Design And Synthesis Of Fe/Cu Based Nanozymes For Optical Sensing Analysis

Natural enzyme is a kind of biocatalyst produced by cells in vivo,which has the characteristics of high catalytic efficiency,specificity and mild action conditions.Inspired by the catalysis of natural enzymes,various enzyme analogues have been developed to"take the advantage of natural enzymes and avoid the shortcoming of them".Over the past few decades,researchers have designed and constructed a variety of highly stable,low-cost artificial analogues that can replace natural enzymes and be widely used in many fields.To date,"artificial enzymes"have become a very important and exciting branch of biomimetic chemistry.Recently,the integration of nanotechnology and biology has greatly stimulated the interest of researchers in designing and constructing functional nanomaterials with enzymatic properties.The nanomaterials with enzyme activity are commonly referred to as nanozymes.However,with the development of research,some problems of limiting the further application of nanozymes need to be solved urgently.At present,nanozymes generally have the disadvantages of low catalytic activity and poor specificity,which limits the application of nanozymes to some extent.Furthermore,the unique physical and chemical properties of nanomaterials not only endow nanozymes with various functions,but also realize various designs and wide applications.Therefore,improving the catalytic activity,specificity and expanding the practical application of nanozymes are the research hotspots in the field of nanozyme.In this paper,different Fe/Cu-based nanozymes were designed and synthesized,and the corresponding optical sensing analysis system was constructed.The main contents are as follows:1.A novel colorimetric sensor based on nanozyme with magnetic separation was constructed to can detect metabolites in near neutral conditions.Magnetic Cu/Fe₃O₄@Fe OOH with oxygen vacancies was prepared by self-assembly hydrothermal method,and the material was characterized by different methods.The oxygen vacancies generated by the binding of Cu²⁺to the Fe₃O₄@Fe OOH structure has been proved to be an important reaction site for the enhancement of catalytic activity.Owing to its inherent peroxidase-like activity that can catalytic decomposition of H₂O₂ to oxidize 3,3',5,5'-tetramethylbenzidine(TMB)for signals,a simple selective enzyme-based colorimetric sensor was developed for one-step detection of H₂O₂ and cholesterol.2.Copper(II)-based metal organic frameworks(NH₂-Cu-MOF)with dual functions of blue fluorescence and peroxidase-like activity were synthesized by simple hydrothermal method.NH₂-Cu-MOF with peroxidase-like activity can catalyze the decomposition of H₂O₂ to oxidize o-phenylenediamine(OPD)into 2,3-diaminophenazine(DAP)with yellow fluorescence,and the energy of NH₂-Cu-MOF(429 nm)can be transferred to DAP(549 nm)by fluorescence resonance energy transfer(FRET).In the presence of PPi,the catalytic activity of NH₂-Cu-MOF is greatly inhibited due to the strong binding ability of Cu²⁺and PPi.However,after incubation with PPase,PPi is hydrolyzed to orthophosphate(Pi)with low affinity for Cu²⁺,and the peroxidase-like activity of NH₂-Cu-MOF is restored,resulting in a ratio fluorescence signal depending on the level of PPase.Based on the different ratios of fluorescent signals induced by PPi and PPase,a quantitative analysis method of PPase activity was constructed.3.Cu-MOF-74 was synthesized by a simple hydrothermal method using copper nitrate as metal node and 2,5-dihydroxyterephthalic acid as bridging ligand.Cu-MOF-74 acts as a peroxidase mimic to induce the formation of^·OH by catalyzing the decomposition of H₂O₂,and^·OH can oxidize the two hydroxyl groups of bridging ligand 2,5-dihydroxyterephthalic acid into carbonyl groups.During the process of excitation,electrons are transferred to the electron-deficient carbonyl groups,which quenche the yellow-green fluorescence of Cu-MOF-74.A simple,visual,label-free fluorescence sensor for H₂O₂ detection was developed using dual-function Cu-MOF-74 as mimic enzyme and fluorescent probe.