| Bone tissue engineering has been heralded as the alternative strategy to regenerate bone.Bone tissue engineering requires a scaffold conducive to cell attachment and maintenance of cell function,together with a rich source of osteoprogenitor cells in combination with selected osteoinductive growth factors.Scaffolds need to be biocompatible,ideally osteoinductive,osteoconductive,biodegradable and mechanically compatible with native bone to fulfil their desired role in bone tissue engineering. Apatite-wollastonite bioactive glass-ceramic (AW-GC) has high biocompatibility and bioactivity.Some reports indicate the dissolution of bioglass promotes the expression of some gene,which cortrols and induces the begin and course of cell cycle. Consequently the bone regeneration and osteoproduction are enhanced.Porous sol-gel derived bioglass has high bioactivity because it possesses high specific surface areas which can adsorb bioactive substances.Moreover,this bioglass can control the interfacial reactive kinetics and degradation rate by adjusting the structure and porosity of the matrix. Owing to such properties,AW-GC is a prospective scaffold for bone tissue engineering. AW-GC was prepared by sintering the precursor powder derived from sol-gel process. Porous AW scaffold(AW) was prepared through mixing,using stearic acid as porogen,compression molding and sintering process.Basis on this,in order to further increase the porosity and control the degradation rate,biodegradable β-tricalcium phosphate(β-TCP) is added into AW-GC to prepare AW/β-TCP composite scaffold(AW/β-TCP). AW/β-TCP has appropriate preliminary mechanical strength,and can increase the porosity by developing a in situ porous structure as the degradation of β-TCP.The degradation of β-TCP can also provide abundant calcium and phosphate for the bone growth. The phase compositions and microstructure of both scaffolds were characterized by scan electron microscopy (SEM) , X-ray diffraction (XRD).The compressive strength and porosity of both scaffolds were measured.The bioactivity and biodegration were investigated by soaking both scaffolds in simulated body fluid (SBF). The surface morphology, phase compositions and microstructure of both scaffolds after soaked in SBF were examined by SEM and infrared spectroscopy(IR),the concentration changes of calcium in SBF were measured with inductively couple plasma atomic emission spectroscopy(ICP-AES),and the changes of pH values in SBF were recorded. Osteoblastic rat mesenchymal stem cells(rMSCs) were co-cultured with both scaffolds in vitro.The cells-material complex was observed by SEM ,the test of MTT and alkaline phosphatase(ALP) were evaluated. The results show: (1)The phases of AW include apatite and wollastonite. The phases of AW/β-TCP include apatite, wollastonite andβ-tricalcium phosphate, which indicates no new solid state reactions happens between the AW glass-cceramic powder and β-TCP powder during the process of mixing ,compressing and sintering.The porosity and pore diameter of scaffolds can be control by the content and particle size of the porogen. AW and AW/β-TCP with 30% of stearic acid posses compressive strength as high as 15.3 and 14.3MPa,porosity as high as 67.1% and 66.9% , respectively.The pore diameter ranged from 100 to 500μm.Both scaffolds have appropriate mechanical strength and porous structure.(2)A layer of carbonate hydroxyapatite (HCA) can form on the surfaces of both scaffolds when soaked in SBF,which indicates they are bioactive.The crystallite HCA formed on AW is worm-like,while that formed onAW/β-TCP is ball-like,these are due to the difference of the supersaturation of the SBF after the two scaffolds are soaked in it.The in vitro tests also indicate both scaffolds are degradable in SBF.The addition ofβ-TCP can increase the porosity correspondingly.(3) Osteoblastic rMSCs are biocompatible with both scaffolds,and can attach,proliferate and differentiate on both scaffolds.The proliferation and differentiation of osteoblastic rMSCs increase with the roughness of AW. AW and AW/β-TCP scaffolds have potential for application in bone tissue engineering.
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