Long Bai

Highly ordered Ni-Ti-O nanotubes for non-enzymatic glucose detection.

Anodization is used to fabricate Ni-Ti-O nanotube (NT) electrodes for non-enzymatic glucose detection. The morphology, microstructure and composition of the materials are characterized by field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HR-TEM) and X-ray photoelectron spectroscopy (XPS). Our results show amorphous and highly ordered NTs with diameter of 50nm, length of 800nm, and Ni/Ti ratio (at %) of 0.35 can be fabricated in ethylene glycol electrolyte supplemented with 0.2 wt.% NH4F and 0.5 vol.% H2O at 30°C and 25V for 1h. Electrochemical experiments indicate that at an applied potential of 0.60V vs. Ag/AgCl, the electrode exhibits a linear response window for glucose concentrations from 0.002mM to 0.2mM with a response time of 10s, detection limit of 0.13μM (S/N=3), and sensitivity of 83μAmM(-1)cm(-2). The excellent performance of the electrode is attributed to its large specific area and fast electron transfer between the NT walls. The good electrochemical performance of the Ni-Ti-O NTs as well as their simple and low-cost preparation method make the strategy promising in non-enzymatic glucose detection.

Fabrication of Ni-Ti-O nanotube arrays by anodization of NiTi alloy and their potential applications.

Nickel-titanium-oxide (Ni-Ti-O) nanotube arrays (NTAs) prepared on nearly equiatomic NiTi alloy shall have broad application potential such as for energy storage and biomedicine, but their precise structure control is a great challenge because of the high content of alloying element of Ni, a non-valve metal that cannot form a compact electronic insulating passive layer when anodized. In the present work, we systemically investigated the influence of various anodization parameters on the formation and structure of Ni-Ti-O NTAs and their potential applications. Our results show that well controlled NTAs can be fabricated during relatively wide ranges of the anodization voltage (5–90 V), electrolyte temperature (10–50°C) and electrolyte NH4F content (0.025–0.8 wt%) but within a narrow window of the electrolyte H2O content (0.0–1.0 vol%). Through modulating these parameters, the Ni-Ti-O NTAs with different diameter (15–70 nm) and length (45–1320 nm) can be produced in a controlled manner. Regarding potential applications, the Ni-Ti-O NTAs may be used as electrodes for electrochemical energy storage and non-enzymic glucose detection, and may constitute nanoscaled biofunctional coating to improve the biological performance of NiTi based biomedical implants.

Osteogenic and angiogenic activities of silicon-incorporated TiO2 nanotube arrays

Osteogenesis and angiogenesis that have interaction in vivo are two pivotal processes for implant osseointegration, so implant surfaces with both enhanced osteogenic and angiogenic activities are in need. Developing silicon (Si) doped TiO2 nanotube array (TNA-Si) coatings shall be a promising strategy to yield favorable implant osseointegration with the combined effects of TiO2 nanotube arrays (TNAs) and Si in the enhancement of both osteogenic and angiogenic activities. To achieve this purpose, TNA-Sis are fabricated through the unique strategy of anodization of magnetron-sputtered TiSi coatings. Under optimized conditions, a highly ordered nanotubular structure with even dispersion of Si throughout the nanotubes in the form of SiO2 can be obtained. Si incorporation has little influence on the nanotube length, but slightly decreases the diameter, thickens the nanotube wall, and increases the hydrophilicity. TNA-Sis show good cytocompatibility to both osteoblasts and endothelial cells (ECs). TNA-Sis show enhanced proliferation, spreading, alkaline phosphatase activity, collagen secretion, and matrix mineralization of osteoblasts. Meanwhile, TNA-Sis induce better EC proliferation, and the conditioned culture media from TNA-Sis generate better angiogenic ability, nitric oxide production, and vascular endothelial growth factor secretion from ECs. In particular, TNA-Si4.6 with the strongest osteogenic and angiogenic activities in the context of the present study is highly promising as the next-generation hard tissue implant coating.

Antibacterial ability and angiogenic activity of Cu-Ti-O nanotube arrays

Bacterial infection and loosening of orthopedic implants remain two disastrously postoperative complications. Angiogenesis is critical important to facilitate implant osseointegration in vivo. TiO2 nanotubes arrays (NTAs) with proper dimensions possess good osseointegration ability. Accordingly, the present work incorporated copper (Cu) into TiO2 NTAs (Cu-Ti-O NTAs) to enhance their antibacterial ability and angiogenesis activity, which was realized through anodizing magnetron-sputtered TiCu coatings with different Cu contents on pure titanium (Ti). Our results show ordered Cu-Ti-O NTAs can be produced under proper Cu content (<15.14%) in TiCu coatings. The NTAs possess excellent long-term antibacterial ability against Staphylococcus aureus (S. aureus), which may be ascribed to sustained release of Cu2+. The cytotoxicity of Cu-Ti-O NTAs to endothelial cells (ECs) could be negligible and can even promote cell proliferation as revealed by live/dead staining and MTT. Meanwhile, Cu-Ti-O NTAs can up-regulate nitric oxide (NO) synthesis and vascular endothelial growth factors (VEGF) secretion of ECs on the sample surfaces compared with that of pure TiO2 NTAs (control). Furthermore, the angiogenic activity is also enhanced in ionic extracts of Cu-Ti-O NTAs compared with the control. The excellent long-term antibacterial ability and favorable angiogenic activity render Cu-Ti-O NTAs to be promising implant coatings.

Antibacterial ability and osteogenic activity of porous Sr/Ag-containing TiO2 coatings.

Implant-associated infection and poor osseointegration remains a major clinical challenge in Ti-based implant materials. A versatile strategy to endow Ti-based implants with long-term antibacterial ability as well as better osteogenic activity is highly desirable for high quality implantation. Strontium (Sr) has been shown to be a significant element to favor bone growth by promoting new bone formation and inhibiting bone resorption. In this study, a novel duplex-treatment technique encompassing magnetron sputtering with micro-arc oxidation is utilized to fabricate porous Sr/Ag-containing TiO2 coatings loaded with different concentrations of Ag and Sr. All coatings are porous with pore size less than 5 µm. Ag is primarily distributed homogeneously inside the pores, and the concentrations of Ag in Sr/Ag-containing TiO2 coatings with low and high Ag contents are 0.40 at.% and 0.83 at.% respectively. We have demonstrated that this kind of coating displays long-lasting antibacterial ability even up to 28 d due to the incorporation of Ag. Further, Sr/Ag-containing TiO2 coatings with optimum Ag and Sr contents revealed good cytocompatibility, enhanced osteoblast spreading and osseointegration, which stemmed primarily from the synergistic effect exerted by the porous surface topography and the bioactive element Sr. However, this study has also identified, for the first time, that proper addition of Ag would further facilitate osteogenic effects. Besides, Sr may be able to alleviate the potential cytotoxic effect of excessive Ag. Thus, integration of optimum functional elements Ag and Sr into Ti-based implant materials would be expected to expedite osseointegration while simultaneously sustaining long-term antibacterial activity, which would provide new insights for relevant fundamental investigations and biomedical applications.

Antibacterial, osteogenic, and angiogenic activities of SrTiO3 nanotubes embedded with Ag2O nanoparticles

Biomedical titanium (Ti) implants with good anti-infective, osteogenic, and angiogenic properties are in great demand. SrTiO3 nanotubes (NTs) are embedded with silver oxide (Ag2O) nanoparticles (NPs) (denoted as NT-Sr-Ag) by a hydrothermal treatment of TiO2 NTs containing Ag2O NPs (denoted as NT-Ag) in a Sr(OH)2 solution. The morphology, composition, microstructure, ion release phenomenon, as well as antibacterial, osteogenic, and angiogenic activities are investigated in details. During the hydrothermal treatment, the amorphous TiO2 in the NTs morphs into cubic SrTiO3 gradually and the ordered nanotubular architecture is preserved. Some Ag2O NPs are incorporated into the structure although some of them dissolve in the solution. Long-term bacterial resistance against Staphylococcus aureus is observed as a result of the prolonged and controllable Ag+ release. NT-Sr-Ag can also release Sr2+ similarly to stimulate osteoblasts to secrete the vascular endothelial growth factor (VEGF). Both the released Sr2+ and secreted VEGF upregulate the alkaline phosphatase (ALP) activity and extracellular matrix mineralization of osteoblasts. Furthermore, better angiogenic activity is observed when endothelial cells are cultured in NT-Sr-Ag conditioned media when compared with that in NT-Ag conditioned media, which is believed to be ascribed to the positive regulation of VEGF secretion of Sr2+. NT-2Sr-Ag and NT-3Sr-Ag (Hydrothermal treatment for 2 and 3h, respectively) exhibit excellent antibacterial, osteogenic, and angiogenic activities and are promising in biomedical implants.

Length-dependent corrosion behavior, Ni 2+ release, cytocompatibility, and antibacterial ability of Ni-Ti-O nanopores anodically grown on biomedical NiTi alloy

In the present work, nickel-titanium-oxygen nanopores with different length (0.55-114 μm) were anodically grown on nearly equiatomic nickel-titanium (NiTi) alloy. Length-dependent corrosion behavior, nickel ion (Ni2+) release, cytocompatibility, and antibacterial ability were investigated by electrochemical, analytical chemistry, and biological methods. The results show constructing nanoporous structure on the NiTi alloy improve its corrosion resistance. However, the anodized samples release more Ni2+ than that of the bare NiTi alloy, suggesting chemical dissolution of the nanopores rather than electrochemical corrosion governs the Ni2+ release. In addition, the Ni2+ release amount increases with nanopore length. The anodized samples show good cytocompatibility when the nanopore length is <11 μm. Encouragingly, the length scale covers the one (1-11 μm) that the nanopores showing favorable antibacterial ability. Consequently, the nanopores with length in the range of 1-11 μm are promising as coatings of biomedical NiTi alloy for anti-infection, drug delivery, and other desirable applications.