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 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 (Km) and the maximal velocity (Vmax) of CeO2@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.