Papers by Author: Yu Bao Li

Abstract: To well understand the influence of the sterilization on the properties of biomaterials prior to application is pivotal. The effect of γ-ray irradiation on the mechanical and thermal properties of nanohydroxyapatite/polyurethane (n-HA/PU) porous scaffold for bone tissue engineering was studied in this paper. The mechanical testing, fourier transform infrared spectroscopy and thermal analysis were employed to determine the structure and properties change of these composite scaffolds after γ-ray irradiation with different doses.The results show that thermal stability, and mechanical properties of the composite scaffolds increase after γ-ray irradiation with doses of15 kGy to 25 kGy, especially the irradiation dose of 15kGy which imposed a remarkable effect on these properties. However, a reverse trend is found when the 50kGy irradiation dose was applied.In general, it can be concluded that sterilization using γ-ray irradiation with proper dose has no adverse effect on the properties of n-HA/PU composite scaffolds.

Abstract: Elimination of the residual microorganisms from an infectious bone defects and the prevention of subsequent re-infection are of importance for chronic osteomyelitis treatment. The application of bone repair materials with antibacterial properties in such a condition has advantages. The present study reported a novel method to fabricate nanohydroxyapatite/polyurethane (n-HA/PU) based antibacterial porous scaffolds through immobilization "core-shell" silver-based mesoporous silica particles (Ag@SiO₂), i.e., silver nanoparticle as core and mesoporous silica as shell, on the surface of n-HA/PU scaffold. The samples were characterized by Scanning Electron Microscope (SEM) and antibacterial tests. The results revealed that the Ag@SiO₂ nanoparticles distributed uniformly on the surface of n-HA/PU porous scaffold. The Ag@SiO₂ could been kept on the surface of n-HA/PU porous scaffold more than 2 weeks, resulting in long-lasting the release of silver ions and antibacterial ability. The porous n-HA/PU scaffolds with an antibacterial surface may hold promise to be used in infectious bone defects repair.

Abstract: The novel tourmaline/chitosan (Tur/CS) composite fibers were successfully prepared by solution spinning method. The fibers had the diameter of 200-300μm.Tur particles were distributed evenly inside the composite fibers. The crystal structure of CS was not remarkable changed except of the crystallinity decreasing. Then L929 cells were co-cultured on the composite fibers to access the cytotoxicity in vitro.Suitable mass ration of Tur/CS composite fibers were found to be the most promising matrix for the attachment and spreading of the L929 cells. This novel fiber can be used as potential wound dressings for skin regeneration.

Abstract: Elimination of microorganisms from the root canal system and the prevention of subsequent reinfection are of importance for long-term endodontic treatment. The application of a sealer with antibacterial properties may reduce the reinfection and improve the success rate of the root filling treatment. The aim of this paper is to evaluate the antibacterial properties of a novel root canal sealer based on injectable self-curing polyurethane with silver phosphate (PU/Ag₃PO₄). The antibacterial abilities were assessed by direct contact test, anti-bacterial adhesion assay and bacteriostatic rate test. The results show that the fabricated PU/Ag₃PO₄ sealer can completely inhibit the bacterial growth and prevent bacterial adhension effectively. The bacteriostatic rate is 93.6% and 98.1% when the bacteria incubated with PU/Ag3PO4 sealer for 7 and 24h respectively. The strong antibacterial abilities suggest that PU/Ag3PO4 sealer has great application potential in the field of root canal filling.Key words: Root canal sealer, polyurethane, silver phosphate, antibacterial properties, direct contact test

Abstract: The glycerides of castor oil (GCO) were copolymerized with isophorone diisocyanate (IPDI) to generate glyceride-based polyurethane (GCPU), meanwile blending with hydroxyapatite (HA) powder to fabricate porous composite scaffolds. The effect of HA content on mechanical properties of the resulting polymer scaffolds and the in vitro cell response of HA/GCPU scaffolds were investigated, by use of mechanical testing, FTIR, SEM and MTT assay. The results showed that the compressive strength increased with HA content, and the HA/GCPU scaffold with 40 wt% HA reached about 4.6 MPa, much higher than the scaffold without HA (only 605 kPa). The SEM observation, live-dead staining assay and MTT assay demonstrated the excellent biological properties of HA/GCPU scaffolds, which support cell adhesion and proliferation. This novel class of HA/GCPU porous scaffolds have prospect and advantage for bone repair and regeneration.

Abstract: In this paper, isoniazid (INH)-loaded poly (ε-caprolactone) microspheres with a special microporous surface and relatively high drug loading were fabricated by an oil-in-oil (O/O) solvent evaporation method. Meanwhile the microspheres were produced by an oil-in-water (O/W) method for comparison. The technological parameters such as the concentration of surfactant, the volume of continuous phase and the quantity of the drug were investigated systematically. The microspheres morphology, their size distribution and the viscosity of both the dispersed and continuous phase were characterized. The results indicate that the O/O solvent evaporation method is a feasible approach to encapsulate micromolecular and hydrophilic drugs in PCL. This opens the door for INH-loaded microspheres able to release drugs and thereby improve the therapy of tuberculosis of bones and joints in the future.

Abstract: Acicular nano-hydroxyapatite (n-HA) was used to make a new biomaterial composite with polycarbonate by a novel technique. The physical and chemical characteristics of the composites were tested. It was found that the synthesized n-HA crystals were similar to bone apatite in size, phase composition and crystal structure. The TEM results indicated the biomimetic n-HA crystals were uniformly distributed in the polymer matrix. Chemical inter-action between inorganic n-HA and polycarbonate was investigated and discussed. These results indicate that the composite fulfills the basic requirement of bone substitute material, and has the potential for clinical applications.

Abstract: High-purity aluminum oxide is potentially an attractive implante material for total hip joint replacement, because its biocompatibility, excellent wear resistance, high strength and corrosion resistance. The main problem of alumina is relatively low fracture toughness. Thus, this study is the introduction of ZrO2 as second ceramic phase homogeneously dispersed wihtin an alumina matix. Al2O3/ZrO2 nanocomposites disk is prepared by spark plasma sintering (SPS) method at 1500°C and 50MPa, in vacuum for 5min. Then, X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to analyze the microstucture and phases of this nanocomposite. Moreover, frexual sthrength of the nanocomposites was meausured as well as hardness and fracture toughness. When the content of ZrO2 is up to 15wt%, the fracture toughness value (8.4MPam1/2), and strength (527MPa) are achieved. This Al2O3/ZrO2 nanocomposites may be served as a tatal hip joint replacement.

Abstract: Nano-hydroxyapatite (n-HA)/chitosan (CS)/konjac glucomannan (KGM) composite was prepared by integrating composition and molding. Then, X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to analyze the physical, chemical and degradable properties of the composite before and after in simulated body fluid (SBF). Moreover, study in vitro test for drug delivery revealed that the amount of released pentoxifylline (1-[5-oxohexyl]-3,7-dimethylxanthine)(PTX) reached a plateau and equaled 80% of the drug loaded in an implant. The newly develop n-HA/CS/KGM composite may serve as a good degradable biomaterial for implantable drug delivery system (IDDS) in bone tissue engineering.

Abstract: In the paper, ampicillin-loaded alginate(ALG) microspheres covered with chitosan (CS) were firstly prepared by emulsification/internal gelation method. These microspheres were mixed with n-HA/CS composite and then were fabricated into porous scaffold carrying micropheres by gas-foaming together with phase-separation. their properties were characterized by the methods of scanning electronic microscopy (SEM), X-ray diffraction (XRD), infrared spectroscopy (IR) and inversed microscope. The drug releasing rate and entrapment efficiency were tested by spectrophotometry at 203 nm. The results show that the porous scaffold carrying microspheres has good property of slow drug releasing rate. The research will offer a new kind of degradable porous scaffold with good property of controlled drug release for bone or cartilage repairing.