Study On Preparation And Enzyme-like Activities Of Amorphous Manganese Oxide-containing Nanozyme

Manganese is an necessary trace element for the human body.It is also an essential element involved in many cell processes,including lipid,protein and carbohydrate metabolism,and affects various physiological and life activities of people.In addition,manganese ions also play an important role in biological processes due to their redox and magnetic properties.Due to its unique structural flexibility and abundant defect sites,amorphous substances have become a research hotspot in the field of catalysis in recent years.Among them,amorphous oxides containing manganese in mixed valence states have been proven to have extremely excellent catalytic activity.Compared with traditional cancer treatment methods,chemodynamic therapy（CDT）and photothermal therapy（PTT）are both a new type of treatment.They have the advantages of low side effects,less trauma and low cost,and have recently attracted more and more attention.At the same time,the detection of cancer cells is a more challenging and urgent topic for scientists.Preliminary detection of cancer cells is sensitive to make early diagnosis of cancer and continuous monitoring of cancer treatment possible.Unfortunately,most of the existing clinical techniques have the disadvantages of low sensitivity and inability to detect cancer cells at an early stage.In this article,using Mn（CO₃）as the precursor,calcination and surface modification of polydopamine（PDA）were used to prepare amorphous mixed-valent Mn-containing nanozyme amv Mn-300-x（where 300 represents the calcination temperature,x represents the calcination time）and Mn（CO₃）@PDA with a core-shell structure.Researched its mimic enzyme activities and explored their application in tumor cell specific recognition and tumor CDT and PTT treatment.The specific content is as follows:1.Research on the preparation,performance and application of amv Mn-300-x in tumor cell recognition and treatment.First,the precursor Mn（CO₃）nanoparticles were prepared by solvothermal method,and then calcined in an air atmosphere at 300°C for a certain period of time,the calcining time was recorded as x.Thus,amv Mn-300-x nanoparticles with a morphology similar to cocklebur were prepared.Subsequently,the mimic enzyme activity of amv Mn-300-x was studied,and the tetramethylbenzidine（TMB）color method and the hydrogen peroxide production test method proved that amv Mn-300-x has a dual mimic enzyme of oxidase and catalase.The activity of the two enzymes is dependent on the p H of the reaction system.Under the condition of p H=3.4-5.4,the mimic activity of peroxidase is more obvious,and under the condition of p H greater than 6.4,the mimic activity of catalase is more significant.Based on the characteristic that cancer cells have a large number of micro-nano filopodia,the specific adhesion of cocklebur-like Mn（CO₃）and amv Mn-300-15 to cancer cells is achieved.Using the oxidase mimic activity of amv Mn-300-15,under the condition of external TMB,the specific colorimetric recognition of tumor cells is realized.Using the human cervical cancer（He La）cell line as the cell model,amv Mn-300-15-mediated tumor chemodynamic therapy in vitro was explored.2.Research on the preparation,performance and application of Mn（CO₃）@PDA in tumor photothermal therapy.Based on the precursor Mn（CO₃）nanoparticles prepared by the solvothermal method,a layer of polydopamine（PDA）polymer layer was successfully coated on the surface to prepare Mn（CO₃）@PDA nanoparticles with a core-shell structure.The photothermal properties of Mn（CO₃）@PDA nanoparticles were studied,and it was found that Mn（CO₃）@PDA nanoparticles can absorb the energy of 808 nm photons and convert it into heat energy.In addition,Mn（CO₃）@PDA also retains the ability of Mn（CO₃）to specifically recognize cancer cells.Using its photothermal properties,preliminary exploration of the material’s in vitro photothermal killing of He La cells has been conducted.The results show that the in vitro photothermal therapy mediated by Mn（CO₃）@PDA has a certain inhibitory effect on the proliferation of He La cells.