Guang Fu Yin

Preparation of Merwinite with Apatite-Forming Ability by Sol-Gel Process

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.

Preparation of Nano-Ag Particles and Antibacterial Dope Loaded Silver

The nano-size silver particles were prepared in polymer-protecting colloidal dispersion with silver nitride as the raw material, hydrazine hydrate as the reduction reagent and polyvinyl pirrolidone (PVP) as the protective solvent. The optimal conditions for the preparation process were studied experimentally as well. The influences from main factors, such as Ag+ concentration and ratio of hydrazine/AgNO3, on the particle size, appearance shape, particle aggregation condition and size distribution of nano-silver particles were also investigated. The results showed that the size of Ag particles prepared in this polymer-protecting system is less than 50 nm, and PVP can reduce the growing tendency of nano-size silver particles. Meanwhile, the antibacterial dope loaded nano-silver particles were prepared by wetting agent, dispersant, defoamer, etc. The antibacterial and bacteriostatic effects of the dope with or without nano-silver particles were tested with bacilli as the tested bacteria. The experiment results showed that the dope loaded nano-silver particles are of high practicality. Its antibacterial ratio is also up to 91.9% in one hour when the added dosage of nano-silver is 0.02%.

The Influence of Titanium Particles Size on Bone Marrow Mensenchymal Stem Cells Viability

The decrease in bone mass caused by wear debris-induced osteolysis could have been compensated through osteoblasts secreting enough new bone matrix. However, the normal osteoblastic population depends on the regular differentiation of their progenitor cells, the bone marrow mesenchymal stem cells (BMSCs). It is not possible to predict whether wear particles will affect the BMSCs’ viability, and subsequently their differentiation. Furthermore, little is known about the extent to which the sizes of the wear particles loading can impact the viability the most. This study has, therefore, concentrated on the potential mechanism for rat BMSCs’ (rBMSCs) viability influenced by different-sized titanium particle (Ti) loading in vitro.rBMSCs were harvested and loaded with circular Ti particles having three different mean diameters, 0.9, 2.7 and 6.9 .m respectively. The results showed that different-sized titanium particles all inhibited rBMSCs’ proliferation and induced rBMSCs’ apoptosis response , but this influence varied with the size of the Ti particles, their concentration and the duration of loading. The smallest Ti particles (0.9.m) exhibited the earliest and largest suppression on the proliferation and the most powerful induction on the apoptotic response of rBMSCs. qRT-PCR analysis demonstrated that those apoptotic effects were association with the abnormal accentuation of inducible nitric oxide synthase(iNOS) activity. The size of titanium particles generated through wear of a prosthetic device and the osteoblastic progenitor BMSCs may be both important considerations in the development of superior implant technology.

Effects of Mechanical Stress on the In Vitro Degradation of Porous Composite Scaffold for Bone Tissue Engineering

In bone tissue engineering, porous scaffolds served as the temporary matrix are often subjected to mechanical stress when implanted in the body. Based on this fact, the goal of this study was to examine the effects of mechanical loading on the in vitro degradation characteristics and kinetics of porous scaffolds in a custom-designed loading system. Porous Poly(L-lactic acid)/β-Tricalcium Phosphate (PLLA/β-TCP) composite scaffolds fabricated by using solution casting/compression molding/particulate leaching technique (SCP) were subjected to degradation in simulated body fluid (SBF) at 37°C for up to 6 weeks under the conditions: with and without static compressive loading, respectively. The results indicated that the increase of the porosity and decrease of the compressive strength under static compressive loading were slower than that of non-loading case, and so did the mass loss rate. It might be due to that the loading retarded the penetration, absorption and transfer of simulated body fluid. These data provide an important step towards understanding mechanical loading factors contributing to degradation.

Degradation of Surface Modified β-TCP/PLLA Porous Scaffold In Vitro

Degradation of surface modified β-tricalcium phosphate (β-TCP) and poly L lactic acid (PLLA) composite scaffolds were investigated in vitro. Bending and compressive strengths were tested by electromechanical universal material testing machine. Molecular weight changes of lactic acid during degradation were measured by gel permeation chromatography (GPC). Phase composition of the surface after soaking was analyzed by Fourier transform infrared ray (FTIR). The surface and cross section of scaffold samples after degradation were observed by Scanning electron microscope (SEM).The results show that degradation speed can be controlled by adjusting the ratio of β-TCP to PLLA in the composite. PLLA can compound more closely with surface modified β-TCP than with non-modified one. The final compressive strength and bending strength of the scaffolds reach 7.11MPa and 2.20MPa respectively, which satisfies the need for bone tissue engineering scaffolds in clinic applications.

Improved Principal Component Analysis on the Comprehensive Hemocompatibility Evaluation of Biomaterials

Hemocompatibility of a biomaterial is determined by the interactions between its surface and blood. Due to the complicated action mechanism, various effective ways and the multiple affective factors of the hemocompatibility, a comprehensive evaluation needs to be built instead of single index. Therefore, the platelet consumption ratio of 10 kinds of biomaterials including Ti6Al4V-TiC-DLC gradient coat material was studied based on image analysis method. Combined with the kinetic clotting time and the hemolysis ratio, the comprehensive hemocompatibility evaluation of the material is carried out based on the improved principal component analysis. First, linear transformation of negative index is carried out. Second, index is under a dimensionless using the logarithmic treatment, then to acquire all variants’ principal component and their characteristic vectors. Finally, comprehensive evaluation index of hemocompatibility is constructed. The improved principal component analysis avoids the effect of correlativity among indexes during anaphase evaluation, and can more correctly maintain the original information of indexes. Thus, the research provides a new idea to the comprehensive evaluation of Hemocompatibility.

Preparation of β-Calcium Metaphosphate (β-CMP) Whiskers

To increase the mechanical properties of PLA used for fracture inner fixation, β-calcium metaphosphate whiskers were prepared by controlled crystallization in the glass. The factors influencing the morphology of the samples, such as component, time and temperature of crystallization were discussed. Results showed that the high quality of β-calcium metaphosphate whiskers can be obtained by crystallization treating for 36 hours and washing for 48 hours at 80°C distilled water. β-calcium metaphosphate whiskers having high aspect ratios of 20-100 with diameters of 1-5μm were achieved at the optimized conditions.

A Study of Bone-Like Apatite Formation on β-TCP/PLLA Scaffold in Static and Dynamic Simulated Body Fluid

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.

Design and Properties of Fire-Proof Coating for Tunnels

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.

In Vitro Degradation of β-TCP/PLLA Scaffolds with Different Proportions of β-TCP

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.