Key Engineering Materials Vols. 330-332

Abstract: Circumambient tissues infection is a common complication of implanted percutaneous and permucosal devices (PDs). In order to counter the infection, the titanium abutment surface of PDs was modified to achieve antibacterial and antiadhesive activities. Titanium discs were immersed into hydroxyapatite (HA) sol containing different mass fraction silver and thermally treated to get modified discs. The modified discs become more smoother and get crystal HA coatings containing silver. Silver ion release test demonstrate the release rate is very slow and the coating is a reservoir of silver. The antibacterial and antiadhesive effects of modified discs on Staphylococcus aureus and Porphyromonas gingivalis were evaluated. Modified titanium discs with silver significantly inhibited the growth of these two bacteria compared with both the polished titanium discs control and modified titanium discs without silver. And titanium discs modified with more silver have higher antibacterial activity and less bacteria adhesion in this study. These findings indicate that titanium surface modified with the HA sol-gel containing silver could achieve antibacterial and antiadhesive activities, and the abutments of PDs are promising to be modified by this method.

Abstract: Based on the molecular recognition theory, an organic molecules model was designed to induce the hydroxyapatite crystallization, to build a tooth-like calcium phosphate/hydroxyapatite under a controllable way in vitro. The cross-linking of collagen on the dentin surface and gelatin was optimized by varying the molar ratio of N,N-(3-dimethylaminopropyl)- N'-ethyl-carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) at a constant EDC concentration. CaCl2 and Na3PO4-12H2O solutions were added after the crosslinking process. The whole process requires repeating the crosslinking and mineralization process for five times. The obtained composite were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) as well as energy dispersive X-ray photoelectron spectroscopy (XPS). The results showed that the dentinal tubule were blocked by neonatal hydroxyapatite layer which has a continuous structure of columns crystal with size of 10-40nm. Furthermore, there was column crystal with parallel direction inside, similar to the crystal array in the top of enamel rod. This study showed that the specific organic molecule model can be used as a potential effective crystal growth modifier.

Abstract: Heating reduces the amount of Ti-OH groups in the surface layers that are considered to favor apatite nucleation. Thus, low temperature processes are developed to fabricate bioactive titania. Anatase/rutile dual layers were deposited on titanium substrates when they were soaked in TiOSO4/H2O2 solution at low temperature, and than aged in hot water, which can induce apatite formation in DMEM. The resulted titania layers have apatite-forming ability. The organic molecules in DMEM medium had reduced the apatite formation on as-treated substrates in some measure.

Abstract: The PCL plates hydrolyzed by NaOH aqueous solutions and carboxylate groups were introduced onto the surfaces of specimen. Specimens were treated by CaCl2 and K2HPO4⋅3H2O under the normal-pressure condition and low-pressure of 103 Pa condition for 30min separately. Dense and uniform bone-like layers could be formed on the surface of specimens after mineralizing for less than 24h in simulated body fluids (SBF). The low-pressure condition could accelerate the formation of apatite layer.

Abstract: Apatite-polymer hybrids are expected as novel bone substitutes exhibiting bone-bonding ability and mechanical performances analogous to those of natural bone. In this study, we attempted preparation of organic-inorganic hybrids from different pectins such as pectic acid, apple-derived pectin and citrus-derived pectin through apatite deposition in simulated body fluid (SBF). Pectin gels were prepared by CaCl2 treatment of aqueous solutions of pectin. Apatite-forming ability of the gels was examined in SBF. The citrus-derived pectin showed tendency to form the largest amount of the apatite in SBF.

Abstract: Rutile films were deposited on polyethylene terephatalate (PET), polytetrafluoroethylene (PTFE), Silicone, poly6-caprolactam (Nylon6), polyhexamethylene adipamide (Nylon6,6) and Nylon fiber substrates using 0.03 M TiOSO4 and 0.03 M H2O2 aqueous solution at 80°C for 24 h. The rutile films exhibited excellent in vitro bioactivity as they induced apatite deposition in a simulated body fluid (SBF).

Abstract: Development of the organic-inorganic hybrids composed of apatite crystals and organic polymer is expected to be an attractive material that has mechanical properties similar to natural bone as well as bone-bonding ability, i.e. bioactivity. It is reported that the carboxyl groups (-COOH) on the surfaces of the organic substrates act as a catalyst for induction of heterogeneous nucleation of apatite. The present authors previously showed that the apatite was successfully deposited on the polyglutamic acid gels containing abundant carboxyl groups through the biomimetic process, when they were priorly treated with calcium chloride solution. In this study, we fabricated the polyglutamic acid gels with different degree of cross-linking. Effect of the cross-linking on their ability of the apatite formation was examined in simulated body fluid (SBF). It was suggested that the apatite deposition on the polyglutamic acid gels is governed not only by the amount of –COOH that induces the heterogeneous nucleation of the apatite, but also by swelling property that controls local increase in degree of supersaturation with respect to the apatite.

Abstract: Rutile films were deposited on poly-l-lactide (PLLA) substrates using 0.5 M titanium tetrachloride aqueous solution at 40 °C for 72 h. The rutile films exhibited excellent in vitro bioactivity as they induced apatite deposition in a simulated body fluid (SBF) within 3 days. This simple treatment provided an effective route to synthesize bioactive and biodegradable scaffolds.

Abstract: A FGF-2-apatite composite layer (FGF-AP layer) was formed on the surface of Ti screws in a supersaturated calcium phosphate solution supplemented with FGF-2. By an in vitro study using fibroblastic NIH3T3 cells, it was confirmed that FGF-2 was immobilized in the layer without complete denaturation although the composite layer was formed at 37°C. When Ti screws with the FGF-AP layer were percutaneously implanted in the proximal tibial metaphysis of 16 rabbits, no osteomyelitis was observed in any rabbits although a FGF-2-free AP layer allowed osteomyelitis in some cases in our previous study. These results suggest that a FGF-AP layer formed on Ti screws is useful for resisting bacterial infection during external fixations.