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Nanoscale extracellular vesicle (EVs) have been found to play a key role in intercellular communication, offering opportunities for both diagnostics and therapeutics. However, lying below the diffraction limit and also being highly heterogeneous in their size, morphology and abundance, these vesicles pose significant challenges for their physical characterization. Here, we present a direct visual approach for their accurate morphological and size-based profiling by using scanning electron microscopy (SEM). To achieve that, we methodically examined various process steps and developed a protocol to improve the throughput, conformity and image quality while preserving the shape of EVs. The investigation was performed with small EVs (sEVs) isolated from a non-small cell lung cancer (NSCLC) cell line H1975 as well as from a human serum, and the results were compared with those obtained from nanoparticle tracking analysis (NTA). While the comparison of the sEV size distributions showed good agreement between the two methods for large sEVs (diameter >70 nm), the microscopy based approach showed a better capacity for analyses on smaller vesicles, with higher sEV counts compared to NTA. In addition, we demonstrated the possibility of identifying non-EV particles based on size and morphological features. The study also showed process steps that can generate artifacts bearing resemblance with sEVs. The results therefore present a simple way to use a widely available microscopy tool for accurate and high throughput physical characterization of EVs.

Nanosized extracellular vesicles (EVs) have been found to play a key role in intercellular communication, offering opportunities for both disease diagnostics and therapeutics. However, lying below the diffraction limit and also being highly heterogeneous in their size, morphology and abundance, these vesicles pose significant challenges for physical characterization. Here, we present a direct visual approach for their accurate morphological and size-based profiling by using scanning electron microscopy (SEM). To achieve that, we methodically examined various process steps and developed a protocol to improve the throughput, conformity and image quality while preserving the shape of EVs. The study was performed with small EVs (sEVs) isolated from a non-small-cell lung cancer (NSCLC) cell line as well as from human serum, and the results were compared with those obtained from nanoparticle tracking analysis (NTA). While the comparison of the sEV size distributions showed good agreement between the two methods for large sEVs (diameter > 70 nm), the microscopy based approach showed a better capacity for analyses of smaller vesicles, with higher sEV counts compared to NTA. In addition, we demonstrated the possibility of identifying non-EV particles based on size and morphological features. The study also showed process steps that can generate artifacts bearing resemblance with sEVs. The results therefore present a simple way to use a widely available microscopy tool for accurate and high throughput physical characterization of EVs.

We describe a sensing system that is able to measure pH in-vivo, in the rumen of a cow, in real time. The sensing principle is based on gravimetric transduction using a magnetoelastic ribbon functionalized by pH-sensitive nanobeads that is placed in the rumen where it is actuated and read-out wirelessly. We describe a generic procedure that enables one to deposit monolayers or multilayers of nano- and micro beads onto virtually any substrate. The topography of the resulting layers as well as interlayer coverages were characterised using optical microscopy and scanning profilometry. First we determined performance of the system in-vitro, in phosphate-buffered saline, in McDougall’s buffer and in a rumen fluid. Thereafter we also performed in-vivo measurements. Using buffers we determined pH response in the liquids both at the fundamental frequency of the functionalised foils, and at the 1st overtone. We argue that observed frequency changes vs pH are mainly due to changes of trapped liquid when the bead layers shrink or expand as a response to changed pH. The data obtained from the pH response of magnetoelastic foils at different bead coverages was modelled by a simple two-parameter model that corroborates this assumption.

We follow template-binding induced aggregation of nanoparticles enantioselectively imprinted against (S)-propranolol, and the non-imprinted ones, using photon correlation spectroscopy (dynamic light scattering). The method requires no separation steps. We have characterized binding of (R,S)-propranolol to the imprinted polymers and determined the degree of non-specificity by comparing the specific binding with the results obtained using non-imprinted nanoparticles. Using (S)-propranolol as a template for binding to (S)-imprinted nanoparticle, and (R)-propranolol as a non-specific control, we have determined range of concentrations where chiral recognition can be observed. By studying aggregation induced by three analytes related to propranolol, atenolol, betaxolol, and 1-amino-3-(naphthalen-1-yloxy)propan-2-ol, we were able to determine which parts of the template are involved in the specific binding, discuss several details of specific adsorption, and the structure of the imprinted site. Copyright (c) 2014 John Wiley & Sons, Ltd. (Less)

Obtaining more data for the research/studies of plants growing may be easier realized when suitable non-destructive detection methods are available. We are here presenting the development of a miniaturised, low-power, real-time, multi-parameter and cost-effective sensor for measurements in mini plugs (growth of seedling). The detection technique is based on measurement of electrical impedance at two frequencies for sensing two soil parameters, water content and water conductivity (dependent on e.g. total ions concentration). Electrical models were developed and comply with data at two frequencies. An easy and efficient calibration method for the sensor is established by using known liquids’ properties instead of various soil types. The measurements show a good correlation between the sensor’s readings and the traditional soil testing. This soil sensor can easily send data wirelessly allowing for spot checks of substrate moisture levels throughout a greenhouse/field, and/or enable sensors to be buried inside the soil/substrate for long-term consecutive measurements.

Self contained closed circuit rebreathers are life supporting breathing systems, where the exhaled gas is recycled by filtering CO2 and replacing metabolized O2. For the O2 injection control galvanic O2 sensors are used to measure the partial pressure of O2. A malfunction of the sensors can lead to a gas mixture beyond life supporting limits which is life threatening. Galvanic O2 sensors are often used in anaesthetic machines in hospitals. Also in this case, a malfunction of the sensors can cause severe injury to a person. It is obvious that such sensors are key elements in life supporting equipment and as such must be designed in order to achieve high functional safety. However these sensors are consuming sensors, and with that, will fail at a certain time. Failure modes include current limitation, non linearity, electrolyte evaporation or leakage, etc. Within this paper a novel low cost read out electronic circuit for galvanic O2 sensors is presented, which allows not only digital readout, digital temperature compensation, on board storage of calibration and manufacturing data, but also can be used for performing voltammetry cycles to test the Pb anode for exhaustion. First measurements are presented and compared to data from a Solartron SI 1287 impedance analyzer, which is state-of-the-art in electrochemical sensor characterization.

Molecularly imprinted polymers (MIPs) are gaining great interest as tailor-made recognition materials for the development of biomimetic sensors. Various approaches have been adopted to interface MIPs with different transducers, including the use of pre-made imprinted particles and the in situ preparation of thin polymer layers directly on transducer surfaces. In this work we functionalized quartz crystal microbalance (QCM) sensor crystals by coating the sensing surfaces with pre-made molecularly imprinted nanoparticles. The nanoparticles were immobilized on the QCM transducers by physical entrapment in a thin poly(ethylene terephthalate) (PET) layer that was spin-coated on the transducer surface. By controlling the deposition conditions, it was possible to gain a high nanoparticle loading in a stable PET layer, allowing the recognition sites in nanoparticles to be easily accessed by the test analytes. In this work, different sensor surfaces were studied by micro-profilometry and atomic force microscopy and the functionality was evaluated using quartz crystal microbalance with dissipation (QCM-D). The molecular recognition capability of the sensors were also confirmed using radioligand binding analysis by testing their response to the presence of the test compounds, (R)- and (S)-propranolol in aqueous buffer.

In order to detect fast changes of the Brownian relaxation time due to reaction kinetics on the surface of magnetic particles or particle-clustering processes, we have developed a method that uses pulsed magnetic fields and detects the relaxation of the magnetic response on the time scale of milliseconds. We compared measurements in the frequency domain with the time domain measurement using particle suspensions with three different median sizes. The results obtained with the two methods agreed well. Time domain determination of Brownian relaxation was then used to study the reaction kinetics of the clustering process when sodium chloride solution was added to a magnetic nanoparticle suspension.

Molecularly imprinted polymers (MIPs) are being increasingly used as selective adsorbents in different analytical applications. To satisfy the different application purposes, MEN with well controlled physical forms in different size ranges are highly desirable. For examples, MIP nanoparticles are very suitable to be used to develop binding assays and for microfluidic separations, whereas MIP beads with diameter of 1.5-3 mu m can be more appropriate to use in new analytical liquid chromatography systems. Previous studies have demonstrated that imprinted microspheres and nanoparticles can be synthesized using a simple precipitation polymerization method. Despite that the synthetic method is straightforward, the final particle size obtained has been difficult to adjust for a given template. In this work, we initiated to study new synthetic conditions to obtain MIP beads with controllable size in the nano- to micro-meter range, using racemic propranolol as a model template. Varying the composition of the cross-linking monomer allowed the particle size of the MIP beads to be altered in the range of 130 nm to 2.4 mu m, whereas the favorable binding property of the imprinted beads remained intact. The chiral recognition sites were further characterized with equilibrium binding analysis using tritium-labeled (S)-propranolol as a tracer. In general, the imprinted sites displayed a high chiral selectivity: the apparent affinity of the (S)-imprinted sites for (S)-propranolol was 20 times that of for (R)-propranolol. Compared to previously reported irregular particles, the chiral selectivity of competitive radioligand binding assays developed from the present imprinted beads has been increased by six to seven folds in an optimized aqueous solvent. (c) 2006 Elsevier B.V. All rights reserved. (Less)

Ultraviolet (UV) treatment is an effective method for modification of the surface properties of polymeric materials. In this study, the effects of the ozone-generating UV light treatment of thin high-density polyethylene (HDPE) films were monitored with the quartz crystal microbalance (QCM) technique both in the presence of ozone and without it. The films were further characterized by X-ray photoelectron spectroscopy, optical microscopy, and atomic force microscopy. We found that the ozone not only modified the surface properties of the HDPE films but also etched away the polymer layer. An average etching rate of 0.48 nm/min was determined. UV light exposure of the polymer film in an argon atmosphere resulted only in minor degradation of the films; the presence of ozone was needed to cause the destruction and loss of material. The QCM technique was a straightforward method for the monitoring of the kinetics of the ablation induced by the UV–ozone treatment process. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2833–2839, 2004

We have used magnetic particles to study specific binding of prostate specific antigen (PSA) to the surfaces of the bioparticles. The used particles have a mean diameter of about 130 nm and are placed in phosphate buffer saline (PBS). Each particle is composed of clusters of magnetic single domains of magnetite, which are covered with dextran. Changes in surface chemistry of the particles give rise to a change in the hydrodynamic volume of the particles. The later is mirrored by the changed frequency response of the complex magnetic susceptibility of a fluid containing these particles. Using ordinary induction coils and the lock-in amplifier technique it is possible to measure the complex magnetic susceptibility of the particle solution in a frequency range from about 10 Hz up to 10 kHz. From the measurement of the complex susceptibility versus the excitation frequency (both at the excitation frequency as well as at higher harmonics) we have shown that it is possible to quantitatively study the binding of PSA to the surfaces of the magnetic particles and thus to determine the PSA concentration in solution containing known concentration of nanoparticles functionalised with a monoclonal PSA antibody. Our method allows to perform an immunoassay in a single step and is much faster and cheaper compared to conventional ELISA procedures.

The properties of thin films (0.03−2 μm) of high-density polyethylene spin-coated at elevated temperatures (100−180 °C) onto silicon wafers and evaporated gold films were investigated. The coatings were characterized with respect to thickness (ellipsometry, QCM), chemical composition (ESCA, TOF-SIMS), and morphology (optical microscopy, AFM). Initial deposition temperature was found to be an important process parameter that affected the crystal morphology, uniformity, and thickness of the films. The nucleation and the crystal growth were found to depend on both the substrate type and surface properties, especially at low supercooling. Below a film thickness of 0.1 μm, the morphology was composed of aggregates of edge-on oriented lamellae instead of the flattened spherulitic structure observed in thicker films. This thickness dependence of the morphology ceased when the spin-coating was performed at the lowest process temperature, since crystallization probably occurred in the presence of solvent, rather t...

The adsorption of glycine deposited at 95 K on the graphite basal (0001) plane was studied from submonolayer to multilayer coverages by thermal desorption spectroscopy (TDS) and high- resolution electron loss spectroscopy (HREELS). At all coverages glycine adsorbs in three-dimensional (3D) clusters (no distinct monolayer formation was observed). Glycine molecules desorb around 300 K in a single desorption peak (α peak) with a binding energy of 0.85 eV, representing the cohesive energy of glycine. HREELS analysis of these overlayers is severely hampered by charging of the 3D clusters; only one vibrational feature at 26 meV was observed reproducibly. The glycine adlayers are very sensitive to electron irradiation. This effect was studied in some detail by TDS. Electrons of ∼50 eV energy cause: (i) conversion of glycine molecules from the α state to (surprisingly) a more weakly bound β state (desorption temperature ∼250 K), interpreted as 2D adsorbates, and (ii) dissociation of glycine into fragments that ei...

Iron in amphibole asbestos is implicated in the pathogenicity of inhaled fibers. Evidence includes the observation that iron chelators can suppress fiber-induced tissue damage. This is believed to occur via the diminished production of fiber-associated reactive oxygen species. The purpose of this study was to explore possible mechanisms for the reduction of fiber toxicity by iron chelator treatments. We studied changes in the amount and the oxidation states of bulk and surface iron in crocidolite and amosite asbestos that were treated with iron-chelating desferrioxamine, ferrozine, sodium ascorbate, and phosphate buffer solutions. The results have been compared with the ability of the fibers to produce free radicals and decompose hydrogen peroxide in a cell-free system in vitro. We found that chelators can affect the amount of iron at the surface of the asbestos fibers and its valence, and that they can modify the chemical reactivity of these surfaces. However, we found no obvious or direct correlations between fiber reactivity and the amount of iron removed, the amount of iron at the fiber surface, or the oxidation state of surface iron. Our results suggest that surface Fe3+ ions may play a role in fiber-related carboxylate radical formation, and that desferrioxamine and phosphate groups detected at treated fiber surfaces may play a role in diminishing and enhancing, respectively, fiber redox activity. It is proposed that iron mobility in the silicate structure may play a larger role in the chemical reactivity of asbestos than previously assumed.

The adsorption and desorption of in situ deposited glycine on Pt(111) were investigated with thermal desorption spectroscopy (TDS) and X-ray photoelectron spectroscopy (XPS). Glycine adsorbs intact on Pt(111) at all coverages at temperatures below 250 K. The collected results suggest that the glycine molecules adsorb predominantly in the zwitterionic state both in the first monolayer and in multilayers. Upon heating, intact molecules start to desorb from multilayers around 325 K. The second (and possibly third) layer(s) are somewhat more strongly bound than the subsequent layers. The multilayer desorption follows zero order kinetics with an activation energy of 0.87 eV molecule −1 . From the first saturated monolayer approximately half of the molecules desorbs intact with a desorption peak at 360 K, while the other half dissociates before desorption. Below 0.25 monolayer all molecules dissociate upon heating. The dissociation reactions lead to H 2 , CO 2 , and H 2 O desorption around 375 K and CO desorption around 450 K. This is well below the reported gas phase decomposition temperature of glycine, but well above the thermal desorption temperatures of the individual H 2 , CO 2 , and H 2 O species on Pt(111), i.e. the dissociation is catalyzed by the surface and H 2 , CO 2 , and H 2 O immediately desorb upon dissociation. For temperatures above 500 K the remaining residues of the dissociated molecules undergo a series of reactions leading to desorption of, for example, H 2 CN, N 2 and C 2 N 2 , leaving only carbon left on the surface at 900 K. Comparison with previously reported studies of this system show substantial agreement but also distinct differences.

We have measured the energy dissipation of the quartz crystal microbalance (QCM), operating in the liquid phase, when mono- or multi-layers of biomolecules and biofilms form on the QCM electrode (with a time resolution of ca. 1 s). Examples are taken from protein adsorption, lipid vesicle adsorption and cell adhesion studies. Our results show that even very thin (a few nm) biofilms dissipate a significant amount of energy owing to the QCM oscillation. Various mechanisms for this energy dissipation are discussed. Three main contributions to the measured increase in energy dissipation are considered. (i) A viscoelastic porous structure (the biofilm) that is strained during oscillation, (ii) trapped liquid that moves between or in and out of the pores due to the deformation of the film and (iii) the load from the bulk liquid which increases the strain of the film. These mechanisms are, in reality, not entirely separable, rather, they constitute an effective viscoelastic load. The biofilms can therefore not be considered rigidly coupled to the QCM oscillation. It is further shown theoretically that viscoelastic layers with thicknesses comparable to the biofilms studied in this work can induce energy dissipation of the same magnitude as the measured ones.

We follow template-binding induced aggregation of nanoparticles enantioselectively imprinted against (S)-propranolol, and the non-imprinted ones, using photon correlation spectroscopy (dynamic light scattering). The method requires no separation steps. We have characterized binding of (R,S)-propranolol to the imprinted polymers and determined the degree of non-specificity by comparing the specific binding with the results obtained using non-imprinted nanoparticles. Using (S)-propranolol as a template for binding to (S)-imprinted nanoparticle, and (R)-propranolol as a non-specific control, we have determined range of concentrations where chiral recognition can be observed. By studying aggregation induced by three analytes related to propranolol, atenolol, betaxolol, and 1-amino-3-(naphthalen-1-yloxy)propan-2-ol, we were able to determine which parts of the template are involved in the specific binding, discuss several details of specific adsorption, and the structure of the imprinted site.

The influence of oxygen on the hydrogen uptake by Pd-coated Mg films was investigated, by exposing the Mg films to various amounts of oxygen, after deposition of the Mg film but before deposition of the Pd layer. The hydrogen uptake rate of these PdMgOxMg samples shows a peculiar dependence on the thickness of the MgOx layer. For thin oxide layers (small added amounts of oxygen) the hydrogen rate uptake increases, compared with pure PdMg samples. Thicker oxide films (larger amounts of added oxygen) cause a monotonic decline of the hydrogen uptake rate. However, even very large oxygen exposures/uptakes cannot prevent hydrogen uptake completely. MgOx is thus only a partial but not a perfect diffusion barrier for hydrogen. Repeated hydriding-dehydriding cycles increase the hydrogen uptake rate by PdMgOxMg samples, compared with the rate during the first cycle. The results are discussed in terms of a combined effect of the MgOx, layer, affecting both hydrogen transport and nucleation of the hydride phase.

Resistivity measurements were performed during hydriding—decomposition cycles of UHV-prepared Mg films. The hydrogen exposures were made in situ at pH2 = 0.6 torr and 350 K. To obtain measurable uptake rates at these conditions a thin layer of Pd (≈ 7 nm) was deposited on top of the typically 380 nm thick Mg films. Mg and Pd film thicknesses and hydrogen uptakes were determined by the frequency shift of a quartz crystal microbalance (QCM). Both the QCM and the quartz substrate onto which the Mg resistor film was deposited were mounted on the same sample holder. The p, T conditions were chosen so that hydrogen was distributed nearly homogeneously through the sample. The total hydrogen uptakes were in most cases kept small (

Glycine (GL) overlayers of varying thickness were deposited in situ on the clean Pt(111) surface by evaporating commercially available glycine powder. The temperature-stabilized evaporation source, made of Cu, was kept at 420 K during evaporation. The distance between Pt and the evaporation source was about 240 mm. The deposition rate and the total amount of glycine deposited were monitored by a quartz crystal microbalance that could be moved to intersect the GL beam approximately 40 mm downstream compared to the Pt position. The total amount of glycine in the reproduced spectra was 34 (∼0.5 ML) and 340 ng/cm2 (∼ 5 ML), respectively. We discuss the spectra with reference to both the neutral and zwitterionic states. There are two glycine-related C 1s peaks at both low and high GL coverages and a shoulder at ∼ 285 eV most probably due to partial decomposition of glycine inside the evaporation source, at least for a thicker GL layer. The C 1s peak at lower binding energy is usually attributed to the C 1s car...

Commercially pure (c.p., 99.6%) titanium and the Ti6Al4V alloy are widely used in biomedical applications. The surface (oxide) properties of these materials play a key role for their function in biomaterial applications, and it is therefore important to analyze their surface composition. XPS survey and high resolution spectra (Ti 2p, O 1s, and C 1s) are presented from three commercially available dental implants, all manufactured by machining but with different post treatments (grit blasting, cleaning, sterilizing, and packaging). Comparison is made with a TiO2 single crystal (rutile (110)) reference sample, and with Ti and Ti6Al4V foils prepared by the following treatments commonly used for titanium biomaterials: ASTM F86/B600 passivation, electropolishing in perchloric acid based electrolyte, anodization in sulfuric acid and phosphoric acid, and glow discharge plasma oxidation. Survey spectra from the implants are qualitatively similar but quantitatively different, with Ti, O, and C as the main elements...

The adsorption on a gold surface of 5–50-nm silica particles in solution has been studied by the piezoelectric quartz crystal microbalance technique. The parameters of the solution where a reproducible layer by layer deposition is possible have been characterized. The uptake depends strongly on the ionic strength of the solution, but only weakly on the particle size or concentration. The strong dependence on ionic strength is attributed to electrostatic screening.

An experimental setup has been constructed for simultaneous measurements of the frequency, the absolute Q factor, and the amplitude of oscillation of a quartz crystal microbalance (QCM). The technical solution allows operation in vacuum, air, or liquid. The crystal is driven at its resonant frequency by an oscillator that can be intermittently disconnected causing the crystal oscillation amplitude to decay exponentially. From the recorded decay curve the absolute Q factor (calculated from the decay time constant), the frequency of the freely oscillating crystal, and the amplitude of oscillation are obtained. All measurements are fully automated. One electrode of the QCM in our setup was connected to true ground which makes possible simultaneous electrochemistry. The performance is illustrated by experiments in fluids of varying viscosity (gas and liquid) and by proteinadsorptionin situ. We found, in addition to the above results, that the amplitude of oscillation is not always directly proportional to the Q factor, as the commonly used theory states. This puts limitations on the customary use of the amplitude of oscillation as a measure of the Q factor.

Recently developed prototypes of zirconium dioxide and NASICON-based micro solid-state electrolyte oxygen (O2) and carbon dioxide (CO2) sensors were tested for their potential suitability in rebreathers. The O2 sensor has a quasi-indefinite lifetime, whilst that of the CO2 sensor is approximately 700 h. This is a preliminary report of a new technological application.The O2 sensor was tested in a small pressure chamber to a partial pressure of oxygen (PO2) of 405 kPa (4 bar). The CO2 sensor was tested up to 10 kPa CO2. The response times to a step change of pressure were measured, and cross-sensitivity for helium tested using trimix. A rebreather mouthpiece was modified so that breath-by-breath gas recordings could be observed. Power consumption to heat the sensors was measured.The O2 sensor demonstrated non-linearity, particularly above 101.3 kPa (1 bar) PO2, whereas the output of the CO2 sensor showed an inverse logarithmic relationship. Cross-sensitivity to helium was observed. The mean t90 response times were 90 (SD 10) ms for the O2 sensor, and 100 (SD 10) ms for the CO2 sensor. Breath-by-breath recordings showed slight damping of the CO2 trace due to electronic filtering. Power consumption was 1.5-2 W per sensor.The fast response times would allow accurate breath-by-breath measurement. Even though the O2 sensor has a non-linear response, measurement is possible using multi-point calibration. Further design is necessary to allow trimix to be used as the diluent. A major disadvantage is the high power consumption needed to heat the sensors to high temperatures.

Functionalized magnetic nanoparticles are increasingly used as probes in biomolecule detection. We compared two different techniques, which provide information on the state of the magnetic particle system. The dynamics of an ensemble of magnetic nanoparticles was probed measuring the response its magnetisation both on an alternating magnetic field by AC-susceptometry and on a jump of external magnetic field by magnetorelaxometry. In order to compare both techniques, we studied the binding of streptavidin functionalized nanoparticles (fluidMAG/BC-SAV) to biotin-agarose beads and to biotinylated prostate specific antigens (PSA-10). By both techniques we observed specific changes in shape and amplitude of the characteristic signals due the binding of the particles. Therewith the signals of bound and unbound probes can be discriminated and a homogeneous assay without time-comsuming washing steps is realized. The AC susceptometry method provides a robust and sensitive measurement technology. Magnetorelaxometry, utilizing superconducting quantum interference devices (SQUIDs) as magnetic field sensors, owns a much shorter measurement time and has the potential of an even higher sensitivity, at the expense of a considerably increased technological effort.

The reported anomalous “up-hill” diffusion of hydrogen in PdPt and PdAg alloys is explained in terms of attractive, long-range, non-local, elastic interactions between dissolved hydrogen atoms. A statistical model based on the continuum elasticity theory is presented, and model calculations for the Pd 81 Pt 19 system are shown to give results that are in semi-quantitative agreement with experimental data.

We developed nanoparticles with tailored magnetic properties for direct and sensitive detection of biomolecules in biological samples in a single step. Thermally blocked nanoparticles obtained by thermal hydrolysis, functionalized with specific ligands, are mixed with sample solutions, and the variation of the magnetic relaxation due to surface binding is used to detect the presence of biomolecules. The binding significantly increases the hydrodynamic volume of nanoparticles, thus changing their Brownian relaxation frequency which is measured by a specifically developed AC susceptometer. The system was tested for the presence of Brucella antibodies, a dangerous pathogen causing brucellosis with severe effects both on humans and animals, in serum samples from infected cows and the surface of the nanoparticles was functionalized with lipopolysaccharides (LPS) from Brucella abortus. The hydrodynamic volume of LPS-functionalized particles increased by 25-35% as a result of the binding of the antibodies, measured by changes in the susceptibility in an alternating magnetic field. The method has shown high sensitivity, with detection limit of 0.05 microg x mL(-1) of antibody in the biological samples without any pretreatment. This magnetic-based assay is very sensitive, cost-efficient, and versatile, giving a direct indication whether the animal is infected or not, making it suitable for point-of-care applications. The functionalization of tailored magnetic nanoparticles can be modified to suit numerous homogeneous assays for a wide range of applications.

With today's developments of biosensors and medical implants comes the need for efficient reduction of nonspecific binding. We report on a comparison of the ability of traditionally used blocking agents and poly(ethylene glycol) (PEG) derivatives to prevent protein adsorption on both gold and polystyrene surfaces. The adsorption kinetics of blocking molecules and proteins was monitored gravimetrically using quartz crystal microbalance with dissipation (QCM-D). The resistance to nonspecific adsorption was evaluated on gold and polystyrene surfaces coated with bovine serum albumin (BSA) or casein, gold coated with three different 6-11 ethylene glycol (EG) long hydroxyl- or methoxy-terminated PEG-thiolates and polystyrene blocked with a PLL-g-PEG or three different 12 EG long benzyl-PEG-derivatives. The prevention of protein adsorption on the coated surfaces was evaluated by monitoring the mass uptake at the addition of both pure prostate specific antigen (PSA) and seminal plasma. We demonstrate that on pure gold the PEG-thiols are superior to the other blocking molecules tested, with the end group and length of the PEG-thiols used being of minor importance. On polystyrene surfaces blocking with PLL-g-PEG, BSA and casein gave the best results. These results have an impact on further development of an optimized immunoassay protocol.

The phase diagram of the hydrogen-magnesium system, and the associated uptake-decomposition kinetics, have been measured in the pressure range 0.01–0.6 Torr, i.e. at 105 times lower pressure than previously reported, and in the temperature range 290–370 K. The measurements were performed using thin, ultrahigh vacuum evaporated samples of magnesium covered with a thin palladium coating. Hydrogen uptake was measured by a piezoelectric quartz crystal microbalance on which the samples were deposited. Sample purity was controlled by Auger electron spectroscopy and X-ray photoelectron spectroscopy. In a limited pressure-temperature regime, equilibrium can be established between H2 gas and magnesium at isothermal conditions. The experimental data in this region reveal several features not previously reported for the H-Mg system. In the α phase, fast kinetics and p 1 2 dependence of the uptake at low hydrogen concentrations are followed by a stronger p dependence and accompanying slower kinetics at concentrations of about [H] [Mg] ≈ 0.01 . The latter observation may indicate the onset of attractive H-H interaction at concentrations below the solvus. In the α + β phase, the absorption and decomposition isotherms (plateau pressures) are widely separated in pressure, i.e. large hysteresis effects are observed. The enthalpies of hydride formation and decomposition derived from the measured plateau pressures are 60.7 ± 6.3 kJ mol − 1 H2 and 71 ± 4.2 kJ mol − 1 H2 respectively. The measured decomposition plateau pressures agree well with extrapolations from reported high pressure measurements. The results obtained in this work are compared, whenever possible, with the available high temperature data for the H2-Mg system, and with other metal-hydrogen systems.

We study the behavior of Molecularly Imprinted Polymers (MIP) as novel synthetic receptor layers in biochemical sensors. Electropolymerization was used as an easy to implement method for polymer deposition and integrated impedance spectroscopy to monitor MIP behavior towards target molecules. Contrary to what is reported in the literature we consider that it is neither easy nor reliable to attribute the impedance changes to target binding/elution. However, alternative and/or more precise characterization methods are needed to track nano-scale changes in MIPs. Thus we are developing an optical set-up for detection of static deflections on the micro-cantilevers as a result of surface stress induced by changes in MIPs. Using an optical set-up, changes in the deflection of MIP-covered micro-cantilevers when exposed to the target molecules could be measured.

The present study was designed to investigate the long-term bone response around machined screw-type uncoated and calcium phosphate (CaP) -coated commercially pure titanium implants.Using a magnetron sputtering technique, implants with a CaP coating similar in composition and CaP ratio to hydroxyapatite were produced. Heat treatment was subsequently used to increase the crystallinity of the coatings. Four types of coatings (0.1 and 2.0 microm amorphous and 0.1 and 2.0 microm crystalline) were manufactured; uncoated implants served as a control. Three hundred twenty implants (64 of each type) were randomly placed in the tibial cortical and trabecular femoral bones of 40 rabbits. The rabbits were sacrificed 9 months after implant placement.Histomorphometric evaluation carried out on ground sections revealed that the crystalline CaP coatings achieved the highest bone-implant contact in both tibiae and femora compared with amorphous CaP-coated and uncoated titanium.The present study suggests that submicron crystalline hydroxyapatite coating adds bioactive properties to titanium oral implants.An ultra-thin, 0.1-microm crystalline CaP coating can elicit and maintain an improved long-term bone response compared to amorphous coated or uncoated Ti implants, without any adverse tissue reactions.

Background: It has been suggested that calcium phosphate (CaP) coatings initiate faster bone growth around implants. A major concern about the viable use of these coatings has been their biologic performance related to the coating characteristics. Purpose: The purpose of this study was to investigate the early bone response to micron- and submicron-thick hydroxya-patite (HA) coatings in cortical and trabecular bone. Materials and Methods: CaP coatings were manufactured by magnetron sputtering. Heat treatment was subsequently used to increase the crystallinity of the coatings. Coatings were characterized by x-ray diffraction, Fourier transform infrared spectroscopy, inductively coupled plasma optical emission spectroscopy (ICP-OES), and stylus profilometry. Four types of CaP-coated implants were used (0.1 urn and 2.0 μm amorphous; 0.1 um and 2.0 μn crystalline); uncoated machined commercially pure titanium implants served as controls. Four hundred eighty implants were randomly placed in 60 rabbits. Ten animals were followed up for 1 week, 10 for 3 weeks, and 40 for 6 weeks. The bone response was histomorphometrically evaluated. Results: Coatings with a CaP ratio very close to that of HA were produced. Crystalline coatings significantly improved the early bone-implant contact whereas the amorphous-coated implants behaved similarly to uncoated titanium. Conclusions: Crystalline CaP coatings 100 nm thick on titanium implants elicited an improved early bone response compared with that of uncoated titanium implants. No further improvement in the bone response was observed with 2 μm coatings.

Titanium implants have been used widely and successfully for various types of bone-anchored reconstructions. It is believed that properties of oxide films covering titanium implant surfaces are of crucial importance for a successful osseointegration, in particular at compromized bone sites. The aim of the present study is to investigate the surface properties of anodic oxides formed on commercially pure (c.p.) titanium screw implants as well as to study 'native' oxides on turned c.p. titanium implants. Anodic oxides were prepared by galvanostatic mode in CH3COOH up to the high forming voltage of dielectric breakdown and spark formation. The oxide thicknesses, measured with Auger electron spectroscopy (AES), were in the range of about 200-1000 nm. Barrier and porous structures dominated the surface morphology of the anodic film. Quantitative morphometric analyses of the micropore structures were performed using an image analysis system on scanning electron microscopy (SEM) negatives. The pore sizes wereor = 8 microm in diameter and had 1.27-2.1 microm2 opening area. The porosity was in the range of 12.7-24.4%. The surface roughness was in the range of 0.96-1.03 microm (Sa), measured with TopScan 3D. The crystal structures of the titanium oxide were amorphous, anatase, and a mixtures of anatase and rutile type, as analyzed with thin-film X-ray diffractometry (TF-XRD) and Raman spectroscopy. The chemical compositions consisted mainly of TiO2, characterized with X-ray photoelectron spectroscopy (XPS). The native (thermal) oxide on turned implants was 17.4 nm (+/- 6.2) thick and amorphous. Its chemical composition was TiO2. The surface roughness had an average height deviation of 0.83 microm (Sa). The present results are needed to elucidate the influence of the oxide properties on the biological reaction. The results of animal studies using the presently characterized surface oxides on titanium implants will be published separately.

We demonstrate ElectroWetting-On-Dielectric (EWOD) transport and SQUID gradiometer detection of magnetic nanoparticles (MNPs) suspended in a 2 microl de-ionized water droplet. This proof-of-concept methodology constitutes the first development step towards a highly sensitive magnetic immunoassay platform with SQUID readout and droplet-based sample handling. Magnetic AC-susceptibility measurements were performed on MNPs with a hydrodynamic diameter of 100 nm using a high-Tc dc Superconducting Quantum Interference Device (SQUID) gradiometer as detector. We observed that the signal amplitude per unit volume is 2.5 times higher for a 2 microl sample droplet compared to a 30 microl sample volume.

Using magnetic particles with sizes in the nanometer range in biomedical magnetic separation has gained much interest recently due to their higher surface area to particle volume and lower sedimentation rates. In this paper, we report our both theoretical and experimental investigation of the motion of magnetic particles in a magnetic field gradient with particle sizes from 425 nm down to 50 nm. In the experimental measurements, we monitor the absorbance change of the sample volume as the particle concentration varies over time. We also implement a Brownian dynamics algorithm to investigate the influence of particle interactions during the separation and compare it to the experimental results for validation. The simulation agrees well with the measurements for particle sizes around 425 nm. Some discrepancies remain for smaller particle sizes, which may indicate that additional factors also influence the separation for the smaller size range. We observe that the separation process includes the formation of chainlike particle aggregates due to the magnetic dipole-dipole interactions between particles when subjected to an external magnetic field. We can also see that the hydrodynamic interaction between these chains contributes to reducing the separation time. In conclusion, we show that the formation of these particle aggregates, and to a less extent the hydrodynamic interactions between them contributes to significantly enhancing the particle separation process.

Hydrogen uptake by palladium-covered magnesium samples has been studied in the temperature range 260–403 K and the pressure range 0.03–30 Torr. The samples were prepared and measured under ultrahigh vacuum. Typical thicknesses were 600–1300 nm magnesium with a coating of palladium 7–8 nm. The measurements performed were 1. (i) depth profiling of the hydrogen distribution using the 15N method and 2. (ii) measurements of the hydrogen uptake/release using the quartz crystal microbalance (QCM) technique. The profiling provides information about the hydrogen distribution and concentration in the sample. The unusual pressure dependence for the hydrogen uptake, which increases with decreasing pressure, is related to the formation of a hydride in the magnesium near the Pd-Mg interface. The uptake is shown to be kinetically restricted for temperatures close to 296 K and pressures in excess of about 0.01 Torr.