High-activity Mo, S co-doped carbon quantum dots nanozyme-based cascade colorimetric biosensor for sensitive detection of cholesterol
Nanozymes have drawn considerable attention because of their lower cost, higher stability and convenient preparation than protein enzymes. In the present work, the Mo, S co-doped carbon quantum dots (Mo-CQDs) as a peroxidase mimic were used to fabricate the cascade colorimetric biosensor to detect cholesterol. The Mo-CQDs possess a robust peroxidase-like activity, which can easily catalyze 3,3,5,5-tetramethylbenzidine (TMB) to produce an oxidized TMB in the presence of H2O2. The Mo, S doping in the carbon quantum dots (CQDs) notably boost the yield of CQDs and may facilitate the electron transfer between TMB and H2O2, which further enhance the catalytic activity of CQDs. The colorimetric biosensor based on Mo-CQDs and cholesterol oxidase exhibited excellent selectivity and high sensitivity for cholesterol in the range of 0.01-1.0 mM along with the detection limit as low as 7 μM. The total cholesterol concentration in serum sample was measured with satisfactory results and read out by naked eye, indicating the potential application in clinical diagnosis and portable test kit.