Tween-20 Modified BiVO₄ Nanorods For CT Imaging And Sensitizing Radiotherapy Of Oral Cancer

Objective:Oral cancer is the most common malignant tumor in the oral and maxillofacial region,which seriously threatens the physical and mental health of patients.Radiotherapy is one of the commonly used methods in the treatment of oral cancer.However,the resistance of tumor tissues to ionizing radiation and the side effects of X-rays on healthy tissues still limit the application of radiotherapy.In recent years,tumor radiotherapy guided by computed tomography（CT）imaging can be achieved by using nanomaterials with high atomic number elements as radiosensitizers and CT contrast agents.At the same time,the modification of nanomaterials based on the above elements by biocompatible polymers can effectively reduce the side effects of radiosensitizers and provide a new way to achieve efficient,accurate,and safe radiotherapy for oral cancer.Methods:The BiVO₄ nanorods（BiVO₄ NRs）were synthesized in an organic solution with oleylamine and oleic acid as ligands.The surface of BiVO₄ NRs was modified by high biocompatibility polymer Tween-20（Tw20）.While BiVO₄ NRs were transferred from the oil phase to the aqueous phase,Tw20-BiVO₄ nanorods（Tw20-BiVO₄ NRs）were obtained.The morphology and structure of Tw20-BiVO₄ NRs were characterized by transmission electron microscope（TEM）,ultraviolet spectrophotometer（UVS）,and X-ray diffractometer（XRD）.In the in vitro experiment,the CT imaging effect of Tw20-BiVO₄NRs was tested by CT scanner,the cytotoxicity of Tw20-BiVO₄ NRs to CAL27 cells was detected by flow cytometry,and the effects of Tw20-BiVO₄ NRs on tumor cell proliferation and apoptosis after X-ray irradiation were detected by colony formation test and flow cytometry in vitro.Immunofluorescence assay and flow cytometry were used to detect whether the effect of X-ray irradiation on the level of intracellular ROS after co-culture of Tw20-BiVO₄ NRs and cells could enhance the effect of DNA double-strand break and increase cell apoptosis.In the in vivo experiment,BALB/c nude mice were subcutaneously injected with CAL27 cells in the middle of the buttocks to establish a squamous cell carcinoma model,and 24 hours after Tw20-BiVO₄ NRs was injected through tail vein.And then CT imaging was performed to evaluate the CT imaging ability of Tw20-BiVO₄ NRs in vivo.After X-ray irradiation,the tumor volume and body weight of mice were recorded every day,and after treatment,the mice were killed to take out the tumor and weigh it,and the therapeutic effects were compared.Hematological analysis and histopathological examination of major organs were used to evaluate the biosafety of Tw20-BiVO₄ NRs.Results:TEM shows that Tw20-BiVO₄NRs has a regular one-dimensional rod-like morphology and uniform size distribution.The UVS absorption spectrum of Tw20-BiVO₄NRs proves the existence of BiVO₄.The position and relative intensity of the diffraction peak in the XRD spectrum correspond to the standard card height of monoclinic BiVO₄（JCPDS:83-1699）,which proves that BiVO₄ in Tw20-BiVO₄ NRs is monoclinic.The results of CT imaging in vitro show that Tw20-BiVO₄ NRs have good imaging ability in vitro,and the results of flow cytometry showed that Tw20-BiVO₄ NRs had low toxicity to CAL27 cells.Colony formation assay and flow cytometry analysis showed that X-ray irradiation after co-culture with Tw20-BiVO₄ NRs could effectively reduce the ability of cell proliferation and increase the rate of apoptosis.The results of immunofluorescence and flow cytometry showed that co-incubation of Tw20-BiVO₄ NRs and CAL27 cells followed by X-ray irradiation could significantly increase the level of intracellular ROS,increase the degree of DNA double-strand break,and thus promote cell apoptosis.The experimental results of constructing a squamous cell carcinoma model in BALB/c nude mice show that Tw20-BiVO₄ NRs have strong CT imaging ability in vivo and can enhance the effect of radiotherapy on squamous cell carcinoma.And hematological analysis and histopathological results of major organs showed that Tw20-BiVO₄ NRs had good biological safety.Conclusion:1.Tw20-BiVO₄ NRs have a strong ability to absorb X-rays.X-ray irradiation after co-culture with squamous cell carcinoma cells can significantly increase the level of free radicals and aggravate the destruction of chromosomes,thus promoting apoptosis and reducing the ability of cell proliferation,to improve the therapeutic effect of radiotherapy.2.Tw20-BiVO₄ NRs is expected to be used in radiotherapy guided by CT imaging,which can not only determine the location of the tumor and guide accurate radiotherapy but also improve the sensitivity of radiotherapy and reduce the side effects of radiotherapy.