Construction And Properties Of Calcium Phosphate Cement Composite Scaffold With Unidirectional Pore Structure

A PLGA/CPC scaffold with unidirectional lamellar pore structure was fabricated by theunidirectional freeze casting of CPC slurry and the following infiltration ofpoly(lactic-co-glycolic acid)(PLGA) in this study. In vitro degradation, cell response and invivo osteogenesis of PLGA/CPC scaffold were conducted. Furthermore, the composition,three dimensional (3D) structure of PLGA/CPC scaffold were redesigned to optimize itsmechanical performance, cell response and in vivo osteogenesis.The pore wall of PLGA/CPC scaffold was covered by PLGA film. The PLGA film firstlydegraded during immersion in PBS solution, which was accompanied with the exposure ofCPC matrix that was beneficial for cell response and osteogenesis. The unidirectional lamellarpore structure of PLGA/CPC scaffold was beneficial for growth of cells into inner macropores,but unfavorable for cell seeding and differentiation. After being implanted in vivo, new bonetissues grew along the unidirectional lamellar pores into the scaffold. The PLGA film on thepore wall of PLGA/CPC scaffold compromises the osteoconductivity of CPC due to poor cellresponse of PLGA. In order to improve cell response of PLGA/CPC scaffold, collagen wasimmobilized on the PLGA film of PLGA/CPC composite scaffold by plasma treatment underthe ammonia atmosphere. After immobilization of collagen, the cell seeding, adhesion,proliferation and differentiation on PLGA/CPC scaffold were significantly enhanced.However, the results of histological evaluation showed that the osteogenesis of PLGA/CPCscaffold was not obviously improved after immobilization of collagen.To meet the requirements of bone defect repair at various sites, a core/shell bi-layeredCPC-based composite scaffold with adjustable compressive strength, which mimicked thenatural structure of cortical/cancellous bone, was fabricated. The dense tube-like CPC shellwas prepared by designing a mould and isostatic pressing process. A porous core withunidirectional lamellar pore structure was fabricated inside the cavity of dense tube-like CPCshell by aforementioned unidirectional freeze casting, followed by infiltration of PLGA andimmobilization of collagen. The compressive strength of bi-layered CPC-based compositescaffold can be controlled by varying thickness ratio of dense layer to porous layer (590MPa). Compared to the scaffold without dense shell, the pore interconnection of bi-layeredscaffold was not obviously compromised because of its high unidirectional interconnectivitybut poor3D interconnectivity. The cells adhered and proliferated well on the bi-layered CPCbased composite scaffold.Gelatine microspheres (GM) were used to modify the3D pore structure of PLGA/CPC scaffold. After being modified by various amounts of GM (5%30%), the compressivestrength and porosity of the PLGA/CPC scaffold remained in the range of2.45MPa and62%72%, respectively. The unidirectional lamellar pores were divided into smaller pores.Macropores with the size of80200μm were left being generated by the dissolution of GM.The scaffold modified by20%GM exhibited the most excellent cell seeding, proliferation anddifferentiation. The pore interconnection of scaffold was not starkly compromised aftermodification by GM so that cells still penetrated into the inner pores of scaffolds smoothly.PRP-PLGA/CPC construct was fabricated by infiltration of platelet-rich plasma (PRP)into PLGA/CPC scaffold. The incorporation of PRP significantly improved cell response ofPLGA/CPC scaffold. The PRP-PLGA/CPC composite scaffold was implanted in femoralbone defects of rabbits, the results showed that PRP boosted markedly bone ingrowth,angiogenesis and degradation of PLGA/CPC scaffold. The PLGA/CPC scaffold withunidirectional lamellar pore structure was originally used to reconstruct the segmental bonedefect in radius of rabbit. The new bone tissues grew well along the unidirectional lamellarpores of scaffold regardless of its poor3D pore interconnection. The incorporation of PRPshowed outstanding improvement in osteogenesis of PLGA/CPC scaffold as implanted in thesegmental bone defect in the radius of rabbit.