Study On The Moldable And Bioactive Calcium Silicate-based Materials For Tissue Repair

As compared with the biomaterials used in the forms of blocks and particles,the tissue repair materials with moldable property can be arbitrarily shaped according to the irregular tissue defect site.Therefore,the moldable materials have received extensive attention and application in tissue repair materials.However,there are some other deficiencies in the field of moldable materials for bone,teeth and wound repair.For example,the tricalcium silicate-based bone cement still showed poor washout resistance,long setting time and single function,while the moldable polyvinyl alcohol hydrogel crosslinked by borate lacked bioactivity to stimulate the healing of the wound.In this dissertation,novel moldable silicate materials with bioactivity were designed and prepared to improve the deficiencies of the silicate-based tissue repair materials.The main content and results are described as follows:Developing a novel tricalcium silicate/alginate composite cement with improved washout resistance.The results showed that the washout resistance and handling properties have been improved due to the fact that alginate could chelate with Ca²⁺to form three-dimensional calcium alginate hydrogel,which hindered the collapse of the tricalcium silicateparticles and thus resulted in enhanced washout resistance.Besides,the as formed hydrogel also reinforced the composite cement,and the compressive strength was up to 54.0 MPa,which was much higher than that of tricalcium silicate?35.3 MPa?.In addition,the composite cement retained the in vitro bioactivity of tricalcium silicate,such as the ability to induce apatite formation in vitro and to promote the proliferation of osteoblasts.Developing a kind of ready-to-use premixed cement by introducing non-aqueous reagents?polyethylene glycol and glycerol?into tricalcium silicate-based cement for root canal treatment.Moreover,setting accelerator?calcium chloride and magnesium phosphate cement?were introduced to fabricate a fast setting premixed cement.When injected into water,hydration of tricalcium silicate occurred via the exchange of water with polyethylene glycol or glycerol.In particular,the setting time of the premixed calcium silicate/magnesium phosphate cement was significantly shortened to 70 min,which was much shorter than that of the premixed tricalcium silicate cement.In addition,the premixed cement exhibited superior antibacterial properties owing to a large amount of OH^-generated during the hydration process.Meanwhile,the premixed cement showed good bioactivity to induce apatite formation and to stimulate dental pulp stem cell proliferation.Ultimately,a premixed cement with radiopacity was prepared and injected into the root canal of the extracted teeth,and the results indicated that the premixed cement showed good flowability and could be well filled into the root canal.Developing a novel tricalcium silicate-based cement with good photothermal property by co-precipitation of tricalcium silicate with graphene oxide in an aqueous solution.The results indicated that a large amount of graphene oxide could be introduced without influence on the phase and hydration performance of tricalcium silicate particles.To some extent,the content of graphene oxide could shorten the setting time and reinforce the compressive strength of tricalcium silicate.More importantly,the tricalcium silicate/graphene oxide composite cement showed excellent photothermal properties:when placed at room temperature and soaked in water,the temperature of the composite cement could rise to 100?within 30 s and 45?within1 min,respectively.Meanwhile,the photothermal property also promoted the tricalcium silicate cement to harden and to provide a certain mechanical strength within 1 hour.In addition,the composite cement possessed excellent photothermal property due to the uniform distribution of graphene oxide.Furthermore,the subcutaneous tumor experiments revealed that the composite cement could suppressed the growth of the osteosarcoma.Developing a moldable hydrogel with bioactivity via the crosslinking between the polyvinyl alcohol and borosilicate glass.On one hand,the borate ions released from the bioactive glass were used as a crosslinker of the polyvinyl alcohol.On the other hand,the hydrogel released calcium,silicate and borate ions and thus stimulated the proliferation of the fibroblasts and endothelial cells.It was interesting to note that the hydrogel showed excellent formability,self-healing property and a certain degree of tissue viscosity.Therefore,the hydrogel could be prefabricated before use and arbitrarily molded in order to fit the defect and size of the skin wound.More importantly,the hydrogel could adhere to the relatively dry site around the wound,but did not stick to the wound itself because of the existence of water.The special character of the hydrogel could avoid the secondary injury to the wound when removing it from the wound.We further validated the effect of the hydrogel on chronic wound healing,and the preliminary result indicated the hydrogel could promote the healing process of the chronic wound.Therefore,the washout resistance and handling properties of the tricalcium silicate cement could be improved by the introduction of alginate,and the bioactivity of the calcium silicate retained.Besides,non-aqueous reagents and accelerates could be used to prepare a fast setting premixed cement,so it could be applied to the root canal therapy more conveniently.Biofunctional cement could be prepared via introducing graphene oxide into tricalcium silicate,and the cement showed prospect in bone regeneration and osteosarcoma therapy.Finally,the hydrogel with moldable property and bioactivity could be used in chromic wound healing.In summary,a new type of moldable and bioactive materials with prospect for tissue repair could be prepared on the basis of the current investigation of the silicate-based materials.