Construction Of Prussian Blue-based Nanozyme For Biosensing And Multimodal Tumor Therapy

Nanozymes,as a kind of synthetic nanomaterials with simulated natural enzyme activity,have attracted increasing attention due to the adjustable catalytic activity,multienzyme-like activity and high stability.Relying on the reactive oxide species produced by the catalysis of small biological molecules,nanozymes can realize the visual detection of biological molecules and the chemokinetic treatment of diseases.Therefore,the construction of nanozymes with high catalytic activity and multifunctional characteristics is of great significance for biological application research.As a face-centered cubic metal-organic frameworks formed by alternately connecting Fe^Ⅱand Fe^Ⅲwith cyanide ligands,Prussian blue nanoparticles（PBNPs）possess catalysis activity,good biocompatibility,structural controllability and excellent photothermal conversion property.At present,studies on PBNPs mainly focused on their drug-loading and photothermal properties.The research on the catalytic mechanism and versatility of PBNPs is an effective means to promote the development of PBNPs.Based on the enzyme-like activity of PBNPs,this paper studies the mechanism of the enzyme like activity,the molecular detection in vitro and multi-functional coordinated tumor treatment in vivo.The main research contents are as follows:（1）The enzyme-like activity of PBNPs was studied,a series of PBAs were synthesized by replacing Fe atoms in PBNPs with Cr,Co,Cu,Mn,and Zn atoms.The PBNPs showed the highest maximal reaction rate(0.378μM·s^-1)by comparing their peroxidase-like activity,indicating that the peroxidase-like activity of PBNPs could be attributed to Fe N_x（x=4-6）unit.Meanwhile,the PBNPs with Fe（Ⅲ）-C≡N-Fe（Ⅱ）structure showed higher maximal reaction rate than that of PBNPs with Fe（Ⅱ）-C≡N-Fe（Ⅲ）structure,demonstrating that the Fe^ⅡN_xunit was the main catalytic active site of PBNPs.Especially,the PBNPs（Fe（Ⅲ）-C≡N-Fe（Ⅱ））and H₂O₂system exhibited much higher oxidizability than·OH generated from the Fenton reaction,which further implied that the Fe^ⅡN_xunit is the key to the excellent catalytic activity of PBNPs.In addition,the PBNPs with Fe（Ⅲ）-C≡N-Fe（Ⅱ）structure also showed the highest catalase-like activity.（2）In order to enhance the catalytic activity of PBNPs and endow them versatility,carbon dots/Prussian blue nanoparticles（CDs/PBNPs）were prepared by a two-step method.The improvement of the catalytic effect of PBNPs in the complex is achieved in two ways.Firstly,carbon dots（CDs）and PBNPs can accelerate electron transfer through the formation of heterojunction and thus improve the peroxidase-like activity of PBNPs.Then,the photothermal effect of PBNPs can also improve the catalytic activity.In addition,Fe³⁺could quench the fluorescence of CDs,and thus CDs could be used as a fluorescent probe to detect Fe³⁺.Based on the above characteristics of CDs/PBNPs,this chapter constructed a visual probe with colorimetric and fluorescent dual-visual probe,which could simultaneously detect the concentration of Fe³⁺and cholesterol in serum samples.（3）Due to the catalytic activity,PBNPs can not only be used for biological detection,but also for tumor chemodynamic therapy.However,the complex tumor microenvironment reduced the effect of chemokinetic therapy.To efficiently improve the production of reactive oxygen species induced by nanozymes and realize the destruction of tumor cells,this chapter constructed a composite material loaded with glucose oxidase and Rose Bengal（RB）based on PBNPs.Glucose oxidase could catalyze the decomposition of excess glucose in the tumor microenvironment into gluconic acid and H₂O₂,thereby cutting off the nutritional supply of tumor tissue and realizing starvation therapy.On the one hand,PMGR with peroxide-like activity could convert H₂O₂into reactive oxygen species,enhancing the effect of chemodynamic therapy.On the other hand,PMGR could also accelerate the decomposition of H₂O₂to produce O₂.Rose Bengal could effectively convert the generated O₂into¹O₂under 540 nm laser irradiation,enhancing photodynamic therapy.Based on this,the PBNPs-based nanocomposites realized photoacoustic imaging-guided tumor chemodynamics,photothermal and photodynamic synergistic therapy.This work provided a new opportunity to explore multiple synergistic treatment modalities for tumor.