Hydrogel Loaded With Black Phosphorus Nanosheets/Doxorubicin For Osteosarcoma Treatment By Chemo-photothermal Therapy

Background:Osteosarcoma is a highly malignant primary bone tumor,with a third incidence rate among children and adolescents.The treatment of osteosarcoma usually requires surgical resection of tumor tissue.However,it is difficult to ensure the complete removal of tumor cells through surgery.The remaining osteosarcoma cells can survive in and around bone tissue,resulting in tumor recurrence.In order to completely remove tumor cells,surgery combined with postoperative adjuvant chemotherapy has become the standard treatment strategy of osteosarcoma.However,the side effects and adverse reactions of systemic chemotherapy,such as hair loss,vomiting and bone marrow suppression,will bring great pain to patients and seriously affect their quality of life.In recent years,unconventional therapies based on biomaterials,such as targeted therapy,gene therapy,photothermal therapy（PTT）,photodynamic therapy and drug delivery system,have been widely studied.PTT refers to the local treatment method of ablation of lesions through the thermal effect of photothermal converter under the irradiation of nearinfrared light（NIR）.Black phosphorus nanosheets（BPNS）have attracted extensive attention in the scientific community since they were first stripped from bulk black phosphorus（BP）in 2014.BPNS has many excellent characteristics,such as good biocompatibility,large specific surface area,adjustable band gap and high extinction coefficient.Compared with other two-dimensional materials,BPNS has higher photothermal conversion efficiency.It is an ideal PTT nano material.Hydrogel is similar to natural tissue in many aspects.It has the advantages of good drug storage and long term sustained release.It has broad application prospects in drug delivery and tissue engineering.Hydrogel has excellent biocompatibility,biodegradability and local retention effect.It can improve the concentration of local chemotherapy drugs,reduce the side effects of systemic administration,significantly reduce the toxicity to normal cells and enhance the killing efficiency of tumor cells,so it has great potential in the field of antitumor.In this study,BPNS and doxorubicin（DOX）were encapsulated in chitosan hydrogel（CS）to prepare BPNS/DOX/CS and to study its ability to abate tumor.Objective:To explore the ability of BPNS/DOX/CS to abate osteosarcoma through chemophotothermal therapy.Methods:BPNS was prepared by liquid-phase stripping method,and BPNS and DOX were encapsulated in chitosan thermosensitive hydrogel to obtain BPNS/DOX/CS.BPNs was characterized by scanning electron microscope（SEM）,energy spectrum analysis,transmission electron microscope（TEM）and particle size distribution instrument.The phase transition time of BPNS/DOX/CS was studied by tube inversion method.The photothermal effect and photothermal stability of BPNS/DOX/CS in vitro were evaluated by infrared thermal imager,and the release of DOX in vitro was evaluated by multifunctional enzyme labeling instrument.The biocompatibility of BPNS/CS was evaluated by CCK-8 method.The photothermal antitumor properties of BPNS/DOX/CS were evaluated by live/dead staining.The tumor ablation ability and systemic toxicity of BPNS/DOX/CS in vivo were studied by tumor bearing experiment in mice.Results:BPNS and BPNS/DOX/CS were successfully prepared in this study.SEM showed that BPNS had uniform two-dimensional flake morphology.BPNS/DOX/CS can achieve sol-gel transition in 10 minutes at 37 ℃.In vitro photothermal experiments show that BPNS/DOX/CS had good photothermal effect and photothermal stability.Cytotoxicity test showed that BPNS/CS had no obvious toxicity to L929 cells.In vitro and in vivo anti-tumor experiments showed that BPNS/DOX/CS had significant anti-tumor ability,and no obvious toxicity was observed in vivo experiments.Conclusion:In this study,BPNS/DOX/CS drug loaded platform was successfully prepared.The platform could achieve rapid sol-gel transition at physiological temperature.The combination of PTT and chemotherapy can significantly kill tumor cells and tissues.The treatment platform has a good application prospect in the local treatment of tumor.It is expected to become a new strategy for tumor treatment.