedure used in this project was based on the synthesis of molecularly imprinted polymers (MIPs) to the preconcentration of CHO and its biosensing by a rotating glassy carbon electrode (GCE) modified by co-immobilization of cholesterol oxidase (CO), cholesterol esterase (CE) and horseradish peroxidase (HP) onto multiwalled carbon nanotubes-ionic liquid (COCEHP/MWCNTs-IL/GCE). The results showed that the hydrodynamic DPV (HYDPV) was much more sensitive than DPV and using the area under peak for univariate calibration purposes was more suitable than height of peak. Adsorption at the electrode surface is an important trouble which affects the height and position of voltammetric peaks, but the area under peak is not affected by adsorption therefore, it can be more suitable for univariate calibration purposes. The biosensor response was also calibrated by chronoamperometry and the results confirmed that the HYDPV was more sensitive than chronoamperometry. The next attempt was based on recording the biosensor responses based on second-order HYDPV data and modeling of them (whole of vectors) by three-way calibration methods which showed the best performance among the tested methods for determination of CHO. The biosensor response was long-term stable, repeatable and reproducible which was successfully applied to the analysis of serum sample towards determination of CHO whose results were comparable with a reference method.