Aqueous Calcium Chloride Research Articles

Controlled fabrication of multi-core alginate microcapsules

In this work, we present a robust microfluidic platform for controlled and complete on-chip generation of alginate microcapsules with single and double liquid cores. A combined Coflow and T-junction configuration implemented in a hybrid glass-PDMS (Polydimethylsiloxane) device is used for the generation of microcapsules with oil as liquid core. Frequency matching of oil-alginate double emulsion generation with that of aqueous Calcium chloride droplet generation allows for controlled merging of the two, resulting in reliable production of microcapsules. Confocal imaging of microcapsule cross-section reveals presence of intact liquid core. In the case of double core microcapsules, the two cores are well separated by alginate layer ensuring their long term stability. The current approach is expected to have advantages over existing techniques for liquid core microcapsule generation in terms of continuity of the process, control over core stability, and non-damage to cells when used for cell encapsulation applications.

Detecting phase transitions in a CaCl2-H2O system at low temperatures using a fiber-optic Fresnel reflection sensor.

Temperature-induced crystallization events in an aqueous calcium chloride solution in the concentration range of 15-40 mass% are monitored using an optical fiber Fresnel reflection sensor in the temperature range of 30°C to -200°C. The deviation of the phase boundary from equilibrium and the formation of an eutectic mixture followed by its densification during rapid cooling are inferred from the distinct signatures of the optical fiber sensor via the changes in refractive index. During the natural heating at laboratory ambient conditions, the optical signals impart the completion of dissolution of ice and CaCl2·6H2O. The corresponding temperatures have been used in Linke's equations to obtain the salinities, which are in good agreement with the intended solution concentrations. The sensor signal imparts simultaneous melting of the constituents of the eutectic mixture of a 29.7 mass% solution during the natural heating phase. The persistence of the metastable liquid phase at -200°C for tens of minutes followed by solidification is observed at all the concentrations studied. Finally, the feasibility of monitoring phase transitions in a NaCl-CaCl2-H2O system has been demonstrated.

The effect of microwave on the primary nucleation of CaSO4 from aqueous solutions

The effect of microwave on reactive crystallization is studied by measuring the induction time when nucleation is predominantly homogeneous and predominantly heterogeneous, respectively. Calcium sulfate is used as the working substance precipitated by mixing aqueous calcium chloride and sodium sulfate solutions. The experiments were carried with various microwave energy inputs. It is observed that the induction time significantly decreases with the increase of microwave energy input.The mechanism of the microwave effect on primary nucleation is analyzed. The main effect of microwave on primary nucleation is to increase the diffusion coefficient (DAB). The surface tension (γCL) changes only slightly or remains constant in the microwave field. In addition, when nucleation is predominantly heterogeneous, the effect of microwave on contact angle (θ), geometric factor (f) is not significant. This suggests that diffusion coefficient acceleration is the main reason for the reduction of the induction time. It is also found that DAB-D0 has an exponential relationship with the energy input value of microwave. At the same energy input level, compared to homogeneous nucleation, the effect of microwave on diffusion coefficient was reduced by microscopic particles in the solution, when nucleation is predominantly heterogeneous.

Preparation of new photo-crosslinked β-cyclodextrin polymer beads

Photo-crosslinkable groups were introduced to β-cyclodextrin (β-CyD) by the reaction of β-cyclodextrins with isophorone diisocyanate and 2-hydroxyethyl acrylate to produce polysubstituted photo-crosslinkable β-CyD (PSβCyD). To yield PSβCyD of a spherical shape, a suspension consisting of PSβCyD and aqueous sodium alginate solution was added dropwise into an aqueous calcium chloride solution. Then, the PSβCyD macromonomer was photo-crosslinked with ultraviolet radiation to obtain β-CyD polymer beads.

Governing Principles of Alginate Microparticle Synthesis with Centrifugal Forces.

A controlled synthesis of polymeric particles is becoming increasingly important because of emerging applications ranging from medical diagnostics to self-assembly. Centrifugal synthesis of hydrogel microparticles is a promising method, combining rapid particle synthesis and the ease of manufacturing with readily available laboratory equipment. This method utilizes centrifugal forces to extrude an aqueous polymer solution, sodium alginate (NaALG) through a nozzle. The extruded solution forms droplets that quickly cross-link upon contact with aqueous calcium chloride (CaCl2) solution to form hydrogel particles. The size distribution of hydrogel particles is dictated by the pinch-off behavior of the extruded solution through a balance of inertial, viscous, and surface tension stresses. We identify the parameters dictating the particle size and provide a numerical correlation predicting the average particle size. Furthermore, we create a phase map identifying different pinch-off regimes (dripping without satellites, dripping with satellites, and jetting), explaining the corresponding particle size distributions, and present scaling arguments predicting the transition between regimes. By shedding light on the underlying physics, this study enables the rational design and operation of particle synthesis by centrifugal forces.

Flexible Asymmetric Encapsulation for Dehydration-Responsive Hybrid Microfibers.

A new class of smart alginate microfibers with asymmetric oil encapsulates is introduced. These fibers are produced by injecting an aqueous alginate solution into an outer aqueous calcium chloride solution to form alginate fibers, which are asymmetrically loaded with oil entities through eccentrically aligned inner capillaries. The fiber morphology and its degree of asymmetry can be tuned via altering the size, location, and frequency of the oil encapsulates. These asymmetric fibers reveal significant potential for applications where conventional symmetric fibers fail to perform. It is shown how asymmetric oil-encapsulated fibers can become dehydration-sensitive, and trigger the release of encapsulates if their hydration level drops below a critical value. It is also shown how the triggered response could be switched off on demand by stabilizing the oil encapsulates. The capability of asymmetric fibers to carry and release multiple cargos in parallel is demonstrated. The fibers loaded with equal-sized spheres are more asymmetric than those containing unequal drops, have a higher tensile strength, and show better potential for a triggered response.

The fabrication technique for hollow gel microparticles using microbubble templates

Hollow gel microparticles with shells composed of functional polymer gels are expected to be useful in the production of food additives or anti-reflective films for liquid crystal displays. However, few studies have addressed methods for the simple and efficient production of hollow gel microparticles. Hollow gel microparticles would be expected to find widespread applications if they could be fabricated more easily. In this study, we succeeded in fabricating hollow gel microparticles simply by atomizing a gas-supersaturated aqueous sodium alginate solution into aqueous calcium chloride solution. The gas-supersaturated aqueous sodium alginate solution was prepared by gas pressurization; following a rapid pressure decrease, the excess dissolved gas appeared as microbubbles in the atomized droplets. When the atomized droplets, with encapsulated microbubbles, came into contact with the aqueous calcium chloride solution, the droplets were converted to a gel by ionic crosslinking between sodium alginate and calcium ions, and any remaining bubbles were trapped inside the droplets. With this method, we can fabricate calcium alginate hollow gel microparticles of less than 100 μm with multi-voids. Furthermore, these hollow structures can be controlled by changing the compression pressure, which changes the amount of dissolved gas in the liquid.

Tensile strengths of flocculated compacted unsaturated soils

Flocculating agents can be introduced to soils through a number of natural or anthropogenic processes. This paper investigates the effect of flocculant addition (aqueous calcium chloride (CaCl2)) on the tensile strengths of two soils of differing flocculation susceptibility. Tensile strengths were found using the Brazilian (direct splitting) test for a range of suction values. A decrease in tensile strength was found for a soil with high clay content, which was consistent with previous findings in the literature. However, the strength of the soil with lower clay content unexpectedly increased. Results were interpreted using the extended Mohr–Coulomb (EMC) yield criterion fitted to data above the residual suction value. Changes in EMC parameters were used to infer changes in material behaviour on calcium chloride addition. Results have important implications for the design of geotechnical structures, for example engineered cover systems, exposed to flocculating conditions.

Control of biomimetic hydroxyapatite deposition on polymer substrates using different protein adsorption abilities

We recently developed a system for coating polystyrene (PS) substrates with hydroxyapatite (HAp) by utilizing serum protein adsorption layers as mediators to induce the heterogeneous nucleation of HAp in simulated body fluids (SBFs). In this study, the selective deposition of HAp on polymer substrate surfaces with different protein adsorption abilities was investigated using PS and poly(methyl methacrylate) (PMMA). Atomic force microscopic observations and the results of a quantitative analysis using a quartz-crystal microbalance (QCM) revealed that the amounts of proteins such as human serum albumin (HSA) and human immunoglobulin G (hIgG) adsorbed on PS substrate surfaces were markedly greater than those on PMMA substrate surfaces. A markedly larger amount of HAp was deposited on protein-treated PS substrate surfaces than on PMMA substrate surfaces, reflecting protein adsorption to polymers. We also revealed that the deposition of HAp on protein-adsorbed PS substrate surfaces was enhanced by aqueous calcium chloride treatments before immersion in 1.5SBF. In the case of 2.5M calcium chloride treatment, these surfaces were completely covered with deposits.

Oxidative calcium release from catechol.

Oxidation of 4-methylcatechol previously exposed to aqueous calcium chloride was shown by ion chromatography to be associated with release of calcium ions. The catechol was oxidised to the corresponding orthoquinone by the use of tyrosinase from Agaricus bisporus. The oxidative release of calcium from the catechol is ascribed to the diminution of the available hydroxyl functions able to act as chelating groups. Our results suggest that the redox status of melanin may regulate calcium binding and influence calcium levels in pigmented cells.

エネルギー分散型X線回折法による高温高圧下における塩化カルシウム水溶液の構造

エネルギー分散型X線回折法による高温高圧下における塩化カルシウム水溶液の構造

Facile preparation of PLGA microspheres with diverse internal structures by modified double‐emulsion method for controlled release

Poly(l‐lactide‐co‐glycolide) (PLGA) microspheres with diverse internal structures and different release behaviors were prepared via a modified double‐emulsion method by introduction of heparin or carboxymethyl chitosan in the inner aqueous phase and calcium chloride in the outer aqueous phase, respectively. The main factors affecting the microsphere morphology were systematically studied, including compositions in the inner aqueous phase, the oily phase, and the outer aqueous phase. The transmission electron microscope images demonstrated that the microspheres are featured with single core, hollow, and multicore structures when their sizes were less than 200 nm, in the range of 200–700 nm, and greater than 700 nm, respectively. In comparison with hollow PLGA microspheres, the PLGA microspheres with heparin and carboxymethyl chitosan in the inner aqueous phase also showed multicore and single core structures, respectively, and exhibited higher loading efficiencies and slower release rates by using bovine serum albumin as a model for bioactive substances. It was concluded that this study provided a facile method to prepare microspheres with single core, multicore, or hollow feature, and the tunability of the different internal structures and related release profiles enables these systems cater to specific requirements for potential applications in controlled biomolecule delivery for tissue regeneration. POLYM. ENG. SCI., 55:896–906, 2015. © 2014 Society of Plastics Engineers

Accurate description of calcium solvation in concentrated aqueous solutions.

Calcium is one of the biologically most important ions; however, its accurate description by classical molecular dynamics simulations is complicated by strong electrostatic and polarization interactions with surroundings due to its divalent nature. Here, we explore the recently suggested approach for effectively accounting for polarization effects via ionic charge rescaling and develop a new and accurate parametrization of the calcium dication. Comparison to neutron scattering and viscosity measurements demonstrates that our model allows for an accurate description of concentrated aqueous calcium chloride solutions. The present model should find broad use in efficient and accurate modeling of calcium in aqueous environments, such as those encountered in biological and technological applications.

Antioxidant activity of fucose-containing sulfated polysaccharides obtained from Fucus evanescens by different extraction methods

The fucose-containing sulfated polysaccharides (FCSPs) from Fucus evanescens were obtained via different procedures: by hot acidic extraction and with aqueous calcium chloride solution, followed by separation FCSPs using anion-exchanging chromatography. Chemical characteristics of these polysaccharide fractions were determined. It was shown that extraction with aqueous calcium chloride solution provides a purified preparation of the FCSPs. The crude polysaccharide and its chromatography purified fractions obtained by this method have significantly lower contents of laminaran, uronic acids, and polyphenols in comparison with FCSPs obtained by hot acid extraction. All polysaccharides exhibited total antioxidant capacity and 1,1-diphenyl-2-pycrilhydrazyl (DPPH) radical-scavenging activity and low 2,2′-azino-bis 3-ethyl benzothiazoline-6-sulfuric acid (ABTS) radical-scavenging activity. A strong positive correlation between polyphenol content in FCSPs and their antioxidant activity was found. This fact may indicate that phenols play a key role in the previously described antioxidant capacity of FCSPs.

Preparation and characterization of in situ ionic cross-linked pectin films: Unique biodegradable polymers

The study aimed to investigate the swelling and degradation of calcium pectinate (CaP) films that were cross-linked by the innovative approach of adding aqueous calcium chloride (CaCl2) to pre-formed pectin films in situ. The films, cast from low methoxy pectin, were dried and cross-linked by immersion in a selected CaCl2 solution for a selected period. It was found that CaCl2 concentration, immersion time, and temperature affected the films’ dissolution and swelling behaviors in simulated intestinal fluid. With lower CaCl2 concentration, more time was needed to form a proper film. Heat accelerated the cross-linking reaction, probably by elevating the cross-linked solution flux into the matrix. Depending upon cross-linking conditions, similar calcium contents in the CaP films resulted in different swelling and degradation behaviors. The degree of pectin esterification (DE) affected the films’ degradation rate. The role of pectin molecular weight and DE on the films’ mechanical properties was determined by stress/strain analysis.

Dissolution Properties of Silk Cocoon Shells and Degummed Fibers from African Wild Silkmoths

Silk cocoon shells and degummed fibers from four African wild silkmoth species were studied and compared with the industrial standard, Bombyx mori, for their dissolution properties. Nine M aqueous Lithium bromide, Calcium chloride and Sodium thiocyanate solution systems were used. Efficiency of the solvent systems was determined by the percentage of dissolved silk cocoon shells and degummed fibers after three hours of treatment. Degummed fibers were more readily soluble than the cocoon shells. B. mori cocoon shells (51.5%) and fibers (59.3%) had higher solubility than their wild counterparts. Among the wild species, Gonometa postica cocoon shells and degummed fibers had the highest solubility (37.3 and 51.7%, respectively). Lithium bromide was the most effective dissolving agent for both the cocoon shells and fibers (41.2 and 84.5%, respectively). Argema mimosae, Anaphe panda and Epiphora bauhiniae showed lower solubility across the solution systems used. The Scanning Electron micrographs showed A. panda fibers exhibited gelling property after dissolution while E. bauhiniae and A. mimosae had cracked and broken fibers exposing the fibriliar structures. The difference in the chemical orientation and composition of the fibers might have contributed to the variability in the dissolution behaviour.

Heat and mass transfer during heating of a hybrid absorption/sensible storage tank

A numerical study of heat and mass transport in a tank of aqueous calcium chloride as heat is added to the tank is presented to evaluate the potential of storing water, diluted, and concentrated salt solutions in a single tank to provide sensible and thermochemical (sorption) storage for solar space heating and hot water. An immersed heat exchanger provides the means to sensibly charge the tank while a stable density interface between layers of different salt mass fraction minimizes mass transfer to permit long term storage. Transient simulations are presented over the wide range of conditions expected in practice, as represented in dimensionless form by the Rayleigh number (Ra), buoyancy ratio (N), geometric aspect ratio (a), Lewis number (Le) and Prandtl number (Pr). Correlations of Nusselt number (Nu) and Sherwood number (Sh) for 7×103<Ra<3.3×109, 1<N<26.4, 0.125<a<1, and 15<Le<1.5×104 are in the form Nu=0.45a0.5Ra0.28 and Sh=0.001Ra0.28N−0.69Le1.17.

Microemulsification–cold gelation of whey proteins for nanoencapsulation of date palm pit extract

Cold gelation of whey proteins is a promising method to produce biopolymeric particles entrapping heat-sensitive nutraceuticals at ambient conditions. An aqueous phase composed of heat-treated whey protein isolate (WPI), date palm pit aqueous extract powder, glucono-δ-lactone (GDL) and calcium chloride was microemulsified in a mixture of sunflower oil and sorbitan monooleate. The partial hydrolysis of GDL to gluconic acid resulted in cold gelation of whey proteins inside the nanodroplets of microemulsion which afterwards were precipitated by centrifugation. Heat-treated WPI, extract free particles and extract-loaded capsules had mean sizes of 23, 304 and 230 nm, respectively. Fourier transform infra-red spectroscopy revealed the partial conversion of Amid I band in native WPI to Amid II band in particles and capsules, as well, formation of disulfide bonds. Extract-loading donated a more spherical morphology to particles but did not influence their thermal behavior examined by differential scanning calorimetry. A controlled release character was suggested for nanoparticles based on the phenolics content measurement released from extract-loaded nanoparticles.

Buoyancy Driven Mass Transfer in a Liquid Desiccant Storage Tank

A new concept for long-term solar thermal storage is based on the absorption properties of aqueous calcium chloride. Water, diluted and concentrated calcium chloride solutions are stored in a single tank. An immersed heat exchanger and stratification manifold are used to preserve long-term sorption storage, and to achieve thermal stratification. The feasibility of sensible heating the tank via large-scale natural convection without mixing salt solutions is demonstrated via measurements of velocity, CaCl2 mass fraction, and temperature in a 1500 l prototype tank. Experiments are conducted over a practical range of the relevant dimensionless parameters. For Rayleigh numbers from 3.4 × 108 to 5.6 × 1010 and buoyancy ratios from 0.8 to 46.2, measured Sherwood numbers are 11 ± 2 to 62 ± 9, and the tank is thermally stratified. Convective mixing between salt layers is inhibited by the presence of a steep density gradient at the interface between regions of differing mass fraction. The predicted storage time scales based on mixing via natural convection for the reported Sherwood numbers are 160–902 days.

Bioactive dentin replacement

Replacement of dentin with a material popularly marketed as Biodentine (Septodont, Saint Maur des Fausses, France), a new tricalcium silicate-based cement, has recently been commercialized and advertised as a bioactive material. Its clinical application and physical properties have been widely described. Biodentine, a new biologically active cement which has dentin-like mechanical properties and can be used as a dentin replacement in the tooth crown and root region. The cement consists mainly of a tri- and dicalcium silicate powder, which is mixed with an aqueous calcium chloride solution. As regards biocompatibility, long- term impermeability, antibacterial properties, induction of hard tissue regeneration, stability, low solubility, non-absorbability and ease of handling, Biodentine fulfils the requirements found in the literature for a material suitable for these purposes. On the basis of the good material properties of Biodentine, this cement is an interesting alternative to the conventional materials which were hitherto recommended. Biodentine can therefore confer advantages in day-to-day practice and with correct diagnosis contribute to the long-term maintenance of the vitality of the dental pulp and to the retention of teeth. However, little scientific data is available at present.