Preparation, Drug Delivery And Osteogenic Properties Of Mesoporous Calcium Silicate/chitosan Composites

With the increase in the number of bone defects caused by trauma,tumor resection,accidents,etc.,the demand for bone implants is gradually increasing.Therefore,it is of great significance to develop bone repair materials.At present,there are three methods:autologous bone and allogeneic bone transplantation and bone repair materials.Autologous bone grafts are prone to new wounds and are prone to complications in the communal tissue.Allogeneic bone grafts are prone to cause immune rejection and may cause secondary damage to donors from donor-transmitted diseases.At present,the main artificial synthetic bone repair materials mainly include hydroxyapatite,mesoporous calcium silicate,active bioglass,tricalcium phosphate,etc.These materials have good biocompatibility and osteoconductivity,but do not have certain osteoinductivity.Growth factors,and osteogenic agents can improve the osteoinductive properties of the materials.Therefore,the novel drug delivery system can make up for the lack of current materials in osteoinduction performance,but it is still a huge challenge for clinical application.In this paper,mesoporous CaSiO₃ was prepared by organic template method for the first time,and CaSiO₃/CS microspheres with core-shell structure and CaSiO₃/CS/PFT?powder with Pifithrin-?were prepared by combining with chitosan.Mesoporous CaSiO₃ and chitosan were used to synthesize CaSi O₃/CS and CaSiO₃/CS/SC79 porous scaffolds.The structure and composition of the materials were tested by TEM,XRD,SEM,FTIR,BET,TG-DTA,and the drug release properties were determined.The biocompatibility and biocompatibility of the materials were studied by animal experiments and cell experiments.The diameter of mesoporous CaSiO₃ microspheres is approximately 150-200 nm.The mesoporous structure of CaSiO₃ can be used as a channel for drug loading and release.Chitosan is encapsulated on the surface of microspheres and can effectively control drug release up to 180?g.In vitro tests,both CaSiO₃/CS and CaSiO₃/CS/PFT?materials exhibited good cell compatibility,and cells were able to spread well on the material,with more pseudopodia and no obvious cytotoxicity.In addition,PFT?release increased the relative expression of mRNA of COL1,RUNX2,OCN,the formation of?-catenin and?-actin osteogenic proteins and alkaline phosphatase activity.This is because the released PFT?can inhibit p53 which disrupts?-catenin and increase cell proliferation,as a result the expression of downstream transcripts is more increasingly.CaSiO₃/CS/PFT?exhibited excellent biological activity and osteoinduction performance,indicating that CaSiO₃/CS/PFT?can be applied in the field of bone defects.We fabricated SC79-loaded CaSiO₃/chitosan?CaSiO₃/CS/SC79?scaffolds with excellent osteoinductivity.The CaSiO₃/CS scaffolds exhibited three-dimension interconnected macropores.The CaSiO₃/CS scaffolds had great drug loading efficiency and controlled release kinetics because of mesoporous structure and hydrogen bonding interactions between CS and SC79.Both the CaSiO₃/CS and CaSiO₃/CS/SC79 scaffolds displayed excellent cytocompatibility,supporting the adhesion,spreading and proliferation of bone mesenchymal stem cells?BMSCs?.Interestingly,the controlled release of SC79 from the therapeutic scaffolds accelerated the osteogenic differentiation of BMSCs via activating Akt/GSK3?/?-catenin signaling pathway.In vivo new bone formation on the scaffolds was investigated by Micro-CT,hematoxylin and eosin?H&E?staining,immunohistochemical staining of collagen 1?COL1?,Van Gieson?VG?staining and Masson staining.As compared with the pure CaSiO₃/CS scaffolds,the CaSiO₃/CS/SC79 therapeutic scaffolds significantly promoted the formation of new bone tissues due to the controlled release of SC79.Therefore,the CaSiO₃/CS/SC79 therapeutic scaffolds were novel and promising implants for defined local bone regeneration.