Source Of Calcium Ions Research Articles

Formation of Membrane Tubular Protrusions upon Localized Application of Calcium Ions to the Surface of Giant Lipid Vesicles

We present a study on the formation of lipid nanotubular protrusions as a result of localized application of calcium ions to the membrane of giant lipid vesicles. Our findings demonstrate that a point source of calcium ions acting upon a negatively charged membrane generates spontaneous curvature sufficient to induce membrane bending and the formation of nanotubular protrusions. The observed membrane behaviour can be explained as the response to the trans-bilayer mismatch of surface charge density upon calcium ion binding from the exposed side of the bilayer. By using molecular dynamics simulations, we validate this experimental observation, finding that calcium ion binding to a lipid membrane is sufficient to generate spontaneous curvature, bending the membrane away from the ion source. The observed calcium-ion guided tubulation in lipid membranes can be a significant step towards gaining insights into cell membrane re-shaping in response to chemical stimulation, and can further our understanding of the fundamental mechanisms by which lipids redistribute within cell membranes.

The effect of concentration and source of calcium ions on anticorrosion properties of Ca-doped TiO2 bioactive sol-gel coatings

Abstract Titanium dioxide (TiO 2 ) coating with an enhanced anticorrosion properties and bioactivity was developed by doping it with calcium ions through a sol–gel method. The effect of annealing temperature, anions, as well as calcium ions concentration on microstructural and anticorrosion properties of Ca-doped TiO 2 coatings have been investigated. The phase composition and morphology of the coatings were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The corrosion resistance of M30NW biomedical alloy coated with Ca-doped TiO 2 coatings was evaluated using electrochemical methods in conditions similar to the normal physiological environments (PBS solution, pH 7.4, temperature of 37 °C). The obtained results show that the annealing temperature and the source of calcium ions influence the anticorrosion properties of Ca-doped TiO 2 coatings. The best anticorrosion properties were registered for coatings with the highest concentration of Ca ions. At the same time all the examined coatings presented good bioactivity in SBF solution test.

Effect of process parameters on the CaCO3 production in the single process for carbon capture and mineralization

The regeneration of the CO2 capture system is the most energy-intensive process associated with CO2 capture because high temperatures are required to desorb CO2 from the absorbent. We propose a single process for effective CO2 capture and mineralization as a substitute for desorption of absorbed CO2, producing high value-added CaCO3. A saturated 2-amino-2-methyl-1-propanol (AMP) solution was used as a carbonate source, and calcium chloride (CaCl2) was used as a calcium ion source to precipitate CaCO3. A semi-batch reactor was used to investigate the effects of the mixing rate, temperature, and amount of calcium added during the CaCO3 precipitation process. During the mineralization reaction, the absorbed CO2 in AMP solution instantly converted into white CaCO3 precipitant with 97.4% conversion. The stirring rate provided a reciprocal effect on the crystal size, whereas the temperature and Ca/CO2 molar ratio appeared to affect the crystal morphology.

Ostrich Eggshell as an Alternative Source of Calcium Ions for Biomaterials Synthesis

Ostrich eggshells are a potentially abundant and a high purity and low cost source of calcium to produce β-Tricalcium Phosphate (β-TCP) and Hydroxyapatite (HA), important calcium phosphates used as biomaterials. Here, we use a wet precipitation procedure to synthesize these phosphates using ostrich eggshells as a source of calcium ions. The biphasic precipitated powder, calcined at 800oC, is a mixture of both Hydroxyapatite and β-Tricalcium Phosphate, also known as the biomaterial Biphasic Calcium Phosphate (BCP). Physico-chemical properties of the final powder product show water and CO32- groups absorbed in the particles surface, 0.1 to 100 µm particles size distribution and 11.70 m2/g of specific surface area.

Short-term effects on physical properties of lime treated kaolin

In the paper an experimental multi-scale investigation on the influence of pore water chemistry on the short-term behaviour of lime treated soil is presented. Sedimentation tests on kaolin suspensions under different chemical environment have been performed and interpreted, taking into account the effects of clay particles interactions on the soil skeleton formation. The experimental evidences at volume scale of the samples have been directly related to the results of micro-scale investigations. Modification of surface charge and its influence on soil fabric has been investigated by means of zeta-potential measurements, Dynamic Light Scattering (DLS) and Scanning Electron Microscopy (SEM). The effects of lime content, cation valence and source of calcium ions on the surface charge of kaolin particles have been considered. The addition of lime increased the average size of particles aggregates in the short term. The fabric evolution affected the formation of the soil skeleton during sedimentation, influencing its void ratio and compressibility, highlighting the link between microstructural features and mechanical behaviour of lime treated samples.

Sol–gel synthesis, phase composition, morphological and structural characterization of Ca10(PO4)6(OH)2: XRD, FTIR, SEM, 3D SEM and solid-state NMR studies

Aqueous sol–gel chemistry route based on ammonium–hydrogen phosphate as the phosphorus precursor, calcium acetate monohydrate as source of calcium ions, and 1,2-ethylendiaminetetraacetic acid (EDTA), or 1,2-diaminocyclohexanetetracetic acid (DCTA), or tartaric acid (TA), or ethylene glycol (EG), or glycerol (GL) as complexing agents have been used to prepare calcium hydroxyapatite (Ca10(PO4)6(OH)2, CHAp). The phase transformations, composition, and structural changes in the polycrystalline samples were studied by infrared spectroscopy (FTIR), X-ray powder diffraction analysis (XRD), and scanning electron microscopy (SEM). The local short-range (nano- and mezo-) scale effects in CHAp were studied using solid-state NMR spectroscopy. The spatial 3D data from the SEM images of CHAp samples obtained by TA, EG and GL sol–gel routes were recovered for the first time to our knowledge.

Environmental parameters conditioning microbially induced mineralization under the experimental model conditions.

Microbially induced calcium carbonate precipitation is one of the biomineralization types closely dependent on the parameters of the microenvironment. Minerals are precipitated as a product of environmental and bacterial cell interactions, however, this system has very little control via microorganisms. The aim of research was to determine the influence of abiotic factors (pH, temperature, agitation speed of bacterial culture and calcium ion source) on the mineralization induced by Arthrobacter sulfureus, Bacillus muralis and B. atrophaeus strains under the standard laboratory conditions. Because of the key role of urease in biomineralization, processes occurring in environments with and without the urea were compared. For this purpose, cultivation of bacteria (A. sulfureus, B. muralis and B. atrophaeus) was carried out in B4 liquid medium for 5 days with various environmental parameters (pH 6-9; temperature 25-44°C; speed of agitation 0-180 rpm, different calcium sources). It was noticed that the pH and the speed of agitation clearly affect the amount of the calcium carbonate that formed. Our observations suggest that the highest precipitation rate takes place in alkaline pH between 8-9, with shaking at 180 rpms. Among studied sources of calcium ions (calcium acetate, calcium chloride and calcium nitrate), calcium acetate demonstrated the strongest potential in the biomineralization process. Moreover, work presented here demonstrates that the correlation between cultivation temperature and biomineralization process cannot be clearly evaluated. The morphology and size of calcium carbonate minerals was strain-specific, although affected by the presence of urea in the surrounding solution.

Conservation of minimally processed apples using edible coatings made of turnip extract and xanthan gum

Summary The objective of this study was to evaluate the potential of turnip extract and xanthan gum in the conservation of minimally processed apples. The apples were washed, sanitized with sodium hypochlorite (200 ppm) for 15 minutes, peeled, and cut into eight pieces prior to being subjected to one of the following treatments in aqueous solution: A – water (control); B – turnip extract; C – turnip extract and CaCl2; D – xanthan gum, CaCl2 and glycerol; E – turnip extract, xanthan gum, CaCl2, and glycerol. Subsequently, the freshly cut apples were dried under ventilation on nylon screens to ensure drying of the coatings, and then packed in polystyrene trays, covered with polyvinylchloride films and stored at 4 ± 1 ° C for 13 days. The following parameters were evaluated: mass loss, firmness, colouration, pH value, soluble solids, and peroxidase/polyphenoloxidase activities. The edible coatings were found to be ineffective with respect to controlling mass loss, but the minimally processed apples coated with turnip extract maintained their initial levels of colouration, firmness and pH value. A considerable increase in peroxidase activity was registered for apples treated with turnip extract, suggesting that this effect may also be responsible for the reduction in browning. No advantage could be observed for the simultaneous presence of turnip extract and xanthan gum or calcium chloride. The turnip extract may represent an interesting alternative for applications to minimally processed apples, especially as it is a natural product, easily obtained, cost effective and contributes to the nutritional quality (e.g. as a source of calcium ions).

Development of the Neuron-Electrode Interfaced Network Using Dynamic Substrate Based on Alginate Hydrogel

Event Abstract Back to Event Development of the Neuron-Electrode Interfaced Network Using Dynamic Substrate Based on Alginate Hydrogel Sunghoon Joo1, Seukyoung Song2, Yoon S. Nam2 and Yoonkey Nam1* 1 Korea Advanced Institute of Science and Technology, Department of Bio and Brain Engineering, Korea 2 Korea Advanced Institute of Science and Technology, Department of Materials Science and Engineering, Korea Motivation To study the signal processing such as learning and memory between neurons in network scale, In vitro neural network have been used as a powerful and controllable model system. However, the neural network without any control of cell-positioning and axon-guidance is too complicate to figure out the structure of the network. To reduce the limitation of randomly positioned neural network, neuron patterning techniques based on microfabrication, material engineering, and chemical engineering have recently been developed and applied on the MEA substrate [1]. In this study, we selectively control the cell adhesiveness of MEA surface using alginate hydrogel. Using this method, we can design the neural network where neurons are positioned precisely on the electrodes of MEA and the clusters of neurons are freely connected. Material and Methods Polydimethoxysiloxane (PDMS) molds were manufactured by soft-lithography. The mold was placed on the poly-D-lysine coated MEA (MultiChannel Systems, Germany), and 0.1% (w/v) alginate solution was applied to the mold. Calcium ion source, 1% CaCl2, was treated for gelation of alginate solution by ionic cross-linking. After the removal of PDMS mold, neuronal cells were seeded onto the pattern. The alginate hydrogel background could be dissolved by the addition of 10 mM Na2CO3 to remove calcium ion which cross-linked alginate hydrogel at 4 DIV. Results Figure 1a shows that the connection of the neuronal network after removal of the alginate hydrogel from the MEA. Before the removal of the alginate, neurons on each electrode were separated due to the cell repulsive nature of alginate hydrogel. The alginate hydrogel background was dissolved by the treatment of 10 mM Na2CO3 at 4 DIV. After a few days, the cell body of neurons were located only on the electrodes, but the neurons were connected by neurites. From the networks, electrical signals were successfully measured by neural signal amplifier (Gain: 1100, bandwidth: 10 Hz ~ 5 kHz, MultiChannel Systems) at 15 DIV (11 days after the removal of alginate) as provided in Figure 1b. Discussion Our designing method to make neuron-electrode interfaced network has many advantages. A biocompatible material, alginate hydrogel, was used to control the cell adhesiveness on MEA substrate. The alginate background can be easily removed by the treatment of Na2CO3 solution. Because of neuron-electrode interfacing of our neuronal network, the measurement of electrical activity could be enhanced compared to the randomly positioned neural network. Conclusion In this work, we suggest a simple, but effective method to pattern the primary neural network where neurons were patterned on electrodes and each cluster of neurons were freely connected using dynamic substrate based on alginate hydrogel. Using the MEA system, we recorded the electrical activity from the patterned neuronal network.

Chitosan-based hydrogel implants enriched with calcium ions intended for peripheral nervous tissue regeneration

A new method for fabrication of chitosan-based hydrogel implants intended for peripheral nervous tissue regeneration was developed. The method is based on an electrodeposition phenomenon from a solution of chitosan and organic acid. In order to increase the mechanical strength of the implant, the solution was enriched with hydroxyapatite. Hydroxyapatite served as a source of calcium ions too. The influence of the concentration of the polymer and the additive on chemical, mechanical as well as biological properties of the obtained implant was evaluated. The study showed great dependence of the initial solution composition mainly on the physicochemical properties of the resulting structure. Basic in vitro cytotoxic and pro-inflammatory assays showed biocompatibility of manufactured implants, therefore, animal experimentations may be considered.

In-situ assembly of Ca-alginate gels with controlled pore loading/release capability.

Development of tailor-made porous polymer scaffolds acting as a temporary tissue-construct for cellular organization is of primary importance for tissue engineering applications. Control over the gel porosity is a critical issue due to the need for cells to proliferate and migrate and to ensure the transport of nutrition and metabolites. Gel loading with bioactive molecules is desired for target release of soluble signals to guide cell function. Calcium-alginate hydrogels are one of the most popular gels successfully utilized as polymer scaffolds. Here we propose a benchtop approach to design porous alginate gels by dispersion of CaCO3 vaterite crystals in sodium alginate followed by the crystal elimination. CaCO3 crystals play a triple role being (i) cross-linkers (a source of calcium ions to cross-link gel network), (ii) pore-makers (leaching of crystals retains the empty pores), and (iii) reservoirs with (bio)molecules (by molecule preloading into the crystals). Pore dimensions, interconnectivity, and density can be adjusted by choosing the size, concentration, and packing of the sacrificial CaCO3 crystals. An opportunity to load the pores with biomolecules was demonstrated using FITC-labeled dextrans of different molecular masses from 10 to 500 kDa. The dextrans were preloaded into CaCO3 vaterite crystals, and the subsequent crystal removal resulted in encapsulation of dextrans inside the pores of the gel. The dextran release rate from the gel pores depends on the equilibration of the gel structure as concluded by comparing dextran release kinetics during gelation (fast) and dextran diffusion into the performed gel (slower). Macromolecule binding to the gel is electrostatically driven as found for lysozyme and insulin. The application of porous gels as scaffolds potentially offering biomacromolecule encapsulation/release performance might be useful for alginate gel-based applications such as tissue engineering.

Biomimetic Sequestration of CO2 Using Carbonic Anhydrase from Calcite Encrust Forming Marine Actinomycetes

Background: CO2 in the environment has been a burning issue and aggravated the threats of global warming. Various strategies are being used to decrease the level of releasing CO 2 . Biosequestration is a one of the available nontoxic, robust and eco-friendly approaches but still less evaluated. This study reports the role of microbial Carbonic Anhydrase (CA) in the formation of calcite by utilizing CO2. Methods: The marine Nocardiopsis lucentensis was studied for intracellular microbial CA. Isolate grown optimally at 2.5% CO2 saturated environment and procedure the calcium carbonate encrust in the presence of CaCl2. Results: The enzyme was found to catalyze the reaction in a wide range of pH and temperature with an optimum at 7.0 pH and 25°C. The 50 mM NaCl, KCl and MgCl2 were found to support the enzyme activity and 50 mM ZnCl 2 increases activity 1.5 fold. CA was able to withstand against sulphanilamide inhibitor and stable over prolonged incubation at 4 and 37°C. Conclusion: Calcite formation was evaluated with and without enzyme using marine water as a source of calcium ions. The result of SEM and EDX indicated the formation of larger flower-shaped particles compare to the small cubic particles formed without enzyme. The results suggest that the robustness of enzyme and suitability in the CO2 capture reactor.

Leaching kinetics of bottom ash waste as a source of calcium ions

Bottom ash is a waste material from coal-fired power plants, and it is known to contain elements that are potentially toxic at high concentration levels when disposed in landfills. This study investigates the use of bottom ash as a partial substitute sorbent for wet flue gas desulfurization (FGD) processes by focusing on its leaching kinetics in adipic acid. This was studied basing on the shrinking core model that was applied to the experimental data obtained by the authors presented at the International Conference on Industrial, Manufacturing, Automation and Mechanical Engineering, Johannesburg, South Africa, November 27–28, 2013) on dissolution of bottom ash. The leaching rate constant was obtained from different reaction variables, namely, temperature, pH, acid concentration, and solid-to-liquid ratio, that could affect the leaching process. The solid sample of bottom ash was characterized at different leaching periods using X-ray diffraction (XRD) and scanning electron microscopy (SEM). It was found that solid-to-liquid ratio had a significant effect on the leaching rate constant when compared with other variables. The leaching kinetics showed that diffusion through the product layer was the rate-controlling step during leaching, and the activation energy for the process was found to be 18.92 kJ/mol.Implications: The use of coal bottom ash waste as a sorbent substitute in wet flue gas desulfurization (FGD) has both economic and environmental advantages. This is because it is a waste from coal-fired thermal power plant and this study has proven that it can leach out a substantial amount of calcium ions for wet FGD process. This will abate anthropogenic pollution due to landfill disposal of bottom ash wastes and also reduce sulfur dioxide emissions.

Appraisal of gastropod shell as calcium ion source for phosphate removal and recovery in calcium phosphate minerals crystallization procedure

On the basis of the perspective of wastes recycling and minimization of cost of phosphate removal via the chemical precipitation procedure, the present studies evaluated the ability of waste biogenic Gastropod shell to serve as a source of Ca2+ ion in the removal and recovery of phosphate in calcium phosphate mineral (CPM) crystallization procedure. Phosphate removal efficiency values >99% was achieved when 2g of snail shell was used in water of phosphate concentrations ranging between 25 and 1000mg/L. pH and ionic strength exhibited no influence on the phosphate removal efficiency. Concomitant removal of phosphate and organic matter revealed that phosphate removal efficiency was not impacted but the magnitude of the organics removed increased with increase in the organic load. Kinetic analysis showed that second order kinetic model gave a better description of the process. XRD analysis of the derived sludge showed the crystallinity and peaks synonymous with the presence of whitlockite, hydroxyapatite and calcium phosphate hydrate. The FTIR of the sludge showed the disappearance of some naturally occurring functional groups and the appearance of phosphate peaks which confirmed the formation of CPM.

Biomineralizations: insights and prospects from crustaceans

For growing, crustaceans have to molt cyclically because of the presence of a rigid exoskeleton. Most of the crustaceans harden their cuticle not only by sclerotization, like all the arthropods, but also by calcification. All the physiology of crustaceans, including the calcification process, is then linked to molting cycles. This means for these animals to find regularly a source of calcium ions quickly available just after ecdysis. The sources of calcium used are diverse, ranging from the environment where the animals live to endogenous calcium deposits cyclically elaborated by some of them. As a result, crustaceans are submitted to an important and energetically demanding calcium turnover throughout their life. The mineralization process occurs by precipitation of calcium carbonate within an organic matrix network of chitin-proteins fibers. Both crystalline and stabilized amorphous polymorphs of calcium carbonate are found in crustacean biominerals. Furthermore, Crustacea is the only phylum of animals able to elaborate and resorb periodically calcified structures. Notably for these two previous reasons, crustaceans are more and more extensively studied and considered as models of choice in the biomineralization research area.

Change in Ca2+-responses of cultivated brown adipocytes at adrenergic activation

The thermogenic capability of brown adipose tissue is controlled by noradrenaline. By interacting with α1- and β-adrenoreceptors of adipocytes, noradrenaline (NA) increases the intracellular concentration of Ca2+ ([Ca2+]i) and cAMP. The changes in [Ca2+]i under the action of NA and selective agonists of α1- and β-adrenoreceptors, i.e., cirazoline and isoproterenol (IP), are recorded on individual cells of the primary culture of adipocytes during the day in vitro (DIV) 1, DIV 3, and DIV 6. The change in [Ca2+]i under the effect of IP as compared to the response to cirazoline in cells of DIV 1 is characterized by a higher amplitude and shorter duration of impulses in the entire diapason of the used physiological concentrations. After DIV 3, these differences are insignificant and, after DIV 6, the differences in kinetics are nearly absent. For all three agonists, the kinetics of the [Ca2+]i change in the proliferating and differentiated cells is significantly different; i.e., the response amplitude increases with the age of the culture and the duration of transitory response decreases, while sensitivity to agonists of adrenoreceptors increases. It can be seen from the rise in [Ca2+]i with an inhibitor of Ca2+-ATPase of the endoplasmic reticulum thapsigargin in calcium-free medium that the source of calcium ions in the endoplasmic reticulum rises with the growth and development of cells in culture, while the rate at which Ca2+ is pumped out of cells, which characterizes the activity of Ca2+-ATPase of the plasma membrane, increases.

A New Coagulant for Spilled Oil Removal with Bentonite and Calcium Chlorine and Sawdust

A new coagulant for spilled oil with bentonite and CaCl2 and sawdust has been done in our lab. The experiment indicates that bentonite is a good coagulant, especilly accompany with CaCl2 and sawdust. The function of bentonite is coagulation, adsorption and emulsification. CaCl2 is a good coagulant-mate, and strengthen the coagulating function of bentonite. It can be used as the source of calcium ions, which can strongly adsorb on both bentonite and oil droplets, and is helpful for the coagulation between bentonite and oil droplets. Sawdust is also very important, its function is buoyant, bridge-made and adsorbent.

The Forming Mechanism of a New Oil-Mineral Aggregate

A new Oil-Mineral Aggregate with bentonite and calsium hydroxide and sawdust has been done. Through several dozens of experiments, the coagulation efficiency with bentonite and Ca(OH)2 and sawdust is 94.53%. The functions of bentonite are coagulation, adsorption and emulsification. Calsium hydroxide is a good coagulant-mate, and strengthen the coagulating function of bentonite. It can be used as the source of calcium ions, which can strongly adsorb on both bentonite and oil droplets, and is helpful for the coagulation between bentonite and oil droplets. Sawdust is also very important in the OMA, its fouctions are buoyant, bridge-made and adsorbant.

PH impact on the sol-gel preparation of calcium hydroxyapatite, Ca10(PO4)6(OH)2, using a novel complexing agent, DCTA

Abstract Aqueous sol-gel chemistry routes — based on ammonium hydrogen phosphate as the phosphorus precursor, calcium acetate monohydrate as the source of calcium ions, and 1,2-diaminocyclohexanetetraacetic acid monohydrate (DCTA) as the complexing agent — have been used to prepare calcium hydroxyapatite (HA). The sol-gel process was performed in aqueous solution at different pH values followed by calcination of the dry precursor gels for 5 h at 1000°C. Phase transformations, composition, and structural changes in the polycrystalline samples were studied by thermoanalytical methods (TG/DTA), infrared spectroscopy (IR), X-ray powder diffraction analysis (XRD), and scanning electron microscopy (SEM). It was shown that pH adjustment has significant impact on the apatite formation process and on the morphology and phase purity of the ceramic samples.

Growth of calcium carbonate mediated by slowly released alginate

The presence of additives has demonstrated strong effects on the crystallization and morphology of calcium carbonate (CaCO3). To understand the mediating function of alginate on the growth of CaCO3, we design a novel method to add alginate molecules and inorganic ions mildly and continuously to the mineralization system: a Ca-alginate gel is used as a slow-releasing source of calcium ions and alginate molecules; the gel is gradually broken down by the diffusion of CO2 to the solution, inducing the slow release of Ca2+ and alginate molecules. The slowly released alginate is involved in the nucleation and growth of CaCO3, in the form of micro-sized lens-like particles with a vaterite polymorph and composed of fused nanoparticles. With the increasing reaction time, the lens-like CaCO3 particles gradually develop into a hollow structure and finally turn into ring-shaped CaCO3, in which the polymorph of CaCO3 remains vaterite. The formation of the lens-like particles is the result of the partially-oriented aggregation of primary nanoparticles mediated by alginate. The further evolution of the morphology to ring-shaped particles is due to a dissolution–recrystallization process as well as Ostward ripening.