Preparation Of Porous PHBV Bone Scaffold And Its Application

Bone tissue engineering is focus on the replacement and reconstruction of damaged bonetissue. One of the most important concerns in this area is developing proper biomaterials andmethod to preparation the bone scaffold which possess high porosity, proper pore structure, andsuitable mechanical properties.Poly (3-hydroxybutyrate-co-3-hydroxyvalerate)(PHBV) is a member of the polyester family.It is produced by microorganisms and can be fully biodegraded, it is also biocompatible. Themechanical property of PHBV is comparable to polypropylene (PP). Thus, the PHBV give rise tomuch attention in bone tissue engineering. For the present, PHBV bone scaffold is made by saltleaching or electrospinning methods. Because the limitation of these methods, in this study, weprepared porous PHBV bone scaffold using thermally induced phase separation method (TIPS) andTIPS-salt leaching method.In this study, we investigated the influence of phase separation temperature, quenching rate,polymer concentration, and salt content on morphology, porosity, and mechanical property ofPHBV scaffold. The results show that:(1) Phase separation temperature effect the morphology of the PHBV scaffold greatly. Whenthe phase separation temperature was above the crystallization point of the dioxane, The PHBVunderwent crystallize during phase separation procedure and formed spherulites structure. Whenthe phase separation temperature was below the crystallization point of the dioxane, the solventcrystallized and formed porous structure. The diameter of the pore varied from90μm-10μm, theporosity can reach to92%. When the PHBV/dioxane was quenched by liquid N2, a leaf-likemorphology was formed because of the unbalance temperature transportation, the pore size wasabout3μm in this structure.The porosity and pore size decreased as the PHBV concentrationincreased when the scaffold was fabricated by TIPS method; the spherulites diameter was alsoshow the same trend when the polymer concentration increased. (2) Macro-pore and micro-pore structure was formed when we use TIPS&salt leachingmethod to fabricate PHBV scaffold. The size of the macro-pore and micro-pore were depended onthe salt particles and TIPS condition, respectively. The mechanical property of PHBV scaffoldwhich fabricated by TIPS&salt leaching method was better than using salt leaching method, thushighly porous, mechanical stable, three dimension PHBV bone scaffold can be obtained byTIPS&salt leaching method.The scaffold in tissue engineering is not only offering a template or physical support for cell toadhere. Nowadays, developing bioactive scaffold which can induce cell to attach, proliferation, anddifferentiation is become more and more important. We modified the porous PHBV scaffold byemploying poly(methyl methacrylate-diethylaminoethylmethacrylate) P(MMA-DEA) coating onthe surface of PHBV scaffold. P(MMA-DEA) has good cell biocompatibility, it can introduce thenitrogen-containing group onto the surface of PHBV scaffold and increase the scaffoldhydrophilicity. As results of which, the attachment and proliferation of human adipose derived stemcells (hADSCs) on this surface coated PHBV was improved. After being osteogenic induced for7days, alkaline Phosphatase was detected on the scaffold. Calcium deposition was examined byalizarin red staining. Results showed that this P(MMA-DEA) surface coated PHBV scaffold canenhance the cell adhesion, proliferation and osteogenic differentiation of hADCS, which can beused as bone reconstruction substitutes.We also incorporated bioactive chitin nanocrystals into the PHBV scaffold. The incorporatingof chitin nanocrystals not only improved the mechanical property of PHBV scaffold, but also thescaffold surface property. Human adipose derived stem cells (hADSCs) were seeded on themodified PHBV scaffolds and been osteogenic induced. The results showed that PHBV/chitinnanocrystals composite scaffolds can facilitate the hADSCs attachment, proliferation andmineralization, which suggested that the composite scaffold can be used as bone tissue engineeringscaffold.