Research On The Design And Synthesis Of Nanoenzymes Based On Porous Organic Framework Compounds And Their Application In Colorimetric Sensing

Nanozymes?nanomaterials with enzyme-like catalytic properties?have been widely used in colorimetric sensing,environmental protection,disease diagnosis and treatment due to its easy preparation,good stability and high catalytic efficiency.In recent years,porous organic framework compounds?such as MOFs and COFs?have been applied in the construction of nanozymes,which have attracted great attention for their excellent performance and become an important topic in the research field of nanozymes.However,metal-organic frameworks?MOFs?as nanozymes still face some problems that need to be solved urgently,such as low catalytic activity and poor substrate recognition specificity.In addition,the research on covalent organic frameworks?COFs?as nanozymes is still in its infancy.Based on these,novel nanozymes based on porous organic framework compounds were designed and synthesized by means of post-synthesis and biomimetic mineralization,and their application in colorimetric sensing was studied.The main contents are as follows:1.In this work,the Fe-porphyrin-based covalent organic framework?Fe-COF?has been successfully synthesized through a facile postsynthetic strategy.In the presence of hydrogen peroxide?H₂O₂?,the Fe-COF can catalyze a chromogenic substrate?3,3?,5,5?-tetramethylbenzidine?TMB??to produce color,and this just goes to show that it has an inner peroxidase-like activity.Moreover,the kinetic studies indicate that the Fe-COF nanomaterial has a higher affinity toward both the substrate H₂O₂ and TMB than the natural enzyme,horseradish peroxidase?HRP?.Under the optimized conditions,the Fe-COF nanomaterial was applied in a colorimetric sensor for the sensitive detection of H₂O₂.The detection range was from 7 to 500?M,and the detection limit was 1.1?M.Furthermore,the combination of the Fe-COF with glucose oxidase?GOx?can be implemented to measure glucose by a one-pot method,and the obtained detection range was from 5 to 350?M;the detection limit was 1.0?M.It was proved that the sensor can be successfully used to detect the concentration of glucose in human serum samples.As a peroxidase mimic,the Fe-COF exhibits the advantages of easy preparation,good stability,and ultrahigh catalytic efficiency.We believed that the proposed method in this work would facilitate the applications of COFs-based composites as enzymatic mimics in biomedical fields.2.An iron-nickel bimetallic metal-organic framework?FeNi-MOF?with inner peroxidase-like activity as a support for enzyme immobilization was synthesized.And the GOx-mediated synthesis of mimic multienzyme system?GOx/FeNi-MOF?was obtained by a one-step biomimetic mineralization.FeNi-MOF played a dual role of a peroxidase mimic and a protective coating.Therefore,the obtained multienzyme system showed both peroxidase-like activity of FeNi-MOF and the biological activity of natural enzyme.FeNi-MOF acted as a peroxidase mimic,showing a higher affinity for H₂O₂.The enhanced catalytic activity of the FeNi-MOF may result from synergistic effect between iron and nickel.In addition,the GOx/FeNi-MOF was selected as a proof of concept and succeeded in a one-step colorimetric detection of glucose by tandem catalysis.3.In this work,we develop a new and facile method for synthesis of a sub-100nm peroxidase-mimicking zirconium porphyrin metal-organic framework?Zr-Por MOF?by solvothermal method.The experimental results indicated that compared with the micron-sized crystals obtained by the classical synthesis method,the catalytic property,stability and dispersity in the water of the colloidal Zr-Por MOF were enhanced obviously.The as-synthesized colloidal Zr-Por MOF was further successfully applied in colorimetric H₂O₂ detection and satisfying detection performance was obtained.Furthermore,the colloidal Zr-Por MOF was also successfully employed in constructing a peroxidase-based tandem catalysis system.Taking the glucose oxidase as an example,this system has successfully applied for glucose sensing in real human serum samples,which proved its practical feasibility in diabetes diagnosis and indicated its high potential feasibility in peroxidase related applications in complex biomatrix.