3D Printing And Properties Of Zn And B Doped Bioactive Glass Bone Scaffolds

With the rapid development of science and technology,all kinds of vehicles are widely used.As a result,more traffic accidents and accidental injuries have been caused,and the cases of bone defects have been increasing year by year.Moreover,the aging problem in China is becoming more and more serious,and the incidence of bone inflammation,tumors and other diseases has also increased.The demand for bone repair materials in medical treatment is enormous.Among the bone repair materials,bioactive glass has received widespread attention due to its excellent biological activity,biocompatibility and ability to promote osteoblast growth.This has led to its wide application in bone tissue engineering.However,bioactive glass has poor mechanical properties and is prone to brittle fracture and cannot withstand excessive pressure.Although the traditional melting method is simple and the preparation period is short,the glass obtained by high temperature melting has subpar bioactivity.To prepare bioactive glass scaffolds with bone tissue engineering application value and solve the above two problems,the following methods are often used:（1）element doping,which involves adjusting the composition of glass scaffolds;（2）improving the glass scaffold preparation process;（3）optimizing the structure of the glass scaffold.In this paper,Zn and B elements are added to the 45S5 bioactive glass commonly used in bone repair.On the one hand,the action of Zn and B elements improves some characteristics of the bioactive glass.For example,B can improve the biodegradability of the glass,while Zn can stimulate bone regeneration,inhibit bone resorption,and give the glass a certain antibacterial property.Specifically,Zn and B are added to improve the mechanical properties of the glass.On the other hand,the B element can reduce the melting point of the glass and make it have low temperature sintering characteristics.Zn can also be used as a structural stabilizer to reduce the melting temperature of the glass,which can play an important role in the process of glass melting preparation.Reducing the melting temperature can maintain the good biological activity of the glass.In the sintering process of the glass scaffold,reducing the sintering temperature appropriately is also an improvement of the biological properties of the glass.At the same time,Zn and B doped 45S5 bioactive glass ceramic scaffolds were successfully prepared by UV curing 3D printing technology.Compared with traditional scaffold preparation methods and extrusion molding,3D printing technology can more accurately control the pore size of the scaffold and the connectivity between the pores,which plays a vital role in the transmission and exchange of nutrients and the growth of new bone tissue and new blood vessels.The effects of Zn and B doping on the mechanical properties and bioactivity of glass scaffolds were investigated by XRD,SEM and porosity,shrinkage,compressive strength and bioactivity tests.The results show that the crystalline phase of 0 mol%,2 mol%and 4 mol%B doped bioactive glass（BG）scaffolds sintered at 900°C is sodium calcium silicate(Na₆Ca₃Si₆O₁₈)phase,and the diffraction phase Ca Si O₃ appears when 6 mol%B is doped.The addition of B makes the microstructure of BG more compact and the mechanical properties are enhanced.Under the doping amount of 2 mol%B,the compressive strength of the scaffold is the best at 9.68 MPa.After soaking in SBF simulated body fluid for 7 days,the scaffold shows that a similar hydroxyapatite layer is formed.The incorporation of 4mol%and above Zn will lead to the formation of zinc feldspar（Ca₂Zn Si₂O₇）phase in the scaffold.The presence of this phase makes the glass network structure more compact,and the mechanical properties continue to improve.The maximum can reach 14.52 MPa,which is 3.5times that of pure 45S5 bioactive glass scaffold.After SBF immersion,SEM observed that the scaffold has the ability to generate hydroxyapatite,indicating that doping Zn can improve the biological activity of the scaffold.