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

Abstract This study reports a sensitive and selective colorimetric approach for the analysis of dopamine (DA) based on CeO 2 @ZIF‐8/Cu‐CDs laccase‐like nanozymes activity. The CeO 2 @ZIF‐8/Cu‐CDs was synthesized using cerium oxide (CeO 2 ) and copper‐doped carbon dots (Cu‐CDs) with 2‐methylimidazole by a facilely hydrothermal approach. The CeO 2 @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 CeO 2 @ZIF‐8/Cu‐CDs are 0.20 mM and 1.48 μM/min, respectively. The detection method has a linear range of 0.05–7.5 μg/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.