Colorimetric evaluation of the hydroxyl radical scavenging ability of antioxidants using carbon-confined CoOx as a highly active peroxidase mimic
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The authors present a colorimetric method for the evaluation of the hydroxyl radical scavenging capability of antioxidants by exploiting carbon-confined mixed cobalt oxide nanoparticles (denoted as C-confined CoOx NPs) as a novel peroxidase mimic. The nanozyme can be prepared from the metal-organic framework ZIF-67 by calcination at a moderate temperature. It exhibits peroxidase-mimicking activity and catalyzes the oxidation of colorless 3,3′,5,5′-tetramethylbenzidine (TMB) to form a blue product in the presence of H2O2 via generation of hydroxyl radicals. However, in the presence of an antioxidant, the color reaction is suppressed due to scavenging of hydroxyl radicals by the antioxidant. Based on this principle, the hydroxy radical scavenging ability of glutathione (GSH), cysteine (Cys), tannic acid (TA) and tea polyphenols (TP) was assessed. It was found that these antioxidants can scavenge hydroxyl radicals in the following decreasing order: TA>Cys>GSH>TP. The assay was also used to quantify the antioxidative power of common fruit extracts.
KeywordsNanozyme Co-based materials ROS Colorimetric detection Hydroxyl radicals Antioxidant activity POx Fruit extracts
The authors appreciated the supports from the National Natural Science Foundation of China (Nos. 21605061 and 31601549), the Natural Science Foundation of Jiangsu Province (No. BK20160489), the Open Fund from the Shanghai Key Laboratory of Functional Materials Chemistry (No. SKLFMC201601), the Open Fund from the State Key Laboratory of Bioreactor University, and the Postgraduate Research & Practice Innovation Program of Jiangsu Province (No. KYCX18_2341).
Compliance with ethical standards
The author(s) declare that they have no competing interests.
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- 33.The natural HRP (100 mg, 300 U/mg) purchased from Shanghai Macklin biochemical co., ltd. costs ~$70, so the cost of the natural HRP is ~$2.5 per kU. The commercial prices of the co(NO3)2·6H2O (100 g) and 2-MI (100 g) precursors are ~$20 and ~$10, respectively. After considering the cost of other reagents including PVP, the cost of all raw materials is calculated to be ~$35 to obtain 25 g C-confined CoOx NPs. Taking ~$30 as the cost for the preparation of C-confined CoOx NPs, the total cost of 25 g C-confined CoOx NPs is determined to be ~$65. According to the k cat value, the enzymatic activity of C-confined CoOx NPs is estimated to be about 20 U/mg. So, the cost of the C-confined CoOx NPs nanozyme is ~$0.13 per kU, which is much lower than that of natural HRP (~$2.5 per kU)Google Scholar