The role of electron irradiation history in liquid cell transmission electron microscopy.

In situ liquid cell transmission electron microscopy (LC-TEM) allows dynamic nanoscale characterization of systems in a hydrated state. Although powerful, this technique remains impaired by issues of repeatability that limit experimental fidelity and hinder the identification and control of some variables underlying observed dynamics. We detail new LC-TEM devices that improve experimental reproducibility by expanding available imaging area and providing a platform for investigating electron flux history on the sample. Irradiation history is an important factor influencing LC-TEM results that has, to this point, been largely qualitatively and not quantitatively described. We use these devices to highlight the role of cumulative electron flux history on samples from both nanoparticle growth and biological imaging experiments and demonstrate capture of time zero, low-dose images on beam-sensitive samples. In particular, the ability to capture pristine images of biological samples, where the acquired image is the first time that the cell experiences significant electron flux, allowed us to determine that nanoparticle movement compared to the cell membrane was a function of cell damage and therefore an artifact rather than visualizing cell dynamics in action. These results highlight just a subset of the new science that is accessible with LC-TEM through the new multiwindow devices with patterned focusing aides

Trojan-like internalization of anatase titanium dioxide nanoparticles by human osteoblast cells

Dentistry and orthopedics are undergoing a revolution in order to provide more reliable, comfortable and long-lasting implants to patients. Titanium (Ti) and titanium alloys have been used in dental implants and total hip arthroplasty due to their excellent biocompatibility. However, Ti-based implants in human body suffer surface degradation (corrosion and wear) resulting in the release of metallic ions and solid wear debris (mainly titanium dioxide) leading to peri-implant inflammatory reactions. Unfortunately, our current understanding of the biological interactions with titanium dioxide nanoparticles is still very limited. Taking this into consideration, this study focuses on the internalization of titanium dioxide nanoparticles on primary bone cells, exploring the events occurring at the nano-bio interface. For the first time, we report the selective binding of calcium (Ca), phosphorous (P) and proteins from cell culture medium to anatase nanoparticles that are extremely important for nanoparticle internalization and bone cells survival. In the intricate biological environment, anatase nanoparticles form bio-complexes (mixture of proteins and ions) which act as a kind of ‘Trojan-horse’ internalization by cells. Furthermore, anatase nanoparticles-induced modifications on cell behavior (viability and internalization) could be understand in detail. The results presented in this report can inspire new strategies for the use of titanium dioxide nanoparticles in several regeneration therapies

Deformation-driven electrical transport in amorphous TiO \u3c inf\u3e 2 nanotubes

A series of in situ transmission electron microscopy combined with scanning tunneling microscopy measurements were carried out to investigate the effect of mechanical deformation on the electrical transport properties of amorphous TiO 2 nanotubes. Under no mechanical straining, it was found that the TiO 2 nanotubes behave as electrical insulators. However, the nanotubes show semiconducting behavior under a highly deformed state. On the basis of a metal-semiconductor-metal model, it was suggested that in-shell defects, surface defect-driven conduction modes, are responsible for the appearance of the semiconducting behavior. © 2012 Springer-Verlag

Tribocorrosive behaviour of commonly used temporomandibular implants in a synovial fluid-like environment: Ti-6Al-4V and CoCrMo

The temporomandibular joint implant metal alloys, Ti6Al4V and CoCrMo, (n = 3/group) were tested under free-potential and potentiostatic conditions using a custom-made tribocorrosion apparatus. Sliding duration (1800 cycles), frequency (1.0 Hz) and load (16 N) mimicked the daily mastication process. Synovial-like fluid (bovine calf serum, pH = 7.6 at 37 °C) was used to simulate the in vivo environment. Changes in friction coefficient were monitored throughout the sliding process. Changes in surface topography, total weight loss and roughness values were calculated using scanning electron microscopy and white-light interferometry. Finally, statistical analyses were performed using paired t-tests to determine significance between regions within each metal type and also independent sample t-tests to determine statistical significance between metal alloy types. Ti6Al4V demonstrated a greater decrease of potential than CoCrMo, a higher weight loss from wear (Kw = 257.8 versus 2.62 μg; p \u3c 0.0001), a higher weight loss from corrosion (Kc = 17.44 versus 0.14 μg; p \u3c 0.0001) and a higher weight loss from the combined effects of wear and corrosion (Kwc = 275.28 versus 2.76 μg; p \u3c 0.0001). White-light interferometry measurements demonstrated a greater difference in surface roughness inside the wear region in Ti6Al4V than CoCrMo after the sliding (Ra = 323.80 versus 70.74 nm; p \u3c 0.0001). In conclusion, CoCrMo alloy shows superior anti-corrosive and biomechanical properties. © 2013 IOP Publishing Ltd

Structural instabilities in TiO \u3c inf\u3e 2 nanotubes

We report the structural instability of TiO2 nanotubes subjected to treatment with ammonium hydroxide (NH4 OH) solution prior to calcination at elevated temperatures. The nanotubes were disintegrated into nanoparticles and the tubular morphology was vanished after 2 h of calcination at 500 °C. High-resolution transmission electron microscopy, Raman spectroscopy, x-ray diffraction, and atomic force microscopy were used to understand the nature of structural collapse in the NH4 OH treated TiO2 nanotubes. It was concluded that the volumetric changes during amorphous to anatase phase transformation and surface cracking was the key role during the collapse of NH4 OH -treated TiO2 nanotubes. © 2010 American Institute of Physics

A study on the modulation of the electrical transport by mechanical straining of individual titanium dioxide nanotube

We report here, the deformation driven modulation of the electrical transport properties of an individual TiO2 nanotube via in situ transmission electron microscopy (TEM) using a scanning tunneling microscopy system. The current-voltage characteristics of each individual TiO2 nanotube revealed that under bending deformation within the elastic limit, the electrical conductivity of a TiO2 nanotube can be enhanced. High resolution TEM and electron diffraction pattern reveal that TiO2 nanotubes have tetragonal structure (a=0.378 nm, c=0.9513 nm, I 4 1/amd). Analysis based on a metal-semiconductor-metal model suggests that in-shell, surface defect-driven conduction modes and electron-phonon coupling effect are responsible for the modulated semiconducting behaviors. © 2010 American Institute of Physics