Correction: Synthesis of TiO2 nanotubes with ZnO nanoparticles to achieve antibacterial properties and stem cell compatibility.

Correction for 'Synthesis of TiO2 nanotubes with ZnO nanoparticles to achieve antibacterial properties and stem cell compatibility' by Wenwen Liu et al., Nanoscale, 2014, 6, 9050-9062, DOI: 10.1039/C4NR01531B.

Design and Mechanical Properties Verification of Gradient Voronoi Scaffold for Bone Tissue Engineering.

In order to obtain scaffold that can meet the therapeutic effect, researchers have carried out research on irregular porous structures. However, there are deficiencies in the design method of accurately controlling the apparent elastic modulus of the structure at present. Natural bone has a gradient porous structure. However, there are few studies on the mechanical property advantages of gradient bionic bone scaffold. In this paper, an improved method based on Voronoi-tessellation is proposed. The method can get controllable gradient scaffolds to fit the modulus of natural bone, and accurately control the apparent elastic modulus of porous structure, which is conducive to improving the stress shielding. To verify the designed structure can be fabricated by additive manufacturing, several designed models are obtained by SLM and EBM. Through finite element analysis (FEA), it is verified that the irregular porous structure based on Voronoi-tessellation is more stable than the traditional regular porous structure of the same structure volume, the same pore number and the same material. Furthermore, it is verified that the gradient irregular structure has a better stability than the non-gradient structure. An experiment is conducted successfully to verify the stability performance got by FEA. In addition, a dynamic impact FEA is also performed to simulate impact resistance. The result shows that the impact resistance of the regular porous structure, the irregular porous structure and the gradient irregular porous structure becomes better in turn. The mechanical property verification provides a theoretical basis for the structural design of gradient irregular porous bone tissue engineering scaffolds.

The influence of yttrium dopant on the properties of anatase nanoparticles and the performance of dye-sensitized solar cells.

TiO2 mesoporous nanoparticles (NPs) doped with yttrium (Y) ions are fabricated via an environmentally friendly and facile solvothermal method to serve as a photoanode for dye sensitized solar cells (DSSCs). X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy and N2 adsorption-desorption tests are used to characterize the influence of yttrium dopant on the properties of TiO2 NPs. The prepared Y-doped TiO2 NPs show the anatase phase and exhibit Ti-O-Y bonds. The photovoltaic performance is primarily associated with the morphological parameters of the NPs. At the optimum Y concentration of 3 at%, the short circuit current density increased from 13.20 to 15.74 mA cm(-2), full sun solar power conversion efficiencies increased from 6.09% up to 7.61% as compared to the blank DSSC.

Optimizing stem cell functions and antibacterial properties of TiO2 nanotubes incorporated with ZnO nanoparticles: experiments and modeling.

To optimize mesenchymal stem cell differentiation and antibacterial properties of titanium (Ti), nano-sized zinc oxide (ZnO) particles with tunable concentrations were incorporated into TiO2 nanotubes (TNTs) using a facile hydrothermal strategy. It is revealed here for the first time that the TNTs incorporated with ZnO nanoparticles exhibited better biocompatibility compared with pure Ti samples (controls) and that the amount of ZnO (tailored by the concentration of Zn(NO3)2 in the precursor) introduced into TNTs played a crucial role on their osteogenic properties. Not only was the alkaline phosphatase activity improved to about 13.8 U/g protein, but the osterix, collagen-I, and osteocalcin gene expressions was improved from mesenchymal stem cells compared to controls. To further explore the mechanism of TNTs decorated with ZnO on cell functions, a response surface mathematical model was used to optimize the concentration of ZnO incorporation into the Ti nanotubes for stem cell differentiation and antibacterial properties for the first time. Both experimental and modeling results confirmed (R (2) values of 0.8873-0.9138 and 0.9596-0.9941, respectively) that Ti incorporated with appropriate concentrations (with an initial concentration of Zn(NO3)2 at 0.015 M) of ZnO can provide exceptional osteogenic properties for stem cell differentiation in bone cells with strong antibacterial effects, properties important for improving dental and orthopedic implant efficacy.

Antibacterial and osteogenic stem cell differentiation properties of photoinduced TiO2 nanoparticle-decorated TiO2 nanotubes.

AIM: To improve the antibacterial and mammalian cell compatibility properties of titania nanotubes (TNTs) anodized into titanium (Ti). MATERIALS & METHODS: 3-8-nm TiO2 nanoparticles were decorated on the surface and inside TNT (TNT-TiO2) through a hydrothermal method. After UV light treatment, two types of oral bacteria and stem cells were cultured on the samples to determine antibacterial and compatibility properties. RESULTS: TiO2 nanoparticles increased the surface area and photocatalysis of TNTs. Based on the photocatalysis effect and prolonged photo-induced wettability, the numbers of Streptococcus mutans and Porphyromonas gingivalis were lower on the surface of TNT-TiO2 than pure Ti and TNTs after the first 7 days. Specifically, for S. mutans, the glycosytransferase (gtf) genes were downregulated 0.1-0.2-fold on TNT-TiO2. Due to the different topography and high surface energy of TNT-TiO2, stem cells also showed improved osteogenic functions on TNT-TiO2. CONCLUSION: In this study, we demonstrated for the first time improved antibacterial properties and, at the same time, greater stem cell osteogenic capacity when decorating TNTs with nanosized TiO2 particles, which may significantly improve orthopedic and dental implant efficacy.

The nanoscale geometry of TiO2 nanotubes influences the osteogenic differentiation of human adipose-derived stem cells by modulating H3K4 trimethylation.

Nanostructured materials can direct stem cell lineage commitment solely by their various, but controllable, geometric cues, which would be very important for their future application in bone tissue engineering and bone regeneration. However, the mechanisms by which nano-geometric cues dictate the osteogenic differentiation of stem cells remain unclear. Epigenetics is central to cellular differentiation, a process that regulates heritable and long-lasting alterations in gene expression without changing the DNA sequence. Here, we explored the varied osteogenic behaviors of human adipose-derived stem cells (hASCs) on titanium dioxide (TiO2) nanotube arrays of different diameters. Both in vitro and in vivo studies demonstrated that the nanoscale geometry influenced cellular differentiation and TiO2 nanotubes with a diameter of 70 nm was the optimal dimension for the osteogenic differentiation of hASCs. Moreover, we observed that TiO2 nanotubes promoted the osteogenic differentiation of hASCs by upregulating methylation level of histone H3 at lysine 4 (H3K4) in the promoter regions of osteogenic genes Runx2 and osteocalcin, by inhibiting demethylase retinoblastoma binding protein 2 (RBP2). These results revealed, for the first time, the epigenetic mechanism by which nanotopography directs stem cell fate.

Synthesis of TiO2 nanotubes with ZnO nanoparticles to achieve antibacterial properties and stem cell compatibility.

To endow titanium (Ti) with antibacterial properties, different concentrations of zinc oxide (ZnO) nanoparticles were decorated on anodized titanium dioxide (TiO2) nanotubes by a simple hydrothermal treatment method. The particle sizes of ZnO, which were evenly distributed and tightly adherent to the walls of the Ti nanotubes, ranged from 20-50 nm. Results from this study showed that Zn was released from the TiO2 nanotubes in a constant, slow, and biologically inspired manner. Importantly, the results showed that the ZnO decorated TiO2 nanotubular samples inhibited Streptococcus mutants and Porphyromonas gingivalis growth compared to control unmodified Ti samples. Specifically, S. mutants and P. gingivalis growth were both reduced 45-85% on the ZnO decorated Ti samples compared to Ti controls after 7 days of culture. When examining the mechanism of action, it has been further found for the first time that the ZnO decorated Ti samples inhibited the expression of Streptococcus mutans bacterial adhesion genes. Lastly, the results showed that the same samples which decreased bacterial growth the most (0.015 M precursor Zn(NO3)2 samples) did not inhibit mesenchymal stem cell growth compared to Ti controls for up to 7 days. In summary, results from this study showed that compared to plain TiO2 nanotubes, TiO2 decorated with 0.015 M ZnO provided unprecedented antibacterial properties while maintaining the stem cell proliferation capacity necessary for enhancing the use of Ti in numerous medical applications, particularly in dentistry.

Formation process of TiO2 nanotube arrays prepared by anodic oxidation method.

TiO2 nanotube array thin films have great potential in many fields, such as solar cell, photo catalyst, photo-induced cathodic protection for metals and bioactivity. In order to investigate the formation process of the TiO2 nanotube array thin films, the EIS spectrum and current density were measured during the anodic oxidation. The results showed that the formation process could be divided into four stages. The current density decreased sharply at the first stage, and then increased at the second stage, followed by declining and finally remained constant value. In addition, the current density increased with the anodic voltage. The EIS spectrum varied in different stage. The simulated circuit was composed three sections, the first sections indicated the resistance of the electrolyte, the second one gave the double layer structure between the electrolyte and titanium electrode, the third one was a inductive loop, which represented the anions absorbed on the surface of the TiO2 nanotube's wall. The more cations were absorbed, the higher value of the inductive loop would be. The EIS results showed that the value increased with the outer voltage, which means that more cations were absorbed under the higher anodic voltage.