Nanofibrils vs nanocrystals bio-nanocomposites based on sodium alginate matrix: An improved-performance study.

To develop bio-nanocomposites using natural biopolymers, nanocomposite films were prepared based on sodium alginate and kapok nanofibrils (CNFs). CNFs when subjected to TEMPO-mediated oxidation gave rise to cellulose nanocrystals (TOCNCs), with carboxyl groups at the surface ( K a / K b = 3.64). The differences between the two types of nanocelluloses (nanofibrils and nanocrystals) and their impact in the preparation of bio-nanocomposites, were studied. When incorporated in the matrix, the CNFs particles have the tendency to form surface aggregation ( K a / K b = 2.37), distorting the alginate network, creating heterogeneous films, with high surface roughness (S a = 29.37 nm), porosity (D p = 0.087 cm2/min) and vulnerability to heat. The TOCNCs present good dispersion creating a 3D network, which forms uniform (D p = 0.122 cm2/min) and homogeneous films, with smooth surface (S a = 16.83 nm). The ultrasonication treatment facilitated the dispersion improving the interfacial interaction between the reinforcing phase and the matrix. The results show the reinforcement potential of kapok nanocellulose in an industrially and medically important biopolymer, sodium alginate, especially when TOCNCs and ultrasonication were used.

Titanium nanostructures for biomedical applications.

Titanium and titanium alloys exhibit a unique combination of strength and biocompatibility, which enables their use in medical applications and accounts for their extensive use as implant materials in the last 50 years. Currently, a large amount of research is being carried out in order to determine the optimal surface topography for use in bioapplications, and thus the emphasis is on nanotechnology for biomedical applications. It was recently shown that titanium implants with rough surface topography and free energy increase osteoblast adhesion, maturation and subsequent bone formation. Furthermore, the adhesion of different cell lines to the surface of titanium implants is influenced by the surface characteristics of titanium; namely topography, charge distribution and chemistry. The present review article focuses on the specific nanotopography of titanium, i.e. titanium dioxide (TiO2) nanotubes, using a simple electrochemical anodisation method of the metallic substrate and other processes such as the hydrothermal or sol-gel template. One key advantage of using TiO2 nanotubes in cell interactions is based on the fact that TiO2 nanotube morphology is correlated with cell adhesion, spreading, growth and differentiation of mesenchymal stem cells, which were shown to be maximally induced on smaller diameter nanotubes (15 nm), but hindered on larger diameter (100 nm) tubes, leading to cell death and apoptosis. Research has supported the significance of nanotopography (TiO2 nanotube diameter) in cell adhesion and cell growth, and suggests that the mechanics of focal adhesion formation are similar among different cell types. As such, the present review will focus on perhaps the most spectacular and surprising one-dimensional structures and their unique biomedical applications for increased osseointegration, protein interaction and antibacterial properties.

Nanoherding: Plasma-Chemical Synthesis and Electric-Charge-Driven Self Organization of SiO2 Nanodots.

We report on the chemical synthesis of the arrays of silicon oxide nanodots and their self-organization on the surface via physical processes triggered by surface charges. The method based on chemically active oxygen plasma leads to the rearrangement of nanostructures and eventually to the formation of groups of nanodots. This behavior is explained in terms of the effect of electric field on the kinetics of surface processes. The direct measurements of the electric charges on the surface demonstrate that the charge correlates with the density and arrangement of nanodots within the array. Extensive numerical simulations support the proposed mechanism and prove a critical role of the electric charges in the self-organization. This simple and environment-friendly self-guided process could be used in the chemical synthesis of large arrays of nanodots on semiconducting surfaces for a variety of applications in catalysis, energy conversion and storage, photochemistry, environmental and biosensing, and several others.

How to control the recombinant prion protein adhesion for successful storage through modification of surface properties.

Depletion of neuroproteins on the inner walls of storage tubes influences the accuracy of tests used for identification of various neurodegenerative disorders. In this paper, a strategy is described for surface modification of Eppendorf tubes leading to non-adhesive properties towards the recombinant human prion proteins (PrPrec(hum)). Tubes were pre-activated by helium plasma and grafted with three diverse coatings: pure poly(N-isopropylacrylamide) (PNIPAM), PNIPAM admixed with either neutral PEG(20)sorbitan monolaurate (PEG(20)) or positively charged cetyl trimethylammonium bromide (CTAB) at varying plasma activation times and polymer to surfactant ratios. New functionalized surfaces were analyzed by goniometry, streaming potential measurement and X-ray photoelectron spectroscopy, whereas the protein adhesion was monitored by enzyme linked immunosorbent assays and confocal microscopy. The mapping of PrPrec(hum) adhesion associated with surface analyses enabled us to determine that no or negligible depletion of PrPrec(hum) can be obtained by surfaces possessing basic component in the range between 50 and 60 mJ m(-2) and streaming potential ζ(7.4) - -50 mV.

Suppression of tritium retention in remote areas of ITER by nonperturbative reactive gas injection.

A technique based on reactive gas injection in the afterglow region of the divertor plasma is proposed for the suppression of tritium-carbon codeposits in remote areas of ITER when operated with carbon-based divertor targets. Experiments in a divertor simulator plasma device indicate that a 4 nm/min deposition can be suppressed by addition of 1 Pa·m³ s⁻¹ ammonia flow at 10 cm from the plasma. These results bolster the concept of nonperturbative scavenger injection for tritium inventory control in carbon-based fusion plasma devices, thus paving the way for ITER operation in the active phase under a carbon-dominated, plasma facing component background.

Selective etching of metallic single-wall carbon nanotubes with hydrogen plasma.

We present Raman scattering and scanning tunnelling microscopy (STM) measurements on hydrogen plasma etched single-wall carbon nanotubes (SWNTs). Interestingly, both the STM and Raman spectroscopy show that the metallic SWNTs are dramatically altered and highly defected by the plasma treatment. In addition, structural characterizations show that metal catalysts are detached from the ends of the SWNT bundles. For semiconducting SWNTs we observe no feature of defects or etching along the nanotubes. Raman spectra in the radial breathing mode region of plasma-treated SWNT material show that most of the tubes are semiconducting. These results show that hydrogen plasma treatment favours etching of metallic nanotubes over semiconducting ones and therefore could be used to tailor the electronic properties of SWNT raw materials.

EXAFS study of NiAl in thin films.

Technologically important coatings of transition-metal aluminides call be produced by thermal or ion beam mixing of multilayer structures sputter deposited on substrates. The quantitative detection of constituents by depth profiling is sufficient to establish the efficiency of mixing methods. However, to decide whether a mixture of nanoparticles or a stoichiometric alloy is formed, EXAFS analysis of the local atomic neighborhood in the film is required. Ni K edge EXAFS spectra are measured on a series of samples of Ni/Al multilayer on Si(111) surface, after ion mixing at different substrate temperatures. The spectra show that with increasing temperature the nickel aluminide phase gradually substitutes the Ni fcc metal phase.

Aseptic meningitis after vaccination against measles and mumps.

This retrospective study (1979 to 1986) investigated the possible etiologic relationship between vaccination and aseptic meningitis in 115 hospitalized children who became ill within 30 days of vaccination with the Leningrad 3 strain of mumps virus and the Edmonston-Zagreb strain of measles virus. The etiologic viral diagnosis was based on serologic tests and the isolation of virus from cell cultures which distinguished between attenuated and "virulent" mumps virus. The incidence of mumps vaccine-associated meningitis was 1/1000 vaccine recipients. In 92% of children the incubation period was 11 to 25 days and 28% had associated swelling of the salivary glands. Sixteen cases (13.9%) had a positive cerebrospinal fluid culture (attenuated mumps virus, 6 cases; "virulent" mumps virus, 7 cases; echoviruses, 3 cases). Clustering of cases, seasonal occurrence and age of the patients suggested causal relationship with the vaccination in the majority of children. In 4 patients with attenuated virus isolation from cerebrospinal fluid the incubation period ranged from 17 to 20 days. Clinical findings did not differ from natural mumps meningitis. The course was uncomplicated and at discharge the patients had no sequelae. Measles virus was never found as a cause of the meningitis. The mumps vaccine virus should be recognized as one of the causative agents of aseptic meningitis in countries where less attenuated mumps vaccine is used.