A colorimetric detection of dopamine in urine and serum based on the CeO2@ZIF-8/Cu-CDs laccase-like nanozyme activity

This study reports a sensitive and selective colorimetric approach for the analysis of dopamine (DA) based on CeO2@ZIF-8/Cu-CDs laccase-like nanozymes activity. The CeO2@ZIF-8/Cu-CDs was synthesized using cerium oxide (CeO2) and copper-doped carbon dots (Cu-CDs) with 2-methylimidazole by a facilely hydrothermal approach. The CeO2@ZIF-8/Cu-CDs exhibited excellent laccase-like nanozymes activity and can oxidize the colorless substrate (DA) to red product with 4-aminoantipyrine as the chromogenic agent. The Michaelis-Menten constant (K-m) and the maximal velocity (V-max) of CeO2@ZIF-8/Cu-CDs are 0.20 mM and 1.48 mu M/min, respectively. The detection method has a linear range of 0.05-7.5 mu g/mL and a detection limit as low as 8.5 ng/mL with good reproducibility. The developed colorimetric sensor was applied to rapid and precise quantitative evaluation of DA levels in serum and urine samples. This study presents a new approach for detecting biological molecules by utilizing the controlled regulation of nanozymes' laccase-like activity.