Interfacial water states and the biocompatibility of biomaterials: The role of intermediate water

The excellent biocompatibility of PMEA was ascribed by Tanaka to the predominant population of intermediate water in the hydrated polymer matrix. The intermediate water concept was examined using the 'nano-plate model' on the basis of new results (by Morita) of a time-resolved IR study on the water sorption process into PMEA. The examination showed that the image picture proposed by Tanaka concerning the role of intermediate water was in consistent with experimental results so far obtained. Morita showed that the intermediate water exhibited a strong peak at 3400 cm−1 in its IR spectrum. Water sorption profiles of MMA, PEG and PMVE were found to be similar to that of PMEA. It was shown that the biocompatibility of these polymers could be explained by the intermediate water concept. It was also pointed out that PVP and PDMAA have a considerable amount of intermediate water under appropriate circumstances. The PHEMA–water system showed neither clear peak for cold crystallization in DSC chart, nor the strong peak at 3400 cm−1 in its IR spectrum, because the PHEMA system did not contain enough intermediate water to show similar behavior to PMEA. The hydrated PHEMA matrix contains a stable network structure of water molecules including the nodes of OH groups of its side-chains. In the stable network system, most water molecules should be hydrogen bonded strongly to form non-freezing water, but not intermediate water. The inferior biocompatibility of PHEMA was ascribed to the stable network structure of water molecules. Some of the PHEMA co-polymers, on the other hand, were found to have highly improved biocompatibility. Mechanism for the improvement was discussed in terms of loosening the network structure, which could be brought about by introducing ionic groups or branching to the polymer chains through co-polymerization with appropriate 'key monomers'. The mobility of polymer chains, as well as the population of three kinds of water in polysaccharide molecules in aqueous medium could change in response to their chemical structure such as nature of ionic groups, the degree of branching, etc. Polysaccharides located at the utmost-outer layer of blood cells probably possess a loosened network structure to form soft biological surface where intermediate water predominates. Cellulose, on the other hand, has a common feature with PHEMA in the sense of predominance of the non-freezing water in its hydrated system. Note: The word 'biocompatibility' is used in general as the term evaluating properties of materials which do not cause adverse effect when the materials come into contact with living organisms, such as proteins, biological cells and tissues. This review paper primarily deals with 'biocompatibility' of polymer materials against various biological elements in blood flow system.

<p>Ocean circulation plays a central role on climate regulation. The paleoceanographic studies of the last decades have allowed to better document the variations in the production of the North Atlantic Deep Water (NADW). However, the role of intermediate water (IW) masses through time remains to be documented and is highly controversial. Indeed, some studies have highlighted the increased contribution of the Antarctic Intermediate Water (AAIW) in all ocean basins during the cold events recorded in the North Atlantic [1] while others suggest their absence [2]. Moreover, during the last deglaciation, the Southern Ocean played a fundamental role in the Carbon transfer from the deep ocean to the atmosphere via the increased upwelling associated to the AAIW production. In order to reconstruct the dynamics of IW masses, to better understand the relationships between variations in ocean circulation in the Atlantic and in the Southern Ocean, and the impact of these changes on the global carbon cycle during Termination I, we use two marine sediment cores from the Porcupine basin MD01-2461 (1153m) and the Iberian margin SU92-28 (997m). We combine the study of benthic foraminifera assemblages sensitive to variations in their environment (nutrient content, oxygen), and different geochemical proxies such as elemental ratios (Mg/Ca, Sr/Ca, Cd/Ca, Ba/Ca, B/Ca, Li/Ca and U/Ca), stable isotopes (δ18O and δ13C) and Neodymium isotopes records (eNd). On core SU92-28, past changes in the benthic foraminiferal content exhibit strong differences in the paleo-environments, with different ecological conditions from the LGM to the Holocene, as well as during the YD and H1 events. These differences are also observed in the δ13C, oxygen concentrations and elemental ratios records obtained from <em>Uvigerina peregrina (or U.mediterranea), Cibicidoides mundulus and Melonis affinis</em>. Changes in the Nd record allow to distinguish changes in the IW mass sources, reflecting the balance between Northern and Southern contributions. Future analysis (e.g., 14C reservoir ages) and the comparison with core MD01-2461 records will help to better constrain the North-South connections in the Atlantic Ocean at IW depths, and their impact on global climate changes.</p><p>[1] Ma et al. (2019) Geochemistry, Geophysics, Geosystems, 20(3), 1592-1608</p><p>[2] Gu, S., et al. (2017). Paleoceanography, 32, 1036-1053.</p>

Tissue engineering and regenerative medicine require biomaterials that balance blood compatibility with cell adhesion, proliferation, and differentiation. Chitosan and its derivatives, owing to their biocompatibility, biodegradability, and functional versatility, have been extensively explored for biomedical applications, including vascular grafts and tissue engineering scaffolds. This study investigates the effect of chemical modifications on the water state of chitosan derivatives─specifically, free water (FW), intermediate water (IW), and nonfreezing water (NFW)─and their implications for protein interactions, platelet adhesion, and mesenchymal stem cell (MSC) behavior. By incorporating hydrophilic and hydrophobic groups, the hydration of chitosan derivatives was precisely controlled, which significantly influenced blood compatibility and cell adhesion. Hexanoyl glycol chitosan (HGC) demonstrated reduced platelet adhesion, low fibrinogen denaturation, and favorable MSC adhesion, making it a promising candidate for applications requiring both enhanced blood compatibility and regenerative potential. These findings underscore the importance of hydration water modulation in designing advanced biomaterials for blood-contacting and regenerative medicine applications.

Research on global climate change has increasingly focused on rapid (century-scale and decadal) changes. One such climate shift, the Younger Dryas cooling event1, took place during the last deglaciation, from 13,000 to 11,700 years BP. Climate records from Greenland ice cores and North Atlantic sediment cores show high-frequency fluctuations implying significant (>5 °C) shifts in temperature at this time, taking place within 50–100 years (ref. 2). The origin of the Younger Dryas has recently been attributed to a reduction or cessation of deep-water production in the North Atlantic and a concurrent lessening of the heat flux from low latitudes3,4. The role of intermediate waters (1,000–2,000 m depth) is less certain, however, because climate proxies for this ocean reservoir are rare and ambiguous. Here we report on the use of a new climate archive, deep-sea corals from Orphan knoll (1,600m depth) in the northwestern Atlantic Ocean. The oxygen isotope ratios in the coral skeletons (accurately dated by the 230Th/234U chronometric method) change markedly coincident with the initiation of the Younger Dryas, suggesting that there were profound changes in intermediate-water circulation at this time.

Intermediate water (IW) in hydrated bioactive glasses remains uninvestigated. We obtained titanium (Ti)-containing bioactive glasses (BGTs) (Ti at 5%, 7.5% and 10% of the glass system) using the sol–gel technique. Their thermal, physicochemical, and morphological properties, before and after Ti-doping, were analysed using DTA, XRD, FTIR, TEM, and SEM accessorised with EDAX, and size distribution and zeta potential surface charges were determined using a NanoZetasizer. The IW in hydrated BGTs was investigated by cooling and heating runs of DSC measurements. Moreover, the mode of death in an osteosarcoma cell line (MG63) was evaluated at different times of exposure to BGT discs. Ti doping had no remarkable effect on the thermal, physicochemical, and morphological properties of BGTs. However, the morphology, size, and charges of BGT nano-powders were slightly changed after inclusion of Ti compared with those of BGT0; for example, the particle size increased with increasing Ti content (from 4–5 to 7–28 nm). The IW content was enhanced in the presence of Ti. The mode of cell death revealed the effect of IW content on the proliferation of cells exposed to BGTs. These findings should help improve the biocompatibility of inorganic biomaterials.

There are numerous parameters of polymeric biomaterials that can affect the protein adsorption and cell adhesion. The mechanisms responsible for the polymer/protein/cell interactions at the molecular level have not been clearly demonstrated, although many experimental and theoretical efforts have been made to understand these mechanisms. Water interactions have been recognized as fundamental for the protein and cell response to contact with polymers. This chapter focuses on the interfacial water at the polymer/protein/cell interfaces and specific water structure in hydrated biopolymers and bio-inspired water in hydrated synthetic polymers. Additionally, it highlights recent developments in the use of biocompatible polymeric biomaterials for medical devices and provides an overview of the progress made in the design of multifunctional element-block polymers by controlling the bio-inspired water structure through precision polymer synthesis.

: We present the first experimental measurements of the orientation and hydrogen bonding character of interfacial water molecules in their gaseous state in coexistence with the bulk liquid water. These interfacial vapor state molecules are distinct from the surface free OH and the interfacial liquid state water molecules and show a preferred orientation with their hydrogen atoms directed towards the liquid surface. The goal to develop a molecular level picture of water orientation and bonding at this vapor-liquid boundary where liquid phase water molecules coexist with vapor phase molecules has fascinated scientists for decades. Whereas most theoretical and experimental studies in recent years are converging on a consistent description of interfacial water on the liquid side of the interface, there is considerable disparity in the theoretical description of water molecules on the vapor side. A primary factor in this lack of consensus is the paucity of available data that unequivocally measures the properties of these interfacial vapor state molecules. As with theoretical efforts in this area, the low density of these vapor state interfacial water molecules is experimentally problematic. In this paper we present the first vibrational spectroscopic measurements of interfacial water vapor species in coexistence with their liquid phase. These detected vapor state molecules have a preferred orientation relative to the surface plane and have minimal hydrogen bonding to adjacent water molecules as manifested in the energy and linewidth of the spectral OH stretching modes examined. These molecules are distinctly different than the water molecules with a dangling bond into the vapor phase, or water in the liquid portion of the interface where hydrogen bonding between water molecules is strong.

Topological concepts have been introduced into electronic, photonic, and phononic systems, but have not been studied in surface-water-wave systems. Here we study a one-dimensional periodic resonant surface-water-wave system and demonstrate its topological transition. By selecting three different water depths, we can construct different types of water waves - shallow, intermediate and deep water waves. The periodic surface-water-wave system consists of an array of cylindrical water tanks connected with narrow water channels. As the width of connecting channel varies, the band diagram undergoes a topological transition which can be further characterized by Zak phase. This topological transition holds true for shallow, intermediate and deep water waves. However, the interface state at the boundary separating two topologically distinct arrays of water tanks can exhibit different bands for shallow, intermediate and deep water waves. Our work studies for the first time topological properties of water wave systems, and paves the way to potential management of water waves.

Interfacial processes can control the transport, speciation, and ultimate fate of aqueous pollutants in groundwater. Here, we apply resonantly enhanced second harmonic generation as well as the χ(3) technique to study the interaction of chromium(VI) with the (11̄02) α-Al2O3−water interface. Adsorption isotherm measurements yield free energies of adsorption that are consistent with a hydrogen-bonding mechanism mediated through the outer-sphere solvation shell of chromium(VI). Results from measurements regarding the charge state of the α-Al2O3−water interface as well as the chromium(VI) saturation surface coverages and the pH-dependence of the chromium(VI) equilibrium binding constants are used to develop a thermodynamic and mass-balanced model that describes the interfacial interactions on the molecular level. Special attention is paid to the interfacial speciation state of chromium(VI) as a function of bulk solution pH. Scaling up, we estimate the mobility of chromium(VI) in alumina-rich soils by using the Kd model. This work presents a significant advancement in our understanding of the molecular-level interactions between chromium(VI) and α-Al2O3 and improves our ability to predict the environmental mobility, speciation, and ultimate fate of chromium(VI).

Roles of interfacial water states on advanced biomedical material design

Responsive foams and interfaces are interesting building blocks for active materials that respond and adapt to external stimuli. We have used the photochromic reaction of a spiropyran sulfonate surfactant to render interfacial, rising bubbles as well as foaming properties active to light stimuli. In order to address the air-water interface on a molecular level, we have applied sum-frequency generation (SFG) spectroscopy which has provided qualitative information on the surface excess and the interfacial charging state as a function of light irradiation and solution pH. Under blue light irradiation, the surfactant forms a closed ring spiro form (SP), whereas under dark conditions the ring opens and the merocyanine (MC) form is generated. Using SFG spectroscopy, we show that at the interface, different pH conditions of the bulk solution lead to changes in the interfacial charging state. We have exploited the fact that the MC surfactant's O-H group can be deprotonated as a function of pH and used that to tune the molecules net charge at the interface. In fact, SFG spectroscopy shows that with increasing pH the intensity of the O-H stretching band from interfacial water molecules increases, which we associate to an increase in surface net charge. At a pH of 5.3, irradiation with blue light leads to a reversible decrease of O-H intensities, whereas the C-H intensities were unchanged compared to the corresponding intensities under dark conditions. These results are indicative of changes in the surface net charge with light irradiation, which are also expected to influence the foam stability via changes in the electrostatic disjoining pressure. In fact, measurements of the foam stabilities are consistent with this hypothesis and show higher foam stability under dark conditions. At pH 2.7 this behavior is reversed as far as the surface tension and surface charging as well as the foam stability are concerned. This is corroborated by rising bubble experiments, which demonstrated an unprecedented reduction of ∼30% in bubble velocity when the bubbles were irradiated with blue light compared to the velocity of bubbles with the surfactants in the dark state. Clearly, the light-triggered changes can be used to control foams, rising bubbles, and fluid interfaces on a molecular level which renders them active to light stimuli.

The nature of electron transfer across metal oxide-water interfaces depends significantly on the band gap of the oxide and its band edge energies relative to the potentials of relevant aqueous redox couples. Here we focus on the water interface with MgO, a prototypical wide band gap oxide whose conduction band edge is close in energy to that of water. We investigate the behavior of an excess electron at and out of equilibrium near the interface using ab initio molecular dynamics based on hybrid density functional theory. Our simulations show that under equilibrium conditions the excess electron (donated by an Al impurity in MgO) localizes to a midgap defect state comparable in energy and shape to a hydrated electron in bulk water. To characterize the electron transfer from the conduction band of MgO to interfacial product states, we dope near-equilibrium configurations of the pristine MgO-water system with Al and run short trajectories of these instantaneously out-of-equilibrium systems. We observe two distinct products associated with the excess electron: a surface-localized electron (esurf-) and an aqueous hydrogen radical (H•). The H• pathway exhibits a much higher activation barrier despite being more exoergic, making esurf- the kinetic product. Our characterization of the pathways on the basis of Marcus theory is consistent with the poor observed utility of MgO for water radiolysis. Moreover, we anticipate that the computational framework employed here will be broadly applicable to assessing electron transfer mechanisms at aqueous, photocatalytic interfaces.

Double-layer dynamics in the adsorption of tetrabutyl ammonium ions at the mercury—water interface: I: Survey

Influential mechanism of water occurrence states of waste-activated sludge: specifically focusing on the roles of EPS micro-spatial distribution and cation-dominated interfacial properties

In cellular respiration, cytochrome c transfers electrons from cytochrome bc(1) complex (complex III) to cytochrome c oxidase by transiently binding to the membrane proteins. Here, we report the structure of isoform-1 cytochrome c bound to cytochrome bc(1) complex at 1.9 A resolution in reduced state. The dimer structure is asymmetric. Monovalent cytochrome c binding is correlated with conformational changes of the Rieske head domain and subunit QCR6p and with a higher number of interfacial water molecules bound to cytochrome c(1). Pronounced hydration and a "mobility mismatch" at the interface with disordered charged residues on the cytochrome c side are favorable for transient binding. Within the hydrophobic interface, a minimal core was identified by comparison with the novel structure of the complex with bound isoform-2 cytochrome c. Four core interactions encircle the heme cofactors surrounded by variable interactions. The core interface may be a feature to gain specificity for formation of the reactive complex.