Deposition Of Calcium Ions Research Articles

RGD-functionalised self-assembling peptide hydrogel induces a proliferative profile in human osteoblasts in vitro.

Self-assembling peptide hydrogels (SAPHs) have been used in the past decade as reliable three-dimensional (3D) synthetic scaffolds for the culture of a variety of mammalian cells in vitro. Thanks to their versatile physicochemical properties, they allow researchers to tailor the hydrogel properties, including stiffness and functionality to the targeted cells and cells' behaviour. One of the advantages of using SAPH scaffolds is the ease of functionalisation. In the present work, we discuss the effect that functionalising the FEFEFKFK (F, phenylalanine; K, lysine; and E, glutamic acid) hydrogel scaffold using the cell-binding RGDS (fibronectin - R, arginine; G, glycine; D, aspartic acid; S, serine) epitope affects the material properties as well as the function of encapsulated human osteoblast cells. RGDS functionalisation resulted in cells adopting an elongated morphology, suggesting attachment and increased proliferation. While this led to higher cell viability, it also resulted in a decrease in extra-cellular matrix (ECM) protein production as well as a decrease in calcium ion deposition, suggesting lower mineralisation capabilities. The work clearly shows that SAPHs are a flexible platform that allow the modification of scaffolds in a controlled manner to investigate cell-material interactions.

Harnessing the Regenerative Potential of Purified Bovine Dental Pulp and Dentin Extracellular Matrices in a Chitosan/Alginate Hydrogel.

When a tooth is diseased or damaged through caries, bioactive molecules are liberated from the pulp and dentin as part of the natural response to injury and these are key molecules for stimulating stem cell responses for tissue repair. Incorporation of these extracellular-matrix (ECM)-derived molecules into a hydrogel model can mimic in vivo conditions to enable dentin-pulp complex regeneration. Here, a chitosan/alginate (C/A) hydrogel is developed to sequester bovine ECM extracts. Human dental pulp cells (hDPCs) are cultured with these constructs and proliferation and cytotoxicity assays confirm that these C/A hydrogels are bioactive. Sequential z-axis fluorescent imaging visualizes hDPCs protruding into the hydrogel as it degraded. Alizarin red S staining shows that hDPCs cultured with the hydrogels display increased calcium-ion deposition, with dentin ECM stimulating the highest levels. Alkaline phosphatase activity is increased, as is expression of transforming growth factor-beta as demonstrated using immunocytochemistry. Directional analysis following phase contrast kinetic image capture demonstrates that both dentin and pulp ECM molecules act as chemoattractants for hDPCs. Data from this study demonstrate that purified ECM from dental pulp and dentin when delivered in a C/A hydrogel stimulates dental tissue repair processes in vitro.

PCSK9 inhibitors ameliorate arterial stiffness in ACS patients: evidences from Mendelian randomization, a retrospective study and basic experiments.

Current evidences suggest that Proprotein Convertase Subtilisin/kexin Type 9 inhibitors (PCSK9i) exhibit a protective influence on acute coronary syndrome (ACS). Nevertheless, further investigation is required to comprehend the impact and mechanisms of these pharmaceutical agents on inflammatory factors and arterial stiffness (AS) in patients with ACS. Consequently, the objective of this study is to ascertain the influence of PCSK9i on arterial stiffness in ACS patients and elucidate the underlying mechanisms behind their actions. This study employed Mendelian randomization (MR) analysis to examine the association between genetic prediction of PCSK9 inhibition and arterial stiffness. Data of 71 patients with ACS were retrospectively collected, including PCSK9i group (n = 36, PCSK9 inhibitors combined with statins) and control group (n = 35, statins only). Blood lipid levels, inflammatory markers and pulse wave velocity (PWV) data were collected before treatment and at 1 and 6 months after treatment for analysis. Additionally, cell experiments were conducted to investigate the impact of PCSK9i on osteogenesis of vascular smooth muscle cells (VSMCs), utilizing western blot (WB), enzyme-linked immunosorbent assay (ELISA), and calcification index measurements. The results of the MR analysis suggest that genetic prediction of PCSK9 inhibition has potential to reduce the PWV. Following treatment of statins combined with PCSK9 inhibitors for 1 and 6 months, the PCSK9i group exhibited significantly lower levels of total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), C-reactive protein (CRP), interleukin-6 (IL-6), fibrinogen (FIB) and procalcitonin (PCT) compared to the control group (p < 0.05). Additionally, PWV in the PCSK9i group demonstrated significant reduction after 6 months of treatment and was found to be associated with the circulating CRP level. In cell experiments, PCSK9i pretreatment ameliorated osteogenesis of VSMCs through reducing the deposition of calcium ions, alkaline phosphatase (ALP) activity, and expression of runt-related transcription factor 2 (RUNX2). PCSK9i have potential to enhance arterial stiffness in ACS patients. Specifically, at the clinical level, this impact may be attributed to alterations in circulating CRP levels. At the cellular level, it is associated with the signaling pathway linked to RUNX2.

Calcium Ion Deposition with Precipitated Calcium Carbonate: Influencing Factors and Mechanism Exploration

In order to apply precipitated calcium carbonate (PCC) in the detergent industry, its ability to deposit calcium ions in hard water is an important process. In this work, the calcium ion deposition in the presence of PCC from different sources is investigated to reveal the influencing factors and mechanism of nucleation and crystal growth of CaCO3. SEM, XRD, Malvern particle size analysis, and calcium electrodes are used to evaluate the effects of PCC morphology, saturation of Ca2+, and PCC additive amount on the deposition behavior of CaCO3. Through SEM and Malvern particle size analysis, it is found that the precipitation of calcium ions is obviously accelerated by PCC acting as seeds. Moreover, calcium ions are effectively adsorbed on (211) crystal facets, thus prismatic and scalenohedral PCC crystals exhibit better adsorption performance than irregular cubic PCC ones. In addition, XRD demonstrates that PCC reduces or even eliminates the formation of crystals such as vaterite, displaying high deposition capacity under complex water conditions (slightly acidic or highly alkaline pH, low magnesium ion concentration (&lt;0.01 M), and temperatures of 0–60 °C), forming thermodynamically stable calcite in water, which significantly controls the instability of the washing process.

EFFICIENCY OF PLANTING CALCIUM IONS FROM DILUTE AQUEOUS SOLUTIONS IN THE FORM OF PHOSPHATES

The specifics of calcium phosphate formation process during diluted aqueous solutions softening for home or office were researched. Studies have shown that, unlike calcium carbonate, effective precipitation of calcium ions with phosphate is possible even at doses less than stoichiometric. The ratio between concentrations of phosphate ions and calcium ions K = [PO43-, mg-eq] / [Ca2+, mg-eq] is a determining factor. Already at K = 0.5 there is a decrease in the content of calcium ions by more than half. In stoichiometry (K = 1), the residual concentrations of calcium ions in the treated water fall below 1 mg-eq/dm3. At K &gt; 1.5, the content of calcium ions in the treated water stabilizes at the level of 0.2 – 0.1 mg-eq/dm3. Water temperature does not significantly affect the deposition of calcium ions with phosphates. A noticeable decrease in efficiency is recorded only at a temperature of 5 ° C. But even in this case, this decrease is 0.1 – 1.5 mg-eq/dm3, which is quite acceptable for living conditions, since it provides soft and very soft water. The reaction between calcium ions and phosphates is quite complete in the first minutes of contact. The settling of mixed solutions for an hour showed that the reaction of the formation of a solid phase takes place at the time of draining the solutions and over time the residual hardness of the water practically does not change. From the point of view of softening efficiency, phosphate is quite suitable as a reagent for removing calcium ions from hard natural waters. An important aspect of the softening technology is the separation of the precipitate formed from the treated water. To do this, it is necessary to determine the conditions for the formation of a crystalline, most compact and formed precipitate. The clarification of the hard water sample treated with sodium phosphate showed that there was no significant difference in deposition at different initial pH values.

Calcifying nanoparticles initiate the calcification process of mesenchymal stem cells in vitro through the activation of the TGF-β1/Smad signaling pathway and promote the decay of echinococcosis

Abstract The role of the calcifying nanoparticles (CNPs) in the calcification process of the outer cyst wall in hepatic cystic echinococcosis (HCE) remains unknown. CNPs were isolated from the tissues of the patients with HCE. Western blotting, alkaline phosphatase staining, and alizarin staining were performed to detect the cellular calcium ion deposition induced by the CNPs. CCK-8 and flow cytometry assays were conducted to determine the effect of CNPs on the apoptosis of mesenchymal stem cells (MSCs). Western blot experiments were performed to examine the expression levels of apoptosis-related factors and TGF-β1/Smad signaling pathway constituents. Treatment with CNPs induced the differentiation of MSCs. Calcium-related proteins, including OPN, BMP-2, and RUNX2, were upregulated after the CNP treatment. Similarly, CNP exposure increased the cellular calcium ion deposition in MSCs. In addition, the expression of Bax and Caspase-8 was elevated by the CNPs in MSCs. Treatment with CNPs promoted MSC apoptosis and inhibited the MSC growth. The TGF-β1/Smad signaling pathway was also activated after the CNP treatment. This study indicated that CNPs may play a critical role in initiating calcification of the outer cyst wall of HCE and promote the decay of echinococcosis, providing a new strategy for the treatment of hepatic echinococcosis.

Nanofibrillated cellulose/cyclodextrin based 3D scaffolds loaded with raloxifene hydrochloride for bone regeneration

This study intended to design novel nanofibrillated cellulose/cyclodextrin-based 3D scaffolds loaded with raloxifene hydrochloride for bone regeneration. The scaffolds were prepared using two different types of cyclodextrins namely; beta-cyclodextrin and methyl-beta-cyclodextrin. The prepared scaffolds were evaluated by characterizing their porosity, compressive strength, in-vitro drug release, FT-IR and XRD as well as their morphological properties using SEM. Results presented that the prepared scaffolds were highly porous, additionally, the scaffold containing drug/beta-cyclodextrin kneaded complex (SC5) showed the most controlled drug release pattern with the least burst effect and reached almost complete release at 480 h. The in-vitro cytocompatibility and regenerative effect of the chosen scaffold (SC5) was assessed using Saos-2 cell line. Results proved that SC5 was biocompatible. Moreover, it enhanced the cell adhesion, alkaline phosphatase enzyme expression and calcium ion deposition which are essential factors for bone mineralization. The obtained observations presented a novel, safe and propitious approach for bone engineering.

Etoricoxib-loaded bio-adhesive hybridized polylactic acid-based nanoparticles as an intra-articular injection for the treatment of osteoarthritis.

Osteoarthritis is a major problem in elder people. Etoricoxib-loaded bio-adhesive hybridized nanoparticles were prepared using polylactic acid (PLA) and chitosan hydrochloride (CS-HCl) in presence of Captex®200 as a liquid oil, polyvinyl alcohol (PVA) and Tween®80 as surfactants. The study aimed to present a new intra-articular treatment of osteoarthritis with anti-inflammatory as well as bone rebuilding effects. Hybridized nanoparticles were fabricated applying the emulsion solvent evaporation technique then assessed for particle size, zeta potential, entrapment efficiency and in-vitro drug release. Furthermore, FT-IR and DSC in addition to morphological examination were done. Results revealed that the formulation composed of PLA:Captex®200 in ratio 1:2 (w/w), 1%w/v Tween®80, 0.3% w/v CS-HCl and 3%w/v PVA possessed the smallest particle size and the most sustained drug release, thus was sorted for further analyses. The selected formulation ability to interact with the negatively charged sodium fluroscein was evaluated to predict its binding with the naturally occurring hyaluronic acid in the knee joint where promising results were obtained. Results showed the cytocompatibility of the formulation when tested using MC3T3-E1 normal bone cell line, enhanced ALP activity and increased calcium ion deposition and binding. Results suggested that the presented formulation can be considered as an innovative approach for osteoarthritis.

Evolution of the microstructural and mechanical properties of hydroxyapatite bioceramics with varying sintering temperature

Abstract This study highlights the effects of sintering temperature on the microstructures, densification, grain sizes/boundaries, calcium/phosphorus (Ca/P) ion ratios, mechanical and bioactive properties of biocompatible hydroxyapatite (HA) ceramics prepared via cold isostatic pressing. X-ray diffraction refinement analysis revealed that the phase ratios of hexagonal HA and secondary phases were sensitive to the sintering temperature. Grain sizes, densities, and shrinkages of the as-sintered HA ceramics increased with increasing sintering temperature. The Ca/P ratios of the as-sintered HA specimens ranged from 1.63 to 1.71 for sintering temperatures of 900–1300 °C. The maximum mechanical hardness was achieved in the specimen sintered at 1200 °C due to the dense matrix formed with a smaller grain size and fewer flawed grain boundaries, as determined by high-resolution transmission electron microscopy. Ion release analysis (in a simulated body fluid solution) indicated that phosphorus ions were absorbed and rapid deposition of calcium ions occurred after immersion periods of above 4 days.

Novel anti-biofouling bioactive calcium silicate-based cement containing 2-methacryloyloxyethyl phosphorylcholine.

Calcium silicate-based cements (CSCs) are commonly used for endodontic procedures; however, their antibacterial effects are limited. The objective of this study was to develop a 2-methacryloyloxyethyl phosphorylcholine (MPC)-incorporated CSC with improved antibacterial properties, while maintaining the original advantageous features of CSC. MPC was incorporated into a commercial CSC (Endocem MTA) at 0 wt% (control), 1.5%, 3.0 wt%, 5.0 wt%, 7.5 wt%, and 10 wt%. The setting time, compressive strength, water sorption, and glycerol contact angle were measured. Protein absorption was measured and bacterial adhesion on the surface was evaluated using Enterococcus faecalis. The bactericidal effect was examined by the disc diffusion test. Mineralization ability was assessed based on calcium ion deposition, as assessed by alizarin red staining, after immersion into Hank’s balanced salt solution for 7 days. High concentrations of MPC in CSC (7.5 wt% and 10 wt%) increased the setting time, reduced compressive strength, and reduced wettability. MPC (3 wt%) had greater protein repellent and anti-biofouling effects than those of control and test materials (P < 0.001). However, no bactericidal effect was observed for any control or test materials. There was greater calcium ion deposition on the surface of MPC-supplemented CSC than on the control (P < 0.001). The addition of 3 wt% MPC polymer to CSC confers protein-repellent properties and reduced bacterial attachment, with the potential for improved mineralization.

An In Vitro Study on the Effect of Five Commercial Calcium Supplements on Human Osteoblast Cell Proliferation and Ca2+ Mineralization

Calcium is an essential mineral that supports bone and joint health. It is used as a supplement, most typically as calcium carbonate, to assist in preserving bone density especially when dietary calcium intake is inadequate. In the present study we examined the effect of five varied calcium sources, three natural and two synthetic, on stimulation, proliferation and mineralization of cultured human osteoblast cells. A MTT assay using cultured human fetal osteoblast cells (hFOB 1.19) was used to determine the effective proliferative dose for salmon collagen bone calcium (0.25 mg/ml). Elemental calcium equivalence was used to select the appropriate doses for algae calcium (0.14 mg/ml), eggshell powder (0.16 mg/ml), calcium citrate (0.22 mg/ml) and calcium carbonate (0.13). Alkaline phosphatase activity, DNA synthesis rates and calcium ion deposition were evaluated after incubation under different conditions and harvesting the cells. Alkaline phosphatase activity, DNA synthesis rates and calcium ion deposition rates were all highest for the natural salmon bone collagen calcium, followed by algae calcium. The eggshell powder, calcium citrate and calcium carbonate did not exhibit significant changes from control in most of these assays. The results of these assays suggest that natural marine collagen calcium such as salmon bone collagen calcium acts as the most effective intervention on osteoblast performance and actual calcium deposition. It should be recommended as a superior supplement for improved bone and joint health function.

Effect of Hydrothermal Treatment in Calcium Phosphate Solution on SUS304 Substrate

SUS 304 stainless steel is known to be a biocompatible material and is widely used as screws or plates. However, issues regarding iron ion release after implantation become a concern which limits the application of SUS304. Therefore, to overcome these shortcomings, surface modification on SUS304 by forming calcium layer is needed to disable iron release from the substrate and also to encourage cell attachment. In this study, initially SUS 304 substrate are subjected to electrolysis process in sodium chloride solution to form pitting corrosion. These pitting corrosion will give the anchoring effect for the calcium ions to attach. Then the substrate are subjected to hydrothermal treatment at 200°C in calcium phosphate solution for 24, 36, 48, and 60 hours for deposition of calcium ions on the pitted SUS304 surface. Surface morphology observed by scanning electron microscope (SEM) shows that the calcium ions were deposited on the surface of the SUS304 substrate regardless hydrothermal treatment time. Rockwell hardness values shows that as hydrothermal treatment time increased the hardness value decreases. Therefore, hydrothermal treatment method enables the deposition of calcium ions layer on the surface of SUS304 which will inhibit the release of iron ions and enhanced bone attachment with the implant due to the bonding of the calcium ions with the bone.

Hydroxyapatite-containing gelatin/chitosan microspheres for controlled release of lysozyme and enhanced cytocompatibility.

A simple polymer microsphere was dramatically transformed into a novel protein delivery carrier by the incorporation of hydroxyapatite (HA) into the polymeric phase. In this study, nano-sized HA was uniformly mixed in a gelatin/chitosan solution to ultimately form composite microspheres with a well-defined spherical shape. The physicochemical properties of these microspheres were extensively characterized in terms of morphological analysis, crystalline structure, swelling properties, etc. The average sizes of the microspheres increased slightly due to a gradual increase in viscosity of the HA-containing gelatin/chitosan solution. The typical characteristics of HA used in this work were confirmed to result in the successful fabrication of composite microspheres with graded HA content (0 to 55 %). The HA-containing microspheres showed outstanding features with respect to in vitro calcification, high protein loading/controlled release, and cytocompatibility. First, the addition of HA made composite microspheres greatly facilitated in vitro calcium ion deposition while initiating nucleation in stimulated body fluid (SBF). Second, the HA-involved composite microspheres acted as a highly efficient delivery system when compared to bare polymer microspheres. These features were mostly a result of the relatively good swelling properties and protein adsorption capability of HA. Third, the HA-containing composite microspheres showed significantly improved initial cell adhesion/proliferation. The increase in HA content and surface roughness provided a favorable matrix for the attached cells, which grew extensively in elongated, spindle-like shapes. In summary, this study investigated a high protein loading/controlled release system consisting of nano-sized HA as a key component, which contributed superior features of in vitro calcification and cytocompatibility.

Influence of calcium ion deposition on apatite-inducing ability of porous titanium for biomedical applications

In the present study, the influence of calcium ion deposition on the apatite-inducing ability of porous titanium(Ti) was investigated in a modified simulated body fluid (m-SBF). Calcium hydroxide (Ca(OH) 2) solutions with five degrees of saturation were used to hydrothermally deposit Ca ions on porous Ti with a porosity of 80%. Apatite-inducing ability of the Ca-ion-deposited porous Ti was evaluated by soaking them in m-SBF for up to 14 days. Scanning electron microscopy (SEM) and X-ray diffractometry (XRD) confirmed that a thin layer of calcium titanate (CaTiO 3)/calcium oxide (CaO) mixture with a nanostructured porous network was produced on porous Ti substrates after hydrothermal treatment at 200 °C for 8 h. X-ray photoelectron spectroscopy results demonstrated that the content of the Ca ions deposited on Ti and the thickness of the CaTiO 3/CaO layer increased with increasing saturation degree of the Ca(OH) 2 solution. The thickest (over 10 nm) CaTiO 3/CaO layer with the highest Ca content was achieved on the Ti treated in an oversaturated Ca(OH) 2 solution (0.2 M). SEM, XRD, transmission electron microscopy and Fourier transformed infrared spectroscopy analysis indicated that the porous Ti samples deposited with the highest content of Ca ions exhibited the best apatite-inducing ability, producing a dense and complete carbonated apatite coating after a 14 day soaking in m-SBF. The present study illustrated the validity of using Ca ion deposition as a pre-treatment to endow desirable apatite-inducing ability of porous Ti for bone tissue engineering applications.

Calcium ions are abnormally distributed in the skin of haemodialysis patients with uraemic pruritus.

Although a close relationship between uraemic pruritus and serum calcium levels has been demonstrated for some time, the degree of pruritus was not always correlated with calcium concentrations. In the present study, we assessed calcium ion distribution in the skin of chronic haemodialysis patients with and without pruritus. We excluded patients with concomitant psoriasis or atopic dermatitis or with a previous history of allergy, those who had an arteriovenous fistula created prior to induction of haemodialysis, and patients with only mild pruritus. From the enrolled 22 haemodialysis patients, we obtained forearm skin samples during arteriovenous fistula surgery. These patients were divided into two groups based their grade of pruritus. The pruritus group included patients with moderate to severe grades of pruritus (n = 11, age 64 +/-13 years) and the non-pruritus group consisted of patients without pruritus (n = 11, age 59 +/-13 years). We compared the distribution of calcium ions in the epidermis between the two groups using the ion-capture method (oxalate-pyroantimonate-osmium technique). In addition, we examined and compared the groups for thicknesses of the basal, spinous and granular layers, as well as of the stratum corneum using an electron microscope. The pruritus group had significantly higher calcium ion deposition in the extracellular fluid and cytoplasm of basal cells, and in the extracellular fluid, nuclei and cytoplasm of spinous cells compared with the non-pruritus group. In contrast, calcium ion depositions were similar between the two groups in the dermis/basal layer interface, the nucleus of basal cells, the nucleus and cytoplasm of granular cells, exterior of granular cells, the granular cells/stratum corneum interface, and in the interior and exterior of corneocytes. Although the stratum corneum was significantly thicker in the pruritus group than in the non-pruritus group, there were no differences in basal cell, spinal cell or granular cell layer thicknesses. In chronic haemodialysis patients with pruritus, the calcium ion concentration in the deepest layer of the epidermis was increased, which indicated a disrupted calcium ion gradient in the skin. These findings point to a role for increased skin calcium ion concentrations in the development and/or maintenance of uraemic pruritus. However, more extensive studies in larger patient cohorts will be necessary to confirm this hypothesis.

Biphasic hypercalcemia in severe rhabdomyolysis: serial analysis of PTH and vitamin D metabolites. A case report and literature review

Calcemic fluxes with hypocalcemia leading to hypercalcemia in acute rhabdomyolisis are poorly understood. Analyses in the literature of the factors modulating the blood calcium level include 2, possibly 3 systems. Conflicting results implicate the parathyroid hormone and vitamin D metabolites, but additional contribution from skeletal and muscle calcium ion deposition and dissolution have been cited in some cases, potentially even dominating control of blood calcium during recovery. We have had the opportunity to study in detail a patient presenting with the most severe rhabdomyolisis, serum creatine phosphokinase levels exceeding 106 U/L, thus providing an analysis that delineates major changes in regulatory factors controlling calcium status. We found an exaggerated and clearly defined, phasic sequence of changes in these factors that led to ostensibly atypical, biphasic hypercalcemia juxtaposing the transient and well-described hypocalcemia in such patients. Our conclusions help to clarify the controversy, adding substance to the argument that there is no disruption in the parathyroid hormone-vitamin D axis regulating blood calcium levels in this rare disease.

Origin of observed acidic–alkaline rains in a wet-only precipitation study in a Mediterranean coastal site, Patras, Greece

Major anions and cations were analyzed in a wet-only precipitation study for 16 months. The pH exhibited large variation, from 4.07 to 8.51 pH units. Twenty-eight percent of the observed rain volume had pH <5, whereas 42% of the rains had pH >6, as is usually observed in the Mediterranean. Comparison with our work of 15 years ago indicates a free acidity reduction by ∼18%, non-sea-salt sulfate ions reduction of ∼40% and nitrate ions reduction of 66%. Chloride and all cation concentrations were similar in the present work and that carried out in 1985–86 indicating similar sources, namely aerosol and crustal material as in MS. Calcium ions were the dominating neutralization ions. The annual wet-only deposition rates were calculated for the major species and were found to be comparable to those reported in past studies. Deposition of calcium ions dominates all deposited species, except sea salt, and indicates its significance in the neutralizing mechanisms of soils of the region, if neutralization is needed. Air mass back trajectories calculated for all analyzed samples, revealed four sectors of origin of air masses: NW to NE Europe, northern Africa, local and western Mediterranean, each with a specific chemistry. Cluster analysis and factor analysis also discriminated the samples by their sources. The main sources derived from the statistical analysis were: marine aerosols, alkalinity–acidity as inferred by the calcium ion concentrations from crustal sources and hydronium ions mainly from anthropogenic activities and ammonium salts of sulfate and nitrate also mainly from anthropogenic activities. These sources were closely correlated with the geographic sectors obtained from the air mass back trajectories.

Deposition of calcium ions on rutile (110): a first-principles investigation

The deposition of calcium ions is the first and most crucial step of apatite nucleation on ceramic supports from ionic solution. This process is believed to initiate the growth of bone-like material on the surface of biocompatible implants. We have investigated the adsorption of Ca 2+ from water solution on the rutile TiO 2 (110) surface by means of first principles techniques. The preferential binding site of the calcium ion on the hydrated oxide surface was determined through a series of static calculations. Molecular dynamics simulations were then performed to elucidate the deposition pathway. The driving force for adsorption is identified in the electrostatic interaction between the Ca 2+ complexes and negatively charged deprotonated sites present on the hydrated TiO 2 (110) surface.

In vivo iontophoretic delivery of calcium ions through guinea pig skin enhanced by direct and pulsating current

Studies were initiated to investigate the effect of the delivery mode of45Ca ions through guinea pig skin in vivo. Direct current (DC), pulsating current (PC) and a Bernard current form, the “courtes periodes” current profile (CP) were applied with the same current density (0.16 mA/cm2) and for the same duration (30 minutes). The45Ca ions were delivered from a Ca-bentonite patch radiolabeled with45Ca (a natural mineral clay rich in calcium, 50 mgCa/g). The total quantity of applied bentonite was 1.5g×10 days=15g.45Ca was counted in different biological samples of the animals. The delivery of45Ca ions into the body (systemic effect) is the highest when CP current is applied (6.87±0.95·10−12g/samples). The local effect appears to be more effective in case of DC current mode (5.89±0.12·10−12g/0.5g bone). Total calcium measurements proved that the result of transdermal radiocalcium delivery is not only an ion exchange process at the surface of the bone but a deposition of calcium ions into the hydroxiapatite matrix (the net calcium introduction, which represent the difference between the total calcium into the treated bone and total calcium into untreated bone varied from 15.52±2.42·10−3g/0.5g bone to 44.30±3.50·10−3g/0.5g bone). The results suggest that iontophoresis could be used to accumulate calcium into different target tissues using the appropriate current system.

No change in bone-specific alkaline phosphatase activities in cultured rat osteoblastic cells under L-ascorbate and β-glycerophosphate-induced mineralization

Mineralization occurred both in fetal rat calvarial cells and UMR 106 osteoblastic cells when they were cultured in medium containing L-ascorbate and β-glycerophosphate as evidenced by von Kóssa staining as well as deposition of calcium ions and inorganic phosphate in the cells. When compared with corresponding non-mineralized cell cultures, both the mineralized cultures of calvarial cells and UMR 106 cells did not exhibit any change in intracellular bone-specific alkaline phosphatase activities which were measured by wheatgerm lectin precipitation method. Our results support the hypothesis that mineralization may not exert any direct negative feedback on matrix protein synthesis in osteoblasts during bone formation.