Fabrication Of Bioceramic Scaffolds For Bone Tissue Repair And Treatment Of Osteoporotic Bone Defect

Over the last three decades biomaterials engineers have developed bioceramics and other materials with increasing complexity,recognizing that imperfections are not always detrimental but can be useful to tune mechanical,biodegradable or biological properties.A wide range of models and concepts has been developed to understand the influence of composition and microstructure characteristics on the properties of engineering biomaterials.In this regard,the promising future of inorganic bioceramics as a group of preferable functional biomaterials with highly integrated synergistic functions,may ultimately depend on tuning their composition and microstructures.In this paper we discuss the successful fabrication of bioceramic granules in(i)Enhancing bone regeneration and repair beyond homogenous hybrid and(ii)stimulating new bone growth and treatment of osteoporotic femoral bone defect.In the first part of this study,we succeeded in fabricating bioceramic granules with bi-layered,porous and bi-phase hybrid architecture from yolk to external shell(i.e.,CSi-Sr4,CSi-Sr4/TCP,TCP,CSi-Sr4@TCP and CSi-Sr4@TCP-p30).Beyond the homogenous hybrid bioceramics,varying the bioceramic slurry composition design makes it easy to manufacture bilayer bioceramic granules with tailorable microporous shell structures.The results in vitro and in vivo of this study demonstrate that bioceramic selection plays an important role in the resulting physicochemical properties and osteogenic potential of granule scaffolds for use in bone regeneration and repair in situ.Moreover,the preliminary data reveals osteogenic stem cells that adhere to the TCP granule when compared to the highly biodegradable CSi.The variation in the biodegradation rate derived from the selective microstructural tailoring in sparingly dissolvable Ca-phosphate shell layer is especially beneficial for controlling bioactive ion release from the yolk layer(Sr-doped wollastonite)and spatiotemporal evolution of macro-/micro-pore network in the granule scaffolds.Based on this abnormal but expected composition distribution and microstructural property,it could be considered that the biphasic bioceramic granules with tuned microporous shell layer result in enhancing osteostimulation and osteoconduction in comparison with the conventional single-phase bioceramic granules and homogenously mixed hybrid granules.This is for the first time,to the best of our knowledge,that the bioceramics concerning gradient distribution and microstructure-tailoring design is available for tailoring biodegradation and ion release(bioactivity)to optimizing osteogenesis.Furthermore,it is possibly helpful to develop new bioactive scaffold system for time-dependent tailoring bioactivity and microporous structure to enhance bone regeneration and repair applications,especially in some non-load-bearing arbitrary 3D anatomical bone defects.On our second study,we focused on developing desirable characteristics of the third-generation biomaterials in promoting osteogenous cells activation in a balanced time schedule to treat pathological bone disease like osteoporosis.Balancing the degradation with the pathological bone's natural healing timescale is still a great challenge,and especially there's a lack of material design on how to control spatiotemporal evolution of pore network of the biodegradable porous inorganic biomatrials scaffolds and how the body responds to the bioactive ion stimulations and osteogensis.In this paper,we have developed the new yolk-shell biphasic granules by extruding the alginate-based Ca-silicate(CSi,C2Si)powder or mesoporous bioactive glass(MBG)powder slurries through the coaxial bilayer capillary system.The self-curing C2Si shell could readily integrated the yolk component such as CSi or MBG which produced different biodegradation rate with time.The variation in the biodegradation rate derived from the yolk-shell system is especially beneficial for controlling bioactive ion doses and spatiotemporal evolution of macropore network in the granules scaffolds.These beneficial factors were to help overcome the limitation in the repair and reconstruction of osteoporotic bone defect.Extensive in vitro and in vivo analysis indicated that the CaSiO3@Ca2SiO4 and MBG@Ca2SiO4 bioceramic granules had superior advantages in terms of well controlled ion release,better rate of degradation and enhance osteogenic integration compare to the Ca2SiO4@Ca2SiO4 granules when implanted in the osteoporotic bone defect.