Effect of radiant energy on near-surface water

Exclusion-zone water inside and outside of plant xylem vessels

The fourth phase of water has garnered increased attention within the scientific community due to its distinct properties that differentiate it from regular water. This unique state seems to arise potentially from a liquid crystalline structure, which has been observed near various hydrophilic surfaces to possess the capability of excluding microspheres. Consequently, it has been labeled as exclusion zone (EZ) water. When in contact with hydrophilic surfaces, water could exhibit the ability to form organized layers of EZ water. In this study, we investigated the quick buildup of EZ water exposed to xylem vessels of four vegetable plants: cabbage, celery, asparagus, and pumpkin. Among them, pumpkin vessels showed larger EZs, up to 240 ± 56 μm in width. The width of EZ water found near the xylem vessels of the other plants ranged from 133 ± 22 to 142 ± 20 μm. EZ water generally excludes a wide range of particles, including polystyrene microspheres with various surface modifications, as well as silica microspheres. This implies that the formation of EZ water is not an artificial result of using specific microsphere types but rather demonstrates EZ's ability to exclude particles regardless of their composition. Inside single xylem vessels of the pumpkin, we could observe the dynamics of EZ buildup, growing from the inside edge of the vessel toward the center. The relationship between vessel diameter, vessel length, and salt concentration on EZ generation inside the xylem vessel was also explored. The results showed that EZ water can build up both inside and outside the xylem vessels. Our findings suggest that EZ generation inside xylem vessels is associated with water flow, likely driven by a proton gradient. Further research is warranted to elucidate the role of EZ water in the physiology of living plants, particularly considering the limitations of the current experiments conducted on cut-out xylem vessel samples.

Dependence of cell's membrane potential on extracellular voltage observed in Chara globularis

The membrane potential (Vm) of a cell results from the selective movement of ions across the cell membrane. Recent studies have revealed the presence of a gradient of voltage within a few nanometers adjacent to erythrocytes. Very notably this voltage is modified in response to changes in cell's membrane potential thus effectively extending the potential beyond the membrane and into the solution. In this study, using the microelectrode technique, we provide experimental evidence for the existence of a gradient of negative extracellular voltage (Vz) in a wide zone close to the cell wall of algal cells, extending over several micrometers. Modulating the ionic concentration of the extracellular solution with CO2 alters the extracellular voltage and causes an immediate change in Vm. Elevated extracellular CO2 levels depolarize the cell and hyperpolarize the zone of extracellular voltage (ZEV) by the same magnitude. This observation strongly suggests a coupling effect between Vz and Vm. An increase in the level of intracellular CO2 (dark respiration) leads to hyperpolarization of the cell without any immediate effect on the extracellular voltage. Therefore, the metabolic activity of a cell can proceed without inducing changes in Vz. Conversely, Vz can be modified by external stimulation without metabolic input from the cell. The evolution of the ZEV, particularly around spines and wounded cells, where ion exchange is enhanced, suggests that the formation of the ZEV may be attributed to the exchange of ions across the cell wall and cell membrane. By comparing the changes in Vm in response to external stimuli, as measured by electrodes and observed using a potential-sensitive dye, we provide experimental evidence demonstrating the significance of extracellular voltage in determining the cell's membrane potential. This may have implications for our understanding of cell membrane potential generation beyond the activities of ion channels.

Sulfobetaine-Siloxanes: A Class of Self-Destructive Surfactants

The hydrolytic susceptibility of sulfobetaine-siloxane surfactants is investigated by comparison of a homologous series in this subclass of surfactants (R-(CH2)3N+(Me)2(CH2)3SO3-; R = (Me3SiO)3Si-, (Me3SiO)2Si(Me)-, (Me2SiO)3-Si(Me)-) with an analogue series of oxyethylene-siloxane surfactants (R-(CH2)3(OCH2CH2)10.2OH; R = (Me3SiO)3Si-, (Me3SiO)2Si(Me)-, (Me2SiO)3-Si(Me)-). Nuclear magnetic resonance (NMR) monitoring of these surfactants in an aqueous solution shows that the presence of the sulfobetaine head structure greatly enhances the hydrolysis rate of the siloxane tail as compared with oxyethylene-siloxane analogue control experiments. This sulfobetaine effect is confirmed by adding a model compound, (Me)3N+(CH2)3SO3-, to the oxyethylene-siloxane surfactants and observing the large hydrolysis enhancement. Measurements of pH indicate the sulfobetaine presence greatly enhances acidity, but rigorous analysis could discover no source of acid other than the presence of the sulfobetaine structure. Titration measurements confirmed the presence of a tightly bound hydration layer of 4-7 water molecules per sulfobetaine group. It is speculated that the source of acidity may originate from an aqueous exclusion zone nucleated by the hydrated sulfobetaine at the interface of a sulfobetaine-siloxane surfactant bilayer aggregate. Hydrolysis prevention is investigated by addition of a pH 7 phosphate buffer, of an alkyl polyglycoside cosurfactant, and of a combination of both, with a finding of very significant but not complete suppression of the hydrolysis.

Collective motion of Nafion-based micromotors in water

Ion exchange is one of the most interesting processes occurring at the interface between aqueous solutions and polymers, such as the well-known Nafion. If the exchanged ions have different diffusion coefficients, this interchange generates local electric fields which can be harnessed to drive fluid motion. In this work, we show how it is possible to design and fabricate self-propelling microswimmers based on Nafion, driven by ion-exchange, and fueled by innocuous salts. These Nafion micromotors are made using colloidal lithography by micro/nanostructuring Nafion in the form of asymmetric rods. These microswimmers exhibit fascinating collective motion in water driven by the interplay of their self-generated chemical/electric fields and their capability to pump matter nearby towards the collective motile structure. The pumping activity of the microswimmers induces the formation of growing mobile clusters, whose velocity increases with size. Such dynamic structures are able to trap nearby micro/nano-objects while purifying the liquid, which acts both as the transport media and as fuel. Such phenomenology opens the door to potential applications in water remediation that are currently under development.

On the driver of blood circulation beyond the heart

The heart is widely acknowledged as the unique driver of blood circulation. Recently, we discovered a flow-driving mechanism that can operate without imposed pressure, using infrared (IR) energy to propel flow. We considered the possibility that, by exploiting this mechanism, blood vessels, themselves, could propel flow. We verified the existence of this driving mechanism by using a three-day-old chick-embryo model. When the heart was stopped, blood continued to flow for approximately 50 minutes, albeit at a lower velocity. When IR was introduced, the postmortem flow increased from ~41.1 ± 25.6 μm/s to ~153.0 ± 59.5 μm/s (n = 6). When IR energy was diminished under otherwise physiological conditions, blood failed to flow. Hence, this IR-dependent, vessel-based flow-driving mechanism may indeed operate in the circulatory system, complementing the action of the heart.

Voltage and concentration gradients across membraneless interface generated next to hydrogels: relation to glycocalyx

Next to many hydrophilic surfaces, including those of biological cells and tissues, a layer of water that effectively excludes solutes and particles can be generated. This interfacial water is the subject of research aiming for practical applications such as removal of salts, pathogens or manipulation of biomolecules. However, the exact mechanism of its creation is still elusive because its persistence and extension contradict hydrogen-bond dynamics and electric double layer predictions. The experimentally recorded negative voltage of this interfacial water remains to be properly explained. Even less is known about the nature of such water layers in biological systems. We present experimental evidence for ion and particle exclusion as a result of separation of ionic charges with distinct diffusion rates across a liquid junction at the gel/water interface and the subsequent repulsion of ions of a given sign by a like-charged gel surface. Gels represent features of biological interfaces (in terms of functional groups and porosity) and are subject to biologically relevant chemical triggers. Our results show that gels with -OSO3- and -COO- groups can effectively generate ion- and particle-depleted regions of water reaching over 100 μm and having negative voltage up to -30 mV. Exclusion distance and electric potential depend on the liquid junction potential at the gel/water interface and on the concentration gradient at the depleted region/bulk interface, respectively. The voltage and extension of these ion- and particle-depleted water layers can be effectively modified by CO2 (respiratory gas) or KH2PO4 (cell metabolite). Possible implications pertain to biologically unstirred water layers and a cell's bioenergetics.

Self-generated exclusion zone in a dead-end pore microfluidic channel

Particles can be manipulated by gradients of concentration (diffusiophoresis) and electric potential (electrophoresis) to transport them to desired locations. To establish these gradients, external stimuli are usually required. In this work, we manipulate particles through a self-generated concentration gradient within a PDMS-based microfluidic platform, without directly applying an external field. The interfacial chemistry of the PDMS results in a local increase of hydronium ions, leading to a concentration and electrical potential gradient in the system, which in turn generate a temporary exclusion zone at the pore entrance, extending up to half of the main channel, or 150 μm. With time, this exclusion zone diminishes as equilibrium in the ion concentration is reached. We study the dynamics of the exclusion zone thickness and find that the Sherwood number determines the size and stability of the exclusion zone. Our work shows, that even without introducing external ionic gradients, particle diffusiophoresis is significant in lab-on-a-chip systems. The interfacial chemistry of the microfluidic platform can have a significant influence on particle movement and this should be considered when designing experiments on diffusiophoresis. The observed phenomenon can be employed to design lab-on-a-chip-based sorting of colloidal particles.

Adsorption of Methylene Blue on the Surface of Polymer Membrane; Dependence on the Isotopic Composition of Liquid Matrix

As was found in our previous works, when Nafion swells in water, polymer fibers unwind into the bulk of the surrounding liquid. This effect is controlled by the content of deuterium in water. Here, we present the results of studying the dynamics of methylene blue (MB) adsorption on the Nafion surface for MB solutions based on natural water (deuterium content is 157 ppm, the unwinding effect occurs) and based on deuterium-depleted water (DDW; deuterium content is 3 ppm, there is no unwinding). In addition, we studied the dynamics of water desorption during drying of the Nafion polymer membrane after soaking in MB solution based on natural water and DDW. It turned out that in the case of natural water, the rate of MB adsorption and water desorption is higher than in the case of DDW. It also turned out that the amount of MB adsorbed on the membrane in the case of natural water is greater than in the case of DDW. Finally, it was found that the desorption of water during drying is accompanied by a rearrangement of the absorption spectrum of Nafion. This rearrangement occurs earlier in the case of DDW. Thus, by infinitesimal changes in the deuterium content (from 3 to 157 ppm) in an aqueous solution, in which a polymer membrane swells, we can control the dynamics of adsorption and desorption processes. A qualitative model, which connects the observed effects with the slowing down of diffusion processes inside the layer of unwound fibers, is proposed.

A phenomenological model for interfacial water near hydrophilic polymers

We propose a minimalist phenomenological model for the 'interfacial water' phenomenon that occurs near hydrophilic polymeric surfaces. We achieve this by combining a Ginzburg-Landau approach with Maxwell's equations which leads us to a well-posed model providing a macroscopic interpretation of experimental observations. From the derived governing equations, we estimate the unknown parameters using experimental measurements from the literature. The resulting profiles of the polarization and electric potential show exponential decay near the surface, in qualitative agreement with experiments. Furthermore, the model's quantitative prediction of the electric potential at the hydrophilic surface is in excellent agreement with experiments. The proposed model is a first step towards a more complete parsimonious macroscopic model that will, for example, help to elucidate the effects of interfacial water on cells (e.g. neuronal excitability), the effects of infrared neural stimulation or the effects of drugs mediated by interfacial water.

Magnetic fields induce exclusion zones in water

Hydrophilic materials immersed in aqueous solutions show near-surface zones that exclude suspended colloids and dissolved molecules. These exclusion zones (EZs) can extend for tens to hundreds of micrometers from hydrophilic surfaces and show physicochemical properties that differ from bulk water. Here we report that exposure of standard aqueous microsphere suspensions to static magnetic fields creates similar microsphere-free zones adjacent to magnetic poles. The EZs build next to both north and south poles; and they build whether the microspheres are of polystyrene or carboxylate composition. EZ formation is accompanied by ordered motions of microspheres, creating dense zones some distance from the magnetic poles and leaving microsphere-free zones adjacent to the magnet. EZ size was larger next to the north pole than the south pole. The difference was statistically significant when polystyrene microspheres were used, although not when carboxylate microspheres were used. In many ways, including both size and dynamics, these exclusion zones resemble those found earlier next to various hydrophilic surfaces. The ability to create EZs represents a feature of magnets not previously revealed.

Restoration of the Indicator Properties of Whole-cell Luminescent Biosensors

Whole-cell biosensors are widely used to produce medical diagnostic tests, but in the long term, they tend to lose their indicator properties. Consequently, it is crucial to find ways to restore these properties and prolong the shelf life of the tests. Here, we propose to use electromagnetic radiation with optimally selected parameters of frequency, power, and exposure time. The impact of radiation parameters on biosensor luminescence was studied as well as the effects of different types of radiation coming from laser sources (λ = 875 nm), a LED source (λ = 850 ÷ 890 nm), and microwave units (at frequencies 42.22, 53.53, 61.18 и 34 ÷ 38 GHz). IR treatment resulted in dose-dependent suppression of biosensor luminescence. The luminescence level when exposed to microwave radiation depends on the radiation time and frequency. Also, it has been found that optimal selection of the main radiation parameters enables to restore indicator properties partially lost by biosensors during storage. We explain the mechanism responsible for the sensitizing effect of radiation, which implies the polarization of solvent dipoles and changes in mobility of acceptor molecules. This, in turn, leads to a shift in the chemical equilibrium states and triggers a cascade of biochemical reactions that lead to restoration of the lost indicator properties of biosensors. The study of antagonistic activity has revealed that restored biosensors provide reliable test results after the expiration of their warranty period.

Near-Infrared Photobiomodulation of Living Cells, Tubulin, and Microtubules In Vitro

We report the results of experimental investigations involving photobiomodulation (PBM) of living cells, tubulin, and microtubules in buffer solutions exposed to near-infrared (NIR) light emitted from an 810 nm LED with a power density of 25 mW/cm² pulsed at a frequency of 10 Hz. In the first group of experiments, we measured changes in the alternating current (AC) ionic conductivity in the 50–100 kHz range of HeLa and U251 cancer cell lines as living cells exposed to PBM for 60 min, and an increased resistance compared to the control cells was observed. In the second group of experiments, we investigated the stability and polymerization of microtubules under exposure to PBM. The protein buffer solution used was a mixture of Britton-Robinson buffer (BRB aka PEM) and microtubule cushion buffer. Exposure of Taxol-stabilized microtubules (~2 μM tubulin) to the LED for 120 min resulted in gradual disassembly of microtubules observed in fluorescence microscopy images. These results were compared to controls where microtubules remained stable. In the third group of experiments, we performed turbidity measurements throughout the tubulin polymerization process to quantify the rate and amount of polymerization for PBM-exposed tubulin vs. unexposed tubulin samples, using tubulin resuspended to final concentrations of ~ 22.7 μM and ~ 45.5 μM in the same buffer solution as before. Compared to the unexposed control samples, absorbance measurement results demonstrated a slower rate and reduced overall amount of polymerization in the less concentrated tubulin samples exposed to PBM for 30 min with the parameters mentioned above. Paradoxically, the opposite effect was observed in the 45.5 μM tubulin samples, demonstrating a remarkable increase in the polymerization rates and total polymer mass achieved after exposure to PBM. These results on the effects of PBM on living cells, tubulin, and microtubules are novel, further validating the modulating effects of PBM and contributing to designing more effective PBM parameters. Finally, potential consequences for the use of PBM in the context of neurodegenerative diseases are discussed.

Computational Investigation of the Ordered Water System Around Microtubules: Implications for Protein Interactions

The existence of an exclusion zone in which particles of a colloidal suspension in water are repelled from hydrophilic surfaces has been experimentally demonstrated in numerous studies, especially in the case of Nafion surfaces. Various explanations have been proposed for the origin of this phenomenon, which is not completely understood yet. In particular, the existence of a fourth phase of water has been proposed by G. Pollack and if this theory is proven correct, its implications on our understanding of the properties of water, especially in biological systems, would be profound and could give rise to new medical therapies. Here, a simple approach based on the linearized Poisson-Boltzmann equation is developed in order to study the repulsive forces mediated by ordered water and involving the following interacting biomolecules: 1) microtubule and a tubulin dimer, 2) two tubulin dimers and 3) a tubulin sheet and a tubulin dimer. The choice of microtubules in this study is motivated because they could be a good candidate for the generation of an exclusion zone in the cell and these models could be a starting point for detailed experimental investigations of this phenomenon.

Far-infrared-emitting fabric improves neuromuscular performance of knee extensor

The aim of this study was to verify if exposure to the far-IR emitted by fabric (FIR) is able to improve the neuromuscular performance of the knee extensors of resistance-trained males regardless of changes of the temperature. It is a crossover, randomized, double-blind, and placebo-controlled trial. Fourteen resistance-trained males (age: 24.3 ± 4 years; body mass: 82.8 ± 11.3 kg; height: 176.3 ± 4.2 cm) were randomly assigned to one of initial conditions: FIR (n = 7) or placebo (n = 7). After 4 days, the participants were submitted to neuromuscular tests in an isokinetic dynamometer (maximal isometric voluntary contraction (MVC) and fatigue test). After a week of washout, participants performed the other condition. We measured peak torque (Nm), total work (J), fatigue index (%), root mean square (mV), median frequency (Hz), and temperature (°C) of thigh. The FIR was worn for 82 ± 19 h before the experimental session, totaling 317 ± 74 kJ of energy irradiation. There was a significant increase (p < 0.05) for pre-MVC (318.5 ± 68.7 Nm) and post-MVC (284.1 ± 58.2 Nm), and a trend (p = 0.055) for significant increase for total work (4,122.2 ± 699.8 J) on FIR condition regardless of none change on temperature and electromyographic (EMG) signals. FIR improved the neuromuscular performance of knee extensors in resistance-trained males regardless of changes on temperature and EMG. The present results suggest that the FIR could optimize the neuromuscular performance with 82 ± 19 h of wear.

Effect of Humid Air Exposed to IR Radiation on Enzyme Activity

Water vapor absorbs well in the infra-red region of the electromagnetic spectrum. Absorption of radiant energy by water or water droplets leads to formation of exclusion zone water that possesses peculiar physico-chemical properties. In the course of this study, normally functioning and damaged alkaline phosphatase, horseradish peroxidase and catalase were treated with humid air irradiated with infrared light with a wavelength in the range of 1270 nm and referred to as coherent humidity (CoHu). One-minute long treatment with CoHu helped to partially protect enzymes from heat inactivation, mixed function oxidation, and loss of activity due to partial unfolding. Authors suggest that a possible mechanism underlying the observed effects involves altering the physicochemical properties of aqueous media while treatment of the objects with CoHu where CoHu acts as an intermediary.

Low frequency weak electric fields can induce structural changes in water

Low frequency electric fields were exposed to various water samples using platinum electrodes mounted near the water surface. Responses were monitored using a spectro-radiometer and a contact-angle goniometer. Treatment of DI (deionized), EZ (Exclusion Zone), and bulk water with certain electromagnetic frequencies resulted in a drop of radiance persisting for at least half an hour. Compared to DI water, however, samples of EZ and bulk water showed lesser radiance drop. Contact-angle goniometric results confirmed that when treated with alternating electric fields (E = 600 ± 150 V/m, f = 7.8 and 1000 Hz), droplets of EZ and bulk water acquired different charges. The applied electric field interacted with EZ water only when electrodes were installed above the chamber, but not beneath. Further, when DI water interacted with an electric field applied from above (E = 600 ± 150 V/m, f = 75 Hz), its radiance profile became similar to that of EZ water. Putting these last two findings together, one can say that application of an electric field on DI water from above (E = 600 ± 150 V/m, f = 7.8 to 75 Hz) may induce a molecular ordering in DI water similar to that of EZ water.

Immune Response to Silk Sericin-Fibroin Composites: Potential Immunogenic Elements and Alternatives for Immunomodulation

The unique properties of silk proteins (SPs), particularly silk sericin (SS) and silk fibroin (SF), have attracted attention in the design of scaffolds for tissue engineering over the past decades. Since SF has good mechanical properties, while SS displays bioactivity, scaffolds combining both proteins should exhibit complementary properties enhancing the potential of these materials. Unfortunately, SS-SF composites can generate chronic immune responses and their immunogenic element is not completely clear. The potential of SS-SF composites in tissue engineering, elements which may contribute to their immunogenicity, and alternatives for their preparation and design, to modulate the immune response and take advantage of their useful properties, are discussed in this review. It is known that SS can enhance β-sheet formation in SF, which may act as hydrophobic regions with a strong affinity for adsorption proteins inducing the chronic recruitment of inflammatory cells. Therefore, tailoring the exposure of hydrophobic regions at the scaffold surface should represent a viable strategy to modulate the immune response. This can be achieved by coating SS-SF composites with SS or other hydrophilic polymers, to take advantage of their antibiofouling properties. Research is still needed to realize the full potential of these composites for tissue engineering.

Dynamics of Polymer Membrane Swelling in Aqueous Suspension of Amino-Acids with Different Isotopic Composition; Photoluminescence Spectroscopy Experiments

In photoluminescence spectroscopy experiments, the interaction mode of the polymer membrane Nafion with various amino-acids was studied. The experiments were performed with physiological NaCl solutions prepared in an ordinary water (the deuterium content is 157 ± 1 ppm) and also in deuterium-depleted water (the deuterium content is ≤1 ppm). These studies were motivated by the fact that when Nafion swells in ordinary water, the polymer fibers are effectively “unwound” into the liquid bulk, while in the case of deuterium-depleted water, the unwinding effect is missing. In addition, polymer fibers, unwound into the liquid bulk, are similar to the extracellular matrix (glycocalyx) on the cell membrane surface. It is of interest to clarify the role of unwound fibers in the interaction of amino-acids with the polymer membrane surface. It turned out that the interaction of amino-acids with the membrane surface gives rise to the effects of quenching luminescence from the luminescence centers. We first observed various dynamic regimes arising upon swelling the Nafion membrane in amino-acid suspension with various isotopic content, including triggering effects, which is similar to the processes in the logical gates of computers.

Propolis-induced exclusion of colloids: Possible new mechanism of biological action

Propolis is a natural product originating from life activity of honeybees. It exhibits wide range of biological properties applicable in medicine, the food industry, and cosmetics. Chemically, propolis is a complex and variable mixture with more than 300 identified biologically active components. Propolis's many health-promoting effects are attributed to different biochemical mechanisms, mediated by often-concerted actions of some of its many constituents. Propolis is considered safe and biocompatible. Yet due to its intrinsic complexity, standardization of propolis preparations for medical use as well as prediction of e.g. pathogen-specific interactions becomes a non-trivial task. In this work we demonstrate a new physical mechanism of propolis action, largely independent of specific nuances of propolis chemistry, which may underlie some of its biological actions. We show that propolis-bearing surfaces generate an extensive exclusion zone (EZ) water layer. EZ is an interfacial region of water capable of excluding solutes ranging from ions to microorganisms. Propolis-generated EZ may constitute an effective barrier, physically disabling the approach of various pathogens to the propolis-functionalized surfaces. We suggest possible implications of this new mechanism for propolis-based prevention of respiratory infections.

Exclusion Zone Phenomena in Water-A Critical Review of Experimental Findings and Theories

The existence of the exclusion zone (EZ), a layer of water in which plastic microspheres are repelled from hydrophilic surfaces, has now been independently demonstrated by several groups. A better understanding of the mechanisms which generate EZs would help with understanding the possible importance of EZs in biology and in engineering applications such as filtration and microfluidics. Here we review the experimental evidence for EZ phenomena in water and the major theories that have been proposed. We review experimental results from birefringence, neutron radiography, nuclear magnetic resonance, and other studies. Pollack theorizes that water in the EZ exists has a different structure than bulk water, and that this accounts for the EZ. We present several alternative explanations for EZs and argue that Schurr's theory based on diffusiophoresis presents a compelling alternative explanation for the core EZ phenomenon. Among other things, Schurr's theory makes predictions about the growth of the EZ with time which have been confirmed by Florea et al. and others. We also touch on several possible confounding factors that make experimentation on EZs difficult, such as charged surface groups, dissolved solutes, and adsorbed nanobubbles.

Surface-induced flow: A natural microscopic engine using infrared energy as fuel

Fluid commonly flows in response to an external pressure gradient. However, when a tunnel-containing hydrogel is immersed in water, spontaneous flow occurs through the tunnel without any pressure gradient. We confirmed this flow in a wide range of plant- and animal-derived hydrogels. The flow appears to be driven by axial concentration gradients originating from surface activities of the tunnel wall. Those activities include (i) hydrogel-water interaction and (ii) material exchange across the tunnel boundary. Unlike pressure-driven flow, this surface-induced flow has two distinct features: incident infrared energy substantially increases flow velocity, and narrower tunnels generate faster flow. Thus, surface activities in hydrogel-lined tunnels may confer kinetic energy on the enclosed fluid, with infrared as an energy source.

Electrophoretic origin of long-range repulsion of colloids near water/Nafion interfaces

One of the most striking properties of Nafion is the formation of a long-range solute exclusion zone (EZ) in contact with water. The mechanism of formation of this EZ has been the subject of a controversial and long-standing debate. Previous studies by Schurr et al. and Florea et al. root the explanation of this phenomenon in the ion-exchange properties of Nafion, which generates ion diffusion and ion gradients that drive the repulsion of solutes by diffusiophoresis. Here we have evaluated separately the electrophoretic and chemiphoretic contributions to multi-ionic diffusiophoresis using differently charged colloidal tracers as solutes to identify better their contribution in the EZ formation. Our experimental results, which are also supported by numerical simulations, show that the electric field, built up due to the unequal diffusion coefficients of the exchanged ions, is the dominant parameter behind such interfacial phenomenon in the presence of alkali metal chlorides. The EZ formation depends on the interplay of the electric field with the zeta potential of the solute and can be additionally modulated by changing ion diffusion coefficients or adding salts. As a consequence, we show that not all solutes can be expelled from the Nafion interface and hence the EZ is not always formed. This study thus provides a more detailed description of the origin and dynamics of this phenomenon and opens the door to the rational use of this active interface for many potential applications.

The effect of red-to-near-infrared (R/NIR) irradiation on inflammatory processes

Introduction: Near-infrared (NIR) and red-to-near-infrared (R/NIR) radiation are increasingly applied for therapeutic use. R/NIR-employing therapies aim to stimulate healing, prevent tissue necrosis, increase mitochondrial function, and improve blood flow and tissue oxygenation. The wide range of applications of this radiation raises questions concerning the effects of R/NIR on the immune system. Methods: In this review, we discuss the potential effects of exposure to R/NIR light on immune cells in the context of physical parameters of light. Discussion: The effects that R/NIR may induce in immune cells typically involve the production of reactive oxygen species (ROS), nitrogen oxide (NO), or interleukins. Production of ROS after exposure to R/NIR can either be inhibited or to some extent increased, which suggests that detailed conditions of experiments, such as the spectrum of radiation, irradiance, exposure time, determine the outcome of the treatment. However, a wide range of immune cell studies have demonstrated that exposure to R/NIR most often has an anti-inflammatory effect. Finally, photobiomodulation molecular mechanism with particular attention to the role of interfacial water structure changes for cell physiology and regulation of the inflammatory process was described. Conclusions: Optimization of light parameters allows R/NIR to act as an anti-inflammatory agent in a wide range of medical applications.

Interfacial water and its potential role in the function of sericin against biofouling

Silk sericin is a globular protein whose resistance against fouling is important for applications in biomaterials and water-purification membranes. Here it is shown how sericin generates a water-exclusion zone that may facilitate antifouling behavior. Negatively charged microspheres were used to mimic the surface charge and hydrophobic domains in bacteria. Immersed in water, regenerated silk sericin formed a 100-µm-sized exclusion zone (for micron-size foulants), along with a proton gradient with a decrease of >2 pH-units. Thus, when in contact with sericin, water molecules near the surface restructure to form a physical exclusionary barrier that might prevent biofouling. The decreased pH turns the aqueous medium unviable for neutrophilic bacteria. Therefore, resistance to biofouling seems explainable, among other factors, on the basis of water-exclusionary phenomena. Furthermore, sericin may play a role in triggering the fibroin assembly process by lowering the pH to the required value.

Large-scale structure formation in ionic solution and its role in electrolysis and conductivity

That water may not be an inert medium was indicated by the presence at water’s interfaces a negatively charged solute free zone of several hundred microns in thickness called the exclusion zone (EZ). Further evidence was demonstrated by Ovchinnikova’s experiments (2009) showing that water can store and release substantial amount of charge. We demonstrate that the charge storage capacity of water arises from highly stable large-scale ionic structures with measurable charge imbalances and discrete levels of charge density. We also show evidence that the charge zones formation requires ionic solutes, and their formation correlate to large change in conductivity, by as much as 250%. Our experiments indicate that large-scale structuring plays a pivotal role in electrolysis and conductivity in ionic solution. We propose that water is an electrochemically active medium and present a new model of electrolysis and conductivity in ionic solution.

Spontaneous Selective Preconcentration Leveraged by Ion Exchange and Imbibition through Nanoporous Medium

Manipulating mechanism of particle’s motion has been extensively studied for the sample preparation in microfluidic applications including diagnostics, food industries, biological analyses and environmental monitoring. However, most of conventional methods need additional external forces such as electric field or pressure and complicated channel designs, which demand highly complex fabrication processes and operation strategies. In addition, these methods have inherent limitations of dilution or mixing during separation or preconcentration step, respectively, so that a number of studies have reported an efficient selective preconcentration process, i.e. conducting the separation and preconcentration simultaneously. In this work, a power-free spontaneous selective preconcentration method was suggested based on leveraging convective flow over diffusiophoresis near the water-absorbing nanoporous ion exchange medium, which was verified both by simulation and experiment. Especially, the velocity of the convective flow by an imbibition deviated from the original tendency of t^−1/2 due to non-uniformly patterned nanoporous medium that has multiple cross-sectional areas. As a result, the direction of particle’s motion was controlled at one’s discretion, which led to the spontaneous selective preconcentration of particles having different diffusiophoretic constant. Also, design rule for maximizing the efficiency was recommended. Thus, this selective preconcentration method would play as a key mechanism for power-free lab on a chip applications.

Non-mammalian Hosts and Photobiomodulation: Do All Life-forms Respond to Light?

Photobiomodulation (PBM), also known as low-level laser (light) therapy, was discovered over 50 years ago, but only recently has it been making progress toward wide acceptance. PBM originally used red and near-infrared (NIR) lasers, but now other wavelengths and non-coherent light-emitting diodes (LEDs) are being explored. The almost complete lack of side effects makes the conduction of controlled clinical trials relatively easy. Laboratory research has mainly concentrated on mammalian cells (normal or cancer) in culture, and small rodents (mice and rats) as models of different diseases. A sizeable body of work was carried out in the 1970s and 1980s in Russia looking at various bacterial and fungal cells. The present review covers some of these studies and a recent number of papers that have applied PBM to so-called "model organisms." These models include flies (Drosophila), worms (Caenorhabditis elegans), fish (zebrafish) and caterpillars (Galleria). Much knowledge about the genomics and proteomics, and many reagents for these organisms already exist. They are inexpensive to work with and have lower regulatory barriers compared to vertebrate animals. Other researchers have studied different models (snails, sea urchins, Paramecium, toads, frogs and chickens). Plants may respond to NIR light differently from visible light (photosynthesis and photomorphogenesis) but PBM in plants has not been much studied. Veterinarians routinely use PBM to treat non-mammalian patients. The conclusion is that red or NIR light does indeed have significant biologic effects conserved over many different kingdoms, and perhaps it is true that "all life-forms respond to light."

Effect of red light and near infrared laser on the generation of reactive oxygen species in primary dermal fibroblasts

Irradiation with red light or near-infrared (NIR) lasers can bio-modulate cellular processes or revitalize injured tissues and therefore, widely been used for therapeutic interventions. Mechanistically, this cellular or biological process, referred as Photobiomodulation (PBM), is achieved by the generation of oxide free radicals in cells and tissues. This explorative study using red light (636 nm) and Near Infra-Red (NIR, 825 nm) laser at various irradiation exposures reckons the level of oxidative stress induced by these free radicals in human primary fibroblasts. Freshly isolated dermal fibroblasts were irradiated with red light and NIR at power densities of 74 and 104 mV/cm², respectively and, at varying fluences ranging from 5 to 25 J/cm². Cellular oxidative stress, measured by Reactive Oxygen Species (ROS) upon quantifying fluorescently labelled oxide free radicals in cells, detected considerable variations between the irradiation exposures of red light and NIR laser. The NIR laser demonstrated high levels of ROS at all fluences, except 10 J/cm² indicating its ability in generating of two types of oxide radicals in dermal fibroblasts, often illustrated as biphasic response. Further, the responses of these cells to variable fluences of red light and NIR laser were measured to evaluate the immediate effect of PBM on cellular activity. The production of cellular energy coincides with the amount of oxidative stress, which was two-fold higher in cells irradiated with the NIR laser, as compared with the red light. This outcome indicates that the ROS production within biological systems are more dependent on the wavelength of the laser rather than its fluences. Further studies are required to avoid 'overdosing of PBM' and to analyse ROS qualitatively for making the best use of the red light and NIR laser in clinics.

Non-negligible Water-permeance through Nanoporous Ion Exchange Medium

While the water impermeable constraint has been conventionally adopted for analyzing the transport phenomena at the interface of electrolyte/nanoporous medium, non-negligible water-permeance through the medium results in significant effect on ion and particle transportation. In this work, a rigorous theoretical and experimental analysis of the water-permeance effect were conducted based on a fully-coupled analytical/numerical method and micro/nanofluidic experiments. The regime diagram with three distinctive types of concentration boundary layers (ion depletion, ion accumulation, and intermediate) near the ion exchange nanoporous medium was proposed depending on the medium's permselectivity and the water-permeance represented by an absorbing parameter. Moreover, the critical absorbing parameters which divide the regimes were analytically obtained so that the bidirectional motion of particles were demonstrated only by altering the water-permeance without external stimuli. Conclusively, the presenting analysis of non-negligible water-permeance would be a substantial fundamental of transport phenomena at the interface of the ion exchange medium and electrolyte, especially useful for the tunable particle/ion manipulations in intermediate Peclet number environment.

Exclusion zone and heterogeneous water structure at ambient temperature

Earlier studies have reported the formation of an exclusion zone devoid of microspheres at the interface of water with a hydrophilic surface such as Nafion® or the hydrophilic ceramic powder. We now report the formation of a 'three-dimensional cell-like structured exclusion zone' in water prepared by two different methods. In the first, the hydrophilic powder was agitated with deionized water and allowed to rest (contact method). Subsequently, the 'powder-supernatant water' was collected and termed 'contact water'. In the second method, deionized water in a closed container was kept in the close vicinity of the hydrophilic powder for an extended time-period and it was termed 'non-contact water'. The two kinds of waters were tested by standard methods for various physical properties. In addition, we carried out cryogenic scanning-electron microscopy of frozen samples of the two kinds of water. The powder-supernatant water showed a cell-like heterogeneous ice structure with the high-density exclusion-zone water forming the walls of a cell-like structure. A similar cell-like ice structure was formed for water treated with the hydrophilic powder in a non-contact manner; the unit cell size depended on the 'degree of structure' in the water. When highly structured, the unit cell size was smaller with a concurrently enhanced dielectric constant and reduced redox potential. It was found that the electrical properties are more sensitive to the change in water structure compared to other physical properties such as surface tension, density, and specific heat. Based on our findings of an electric potential difference between the heterogeneous structured water and the ordinary water, we propose a new model to explain the relationship between heterogeneous, structured water and its electrical properties.

Why Hydrogels Don't Dribble Water

Hydrogels contain ample amounts of water, with the water-to-solid ratio sometimes reaching tens of thousands of times. How can so much water remain securely lodged within the gel? New findings imply a simple mechanism. Next to hydrophilic surfaces, water transitions into an extensive gel-like phase in which molecules become ordered. This “fourth phase” of water sticks securely to the solid gel matrix, ensuring that the water does not leak out.

Effect of Antioxidant Water on the Bioactivities of Cells

It has been reported that water at the interface of a hydrophilic thin film forms an exclusion zone, which has a higher density than ordinary water. A similar phenomenon was observed for a hydrated hydrophilic ceramic powder, and water turns into a three-dimensional cell-like structure composed of high density water and low density water. This structured water appears to have a stimulative effect on plant growth. This report outlines our study of antioxidant properties of this structured water and its effect on cell bioactivities. Culturing media which were prepared utilizing this antioxidant structured water promoted the viability of RAW 264.7 macrophage cells by up to three times. The same tendency was observed for other cells including IEC-6, C2C12, and 3T3-L1. Also, the cytokine expression of the splenocytes taken from a mouse spleen increased in the same manner. The water also appears to suppress the viability of cancer cell, MCF-7. These results strongly suggest that the structured water helps the activities of normal cells while suppressing those of malignant cells.

Mechanisms and applications of the anti-inflammatory effects of photobiomodulation

Photobiomodulation (PBM) also known as low-level level laser therapy is the use of red and near-infrared light to stimulate healing, relieve pain, and reduce inflammation. The primary chromophores have been identified as cytochrome c oxidase in mitochondria, and calcium ion channels (possibly mediated by light absorption by opsins). Secondary effects of photon absorption include increases in ATP, a brief burst of reactive oxygen species, an increase in nitric oxide, and modulation of calcium levels. Tertiary effects include activation of a wide range of transcription factors leading to improved cell survival, increased proliferation and migration, and new protein synthesis. There is a pronounced biphasic dose response whereby low levels of light have stimulating effects, while high levels of light have inhibitory effects. It has been found that PBM can produce ROS in normal cells, but when used in oxidatively stressed cells or in animal models of disease, ROS levels are lowered. PBM is able to up-regulate anti-oxidant defenses and reduce oxidative stress. It was shown that PBM can activate NF-kB in normal quiescent cells, however in activated inflammatory cells, inflammatory markers were decreased. One of the most reproducible effects of PBM is an overall reduction in inflammation, which is particularly important for disorders of the joints, traumatic injuries, lung disorders, and in the brain. PBM has been shown to reduce markers of M1 phenotype in activated macrophages. Many reports have shown reductions in reactive nitrogen species and prostaglandins in various animal models. PBM can reduce inflammation in the brain, abdominal fat, wounds, lungs, spinal cord.

Photobiomodulation of human adipose-derived stem cells using 810nm and 980nm lasers operates via different mechanisms of action

Photobiomodulation (PBM) using red or near-infrared (NIR) light has been used to stimulate the proliferation and differentiation of adipose-derived stem cells. The use of NIR wavelengths such as 810nm is reasonably well accepted to stimulate mitochondrial activity and ATP production via absorption of photons by cytochrome c oxidase. However, the mechanism of action of 980nm is less well understood. Here we study the effects of both wavelengths (810nm and 980nm) on adipose-derived stem cells in vitro. Both wavelengths showed a biphasic dose response, but 810nm had a peak dose response at 3J/cm² for stimulation of proliferation at 24h, while the peak dose for 980nm was 10-100 times lower at 0.03 or 0.3J/cm². Moreover, 980nm (but not 810nm) increased cytosolic calcium while decreasing mitochondrial calcium. The effects of 980nm could be blocked by calcium channel blockers (capsazepine for TRPV1 and SKF96365 for TRPC channels), which had no effect on 810nm. To test the hypothesis that the chromophore for 980nm was intracellular water, which could possibly form a microscopic temperature gradient upon laser irradiation, we added cold medium (4°C) during the light exposure, or pre-incubated the cells at 42°C, both of which abrogated the effect of 980nm but not 810nm. We conclude that 980nm affects temperature-gated calcium ion channels, while 810nm largely affects mitochondrial cytochrome c oxidase.

Long range physical cell-to-cell signalling via mitochondria inside membrane nanotubes: a hypothesis

Coordinated interaction of single cells by cell-to-cell communication (signalling) enables complex behaviour necessary for the functioning of multicellular organisms. A quite newly discovered cell-to-cell signalling mechanism relies on nanotubular cell-co-cell connections, termed "membrane nanotubes" (MNTs). The present paper presents the hypothesis that mitochondria inside MNTs can form a connected structure (mitochondrial network) which enables the exchange of energy and signals between cells. It is proposed that two modes of energy and signal transmission may occur: electrical/electrochemical and electromagnetic (optical). Experimental work supporting the hypothesis is reviewed, and suggestions for future research regarding the discussed topic are given.

Thermal properties of frozen water in the native and amorphous starches with various hydration degrees

The melting process of frozen water (FW) in various starches (rice, wheat, potato) that have crystal lattices of A- and B-type has been studied by means of differential scanning calorimetry (DSC). The dependences of the melting temperature (Tm) and heat (Qm) of FW on the size of the water clusters forming in starches with various humidity (the so-called size effect) and on conformational changes of starch molecules upon the destruction of native starch crystals (starch amorphization) have been considered. It has been found that in the native starches with low humidity (<35%) the Tm of FW lies below 0 °C and decreases with the decrease of their humidity. The sizes of the water clusters formed under these conditions have been estimated. In contrast, such a size effect in amorphous starches has not been observed and possible reasons for its masking have been discussed. Still, all the values of Tm for FW obtained in the amorphous starches are also negative thereby indicating the dispersed state of water in these systems. Conversely, the size effect for Qm of FW in starches with low humidity, very pronounced in the amorphous state and barely visible in the native one, has been found. It has been established that the starch amorphization leads to a redistribution of the relative amounts of FW and unfrozen water (UFW) resulting in the decrease of Qm for FW in both A- and B- starch types. Finally, it has been concluded that in all the investigated starches there exist water clusters with Tm and Qm lower than that of bulk water.