Papers by Author: Yu Bao Li

Abstract: Scaffold in bone tissue engineering must have a three-dimensional (3-D) interconnected porous structure acting as a template for bone tissue regeneration, and material fabricating the scaffold must be biocompatible and can provide structural support during bone growth and remodeling at the same time. In this paper, a method of phase separation and particle leaching combined (PS/PL) was used to prepare porous scaffold of nano-hydroxyapatite and polyamide6 (n-HA/PA6) composite. The results show that the scaffold prepared by PS/PL has not only interconnected macropores of 100~300 μm, but also micropores on the walls of macropores, and PS/PL scaffold is more interconnective in compare with phase separation (PS) scaffold. When the porosity of the scaffold is about 79%, its compressive strongth is about 3.27 MPa, that is similar to the human cancellous bone(2~10MPa). Ethanol has some effect on hydrogen bonds, but fabricating method will not change the chemical component of the composite. The porous scaffold is prospect for bone tissue engineering.

Abstract: A novel nano-hydroxyapatite/chitosan (n-HA/CS) composite scaffold with high porosity was developed by a new method of emulsion-foaming/freeze-drying process and was characterized by means of infrared spectroscopy (IR), scanning electronic microscopy (SEM) and universal material testing machine. In addition, the porosity and density of the scaffold were also calculated. IR result shows that the characteristic absorption peaks belonging to both CS and HA are present in their composite, and the slight band-shifts and peak-decrease suggest that some interactions have taken place between the two phases of CS and n-HA in the composite. SEM photo displays that, with the dosage increase of Tween-80, the prepared scaffold shows highly porous and interconnected structure, in which macropores and micropores coexist. The calculated data demonstrate that the porosity of the scaffold is proportional to the content of the emulsifier, while the compressive strength is inversely. When 15wt% emulsifier used, the porosity of the scaffold can be up to 90% and the density is 0.453g/cm3, while the corresponding compressive strength is about 2.4MPa. The newly developed n-HA/CS composite scaffolds may serve as a good 3-D substrate for cell attachment and migration in bone tissue engineering.

Abstract: Nano-hydroxyapatite/polyamide66/chitosan composite (n-HA/PA66/CS) was prepared by a co-precipitation method and porous scaffolds from n-HA/PA66/CS composite were prepared by means of porogen–leaching method and were characterized by SEM, IR, XRD and universal mechanical testing machine. IR and XRD analyses showed that some chemical bonds existed between n-HA and polymers. Furthermore, macroporous structure of the scaffolds and mechanical strength were tested with a changed ratio of porogens (PVP/NaCl). When the ratio of PVP and NaCl is1: 6, the scaffold processed highly porosity and the pores were interconnected. The compressive strength of the scaffold, can meet the requirement of tissue regeneration.

Abstract: The aim of this study was to evaluate the remineralizing potential of demineralized human dentin treated with Y/HA nanoparticles (doping Y with 5mol %) and HA nanoparticles suspension and whether dentin could be remineralized by HA. Human crown dentin was demineralized with EDTA for 4 hours, and then subjected to remineralization condition. The ability of these matrices to remineralize was determined by SEM, AFM and calcium levels in the remineralized tissue were measured by atomic energy spectrum analysis. The results showed that Y/HA and HA nanoparticles remineralized the demineralized dentin surface; these demineralized matrices treated with Y/HA nanoparticles remineralized to a greater extent than those treated HA nanoparticles. The differences in both the quality and quantity, as defined by Yttrium iones leading to changes in characterization of the apatite crystals might be important in effecting the ability of this tissue to remineralize. This work suggested that apatite nanoparticles caused remineralization of dentin and the yttrium ions substituted in the apatite structure might enhance their remineralization potential.

Abstract: A unique composite consisted of nano-hydroxyapatite (n-HA), poly (vinyl alcohol) (PVA) and gelatin (Gel), was prepared and characterized by Fourier transform infrared absorption spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and burning test. The homogenicity of the composite was evaluated, and the presence of interior chemical bond was confirmed and discussed. Mechanical strength and water absorption of the prepared composite were investigated, respectively. The results show that n-HA/PVA/Gel composite has good homogeneity, similar mechanical properties to natural cartilage and excellent in vivo biocompatibility.

Abstract: Nano-hydroxyapatite/polyamide66/chitosan composite (n-HA/PA66/CS) was prepared by a co-precipitation method, and was characterized by TG/DTG, TEM, IR, XRD and Universal mechanical testing machine. TEM test showed that some rod like crystals were formed and distributed uniformly into polymer matrix, with a size of about Φ30nm×80nm. IR and XRD analysis showed that some chemical bonds and electrostatic interaction existed between n-HA and polymers. TG/DTG curves indicated that the composites possessed a talent of high heat-resistance. The compressive strength of composite changed with different content of three compounds, the maximum compressive strength of composite (70MPa) could be acquired.

Abstract: This study was focused on evaluating the bactericidal and anti-adhesive efficacy of silver-hydroxyapatite/ titania nanocomposites (nAg-HA/TiO2) coating on titanium against oral bacteria. Porphyromonas gingivalis, Prevotella intermedia and Fusohacterium nucleatum and Streptococcus mutans were used. Antibacterial activity of nAg-HA/TiO2 coating was investigated quantitatively using film applicator coating method and titanium plates incubated with bacteria were prepared for SEM to observe the adherence of oral bacteria. The viability of each type of bacteria on the antibacterial film was suppressed to about 10% after anaerobic incubation for 3 hours. Image of SEM demonstrated that bacteria on sandblasting surfaces were relatively confluent whilst on coated surfaces fewer bacteria were observed. Adherence of bacteria on nAg-HA / TiO2-coated surfaces compared with uncoated surfaces was remarkably decreased.

Abstract: In the present in vitro study, osteoblasts proliferation, vitality and ultrastructure were investigated when cultured in the presence of silver-hydroxyapatite/titania nanoparticles (nAg_HA/TiO2) compared to HA nanoparticles (nHA) at various concentrations and cell culture without nanoparticles for up to 120 hours. Results confirmed the detrimental influences of both nAg_HA/TiO2 and nHA on osteoblast growth.Cell vitality was slightly higher during the earlier 24h, but after that was inhibited. Both cell proliferation and vitality by addition of nanoparticles were restricted with concentrations of nanoparticles increasing. However, the respiration rates by addition of nanoparticles were showed higher than that of the cell culture without nanoparticles. No remarkable ultrastructure changes were showed in the osteoblasts exposed nanoparticles. The difference in cell proliferation, vitality and ultrastructure between nAg_HA/TiO2 and nHA were insignificant. It was demonstrated that biocompatibility of nAg_HA/TiO2 is almost the same as nHA.

Abstract: Nano-hydroxyapatite/polyamide66 (n-HA/PA66) composite scaffolds are prepared using phase separation and phase separation in combination with particle leaching, and both the composite powder and paste are used as starting materials. The composite is characterized by IR and XRD. The micro-architecture of the scaffolds is observed by SEM, and the mechanisms that the formation of the porous structure follows have been investigated preliminarily. The results show that scaffold prepared by phase separation in combination with particle leaching method using composite powder as starting material possesses controllable porosity and interconnectivity, as well as good mechanical strength comparable to human cancellous bone, suitable for being the tissue-engineered scaffold for load-bearing bone repair. Furthermore, scaffold made by phase separation using composite paste as starting material exhibits an anisotropy both in morphology and mechanical properties, which indicates the potential of guiding cell seeding, distribution and new tissue formation in preferential direction.