Improvement Of Osteogenesis And Angiogenesis Of Calcium Phosphate Bone Cement By Introducing Functional Ions

Calcium phosphate cement(CPC)is osteocondunctive,but the lack of osteoinduction and angiogenesis restricts its application in bone defeat repair.Many researches show that the introduction of functional ions in bone repair material,such as silicon,magnesium,zinc and strontium,are conducive to the formation of new bone and/or blood vessels.In this paper,multifunctional CPC was prepared by the respective incorporation of single and multiple ions with osteoinductive property and angiogenesis.The effects of these ions on physicochemical properties and biological properties of CPC were investigated,which can help pave the way for its application in the field of bone repair.To improve the osteogenesis of CPC,Mn2+ and Sr2+ containing CPCs were respectively prepared by the addition of absorbable Mn doped tricalcium phosphate(Mn-TCP)powder and different strontium containing compounds(Sr-PCCP,SrCO3,SrHPO4,SrSiO3 and SrSO4).The addition of Mn-TCP shortened the setting time and retarded the strength and injectability of CPC.The mBMSCs on the surface of Mn-TCP/CPC presented better adhesion and spreading behaviors,higher proliferation rate and ALP activity,and more expression of osteogenic related genes(Col-I,OC,Runx2).The behaviors of the cells were related to the increase of the protein adsorption of CPC and the role of Mn2+ on osteogenesis.Mn2+ in the appropriate concentration range(< 3.59 μg/m L)could significantly promote the adhesion,proliferation and early osteogenic differentiation of mBMSCs.The introduction of Sr2+ shortened the setting time,decreased the compressive strength slightly and increased the injectability of CPC.The electronegativity of Sr-CPCs decreased and the surface roughness and microstructure changed,which resulted in the enhanced protein adsorption capacity of BSA and LSZ.When compared to the control cement,the adsorption of LSZ of CPC with SrSiO3 improved 70.83%.Furthermore,mBMSCs on the surface of Sr-CPCs showed better adhesion behavior and cell activity,higher cell proliferation rate and ALP activity,and more expression of osteogenic related genes.The effect of Sr-CPCs on the osteogenesis was related to the concentration of Sr2+ and the release rate of Sr2+.In addition,CPC with SrSiO3 could release silicon ions,which further promoted the osteogenic differentiation of the cement.Silicon has a role in promoting angiogenesis.Magnesium plays an important role in the formation of blood vessels and bone metabolism.To improve the osteogenesis and angiogenesis of CPC,CPC with binary ions Sr2+/Si4+ and Mg2+/Si4+ were prepared by incorporating degradable Sr-doped calcium silicate(Sr-CS)particles and magnesium containing silicates [MS: including akermanite(Ake),diopside(Dio)and forsterite(For)] into CPC.The addition of SrCS prolonged the setting time,decreased the compressive strength a little and increased the injectability of CPC.Besides,Sr-CS decreased the electronegativity,refined the lamellar crystals and increased the surface roughness of CPC,thus improved the ability of BSA adsorption.Sr-CS/CPC could release silicon and strontium ions slowly,and the concentration of strontium ion had a positive correlation with the content of strontium addition.The dissolved ions significantly promoted the adhesion,proliferation and osteogenic differentiation of mBMSCs when compared with CPC containing only Si4+.Low content of Sr2+ and Si4+ could promote the adhesion,proliferation and angiogenesis of HUVECs.With the respective addition of three kinds of MS,the setting time of CPC was respectively prolonged while the strength and the injectability were enhanced at first and declined later with the increase of their content.MS/CPC had lower electrical conductivity,finer lamellar crystal and improved adsorption of BSA and LSZ.The adsorption of BSA of CPC with 10 wt.% Dio and 5 wt.% For were both enhanced about 75%.The ions,Mg2+ and Si4+,released from CPC with appropriate amount of Ake,Dio and For could significantly promote the adhesion,proliferation and osteogenic differentiation of mBMSCs and enhance the activity and angiogenesis of endothelial cells.In order to further improve the osteogenesis and angiogenesis,CPC with Zn2+,Sr2+ and Si4+ were prepared by the incorporation of Zn and Sr co-doped CS particles.The addition of(Zn,Sr-CS)into CPC prolonged the setting time,reduced the compressive strength a little,reduced the electrical resistance and improved the BSA absorption ability of CPC.The ions,Zn2+,Sr2+ and Si4+,were released from(Zn,Sr)-CS/CPC steadily and improved the adhesion,proliferation and osteogenic differentiation of m BMSCs.The effect of Zn2+/Sr2+/Si4+ on the osteogenesis of CPC was higher than that of Sr2+/Si4+和 Zn2+/Si4+.Besides,these ions promoted the activity and angiogenesis of endothelial cells,but the effect decreased with the increase of the concentration of Zn2+ and Sr2+.