Study Of Degradation Rule And Degradation Velocity Effect Factor Of SCPP For Bone Repair Material

The ideal bone repair materials must have osteoconduction, osteoinduction and good biocompatibility, besides biodegradability. 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 study the biodegradation of strontium-doped calcium polyphosphate for bone repair materials.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 pre-osteoblastic cells and decreases bone resorption. In this study, started with the research of Strontium-doped calcium polyphosphate (SCPP), it is included the parts as follows: the preparation condition; the effect of holding temperature time namely polymerization degree and sintering temperature on degradation of SCPP from solution-driven level; obtain the optimal preparation condition. Secondly, cell-driven degradation of SCPP including macrophage cell-driven and osteoclast cell-driven were studied. Finally, implantation experiment into animal was carried to explore the biodegradability of SCPP.In this study, SCPP with different preparation condition were prepared. Chemistry structure of SCPP was studied by IR, and the polymerization degree of SCPP with different holding temperature time was studied by ³¹pNMR. The result of ³¹PNMR showed the polymerization degree of SCPP didn't increase with prolonging holding temperature time. 7 kind of SCPP were obtained by controlling different sintering temperature, XRD showed all these SCPP wereβ-SCPP. SEM showed morphologies changed with sintering temperature, SCPP stintered at 700℃showed compact surface and unclear crystal boundary, while SCPP stintered at 800℃and 900℃showed lacunaris surface and clear crystal boundary.In this study, the effect of holding temperature time namely polymerization degree and sintering temperature on degradation of SCPP from solution-driven level was studied. Results showed the degradation velocity of SCPP didn't decrease with increasing of its polymerization degree. At the same sintering temperature, SCPP, holding temperature time is 5h, degraded the fastest in all. The degradation velocity of SCPP whose holding temperature time is 3h was middle, while SCPP whose holding temperature time is 7h was the last. In the range of SCPP's melt temperature, at the same holding temperature time, the degradation velocity of SCPP increased with increasing of sintering temperature. The degradation velocity sequence of SCPP as follows: 7H900C＞5H800C＞5H700C＞3H800C＞3H700C＞7H800C＞7H700C. Some precipitate formed on the surface of 7H900C, 5H800C and 5H700C and IR showed that the precipitate was a new apatite contended carbonate group. Considered sinter technics and degradation velocity, 5H800C was selected as the optimal preparation condition.In this study, macrophage cell-driven degradation of SCPP and the effect of Sr on the function of macrophage were studied. Results of weight change and ion consistence change showed SCPP degraded faster than CPP in cell group and macrophage accelerated degradation of SCPP compared with simplex SCPP group. ICP showed the quantity of Sr was 10μg in 6w, namely 1×10^-4mmol, which far less than the quantity in body (3.5 mmol), so the quantity of Sr was in the range of normal level. MTT and SEM showed existing of Sr didn't effect the activity and morphologies of macrophage.In this study, osteoclast cell-driven degradation of SCPP and the effect of Sr on the osteoclast were studied, osteoclast cell was identified by TRAP stain, bone lacuna and cell morphology and the cultured method of osteoclast was established. The resorption lacunas quantity and cell quantity of SCPP was less than CPP, which showed degradation velocity of SCPP by osteoclast was slower than CPP. SEM showed cell quantity in CPP group was more than in SCPP group, revealed the existence of Sr decreased multiplication of osteoclast.In this study, implantation experiment into rabbit's cannon bom and dog's thighbone were carried to explore the biodegradability of SCPP in vivo. Masson picture analysis showed in dog group CPP degraded faster than SCPP, while in rabbit group degradation velocity of SCPP in vivo was faster than CPP and far faster than HA, revealed the degradability of SCPP was better than CPP and HA.In this study, biological experiment was simulated in vitro. Degradation of SCPP was studied from solution-driven degradation and cell-driven degradation, moreover degradation of SCPP in vivo was studied. The result of solution-driven degradation showed degradation velocity of SCPP was different at different preparation condition. Cell-driven degradation showed macrophage and osteoclast cell could accelerate degradation of SCPP, however macrophage cell played primary role because Sr restrained multiplication of osteoclast cell. Degradation of SCPP in vivo showed dagradation results were different as different animal, different part and different kinds of cells in biological experiment. In dog group, osteoclast cell played primary role in degradation process so CPP degraded faster than SCPP; while in rabbit group body fluid and macrophage cell played primary role leading SCPP degraded faster than CPP. Considering in vitro and in vivo condition, the dagradation method of SCPP including solution-driven degradation, macrophage cell-driven and osteoclast cell-driven degradation. When body fluid and macrophage cell contributed more to degradation, SCPP degraded faster than CPP, contrarily SCPP degraded slower than CPP.In conclusion, SCPP displayed good biodegradability in this study. This study offered important data to degradation study of SCPP and offered feasibility basis to clinical application of SCPP at the same time.