Construction And Application Of Prussian Blue Nanozyme

Nanozymes are artificial enzyme mimics that have unique properties of nanomaterials and at the same time have catalytic activity.Nanozymes have attracted great research interest in the past decade or so due to their significant advantages over traditional biological enzymes.They are not only cheap to prepare,easy to store,and stable,but also have good catalytic activity,which makes nanozymes widely used in the fields of antibacterial,biosensing,and anti-tumor therapy applications.So far,various nanomaterials such as noble metal nanoparticles,metal oxides,carbon-based nanomaterials and metal-organic frameworks have been used as potential nanozymes.Among them,Prussian Blue（PB）has attracted extensive research interest because of its high peroxidase-like catalytic activity due to its mixed valence state(Fe²⁺,Fe³⁺)similar to that of Fe atoms in Fe₃O₄.However,the poor stability and easy aggregation of single Prussian blue nanoparticles,coupled with the harsh purification conditions in the synthesis process,make it difficult to be applied to colorimetric sensing.Therefore,this thesis focuses on improving the above problems by designing and preparing Prussian blue-based enzyme nanocomposites and conducting preliminary investigations in GSH colorimetric detection and tumor therapy by:（1）A silica-based Prussian blue nanocomposite（mSiO₂@PB）with（3-aminopropyl）triethoxysilane（APTES）-modified mesoporous silica spheres（mSiO₂）as the core carrier was synthesized using a simple and convenient precipitation method with a simple,easy-to-operate and stable reproducibility scheme.The synthesized mSiO₂@PB nanocomposites were characterized by transmission electron microscopy（TEM）,scanning electron microscopy（SEM）,energy spectrometry（EDS）,UV absorption,ZETA potential,X-ray diffraction（XRD）,and X-ray photoelectron spectroscopy（XPS）,and the stability of the synthesized mSiO₂@PB nanocomposites was investigated in multiple aspects.The final mSiO₂@PB nanocomposites were uniformly distributed and sized with an average diameter of 135 nm.mSiO₂@PB nanocomposites also showed excellent performance in terms of operational stability of the synthesis method,dispersion stability in solution and storage stability of the material.（2）Based on the above findings,the peroxidase-like activity of mSiO₂@PB was investigated.The catalytic activity of mSiO₂@PB was investigated with 3,3’,5,5’-tetramethylbenzidine（TMB）as the substrate,and the optimal catalytic reaction conditions（p H,temperature,H₂O₂ concentration）were confirmed.Meanwhile,the enzymatic kinetic performance of mSiO₂@PB was further investigated by combining the Mie equation with TMB and H₂O₂ as substrates,and the Mie constant（K_m）and the maximum reaction rate(V_max)of mSiO₂@PB were calculated.Using the principle that mSiO₂@PB nanozyme can trigger the oxidation of TMB for color development in the presence of H₂O₂ and GSH can inhibit the oxidation of TMB,a visual colorimetric GSH biosensing platform was constructed for the detection of GSH in the range of 0.5～30μM with a detection limit of 0.15μM.The platform has excellent sensitivity and relatively low detection limit,and has been used in the detection of GSH.The platform has excellent sensitivity and relatively low detection limits,and has been validated for the detection of GSH in actual samples of human physiological fluids（saliva,urine）.In addition,a portable colorimetric method for the semi-quantitative determination of GSH was proposed by combining the platform with modern intelligent technology using a smartphone as a detector.Combined with the advantage that mSiO₂@PB nanozyme-catalyzed substrates can be highly sensitive for color development,this smartphone assay is expected to be further extended to clinical and daily life testing.（3）Based on the broad absorption of mSiO₂@PB in the near-infrared region,this thesis continues to investigate the photothermal properties of mSiO₂@PB.With the increase of mass concentration of mSiO₂@PB and the increase of laser power density,the photothermal warming effect of mSiO₂@PB was gradually obvious,in which the mass concentration of 0.8 mg/mL increased the temperature from room temperature to about 72°C under 3 min of irradiation.And the photothermal performance of mSiO₂@PB aqueous solution irradiated by 1.5 W/cm²,808 nm laser for 4 times is almost the same,and the photothermal conversion efficiency of the material is 69.3%.In addition,the results of photothermal therapy at the cellular level showed that 120μg/mL mSiO₂@PB could kill more than 70%of the tumor cells after 3 min of 1.5W/cm²,808 nm laser irradiation.The above results show that mSiO₂@PB has excellent photothermal effect,photothermal stability and high photothermal conversion efficiency,and can be used as a candidate material for photothermal therapy of tumors.