Viscosity Of Solutions Research Articles

IMPLICATIONS OF STORAGE CONDITIONS ON THE CHARACTERISTICS OF ALGINATE DIALDEHYDE AND ITS HYDROGELS

AbstractA review of recent literature reveals a spurt in the publications using alginate dialdehyde (ADA)‐based hydrogels. This study evaluates the stability and characteristics of ADA solutions stored at different temperatures (4 & −20 °C; designated as ADA4°C & ADA−20°C) and durations (1, 3, and 6 months), and gives valuable insights into the shelf life, a parameter important in a clinical setting. ADA solutions were characterized for their viscosity, aldehyde content, molecular weight, and chemical structure before and after storage. The solution viscosities of ADA4°C showed a decreasing trend over 6 months while that of ADA‐20°C showed an increase. Compared to freshly prepared ADA, a significant reduction in aldehyde content, from 40.1±1.4 % to 37.1±1.01 %, was observed for ADA4°C stored for 6 months, but the aldehyde content was stable for ADA−20°C stored for the same period. Molecular weight remained stable (~6800 g/mol) irrespective of the storage temperatures. Injectable hydrogels were prepared by reacting the stored ADA solutions with 20 % aqueous solutions of gelatin. Hydrogels prepared with ADA stored at 4 °C for 6 months showed a significant increase in gelation time from 4.3±1.5 to 8.79±0.1 min and a decrease in degree of crosslinking from 54.3±1.4 % to 29.2±2.3 %. A decreasing trend was observed for properties such as water uptake (from 470 to 961 %) and tensile strength (from 348 to 282 kPa). Hydrogels made with ADA−20°C demonstrated better retention of physicochemical properties over time. In vitro studies revealed that the hydrogels showed a non‐cytotoxic response towards L929 cells irrespective of the storage conditions. LIVE/DEAD assay and F‐Actin staining revealed good cell proliferation on the hydrogels. In conclusion, retention of the properties of ADA in its aqueous solution requires careful control of storage temperatures.

Effect of Molecules' Physicochemical Properties on Whey Protein/Alginate Hydrogel Rheology, Microstructure and Release Profile.

The encapsulation of molecules with different physicochemical properties (theophylline, blue dextran, salicylic acid and insulin) in whey protein (WP) and alginate (ALG) microparticles (MP) for oral administration was studied. MP based on WP/ALG were prepared by a cold gelation technique and coated with WP solution after reticulation. Molecules influenced polymer solution viscosity and elasticity, resulting in differences regarding encapsulation efficiency (from 23 to 100%), MP structure and swelling (>10%) and in terms of pH tested. Molecule release was due to diffusion and/or erosion of MP and was very dependent on the substance encapsulated. All the loaded MP were successfully coated, but variation in coating thickness (from 68 to 146 µm) and function of the molecules encapsulated resulted in differences in molecule release (5 to 80% in 1 h). Gel rheology modification, due to interactions between WP, ALG, calcium and other substances, was responsible for the highlighted differences. Measuring rheologic parameters before extrusion and reticulation appeared to be one of the most important aspects to study in order to successfully develop a vector with optimal biopharmaceutical properties. Our vector seems to be more appropriate for anionic high-molecular-weight substances, leading to high viscosity and elasticity and to MP enabling gastroresistance and controlled release of molecules at intestinal pH.

Chemical and physical characteristics of wheat root mucilage influenced by Serendipita indica symbiosis: a comparison among four cultivars.

Although there is evidence to suggest that the endophytic fungus Serendipita indica plays a crucial role in enhancing plant tolerance against biotic/abiotic stressors, less is known about the impacts of this symbiosis association on root mucilage chemical composition and its physical functions. The mucilage of inoculated and non-inoculated seedlings of four wheat cultivars (i.e., Roshan, Ghods, Kavir and Pishtaz) were extracted using an aeroponic method. Total solute concentration (TCm), carbon content (Cmucilage), electrical conductivity (EC), pH, fatty acids, surface tension (σm), and viscosity (ηm) of mucilage were measured. Ghods and Kavir had the highest and lowest root colonization percents, respectively. Saturated fatty acids, including palmitic and stearic acids, were dominant over unsaturated fatty acids in wheat root mucilage. However, their compositions were significantly different among wheat cultivars. S. indica colonization, especially for Ghods, increased the TCm, Cmucilage, and palmitic acid. Moreover, root mucilage of S. indica-inoculated Ghods had lower σm and greater ηm. An increased amount of powerful surfactants like palmitic acid in the mucilage of S. indica inoculated treatments led to lower σm and greater ηm. Such studies provide further support for the idea that plant-released mucilage plays a major role in modifying the physical environment of the rhizosphere. This knowledge toward truly understanding the rhizosphere can be potentially used for improving the rhizosphere soil quality and increasing crop growth and yield.

Computational Procedure for Predicting Excipient Effects on Protein-Protein Affinities.

Protein-protein interactions lie at the center of many biological processes and are a challenge in formulating biological drugs, such as antibodies. A key to mitigating protein association is to use small-molecule additives, i.e., excipients that can weaken protein-protein interactions. Here, we develop a computationally efficient model for predicting the viscosity-reducing effect of different excipient molecules by combining atomic-resolution MD simulations, binding polynomials, and a thermodynamic perturbation theory. In a proof of principle, this method successfully ranks the order of four types of excipients known to reduce the viscosity of solutions of a particular monoclonal antibody. This approach appears useful for predicting the effects of excipients on protein association and phase separation, as well as the effects of buffers on protein solutions.

Scrutinizing micellar transitions and interfacial properties in mixed micelles comprising sodium dodecyl sulfate and sodium oleate: A tensiometric and scattering insight

Mixed micellar systems play a pivotal role in numerous scientific and industrial applications due to their inimitable solution properties and potential for enhancing solubilization and emulsification processes. The present study unveils the mixed micellization behavior of two anionically charged surfactants, sodium dodecyl sulfate (SDS) and sodium oleate (SO), in aqueous solutions through a combination of solution viscosity, tensiometric and small-angle neutron scattering (SANS) techniques. The dynamic changes in the interfacial properties of the mixed micellar system as a function of the SDS-to-SO ratio are evaluated from surface tension measurements. The results offer an insight into the formation of the stable mixed micelles with the alteration in the critical micelle concentration (CMC) as a function of the composition of both surfactants and the nature of the interaction. Surface tension data disclose the thermodynamic aspects of micelle formation and the influence of surfactant interactions on the surface activity of the system. Complementing the surface tension measurements, SANS analysis was conducted to clarify the structural aspects of the SDS-SO mixed micelles. SANS inferred the micellar size, shape, and aggregation number (Nagg), thereby shedding light on the nanoscale organization of the micellar aggregates in the aqueous solution. By combining SANS and surface tension data, a comprehensive understanding of the mixed micellization behavior of SDS and SO is achieved, addressing both interfacial and structural aspects. A computational simulation approach has also been employed to obtain the optimized parameters, which provide a better understanding of the correlation of SDS and SO molecular orbital energy levels. The results underscore the importance of surface tension and structural characterization techniques to comprehend the behavior of mixed micelles fully.

High pressure homogenization: A promising approach to expand food applications of chia mucilage

Two chia mucilages with different viscosities, obtained by extraction conditions optimized in a previous work, were homogenized by high pressure homogenization (HPH). Particle size, molecular weight, zeta potential, FTIR spectrum, rheological properties, water absorption capacity, water holding capacity and iron binding capacity were determined on both mucilages treated and without treatment. Homogenization led to a significant reduction in viscosity respect to chia mucilage controls, which can be related to the decrease in particle size and molecular weight. A high iron binding capacity was obtained for both mucilages. FTIR spectra of both mucilages with iron showed displacements in bands related with stretching of carboxylic uronic acids, suggesting the interaction site with this mineral. This interaction was also verified by particle size determination with a displacement to higher sizes in the presence of iron. Potential zeta showed a significant reduction in the presence of iron. A model to explain the binding between chia mucilage and iron is proposed. HPH appears as an alternative to expand chia mucilage functionality reducing the viscosity of chia mucilage solutions for the offer of a new ingredient also with optimal levels of hydration and iron binding capacity.

Brownian dynamics simulations of bottlebrush polymers in dilute solution under simple shear and uniaxial extensional flows.

We study the dynamics of bottlebrush polymer molecules in dilute solutions subjected to shear and uniaxial extensional flows using Brownian dynamics simulations with hydrodynamic interaction (HI). Bottlebrush polymers are modeled using a coarse-grained representation, consisting of a set of beads interacting pairwise via a purely repulsive potential and connected by finitely extensible nonlinear springs. We present the results for molecular stretching, stress, and solution viscosity during the startup of flow as well as under steady state as a function of side chain length while keeping the backbone length fixed. In extensional flow, the backbone fractional extension and the first normal stress difference decrease with an increase in side chain length at a fixed Weissenberg number (Wi). Using simulation results both in the presence of and in the absence of HI, we show that this is primarily a consequence of steric interaction resulting from the dense grafting of side chains. In shear flow, we observe a shear-thinning behavior in all cases, although it becomes less pronounced with increasing side chain length. Furthermore, nonmonotonicity in the backbone fractional extension is observed under shear, particularly at high Wi. We contextualize our simulation results for bottlebrush polymers with respect to existing studies in the literature for linear polymers and show that the unique dynamical features characterizing bottlebrush polymers arise on account of their additional molecular thickness due to the presence of densely grafted side chains.

Optimization design and properties of PVA/GEL nanofibers

In this paper, the Optimization Design and properties of polyvinyl alcohol (PVA)/gelatin (GEL) nanofibers were studied. Different mass fractions of PVA (4, 5, 6 and 7 wt%), GEL (1, 2, 3 and 4 wt%), different spinning distances (8, 15, 22 and 29 cm), different voltages (10, 17, 24 and 31 kV), and different spinning speeds (0.1, 0.2, 0.3 and 0.4 mL) were designed into five factors and four levels by orthogonal experiments. The conductivity and viscosity of the mixed solution was tested. The PVA/GEL nanofibers were prepared by electrospinning and the morphology of composite nanofibers was observed under electron microscope. Finally, the PVA/GEL nanofiber film was tested by infrared spectroscopy and X-ray diffraction. The results showed that the infrared spectral groups and X-ray diffraction angles of nanofibers with different PVA/GEL ratios have little change. PVA/GEL nanofiber materials have great application potential in the field of biomedicine.

An Application of Polymer Nanocomposites Based On Carboxymethylcellulose along with Aluminium (Al) and Copper (Cu) Nanoparticles for Increasing Oil Production

As an agent for displacing residual and hard-to-recover oil reserves, polymer nanocomposites based on sodium salts of carboxymethylcellulose (CMC) and aluminium (Al) and copper (Cu) nanoparticles were investigated. It has been shown that polymer nanocomposites are more effective as oil displacement agents than the sodium salt of carboxymethylcellulose itself. Increasing the viscosity of an oil displacement solution can be achieved by varying the concentrations of CMC and nanoparticles. This study thoroughly examined the dynamic viscosities of carboxymethylcellulose (CMC) and polymer nanocomposites that contain CMC and metal nanoparticles (Al and Cu) across various concentrations. The results obtained are robust and reliable. It has been shown that, among polymer nanocomposites containing Al nanoparticles, there is a higher dynamic viscosity compared to its Cu nanoparticle counterpart at equivalent concentrations. This work proposes a simulation reservoir model to enhance oil recovery from hard-to-recovery reserves. Through this reservoir model simulation, the oil recovery factor was calculated using filler sand and oil extracted from a hydrocarbon field. The experimental data revealed the most effective concentration of CMC and nanoparticles for oil displacement. The results suggest that polymer nano composites composed of different metal nano powders have varying impacts on oil displacement efficiency. In this experiment, a composition consisting of Al nanoparticles with a size range of 50-70 manometers (nm) proved to be more successful as an oil displacement agent than a polymer nanocomposite made of Cu nanoparticles and CMC. At these concentrations and combinations, the highest oil recovery factors were achieved.

Ovalbumin amyloid-like fibrils/resveratrol self-assembling hydrogel: Preparation, characterization and formation mechanism

Food protein amyloid-like fibrils can significantly increase solution viscosity and promote the formation of entangled gel network due to its high stiffness and extreme aspect ratios. In this study, the ability of hydrophobic resveratrol (RES) deposited on the surface of the ovalbumin (OVA) amyloid-like fibrils (OVAF) to form a new self-assembling hydrogel was explored. The results showed that the simple mixing of RES and OVAF at pH 6.5 can successfully drive the formation of hybrid hydrogels through molecular self-assembly. The interactions between OVAF and RES were confirmed by the results of transmission electron microscope and fluorescence spectra. Non-covalent interactions including hydrophobic interactions and hydrogen bonds played an important role in the formation of the OVAF/RES self-assembling hydrogels. Furthermore, the OVAF/RES hydrogel showed a dense structure, high water holding capacity and remarkable rheological properties. The viscosity and storage modulus of the hybrid hydrogels increased with the increase of the RES and OVAF concentrations. After gastrointestinal digestion, some fibrous structures in the OVAF/RES hydrogels remained, which allowed for continuous release of RES. In summary, the OVAF/RES hybrid hydrogels with tunable structures, encapsulation ability and self-assembly characteristics are expected to be candidates for the delivery of hydrophobic active polyphenols in the food industry.

Electron beam irradiation induced aggregation, structural and functional changes of soybean 11S globulin

This study investigated the effects of different irradiation doses of an electron beam (e-beam) (0, 2, 4, 6, 8, and 10 kGy) on the structure, emulsification, foaming, and rheological and gel properties of soybean 11S globulin. The irradiation treatment at 4 and 6 kGy significantly increased the solubility, surface hydrophobicity, disulfide bonding, and ζ-potential of 11S globulin, decreased the particle size of the protein solution, and effectively improved the emulsifying activity and foaming stability of the protein solution. Moreover, irradiation induced moderate cross-linking and aggregation of the proteins, thereby increasing the apparent viscosity and shear stress of the protein solution. In addition, the low-field NMR and microstructure analysis results revealed that protein gels formed a dense and homogeneous three-dimensional mesh structure after irradiation (6 kGy), along with increased content of bound water (T2b) and water not readily flowable (T21) and a decrease content of free water (T22). Overall, our results confirmed that e-beam irradiation could significantly improve the physicochemical properties of soybean 11S globulin. Our study thus provides a new technical means for the application of electron beam irradiation technology toward protein modification and broadens the high-value utilization of soybean 11S globulin in the food processing industry.

The effect of solution viscosity on the quality of electroactive nanofibers produced by electrospinning

This work describes the modification of organic–inorganic nanofibrous templates for advanced electrotechnical applications and their filling with active particles from various materials, according to their intended use. The organic component of the templates consists of high molecular polyvinylpyrrolidone. The inorganic part is colloidal SiO2. The organic–inorganic templates produce by electrospinning can be filled with inorganic particles with diameter below 50 µm (for example, different types of spinels or electroactive nanopowders). The idea is to create a modifiable and flexible material for use as a template for electrodes or a solid electrolyte in a safe solid-state battery. The quality and properties of nanofibers are very important for advanced applications, and therefore, the optimization of the manufacturing process is needed. The most important property is the viscosity of the organic–inorganic solution for electrospinning. The influence of viscosity on the quality of nanofibrous layers was observed even with very subtle differences in viscosity. The age of the precursors and the resulting workability time also plays a significant role.Graphical abstract

Poly(glutamic acid)-Based Viscosity Reducers for Concentrated Formulations of a Monoclonal IgG Antibody.

Above a concentration threshold, the viscosity of solutions of proteins increases abruptly, which hampers the injectability of therapeutic formulations. Concentrations above 200 g/L are an ideal goal for subcutaneous application of antibodies. Molecular additives, such as amino acids (e.g., arginine) help decrease the viscosity, but they are used at concentrations as high as about 200 mmol/L. We addressed the question of whether poly(amino acids) could be more efficient than small molecular additives. We observed marked fluidification of a model therapeutic monoclonal antibody (mAb) solution by poly(d,l-glutamic acid) and poly(l-glutamic acid) derivatives added at concentrations of <6.5 g/L (i.e., a mAb/polymer chain molar ratio between 4:1 and 1:1 mol/mol). The bare poly(glutamate) parent chains were compared with polyethylene glycol-grafted chains as PEGylation is a common way to enhance stability. Viscosity could be decreased to ∼20 mPa s as compared to values of ∼100 mPa s in the absence of polymers at 200 g/L mAb. Formation of complexes between the mAb and the polyglutamates was characterized by capillary electrophoresis analysis in dilute solutions (1 g/L mAb) and by observation of phase separation at higher concentrations, suggesting tight association at about 2:1 mol/mol mAb/polymer. Altogether, these results show that polyglutamate derivatives hold an untapped potential as an excipient for fluidification of concentrated protein solutions.

Innovative submucosal injection solution for endoscopic resection with phosphorylated pullulan: a preclinical study

A submucosal injection solution is used to assist in endoscopic surgery. The high viscosity of current solutions makes them difficult to inject. In the present study, we developed an extremely low-viscosity, easy-to-use submucosal injection solution using phosphorylated pullulan (PPL). The PPL solutions were prepared at different concentrations, and their viscosities were measured. The mucosal elevation capacity was evaluated using excised porcine stomachs. Controls included 0.4% sodium hyaluronate (SH), 0.6% sodium alginate (SA), and saline. To evaluate the practicality, the catheter injectability of 0.7% PPL was measured, and EMR and endoscopic submucosal dissection (ESD) were performed using the stomach and colorectum of live pigs. As controls, 0.4% SH and saline were used. The PPL solutions were of extremely low viscosity compared to the solutions of 0.4% SH and 0.6% SA. Nevertheless, the mucosal elevation capacity of PPL solutions for up to 0.7% concentration was similar to that of 0.4% SH, and 0.7% PPL was less resistant to catheter infusion than 0.4% SH and 0.6% SA. In live pig experiments with endoscopic mucosal resection and ESD, snaring after submucosal injection of 0.7% PPL was easier than with 0.4% SH, ESD with 0.7% PPL produced less bubble formation than with 0.4% SH, and the procedure time tended to be shorter with 0.7% PPL than with 0.4% SH because of the shorter injection time. The PPL solution is an innovative and easy-to-use submucosal injection solution.

Ion effects on co-existing pseudo-phases in aqueous surfactant solutions: cryo-TEM, rheometry, and quantification

HypothesisSpecific alkaline cation effects control the area per headgroup of alkylester sulphates, which modifies the spontaneous packing of the surfactants. The resulting effective packing minimizes the total bending energy frustration and results in a Boltzmann distribution of coexisting pseudo-phases. These pseudo-phases constitute of micelles and other structures of complex morphology: cylindrical sections, end-caps, branching points, and bilayers, all in dynamic equilibrium. According to our model, excess of end-caps or excess of branching points lead to low viscosity, whereas comparable amounts of both structures lead to viscosity maxima. Relative occurrence of branching points and end-caps is the molecular mechanism at the origin of the salt-sensitive viscosity peak in the “salt-curve” (viscosity against salt concentration at fixed surfactant concentration). Up to now, and as indicated in former papers, this has been a pure model without microscopic verification. ExperimentsIn this work, we introduce explicit counting of the number of coexisting pseudo-phases as observed by state-of-the-art cryogenic transmission electron microscopy (cryo-TEM). The model system used, i.e., sodium laurylethersulfate (SLES)/salt/water, is very common as part of cosmetic formulations. As added salts, we used Li+, Na+, K+, and Cs+ chlorides. In parallel to imaging, we measured the macroscopic viscosities of the different solutions. FindingsWith cryogenic transmission electron microscopy (cryo-TEM), we imaged a variety of morphologies (pseudo-phases) in the different aqueous surfactant/salt solutions: cylindrical micelles with end-caps, discs surrounded by “rims”, entangled thread-like micelles with branching points, networks with gliding branching points, and bilayers. The relative chemical potentials of these morphologies could be approximated simply by counting the relative proportion of their occurrence. This simple multi-scale approach avoids any ad-hoc “specificity” assumption of ions, and is based on the bending energy model in an extended version of the Benedek “ladder model”. It is capable of explaining and even quantifying the location of all viscosity peaks in the “salt-curves” for the different cations investigated, thus confirming the previously proposed model experimentally, and – thanks to cryo-TEM – for the first time on a microscopic scale. Moreover, this approach can also be applied when the added cations lead to newly observed pseudo-phases, such as discs and vesicles. To the best of our knowledge, this is the first time that cryo-TEM is used, together with a mesoscopic model, to describe a macroscopic property such as viscosity and specific ion effects on it, without any a priori assumption about these effects. So, in total, we could a) confirm the predictions of the previously developed model, b) use cryo-TEM imaging and viscosity measurements to predict and find unusual morphologies when varying the cations of the added salt, and c) count the pseudo-phases in cryo-TEM micrographs to quantitatively explain the different nanostructures.

The physicochemical and DNA binding studies of ceftazidime pentahydrate and cefotaxime sodium in aqueous medium

Abstract Ceftazidime pentahydrate (CP) and cefotaxime sodium (CS) are semisynthetic cephalosporin antibiotics and are used to treat a variety of diseases worldwide. In order to explore the efficiency of a medicinal compound, it is important to have a deep understanding of its solution and physiochemical behaviour along with its interaction with biological molecules. In this regard, the solution of two drugs i.e., ceftazidime pentahydrate (CP) and cefotaxime sodium (CS) were investigated in detail. The physicochemical properties of drugs solutions and their interaction with deoxyribonucleic acid (DNA) were studied in water under varying experimental parameters. In the present study the physicochemical properties such as density, viscosity, surface tension, and conductance of aqueous solution, having various molar concentrations, of CP and CS were traced out at different temperatures. Five various concentrations (0.05, 0.1, 0.15, 0.2, and 0.3 mol dm−3) of each drug in an aqueous medium were prepared separately, and the physicochemical properties of each solution, were studied individually at temperatures such as 293, 303, 313, 323, and 333 K respectively. Most of these parameters have shown different behaviour with varying concentration of solution and temperature of the medium. In addition, these drugs showed a spontaneous surface-active and association behaviour in aqueous solutions and drug DNA solution. The flow behaviour, surface properties, volumetric behaviour and solute–solvent interaction of this drug were prominently influenced by experimental variables. UV-Visible spectroscopy was also used to study the interaction of these drugs with DNA in aqueous media in detail. Calculated values of binding constants (K b) for all drug–DNA are positive, indicating constructive binding and interactions between the molecules. In addition the binding efficiency of ceftazidime pentahydrate was found more than that of cefotaxime sodium. The interaction of drug–DNA was not only affected by the nature of the drug but also by the drug-to-DNA ratio and nature of the medium used.

Foam and emulsion properties of crude saponin extract from saffron (Crocus sativus L.) corm

The emulsion and foam stability of the crude saponin extract from the saffron corm (SS) were compared with commercially available saponin (CS) and Tween 60 (T60). The purity of the SS sample was calculated relative to CS and showed a value of 84.43%. Most stable emulsions with the smallest oil droplet size were acquired with T60. Also, T60 showed the lowest surface tension, interfacial tension, and the lowest contact angle. However, a reduction of interfacial tension and surface tension up to 77% and 32% was recorded for SS, respectively. Commercially available saponin indicated the best foam stability regarding film drainage, coalescence, and bubble disproportionation due to its highest solution viscosity. The antioxidant activity of samples was evaluated regarding the FRAP assay and the DPPH free radical scavenging activity. The results showed FRAP values of 2.41 and 1.20 mmol L−1 Fe (II)/100 g sample, and DPPH IC50 values of 2103 and 2326 mg kg−1 for CS and SS, respectively. The investigation showed that SS can form stable emulsions and abundant and persistent foams. Our results provide valuable insights for using saffron corm saponin extract as a new potential natural surfactant for selected applications of the food and pharmaceutical industries.

Protein Preferential Solvation in (Sucralose + Water) Mixtures.

Addition of sugars such as sucrose to aqueous protein solutions generally stabilizes proteins against thermal denaturation by preferential exclusion of sugars from proteins (preferential hydration of proteins). In this study, we investigated the effect of sucralose, a chlorinated sucrose derivative, on protein stability and preferential solvation. Circular dichroism and small-angle X-ray scattering measurements showed that sucrose increased the denaturation temperature of myoglobin and was preferentially excluded from the protein, whereas sucralose decreased the denaturation temperature of myoglobin and was preferentially adsorbed to the protein. No clear evidence was obtained for the indirect effects of sucralose on protein destabilization via the structure and properties of solvent water from the physicochemical properties (mass density, sound velocity, viscosity, and osmolality) of aqueous sucralose solutions; therefore, we concluded that a direct protein-sucralose interaction induced protein destabilization.

Mitigating chloride attack in cementitious materials without compromising other properties via the use of viscosity modifying admixture

To mitigate the harmful chemicals ingression into cementitious materials, traditional methods often aim to densify the pore structure, posing challenges for concrete dead-load or crack control. This paper proposes a facile method to mitigate chloride attack via increasing the pore solution viscosity in cementitious material without changing the matrix density or compromising other properties. The results indicate that the addition of viscosity modifying admixtures (VMAs) to the mortar, as an equivalent mass replacement of mixing water, can mitigate chloride ingress. Although it reduces the early age hydration heat, the mechanical strength at full age (3 d–28 d) and the porosity at 28 d remain unchanged when using an effective VMA (PEG1000). In addition, the matrix resistance to leaching is improved as well. These results may be attributed to the enhanced pore solution viscosity and the coexistence of VMA and C–S–H with decreased interlayer distance and shortened mean chain length. After 28 d of exposure, the most effective experimental group (PEG1000) showed approximately a 28 % decrease in chloride diffusion coefficient compared to the control group. This paper may inspire new technology to mitigate ions diffusion and promote its practical application.

A Low-Cost, Tabletop LOD-EPR System for Nondestructive Quantification of Iron Oxide Nanoparticles in Tissues.

Iron oxide nanoparticles (IONPs) have wide utility in applications from drug delivery to the rewarming of cryopreserved tissues. Due to the complex behavior of IONPs (e.g., uneven particle distribution and aggregation), further developments and clinical translation can be accelerated by having access to a noninvasive method for tissue IONP quantification. Currently, there is no low-cost method to nondestructively track IONPs in tissues across a wide range of concentrations. This work describes the performance of a low-cost, tabletop, longitudinally detected electron paramagnetic resonance (LOD-EPR) system to address this issue in the field of cryopreservation, which utilizes IONPs for rewarming of rat kidneys. A low-cost LOD-EPR system is realized via simultaneous transmit and receive using MHz continuous-wave transverse excitation with kHz modulation, which is longitudinally detected at the modulation frequency to provide both geometric and frequency isolation. The accuracy of LOD-EPR for IONP quantification is compared with NMR relaxometry. Solution measurements show excellent linearity (R2 > 0.99) versus Fe concentration for both measurements on EMG308 (a commercial nanoparticle), silica-coated EMG308, and PEG-coated EMG308 in water. The LOD-EPR signal intensity and NMR longitudinal relaxation rate constant (R1) of water are affected by particle coating, solution viscosity, and particle aggregation. R1 remains linear but with a reduced slope when in cryoprotective agent (CPA) solution, whereas the LOD-EPR signal is relatively insensitive to this. R1 does not correlate well with Fe concentration in rat kidney sections (R2 = 0.3487), while LOD-EPR does (R2 = 0.8276), with a linear regression closely matching that observed in solution and CPA.