Phospholipid Bilayer Inspired Sandwich Structural Nanofibrous Membrane for Atmospheric Water Harvesting and Selective Release.

Atmospheric water harvesting (AWH) has been broadly exploited to meet the challenge of water shortage. Despite the significant achievements of AWH, the leakage of hydroscopic salt during the AWH process hinders its practical applications. Herein, inspired by the unique selective permeability of the phospholipid bilayer, a sandwich structural (hydrophobic-hydrophilic-hydrophobic) polyacrylonitrile nanofibrous membrane (San-PAN) was fabricated for AWH. The hydrophilic inner layer loaded with LiCl could capture water from the air. The hydrophobic microchannels in the outer layer could selectively allow the free transmission of gaseous water molecules but confine the hydroscopic salt solution in the hydrophilic layer, achieving continuous and recyclable water sorption/desorption. As demonstrated, the as-prepared AWH devices presented high-efficient adsorption kinetics from 1.66 to 4.08 g g-1 at 30% to 90% relative humidity. Thus, this work strengthens the understanding of the water transmission process along microchannels and provides insight into the practical applications of AWH.

Simultaneous Water Sorption and Crystallization in ASDs 2: Modeling Long-Term Stabilities.

The physical stability of amorphous solid dispersions (ASDs) is a major topic in the formulation research of oral dosage forms. To minimize the effort of investigating the long-term stability using cost- and time-consuming experiments, we developed a thermodynamic and kinetic modeling framework to predict and understand the crystallization kinetics of ASDs during long-term storage below the glass transition. Since crystallization of the active phrarmaceutical ingredients (APIs) in ASDs largely depends on the amount of water absorbed by the ASDs, water-sorption kinetics and API-crystallization kinetics were considered simultaneously. The developed modeling approach allows prediction of the time evolution of viscosity, supersaturation, and crystallinity as a function of drug load, relative humidity, and temperature. It was applied and evaluated against two-year-lasting crystallization experiments of ASDs containing nifedipine and copovidone or HPMCAS measured in part I of this work. We could show that the proposed modeling approach is able to describe the interplay between water sorption and API crystallization and to predict long-term stabilities of ASDs just based on short-term measurements. Most importantly, it enables explaining and understanding the reasons for different and sometimes even unexpected crystallization behaviors of ASDs.

Understanding the Wettability of C1N1 (Sub)Nanopores: Implications for Porous Carbonaceous Electrodes.

Understanding how water interacts with nanopores of carbonaceous electrodes is crucial for energy storage and conversion applications. A high surface area of carbonaceous materials does not necessarily need to translate to a high electrolyte-solid interface area. Herein, we study the interaction of water with nanoporous C1N1 materials to explain their very low specific capacitance in aqueous electrolytes despite their high surface area. Water was used to probe chemical environments, provided by pores of different sizes, in 1H MAS NMR experiments. We observe that regardless of their high hydrophilicity, only a negligible portion of water can enter the nanopores of C1N1, in contrast to a reference pure carbon material with a similar pore structure. The common paradigm that water easily enters hydrophilic pores does not apply to C1N1 nanopores below a few nanometers. Calorimetric and sorption experiments demonstrated strong water adsorption on the C1N1 surface, which restricts water mobility across the interface and impedes its penetration into the nanopores.

Sequential Water Sorption/Desorption of a Nonporous Adaptive Organic Ligand Bridged Coordination Polymer for Atmospheric Moisture Harvesting.

Moisture harvesters with favourable attributes such as easy synthetic availability and good processability as alternatives for atmospheric moisture harvesting (AWH) are desirable. This study reports a novel nonporous anionic coordination polymer (CP) of uranyl squarate with methyl viologen (MV2+ ) as charge balancing ions (named U-Squ-CP) which displays intriguing sequential water sorption/desorption behavior as the relative humidity (RH) changes gradually. The evaluation of AWH performance of U-Squ-CP shows that it can absorb water vapor under air atmosphere at a low RH of 20 % typical of the levels found in most dry regions of the world, and have good cycling durability, thus demonstrating the capability as a potential moisture harvester for AWH. To the authors' knowledge, this is the first report on non-porous organic ligand bridged CP materials for AWH. Moreover, a stepwise water-filling mechanism for the water sorption/desorption process is deciphered by comprehensive characterizations combining single-crystal diffraction, which provides a reasonable explanation for the special moisture harvesting behaviour of this non-porous crystalline material.

Impact of Aluminum Oxide Nanocoating on Drug Release from Amorphous Solid Dispersion Particles.

Atomic layer coating (ALC) is emerging as a particle engineering strategy to inhibit surface crystallization of amorphous solid dispersions (ASDs). In this study, we turn our attention to evaluating drug release behavior from ALC-coated ASDs, and begin to develop a mechanistic framework. Posaconazole/hydroxypropyl methylcellulose acetate succinate was used as a model system at both 25% and 50% drug loadings. ALC-coatings of aluminum oxide up to 40 nm were evaluated for water sorption kinetics and dissolution performance under a range of pH conditions. Scanning electron microscopy with energy dispersive X-ray analysis was used to investigate the microstructure of partially released ASD particles. Coating thickness and defect density (inferred from deposition rates) were found to impact water sorption kinetics. Despite reduced water sorption kinetics, the presence of a coating was not found to impact dissolution rates under conditions where rapid drug release was observed. Under slower releasing conditions, underlying matrix crystallization was reduced by the coating, enabling greater levels of drug release. These results demonstrate that water was able to penetrate through the ALC coating, hydrating the amorphous solid, which can initiate dissolution of drug and/or polymer (depending on pH conditions). Swelling of the ASD substrate subsequently occurs, disrupting and cracking the coating, which serves to facilitate rapid drug release. Water sorption kinetics are highlighted as a potential predictive tool to investigate the coating quality and its potential impact on dissolution performance. This study has implications for formulation design and evaluation of ALC-coated ASD particles.

Zirconia Nanoparticles as Reinforcing Agents for Contemporary Dental Luting Cements: Physicochemical Properties and Shear Bond Strength to Monolithic Zirconia.

Nanofillers in resin materials can improve their mechanical and physicochemical properties. The present work investigated the effects of zirconia nanoparticles (NPs) as fillers in commercial dental luting cements. Two dual-cured self-adhesive composites and one resin modified glass ionomer (RMGI) luting cement were employed. Film thickness (FT), flexural strength (FS), water sorption (Wsp), and shear bond strength (SBS) to monolithic zirconia were evaluated according to ISO 16506:2017 and ISO 9917-2:2017, whereas polymerization progress was evaluated with FTIR. Photopolymerization resulted in double the values of DC%. The addition of 1% wt NPs does not significantly influence polymerization, however, greater amounts do not promote crosslinking. The sorption behavior and the mechanical performance of the composites were not affected, while the film thickness increased in all luting agents, within the acceptable limits. Thermocycling (TC) resulted in a deteriorating effect on all composites. The addition of NPs significantly improved the mechanical properties of the RMGI cement only, without negatively affecting the other cements. Adhesive primer increased the initial SBS significantly, however after TC, its application was only beneficial for RMGI. The MDP containing luting cement showed higher SBS compared to the RMGI and 4-META luting agents. Future commercial adhesives containing zirconia nanoparticles could provide cements with improved mechanical properties.

Impact of Dye Encapsulation in ZIF-8 on CO2, Water, and Wet CO2 Sorption.

The fast adsorption kinetics of zeolitic imidazolate frameworks (ZIFs) enable a wide range of sorption applications. The most commonly used framework, ZIF-8, is relatively non-polar. Increasing the polarity of ZIF-8 through the encapsulation of different polar species shows promise for enhancing the sorption performance for pure CO2. Recently, the outlook has re-focused on gas mixtures, mostly in the context of post-combustion CO2 capture from wet flue gasses. While water is known to sometimes have a synergistic effect on CO2 sorption, we still face the potential problem of preferential water vapor adsorption. Herein, we report the preparation of three ZIF-8/organic dye (OD) composites using Congo red, Xylenol orange, and Bromothymol blue, and their impact on the sorption properties for CO2, water, and a model wet CO2 system at 50% RH. The results show that the preparation of OD composites can be a promising way to optimize adsorbents for single gasses, but further work is needed to find superior ZIF@OD for the selective sorption of CO2 from wet gas mixtures.

Consecutive Single-Crystal-to-Single-Crystal Isomerization of Novel Octamolybdate Anions within a Microporous Hybrid Framework with Robust Water Sorption Properties.

The 3D hybrid framework [{Cu(cyclam)}3 (κ-Mo8 O27 )] ⋅ 14H2 O (1) (cyclam=1,4,8,11-tetraazacyclotetradecane) undergoes sequential single-crystal-to-single-crystal transformations upon heating to afford two different anhydrous phases (2 a and 3 a). These transitions modify the framework dimensionality and enable the isomerization of κ-octamolybdate (κ-Mo8 ) anions into λ (2 a) and µ (3 a) forms through metal migration. Hydration of 3 a involves condensation of one water molecule to the cluster to afford the γ-Mo8 isomer in 4, which dehydrates back into 3 a through the 6 a intermediate. In contrast, 2 a reversibly hydrates to form 5, exhibiting the same Mo8 cluster as that of 1. It is remarkable that three of the Mo8 clusters (κ, λ and µ) are new and that up to three different microporous phases can be isolated from 1 (2 a, 3 a, and 6 a). Water vapor sorption analyses show high recyclability and the highest uptake values for POM-based systems. The isotherms display an abrupt step at low humidity level desirable for humidity control devices or water harvesting in drylands.

Covalent Organic Frameworks for Extracting Water from Air.

Water scarcity is becoming an increasingly pressing issue due to global population growth and industrialization. One effective approach to addressing this issue is sorption-based atmospheric water harvesting (SAWH). Covalent organic frameworks (COFs) are a type of porous crystalline material that have emerged as promising sorbents for water harvesting due to their high surface area, tunable pore size, and customizable pore chemistry. In this mini-review, we provide an overview of the different types of COFs, their structural characteristics, and the diverse linkage chemistries used to construct them. Then, we summarize recent advances in using COF-based sorbents for atmospheric water harvesting, including strategies for controlling sorption properties and optimizing performance in terms of thermodynamics and dynamics. Finally, we discuss prospects and challenges associated with improving the efficiency of COF-based SAWH systems.

Measuring and Modeling Water Sorption in Amorphous Indomethacin and Ritonavir.

The amorphous state of an active pharmaceutical ingredient (API) enhances its water solubility compared to its crystalline state. However, it is well known that amorphous substances can absorb significant amounts of water therewith inducing API recrystallization. This work explores methods to obtain reliable information about water sorption in amorphous APIs and its modeling. Experimental water-sorption curves over a broad humidity range were obtained by measuring the mass increase of well-defined films of amorphous APIs. Water-sorption isotherms modeled using perturbed-chain statistical associating fluid theory (PC-SAFT) showed better accordance with the experimental data than those obtained using the Flory-Huggins model. Crank's diffusion equation was used to describe the water-sorption kinetics providing Fickian diffusion coefficients of water in indomethacin and in ritonavir. Stefan-Maxwell diffusion coefficients were obtained by converting Fickian diffusion coefficients using water activity coefficients obtained from PC-SAFT. Finally, the free-volume theory was applied to explain the persistent water concentration dependency of the Stefan-Maxwell diffusion coefficients.

The Shelf Life of ASDs: 1. Measuring the Crystallization Kinetics at Humid Conditions.

Amorphous solid dispersions (ASDs), where an active pharmaceutical ingredient (API) is dissolved in a polymer, are a favored formulation technique to achieve sufficient bioavailability of poorly water-soluble APIs. The shelf life of such ASDs is often limited by API crystallization. Crystallization depends strongly on the storage conditions (relative humidity and temperature) and the polymer selected for generating the ASD. Determining the crystallization kinetics of ASDs under various conditions requires suitable analytical methods. In this work, two different analytical methods were compared and cross-validated: The first builds on water-sorption measurements combined with thermodynamic predictions ( Eur. J. Pharm. Biopharm. 2018, 127, 183-193, DOI: 10.1016/j.toxrep.2018.11.002), whereas the second applies Raman spectroscopy. Using the two independent methods, factors influencing the crystallization kinetics of ASDs containing the API griseofulvin were investigated quantitatively. It was found that crystallization kinetics increases with increasing temperature and relative humidity. Additionally, the influence of different polymers (poly(vinylpyrrolidone-co-vinyl acetate) and Soluplus) on crystallization kinetics were investigated. The experimentally obtained crystallization kinetics were described using the Johnson-Mehl-Avrami-Kolmogorov model and are the basis for future shelf life predictions at desired storage conditions.

A Phase-Dependent Effect That Enables Multi-Scale Moisture Measurements in Heterogeneous Substrates Using Tubular RH Sensors.

A knowledge of the moisture in soils/soil litter allows for the estimation of irrigation needs or the risk of forest fire. A membrane-based humidity sensor (MHS) can measure the relative humidity (RH) as an average value in such heterogeneous substrates via its sensitive tubular silicone membrane. This RH corresponds to the moisture-dependent water potential of the substrate. For humid conditions in soil, however, the RH is already larger than 98% and hence is insensitively correlated with the water potential. For such conditions, a step-like response of the MHS was found, which occurs if the silicone membrane is wetted with water. This appears to correspond to oversaturated water vapor and must be attributed to a phase-dependent sorption mechanism of the membrane. This effect allows the expansion of the range of applications of the MHS in the detection of liquid water, such as in dew point detection. Based on this, the dependency of the measurement signal on the mean water saturation in a substrate along the tubular membrane is demonstrated. A comparison of the measurement signal with an internal reference signal according to the MHS measurement principle makes it possible to distinguish this new, saturation-dependent measurement scale from the one used for RH measurement.

Antibacterial and Physical Properties of PVM/MA Copolymer- Incorporated Polymethyl Methacrylate as a Novel Antimicrobial Acrylic Resin Material.

Polymethyl methacrylate (PMMA), an acrylic resin used in orthodontic appliances and removable dentures for its biocompatibility and esthetics, may harbor bacteria on its surface. The present study investigated a new PMMA formula with Gantrez: an antibacterial copolymer of methyl vinyl ether and maleic acid (PVM/MA). Samples were tested for mechanical properties (surface hardness, flexural strength, water sorption, and water solubility) and effects against Streptococcus mutans. Six groups (0%-control, 5%, 10%, 15%, 20%, and 25% Gantrez) of n = 12 were fabricated for physical property tests and analyzed with one-way ANOVA and Prism 6. From these results, three groups (0%, 5%, and 10% Gantrez) were selected for antibacterial tests, and data were analyzed with one-way ANOVA and Tukey's multiple comparison test. Adding 5% and 10% Gantrez into PMMA significantly decreased S. mutans adhesion. There was no significant difference between the control vs. 5%, 10%, 15%, and 20% Gantrez (p > 0.05) for surface hardness, the control vs. 5% Gantrez (p > 0.05) for flexural strength, and the control vs. 5 and 10% Gantrez for water sorption and water solubility. Overall, incorporating 5% Gantrez into PMMA may be a promising solution to reduce bacterial adhesion without changing the acrylic resin's physical properties.

Graphene-doped Poly(methyl-methacrylate) as an enhanced biopolymer for medical device and dental implant.

Graphene-doping procedure represents a useful procedure to improve the mechanical, physical and biological response of several PMMA-derived polymers and biomaterials for dental applications. The aim of the study was to evaluate measure water sorption, water solubility and tolerance trough the rabbit pyrogen testing pyrogen detection of Graphene doped Poly (methyl methacrylate) (PMMA) compared with PMMA as potential materials for dental implant device. A total of 8 aged and unaged samples Graphene doped PMMA and PMMA were tested for water sorption and water solubility of the specimens. The experimental condition was evaluated according to the ISO 20795-1:2013 protocol. The biopolymer tolerance was evaluated in vivo on animals through the pyrogen detection test, acute intracutaneous and systemic irritation test. After wet conditioning both of Graphene doped PMMA and PMMA reported an increase of the weight. All the experimental samples showed a drastic low level of water sorption and solubility. Graphene doped PMMA unaged specimens showed a stability of physical and optical feature after the treatment. The Graphene doped PMMA has not shown pyrogens, an intradermal and systemic irritant effect on animals. The Graphene-doped PMMA satisfy the standard requirements and provide a physical and optical stability of the compound after the treatment. Further in vivo findings are required for future clinical application of the compound.

Influence of variations in the environmental pH on the solubility and water sorption of a calcium silicate-based root canal sealer.

AIM: To evaluate the influence of pH variation on the solubility and water sorption of a premixed calcium silicate-based root canal sealer (EndoSequence BC Sealer) compared to the gold standard based on epoxy resin (AH Plus Jet) after immersion in distilled water and phosphate-buffered saline (PBS). METHODOLOGY: Solubility and water sorption were evaluated after immersion in distilled water or PBS at several pHs (5, 7 and 12) and the values were calculated as percentages of the original mass after 24 h, 7 and 30 days of immersion. The crystalline structures present in the sealers and surface precipitates were assessed by X-ray diffraction. The Shapiro-Wilk's test revealed that data were normally distributed; thus, statistical analysis was performed using one-way anova and Tukey's tests or independent t-test, assuming a 5% α-error. RESULTS: EndoSequence BC Sealer was associated with significantly greater water sorption and solubility compared to AH Plus Jet in all tested conditions (P < 0.05). The acid environment increased the 24 h solubility of EndoSequence BC Sealer immersed in PBS (P < 0.05) and did not induce significative changes in the water sorption (P > 0.05). Alkaline pH reduced the solubility of EndoSequence BC Sealer and increased that of AH Plus Jet at all experimental times and soaking media (P < 0.05). Alkaline environment also significantly increased the water sorption of AH Plus Jet immersed in PBS (P < 0.05). Immersion in PBS significantly reduced the solubility of EndoSequence BC Sealer and significantly increased that of AH Plus Jet (P < 0.05). Precipitates on the surface of EndoSequence BC Sealer corresponding to hydroxyapatite and calcium carbonate were detected after immersion in PBS at pH 5 and 7 for 30 days. CONCLUSIONS: EndoSequence BC Sealer had significantly greater solubility and water sorption than AH Plus Jet. Although the alkaline pH and soaking media directly influenced the solubility and water sorption of the sealers, the solubility of AH Plus Jet remained within the limits recommended by ISO 6876, whilst the solubility of the EndoSequence BC Sealer did not comply with ISO recommendations in all the conditions tested.

Effect of equilibrium pH on the structure and properties of bleach-damaged human hair fibers.

Hair proteins are significantly affected by environmental pH. This impact tends to increase with prior hair damage. To understand how pH affects bleached hair properties, we utilized a number of techniques allowing for the determination of hair thermal properties, swelling and water sorption, and dry and wet tensile properties. At pH 5, hair proteins had the best structural integrity, as determined by differential scanning calorimetry and the highest tensile modulus. At pH 10, protein cross-linking density decreased, water content and hair cross-sectional diameter increased. Alkaline treatment, when compared with pH 5, did not reduce intermediate filament conditions (evaluated via enthalpy measurement) nor mechanical property performance in the wet state. In contrast to alkaline-treated hair, bleached hair equilibrated at pH 3 behaved very differently: it contained two different crosslink density zones, was the least stiff in dry and stiffest in wet conditions. Additionally, it absorbed less water and had the lowest diameter because of reduced water binding by protonated carboxyl groups. The pH 3 to 10 did not affect the mechanical strength of bleached hair in dry or wet conditions.

Water Distribution and Clustering on the Lyophilized IgG1 Surface: Insight from Molecular Dynamics Simulations.

Water has a critical role in the stability of the higher-order structure of proteins. In addition, it is considered to be a major destabilization factor for the physical and chemical stability of freeze-dried proteins and peptides. Physical and chemical aspects of protein/water relationships are commonly studied with the use of water vapor sorption isotherms for amorphous lyophilized proteins, which, in turn, are commonly analyzed using the Brunauer-Emmett-Teller (BET) equation to obtain the parameters, Wm and CB. The parameter Wm is generally referred to as the "monolayer limit of adsorption" and has a narrow range of 6-8% for most proteins. In this study, the water distribution on an IgG1 surface is investigated by molecular dynamics (MD) simulations at different water contents. The monolayer of water molecules was found to have limited coverage of the protein surface, and the true monolayer coverage of the protein globule actually occurs at a hydration level above 30%. The distribution of water molecules on the IgG1 surface is also highly heterogeneous, and the heterogeneity is not considered in the BET theory. In this study, a mechanistic model has been developed to describe the water vapor sorption isotherm. This model is based on the analysis of the hydrogen bonding network extracted from the MD simulations. The model is consistent with the experimental Type-II isotherm, which is usually observed for proteins. The physical meaning of the BET monolayer was redefined as the onset of water cluster formation. A simple model to calculate the onset water level, Wm, is proposed based on the hydration of different amino acids, as determined from the MD simulations.

Novel Urethane-Dimethacrylate Monomers and Compositions for Use as Matrices in Dental Restorative Materials.

In this study, novel urethane-dimethacrylate monomers were synthesized from 1,3-bis(1-isocyanato-1-methylethyl)benzene (MEBDI) and oligoethylene glycols monomethacrylates, containing one to three oxyethylene groups. They can potentially be utilized as matrices in dental restorative materials. The obtained monomers were used to prepare four new formulations. Two of them were solely composed of the MEBDI-based monomers. In a second pair, a monomer based on triethylene glycol monomethacrylate, used in 20 wt.%, was replaced with triethylene glycol dimethacrylate (TEGDMA), a reactive diluent typically used in dental materials. For comparison purposes, two formulations, using typical dental dimethacrylates (bisphenol A glycerolate dimethacrylate (Bis-GMA), urethane-dimethacrylate (UDMA) and TEGDMA) were prepared. The monomers and mixtures were tested for the viscosity and density. The homopolymers and copolymers, obtained via photopolymerization, were tested for the degree of conversion, polymerization shrinkage, water sorption and solubility, hardness, flexural strength and modulus. The newly developed formulations achieved promising physico-chemical and mechanical characteristics so as to be suitable for applications as dental composite matrices. A combination of the MEBDI-based urethane-dimethacrylates with TEGDMA resulted in copolymers with a high degree of conversion, low polymerization shrinkage, low water sorption and water solubility, and good mechanical properties. These parameters showed an improvement in relation to currently used dental formulations.

A Hydrolytically Stable Vanadium(IV) Metal-Organic Framework with Photocatalytic Bacteriostatic Activity for Autonomous Indoor Humidity Control.

Metal-organic frameworks (MOFs) with long-term stability and reversible high water uptake properties can be ideal candidates for water harvesting and indoor humidity control. Now, a mesoporous and highly stable MOF, BIT-66 is presented that has indoor humidity control capability and a photocatalytic bacteriostatic effect. BIT-66 (V3 (O)3 (H2 O)(BTB)2 ), possesses prominent moisture tunability in the range of 45-60 % RH and a water uptake and working capacity of 71 and 55 wt %, respectively, showing good recyclability and excellent performance in water adsorption-desorption cycles. Importantly, this MOF demonstrates a unique photocatalytic bacteriostatic behavior under visible light, which can effectively ameliorate the bacteria and/or mold breeding problem in water adsorbing materials.

Mechanical and hydrolytic degradation of an Ormocer®-based Bis-GMA-free resin composite.

OBJECTIVES: The aim of the study was to evaluate the mechanical stability of bisphenol A-glycidyl methacrylate (Bis-GMA) and Ormocer-based resin composites before and after water absorption and to examine water saturation. MATERIAL AND METHODS: Disc-shaped specimens of the Bis-GMA (Grandio SO, Voco) and the Ormocer-based (Admira Fusion, Voco) dental resin composites were produced, stored in water, and weighed after pre-determined times to measure the absorbed water. Bend bars were produced and stored for 24 h in dry conditions as well as in distilled water for 14 days or 60 days at 37 °C. The initial flexural strength (FS) under quasi-static loading and flexural fatigue strength (FFS) under cyclic loading were determined under 4-point bending. Fracture toughness (KIc) of both composites was measured using the single-edge-V-notch-beam (SEVNB) technique after the same storage conditions under 3-point bending. RESULTS: Within the first 14 days, storage conditions did not affect the initial FS of Grandio SO, while a significant drop in initial FS was observed for Admira Fusion after 2 weeks in water and most of the water was absorbed within this time. FFS for the Bis-GMA composite was not reduced before 2 months in water, whereas for the Ormocer®-based composite, there has been a significant decrease in strength after cyclic fatigue already at 2 weeks of water storage. KIc of Admira Fusion decreased significantly after both storage periods, while KIc of Grandio SO decreased only significantly after 2 weeks of water storage. CONCLUSION: All mechanical properties of the Bis-GMA composite were superior to those of the Ormocer®-based material, except water sorption. CLINICAL SIGNIFICANCE: Water storage seems to have a much more pronounced effect on the mechanical properties of Ormocer®-based dental composites in comparison to Bis-GMA-based composites.