Biomimetically ornamented rapid prototyping fabrication of an apatite-collagen- polycaprolactone composite construct with nano-micro-macro hierarchical structure for large bone defect treatment

摘要

Biomaterial based bone graft substitutes with favorable mechanical and biological properties could be used as an alternative of autograft for the large bone defect treatment. In current study, we developed an apatite-collagen-polycaprolactone (Ap-Col-PCL) composite constructs with unique nano-micro-macro hierarchical architectures, through combining the use of advanced rapid prototyping (RP) fabrication technology and three dimensional (3D) functionalization strategy. Controllable macro-porous PCL frameworks was fabricated using fused deposition modeling (FDM) technique, then 3D functionalization treatment with the collagen incorporation and biomimetic deposition was carried out to formulate micro-porous collagen networks with nano-apatite structure. Ap-Col-PCL composite constructs displayed a morphology of porous collagen network homogeneously distributing among PCL frameworks, and a layer of bone-like apatite coating after biomimetic deposition, as evidenced by SEM imaging and EDS analysis; and possessed a similar mechanical properties as cancellous bone of the compressive modulus of 68.75±3.39 MPa. The biocompatibility and osteoconductivity of the Ap-Col-PCL constructs was further evaluated by in vitro cellular response and in vivo critical-sized segmental long bone defect implantation. The biomimetically functionalized Ap-Col-PCL composite constructs can not only significantly increase cell adhesion (2.0 folds), promote faster cells proliferation in vitro; but also successfully bridge the segmental long bone defect in 12 weeks with much more bone regeneration (5.2 folds), better osteointegration (7.2 folds) and a faster new bone deposition rate (2.9 folds) in vivo, as shown by X-ray, micro-computed tomographic (micro-CT) imaging, histomorphometric analysis and sequential fluorescent labeling observations, when compared to pristine PCL constructs. Our study demonstrated biomimetically ornamented Ap-Col-PCL constructs exhibit favorable mechanical property, more bone tissue ingrowth and better osteointegration capability as an effective bone graft substitutes for critical-sized bone defect treatment; meanwhile, it can also harness the advantages of RP technology, in particular, facilitating the customization of shape and size of implants according to medical images during clinical application.