Colorimetric Detection of Dopamine Based on Peroxidase-Like Activity of β-CD Functionalized AuNPs

Catalytically active nanomaterials, or nanozymes, have gained significant attention as alternatives to natural enzymes due to their low cost, ease of preparation, and enhanced stability. Because of easy preparation, excellent biocompatibility, and unique optoelectronic properties, gold nanoparticles (AuNPs) have attracted increasing attention in many fields, including nanozymes. In this work, we demonstrated the applicability of β-CD-AuNPs as enzyme mimics for different substances, including TMB and DA. We found that β-CD-AuNPs can catalyze the H2O2-mediated oxidation of DA. The dopamine signal-off sensor was developed by taking advantage of the peroxidase-like activity of β-CD-AuNPs towards TMB and DA, where both TMB and DA may compete for the binding sites with β-CD-AuNPs. As a result, the presence of dopamine can be detected even through the naked eye (up to a concentration of 3.75 µM) and using a spectrophotometer (up to a concentration of 1.0 µM) by monitoring the disappearance of the blue color of the oxidized form of TMB in the presence of dopamine. Furthermore, dopamine can also be detected in equal concentrations of common interferences, including ascorbic acid and uric acid. Given the versatility of cyclodextrin to host large number of analyte molecules, we envision the similar principle can be applied for the detection of other analyte molecules of biological, medical and environmental significance.