The stability of complexes between calcium and orthophosphate, polymeric phosphate, and phytate

Spray drying of a zinc complexing agent for inhalation therapy of pulmonary fibrosis

Pulmonary fibrosis, a disabling lung disease, results from the fibrotic transformation of lung tissue. This fibrotic transformation leads to a deterioration of lung capacity, resulting in significant respiratory distress and a reduction in overall quality of life. Currently, the frontline treatment of pulmonary fibrosis remains limited, focusing primarily on symptom relief and slowing disease progression. Bacterial infections with Pseudomonas aeruginosa are contributing to a severe progression of idiopathic pulmonary fibrosis. Phytic acid, a natural chelator of zinc, which is essential for the activation of metalloproteinase enzymes involved in pulmonary fibrosis, shows potential inhibition of LasB, a virulence factor in P. aeruginosa, and mammalian metalloproteases (MMPs). In addition, phytic acid has anti-inflammatory properties believed to result from its ability to capture free radicals, inhibit certain inflammatory enzymes and proteins, and reduce the production of inflammatory cytokines, key signaling molecules that promote inflammation. To achieve higher local concentrations in the deep lung, phytic acid was spray dried into an inhalable powder. Challenges due to its hygroscopic and low melting (25 °C) nature were mitigated by converting it to sodium phytate to improve crystallinity and powder characteristics. The addition of leucine improved aerodynamic properties and reduced agglomeration, while mannitol served as carrier matrix. Size variation was achieved by modifying process parameters and were evaluated by tools such as the Next Generation Impactor (NGI), light diffraction methods, and scanning electron microscopy (SEM). An inhibition assay for human MMP-1 (collagenase-1) and MMP-2 (gelatinase A) allowed estimation of the biological effect on tissue remodeling enzymes. The activity was also assessed with respect to inhibition of bacterial LasB. The formulated phytic acid demonstrated an IC50 of 109.7 µg/mL for LasB with viabilities > 80 % up to 188 µg/mL on A549 cells. Therefore, inhalation therapy with phytic acid-based powder shows promise as a treatment for early-stage Pseudomonas-induced pulmonary fibrosis.

An Overview of Targeted Genome Editing Strategies for Reducing the Biosynthesis of Phytic Acid: an Anti-nutrient in Crop Plants

Anti-nutrients are substances either found naturally or are of synthetic origin, which leads to the inactivation of nutrients and limits their utilization in metabolic processes. Phytic acid is classified as an anti-nutrient, as it has a strong binding affinity with most minerals like Fe, Zn, Mg, Ca, Mn, and Cd and impairs their proper metabolism. Removing anti-nutrients from cereal grains may enable the bioavailability of both macro- and micronutrients which is the desired goal of genetic engineering tools for the betterment of agronomic traits. Several strategies have been adopted to minimize phytic acid content in plants. Pursuing the molecular strategies, there are several studies, which result in the decrement of the total phytic acid content in grains of major as well as minor crops. Biosynthesis of phytic acid mainly takes place in the seed comprising lipid-dependent and lipid-independent pathways, involving various enzymes. Furthermore, some studies show that interruption of these enzymes may involve the pleiotropic effect. However, using modern biotechnological approaches, undesirable agronomic traits can be removed. This review presents an overview of different genes encoding the various enzymes involved in the biosynthetic pathway of phytic acid which is being targeted for its reduction. It also, highlights and enumerates the variety of potential applications of genome editing tools such as TALEN, ZFN, and CRISPR/Cas9 to knock out the desired genes, and RNAi for their silencing.

Impacts of orthophosphate-polyphosphate blends on the dissolution and transformation of lead (II) carbonate

Orthophosphate-polyphosphate blends are commonly used to control lead release into drinking water, but little is known about how they interact with lead corrosion scale. Conventional corrosion control practice assumes that orthophosphate controls lead release by forming insoluble Pb-phosphate minerals, but this does not always occur, and under certain conditions, phosphate blends may increase lead release. Here, we used continuously-stirred tank reactors to compare orthophosphate-polyphosphate blends with orthophosphate on the basis of lead (II) carbonate dissolution and transformation at environmentally relevant phosphate concentrations. Three model polyphosphates-tripoly-, trimeta- and hexametaphosphate-were used. Hexametaphosphate was the strongest complexing agent (1.60-2.10 mol_Pb/mol_{Polyphosphate}), followed by tripolyphosphate and trimetaphosphate (1.00 and 0.07 mol_Pb/mol_{Polyphosphate}, respectively. At equivalent orthophosphate and polyphosphate concentrations (as P), orthophosphate-trimetaphosphate had minimal impact on lead release, while orthophosphate-tripolyphosphate increased dissolved lead. Orthophosphate-hexametaphosphate also increased dissolved lead, but only over a 24-h stagnation. Both orthophosphate-tripolyphosphate and orthophosphate-hexametaphosphate increased colloidal lead after 24-h. Increasing the concentrations of hexameta- and tripoly-phosphate increased dissolved lead release, while all three polyphosphates inhibited the formation of hydroxypyromorphite and reduced the phosphorus content of the resulting lead solids. We attributed the impacts of orthophosphate-polyphosphates to a combination of complexation, adsorption, colloidal dispersion, polyphosphate hydrolysis, and lead mineral precipitation.

Hexametaphosphate as a potential therapy for the dissolution and prevention of kidney stones

The incidence of kidney stones is increasing worldwide, and recurrence is common (50% within 5 years). Citrate, the current gold standard therapy, which is usually given as potassium or sodium salts, is used because it raises urine pH and chelates calcium, the primary component of up to 94% of stones. In this study hexametaphosphate (HMP), a potent calcium chelator, was found to be 12 times more effective at dissolving calcium oxalate, the primary component of kidney stones, than citrate. HMP was also observed to be effective against other common kidney stone components, namely calcium phosphate and struvite (magnesium ammonium phosphate). Interestingly, HMP was capable of raising the zeta potential of calcium oxalate particles from -15.4 to -34.6 mV, which may prevent stone growth by aggregation, the most rapid growth mechanism, and thus avert occlusion. Notably, HMP was shown to be up to 16 times as effective as citrate at dissolving human kidney stones under simulated physiological conditions. It may thus be concluded that HMP is a promising potential therapy for calcium and struvite kidney stones.

Optimum hexametaphosphate concentration to inhibit efflorescence formation in dry fermented sausages

The occurrence of efflorescences on the surface of dry fermented sausages represents a current issue for the meat processing industry. Preventing the efflorescence formation by the addition of sodium hexametaphosphate (SHMP) was shown to be promising in a previous study. The optimum SHMP addition was studied by adding SHMP (0.0, 1.0, 3.0, and 5.0g/kg) directly to the sausage batter. Visual and chemical analyses were conducted during 8weeks of storage under modified atmosphere. Visual analyses revealed significant lower amounts of efflorescences on the sausage surface after 8weeks when 1.0 (27.1%), 3.0 (9.0%), and 5.0g/kg SHMP (3.4%) were added, compared to the control with 38.0% efflorescences. SHMP significantly affected the occurrence (8weeks) of magnesium on the surface: +85.5%, +23.7%, +3.5%, and -28.2% for 0.0, 1.0, 3.0, and 5.0g/kg, respectively. The addition of 4.785g/kg was calculated to fully inhibit the formation of efflorescences by complexing magnesium ions.

Phytic acid as alternative setting retarder enhanced biological performance of dicalcium phosphate cement in vitro

Dicalcium phosphate cement preparation requires the addition of setting retarders to meet clinical requirements regarding handling time and processability. Previous studies have focused on the influence of different setting modifiers on material properties such as mechanical performance or injectability, while ignoring their influence on biological cement properties as they are used in low concentrations in the cement pastes and the occurrence of most compounds in human tissues. Here, analyses of both material and biological behavior were carried out on samples with common setting retardants (citric acid, sodium pyrophosphate, sulfuric acid) and novel (phytic acid). Cytocompatibility was evaluated by in vitro tests with osteoblastic (hFOB 1.19) and osteoclastic (RAW 264.7) cells. We found cytocompatibility was better for sodium pyrophosphate and phytic acid with a three-fold cell metabolic activity by WST-1 test, whereas samples set with citric acid showed reduced cell number as well as cell activity. The compressive strength (CS) of cements formed with phytic acid (CS = 13 MPa) were nearly equal to those formed with citric acid (CS = 15 MPa) and approximately threefold higher than for other setting retardants. Due to a proven cytocompatibility and high mechanical strength, phytic acid seems to be a candidate replacement setting retardant for dicalcium phosphate cements.

Phytate in pig and poultry nutrition

Phosphorus (P) is primarily stored in the form of phytates in plant seeds, thus being poorly available for monogastric livestock, such as pigs and poultry. As phytate is a polyanionic molecule, it has the capacity to chelate positively charged cations, especially calcium, iron and zinc. Furthermore, it probably compromises the utilization of other dietary nutrients, including protein, starch and lipids. Reduced efficiency of utilization implies both higher levels of supplementation and increased discharge of the undigested nutrients to the environment. The enzyme phytase catalyses the stepwise hydrolysis of phytate. In respect to livestock nutrition, there are four possible sources of this enzyme available for the animals: endogenous mucosal phytase, gut microfloral phytase, plant phytase and exogenous microbial phytase. As the endogenous mucosal phytase in monogastric organisms appears incapable of hydrolysing sufficient amounts of phytate-bound P, supplementation of exogenous microbial phytase in diets is a common method to increase mineral and nutrient absorption. Plant phytase activity varies greatly among species of plants, resulting in differing gastrointestinal phytate hydrolysis in monogastric animals. Besides the supplementation of microbial phytase, processing techniques are alternative approaches to reduce phytate contents. Thus, techniques such as germination, soaking and fermentation enable activation of naturally occurring plant phytase among others. However, further research is needed to tap the potential of these technologies. The main focus herein is to review the available literature on the role of phytate in pig and poultry nutrition, its degradation throughout the gut and opportunities to enhance the utilization of P as well as other minerals and nutrients which might be complexed by phytates.

Properties of Milk Protein Gels Formed by Phosphates

We investigated the properties of gels that were formed by adding emulsifying salts, such as tetrasodium pyrophosphate (TSPP), to reconstituted milk protein concentrate solution. The pH of a 51 g/L milk protein concentrate solution was adjusted to 5.8 after adding TSPP. Milk protein concentrate solutions were placed in glass jars and allowed to stand at 25 degrees C for 24 h. Gels with the highest breaking force were formed when TSPP was added at a concentration of 6.7 mM, whereas no gel was formed when TSPP was added at concentrations of < or =2.9 or > or =10.5 mM. Several other phosphate-based emulsifying salts were tested but for these emulsifying salts, gelation only occurred after several days or at greater gelation temperatures. No gelation was observed for trisodium citrate. Gelation induced by TSPP was dependent on pH, and the breaking force of gel was greatest at pH 6.0. Furthermore, when the concentration of milk protein concentrate in solution was increased to 103 g/L, the breaking force of the gel increased, and a clearly defined network between caseins could be observed by using confocal scanning laser microscopy. These results suggest that TSPP-induced gelation occurs when the added TSPP acts with calcium as a cross-linking agent between dispersed caseins and when the balance between (a reduced) electrostatic repulsion and (enhanced) attractive (hydrophobic) interactions becomes suitable for aggregation and eventual gelation of casein molecules.

Effects of LDL, cholesterol, and their oxidized forms on the precipitation kinetics of calcium phosphates

BACKGROUND

LDL, cholesterol, and their oxidized forms are known cardiovascular risk factors and are often found in atherosclerotic lesions of various stages. Little is known, however, about whether they are directly involved in the formation of calcium phosphate compounds.

METHODS

We used the pH-stat technique to follow the kinetics of calcium phosphate precipitation at pH 7.4, 37 degrees C, and ionic strength 0.150 mol/L, in the presence or absence of LDL, oxidized LDL, cholesterol, cholestane-3beta,5alpha,6beta-triol, and cholesteryl linoleate. The precipitates were characterized by x-ray diffraction, scanning and transmission electronic microscopy coupled with energy-dispersion x-ray analysis, and inductively coupled plasma atomic emission spectroscopy.

RESULTS

Under the experimental conditions, LDL (14.8 and 43.1 mg/L protein) had no significant effect on the precipitation kinetics. Oxidized LDL (14.8 and 43.1 mg/L protein) prolonged the nucleation phase and diminished the amount of total precipitate, and both the extent of oxidation and the concentration of the protein affected the kinetics. Cholesterol microcrystals (71.4 and 143 mg/L) made the nucleation phase shorter (300 min vs 390 min for the control), and the precipitated particles had an organic core and a shell composed of calcium phosphates. L-alpha-Phosphatidylcholine vesicles (143 mg/L), cholesterol (71.4 mg/L)/phospholipid (143 mg/L) mixed vesicles, cholesteryl linoleate (143 mg/L), and cholestane-3beta,5alpha,6beta-triol (71.4 mg/L) prolonged the nucleation phase.

CONCLUSIONS

LDL is not involved directly in the precipitation of calcium phosphates. Oxidized LDL inhibits both nucleation and crystal growth, possibly by attracting calcium ions in the solution and thus reducing supersaturation. Cholesterol microcrystals serve as seeds for the precipitation of hydroxyapatite, whereas L-alpha-phosphatidylcholine, cholesteryl linoleate, and cholestane-3beta,5alpha,6beta-triol exhibit inhibitive effects on the nucleation of calcium phosphates.

Process-induced compositional changes of flaxseed

Flaxseed has been used as an edible grain in different parts of the world since ancient times. However, use of flaxseed oil has been limited due to its high content of polyunsaturated fatty acids. Nonetheless, alpha-linolenic acid, dietary fiber and lignans of flaxseed have regained attention. New varieties of flaxseed containing low levels of alpha-linolenic acid are available for edible oil extraction. Use of whole flaxseed in foods provides a means to utilise all of its nutrients and require minimum processing steps. However, the presence of cyanogenic glucosides and diglucosides in the seeds is a concern as they may release cyanide upon hydrolysis. In addition, the polyunsaturated fatty acids may undergo thermal or autooxidation when exposed to air or high temperatures that are used in food preparation. Studies todate on oxidation products of intact flaxseed lipids have not shown any harmful effects when flaxseed is included, up to 28%, in the baked products. Furthermore, cyanide levels produced as a result of autolysis are below the harmful limits to humans. However, the meals left after oil extraction require detoxification but, by solvent extraction, to reduce the harmful effects of cyanide when used in animal rations. Flaxseed meal is a good source of proteins; these could be isolated by complexation with sodium hexametaphosphate without changing their nutritional value or composition. In addition, the effect of germination on proteins, lipids, cyanogenic glycosides, and other minor constituents of flaxseed is discussed.

Neuronal cytotoxicity of inositol hexakisphosphate (phytate) in the rat hippocampus

D-myo-Inositol hexakisphosphate (InsP6, phytate), a normal cellular constituent, was found to be toxic to neuronal perikarya when injected into the rat hippocampus. However, the extrinsic cholinergic innervation of the hippocampus (as estimated by staining for acetylcholinesterase) was unaffected. Its potency as a toxin was approximately equal to that of the excitotoxin quinolinate. Other highly charged derivatives of inositol (inositol hexakissulphate, inositol monophosphate) were not toxic. The cytotoxicity of InsP6 was not due to a high osmolality, or to seizure-induced lesions, but was reduced by calcium. Nevertheless, the toxicity was not due to chelation of brain calcium by InsP6, as another calcium chelator with a higher affinity for calcium, 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA), produced only a very mild lesion. Thus, abnormal metabolism of InsP6 might possibly contribute to neuronal death in neurodegenerative diseases.

The cement-forming properties of phytic acid

The properties of aluminosilicate-phytic acid cements were investigated. They proved to be fast-setting and resistant to acid attack, with the ability to bond to enamel, but not to dentin.

Phytic acid interactions in food systems

Phytic acid is present in many plant systems, constituting about 1 to 5% by weight of many cereals and legumes. Concern about its presence in food arises from evidence that it decreases the bioavailability of many essential minerals by interacting with multivalent cations and/or proteins to form complexes that may be insoluble or otherwise unavailable under physiologic conditions. The precise structure of phytic acid and its salts is still a matter of controversy and lack of a good method of analysis is also a problem. It forms fairly stable chelates with almost all multivalent cations which are insoluble about pH 6 to 7, although pH, type, and concentration of cation have a tremendous influence on their solubility characteristics. In addition, at low pH and low cation concentration, phytate-protein complexes are formed due to direct electrostatic interaction, while at pH > 6 to 7, a ternary phytic acid-mineral-protein complex is formed which dissociates at high Na+ concentrations. These complexes appear to be responsible for the decreased bioavailability of the complexed minerals and are also more resistant to proteolytic digestion at low pH. Development of methods for producing low-phytate food products must take into account the nature and extent of the interactions between phytic acid and other food components. Simple mechanical treatment, such as milling, is useful for those seeds in which phytic acid tends to be localized in specific regions. Enzyme treatment, either directly with phytase or indirectly through the action of microorganisms, such as yeast during breadmaking, is quite effective, provided pH and other environmental conditions are favorable. It is also possible to produce low-phytate products by taking advantage of some specific interactions. For example, adjustment of pH and/or ionic strength so as to dissociate phytate-protein complexes and then using centrifugation or ultrafiltration (UF) has been shown to be useful. Phytic acid can also influence certain functional properties such as pH-solubility profiles of the proteins and the cookability of the seeds.

Solubility of CaHPO4 · 2H2O in the System Ca(OH)2-H3PO4-H2O at 5, 15, 25, and 37.5 °C

Solubility isotherms for CaHPO4 · 2H2O, dicalcium phosphate dihydrate, DCPD, in the ternary system Ca(OH)2 - H3PO4 - H2O were determined at 5, 15, 25, and 37.5 °C in the pH range 3.5 - 7; the relative positions of the isotherms indicate that DCPD has a negative thermal coefficient of solubility. The solubility product, K s , of DCPD and the stability constants K x and K y for the ion pairs [ CaHPO 4 0 ] and[ CaH 2 PO 4 + ] , respectively, were obtained as functions of temperature by the use of a generalized least squares procedure subject to three condition functions - constancy of the solubility product, electrical neutrality in the solution, and congruent dissolution of the solid. The equations obtained areln  K s = - 8403 .5 / T + 41 . 863 - 0 . 09678 T ​ln  K x = - 51090 / T - 341.14 + 0 . 5880 T ​ln  K y = - 19373 / T - 122.81 + 0 . 1994 T The existence of a maximum in K s in the neighborhood of 25 °C is plausible on the basis of available thermodynamic data for DCPD. Thermodynamic functions are reported for the solution of DCPD and for the association of the ion pairs.

The calcium content of human erythrocytes

1. The calcium content of human erythrocytes, after removal of the buffy coat and washing free from plasma with isotonic sodium chloride, has been determined by atomic absorption spectrophotometry. The mean value found for normal subjects was 0.634 mug/ml. of packed erythrocytes (0.0158 mug-atom/ml.). The corresponding values for magnesium and zinc were 79.7 and 20.1 mug/ml., respectively.2. The calcium is considered to be mostly and perhaps exclusively located in the erythrocyte membrane, since, after osmotic haemolysis, the same amount was found in the ghost cells as was present in the erythrocytes from which they were prepared. By contrast, magnesium and zinc, which are essentially intracellular, were lost to the extent of about 96 and 92%, respectively.3. About 90% of the calcium was removed from erythrocytes by washing with isotonic sodium chloride containing 5 mM ethylenediaminetetraacetate (EDTA), or other complexing agents of high stability constant for calcium. A small fraction of the magnesium but none of the zinc was removed by this treatment.4. Other complexing agents of lower stability constant removed somewhat less calcium from the erythrocytes. Citrate was totally ineffective.5. The buffy coat had a high calcium content, but this could not be removed by washing with EDTA.6. Calcium was also determined in trichloroacetic acid extracts of ghost cells after ashing and treatment with bis-(o-hydroxyphenylimino)-ethane and measuring the red complex spectrophotometrically. The values obtained confirmed the atomic absorption measurements.

Solubility of CaHPO4 · 2H2O and Formation of Ion Pairs in the System Ca(OH)2- H3PO4 - H2O at 37.5 °C

The solubility isotherm for CaHPO₄ · 2H₂O (DCPD) in the three-component system Ca(OH)₂ - H₃PO₄ - H₂O was determined in the pH range 3.5 to 6.8 by leaching a thermostated column of DCPD with dilute phosphoric acid solutions. In confirmatory experiments, equilibrium was approached both from super- and under-saturation by shaking DCPD with appropriate solutions. The calculated ionic activity product (Ca⁺⁺) × ( HPO 4 = ), appeared to be a parabolic function of pH with a minimum near pH 5.0. The pH dependence of the ionic product could be accounted for by considering the ion pairs [CaHPO₄]° and [CaH₂PO₄]⁺ as semi-empirical parameters. Under the condition of saturation with respect to DCPD, the activity of the pair [CaHPO₄]° must be a constant. The activity of the species [CaH₂PO₄]⁺ was shown to vary directly with hydrogen ion activity. The activities of the two ion pairs were adjusted to give a set of pH-independent ionic activity products with a mean of 2.19±0.011 × 10^-7. The stability constants for [CaHPO₄]° and [CaH₂PO₄]⁺ are 5.88±0.031 × 10² and 7.49 ±0.039, respectively. Experiments were conducted to study the hydrolysis of DCPD to more basic calcium phosphates and the kinetics of these transformations is discussed. The significance of the ion pairs in human serum is considered.