Nanotextured titanium oxide surfaces were obtained by electrochemical anodization of Ti6Al4V alloy. Two different types of electrolytes containing different amounts of water and NH4F concentration in ethylene glycol were used. This work focused on structural modifications by varying the F- ion concentration in the electrolyte, anodization voltage and time. The effect of these anodization parameters on nanotextured morphology and dimensions was studied. The titania nanotube diameters ranging from 50 to 135 nm, and the lengths ranging from 0.5 to 5 μm, were obtained. The morphology showed strong dependence on electrolyte composition whereas, the nanotube dimensions showed dependence on anodization voltage and time. To extend the possibility of fabricating nanotubes on a wide range of Ti6Al4V implant surfaces such as rolled surfaces, thermal plasma sprayed surfaces, and next generation orthopedic implant surfaces made by powder metallurgy, were also targeted in this study

Orthopedic implants requiring osseointegration are often surface modified; however, implants may shed these coatings and generate wear debris leading to complications. Titanium nanotubes (TiNT), a new surface treatment, may promote osseointegration. In this study, in vitro (rat marrow-derived bone marrow cell attachment and morphology) and in vivo (rat model of intramedullary fixation) experiments characterized local and systemic responses of two TiNT surface morphologies, aligned and trabecular, via animal and remote organ weight, metal ion, hematologic, and nondecalcified histologic analyses. In vitro experiments showed total adherent cells on trabecular and aligned TiNT surfaces were greater than control at 30 min and 4 h, and cells were smaller in diameter and more eccentric. Control animals gained more weight, on average; however, no animals met the institutional trigger for weight loss. No hematologic parameters (complete blood count with differential) were significantly different for TiNT groups vs. control. Inductively coupled plasma mass spectrometry (ICP-MS) showed greater aluminum levels in the lungs of the trabecular TiNT group than in those of the controls. Histologic analysis demonstrated no inflammatory infiltrate, cytotoxic, or necrotic conditions in proximity of K-wires. There were significantly fewer eosinophils/basophils and neutrophils in the distal region of trabecular TiNT-implanted femora; and, in the midshaft of aligned TiNT-implanted femora, there were significantly fewer foreign body giant/multinucleated cells and neutrophils, indicating a decreased immune response in aligned TiNT-implanted femora compared to controls.

As total joint replacements increase annually, new strategies to attain solid bone-implant fixation are needed to increase implant survivorship. This study evaluated two morphologies of titania nanotubes (TiNT) in in vitro experiments and an in vivo rodent model of intramedullary fixation, to simulate joint arthroplasty conditions. TiNT surfaces were prepared via an electrochemical etching process, resulting in two different TiNT morphologies, an aligned structure with nanotubes in parallel and a trabecular bone-like structure. in vitro data showed bone marrow cell differentiation into osteoblasts as well as osteoblastic phenotypic behavior through 21 days. In vivo, both TiNT morphologies generated greater bone formation and bone-implant contact than control at 12 weeks, as indicated by μCT analyses and histology, respectively. TiNT groups also exhibited greater strength of fixation compared to controls, when subjected to wire pull-out testing. TiNT may be a promising surface modification for promoting osseointegration.

Recent clinical data suggest improvement in the fixation of tibia trays for total knee arthroplasty when the trays are additive manufactured with highly porous bone ingrowth structures. Currently, ...

In this study, the antibacterial properties of TiNT surfaces, TiNT surfaces integrated with nanosilver, and two current standard-of-care materials (titanium thermal plasma sprayed and titanium alloy surfaces) were evaluated.

In lithium-oxygen batteries, the solubility of LiO2 intermediates in the electrolyte regulates the formation routes of the Li2O2 discharge product. High-donor-number electrolytes with a high solubility of LiO2 tend to promote the formation of Li2O2 large particles following the solution route, which eventually benefits the cell capacity and cycle life. Here, we propose that facet engineering of cathode catalysts could be another direction in tuning the formation routes of Li2O2. In this work, β-MnO2 crystals with high occupancies of {111} or {100} facets were adopted as cathode catalysts in Li-O2 batteries with a tetra(ethylene)glycol dimethyl ether electrolyte. The {111}-dominated β-MnO2 catalyzed the formation of the Li2O2 discharge product into large toroids following the solution routes, while {100}-dominated β-MnO2 facilitated the formation of Li2O2 thin films through the surface routes. Further computational studies indicate that the different formation routes of Li2O2 could be related to different adsorption energies of LiO2 on the two facets of β-MnO2. Our results demonstrate that facet engineering of cathode catalysts could be a new way to tune the formation route of Li2O2 in a low-donor-number electrolyte. We anticipate that this new finding would offer more choices for the design of lithium-oxygen batteries with high capacities and ultimately a long cycle life.

Periprosthetic infection remains a clinical challenge that may lead to revision surgeries, increased spending, disability, and mortality. The cost for treating hip and knee total joint infections i...

To meet future needs for industries from personal devices to automobiles, energy storage devices are transitioning into the next-generation advanced battery systems beyond lithium ions with higher energy density. Among them, lithium-oxygen (Li-O 2 ) battery stands out due to its highest theoretical energy density among all rechargeable ion battery systems. Yet, its application is severely disabled by the sluggish reaction kinetics during oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). To address this problem, various catalysts have been developed with the most promising materials being the noble metals (Pt, etc.) and transitional metal oxides (TMOs such as CoxOy, MnxOy, etc.). While the noble metal catalysts offer superior performance in terms of improving the reaction kinetics, the high cost and environmental sensitivity prevent the large-scale application. As an alternative, TMOs are attracting more and more interest because they exhibit satisfactory catalytic performance while their cost and cycling durability are much better than that of noble metals. While most studies have focused on the development of different TMO structures, phases and compositions, few studies have reported the advancement in the crystalline facet engineering, particularly for the low-cost TMOs such as manganese oxides, and its effect on ORR/OER kinetics. In this work, beta-(β-)MnO2 crystals with either octahedron or rod-like shapes were successfully synthesized separately using a simple hydrothermal method. Combining various electron microscopic methods, the octahedron’s surface is seen to mostly occupied by MnO2-{111} facets, while rod’s surface is occupied by MnO2-{100}. As the cathode for Li-air batteries, the β-MnO2 with {111} facets and {100} facets catalyzed the formation of Li2O2 into large toroids and thin film, respectively. For the first time, we revealed that the control of crystal facets can switch the Li2O2 formation mechanism from the surface mode to the solution mode even in the low donor number TEGDME electrolyte. To further understand the formation kinetics of Li2O2, we referred to operando liquid cell transmission electron microscopy, by which a LiO2 phase was identified to function as the intermediate discharge products which significantly affect the formation of Li2O2 as the final product. Following this finding, DFT results further showed that the different catalytic properties were due to the different adsorption free energies for the LiO2 intermediate on the {111} and {100} facets of MnO2. Our findings revealed that facet-engineering of the low-cost TMO catalysts would open a new way for the design of lithium-air batteries with high stabilities and long cycle life. Figure 1

Exposed crystal facets directly affect the electrochemical/catalytic performance of MnO2 materials during their applications in supercapacitors, rechargeable batteries, and fuel cells. Currently, the facet-controlled synthesis of MnO2 is facing serious challenges due to the lack of an in-depth understanding of their surface evolution mechanisms. Here, combining aberration-corrected scanning transmission electron microscopy (STEM) and high-resolution TEM, we revealed a mutual energy-driven mechanism between beta-MnO2 nanowires and microstructures that dominated the evolution of the lateral facets in both structures. The evolution of the lateral surfaces followed the elimination of the {100} facets and increased the occupancy of {110} facets with the increase in hydrothermal retention time. Both self-growth and oriented attachment along their {100} facets were observed as two different ways to reduce the surface energies of the beta-MnO2 structures. High-density screw dislocations with the 1/2<100> Burgers vector were generated consequently. The observed surface evolution phenomenon offers guidance for the facet-controlled growth of beta-MnO2 materials with high performances for its application in metal-air batteries, fuel cells, supercapacitors, etc.

Engineering crystal facets to enhance their functionalities often require complex processing routes to suppress the growth of surfaces with the lowest thermodynamic energies. Herein, we report a unique method to control the morphologies of beta-MnO2 crystals with different occupancy of {100}/{111} facets through the effect of K+ cations. Combining aberration-corrected scanning transmission electron microscopy (STEM), ultramicrotomy, and dynamic functional theory (DFT) simulation, we clarified that the beta-MnO2 crystals were formed through a direct solid-state phase transition process. Increasing the concentration of K+ cations in the precursor gradually changed the morphology of beta-MnO2 from bipyramid prism ({100}+{111} facets) to an octahedron structure ({111} facets). The K+ cations controlled the morphology of beta-MnO2 by affecting the formation of a-K0.5Mn4O8 intermediate phase and the subsequent phase transition. Utilizing the beta-MnO2 crystals as the cathode for Li-ion batteries showed that highly exposed {111} facets offered beta-MnO2 crystal better rate performance, with similar to 70% capacity retention when the charge-discharge rate increased from 20 mA/g to 200 mA/g. Our work revealed a new mechanism to tune the morphology of this earth-abundant metal oxide crystal, which could be used to adjust its electrochemical performance for different applications, such as supercapacitors and catalysts for metalair batteries and fuel cells.

Titanium knee, shoulder and hip implants are typically grit-blasted, thermal plasma spray coated, or sintered to provide ingrowth surface features having texture with pore sizes on the order of hundreds of micrometers. This provides macro and micro-mechanical locking upon bone remodeling. However, at the nanoscale and cellular level, these surfaces appear smooth. In vitro and in vivo research shows surfaces with nanoscale features result in enhanced osseointegration, greater bone-implant contact area and pullout force, and the potential to be bactericidal via a simple hybrid anodization surface modification process. Prior processes for creating nanotube nano-textured surfaces via electrochemical anodization relied on hydrofluoric acid electrolyte and platinum cathodes. This novel process uses ammonium fluoride electrolytes and graphite cathodes which are more cost effective and easier to handle during processing. Hybrid electrolytes with differing concentrations of ethylene glycol, water, and ammonium flu...

In the present work, we investigate wetting behavior and chemical composition of anodized titanium nanotubular surfaces for orthopedic implant research. The wetting behavior of the nanotubes by alternating UV irradiation and dark storage is reported. This study suggests that hydrophobicity due to aging in air can be restored by annealing, and release of residual fluorine was observed as a function of annealing time, which is important considering side effects of fluorosis. Fabrication of nanotubes on thermal plasma-sprayed implants and super-hydrophilic behavior of these nanotubular surfaces needed for enhanced bioactivity are demonstrated.

The battle against postoperative infection in orthopedic surgery calls for the development of surfaces with antibacterial activity on the implant side of the bacterial biofilm. Incorporation of nanosilver into titanium nanotube surfaces offers a potential solution. This study presents a novel single-step anodization approach to incorporating nanosilver particles within and among anodized titanium nanotubes on implant surfaces using a new hybrid electrolyte. The amount of nanosilver deposited on the titanium nanotubes was analyzed by varying the silver concentration in the hybrid electrolyte. Successful fabrication of titanium nanotubes by anodization of foils, rods and thermal plasma-sprayed surfaces of Ti6Al4V, and simultaneous nanosilver deposition was quantified by field emission scanning electron microscopy, transmission electron microscopy and X-ray energy-dispersive spectroscopy. Upon post-anodization heat treatment, the amorphous to anatase conversion of these structures was confirmed using X-ray diffraction analysis. This study presents a simple single-step fabrication of antibacterial titanium nanotube surfaces allowing controlled nanosilver deposition needed to avoid unintended cytotoxicity.

The amorphous to anatase transformation of anodized nanotubular titania surfaces has been studied by x-ray diffraction and transmission electron microscopy (TEM). A more rapid heat treatment for conversion of amorphous to crystalline anatase favorable for orthopedic implant applications was demonstrated. Nanotube titania surfaces were fabricated by electrochemical anodization of Ti6Al4V in an electrolyte containing 0.2 wt% NH4F, 60% ethylene glycol and 40% deionized water. The resulting surfaces were systematically heat treated in air with isochronal and isothermal experiments to study the temperature and time dependent transformation respectively. Energy dispersive spectroscopy shows that the anatase phase transformation of TiO2 in the as-anodized amorphous nanotube layer can be achieved in as little as 5 min at 350 °C in contrast to reports of higher temperature and much longer time. Crystallinity analysis at different temperatures and times yield transformation rate coefficients and activation energy for crystalline anatase coalescence. TEM confirms the (101) TiO2 presence within the nanotubes. These results confirm that for applications where amorphous titania nanotube surfaces are converted to crystalline anatase, a 5 min production flow-through heating process could be used instead of a 3 h batch process, reducing time, cost, and complexity.

Depositing anodised titanium on ZrO2 substrate improves the bioactivity of the ZrO2 substrate in terms of enhanced cell viability, cell attachment and cell elongation.

Electrochemical etching of titanium alloy in a fluoride-containing electrolyte results in ordered nanotextured surfaces. The reproducibility of nanotextured surfaces depends on several process parameters, most notably the fluoride ion concentration in the electrolyte. In the present work, electrochemical etching of Ti6Al4V alloy foils in ethylene glycol containing 0.66 wt% NH4F and 2% deionized water was carried out at 60 V for 45 minutes. This paper describes the depletion of fluoride ion concentration and contamination of electrolyte upon reuse. Inductively coupled plasma-optical emission spectroscopy was used to measure the dissolution of metal oxides in the electrolyte during etching. We found increasing concentration of the alloy elements Ti, Al, V contaminated the electrolyte due to repeated reuse of the electrolyte. The results show an appreciable log-linear depletion of fluoride ion concentration resulting in a changed surface morphology, chemical composition and etched volume. This paper provides an important insight to changes in surface morphology and surface chemistry with extended reuse of the etching electrolyte, useful for regulatory approvals.

Category: Basic Sciences/Biologics Introduction/Purpose: Solid biologic fixation at the bone-implant interface provides long-term stability of orthopaedic implants. Historically, coatings and surface treatments on implant surfaces have been used to promote osseointegration of orthopaedic implants. The purpose of this research study is to evaluate two morphologies of titania nanotube (TiNT) surfaces via in vitro experiments as well as an in vivo model of femoral intramedullary fixation, in order to assess the influence of TiNT structure on de novo bone formation and bone-implant stability. Methods: TiNT structures were grown from Ti-6Al-4 V materials via an established electrochemical anodization process. Samples were either sonicated then annealed (Aligned TiNT) or annealed without prior sonication (Trabecular TiNT), to produce different morphologies. As-received titanium alloy was the control. Marrow-derived stem cells were isolated from long bones of Sprague Dawley rats and cultured on samples. Alkaline phosphatase (ALP) and osteocalcin (OC) expression by stem cells were assessed via ELISA. Cells were lysed and subjected to quantitative polymerase chain reaction (qPCR) to assess Col1a1, osteonectin, and IGF- 1 expression. An in vivo study evaluated bone formation at 4- and 12-week endpoints. Eight female Sprague Dawley rats per group per endpoint received bilateral Ti-6Al-4 V K-wires as femoral implants. Left femur received control, while right femur received Aligned/Trabecular TiNT K-wire. Bone formation was assessed via microCT, backscatter electron imaging (BEI), and non- decalcified histologic analyses. Results: Aligned and Trabecular TiNT groups demonstrated higher ALP activity than control at 2 and 3 weeks. The in vivo study demonstrated increased bone volume fractions (BV/TV) and total bone volume (TBV) for TiNT surfaces (microCT). The ratio of both BV/TV and TBV in the distal VOI were nearly equivalent for both TiNT surfaces, indicating similar bone formation between both TiNT surfaces and control. In the midshaft VOI, the ratios between TiNT surfaces and control were 1.5 or greater, indicating increased bone formation. At 12 weeks, the bone-implant contact fraction ratio (BEI) showed Aligned TiNT and Trabecular TiNT were 1.3 and 1.4 times greater than control, respectively. Histologic analysis showed both TiNT surfaces had 1.5 times the bone-implant contact as control. Conclusion: In vitro studies demonstrated improved support for osteogenic functions of cultured marrow-derived stem cells on TiNT surfaces compared to controls. μCT, BEI, and histologic analyses associated with the in vivo study demonstrated increased bone formation in the TiNT femora, at specific timepoints and VOIs.

Event Abstract Back to Event Corrosion property of vitamin D loaded nanotubes for bio-implants application in an in vitro environment Sweetu Patel1, Cortino Sukotjo2, Christos Takoudis3, Mathew Mathew4, Farid Amirouche5, Craig Friedrich1 and Tolou Shokuhfar1, 3 1 Michigan Technological University, Mechanical Engineering, United States 2 University of Illinois at Chicago, Restorative Dentistry, United States 3 University of Illinois at Chicago, Bioengineering, United States 4 Rush University Medical Center, Orthopaedics, United States 5 University of Illinois at Chicago, Orthopaedics, United States Introduction: In this study, Ti6Al4V surface has been functionalized with TiO2 nanotubes (TNTs), which has a biomimetic topography that resembles the porous bone morphology structure. Additionally, these TNTs are loaded with Vitamin D, which plays an essential role in homeostasis of the bone remodeling[1]. Previously, various beneficial factors of TNTs have been studied; however, the corrosion property of drug loaded TNTs has yet to be investigated[2]. Therefore, the main objectives of this study is to investigate the corrosion properties of the vitamin D loaded TNTs by performing open circuit potential (OCP), electrochemical impedance spectroscope (EIS) and potentiodynamic (PD) testing in phosphate buffer saline (PBS) and bovine calf serum (BCS) solutions. Methods: Ti6Al4V discs were divided into three groups: non-anodized (NA), anodized (A), and vitamin D loaded anodized surfaces (AD). A and AD surfaces were anodized in 0.2-wt% NH4F, 4-vol% H2O, in EG with a constant voltage of 60V for 2 hours. For AD surfaces, 5000 IU of Vitamin D (within recommended dosage by NIH) was loaded inside TNTs using pipetting and centrifuging technique[3]. Finally, corrosion property of each surface was investigated by performing OCP, EIS and PD testing. Results: Figure 1 shows the OCP graphs of NA, A, and AD samples in PBS and BCS. It is observed that the OCP of A and AD samples are significantly high (p<0.05) compared to NA. This suggests that TNTs decorated surface has higher tendency to resist corrosion than non-treated Ti6Al4V surfaces. Figure 2 shows the PD curves for all the samples, which provides information regarding the corrosion current density (Icorr) and passivation current (Ipass). It shows that lower Icorr and Ipass were obtained for A and AD in PBS compared to NA, indicating its ability to resist corrosion. Figure 3 shows the quantitative data of polarization resistance (Rp) and capacitance (C) of the surface. It is observed that significantly high Rp and low C were observed for A and AD surfaces in PBS or BCS solution, which indicates that A and AD surfaces can resist current flow due to electrochemical reaction and it also has less electrochemically active sites for charge transfer that can facilitate corrosion. Discussion: Results from this study show that Vitamin D loaded nanotubes have similar corrosion properties as non-loaded TNTs. Comprehensive analysis from OCP, PD and EIS data suggests that at either at resting or dynamic conditions, anodized surface have a lower tendency to corrode at bone-implant interface due to its thick oxide layer and the ability of the surface to interact with ions in the surrounding environment, thereby forming insulating dielectric film. Additionally, the electrostatic interaction between the negatively charged TNTs and the proteins from the extracellular fluid forms a protective layer on the anodized surface, which explains the high resistance and low capacitance value[4]. Significance: The study highlights two key points in the development of smart TNTs surfaces. First we have shown that a biomimetic surface is possible and second we have demonstrated how these clusters of nanotubes can act as a reservoir for potential drug storage and drug delivery without risking any surface corrosion resistance property loss. This work made use of instrument in the Electron Microscopy Service (Research Resource Center, UIC). Financial support was provided by the Mechanical Engineering Department at MTU. We are grateful to National Science Foundation, DMR Grant # 1350734, NSF award 1359734 and CBET Grant # 1067424, for making some of our characterizations possible.References:[1] Bouillon, R. and T. Suda, Vitamin D: calcium and bone homeostasis during evolution. BoneKEy Rep, 2014. 3.[2] Yu, W.Q., et al., Corrosion behaviors of TiO2 nanotube layers on titanium in Hank's solution. Biomed Mater, 2009. 4(6): p. 065012.[3] Strengthening Knowledge and Understanding of Dietary Supplements, in Vitamin D. national Institutes of Health: Office of Dietary Supplements. p. 12.[4] Gongadze, E., et al., Adhesion of osteoblasts to a nanorough titanium implant surface. International Journal of Nanomedicine, 2011. 6: p. 1801-1816. Keywords: Biomimetic, biomaterial, Bioactive molecule, bioinerface Conference: 10th World Biomaterials Congress, Montréal, Canada, 17 May - 22 May, 2016. Presentation Type: Poster Topic: Nano-structured materials for unique functions Citation: Patel S, Sukotjo C, Takoudis C, Mathew M, Amirouche F, Friedrich C and Shokuhfar T (2016). Corrosion property of vitamin D loaded nanotubes for bio-implants application in an in vitro environment. Front. Bioeng. Biotechnol. Conference Abstract: 10th World Biomaterials Congress. doi: 10.3389/conf.FBIOE.2016.01.02634 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 27 Mar 2016; Published Online: 30 Mar 2016. Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Sweetu Patel Cortino Sukotjo Christos Takoudis Mathew Mathew Farid Amirouche Craig Friedrich Tolou Shokuhfar Google Sweetu Patel Cortino Sukotjo Christos Takoudis Mathew Mathew Farid Amirouche Craig Friedrich Tolou Shokuhfar Google Scholar Sweetu Patel Cortino Sukotjo Christos Takoudis Mathew Mathew Farid Amirouche Craig Friedrich Tolou Shokuhfar PubMed Sweetu Patel Cortino Sukotjo Christos Takoudis Mathew Mathew Farid Amirouche Craig Friedrich Tolou Shokuhfar Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Molecular sensors and molecular electronics are a major component of a recent research area known as bionanotechnology, which merges biology with nanotechnology. This new class of biosensors and bioelectronics has been a subject of intense research over the past decade and has found application in a wide variety of fields. The unique characteristics of these biomolecular transduction systems has been utilized in applications ranging from solar cells and single-electron transistors (SETs) to fluorescent sensors capable of sensitive and selective detection of a wide variety of targets, both organic and inorganic. This review will discuss three major systems in the area of molecular sensors and electronics and their application in unique technological innovations. Firstly, the synthesis of optoelectric bacteriorhodopsin (bR) and its application in the field of molecular sensors and electronics will be discussed. Next, this article will discuss recent advances in the synthesis and application of semiconductor quantum dots (QDs). Finally, this article will conclude with a review of the new and exciting field of noble metal nanoclusters and their application in the creation of a new class of fluorescent sensors.

Modifying surface chemistry and/or surface topography is considered to be a traditional way of optimizing bone-implant integration (osseointegration) for improved bone bonding. The previous results have shown enhanced in vitro osteoblast cell density on titania nanotube–covered surfaces compared with bare titanium surfaces. However, for titania nanotubes to be considered as a candidate surface modification for titanium implants, they must survive load-bearing conditions. The authors investigated the structural survivability of nanotubes on the surface of Ti-6Al-4V-ELI (extra low interstitials) cancellous bone screws subjected to insertion and removal using bone simulant. Measuring the torque during insertion in bone simulant was performed to provide input loads to a finite element model to predict the survivability of the titania nanotubes. Scanning electron microscopy was used to investigate the nanotube morphology before and after the insertion and removal tests. A finite element model using experimental insertion torque data estimated the maximum von-Mises stress in the titanium oxide nanotubes. The model predicted that the maximum von-Mises stress in the nanotubes due to combined compression and shear loading is well below the yield failure. Scanning electron microscopy observation confirmed the presence and survivability of the nanotubes after being subjected to multiple insertions and removals of the screws.