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ABSTRACT: Various approaches have been studied to engineer the implant surface to enhance bone in-growth properties, particularly using micro- and nano-topography. In this study, the behavior of osteoblast (bone) cells was analyzed in response to a titanium oxide (TiO2) nanotube-coated commercial zirconia femoral knee implant consisting of a combined surface structure of a micro-roughened surface with the nanotube coating. The osteoblast cells demonstrated high degrees of adhesion and integration into the surface of the nanotube-coated implant material, indicating preferential cell behavior on this surface when compared to the bare implant. The results of this brief study provide sufficient evidence to encourage future studies. The development of such hierarchical micro- and nano-topographical features, as demonstrated in this work, can provide insightful designs for advanced bone-inducing material coatings on ceramic orthopedic implant surfaces.
Materials science & engineering. C, Materials for biological applications. 07/2013; 33(5):2752-6.
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ABSTRACT: Iron oxide nanoparticles (IONPs) are promising neuroimaging agents and molecular cargo across neurovascular barriers. Development of intrinsically safe IONP chemistries requires a robust in vivo nanoneurotoxicity screening model. Herein, we engineered four IONPs of different surface and core chemistries: DMSA-Fe2O3, DMSA-Fe3O4, PEG-Fe3O4 and PEG-Au-Fe3O4. Capitalizing on the ability of the peripheral nervous system to recruit potent immune cells from circulation, we characterized a spatiotemporally controlled platform for the study of in vivo nanobiointerfaces with hematogenous immune cells, neuroglial and neurovascular units after intraneural IONP delivery into rat sciatic nerve. SQUID magnetometry and histological iron stain were used for IONP tracking. Among the IONPs, DMSA-Fe2O3 NPs were potent pro-apoptotic agents in nerve, with differential ability to regulate oxidative stress, inflammation and apoptotic signaling in neuroglia, macrophages, lymphocytes and endothelial cells. This platform aims to facilitate the development of predictive paradigms of nanoneurotoxicity based on mechanistic investigation of relevant in vivo bio-nanointerfaces.
Nanomedicine: nanotechnology, biology, and medicine 05/2013; · 5.44 Impact Factor
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ABSTRACT: Typical dye sensitized solar cells (DSSCs) exhibit a severe reduction of power conversion efficiency when the cell size is increased. In order to cope with this issue, we have investigated the use of anodized TiO(2) nanotubes on Ti foil in combination with the standard TiO(2) nanoparticle paste coated anode structure. The presence of nanotubes in the anode structure enabled a significant mitigation of the size-dependent deterioration of the DSSC performance, with a trend of much milder decrease of the efficiency as a function of the cell dimension up to 9 cm(2). The observed improvement is partly attributed to the elimination of fluorine-doped tin oxide glass in the anode structure, as well as the enhanced charge collection via the nanotube coated Ti substrate, resulting from enhanced mechanical and electrical connections and possibly improved light trapping. The introduction of TiO(2) nanotubes on the Ti foil substrate led to a substantial improvement of the J(sc) current density.
Nanotechnology 01/2013; 24(4):045401. · 3.98 Impact Factor
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ABSTRACT: Hollow-sphere-structured magnetic nanocapsules containing intentionally trapped iron oxide nanoparticles and anticancer drugs have
been prepared to provide a powerful magnetic vector under moderate gradient magnetic fields. It is shown that these nanocapsules can
penetrate into the interior oftumors and allow a controlled ON–OFF switchable release of the anticancer drug cargo via remote 100 KHz
RF field. This smart drug delivery system is nanoscale compact, with the drug molecules and magnetic nanoparticles contained within
the hollow capsules having diameter.In vitro results using a mouse model indicate that such a nanocapsule-mediated,
on-demand drug release is effective in reducing tumor cell growth.
IEEE Transactions on Magnetics 01/2013; 49(1):349-352. · 1.36 Impact Factor
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ABSTRACT: Stimuli-responsive nanoparticles (SRNPs) offer the potential in enhancing the therapeutic efficacy and minimizing the side effect of chemotherapeutics by controllably releasing the drug cargoes at the target site. Currently, controlled drug release through external activation remains a major challenge during delivery of therapeutic agents. Here we report a lipid-polymer hybrid nanoparticle system containing magnetic beads for stimuli-responsive drug release via remote radio frequency (RF) magnetic field. These hybrid nanoparticles showed long-term stability in terms of particle size and polydispersity index in PBS buffer solution. Controllable loading of camptothecin (CPT) and Fe(3)O(4) in the hybrid nanoparticles was demonstrated. RF-controlled drug release from these nanoparticles was observed. In addition, the cellular uptake of the SRNPs into MT2 mouse breast cancer cells was examined. Using CPT as a model anticancer drug, the nanoparticles showed a significant reduction of MT2 mouse breast cancer tumor cell growth in vitro in the presence of remote RF. The ease of preparation, formulation stability, and the controllable drug release mark the strengths of the platform and provide the opportunity to improve cancer chemotherapeutics.
Acta biomaterialia 11/2012; · 3.98 Impact Factor
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ABSTRACT: Delivery of therapeutic or diagnostic agents across an intact blood-brain barrier (BBB) remains a major challenge. Here we demonstrate in a mouse model that magnetic nanoparticles (MNPs) can cross the normal BBB when subjected to an external magnetic field. Following a systemic administration, an applied external magnetic field mediates the ability of MNPs to permeate the BBB and accumulate in a perivascular zone of the brain parenchyma. Direct tracking and localization inside endothelial cells and in the perivascular extracellular matrix in vivo was established using fluorescent MNPs. These MNPs were inert and associated with low toxicity, using a non-invasive reporter for astrogliosis, biochemical and histological studies. Atomic force microscopy demonstrated that MNPs were internalized by endothelial cells, suggesting that trans-cellular trafficking may be a mechanism for the MNP crossing of the BBB observed. The silica-coated magnetic nanocapsules (SiMNCs) allow on-demand drug release via remote radio frequency (RF) magnetic field. Together, these results establish an effective strategy for regulating the biodistribution of MNPs in the brain through the application of an external magnetic field.
Journal of Controlled Release 10/2012; · 5.73 Impact Factor
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ABSTRACT: In this study, a composite of TiO2 nanoparticles/8 nm TiO2 nanotubes was successfully fabricated as a stand-alone, paper-like structure for photoanode of dye-sensitized solar cells by using a simple pressing method. The best power conversion efficiency of 5.38% was for the solar cell under illumination of simulated AM 1.5 solar light. The combination of nanosphere particles and 1D nanostructure leads to the effective electron transport and also provides the mechanical robustness for the overall structure while maintaining the transparency level.
Nano Energy. 05/2012; 1(3):411-417.
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ABSTRACT: The fabrication and planarization of patterned magnetic recording media is investigated and the flyability of magnetic recording
sliders on a patterned and planarized 65mm glass disk is investigated a small coupon of patterned media with an array of
nano pillars of 40nm diameter and 60nm height was first fabricated by e-beam lithography and reactive ion etching (RIE)
to investigate the planarization process for patterned media. Since read/write flyability tests require a patterned disk rather
than a small coupon area, we have prepared a bit patterned glass disks of 65mm diameter (2.5in.) using the so-called “Ag
ball-up process” in combination with RIE. This “Ag ball-up process” permits the manufacturing of a nano-sized bit patterns
on a large area, i.e., on a disk with 65mm diameter. Planarization of the patterned area was performed with hydrogen silsesquioxane
(HSQ) by spin coating. The HSQ layer was back-etched using RIE, resulting in a smooth surface. “Flyability testing” indicates
significantly improved flying stability of typical magnetic recording sliders on the planarized glass disks, with the standard
deviation of flying height fluctuations on the order of 0.1nm. The latter value is comparable to that of “smooth” disks.
Microsystem Technologies 04/2012; 17(3):395-402. · 0.93 Impact Factor
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ABSTRACT: The structure and properties of nanoscale magnetic island arrays for bit patterned media (BPM) have been studied. A periodic
Si nano-island array was fabricated by nano-imprint-lithography (NIL), with the trenchfilling and flattening achieved by resist
spin coating followed by reactive ion back-etching. A Co/Pd multilayer magnetic media with a perpendicular anisotropy was
then sputtered and lifted-off so that the processed nanostructure array now has the magnetic material only on the top of the
pillars. This process significantly improved the magnetic characteristics of BPM. A planarization by hydrogen silsesquioxane
filling reduced the tribological interference of the protruding nanoisland heights in BPM.
Keywordsbit patterned media–nano imprint lithography–filling and planarization
Electronic Materials Letters 04/2012; 6(3):113-116. · 1.82 Impact Factor
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ABSTRACT: This paper reports on the extremely superhydrophobic behavior of supercritical CO2 processed silicon nanowires SiNWs) with a contact angle in excess of ∼177°. Vertically aligned silicon nanowires with 10
nm to 40 nm diameter and 1 mm to 3 mm in length were obtained by electroless etching (EE) technique. The asfabricated SiNWs
were superhydrophilic with no water droplet formation (zero contact angle), and were then completely transformed to an extreme
superhydrophobic state when their nanoscale surface roughness is combined with trichlorosilane hydrophobic coating. The processed
SiNW array was so hydrophobic that water droplets always bounced off the surface and did not allow contact angle measurements
to be obtained unless the substrate was intentionally given a concave-curvature by vacuum suction. Utilization of a hydrophobically
surface-treated micro-pipette syringe enabled the release of a water droplet onto this extremely superhydrophobic surface
for contact angle measurement. To prevent severe nanowire agglomeration during the drying process of wet etched SiNWs, supercritical
CO2 drying was utilized, which process significantly improved the nano configuration and enhanced hydrophobicity.
Keywordssuperhydrophobic surface–electroless etching–silicon nanowires–contact angle
Electronic Materials Letters 04/2012; 6(2):59-64. · 1.82 Impact Factor
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ABSTRACT: It is demonstrated that an incorporation of double-walled carbon nanotubes (DWCNTs) into a TiO 2 photo-anode layer results in a significant improvement in the overall energy conversion performance in the dye-sensitized solar cell (DSSC). Comparing to the standard TiO 2 anode, the carbon nanotube-containing TiO 2 anode with 0.2 wt. % DWCNTs has boosted up the photocurrent density (J sc) by 43%. The DSSC power conversion efficiency was also improved from $3.9% in the case of carbon nanotube-free TiO 2 anode to as high as 6.4% with the addition of DWCNTs upon optimized anode annealing. The observed enhancement in the solar cell performance in the presence of the carbon nanotubes is attributed primarily to the noticeable reduction in microcracking and associated robust electrical conduc-tion. Some contribution of the electrical conducting nature of the filler material (DWCNTs) to the improved DSSC properties may be possible; however, it is viewed as a minor effect, considering the small amount of the nanotubes used. V C 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4705117]
Journal of Renewable and Sustainable Energy 04/2012; 4(2). · 1.21 Impact Factor
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ABSTRACT: Nanostructured materials are believed to play a fundamental role in orthopedic research because bone itself has a structural hierarchy at the first level in the nanometer regime. Here, we report on titanium oxide (TiO(2)) surface nanostructures utilized for orthopedic implant considerations. Specifically, the effects of TiO(2) nanotube surfaces for bone regeneration will be discussed. This unique 3D tube shaped nanostructure created by electrochemical anodization has profound effects on osteogenic cells and is stimulating new avenues for orthopedic material surface designs. There is a growing body of data elucidating the benefits of using TiO(2) nanotubes for enhanced orthopedic implant surfaces. The current trends discussed within foreshadow the great potential of TiO(2) nanotubes for clinical use.
Trends in Biotechnology 03/2012; 30(6):315-22. · 9.15 Impact Factor
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ABSTRACT: Silicon is one of the most important materials for modern electronics, telecom, and photovoltaic (PV) solar cells. With the rapidly expanding use of Si in the global economy, it would be highly desirable to reduce the overall use of Si material, especially to make the PVs more affordable and widely used as a renewable energy source. Here we report the first successful direction-guided, nano/microshaping of silicon, the intended direction of which is dictated by an applied magnetic field. Micrometer thin, massively parallel silicon sheets, very tall Si microneedles, zigzag bent Si nanowires, and tunnel drilling into Si substrates have all been demonstrated. The technique, utilizing narrow array of Au/Fe/Au trilayer etch lines, is particularly effective in producing only micrometer-thick Si sheets by rapid and inexpensive means with only 5 μm level slicing loss of Si material, thus practically eliminating the waste (and also the use) of Si material compared to the ~200 μm kerf loss per slicing and ~200 μm thick wafer in the typical saw-cut Si solar cell preparation. We expect that such nano/microshaping will enable a whole new family of novel Si geometries and exciting applications, including flexible Si circuits and highly antireflective zigzag nanowire coatings.
Nano Letters 03/2012; 12(4):2045-50. · 13.20 Impact Factor
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ABSTRACT: The importance and benefits of nanotechnology in biology and medicine are now well-recognized by scientists, technologists,
as well as various governmental and private research funding agencies. The basis that enables the application of nanotechnology
is the availability of nanostructured materials. Therefore, it is essential to provide an insight on the state-of-the-art
methods to manufacture various nanostructures.
12/2011: pages 27-44;
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ABSTRACT: Co/Pd multilayer media with an antidot structure have been fabricated on hole-patterned Si substrates. Si nanoholes were created by dry etching using a self-assembled diblock copolymer (DBCP) pattern as an etch mask. To enhance dry etching selectivity, thin Cr film was vacuum deposited on DBCP surface at an oblique incident angle. In comparison with the Co/Pd multilayer on a flat Si substrate, the magnetic hysteresis loop of the antidot structured Co/Pd multilayer revealed an enhanced coercive force largely independent of the amount of reactive etching time, while the shape of hysteresis loop was substantially altered as a function of dry etching time. In an optimized condition, high perpendicular magnetic anisotropy was obtained while no significant parallel magnetic anisotropy was seen, which is desirable for perpendicular recording media or pseudobit-patterned media application.
IEEE Transactions on Magnetics 11/2011; · 1.36 Impact Factor
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09/2011; , ISBN: 978-953-307-609-6
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ABSTRACT: We report unprecedented superomniphobic characteristics of nanotube-structured TiO(2) surface fabricated by electrochemical etching and hydrothermal synthesis process, with the wettability contact angles for water and oil both being ∼174° or higher. A tangled forest of ∼8-nm-diameter, multiwalled nanotubes of TiO(2) was produced on the microtextured Ti surface, with the overall nanotube length controlled to 150 nm by adjusting the processing time. Wettability measurements indicate that the nanotube surface is extremely nonwettable to both water and oil. The contact angle of the 8 nm TiO(2) nanotube surface after perfluorosilane coating is extremely high (178°) for water droplets indicating superhydrophobic properties. The contact angle for oil, measured using a glycerol droplet, is also very high, about 174°, indicating superoleophobic characteristics. These dual nonwetting properties, superomniphobic characteristics, are in sharp contrast to the as-made TiO(2) nanotubes which exhibit superhydrophilic properties with a contact angle of essentially ∼0°. Such an extreme superomniphobic material made by a simple and versatile method can be useful for a variety of technical applications. It is interesting to note that all three properties can be obtained with identical nanotube structures. A nanometer-scaled structure introduced by hydrothermally grown TiO(2) nanotubes is an effective air trapping nanostructure in enhancing the amphiphobic (superomniphobic) wettability.
Langmuir 08/2011; 27(16):10191-6. · 4.19 Impact Factor
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Angewandte Chemie International Edition 06/2011; 50(30):6771-5. · 13.45 Impact Factor
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ABSTRACT: Titanium is widely used clinically, yet little is known regarding the effects of modifying its three-dimensional surface geometry at the nanoscale level. In this project we have explored the in vivo response in terms of nitric oxide scavenging and fibrotic capsule formation to nano-modified titanium implant surfaces. We compared titanium dioxide (TiO(2)) nanotubes with 100 nm diameters fabricated by electrochemical anodization with TiO(2) control surfaces. Significantly lower nitric oxide was observed for the nanostructured surface in solution, suggesting that nanotubes break down nitric oxide. To evaluate the soft tissue response in vivo TiO(2) nanotube and TiO(2) control implants were placed in the rat abdominal wall for 1 and 6 weeks. A reduced fibrotic capsule thickness was observed for the nanotube surfaces for both time points. Significantly lower nitric oxide activity, measured as the presence of nitrotyrosine (P<0.05), was observed on the nanotube surface after 1 week, indicating that the reactive nitrogen species interaction is of importance. The differences observed between the titanium surfaces may be due to the catalytic properties of TiO(2), which are increased by the nanotube structure. These findings may be significant for the interaction between titanium implants in soft tissue as well as bone tissue and provide a mechanism by which to improve future clinical implants.
Acta biomaterialia 05/2011; 7(8):3209-15. · 3.98 Impact Factor
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ABSTRACT: Surface engineering approaches that alter the topological chemistry of a substrate could be used as an effective tool for directing cell interactions and their subsequent function. It is well known that the physical environment of nanotopography has positive effects on cell behavior, yet direct comparisons of nanotopographic surface chemistry have not been fully explored. Here we compare TiO(2) nanotubes with carbon-coated TiO(2) nanotubes, probing osteogenic cell behavior, including osteoblast (bone cells) and mesenchymal stem cell (MSC) (osteo-progenitor cells) interactions with the different surface chemistries (TiO(2) vs. carbon). The roles played by the material surface chemistry of the nanotubes did not have an effect on the adhesion, growth or morphology, but had a major influence on the alkaline phosphatase (ALP) activity of osteoblast cells, with the original TiO(2) chemistry having higher ALP levels. In addition, the different chemistries caused different levels of osteogenic differentiation in MSCs; however, it was the carbon-coated TiO(2) nanotubes that had the greater advantage, with higher levels of osteo-differentiation. It was observed in this study that: (a) chemistry plays a role in cell functionality, such as ALP activity and osteogenic protein gene expression (PCR); (b) different cell types may have different chemical preferences for optimal function. The ability to optimize cell behavior using surface chemistry factors has a profound effect on both orthopedic and tissue engineering in general. This study aims to highlight the importance of the chemistry of the carrier material in osteogenic tissue engineering schemes.
Acta biomaterialia 03/2011; 7(6):2697-703. · 3.98 Impact Factor
