Synthesis of β-cyclodextrin grafted rhombohedral-CuO antioxidant nanozyme for detection of dopamine and hexavalent chromium through off–on strategy of peroxidase mimicking activity

Abstract

For the last few decades, peroxidase mimicking inorganic nanoparticles are widely used as compared to natural peroxidase due to some basic advantages especially high durability, stability in harsh conditions, easy and cost-effective synthesis, and easy storage. However, most of these peroxidase mimicking nanoparticles are not always effective in a neutral medium, most of the show high activity in an acidic medium which seriously impedes their uses in bioanalytical applications. In the current study, we have developed an inorganic β-cyclodextrin (β-CD) grafted rhombohedral cupric oxide (R-CuO) nanozyme which showed high catalytic activity at neutral conditions (pH = 7) and also exhibited catalytic activity in a wide range of pH with enzymatic substrate TMB (3,3–5,5 tetramethylbenzidine).The current nanozyme has exhibited outstanding peroxidase mimic activity with low Km and very high Vmax value which was calculated by the double reciprocal Lineweaver Burk plot. Considering the R-CuO NPs as a heterogeneous catalyst, a one-pot simple colorimetric system has been developed for dopamine detection, as dopamine turns off the catalytic activity of the R-CuO NPs-TMB peroxidase system. The sensitivity of this current probe to dopamine was promising with a linear range of 2– 24 µM and had a low detection limit of 1.91 µM. More surprisingly, the R-CuO-TMB /dopamine system undergoes recovery of peroxidase activity upon introduction of Cr (+6) (dichromate).The method displays a good selectivity towards Cr (+6) (dichromate) over all the other metal ions with a wide linear relationship in the range of 2 μM–10 μM, and a low detection limit of 0.47 μM. Moreover, the present Nano system was not only applicable for toxic metal and bioactive molecules detection they also used as a ROS scavenger. Our Nano system exhibited scavenging activity for OH radical, O2–. species and metal chelation activity which was investigated calorimetrically. So, the present Nano system is used as a colorimetric probe for dopamine and Cr (+6) (dichromate) detection and consumption of reactive oxygen species as well.