A novel methodology to study antimicrobial properties of high-touch surfaces used for indoor hygiene applications-A study on Cu metal.

Metal-based high-touch surfaces used for indoor applications such as doorknobs, light switches, handles and desks need to remain their antimicrobial properties even when tarnished or degraded. A novel laboratory methodology of relevance for indoor atmospheric conditions and fingerprint contact has therefore been elaborated for combined studies of both tarnishing/corrosion and antimicrobial properties of such high-touch surfaces. Cu metal was used as a benchmark material. The protocol includes pre-tarnishing/corrosion of the high touch surface for different time periods in a climatic chamber at repeated dry/wet conditions and artificial sweat deposition followed by the introduction of bacteria onto the surfaces via artificial sweat droplets. This methodology provides a more realistic and reproducible approach compared with other reported procedures to determine the antimicrobial efficiency of high-touch surfaces. It provides further a possibility to link the antimicrobial characteristics to physical and chemical properties such as surface composition, chemical reactivity, tarnishing/corrosion, surface roughness and surface wettability. The results elucidate that bacteria interactions as well as differences in extent of tarnishing can alter the physical properties (e.g. surface wettability, surface roughness) as well as the extent of metal release. The results clearly elucidate the importance to consider changes in chemical and physical properties of indoor hygiene surfaces when assessing their antimicrobial properties.

Multi-band effects in in-plane resistivity anisotropy of strain-detwinned disordered Ba(Fe1-xRux)2As2.

In-plane resistivity anisotropy was measured in strain-detwinned as-grown and partially annealed samples of isovalently-substituted [Formula: see text] ([Formula: see text]) and the results were contrasted with previous reports on anneal samples with low residual resistivity. In samples with high residual resistivity, detwinned with application of strain, the difference of the two components of in-plane resistivity in the orthorhombic phase, [Formula: see text], was found to obey Matthiessen rule irrespective of sample composition, which is in stark contrast with observations on annealed samples. Our findings are consistent with two-band transport model in which contribution from high mobility carriers of small pockets of the Fermi surface has negligible anisotropy of residual resistivity and is eliminated by disorder. Our finding suggests that magnetic/nematic order has dramatically different effect on different parts of the Fermi surface. It predominantly affects inelastic scattering for small pocket high mobility carriers and elastic impurity scattering for larger sheets of the Fermi surface.

Universal doping evolution of the superconducting gap anisotropy in single crystals of electron-doped Ba(Fe1-x Rh x )2As2 from London penetration depth measurements.

Doping evolution of the superconducting gap anisotropy was studied in single crystals of 4d-electron doped Ba(Fe1-x Rh x )2As2 using tunnel diode resonator measurements of the temperature variation of the London penetration depth [Formula: see text]. Single crystals with doping levels representative of an underdoped regime x = 0.039 ([Formula: see text] K), close to optimal doping x = 0.057 ([Formula: see text] K) and overdoped x = 0.079 ([Formula: see text] K) and x = 0.131([Formula: see text] K) were studied. Superconducting energy gap anisotropy was characterized by the exponent, n, by fitting the data to the power-law, [Formula: see text]. The exponent n varies non-monotonically with x, increasing to a maximum n = 2.5 for x = 0.079 and rapidly decreasing towards overdoped compositions to 1.6 for x = 0.131. This behavior is qualitatively similar to the doping evolution of the superconducting gap anisotropy in other iron pnictides, including hole-doped (Ba,K)Fe2As2 and 3d-electron-doped Ba(Fe,Co)2As2 superconductors, finding a full gap near optimal doping and strong anisotropy toward the ends of the superconducting dome in the T-x phase diagram. The normalized superfluid density in an optimally Rh-doped sample is almost identical to the temperature-dependence in the optimally doped Ba(Fe,Co)2As2 samples. Our study supports the universal superconducting gap variation with doping and [Formula: see text] pairing at least in iron based superconductors of the BaFe2As2 family.

Magnetic resonance force detection using a membrane resonator.

The availability of compact, low-cost magnetic resonance imaging instruments would further broaden the substantial impact of this technology. We report highly sensitive detection of magnetic resonance using low-stress silicon nitride (SiNx) membranes. We use these membranes as low-loss, high-frequency mechanical oscillators and find they are able to mechanically detect spin-dependent forces with high sensitivity enabling ultrasensitive magnetic resonance detection. The high force detection sensitivity stems from their high mechanical quality factor Q∼10(6)[1,2] combined with the low mass of the resonator. We use this excellent mechanical force sensitivity to detect the electron spin magnetic resonance using a SiNx membrane as a force detector. The demonstrated force sensitivity at 300K is 4fN/Hz, indicating a potential low temperature (4K) sensitivity of 25aN/Hz. Given their sensitivity, robust construction, large surface area and low cost, SiNx membranes can potentially serve as the central component of a compact room-temperature ESR and NMR instrument having spatial resolution superior to conventional approaches.

Adsorption of bovine serum albumin on silver surfaces enhances the release of silver at pH neutral conditions.

Metallic biomaterials are widely used to replace and/or restore the function of damaged bodily parts. The use of silver as antibacterial coatings onto implants has recently gained large interest in medical applications. The extent of silver that can be released into different biological fluids from such coatings is, except for the surface characteristics of the coating, governed by parameters such as protein characteristics, adsorbed layer properties, formation of silver-protein complexes as well as concentrations of proteins in the solution. This study aims to relate the structure of adsorbed net negatively charged bovine serum albumin (BSA), which is the most abundant protein in serum, to the release of silver from metallic silver surfaces in order to elucidate if the net charge of the protein has any effect of the silver release. Simultaneous adsorption measurements were performed in real time on the very same surface using combined ellipsometry and quartz crystal microbalance with dissipation monitoring (QCM-D) measurements to provide a more comprehensive understanding on adsorption kinetics and layer structures. The amount of released silver into solution was measured by means of graphite furnace atomic absorption spectroscopy (GF-AAS). The structure of the adsorbed BSA layer largely influenced the amount of released silver, an enhancement that increased with BSA concentration. These observations are in complete contrast to the effect of net positively charged lysozyme (LSZ) adsorbed on silver, previously studied by the authors, for which a complete surface coverage suppressed the possibility for silver release. The underlying mechanisms behind the enhanced release of silver in the presence of BSA were mainly attributed to surface complexation between BSA and silver followed by an enhanced exchange rate of these surface complexes with BSA molecules in the solution, which in turn increase the amount of released silver in solution.

Sign-reversal of the in-plane resistivity anisotropy in hole-doped iron pnictides.

Unconventional superconductivity usually originates from several strongly coupled degrees of freedom, such as magnetic, charge and elastic. A highly anisotropic electronic phase, not driven by lattice degrees of freedom, has been proposed in some of these superconductors, from cuprates to iron-based compounds. In the iron pnictide BaFe2As2, this nematic phase arises in the paramagnetic phase and is present for wide doping and temperature ranges. Here we probe the in-plane electronic anisotropy of electron- and hole-doped BaFe2As2 compounds. Unlike other materials, the resistivity anisotropy behaves very differently for electron- and hole-type dopants and even changes sign on the hole-doped side. This behaviour is explained by Fermi surface reconstruction in the magnetic phase and spin-fluctuation scattering in the paramagnetic phase. This unique transport anisotropy unveils the primary role played by magnetic scattering, demonstrating the close connection between magnetism, nematicity and unconventional superconductivity.

Surface-protein interactions on different stainless steel grades: effects of protein adsorption, surface changes and metal release.

Implantation using stainless steels (SS) is an example where an understanding of protein-induced metal release from SS is important when assessing potential toxicological risks. Here, the protein-induced metal release was investigated for austenitic (AISI 304, 310, and 316L), ferritic (AISI 430), and duplex (AISI 2205) grades in a phosphate buffered saline (PBS, pH 7.4) solution containing either bovine serum albumin (BSA) or lysozyme (LSZ). The results show that both BSA and LSZ induce a significant enrichment of chromium in the surface oxide of all stainless steel grades. Both proteins induced an enhanced extent of released iron, chromium, nickel and manganese, very significant in the case of BSA (up to 40-fold increase), whereas both proteins reduced the corrosion resistance of SS, with the reverse situation for iron metal (reduced corrosion rates and reduced metal release in the presence of proteins). A full monolayer coverage is necessary to induce the effects observed.

Adsorption and protein-induced metal release from chromium metal and stainless steel.

A research effort is undertaken to understand the mechanism of metal release from, e.g., inhaled metal particles or metal implants in the presence of proteins. The effect of protein adsorption on the metal release process from oxidized chromium metal surfaces and stainless steel surfaces was therefore examined by quartz crystal microbalance with energy dissipation monitoring (QCM-D) and graphite furnace atomic absorption spectroscopy (GFAAS). Differently charged and sized proteins, relevant for the inhalation and dermal exposure route were chosen including human and bovine serum albumin (HSA, BSA), mucin (BSM), and lysozyme (LYS). The results show that all proteins have high affinities for chromium and stainless steel (AISI 316) when deposited from solutions at pH 4 and at pH 7.4 where the protein adsorbed amount was very similar. Adsorption of albumin and mucin was substantially higher at pH 4 compared to pH 7.4 with approximately monolayer coverage at pH 7.4, whereas lysozyme adsorbed in multilayers at both investigated pH. The protein-surface interaction was strong since proteins were irreversibly adsorbed with respect to rinsing. Due to the passive nature of chromium and stainless steel (AISI 316) surfaces, very low metal release concentrations from the QCM metal surfaces in the presence of proteins were obtained on the time scale of the adsorption experiment. Therefore, metal release studies from massive metal sheets in contact with protein solutions were carried out in parallel. The presence of proteins increased the extent of metals released for chromium metal and stainless steel grades of different microstructure and alloy content, all with passive chromium(III)-rich surface oxides, such as QCM (AISI 316), ferritic (AISI 430), austentic (AISI 304, 316L), and duplex (LDX 2205).

Interactions between surfactants and silver nanoparticles of varying charge.

The interaction between silver nanoparticles (Ag NPs) of different surface charge and surfactants relevant to the laundry cycle has been investigated to understand changes in speciation, both in and during transport from the washing machine. Ag NPs were synthesized to exhibit either a positive or a negative surface charge in solution conditions relevant for the laundry cycle (pH 10 and pH 7). These particles were characterized in terms of size and surface charge and compared to commercially laser ablated Ag NPs. The surfactants included anionic sodium dodecylbenzenesulfonate (LAS), cationic dodecyltrimethylammoniumchloride (DTAC) and nonionic Berol 266 (Berol). Surfactant-Ag NP interactions were studied by means of dynamic light scattering, Raman spectroscopy, zeta potential, and Quartz Crystal Microbalance. Mixed bilayers of CTAB and LAS were formed through a co-operative adsorption process on positively charged Ag NPs with pre-adsorbed CTAB, resulting in charge reversal from positive to negative zeta potentials. Adsorption of DTAC on negatively charged synthesized Ag NPs and negatively charged commercial Ag NPs resulted in bilayer formation and charge reversal. Weak interactions were observed for nonionic Berol with all Ag NPs via hydrophobic interactions, which resulted in decreased zeta potentials for Berol concentrations above its critical micelle concentration. Differences in particle size were essentially not affected by surfactant adsorption, as the surfactant layer thicknesses did not exceed more than a few nanometers. The surfactant interaction with the Ag NP surface was shown to be reversible, an observation of particular importance for hazard and environmental risk assessments.

The prevalence of hypothyroidism after treatment for laryngeal and hypopharyngeal carcinomas: are autoantibodies of influence?

CONCLUSIONS: The incidence rate of hypothyroidism after treatment for laryngeal and hypopharyngeal cancer is high, especially after combination treatment. An association between hypothyroidism and autoantibodies was found. OBJECTIVES: The incidences of hypothyroidism and autoantibodies were assessed retrospectively in 156 patients with laryngeal and hypopharyngeal carcinoma who were treated with surgery and/or radiotherapy between 1977 and 2002. PATIENTS AND METHODS: Patients treated for T2-T4 carcinoma or a recurrence after T1 who visited the outpatient clinic for their regular follow-up visit were included. All patients were evaluated for the development of hypothyroidism, defined as increased thyroid-stimulating hormone level (>4.5 mU/L) and the presence of autoantibodies. A questionnaire regarding symptoms was administered. RESULTS: The prevalence of undiagnosed hypothyroidism following treatment of laryngeal carcinoma was 28.2%: 18.6% subclinical hypothyroidism and 9.6% clinical hypothyroidism. The prevalence of circulating antithyroid antibodies (anti-thyreoperoxidase and/or anti-thyreoglobulin) was 10.5%. Univariate analysis showed that patients with laryngectomy, hemithyroidectomy, ipsilateral neck dissection and autoantibodies had a higher risk of hypothyroidism. The combination of surgery and radiotherapy increased the risk. Symptoms such as weight gain and cold intolerance were significantly associated with hypothyroidism. Multivariate analysis showed hemithyroidectomy, autoantibodies, weight gain and cold intolerance to be prognostic factors for the development of hypothyroidism.

Disappearance of anti-Saccharomyces cerevisiae antibodies in coeliac disease during a gluten-free diet.

BACKGROUND: Anti-Saccharomyces cerevisiae antibodies (ASCAs) are known to be positive in about 65% of Crohn's disease patients, in up to 43% of coeliac disease patients and in 0-5% of healthy controls. Coeliac disease might be an in-vivo model for unravelling the role of mucosal integrity in the formation of ASCAs since mucosal abnormalities normalize during a gluten-free diet (GFD). AIMS: Firstly, to evaluate, retrospectively, the frequency of ASCA positivity in coeliac patients both at diagnosis and during follow-up on a GFD. Secondly, to study the correlation between ASCA positivity and mucosal damage. METHODS: One hundred and eleven patients with histologically proven coeliac disease, positive endomysium antibodies on diagnosis and normalization of trans-glutaminase antibodies (t-TGAs) after successful adherence to a GFD were included. ASCAs, IgA and IgG were tested by enzyme-linked immunosorbent assays both at diagnosis and after the GFD. RESULTS: Eighty-three children and 28 adults were included in this study. The mean age at diagnosis was 4.6 years for children and 48 years for adults. At diagnosis 15/83 (18%) of children were ASCA positive (either IgG or IgA), compared to 17/28 (61%) of adults. After successful adherence to a GFD and normalization of t-TGAs only one child remained ASCA positive (1%) compared to eight adults (29%). Two out of 28 (7%) adults remained positive for both IgA and IgG ASCAs. CONCLUSION: In the majority of patients ASCAs disappeared during a GFD. In children this disappearance of ASCA positivity was more pronounced. This can be explained by the well-known fact that gut permeability normalizes much better in children than in adults. Also, the adults had higher levels of ASCAs at diagnosis. This was probably because they had been exposed to gluten for longer and therefore had more long-lasting damage.

Surfaces coated with protein layers: a surface force and ESCA study.

In this review article we discuss the types of non-specific forces that are of importance for the interactions between proteins and surfaces. Some of these forces are well understood theoretically, and their properties investigated in detail. The origin of other types of forces is less well understood, or even controversial, and here we will recapitulate the main experimental findings. Most of our knowledge of interfacial forces stems from the use of various surface force techniques. Two such techniques are described in this article. The typical experimental procedure is outlined and attention is drawn to the most common complications that we have met during our studies. In this article we have chosen to present data that illustrate the presence of some particular type of force, that illustrate a particular complication that occurs when evaluating the experimental findings, or that illustrate the advantage of using electron spectroscopy for chemical analysis (ESCA) in combination with surface force measurements. No system is discussed in detail, and for more detailed information we will refer the reader to the original literature. However, we present an estimate of the amount of small ions co-adsorbed with the protein calculated from a combination of the ESCA and surface force apparatus (SFA) results. This estimate is based on a simple charge balance which requires a knowledge of the adsorbed amount and the diffuse layer charge. The adsorbed amount is obtained from ESCA measurements using a quantification method that utilizes the known chemical composition of the mica surface. The diffuse layer charge is obtained from the magnitude of the double-layer force measured with a surface force technique.