Aqueous solubility of calcium L-lactate, calcium D-gluconate, and calcium D-lactobionate: importance of complex formation for solubility increase by hydroxycarboxylate mixtures

Multifaceted Applications of Ferritin Nanocages in Delivering Metal Ions, Bioactive Compounds, and Enzymes: A Comprehensive Review

Ferritin, a distinctive iron-storage protein, possesses a unique cage-like nanoscale structure that enables it to encapsulate and deliver a wide range of biomolecules. Recent advances prove that ferritin can serve as an efficient 8 nm diameter carrier for various bioinorganic nutrients, such as minerals, bioactive polyphenols, and enzymes. This review offers a comprehensive summary of ferritin's structural features from different sources and emphasizes its functions in iron supplementation, calcium delivery, single- and coencapsulation of polyphenols, and enzyme package. Additionally, the influence of innovative food processing technologies, including manothermosonication, pulsed electric field, and atmospheric cold plasma, on the structure and function of ferritin are examined. Furthermore, the limitations and prospects of ferritin in food and nutritional applications are discussed. The exploration of ferritin as a multifunctional protein with the capacity to load various biomolecules is crucial to fully harnessing its potential in food applications.

Concentration and pH effect on the electronic circular dichroism and anisotropy spectra of aqueous solutions of glyceric acid calcium salt

Electronic circular dichroism (ECD) and anisotropy spectra carry information on differential absorption of left- and right-circularly polarized light (LCPL and RCPL) by optically active compounds. This makes them powerful tools for the rapid determination of enantiomeric excesses (ee) in asymmetric synthetic and pharmaceutical chemistry, as well as for predicting the ee inducible by ultraviolet (UV) CPL. The ECD response of a chiral molecule is, however, critically dependent on the properties of the surrounding medium. Here, we report on the first ECD/anisotropy spectra of aqueous solutions of the calcium salt dihydrate of glyceric acid. A systematic study of the effect of the salt concentration and pH on the chiroptical response revealed significant changes and the appearance of a new ECD band of opposite sign. Based on the literature, this can be rationalized by the increase in the relative proportion of free glyceric acid/glycerate to Ca²⁺ complexes with glycerate with decreasing salt concentration or pH. Glyceric acid can be readily produced under astrophysical conditions. The anisotropy spectra of the solution containing prevalently the free form of this dihydroxy carboxylic acid resemble the ones of previously investigated aliphatic chain hydroxycarboxylic acids and proteinogenic amino acids. This indicates possible common handedness of stellar CPL-induced asymmetry in the potential comonomers of primitive proto-peptides.

Fabrication of a ferritin-casein phosphopeptide-calcium shell-core composite as a novel calcium delivery strategy

Plant ferritin has a natural cage-like nanospace for carrying bioactive ingredients. By taking advantage of the calcium binding ability of casein phosphopeptide (CPP) and the cage-like conformation of plant ferritin, a ferritin-CPP shell-core complex (FC) was fabricated with the reversible self-assembly character of ferritin induced by a pH 2.0/7.0 transition strategy. The FC-calcium composite (FCC) was further fabricated by binding of the FC with calcium ions. When the same amount of calcium was loaded, the calcium binding capacity of the FCC was 28.13 ± 1.65%, which was significantly higher than that of ferritin and CPP alone. Fluorescence and Fourier transform infrared analysis indicated that the CPP encapsulation and the calcium binding in the FCC influenced the ferritin structure. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) results showed that the spherical morphology and the 12 nm-diameter size were sustained in the FC and FCC. Moreover, the FCC as a transport carrier could increase the precipitation time of calcium phosphate, and the encapsulated calcium could be released in a more sustained manner as compared with ferritin and CPP under simulated in vitro gastrointestinal conditions. This study presents a novel calcium delivery strategy based on the ferritin cage and CPP, which will improve the applicability of ferritin and CPP and enhance the bioavailability of calcium ions.

Slow lactate gluconate exchange in calcium complexes during precipitation from supersaturated aqueous solutions

Saturated solutions of calcium l-lactate in water or in deuterium oxide continuously dissolve calcium l-lactate by addition of solid sodium d-gluconate and become strongly supersaturated in calcium d-gluconate due to no or slow precipitation. The quantification of total dissolved calcium allied with the calcium complexes equilibrium constants allowed an ion speciation, which shows an initial non-thermal and spontaneous supersaturation of more than a factor of 50 at 25 °C only slowly decreasing after initiation of precipitation of calcium d-gluconate after a lag phase of several hours. A mathematical model is proposed, based on numerical solution of coupled differential equations of dynamics of l-lactate and d-gluconate exchange during the lag phase for precipitation and during precipitation. A slow exchange of l-lactate coordinated to calcium with d-gluconate is indicated with a time constant of 0.20 h^-1 in water and of 0.15 h^-1 in deuterium oxide and a kinetic deuterium/hydrogen isotope effect of 1.25. Such spontaneous non-thermal supersaturation and slow ligand exchange with a pseudo first order equilibration process with a half-life of 3.5 h in water for calcium hydroxycarboxylates can help to understand the higher calcium bioavailability from calcium hydroxycarboxylates compared to simple salts.

Exploring the solid-state phases and thermodynamics of calcium l-lactate

Calcium l-lactate, an organic salt derived from l-lactic acid, is used in many fields such as food, pharmaceutical or cosmetic industry. To this date, its solid-state thermodynamics are still poorly understood: a pentahydrate crystalline and anhydrate amorphous forms were already characterized, and potential other hydrates mentioned in literature. For the development of a robust crystallization process or down-line handling of this compound, it is important to know and understand the relationship between the different solid forms to prevent uncontrolled crystallization or solid-solid transformation during storage. In this paper, we aimed at identifying and characterizing novel solid forms of calcium l-lactate. Combining analytical techniques, we confirmed the existence of the pentahydrate and an amorphous anhydrate. In addition, we played on temperature and relative humidity conditions to discover three new crystalline forms (a crystalline anhydrate, monohydrate and dihydrate). This paper is the first occasion where these forms were successfully isolated and characterized.

CaCO3 nanoparticles pH-sensitively induce blood coagulation as a potential strategy for starving tumor therapy

Based on the concept of starving tumor therapy, in this study we put forward a new idea that the pH-sensitive Ca²⁺ delivery of calcium carbonate nanoparticles (CaCO₃ NPs) induced blood coagulation of tumor vessels, and first explored the effect of CaCO₃ NPs on the in vitro and in vivo blood coagulation by acid stimulus. CaCO₃ NPs with a size of about 100 nm and a porous structure of several nanometers were synthesized in an emulsion system, which showed a high loading capacity (49%) of doxorubicin hydrochloride (DOX) with an encapsulation efficiency of 98% and a pH-sensitive drug delivery. The hemolysis test showed that CaCO₃ NPs were blood compatible. The in vitro Ca²⁺ delivery and blood clotting tests indicated that CaCO₃ NPs pH-sensitively released Ca²⁺, and caused rapid blood coagulation at pH 5.0 but no thrombus at pH 7.4. Confocal laser scanning microscopy showed that after uptake by MCF-7 or MDA-MB-231 breast cancer cells, CaCO₃ NPs mainly distributed in endosomes/lysosomes within the initial 2 h and then decomposed by acid stimulus, leading to the intracellular delivery of Ca²⁺ that subsequently migrated outside the cells. CaCO₃ NPs were nontoxic to NIH3T3 mouse fibroblasts, but highly toxic to both MCF-7 and MDA-MB-231 cells after loading DOX. After topical administration into the breast tumors of mice, CaCO₃ NPs evoked significant thrombosis and hemorrhage of tumor vasculature by hematoxylin-eosin and Masson's trichrome staining. These results indicated that CaCO₃ NPs could induce blood coagulation via acid stimulus, showing potential applications in blocking tumor vessels for starving tumor therapy.

In Vitro Calcification of Bioprosthetic Heart Valves: Investigation of Test Fluids

Calcification is a major reason for the failure of bioprosthetic heart valves. Therefore, several attempts towards an accelerated in vitro model were undertaken in order to provide a cost- and time-saving method for the analysis of calcification processes. Due to the problem of superficial or spontaneous precipitation, which occurred in the fluids applied, we focused our study on the development of a near-physiological calcification fluid. The desired fluid should not precipitate spontaneously and should neither promote nor inhibit calcification. Eleven different fluid compositions were tested without contact to potentially calcifying materials. Crucial factors regarding the fluid properties were the ionic product, the ionic strength, and the degree of supersaturation concerning dicalciumphosphate-dihydrate, octacalciumphosphate, and hydroxyapatite. The fluids were kept in polyethylene bottles and exposed to a slight vibration within a durability tester at 37 °C. The precipitation propensity was monitored optically and colorimetrically. A structural analysis of the deposits was carried out by x-ray powder diffraction and IR-spectroscopy, which showed the development of the crystal phases that are relevant in vivo. Only two of the fluids did not precipitate. Resulting from the computations of the effective fluid contents, the saturation degree concerning dicalciumphosphate-dihydrate seems to be the key factor for spontaneous precipitation.

Bioaccessibility study of calcium and vitamin D3 co-microencapsulated in water-in-oil-in-water double emulsions

Calcium and vitamin D₃ were co-encapsulated in three types of water-in-oil-in-water (W/O/W) double emulsions stabilized with biopolymers: gum arabic, sodium alginate (Alg) and chitosan (Ch). Three calcium salts with different solubility were used: calcium carbonate (CaC), tricalcium phosphate (CaP) and calcium gluconate (CaG). In order to study the bioavailability of calcium and vitamin D₃, the W/O/W double emulsions were subjected to digestion in simulated conditions using in vitro gastrointestinal models. The size of the oil droplets of all double emulsions increased in oral phase and decreased in gastric and intestinal phases. In the intestinal phase, the average diameter of oil globules in the W/O/W(Alg) and W/O/W(Ch) was d₂₃ = 6.56 ± 0.09 and d₂₃ = 5.33 ± 0.01 and the electro-kinetic potential was: ζ ≈ -25 mV and ζ ≈ -17 mV, respectively. Presence of calcium ions in the intestinal fluid decreased the free fatty acids content and decreased the bioaccessibility of vitamin D₃ due to the inhibition of micellization process.

Preparation of a fermentation solution of grass fish bones and its calcium bioavailability in rats

In this study, with grass fish bones as the substrate, after flavourzyme treatment, and fermentation with Leuconostoc mesenteroides, a fermentation solution with a high content of soluble calcium was obtained. High performance liquid chromatography and GC-MS analysis indicated that free calcium (11.29 mmol L-1) in the fermentation solution was composed of calcium lactate (3.89 mmol L-1), calcium acetate (6.21 mmol L-1), calcium amino acids and small peptide calcium. Animal experiments show that the fermentation solution of grass fish bones could promote the growth and development of calcium-deficient rats. Complex organic calcium could be well absorbed and utilized by rats so that serum calcium, alkaline phosphatase levels, femur weight and other indicators in calcium-deficient rats could be returned to normal levels. The fermentation solution of grass fish bones can avoid the waste of aquatic proteins and fish bone calcium, and it exhibited high calcium bioavailability. Therefore, the fermentation solution of grass fish bones might be used as a new efficient calcium supplement.

The effect of respiration buffer composition on mitochondrial metabolism and function

Functional studies on isolated mitochondria critically rely on the right choice of respiration buffer. Differences in buffer composition can lead to dramatically different respiration rates leading to difficulties in comparing prior studies. The ideal buffer facilities high ADP-stimulated respiratory rates and minimizes substrate transport effects so that the ability to distinguish between various treatments and conditions is maximal. In this study, we analyzed a variety of respiration buffers and substrate combinations to determine the optimal conditions to support mitochondrial function through ADP-stimulated respiration and uncoupled respiration using FCCP. The buffers consisted of a standard KCl based buffer (B1) and three modified buffers with chloride replaced by the K-lactobionate, sucrose, and the antioxidant taurine (B2) or K-gluconate (B3). The fourth buffer (B4) was identical to B2 except that K-lactobionate was replaced with K-gluconate. The substrate combinations consisted of metabolites that utilize different pathways of mitochondrial metabolism. To test mitochondrial function, we used isolated cardiac guinea pig mitochondria and measured oxygen consumption for three respiratory states using an Oroboros Oxygraph-2k. These states were the leak state (energized mitochondria in the absence of adenylates), ADP-stimulated state (energized mitochondria in the presence of saturating ADP concentrations), and uncoupled state (energized mitochondria in the presence of FCCP). On average across all substrate combinations, buffers B2, B3, and B4 had an increase of 16%, 26%, and 35% for the leak state, ADP-simulated state, and uncoupled state, respectively, relative to rates using B1. The common feature distinguishing these buffers from B1 is the notable lack of high chloride concentrations. Based on the respiratory rate metrics obtained with the substrate combinations, we conclude that the adenine nucleotide translocase, the dicarboxylate carrier, and the alpha-ketoglutarate exchanger are partially inhibited by chloride. Therefore, when the goal is to maximize ADP-stimulated respiration, buffers containing K-lactobionate or K-gluconate are superior choices compared to the standard KCl-based buffers.

Spontaneous supersaturation of calcium citrate from simultaneous isothermal dissolution of sodium citrate and sparingly soluble calcium hydroxycarboxylates in water

Strongly supersaturated homogeneous calcium citrate solutions are formed spontaneously when solid sodium citrate and solid calcium hydroxycarboxylates are dissolved simultaneously in water.

ML and ML2 complex formation between Ca(ii) and d-glucose derivatives in aqueous solutions

Besides the well-known ML species, Ca(ii) forms ML₂ complexes with carbohydrates having at least one carboxylate group and conformational flexibility.

Mineral nutrient interaction: Improving bioavailability of calcium and iron

Insufficient uptake of essential metals leads to serious malnutrition, which is a worldwide problem. Low bioavailability of iron and calcium may lead to anemia and osteoporosis, respectively, even in individuals with a high dietary intake. For iron, fractionation of meat proteins was studied in order to increase iron bioavailability from other meal components, and uptake of iron was found to increase with minimal risk of increasing oxidative damage. Calcium binding to peptides was found to prevent formation of insoluble calcium salts otherwise hampering absorption particularly in combination with calcium hydroxycarboxylates, entailing spontaneous supersaturation. Based on a review of results from different strategies available for increasing bioavailability, safe iron fortification is suggested to be supported by calcium, with modulation of iron as a prooxidant.

Calcium Binding to Amino Acids and Small Glycine Peptides in Aqueous Solution: Toward Peptide Design for Better Calcium Bioavailability

Deprotonation of amino acids as occurs during transfer from stomach to intestines during food digestion was found by comparison of complex formation constants as determined electrochemically for increasing pH to increase calcium binding (i) by a factor of around 6 for the neutral amino acids, (ii) by a factor of around 4 for anions of the acidic amino acids aspartic and glutamic acid, and (iii) by a factor of around 5.5 for basic amino acids. Optimized structures of the 1:1 complexes and ΔHbinding for calcium binding as calculated by density functional theory (DFT) confirmed in all complexes a stronger calcium binding and shorter calcium-oxygen bond length in the deprotonated form. In addition, the stronger calcium binding was also accompanied by a binding site shift from carboxylate binding to chelation by α-amino group and carboxylate oxygen for leucine, aspartate, glutamate, alanine, and asparagine. For binary amino acid mixtures, the calcium-binding constant was close to the predicted geometric mean of the individual amino acid binding constants indicating separate binding of calcium to two amino acids when present together in solution. At high pH, corresponding to conditions for calcium absorption, the binding affinity increased in the order Lys < Arg < Cys < Gln < Gly ∼ Ala < Asn < His < Leu < Glu< Asp. In a series of glycine peptides, calcium-binding affinity was found to increase in the order Gly-Leu ∼ Gly-Gly < Ala-Gly < Gly-His ∼ Gly-Lys-Gly < Glu-Cys-Gly < Gly-Glu, an ordering confirmed by DFT calculations for the dipeptides and which also accounted for large synergistic effects in calcium binding for up to 6 kJ/mol when compared to the corresponding amino acid mixtures.

Calcium d-Saccharate: Aqueous Solubility, Complex Formation, and Stabilization of Supersaturation

Molar conductivity of saturated aqueous solutions of calcium d-saccharate, used as a stabilizer of beverages fortified with calcium d-gluconate, increases strongly upon dilution, indicating complex formation between calcium and d-saccharate ions, for which, at 25 °C, Kassoc = 1032 ± 80, ΔHassoc° = −34 ± 6 kJ mol–1, and ΔSassoc° = −55 ± 9 J mol–1 K–1, were determined electrochemically. Calcium d-saccharate is sparingly soluble, with a solubility product, Ksp, of (6.17 ± 0.32) × 10–7 at 25 °C, only moderately increasing with the temperature: ΔHsol° = 48 ± 2 kJ mol–1, and ΔSassoc° = 42 ± 7 J mol–1 K–1. Equilibria in supersaturated solutions of calcium d-saccharate seem only to adjust slowly, as seen from calcium activity measurements in calcium d-saccharate solutions made supersaturated by cooling. Solutions formed by isothermal dissolution of calcium d-gluconate in aqueous potassium d-saccharate becomes spontaneously supersaturated with both d-gluconate and d-saccharate calcium salts, from which only calcium d-saccharate slowly precipitates. Calcium d-saccharate is suggested to act as a stabilizer of supersaturated solutions of other calcium hydroxycarboxylates with endothermic complex formation through a heat-induced shift in calcium complex distribution with slow equilibration upon cooling.

Mineral nutrient interaction: Improving bioavailability of calcium and iron

Insufficient uptake of essential metals leads to serious malnutrition, which is a worldwide problem. Low bioavailability of iron and calcium may lead to anemia and osteoporosis, respectively, even in individuals with a high dietary intake. For iron, fractionation of meat proteins was studied in order to increase iron bioavailability from other meal components, and uptake of iron was found to increase with minimal risk of increasing oxidative damage. Calcium binding to peptides was found to prevent formation of insoluble calcium salts otherwise hampering absorption particularly in combination with calcium hydroxycarboxylates, entailing spontaneous supersaturation. Based on a review of results from different strategies available for increasing bioavailability, safe iron fortification is suggested to be supported by calcium, with modulation of iron as a prooxidant.

Calcium complexation and acid–base properties of l-gulonate, a diastereomer of d-gluconate

The structures of Ca-l-gulonate and Ca-d-gluconate complexes are slightly different due to the differences in the configuration of their ligands.

Competitive interactions between glucose and lactose with BSA: which sugar is better for children?

The study strongly suggested that, as compared with glucose, lactose is more likely to promote the growth and development of healthy children.

Yolk-Shell Porous Microspheres of Calcium Phosphate Prepared by Using Calcium L-Lactate and Adenosine 5'-Triphosphate Disodium Salt: Application in Protein/Drug Delivery

A facile and environmentally friendly approach has been developed to prepare yolk-shell porous microspheres of calcium phosphate by using calcium L-lactate pentahydrate (CL) as the calcium source and adenosine 5'-triphosphate disodium salt (ATP) as the phosphate source through the microwave-assisted hydrothermal method. The effects of the concentration of CL, the microwave hydrothermal temperature, and the time on the morphology and crystal phase of the product are investigated. The possible formation mechanism of yolk-shell porous microspheres of calcium phosphate is proposed. Hemoglobin from bovine red cells (Hb) and ibuprofen (IBU) are used to explore the application potential of yolk-shell porous microspheres of calcium phosphate in protein/drug loading and delivery. The experimental results indicate that the as-prepared yolk-shell porous microspheres of calcium phosphate have relatively high protein/drug loading capacity, sustained protein/drug release, favorable pH-responsive release behavior, and a high biocompatibility in the cytotoxicity test. Therefore, the yolk-shell porous microspheres of calcium phosphate have promising applications in various biomedical fields such as protein/drug delivery.

Calcium-buffering effects of gluconate and nucleotides, as determined by a novel fluorimetric titration method

Significantly more Ca(2+) influx is required for eliciting release of neurotransmitter during whole cell patch clamp recording in the Calyx of Held, when gluconate with 3 mm free ATP is used as pipette filling solution, as compared to a methanesulfonate-based solution with excess Mg(2+). This reduction in efficiency of Ca(2+) in eliciting release is due to low-affinity Ca(2+) binding of both gluconate and ATP(2-) anions. To study these effects we developed a simple fluorimeteric titration procedure, which reports the dissociation constant, KD, of a given Ca(2+) indicator dye, multiplied by 1 plus the sum of Ca(2+) binding ratios of any anions, which act as low-affinity Ca(2+) ligands. For solutions without Ca(2+) binding anions we find KD values for Fura2FF ranging from 11.5 ± 1.7 to 15.6 ± 7.47 μm depending on the dominant anion used. For Fura6F and KCl-based solutions we find KD = 17.8 ± 1.3 μm. For solutions with gluconate as the main anion and for solutions that contain nucleotides, such as ATP and GTP, we find much higher values for the product. Assuming that the KD of the indicator dye is equal to that of KCl-based solutions we calculate the summed Ca(2+) binding ratios and find a value of 3.55 for a solution containing 100 mm potassium gluconate and 4 mm ATP. Gluconate contributes a value of 1.75 to this number, while the contribution of ATP depends strongly on the presence of Mg(2+) and varies from 0.8 (with excess Mg(2+)) to 13.8 (in the presence of 3 mm free ATP). Methanesulfonate has negligible Ca(2+) binding capacity. These results explain the reduced efficiency of Ca(2+) influx in the presence of gluconate or nucleotides, as these anions are expected to intercept Ca(2+) ions at short distance.

Spontaneous supersaturation of calcium D-gluconate during isothermal dissolution of calcium L-lactate in aqueous sodium D-gluconate

Continuing dissolution of solid calcium L-lactate pentahydrate in saturated aqueous solutions following addition of solid sodium D-gluconate corresponding to a gluconate/lactate ratio around three was found to result in homogeneous solutions supersaturated with calcium D-gluconate by a factor of seven, from which calcium D-gluconate monohydrate precipitated only slowly. In contrast, dissolution of calcium D-gluconate monohydrate by sodium L-lactate in aqueous solution with the reverse lactate/gluconate ratio also around three did not result in similar homogeneous solutions on the route to solid calcium L-lactate pentahydrate. This increasing supersaturation of calcium D-gluconate during dissolution of calcium L-lactate in aqueous sodium D-gluconate may enhance calcium bioavailability. The dissolution overshooting depends on competitive kinetics and is also of interest in modeling biomineralization and in designing novel food products with increased calcium bioavailability.

Thermodynamics of dissolution of calcium hydroxycarboxylates in water

Aqueous solubility of calcium l-lactate, calcium d-gluconate, and calcium d-lactobionate increases with temperature (10-30 °C investigated), most significantly for the least soluble d-gluconate, while the calcium ion activity of the saturated solutions decreases with temperature, as measured electrochemically, most significantly for the most soluble d-lactobionate. This unusual behavior is discussed in relation to dairy processing and explained by endothermic binding of calcium to hydroxycarboxylate anions determined to have ΔH°ass = (31 ± 3) kJ·mol(-1) for l-lactate, (34 ± 2) kJ·mol(-1) for d-gluconate, and (29 ± 3) kJ·mol(-1) for d-lactobionate in 1:1 complexes with thermodynamic binding constants at 25 °C of Kass = 49 (l-lactate), 88 (d-gluconate), and 140 (d-lactobionate). Quantum mechanical calculations within density functional theory (DFT) confirm the ordering of strength of binding. The complex formation is entropy driven with ΔS°ass > 0, resulting in decreasing calcium ion activity in aqueous solutions for increasing temperature, even for the saturated solutions despite increasing solubility.