Scpp Scaffolds For Bone Tissue Engineering Research

The key factors in the tissue engineering are scaffolds, seeded cells, growth factors and tissue culture, which are also the problem expected to be resolved. The optimal biomaterials as scaffolds in the tissue engineering were still in the stage of filtration from many candidates. As a part of National Science Foundation of China 'The research of molecular self-assemble nano RADA16-RGD/CPP compounds for bone repair (50472091)', the aim of this study is to develop a novel controllably biodegradable scaffold for bone tissue engineering.Recently, calcium polyphosphate (CPP), as a kind of inorganic polymers, has drawn attention due to its controllable degradability, outstanding biocompatibility and enough strength. Meanwhile, strontium has been gradually recognized during the research of treatment for osteoporosis. It enhances the replication of preosteoblastic cells and decreases bone resorption. In this study, started with the research of CPP, it is included the parts as follows: the calculation model of degree of polymerization(DP), the effect of structure on strength, the rule and factors during the degradation and the cell culture in vitro. After the P-CPP was assured to be optimal to the growth of osteoblasts, strontium as a kind of bone-seeking trace elements was added into P-CPP, and the preparation, biocompatibility and implantation into dog's thighbone was explored to decide the SCPP containing 1% strontium is optimal.In this study, the porous CPP with its structure like cancellous bone was synthesized. By analyzing the polycondensation process of calcium phosphate monobasic monohydrate, the calculation model of DP was carried out, which was validated by IR and ³¹PNMR. Then CPP samples with different DP were prepared. By sintering at different temperature, the α-CPP,β-CPP和γ-CPP were obtained. Compared with the compressive strength of α-CPP,β-CPP和γ-CPP, it of a-CPP was highest. Meanwhile, with the increase of DP, the compressive strength also increased.In this study, the factors during the degradation were explored carefully, such as crystalline style, DP, porosity and diameter of frits. And the change of materials during the degradation was also analyzed. The results showed that the effect of crystalline style and DP on the velocity of degradation was notable. Whether in the SBF or Tris solution, the CPP with crystalline style was not the same. From the point of weight loss, the sequence was a-CPP < P-CPP < y-CPP; from the point of releasing PO43', it was also a-CPP < P-CPP < y-CPP. So the crystalline style was an effective way to change the velocity of degradation. Furthermore, smaller DP, higher porosity, and smaller the frits resulted in the faster velocity of degradation. The surface change during the degradation was as follows: after soaking in the Tris solution for 30 days, the tiny holes became more and more; after soaking in the SBF for 30 days, there were much aggradation on the surface of samples, and its turn was a-CPP < P-CPP < y-CPP. The aggradation was judged as hydroxyapatite containing CO32". The change of compressive strength during the degradation was as follows: a-CPP < p-CPP < y-CPP.In this study, the SCPP containing different dose of strontium was prepared. Its structure, performance and the degradable rule were explored. After analyzing the curve of growth of cells which were cultured with CPP with different crystalline style, the p-CPP was optimal to the growth of cells. Then the strontium was added into P-CPP by three methods, in which the raw materials as CaCO3 and S1CO3 were the best. From the data of XRD, the crystal system of SCPP was change between 48%-50%. When the strontium in SCPP was below 48%, the crystal system of SCPP was the same as P-CPP, which was monoclinic; when the strontium in SCPP was more than 50%, the crystal system of SCPP was the same as a-SPP, which is rhombohedral. From the degradation results of SCPP containing different strontium dose, it was showed that with the increase of strontium, the velocity of degradation became slower. When the dose was 60-70%, it was the slowest. The velocity of SPP was slower than it of CPP.In this study, the effects of SCPP on cells' proliferation and differentiation wereevaluated by MTT and ALP activity assay. The results showed that 1% SCPP was optimal to the growth of osteoblasts. The cells on the scaffolds were observed by the light microscopy, fluorescent microscopy, scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). They also excreted much extracelluar matrix and showed high activity.In this study, the CPP and 1% SCPP porous scaffolds were implanted into the dog's thighbone for 12 weeks to examine the biocompatibility in vivo. The results showed that the macroporous structure permitted effective ingrowths of connective tissue and new bone in the thighbone, without eliciting a foreign body reaction or an inflammatory response. The trabecular bone in the porous 1% SCPP was more than it in the porous CPP. Meanwhile, the artery was observed near the surface of 1% SCPP in the pore.It is the first time to point out the convenient calculation model of the DP of CPP, to explore the effects of crystalline style and DP on the strength and degradation, to prepare the SCPP containing different dose of strontium, and to explore the structure, performance and the degradable rule of SCPP. To explain relationships between the structure and nice biocompatibility, the reasons were given that the structure of P-O-P in CPP or SCPP was similar to it of the ATP from the molecular level.In total, the results showed that the porous SCPP may be a promising material for the bone tissue engineering. And by adding proper dose of helpful trace elements into biodegradable materials, it was beneficial to the growth of cells and bone repair, which was a novel direction for the design of biomaterials.