MnO2 Nanoflower Integrated Optoelectronic Biointerfaces for Photostimulation of Neurons.

Optoelectronic biointerfaces have gained significant interest for wireless and electrical control of neurons. Three-dimentional (3D) pseudocapacitive nanomaterials with large surface areas and interconnected porous structures have great potential for optoelectronic biointerfaces that can fulfill the requirement of high electrode-electrolyte capacitance to effectively transduce light into stimulating ionic currents. In this study, the integration of 3D manganese dioxide (MnO2 ) nanoflowers into flexible optoelectronic biointerfaces for safe and efficient photostimulation of neurons is demonstrated. MnO2 nanoflowers are grown via chemical bath deposition on the return electrode, which has a MnO2 seed layer deposited via cyclic voltammetry. They facilitate a high interfacial capacitance (larger than 10 mF cm-2 ) and photogenerated charge density (over 20 µC cm-2 ) under low light intensity (1 mW mm-2 ). MnO2 nanoflowers induce safe capacitive currents with reversible Faradaic reactions and do not cause any toxicity on hippocampal neurons in vitro, making them a promising material for biointerfacing with electrogenic cells. Patch-clamp electrophysiology is recorded in the whole-cell configuration of hippocampal neurons, and the optoelectronic biointerfaces trigger repetitive and rapid firing of action potentials in response to light pulse trains. This study points out the potential of electrochemically-deposited 3D pseudocapacitive nanomaterials as a robust building block for optoelectronic control of neurons.

Mechanisms and Characterization of the Pulsed Electron-Induced Grafting of Styrene onto Poly(tetrafluoroethylene-co-hexafluoropropylene) to Prepare a Polymer Electrolyte Membrane.

During the pulsed-electron beam direct grafting of neat styrene onto poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP) substrate, the radiolytically-produced styryl and carbon-centered FEP radicals undergo various desired and undesired competing reactions. In this study, a high-dose rate is used to impede the undesired free radical homopolymerization of styrene and ensure uniform covalent grafting through 125-µm FEP films. This outweighs the enhancement of the undesired crosslinking reactions of carbon-centered FEP radicals and the dimerization of the styryl radicals. The degree of uniform grafting through 125-µm FEP films increases from ≈8%, immediately after pulsed electron irradiation to 33% with the subsequent thermal treatment exceeding the glass transition temperature of FEP of 39°C. On the contrary, steady-state radiolysis using 60Co gamma radiolysis, shows that the undesired homopolymerization of the styrene has become the predominant reaction with a negligible degree of grafting. Time-resolved fast kinetic measurements on pulsed neat styrene show that the styryl radicals undergo fast decays via propagation homopolymerization and termination reactions at an observed reaction rate constant of 5 × 108 l · mol-1 · s-1. The proton conductivity of 25-µm film at 80°C is 0.29 ± 0.01 s cm-1 and 0.007 s cm-1 at relative humidity of 92% and 28%, respectively. The aims of this work are: 1. electrolyte membranes are prepared via grafting initiated by a pulsed electron beam; 2. postirradiation heat-treated membranes are uniformly grafted, ideal for industry; 3. High dose rate is the primary parameter to promote the desired reactions; 4. measurement of kinetics of undesired radiation-induced styrene homopolymerization; and 5. The conductivity of prepared membranes is on par or higher than industry standards.

Determination of lead ion removal from a flowing electrolyte in the presence of a magnetic field using Raman spectroscopy.

PURPOSE: The authors report on the development of a new, noninvasive method to efficiently remove metal ions in aqueous solution flowing in a tube and to quantify the concentrations of those ions. Such a technique could be used to remove toxic ions in the interiors of arteries and veins in patients intoxicated by the ingestion of metal ions. METHODS: A magnetic field is applied to an aqueous electrolyte flowing in a specially designed rectangular cell in order to deflect the ion trajectories and concentrate them at one side of a cell. Once the ions are concentrated, they can be removed. Raman spectroscopy is used to promptly determine the concentration of the removed lead ions. RESULTS: It is possible to increase, on one side of the cell, the ion concentration by more than 80% with respect to the average concentration; the removed ions were taken from this high concentration region. This approach is a rapid, efficient, and noninvasive method for the removal of ions in aqueous solution. Raman spectroscopy was found to be a suitable technique to determine the amount of removed ions. CONCLUSIONS: The results indicate that the ion concentration can be increased more than 80% in a region where they can be removed. The increment in the ion concentration produced by the deflection due to the magnetic field, together with the use of Raman spectroscopy, allows for a rapid analysis of the removed ions without any previous preparation. The proposed method is a potentially useful method for metal ion separation of interest in the medical physics field.

Surface Disinfection Enabled by a Layer-by-Layer Thin Film of Polyelectrolyte-Stabilized Reduced Graphene Oxide upon Solar Near-Infrared Irradiation.

We report an antibacterial surface that kills airborne bacteria on contact upon minutes of solar near-infrared (NIR) irradiation. This antibacterial surface employs reduced graphene oxide (rGO), a well-known near-infrared photothermal conversion agent, as the photosensitizer and is prepared by assembling oppositely charged polyelectrolyte-stabilized rGO sheets (PEL-rGO) on a quartz substrate with the layer-by-layer (LBL) technique. Upon solar irradiation, the resulting PEL-rGO LBL multilayer efficiently generates rapid localized heating and, within minutes, kills >90% airborne bacteria, including antibiotic-tolerant persisters, on contact, likely by permeabilizing their cellular membranes. The observed activity is retained even when the PEL-rGO LBL multilayer is placed underneath a piece of 3 mm thick pork tissue, indicating that solar light in the near-infrared region plays dominant roles in the observed activity. This work may pave the way toward NIR-light-activated antibacterial surfaces, and our PEL-rGO LBL multilayer may be a novel surface coating material for conveniently disinfecting biomedical implants and common objects touched by people in daily life in the looming postantibiotic era with only minutes of solar exposure.

Ionic electroactive polymer artificial muscles in space applications.

A large-scale effort was carried out to test the performance of seven types of ionic electroactive polymer (IEAP) actuators in space-hazardous environmental factors in laboratory conditions. The results substantiate that the IEAP materials are tolerant to long-term freezing and vacuum environments as well as ionizing Gamma-, X-ray, and UV radiation at the levels corresponding to low Earth orbit (LEO) conditions. The main aim of this material behaviour investigation is to understand and predict device service time for prolonged exposure to space environment.

Effects of genetic strain and light intensity on blood physiological variables of broilers grown to heavy weights.

The effects of genetic strain, light intensity, and their interaction were examined on blood physiological variables of broilers maintained in environmentally controlled rooms in each of 5 trials. The study consisted of a 2 × 5 factorial arranged in a randomized complete block design with 10 treatments of 2 strains (Ross × Ross 308 and 708) and exposure to 5 light intensities (25, 10, 5, 2.5, and 0.2 lx) with chicks equally and randomly distributed at 1 d of age. The 5 light intensities were randomly assigned from 22 to 56 d of age. Feed and water were provided ad libitum. Venous blood samples were collected on d 21 (base line), 28, 42, and 56 of age. Main effects indicate that Ross × Ross 308 significantly (P ≤ 0.05) increased BW, partial pressure of CO2, Ca(2+), Na(+), Cl(-), and thyroxine, along with significantly (P ≤ 0.05) reduced pH level, partial pressure of O2, HCO3(-), and triiodothyronine in comparison with Ross × Ross 708. No main effect of light intensity was observed on all examined variables. In addition, no significant main effects were observed for strain, light intensity, or their interaction on saturated O2, hematocrit, hemoglobin, K(+), mean corpuscular hemoglobin concentration, glucose, osmolality, and anion gap. Physiologically, although Ross × Ross 308 had a significantly increased BW in comparison with Ross × Ross 708, Ross × Ross 708 showed a significant (P ≤ 0.05) increase in partial pressure of O2 and triiodothyronine along with lower blood partial pressure of CO2 and thyroxine. The results of this study supplement current knowledge of physiological response to differing lighting levels and may be used to establish the normal blood values for commercial broilers grown to heavy weights. Plasma corticosterone was not affected by either treatments or strain, indicating that the treatments did not induce physiological stress in broilers.

Laser-induced metal reduction from liquid electrolyte precursor.

A special sort of laser methods such as direct writing of metal and thin film deposition from liquid precursors was developed for the surface processing and the localized metallization of different kinds of materials. Laser radiation initiates the chemical reaction resulted in the reduction of the metal complexes to the metals in the liquid electrolyte, followed by the metal deposition on the substrate with a high degree of the adhesion. In this study, continuous wave of Ar+ laser generated in multiwave regime with laser power from 5 to 500 mW was chosen for the Copper reduction and deposition on SiO2 substrate. In order to investigate the effect of salt precursors on the properties of the deposited structures, two kinds of electrolyte solution were prepared on the base of CuSO4 and CuCl2. It was shown that metal deposition can be initiated at the laser power of 50 mW. The width of the deposits was found to be substantially dependent on the applied laser power. Deposits were revealed as conductive layers and the resistance of the layers depends strongly on the solution temperature and the salt precursor.

Nanometer-scale mapping of irreversible electrochemical nucleation processes on solid Li-ion electrolytes.

Electrochemical processes associated with changes in structure, connectivity or composition typically proceed via new phase nucleation with subsequent growth of nuclei. Understanding and controlling reactions requires the elucidation and control of nucleation mechanisms. However, factors controlling nucleation kinetics, including the interplay between local mechanical conditions, microstructure and local ionic profile remain inaccessible. Furthermore, the tendency of current probing techniques to interfere with the original microstructure prevents a systematic evaluation of the correlation between the microstructure and local electrochemical reactivity. In this work, the spatial variability of irreversible nucleation processes of Li on a Li-ion conductive glass-ceramics surface is studied with ~30 nm resolution. An increased nucleation rate at the boundaries between the crystalline AlPO4 phase and amorphous matrix is observed and attributed to Li segregation. This study opens a pathway for probing mechanisms at the level of single structural defects and elucidation of electrochemical activities in nanoscale volumes.

Nature of inclined growth in thin-layer electrodeposition under uniform magnetic fields.

Electrochemical deposition (ECD) in thin cells in a vertical position relative to gravity, subject to an external uniform magnetic field, yields a growth pattern formation with dense branched morphology with branches tilted in the direction of the magnetic force. We study the nature of the inclined growth through experiments and theory. Experiments in ECD, in the absence of magnetic forces, reveal that a branch grows by allowing fluid to penetrate its tip and to be ejected from the sides through a pair of symmetric vortices attached to the tip. The upper vortices zone defines an arch separating an inner zone ion depleted and an outer zone in a funnel-like form with a concentrated solution through which metal ions are carried into the tip. When a magnetic field is turned on, vortex symmetry is broken, one vortex becoming weaker than the other, inducing an inclination of the funnel. Consequently, particles entering the funnel give rise to branch growth tilted in the same direction. Theory predicts, in the absence of a magnetic force, funnel symmetry induced through symmetric vortices driven by electric and gravitational forces; when the magnetic force is on, it is composed with the pair of clockwise and counterclockwise vortices, reducing or amplifying one or the other. In turn, funnel tilting modifies particle trajectories, thus, growth orientation.

Serum lipids, proteins and electrolyte profiles in rats following total body irradiation.

OBJECTIVE: Serum lipid and electrolyte imbalances are common in critically ill patients undergoing radiation therapy. Although multiple disease states and medication may be responsible for the development of these disorders, the aim of this research is to sequentially document the effect of total body radiation on body function utilizing the sequential changes in the serum lipids, electrolytes and protein in rats. METHODS: Serum protein and lipids contents were assessed using kits while electrolytes were assessed with flame photometry in rats exposed to total body irradiations of 1.27 Gy/min in cumulative doses to the fourth irradiation at five-day intervals. RESULTS: Total cholesterol and triacylglycerols serum levels were significantly reduced by irradiation (p < 0.05). No significant differences between experimental and control groups for HDL-C serum levels were detected. Serum electrolyte concentration remained within the normal range after each total body irradiation. Sodium, bicarbonate and chloride were significantly (p < 0.05) higher than control while potassium and creatinine were significantly reduced after the first irradiation only. Sodium/potassium ratio was significantly (p < 0.05) elevated. Serum protein was significantly (p < 0.05) elevated with increasing radiation. CONCLUSION: There are subtle but significant changes in serum lipids, electrolytes and protein after total body irradiation of normal rats. These variations could be due to non-specific stress reactions; as such, they are important markers in radiation induced injury diagnosis.

Polyelectrolyte wrapping layers control rates of photothermal molecular release from gold nanorods.

Gold nanorods show great promise as light-controlled molecular release systems. Dye molecules were loaded within a variable number of polyelectrolyte multilayers wrapped around gold nanorods. The dye photoinduced release rate depended on the quantity and type of polyelectrolyte trapping layers and could be tuned by a factor of 100. Only two molecular capping layers were sufficient to turn off release. Comparison of the phototriggered molecular release rate to a pure thermal experiment provides an estimate of the effective temperature of the nanorod solution upon irradiation.

All-optical tunability of microdisk lasers via photo-adressable polyelectrolyte functionalization.

Photoactive materials are highly promising candidates for novel applications as they enable all-optical control of photonic devices. Photochromic molecules exhibit a reversible change of their dielectric function upon irradiation with light of proper wavelength. The trans- and cis-isomers of azobenzene exhibit different absorption properties due to the effect of the configuration on the polarizability of the molecule. Here, we introduce a novel molecular/semiconductor hybrid device which is fully tunable by all-optical means via the integration of a semiconductor microdisk into a photo-adressable polyelectrolyte material. We demonstrate that such polyelectrolyte superlattices can be used to tune semiconductor photonic resonators with high precision and without any significant degeneration of device performance. Moreover, we demonstrate an all-optically tunable laser based on this hybrid concept.

Serum lipids, proteins and electrolyte profiles in rats following total body irradiation / Perfiles de lípidos, proteínas y electrolitos plasmáticos en ratas tras irradiación corporal total

OBJECTIVE: Serum lipid and electrolyte imbalances are common in critically ill patients undergoing radiation therapy. Although multiple disease states and medication may be responsible for the development of these disorders, the aim of this research is to sequentially document the effect of total body radiation on body function utilizing the sequential changes in the serum lipids, electrolytes and protein in rats. METHODS: Serum protein and lipids contents were assessed using kits while electrolytes were assessed with flame photometry in rats exposed to total body irradiations of 1.27 Gy/min in cumulative doses to the fourth irradiation at five-day intervals. RESULTS: Total cholesterol and triacylglycerols serum levels were significantly reduced by irradiation (p < 0.05). No significant differences between experimental and control groups for HDL-C serum levels were detected. Serum electrolyte concentration remained within the normal range after each total body irradiation. Sodium, bicarbonate and chloride were significantly (p < 0.05) higher than control while potassium and creatinine were significantly reduced after the first irradiation only. Sodium/potassium ratio was significantly (p < 0.05) elevated. Serum protein was significantly (p < 0.05) elevated with increasing radiation. CONCLUSION: There are subtle but significant changes in serum lipids, electrolytes and protein after total body irradiation of normal rats. These variations could be due to non-specific stress reactions; as such, they are important markers in radiation induced injury diagnosis.

OBJETIVO: Los desequilibrios de lípido y electrolito plasmáticos son comunes en los pacientes críticos sometidos a terapia radioactiva. Aunque los múltiples estados de la enfermedad y la medicación pueden ser responsables del surgimiento de estos trastornos, el objetivo de esta investigación es documentar de manera secuencial el efecto de la radiación corporal total sobre la función corporal, utilizando los cambios secuenciales en los lípidos, electrolitos y proteínas plasmáticos en las ratas. MÉTODOS: Los contenidos de lípidos y proteínas plasmáticos fueron evaluados utilizando kits, en tanto que los electrolitos fueron evaluados mediante fotometría de llama en ratas expuestas a irradiaciones corporales totales de rayos X de 1.27 Gy/min, en dosis cumulativas hasta la cuarta irradiación en intervalos de cinco días. RESULTADOS: El colesterol total y los niveles plasmáticos de triacilgliceroles fueron reducidos significativamente por la irradiación (p < 0.05). No se detectaron diferencias significativas entre; os grupos experimentales y de control en relación con los niveles plasmáticos de colesterol HDL. La concen-tración de electrolito plasmático se mantuvo dentro de los límites normales luego de cada irradiación corporal total de rayos X. La relación sodio/potasio fue significativamente elevada (p < 0.05). La proteína plasmática se elevaba significativamente (p < 0.05) al aumentar la radiación. CONCLUSIÓN: Tras la irradiación corporal total de las ratas normales, seproducen cambios sutiles pero significativos en los lípidos, electrolitos y proteínas del plasma. Estas variaciones podrían ser debidas a reacciones de estrés no específicas, y como tal, son marcadores importantes en el diagnóstico de las lesiones inducidas por la radiación.

Current-induced formation of gradient crystals in block copolymer electrolytes.

Conventional ordered phases such as crystals and liquid crystals have constant domain spacings. In this Letter, we report on the formation of coherently ordered morphologies wherein the domain spacing changes continuously along a specified direction. We have coined the term "gradient crystal" to refer to this structure, a signature of which is a small-angle X-ray scattering pattern that resembles a sundial. Gradient crystals composed of a gyroid morphology form spontaneously when ionic current is driven through a block copolymer electrolyte. We propose that this structure forms because it allows for a continuous change in domain spacing without requiring the introduction of defects. Previous studies have shown that applied electric fields ranging from 1000 to 40,000 V/mm can induce long-range structural order, alignment, and morphological transitions in block copolymers. Gradient crystals form under applied electric fields as low as 2.5 V/mm due to the presence of direct ionic currents that are absent in the aforementioned studies.

Unusual effect of the magnetic field component of the microwave radiation on aqueous electrolyte solutions.

The heating characteristics of aqueous electrolyte solutions (NaCl, KCl, CaCl2, NaBF4, and NaBr) of varying concentrations in ultrapure water by 2.45 GHz microwave radiation from a single-mode resonance microwave device and a semiconductor microwave generator were examined under conditions where the electric field (E-field) was dominant and where the magnetic field (H-field) dominated. Although magnetic field heating is not generally used in microwave chemistry, the electrolyte solutions were heated almost entirely by the microwaves' H-field. The heating rates under H-field irradiation at the higher concentrations of electrolytes (0.125 M to 0.50 M) exceeded the rates under E-field irradiation. This inversion phenomenon in heating is described in terms of the penetration depth of the microwaves. On the other hand, the action of the microwave radiation on ethylene glycol containing an electrolyte differed from that observed for water under E-field and H-field conditions.

Strongly nonlinear dynamics of electrolytes in large ac voltages.

We study the response of a model microelectrochemical cell to a large ac voltage of frequency comparable to the inverse cell relaxation time. To bring out the basic physics, we consider the simplest possible model of a symmetric binary electrolyte confined between parallel-plate blocking electrodes, ignoring any transverse instability or fluid flow. We analyze the resulting one-dimensional problem by matched asymptotic expansions in the limit of thin double layers and extend previous work into the strongly nonlinear regime, which is characterized by two features--significant salt depletion in the electrolyte near the electrodes and, at very large voltage, the breakdown of the quasiequilibrium structure of the double layers. The former leads to the prediction of "ac capacitive desalination" since there is a time-averaged transfer of salt from the bulk to the double layers, via oscillating diffusion layers. The latter is associated with transient diffusion limitation, which drives the formation and collapse of space-charge layers, even in the absence of any net Faradaic current through the cell. We also predict that steric effects of finite ion sizes (going beyond dilute-solution theory) act to suppress the strongly nonlinear regime in the limit of concentrated electrolytes, ionic liquids, and molten salts. Beyond the model problem, our reduced equations for thin double layers, based on uniformly valid matched asymptotic expansions, provide a useful mathematical framework to describe additional nonlinear responses to large ac voltages, such as Faradaic reactions, electro-osmotic instabilities, and induced-charge electrokinetic phenomena.

Magnetoresponsive smart capsules formed with polyelectrolytes, lipid bilayers and magnetic nanoparticles.

Magnetoresponsive smart capsules formed with polyelectrolytes, lipid bilayers and magnetic nanoparticles were fabricated by a colloid-templating technique. Melamine-formaldehyde core particles with polyelectrolyte multilayer shell were prepared by layer-by-layer assembly. Magnetite (Fe(3)O(4)) nanoparticles were selectively deposited on the capsular surface by aqueous solution deposition using Pd catalysts. Hollow capsules were obtained by the removal of the melamine formaldehyde core particles. Vibrating sample magnetometer (VSM) measurement of the capsules revealed the ferromagnetic behavior of deposited Fe(3)O(4) nanoparticles. Alternating magnetic field irradiation generates heat in the capsular dispersion. Additional lipid bilayer coating was carried out on the obtained hollow capsules. Dye molecules were loaded by exploiting the temperature-dependence of the lipid membrane permeability. An encapsulated dye was released on-demand by irradiation with an alternating magnetic field, due to a phase transition in the lipid membrane, induced by heating of the magnetic nanoparticles. The magnetically induced release is attributed to the phase transition of the lipid membrane, caused by heat of Fe(3)O(4) nanoparticles under magnetic stimuli, and not to rupture of the capsules.

Peculiarities of the effect of terahertz radiation at nitric oxide frequencies on gaseous and electrolyte composition of the blood in different types of stress.

We studied the effect of terahertz radiation at NO frequencies 150.176-150.664 GHz on gaseous and electrolyte composition of the blood in albino rats during stress. Partial or complete recovery of the studied parameters of blood gases and electrolytes in stressed animals was observed after 15- and 30-min terahertz irradiation at NO frequencies, respectively.

Static and dynamic responses of polyelectrolyte brushes under external electric field.

The static and dynamic behaviors of partially charged and end-grafted polyelectrolyte brushes in response to electric fields were investigated by means of molecular dynamics simulation. The results show that the polymer brushes can be partially or fully stretched by applying an external electric field. Moreover, the brushes can switch reversibly from collapsed to stretched states, fully responding to the AC electric stimuli, and the gating response frequency can reach a few hundred MHz. The effects of the grafting density, the charge fraction of the brushes and the strength of the electric field on the average height of the polymer brushes were studied through the simulations.

Characterization of a new scaffold formed of polyelectrolyte complexes using atomic force and ultrasonic force microscopy.

Poly(acryloxyethyl-trimethylammonium chloride-co-2-hydroxyethyl methacrylate) [poly(Q-co-H)]/ sodium alginate gel (Ca2+) [AlgNa]/poly-l-lysine [PLL] films have been prepared on a mica surface. The structural arrangement and elasticity of the polyelectrolyte complexes have been studied with nanoscale resolution using Atomic Force Microscopy (AFM) and Ultrasonic Force Microscopy (UFM). The elastic contrast on the AlgNa surface is indicative of the formation of a biopolymer network. On the AlgNa film, the surface morphology is mostly characterized by areas with rounded beads (approximately =150 nm in diameter) and polymer strands. Flatter, more homogenous surface regions are also present, presumably related to outdiffused PLL. Incorporation of the poly(Q-co-H) layer results in an increased compactness of the film, and an enhancement of the previous AlgNa topographic features. The unique subsurface sensitivity provided by UFM allows us to resolve the elastic bonding distribution in the buried biopolymer network by imaging from the poly(Q-co-H) overlayer. Provided the biocompatibility of the resulting polyelectrolyte complex film, we propose this system as a novel scaffold for bioengineering applications. The results we present demonstrate the potential of UFM to get insight in the elastic behavior of encapsulated bionetworks.