Unusually High Optical Transparency in Hexagonal Nanopatterned Graphene with Enhanced Conductivity by Chemical Doping

Graphene has received appreciable attention for its potential applications in flexible conducting film due to its exceptional optical, mechanical, and electrical properties. However increasing transmittance of graphene without sacrificing the electrical conductivity has been difficult. The fabrication of optically highly transparent (≈98%) graphene layer with a reasonable electrical conductivity is demonstrated here by nanopatterning and doping. Anodized aluminium oxide nanomask prepared by facile and simple self-assembly technique is utilized to produce an essentially hexagonally nanopatterned graphene. The electrical resistance of the graphene increases significantly by a factor of ≈15 by removal of substantial graphene regions via nanopatterning into hexagonal array pores. However, the use of chemical doping on the nanopatterned graphene almost completely recovers the lost electrical conductivity, thus leading to a desirably much more optically transparent conductor having ≈6.9 times reduced light blockage by graphene material without much loss of electrical conductivity. It is likely that the availability of large number of edges created in the nanopatterned graphene provides ideal sites for chemical dopant attachment, leading to a significant reduction of the sheet resistance. The results indicate that the nanopatterned graphene approach can be a promising route for simultaneously tuning the optical and electrical properties of graphene to make it more light-transmissible and suitable as a flexible transparent conductor.

Tantalum coating on TiO2 nanotubes induces superior rate of matrix mineralization and osteofunctionality in human osteoblasts

Nanostructured surface geometries have been the focus of a multitude of recent biomaterial research, and exciting findings have been published. However, only a few publications have directly compared nanostructures of various surface chemistries. The work herein directly compares the response of human osteoblast cells to surfaces of identical nanotube geometries with two well-known orthopedic biomaterials: titanium oxide (TiO2) and tantalum (Ta). The results reveal that the Ta surface chemistry on the nanotube architecture enhances alkaline phosphatase activity, and promotes a ~30% faster rate of matrix mineralization and bone-nodule formation when compared to results on bare TiO2 nanotubes. This study implies that unique combinations of surface chemistry and nanostructure may influence cell behavior due to distinctive physico-chemical properties. These findings are of paramount importance to the orthopedics field for understanding cell behavior in response to subtle alterations in nanostructure and surface chemistry, and will enable further insight into the complex manipulation of biomaterial surfaces. With increased focus in the field of orthopedic materials research on nanostructured surfaces, this study emphasizes the need for careful and systematic review of variations in surface chemistry in concurrence with nanotopographical changes.

Deferoxamine promotes osteoblastic differentiation in human periodontal ligament cells via the nuclear factor erythroid 2-related factor-mediated antioxidant signaling pathway

BACKGROUND AND OBJECTIVE

Recently it was reported that deferoxamine (DFO), an iron chelator, stimulates bone formation from MG63 and mesenchymal stem cells, but inhibits differentiation in rat calvarial cells; however, the effect of DFO on osteoblastic differentiation in human periodontal ligament cells (hPDLCs) has not been reported. The aim of this study was to investigate the effects and the possible underlying mechanism of DFO on osteoblastic differentiation of hPDLCs.

MATERIAL AND METHODS

The effect of DFO on osteoblast differentiation was determined by the staining intensity of calcium deposits with Alizarin red and by RT-PCR analysis of the expression of osteoblastic markers. Signal transduction pathways were analyzed by western blotting.

RESULTS

DFO increased osteogenic differentiation in a concentration-dependent manner by expression of the mRNA for differentiation markers and calcium nodule formation. Exposure of hPDLCs to DFO resulted in increases in the production of reactive oxygen species and in the levels of nuclear factor erythroid 2-related factor (Nrf2) protein in nuclear extractions, as well as a dose-dependent increase in the expression of Nrf2 target genes, including glutathione (GSH), glutathione S-transferase, γ-glutamylcysteine lygase, glutathione reductase and glutathione peroxidase. Pretreatment with Nrf2 small interfering RNA, GSH depletion by buthionine sulfoximine and diethyl maleate, and with antioxidants by N-acetylcysteine and vitamin E, blocked DFO-stimulated osteoblastic differentiation. Furthermore, pretreatment with GSH depletion and antioxidants blocked DFO-induced p38 MAPK, ERK, JNK and nuclear factor-kappaB pathways.

CONCLUSION

These data indicate, for the first time, that nontoxic DFO promotes osteoblastic differentiation of hPDLCs via modulation of the Nrf2-mediated antioxidant pathway.

Hybrid micro/nano-topography of a TiO2 nanotube-coated commercial zirconia femoral knee implant promotes bone cell adhesion in vitro

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.

Fabrication of thin film TiO2 nanotube arrays on Co-28Cr-6Mo alloy by anodization

Titanium oxide (TiO2) nanotube arrays were prepared by anodization of Ti/Au/Ti trilayer thin film DC sputtered onto forged and cast Co-28Cr-6Mo alloy substrate at 400 °C. Two different types of deposited film structures (Ti/Au/Ti trilayer and Ti monolayer), and two deposition temperatures (room temperature and 400 °C) were compared in this work. The concentrations of ammonium fluoride (NH4F) and H2O in glycerol electrolyte were varied to study their effect on the formation of TiO2 nanotube arrays on a forged and cast Co-28Cr-6Mo alloy. The results show that Ti/Au/Ti trilayer thin film and elevated temperature sputtered films are favorable for the formation of well-ordered nanotube arrays. The optimized electrolyte concentration for the growth of TiO2 nanotube arrays on forged and cast Co-28Cr-6Mo alloy was obtained. This work contains meaningful results for the application of a TiO2 nanotube coating to a CoCr alloy implant for potential next-generation orthopedic implant surface coatings with improved osseointegrative capabilities.

Preparation of near micrometer-sized TiO2 nanotube arrays by high voltage anodization

Highly ordered TiO2 nanotube arrays with large diameter of 680-750 nm have been prepared by high voltage anodization in an electrolyte containing ethylene glycol at room temperature. To effectively suppress dielectric breakdown due to high voltage, pre-anodized TiO2 film was formed prior to the main anodizing process. Vertically aligned, large sized TiO2 nanotubes with double-wall structure have been demonstrated by SEM in detail under various anodizing voltages up to 225 V. The interface between the inner and outer walls in the double-wall configuration is porous. Surface topography of the large diameter TiO2 nanotube array is substantially improved and effective control of the growth of large diameter TiO2 nanotube array is achieved. Interestingly, the hemispherical barrier layer located at the bottom of TiO2 nanotubes formed in this work has crinkles analogous to the morphology of the brain cortex. These structures are potentially useful for orthopedic implants, storage of biological agents for controlled release, and solar cell applications.

Myocardial pharmacokinetics of ebastine, a substrate for cytochrome P450 2J, in rat isolated heart

BACKGROUND AND PURPOSE

It is well established that cytochrome P450 2J (CYP2J) enzymes are expressed preferentially in the heart, and that ebastine is a substrate for CYP2J, but it is not known whether ebastine is metabolized in myocardium. Therefore, we investigated its pharmacokinetics in the rat isolated perfused heart.

EXPERIMENTAL APPROACH

Rat isolated hearts were perfused in the recirculating mode with ebastine for 130 min. The concentrations of ebastine and its metabolites, hydroxyebastine and carebastine, were measured using liquid chromatography with a tandem mass spectrometry. The data were analysed by a compartmental model. The time course of negative inotropic response was linked to ebastine concentration to determine the concentration-effect relationship.

KEY RESULTS

Ebastine was metabolized to an intermediate compound, hydroxyebastine, which was subsequently further metabolized to carebastine. No desalkylebastine was found. The kinetics of the sequential metabolism of ebastine was well described by the compartmental model. The EC(50) of the negative inotropic effect of ebastine in rat isolated heart was much higher than free plasma concentrations in humans after clinical doses.

CONCLUSIONS AND IMPLICATIONS

The kinetics of ebastine conversion to carebastine via hydroxyebastine resembled that observed in human liver microsomes. The results may be of interest for functional characterization of CYP2J activity in rat heart.

Extreme superomniphobicity of multiwalled 8 nm TiO2 nanotubes

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.

The role of surveillance endoscopy and endosonography after endoscopic ablation of high-grade dysplasia and carcinoma of the esophagus

Barrett's esophagus (BE) with high-grade dysplasia (HGD) or early carcinoma treated with surgery or photodynamic therapy (PDT) is at risk of recurrence. The efficacy of endoscopic ultrasound (EUS) for surveillance after PDT is unknown. Our objective was to determine if EUS is superior to esophagogastroduodenoscopy (EGD) and/or CT scan for surveillance of BE neoplasia after PDT. The study was designed as a retrospective review with the setting as a tertiary referral center. Consecutive patients with BE with HGD or carcinoma in situ treated with PDT were followed with EUS, CT scan and EGD with jumbo biopsies every 1 cm at 3, 4, or 6-month intervals. Exclusion criteria was < 6 months of follow up and/or < 2 EUS procedures. Main outcome measurements were residual or recurrent disease discovered by any method. Results showed that 67/97 patients met the inclusion criteria (56 men and 11 women). Median follow-up was 16 months. Recurrent or residual adenocarcinoma (ACA) was detected in four patients during follow-up. EGD with random biopsies or targeted nodule biopsies detected three patients. EUS with endoscopic mucosal resection of the nodule confirmed T1 recurrence in one of these three. In the fourth patient, CT scan revealed perigastric lymphadenopathy and EUS-FNA (fine needle aspiration) confirmed adenocarcinoma. There were two deaths, one related to disease progression and one unrelated. The rate of recurrent/persistent ACA after PDT was 4/67 = 6%. EUS did not detect disease when EGD and CT were normal. Limitations of this study include non-blinding of results and preferential status of non-invasive imaging (CT) over EUS. Our experience suggests that EUS has little role in the surveillance of these patients, unless discrete abnormalities are found on EGD or cross-sectional imaging.

Effect of manufacturing conditions on the formation of double-walled polymer microspheres

This paper discusses the optimization of the solvent evaporation process to produce double-walled (DW) microspheres in a single-step. Five process variables were studied: polymer solution concentration, polymer weight ratio, polymer solution volume ratios, encapsulation temperature, and air flow rate across the top of the encapsulation vessel. The effects of these variables on the process efficiency (defined here as the percentage of microspheres with a DW configuration compared to the total number of microspheres) were examined. Total polymer concentrations of less than 20% (w/v) produced microspheres with high efficiency, with phase separation consistent across all size fractions in each batch. Changing the volume ratio of the two polymer solutions had no significant effect on the process efficiency. The weight ratio of the polymers greatly influenced the process efficiency, resulting in a low 63% efficiency for the 1:3 Poly-L-lactide (PLLA): Poly(carboxyphenoxypropane-co-sebacic)anhydride 20:80 (P(CPP:SA 20:80)) weight ratio and 0% for the 3:1 weight ratio. The 1:3 weight ratio also caused the polymers to reverse their orientation, although the efficiency for this switch was still relatively low. The temperature of the non-solvent bath affected the efficiency of certain pairs of polymers, but not all. The PLLA/Poly(lactide-co-glycolide) 50:50 (PLGA) pair was most sensitive to temperature, due to the chemical similarity of the two polymers which narrowed the range of acceptable conditions for encapsulation. Pairs of polymers which phase separated readily (e.g. polystyrene and PLLA) were the least sensitive to temperature changes. Process yield and size distribution show no clear trends with respect to air flow rate across the top of the reaction vessel. The efficiency of the process to produce DW microspheres increased and the process time decreased with increasing air flow across the surface of the encapsulation vessel.