Mineralization, degradation and osteogenic property of polylactide multicomponent porous composites for bone repair: In vitro and in vivo study.

Gelatin and hydroxyapatite were assembled into polylactide porous matrix to prepare multicomponent porous composites for bone repair (PLA-gH). PLA-gH possessed a superior ability of mineralization. During simulated body fluids (SBF), the spherical Ca-P depositions on surface of PLA-gH became bulk as Ca/P decreased, while they locally turned into the rod with different variation in Ca/P during SBF containing bovine serum albumin (SBF-BSA), indicating that the mineralization of PLA-gH could be regulated by BSA. Meanwhile, PLA-gH possessed good degradation behaviour, especially in SBF-BSA, the degradation of PLA porous matrix was higher than that in SBF after 14-day immersion, whose crystallinity (Xc) decreased to a slightly lower level. Gelatin and hydroxyapatite endowed PLA-gH with good osteogenic property, characterized by obvious osteogenic differentiation and bone regeneration. In terms of predicting the cytocompatibility, osteogenic differentiation and new bone mineralization of PLA-gH by in vitro methods, applying SBF-BSA may be more reliable than SBF.

Porous bioceramics reinforced by coating gelatin.

Porous bioceramics with high porosity for bone tissue engineering were fabricated by the foam impregnation technique, but their mechanical strength was poor, only a mean compressive strength of 1.04+/-0.15 MPa and an mean elastic modulus of 0.1 GPa. In order to reinforce porous ceramics, the ceramic samples were immersed in 5% gelatin solution and gelatin coatings were formed on the inter-surface of their pores. It was found that the mean compressive strength value and the mean elastic modulus value of porous samples coated with gelatin were improved to 5.17+/-0.17 MPa and 0.3 GPa respectively without sacrificing their porosity greatly. Moreover composite samples were not as fragile as sintered ceramics. The results indicated that the gelatin coatings on the inter-surface of pores reinforced porous bioceramics effectively.

[Study on hydroxyapatite porous scaffold bonded by phosphates and its biocompatibility].

The porous scaffolds for bone tissue engineering were prepared by foam impregnation. The magnesium and aluminum acid phosphates were used as bonder and the hydroxyapatite ((Ca10 (PO4)6(OH)2, HA) powder as raw materials. Scanning electron microscopy (SEM) examination indicated that the 3D interconnected porous structure of the organic foam was replicated well by the scaffolds calcined at high temperature and the structural requirement of tissue engineering was satisfied. XRD analysis showed that the scaffold was composed of HA and Ca7Mg2P6O24 while calcined at 1150 degrees C for shorter time and of (Ca, Mg)3(PO4)2 when the time prolonged to 2 h. There was no peak of CaO found in the scaffolds by XRD. According to the culture in vitro, the scaffold possesses good biocompatibility and certain degree of degradability.

[Relationship between the vertical loop structure and the mechanical properties.].

PURPOSE: The relationship between vertical loop structure and its mechanical properties was investigated in order to provide reference data for more proper use of vertical loop. METHODS: According to the acting manner in use, finite elements model of vertical loop was established and the finite elements software ANSYS was used to simulate the mechanical characteristics of the loops. The simulated data were summarized at the end. RESULTS: The force and moment decreased with the increase of arm length, height and arc radius of the loop. The ratios of force to moment (M/F) decreased with the increase of arm length, but increased with the increase of height and arm radius. When the interval between the vertical arms enlarged, the force and moment rose and the M/F did not vary significantly. CONCLUSION: To satisfy the requirement of individual patient, the structure of loop can be adjusted properly to output mediate force, moment and M/F value.

[Stress analysis of separators with different specifications].

OBJECTIVE: To evaluate the shape and structure of different separators affecting the mechanical behavior. METHODS: The stress of different separators was analyzed by ANSYS software. Various separators were meshed into one-dimensional solid elements and the material character parameters were inputted. The loads were added gradually. RESULTS: The stress was related to the arm of force and the point of force application. CONCLUSIONS: The force applied can be controlled by selecting different separators.