Key Engineering Materials Vols. 330-332

Abstract: In this study, CaSiO3 (CS)/Ca3(PO4)2 (TCP) composites with 50% CS and 50% TCP sintered at different temperatures (1100oC, 1200oC and 1300oC) were prepared. The formation of bone-like apatite on CS-TCP composites was investigated by soaking the ceramics in simulated body fluid (SBF), and the presence of bone-like apatite layer on the composite surface after soaking in SBF was determined by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The results showed that the bone-like apatite was formed on all the CS-TCP composites sintered at different temperatures after 7 days of immersion. In addition, the degradation of CS-TCP composites prepared at different temperatures was evaluated by measurement of weight loss of the ceramics in Tris-HCl buffer solution at 37oC, and the results showed that there was no difference in degradation rate between the samples. In vitro cell experiments indicated that the osteoblasts proliferated faster on the CS-TCP ceramics sintered at higher temperature, and cells on the CS-TCP ceramics sintered at 1300oC showed highest proliferation rate. These results provide valuable information for designing CS-TCP composite bioceramics for bone regeneration applications.

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: Hydroxyapatite (HA)-granule-implanted cylindrical titanium composites, which uniformly have HA granules on the curved surface, were formed by a hot pressing using HA-granuleimplantation system under the conditions of 1023 K, 1 h, 1960 N in vacuo. Cracks were not observed in the HA granules. The HA-granule-implanted titanium samples were implanted in a mandible of a dog. After 1 year, new thin bones like pillars were selectively structured on the HA granules with bone induction ability. The HA-granule-implantation technique is expected to be useful for designing shape of bone around titanium implant in order to match living bones.

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: Apatite nuclei were precipitated in the pores of the porous polyethylene matrix in 2.0SBF. Apatite was induced by the apatite nuclei inside the pores and on the surface of the composite and grew to the surface of the composite by a soak in 1.0SBF. The formed apatite showed high adhesive strength to the composite probably due to a mechanical interlocking effect between the matrix and the apatite.

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: In this work, a new kind of bioactive PVA/HA hydrogels use as artificial cartilage were prepared by in situ sol-gel synthesis method. Simulated experiments were performed to evaluate and compare the bioactive ability and properties of the hydrogels in simulated body solution. PVA/HA Cartilage implants were developed and used to repair articular cartilage defect in rabbit knee. The macroscopic and histological observation of animal experiments displayed that the implanted hydrogels combined tightly to ambient tissues, and some bone-like tissue grew into the bottom of the implants from the base-bone to form more deep-set binding.

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: Mercapto group controls the adsorption and release of insulin, which is one of the proteins for enhancing the osteoblast proliferation. Silicon-ion-species were reported to stimulate the bone-forming ability of osteoblasts. The present paper describes doping with mercapto groups and silicon-ion-species in a calcium carbonate/poly (lactic acid) composite membrane, which is prepared by a sol-gel method using 3-mercaptopropyltrimethoxysilane. The membrane was amorphous and showed high flexibility. A quantitative analysis by thiol-disulfide exchange reaction using 2, 2-dipyridyl disulfide reagent showed that the amount of mercapto group existing on membrane surface was estimated to be about 5.51μmol/cm2. A trace amount of silicon-ion-species was released from the membrane after soaking in tris (hydroxymethyl) aminomethane buffer solution at 37 oC. The membrane is expected to have high bone-forming ability.