Enhanced Electrocatalytic Properties of Co₃O₄ Nanocrystals Derived from Hydrolyzed Polyethyleneimines in Water/Ethanol Solvents for Electrochemical Detection of Cholesterol

The present study describes the effect of hydrolysis of polyethyleneimines in water/ethanol mixture on the morphology of the cobalt oxide (Co3O4), used as the main sensor component. The structure of the generated Co3O4 nanocrystals is consistent with a well-defined cubic phase crystallography, having only cobalt and oxygen elements. Developing simple, low-cost, sensitive, and selective cholesterol biosensors is essential for accurate monitoring of cholesterol to avoid cardiovascular diseases. These nanocrystals exhibit large surfaces suitable for facile and high loading of cholesterol oxidase enzyme through the physical adsorption method. Then, the fabricated cholesterol oxidase/ Co3O4 nanocrystals composite was implemented for potentiometric detection of cholesterol in 10 mM phosphate buffer of pH 7.3. Importantly, the presented cholesterol biosensor revealed a wide linear range of 0.005 mM to 3.0 mM with a limit of detection (LOD) of 0.001 mM. Additionally, the sensitivity of biosensor was estimated around 60 mVdec−1. The selectivity, stability, reproducibility, and repeatability were also observed as satisfactory. The dynamic response of the proposed method demonstrated a fast response time of less than 1 s. Furthermore, the successive addition method confirmed a remarkably stable response towards various cholesterol concentrations. Thus, the developed cholesterol oxidase/ Co3O4 nanocomposite may be used as an efficient alternative method to monitor low cholesterol concentrations form real samples.