Preparation Of Rare Earth-Doped Layered Hydroxyapatite/Chitosan/Graphene Oxide Composite Scaffold And Its Application In Bone Formation And Tumor Treatment

Bone is the toughest tissue in the human body,and it plays a role in supporting various activities of the human body and protecting other organs of the human body.Bone health is of vital importance to the human body.However,bone tumors are one of the causes of large-scale bone defects in the human body,and even cause the death of patients.In order to meet the major clinical challenges of bone repair caused by bone tumors,bone repair materials with excellent performance and comprehensive functions are needed.Chitosan（CS）and hydroxyapatite（HA）are the most used materials in bone repair.The main component of natural bone tissue is HA,which makes HA have good biological activity and biocompatibility with human tissues.CS is a product of the natural polysaccharide chitin to remove part of the acetyl group,and has various physiological functions such as biodegradability,biocompatibility,non-toxicity,bacteriostasis,anti-cancer,lipid-lowering,and immune enhancement.Therefore,they are usually used in various forms and shapes in tissue repair engineering.Rare earth elements have special physical and chemical properties.Under appropriate low concentration,rare earth elements can promote tissue repair to a certain extent.The method of killing tumor cells through photothermal therapy has received more and more attention in recent years.It uses high temperature to kill tumor cells.So finding the right photosensitizer is one of the keys to photothermal therapy.In this paper,a layered CS scaffold was prepared using freeze-drying technology,and then HA was attached to the CS surface by biomineralization.The gap between the layers was conducive to the attachment of cells,which was beneficial to the proliferation of cells Differentiation.Afterwards,XRD,FTIR,SEM and other methods were used for material characterization.SEM images show that the gap between the layers is about 50-200μm,and HA has a sheet-like morphology.The XRD and FTIR results show that the prepared material mainly shows the HA phase,and there is no remaining heterophase.In order to enhance the bone repair ability of the CS/HA composite scaffold and endow the material with the function of tumor treatment,rare earth elements and graphene oxide（GO）were added to the scaffold material to prepare a YbHA/CS/GO composite scaffold material and subjected to SEM analysis.The results showed that the morphology of the composite scaffold did not change significantly after the addition of rare earth elements,and also showed a layered structure with a layer-to-layer gap of approximately 50-200μm.XRD and FTIR results showed that YbHA/CS/GO composite scaffold mainly showed HA phase.Under the irradiation of near infrared,GO will have a rapid temperature rise.Using this feature,the composite scaffold has been given the ability to treat tumors on the basis of the original bone repair ability.In this way,the YbHA/CS/GO composite scaffold has good bone repair ability on the one hand,and the ability to kill tumor cells under irradiation of near infrared light on the other hand.The release of rare earth ions was tested by ICP and other means.When the release duration reached 144 h,the release concentration of Ca²⁺reached 180.4μM according to statistics,and the release concentration of Yb³⁺ion reached 0.3μM.The test results show that the composite scaffold can release rare earth,and its concentration is within the safe range.In addition,the mechanical properties of the materials were tested in this paper.The compressive properties of all materials are about 0.2⁰.3 MPa.Such mechanical properties can make the materials have a certain supporting capacity without harming the surrounding tissue.At the same time,this article conducted in vitro cell experiments and animal in vivo experiments on the materials to test the ability of the composite scaffold material for bone repair and tumor treatment.The cell experiment results show that the composite scaffold after adding rare earth has no toxic effect on mouse embryonic osteoblasts（MC3T3-E1）.Immunoblotting and expression experiments of osteogenic genes showed that YbHA/CS and YbHA/CS/GO can activate the related osteogenic factors BMP-2,Smad,and finally upregulate the expression levels of Runx-2,COL-1and ALP.Finally,CT experiments on mouse skulls show that YbHA/CS and YbHA/CS/GO can effectively promote the repair process of bone tissue,and the new bone area and bone density of the mouse skull after YbHA/CS and YbHA/CS/GO repair are much larger in the HA/CS group.Moreover,YbHA/CS/GO has a certain killing ability on breast cancer bone metastasis cells（MDA-MB-231）under the irradiation of near infrared light.By observing the temperature change of the stent under near infrared light irradiation for 120 S,YbHA/CS/GO can reach about 51℃.The results of MDA-MB-231 live dead cell staining and cell lapse experiments show that YbHA/CS/GO can effectively kill tumor cells under the irradiation of near infrared light.Finally,after measuring the tumor volume,the experimental results show that YbHA/CS/GO can effectively inhibit tumor growth.