Highly sensitive cholesterol biosensor based on electron mediator thionine and cubic-shaped Cu2O nanomaterials

The preparation of an electrochemical biosensor applicable for the highly sensitive detection of cholesterol content in biological samples in clinical practice is studied in this paper. Commonly used in biosensors, nanocuprous oxide (Cu2O) contains active electron-hole pairs and a large specific surface area, while thionine (TH) improves the efficiency of electron transfer between the enzyme and the electrode. In this study, a cholesterol biosensor, cholesterol oxidase (ChOx)/thionine/nano-cuprous oxide/ glassy carbon electrode (GCE) (ChOx/TH/ Cu2O/GCE), is prepared using cubic-shaped Cu2O as the nanomaterial, TH as an electron mediator, and chitosan (CS) as a cross-linking agent to immobilize cholesterol oxidase. The results show that Cu2O nanoparticles (NPs) are successfully synthesized, and the cholesterol biosensor prepared from synthesized Cu2O NPs exhibits excellent electrochemical characteristics, good linearity (R2 = 0.997) over a substrate concentration range of 10 to 1000 mu M, a sensitivity of 70.22 mu A mu M-1 cm-2, and a low detection limit of 0.0018 mu M for the substrate. The ChOx, which immobilizes on the composite electrode, shows a strong affinity for cholesterol due to its low Michaelis-Menten constant (Km) value (25.359 mu M). Moreover, with strong anti-interference, good reproducibility, and stability, the cholesterol biosensor can achieve a recovery rate of 99.71 % to 107.75 % according to a recovery test of actual spiked samples. Thus, the prepared nanomaterial-based cholesterol biosensor can be applied to the highly sensitive detection of cholesterol in actual biological samples.