Design And Analytical Application Of Novel Oxidase Mimics Based On The Ferroelectric Catalytic Effect Of BaTiO₃ Nanoparticles

Since the first report in 2007,nanozymes attracted more and more attention for their high stability against harsh conditions and excellent and tunable catalytical activities.Among nanozymes,peroxidase mimics require unstable and destructive H₂O₂ while oxidase mimics require dissolved oxygen.Without H₂O₂ or dissolved oxygen,their activity will decrease significantly.Therefore,new nanozymes are needed to overcome these problems.The oxidase-mimicking activity of ferroelectric BaTiO₃ nanoparticles（BTO NPs）is reported.In the absence of hydrogen peroxide or oxygen,BTO NPs catalyzed the oxidation of 3,3’,5,5’-tetramethylbenzidine（TMB）and other chromogenic substrates.The catalysis constant was eight times that of fluorescein and 10⁴ times that of bovine serum albumin-protected Se nanozymes.In the mechanism of the chromogenic reaction catalyzed by BTO NPs,the intrinsic electric field of the ferroelectric BTO drove the separation of holes and electrons,and the separated carriers reacted with water to produce reactive oxygen species that oxidized the chromogenic substrates.Our research team used the ferroelectric effect of BTO as an oxidase mimic to study the activity of BTO mimic enzymes.This work not only proposed a new idea of screening and designing nanozymes from ferroelectric materials but also expand the application of ferroelectric nanomaterials to bio-detection.The specific work contents are as follows:（1）Based on the oxidase mimic activity of BTO NPs itself,a simple and effective,direct colorimetric analysis method for BTO NPs detection of GSH was established.3,3’,5,5’-tetramethylbenzidine（TMB）was selected as the chromogenic substrate to study the oxidase mimic activity of BTO NPs.Under the optimal reaction conditions,BTO catalyzed the production of reactive oxygen from oxygen or water molecules,and the reactive oxygen oxidized the colorless TMB to a blue product ox TMB with a characteristic absorption peak at 652 nm.BTO NPs and TMB chromogenic system is used to detect GSH for GSH restores blue oxidized TMB to a colorless TMB.The dynamic range of GSH was 0.50-20μmol/L,and the detection limit（LOD）was 0.2μmol/L.Moreover,this analytical method has been successfully applied to detect GSH in fetal bovine serum.Based on the ferroelectric effect,BTO NPs oxidase mimic enzyme has high catalytic activity.The ferroelectric catalytic performance can be tuned by changing the shape,size and composition of nanoparticles,thus promoting the development of nanoenzymes.（2）Ascorbic acid（AA,vitamin C）is an important antioxidant that can effectively protect the body from harmful substances.Different levels of AA can be used not only to measure the level exactitude of oxidative stress in human metabolism,but also as evidence for the prevention and treatment of neurodegenerative diseases and mental disorders.Acid phosphatase（ACP）is an important enzyme that maintains lysosomal metabolism in organisms.ACP is considered to be a biomarker of some diseases,so it is important to develop a convenient and sensitive method to detect ACP in diagnosis and drug screening.In this chapter,a colorimetric method for the determination of AA concentration and ACP activity was established based on the oxidase-mimicking activity of BTO nanoparticles.The linear range of AA detection is 1.0-20μmol/L,and the detection limit is 0.50μmol/L.The linear range of ACP detection is 0.04-1.0 m U/m L,and the detection limit is 0.02 m U/m L.This method not only realizes the detection of AA and ACP through simple and effective strategies,but also broadens the application of ferroelectric nanomaterials in biological detection.