Colorimetric And Fluorescent Dual-channel Detection Of H₂O₂ And Its H₂O₂-metabolites Based On Nanozymes

Nanozymes are a class of nanomaterials with enzymatic activity.As a substitute for natural enzymes,nanozymes have great potential applications in biosensors and biomedicine due to their high stability and low cost.Since H₂O₂ is an indispensable substance in living organisms,there are many methods for H₂O₂ detecting based on nanozymes,such as electrochemical methods,chemiluminescence methods,fluorescence methods,UV-vis methods and so on.However,most of these methods are based on the single signal readout mode.Because single-signal readout mode is susceptible to external interference,making it difficult to meet accurate measurement requirements.In this paper,bifunctional carbon dot nanozymes with peroxidase activity and fluorescence property was prepared by a simple method.Benefit from their peroxidase activity and fluorescence property,H₂O₂ and metabolites?such as glucose,jaundice,and cholesterol?could be quickly and efficiently detected by colorimetric and fluorescent double readout methods.The details are as follows:?1?Carbon dots?CDs?was prepared by a modified solvothermal method,and then hemin@CDs was synthesized as a bifunctional nanozyme by introduction of hemin on the surface of the CDs.Based on the peroxidase activity and fluorescence property of hemin@CDs,a colorimetric and fluorescent double readout analysis method for detecting H₂O₂ and H₂O₂-related metabolites?glucose and xanthine?was established.The detection mechanism is that hemin@CDs could catalyze the oxidative coupling reaction of4-aminoantipyrine?4-AAP?with phenol to form quinone imine dye?red product?in the presence of H₂O₂,which can be applied to the colorimetric detection of H₂O₂ and H₂O₂-related metabolites.The synergistic effect of the dynamic quenching of hemin@CDs and H₂O₂,and the inner filter effect of?IFE?of hemin@CDs and red quinone can be used for fluorescence detection of H₂O₂ and H₂O₂-related metabolites.The dual-signal readout method has high sensitivity and selectivity for H₂O₂ and its metabolites?glucose and xanthine?with detection limits of 0.16 and 0.11?M,respectively.When it was applied for glucose in human serum samples,the recovery results are satisfactory.This indicates that the carbon dots is a very promising material for practical application..?2?Co-doped carbon dots?Co-CDs?were prepared by coprecipitation and followed calcination process.As a novel bifunctional nanozymes,the colorimetric and fluorescent double readout method for the detection of H₂O₂ and related metabolites?xanthine and cholesterol?was established using Co-CDs with peroxidase activity and fluorescence properties.The detection mechanism is that Co-CDs could catalyze oxidation of o-phenylenediamine?OPD?in the presence of H₂O₂ formed an oxidized OPD?oxOPD,yellow product?for colorimetric detection of H₂O₂ and related metabolites.Based on the IFE of Co-CDs and oxOPD,fluorescence detection of H₂O₂ and related metabolites can be implemented.The dual readout method has high sensitivity and selectivity for H₂O₂ and related metabolites?xanthine and cholesterol?with detection limits up to 0.15 and 0.14?M,respectively.When used for xanthine and cholesterol in human serum samples,the detection and recovery results were satisfactory.Co-CDs nanozymes have been shown to enable tracking of H₂O₂ in living cells,and to achieve high selective detection of H₂O₂ in vivo.