Papers by Author: Ya Dong Yao

Abstract: Poly-L-lactide/β-tricalcium phosphate (PLLA/β-TCP) porous scaffold fabricated by freeze shrinking/particulate leaching was studied. The scaffold was immersed into simulated body fluid (SBF) for 1, 2, 3 and 4 weeks and analyzed by the SEM, XRD and FT-IR spectroscopy. The ability of inducing Ca-P formation was compared among the scaffolds with different content of β- TCP. SEM shows a typical feature of apatite precipitation. Diffraction peak of new crystal structure was detected by x-ray diffraction (XRD). IR Spectrum in which absorption bands arise from newly formed groups of carbonate apatite can be seen. At the same testing point, higher density of Ca-P crystal can be observed by SEM in scaffold with high content of β-TCP than in low group. Until 3 weeks, Ca-P individual crystal started on the wall of inner pore of pure PLLA. Porous PLLA/β-TCP composite scaffolds also indicate good ability of Ca-P formation in vitro, the ability of which to form apatite was enhanced by addition of each other that has different degradable mechanism.

Abstract: Silicate fireproof coatings for tunnels (FCT) have many eminent properties. But low adhesion strength and poor water/fire-resistance of this kind of materials largely limit its applications. Here we reported a new kind of FCT based on high alumina cement as principle adhesive, redispersible powder as assisting adhesive, ammonium polyphosphate as fire-retardant material, vermiculite as adiabatic padding, and magnesium hydroxide as assisting reagents. The influence of various experimental conditions on fire resistance, adhesion strength and water resistance were carefully studied. Results showed that dispersible emulsoid powder was a key component affecting adhesion strength and water resistance of FCT, whereas fire-retardant material posed significant effects on the fire resistance.

Abstract: Porous biodegradable scaffolds are widely used in bone tissue engineering to provide temporary templates for cellular attachment and matrix synthesis. Ideally, the degradation rate in vivo may be similar or slightly less than that of tissue formation, allowing for the maintenance of the scaffold structure and the mechanical support during early stages of tissue formation. Eventually, the 3-D spaces occupied by the porous scaffolds will be replaced by newly formed tissue. In this work, β-tricalcium phosphate/Poly-L lactide (β-TCP/PLLA) scaffolds with different proportions of β-TCP to PLLA were investigated. The effects of β-TCP proportions on degradation rate and mechanical strengths of the scaffolds were evaluated in simulated body fluid (SBF) at 37°C up to 42 days. Results show that: different proportions of β-TCP to PLLA have significant influence on degradation behaviors of the scaffolds, and mechanical strengths of the scaffolds with weight proportion of β-TCP to PLLA being 2 to 1 are much higher than those of the others during the degradation period. And in this period, the scaffolds biodegrade slowly, and Hydroxyl Carbonate Apatite (HCA) forms in the surface of the material.

Abstract: The ability of apatite to form on the surface of biomaterials in simulated body fluid (SBF) has been widely used to predict the bone-bonding ability of bioceramic and bioceramic/polymer composites in vivo. Porous β-tricalcium phosphate/poly(L-lactic acid) (β-TCP/PLLA) composite scaffold was synthesized by new method. The ability of inducing calcium phosphate (Ca-P) formation was compared in static simulated body fluid(sSBF) and dynamic simulated body fluid (dSBF). The Ca-P morphology and crystal structures were identified using SEM, X-ray diffraction and Fourier transform infrared (FT-IR) spectroscopy. The results showed that the typical features of bone-like apatite formation on the surface and the inner pore wall of β-TCP/PLLA. Ca-P formation on scaffold surfaces in dSBF occurred slower than in sSBF and was more difficult with increasing flow rate of dSBF. The ability of apatite to form on β-TCP/PLLA was enhanced by effect of each other that has different degradable mechanism. Porous β-TCP/PLLA composite scaffold indicates good ability of Ca-P formation in vitro.

Abstract: Merwinite powders were synthesized by a sol-gel process. The bioactivity in vitro of merwinite was investigated by soaking the powders in simulated body fluid (SBF), the growth of hydroxyapatite(HAp) on the surface of the powder was evaluated in various time. It was found that hydroxyapatite was formed after soaking for 14 days. The results indicate that merwinite possessed apatite-formation ability might be a potential candidate biomaterial for hard tissue repair.