Preparation Of Functionalized Mo-based Nanomaterials And Research Anti-tumor Performance

With the rapid development of modern technology and industry,cancer has become one of the serious diseases in today’s society,so the development of highly effective anti-cancer strategies is imminent.The current clinical anti-cancer strategies mainly include:surgery,chemotherapy,and radiotherapy,but there are disadvantages such as the risk of recurrence,large toxic side effects and irreversible damage to normal tissues.As a new treatment method,optical therapy has the advantages of low dark toxicity,high selectivity,and long lasting.It has attracted the attention of the majority of scientific researchers.Optical therapy uses photosensitizers to absorb specific wavelengths of light to generate heat and reactive oxygen species（ROS）,destroy tumor tissues and induce tumor cell apoptosis.Optical therapy is divided into photothermal therapy（Photothermal therapy,PTT）and photodynamic therapy（Photodynamic therapy,PDT）.Due to the weak penetration of visible light and the greater damage to tissues by ultraviolet light,near-infrared light（NIR）is the best light source for optical treatment.PTT requires a photosensitizer with high photothermal conversion efficiency.The photosensitizer will generate light and heat when irradiated by NIR,destroy the tumor tissue and cause tumor cell apoptosis.PDT is a photosensitizer that converts O₂ and H₂O in the tumor cell environment into reactive oxygen species（·O₂^-,¹O₂,·OH）that can cause apoptosis of surrounding cells under the irradiation of a suitable light source.In addition,due to the low oxygen concentration at the tumor site,Will greatly reduce the therapeutic effect of PDT,and hypoxia will cause metabolic abnormalities,induce cancer cell metastasis and other problems,significantly affecting the anti-cancer efficacy.Therefore,a photosensitizer with excellent design synthesis performance,high photothermal conversion efficiency,and improved oxygen concentration,thereby enhancing the effect of optical treatment is particularly important for tumor treatment.In order to solve the above problems and take into account the high photoelectric and photocatalytic properties of Mo-based nanomaterials,we designed and synthesized Mo₂C@C,Mo₂C/Mo N@C,and MoO_3-x,and performed a series of characterization of the materials.The near-infrared region has higher absorption,converts light into high heat,and produces higher reactive oxygen species under near-infrared light irradiation to promote tumor cell apoptosis,and has a higher PTT/PDT synergistic therapeutic effect.At the same time,due to the high X-ray absorption coefficient and photothermal properties of Mo atoms,the in vivo and in vitro CT/PT imaging effects of Mo-based nanomaterials were studied,and their PTT and PDT properties were used to destroy tumor tissues and finally induce tumor cell apoptosis.The specific research content is as follows:（1）By synthesizing（NH₄）₆Mo₇O₂₄ nanomaterials as self-templates,mixed with molten urea and calcined in N₂ at high temperature,the self-templates are decomposed into small particles and further deoxidized and carbonized to form 10-20 nm Mo₂C@C nanosheets.In this process,urea can be used as a carbon source,deoxidizer and dispersant,and plays a vital role in the formation of nanomaterials.Mo₂C@C exhibits high NIR absorption and PTT conversion ability（52.7%）.In addition,with the help of the calculation of the energy band structure and the experimental test,it is found that Mo₂C has a certain degree of metallicity.Under NIR illumination,through the crossing between the bands,a photo-generated charge is generated,which realizes NIR photocatalytic oxygen production and relieves tumor hypoxia.The combination of carbon materials further realizes the transfer of photo-generated charges and promotes the generation of ROS.Not only that,Mo₂C@C nanosheets can also be degraded under weak p H and hydrogen peroxide conditions,and can be metabolized out of mice through urine and feces 14 days after administration,with good biocompatibility and degradable metabolism ability.Because Mo has high X-ray absorption coefficient and photothermal performance,it becomes a Mo₂C@C nanosheet with CT/PT imaging combined with PDT/PTT synergistic therapeutic effect.（2）Self-made（NH₄）₆Mo₇O₂₄ is used as the precursor,mixed with urea in different proportions at 150℃,and calcined at 650℃ under NH3 to prepare Mo₂C/Mo N@C nanosheets.NH3 provides a nitrogen source,while urea is still used as a carbon source,deoxidizer and dispersant.Mo₂C/Mo N@C nanosheets have high NIR absorption capacity and light-to-heat conversion efficiency（59.2%）.In addition,by introducing Mo N（good electrical conductivity）,the ROS generation ability of the material is further improved.In addition,Mo atoms have a high X-ray absorption coefficient,and the nanosheets can still be used as contrast agents for CT imaging.Detailed cell and mouse experiments have confirmed that nanosheets exhibit excellent anti-tumor effects by synergizing PTT and PDT.In summary,Mo₂C/Mo N@C nanosheets integrate multi-modal imaging（CT and PT imaging）and collaborative optical therapy,showing the potential application prospects in anti-tumor.（3）（NH₄）₆Mo₇O₂₄ is used as the precursor,and MoO_3-x is prepared by calcination at 650℃ under N₂ atmosphere.MoO_3-x nanomaterials exhibit higher NIR-excited photoelectron hole separation ability due to oxygen vacancies,so they generate more ROS and have good PDT performance.In addition,MoO_3-x nanomaterials have attracted much attention because of their high light-to-heat conversion efficiency.Therefore,it has potential application value in PTT/PDT cancer.