Papers by Author: Min Qi

Abstract: New biodegradable Fe-Zn alloys with different concentration of zinc were prepared by electroforming in this paper. The composition, phase and microstructure of the Fe-Zn alloys were investigated by EDX, XRD and SEM, respectively. The potentiodynamic polarization and static immersion test were used to evaluate the in vitro biodegradation properties of these alloys. The results revealed that the alloys consist of single-phase Fe-Zn solid solution and have a better degradation property than pure iron, which make it a potential material used for bioabsorbable endovascular stent.

Abstract: Sponge-like scaffold with a specific three-dimensional structure resembling the actual extracellular matrix of a particular tissue show significant potential for the regeneration and repair of damaged anisotropic tissues. In this research, an oriented microtubular P34HB scaffold was prepared successfully. The mechanical property showed that anisotropy of modulus is much greater than a typical non-oriented scaffold. Altering the P34HB concentration allowed P34HB scaffolds to be produced with complex pore orientations, and anisotropy in pore size and alignment.

Abstract: A porous titania (TiO₂) coating with vermiform slots was prepared on the Ti substrate through micro-arc oxidation (MAO) treatment using sodium tetraborate as electrolyte. Morphologies and phase structure were analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. Results show that the rutile phase increases and anatase decreases gradually with increasing MAO time. The electrolyte of sodium tetraborate has significant influence on the formation of vermiform coatings, which determine the corrosive patterning in the first stage during MAO processing. The evolution of vermiform morphology is proposed as followed: some corrosive pores appear on the surface before arcing; afterward, the adjacent micropores in the dense regions link each other due to the high temperature result from continuous arc action; then, the micropores grow up to big pits and combine with each other with increasing MAO treating time; finally, the vermiform morphology forms on the surface of Ti metal.

Abstract: Recently, Graphene oxide (GO) has attracted enormous interests due to its extraordinary properties. GO sheets are expected to find a variety of applications, such as GO-based composites materials and biotechnology. The nanocomposites of Poly (ε-caprolactone) (PCL) and graphene oxide (GO) were successfully synthesized by in-situ polymerization. WAXD indicated that the PCL/GO composites formed an exfoliated structure. And Polarized Optical Image (POM) showed that the graphene oxide could be homogeneously dispersed in matrix. What’s more, we also studied the crystallization behavior of the pure PCL and PCL/GO nanocomposites as well as the effects of graphene oxide as the nucleation agent.

Abstract: Fatigue durability is an important attributes of cardiovascular stent. This paper develops a stent fatigue test instrument. And then a fatigue test for cardiovascular stent is carried out successfully with this stent fatigue test instrument. The test result shows that the stents tested still maintain integrity after 400 mio fatigue cycles --corresponding to about 10 years. This paper can provide the guidance for the stent design.

Abstract: To eliminate the risk of late and very late stent thrombosis of permanent polymer stent, a polymer-free stent direct drug-loading by micropores is developed. To evaluate the safety of micropores stent, fatigue test for micropores stent is carried out. The result is that micropores stent still maintain integrity and has no difference found in comparison with the initial state after 400 mio fatigue cycles --corresponding to about 10 years. The result proves that the fatigue durability of micropores stent is safe, which may help to promote the use of polymer-free stent direct drug-loading by micropores.

Abstract: The novel biodegradable poly (ε-caprolactone)/TiO₂ nanocomposites were prepared by in situ polymerization of ε-caprolactone in the presence of modified-TiO₂ nanoparticles as initiator. The molecular weight of poly (ε-caprolactone) (PCL) matrix was dependent on the amount of the TiO₂ fillers. The incorporation of TiO₂ did not significantly affect the crystalline structure of PCL. An astounding nucleating effect of TiO₂ on PCL crystallization was observed. The enhanced thermal stability of PCL nanocomposites was observed. The novel biodegradable poly (ε-caprolactone)/TiO₂ nanocomposites were prepared by in situ polymerization of ε-caprolactone in the presence of modified-TiO₂ nanoparticles as initiator. The molecular weight of poly (ε-caprolactone) (PCL) matrix was dependent on the amount of the TiO₂ fillers. The incorporation of TiO₂ did not significantly affect the crystalline structure of PCL. An astounding nucleating effect of TiO₂ on PCL crystallization was observed. The enhanced thermal stability of PCL nanocomposites was observed.

Abstract: A new poly(ester amide)s (PEA) derived from L-lactic acid and α-alanine have been synthesized by melting copolymerization with p-toluenesulfonic acid (TSA) with stannous chloride (SnCl₂) as catalyst. The products were analyzed by NMR, FT IR techniques. The effects of the content of α-alanine (L-Ala) on the copolymers structure were studied. Being the phosphate buffered saline (pH=7.2) as the degradation solution, the degradation rate speed up with the increasing the content of the α-alanine.

Abstract: In order to improve the osteoblast growth and bacteria resistance, Zn-containing hydroxyapatite (Zn-HA) and titanium oxide (TiO₂) composite coatings were prepared to improve binding between coating and Ti substrate. TiO₂ film was prepared on the surface of Ti by micro-arc oxidation (MAO) and Zn-HA coating was deposited on TiO₂ using sol–gel technique. Phase structure, composition and microstructure of the surface coatings were analyzed by X-ray diffraction (XRD) and Energy Dispersive Spectrometer (EDS), respectively. The adhesion strength between the coatings with different Zn content was measured by tensile testing. The results showed that there was no significant influence of Zn content on adhesion strength between coating and Ti substrate.

Abstract: PLGA blend and gradient films were designed and prepared to improve the late degradation properties of PLGA films. The gradient films were composed of gradual components of PLGA50/50 and PLGA 75/25, and PLGA 50/50, featuring gradual descents from outside parts to inside parts of the films. Degradation processes of biodegradable PLGA blend and gradient films were also predicted by Monte Carlo simulation to understand the mechanism of degradation. The simulation results indicated that the gradient structure prolonged the mass transfer time of the degradable films, and it induced smoother weight loss than single-component or blend films. The degradation behaviors of single-component, blend and gradient films were experimentally investigated to prove the validity of the models by immersing them into PBS. The experiment indicated that the gradient films have the most stable weight loss curves, which were in well accordance with the simulation by Monte Carlo method.