EQUIVALENCE BETWEEN SHORT-TIME BIPHASIC AND INCOMPRESSIBLE ELASTIC MATERIAL RESPONSES

PubMed Central

Ateshian, Gerard A.; Ellis, Benjamin J.; Weiss, Jeffrey A.

2009-01-01

Porous-permeable tissues have often been modeled using porous media theories such as the biphasic theory. This study examines the equivalence of the short-time biphasic and incompressible elastic responses for arbitrary deformations and constitutive relations from first principles. This equivalence is illustrated in problems of unconfined compression of a disk, and of articular contact under finite deformation, using two different constitutive relations for the solid matrix of cartilage, one of which accounts for the large disparity observed between the tensile and compressive moduli in this tissue. Demonstrating this equivalence under general conditions provides a rationale for using available finite element codes for incompressible elastic materials as a practical substitute for biphasic analyses, so long as only the short-time biphasic response is sought. In practice, an incompressible elastic analysis is representative of a biphasic analysis over the short-term response δt≪Δ2/‖C4‖||K||, where Δ is a characteristic dimension, C4 is the elasticity tensor and K is the hydraulic permeability tensor of the solid matrix. Certain notes of caution are provided with regard to implementation issues, particularly when finite element formulations of incompressible elasticity employ an uncoupled strain energy function consisting of additive deviatoric and volumetric components. PMID:17536908

Equivalence between short-time biphasic and incompressible elastic material responses.

PubMed

Ateshian, Gerard A; Ellis, Benjamin J; Weiss, Jeffrey A

2007-06-01

Porous-permeable tissues have often been modeled using porous media theories such as the biphasic theory. This study examines the equivalence of the short-time biphasic and incompressible elastic responses for arbitrary deformations and constitutive relations from first principles. This equivalence is illustrated in problems of unconfined compression of a disk, and of articular contact under finite deformation, using two different constitutive relations for the solid matrix of cartilage, one of which accounts for the large disparity observed between the tensile and compressive moduli in this tissue. Demonstrating this equivalence under general conditions provides a rationale for using available finite element codes for incompressible elastic materials as a practical substitute for biphasic analyses, so long as only the short-time biphasic response is sought. In practice, an incompressible elastic analysis is representative of a biphasic analysis over the short-term response deltat

A new biphasic osteoinductive calcium composite material with a negative Zeta potential for bone augmentation

PubMed Central

Smeets, Ralf; Kolk, Andreas; Gerressen, Marcus; Driemel, Oliver; Maciejewski, Oliver; Hermanns-Sachweh, Benita; Riediger, Dieter; Stein, Jamal M

2009-01-01

The aim of the present study was to analyze the osteogenic potential of a biphasic calcium composite material (BCC) with a negative surface charge for maxillary sinus floor augmentation. In a 61 year old patient, the BCC material was used in a bilateral sinus floor augmentation procedure. Six months postoperative, a bone sample was taken from the augmented regions before two titanium implants were inserted at each side. We analyzed bone neoformation by histology, bone density by computed tomography, and measured the activity of voltage-activated calcium currents of osteoblasts and surface charge effects. Control orthopantomograms were carried out five months after implant insertion. The BCC was biocompatible and replaced by new mineralized bone after being resorbed completely. The material demonstrated a negative surface charge (negative Zeta potential) which was found to be favorable for bone regeneration and osseointegration of dental implants. PMID:19523239

Augmenting in vitro osteogenesis of a glycine-arginine-glycine-aspartic-conjugated oxidized alginate-gelatin-biphasic calcium phosphate hydrogel composite and in vivo bone biogenesis through stem cell delivery.

PubMed

Linh, Nguyen Tb; Paul, Kallyanashis; Kim, Boram; Lee, Byong-Taek

2016-11-01

A functionally modified peptide-conjugated hydrogel system was fabricated with oxidized alginate/gelatin loaded with biphasic calcium phosphate to improve its biocompatibility and functionality. Sodium alginate was treated by controlled oxidation to transform the cis-diol group into an aldehyde group in a controlled manner, which was then conjugated to the amine terminus of glycine-arginine-glycine-aspartic. Oxidized alginate glycine-arginine-glycine-aspartic was then combined with gelatin-loaded biphasic calcium phosphate to form a hydrogel of composite oxidized alginate/gelatin/biphasic calcium phosphate that displayed enhanced human adipose stem cell adhesion, spreading and differentiation. 1 H nuclear magnetic resonance and electron spectroscopy for chemical analysis confirmed that the glycine-arginine-glycine-aspartic was successfully grafted to the oxidized alginate. Co-delivery of glycine-arginine-glycine-aspartic and human adipose stem cell in a hydrogel matrix was studied with the results indicating that hydrogel incorporated modified with glycine-arginine-glycine-aspartic and seeded with human adipose stem cell enhanced osteogenesis in vitro and bone formation in vivo. © The Author(s) 2016.

Surface Modification of Zirconia Substrate by Calcium Phosphate Particles Using Sol-Gel Method.

PubMed

Jin, So Dam; Um, Sang Cheol; Lee, Jong Kook

2015-08-01

Surface modification with a biphasic composition of hydroxyapatite (HA) and tricalcium phosphate (TCP) was performed on a zirconia substrate using a sol-gel method. An initial calcium phosphate sol was prepared by mixing a solution of Ca(NO3)2 · 4H20 and (C2H5O)3P(O), while both porous and dense zirconia were used as substrates. The sol-gel coating was performed using a spin coater. The coated porous zirconia substrate was re-sintered at 1350 °C 2 h, while coated dense zirconia substrate was heat-treated at 750 °C 1 h. The microstructure of the resultant HA/TCP coatings was found to be dependent on the type of zirconia substrate used. With porous zirconia as a starting substrate, numerous isolated calcium phosphate particles (TCP and HA) were uniformly dispersed on the surface, and the particle size and covered area were dependent on the viscosity of the calcium phosphate sol. Conversely, when dense zirconia was used as a starting substrate, a thick film of nano-sized HA particles was obtained after heat treatment, however, substantial agglomeration and cracking was also observed.

Probing the limit of magnesium uptake by β-tricalcium phosphate in biphasic mixtures formed from calcium deficient apatites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, P. Nandha; Mishra, Sandeep K.; Kannan, S., E-mail: para_kanna@yahoo.com

2015-11-15

A series of magnesium doped non-stoichiometric calcium deficient apatites were synthesized through an aqueous precipitation route. The resultant structural changes during heat treatment were investigated by X-ray diffraction, Raman and FT-IR spectroscopy and Rietveld refinement. The results confirmed the formation of biphasic mixtures comprising Ca{sub 10}(PO{sub 4}){sub 6}(OH){sub 2} and β-Ca{sub 3}(PO{sub 4}){sub 2} after heat treatment at 1000 °C with the preferential occupancy of Mg{sup 2+} at the crystal lattice of β-Ca{sub 3}(PO{sub 4}){sub 2}. The concentration of Mg{sup 2+} uptake in β-Ca{sub 3}(PO{sub 4}){sub 2} is limited till reaching the stoichiometric ratio of (Ca+Mg)/P=1.67 and beyond this stoichiometricmore » value [(Ca+Mg)/P>1.67], Mg{sup 2+} precipitates as Mg(OH){sub 2} and thereafter gets converted to MgO during heat treatment. Any kind of Mg{sup 2+} uptake in the crystal lattice of Ca{sub 10}(PO{sub 4}){sub 6}(OH){sub 2} is discarded from the investigation. - Highlights: • Aqueous co-precipitation of calcium deficient apatites with excess magnesium (Mg{sup 2+}) additions. • Heat treatments beyond 800 °C results in the formation of biphasic apatite mixtures. • Mg{sup 2+} gets accommodated at the β-Ca{sub 3}(PO{sub 4}){sub 2} lattice of biphasic mixtures. • Mg{sup 2+} additions exceeding stoichiometric value (Ca/P>1.67) results in its formation as MgO. • Mg{sup 2+} occupancy at β-Ca{sub 3}(PO{sub 4}){sub 2} lattice delays its allotropic conversion α-Ca{sub 3}(PO{sub 4}){sub 2} till 1350 °C.« less

A mixed-penalty biphasic finite element formulation incorporating viscous fluids and material interfaces.

PubMed

Chan, B; Donzelli, P S; Spilker, R L

2000-06-01

The fluid viscosity term of the fluid phase constitutive equation and the interface boundary conditions between biphasic, solid and fluid domains have been incorporated into a mixed-penalty finite element formulation of the linear biphasic theory for hydrated soft tissue. The finite element code can now model a single-phase viscous incompressible fluid, or a single-phase elastic solid, as limiting cases of a biphasic material. Interface boundary conditions allow the solution of problems involving combinations of biphasic, fluid and solid regions. To incorporate these conditions, the volume-weighted mixture velocity is introduced as a degree of freedom at interface nodes so that the kinematic continuity conditions are satisfied by conventional finite element assembly techniques. Results comparing our numerical method with an independent, analytic solution for the problem of Couette flow over rigid and deformable porous biphasic layers show that the finite element code accurately predicts the viscous fluid flows and deformation in the porous biphasic region. Thus, the analysis can be used to model the interface between synovial fluid and articular cartilage in diarthrodial joints. This is an important step toward modeling and understanding the mechanisms of joint lubrication and another step toward fully modeling the in vivo behavior of a diarthrodial joint.

Antibacterial activity evaluation of bioactive glass and biphasic calcium phosphate nanopowders mixtures

NASA Astrophysics Data System (ADS)

Nazemi, Zahra; Mehdikhani-Nahrkhalaji, Mehdi; Haghbin-Nazarpak, Masoumeh; Staji, Hamid; Kalani, Mohammad Mehdi

2016-12-01

The aim of this work was to evaluate the antibacterial activity of bioactive glass (BG) and biphasic calcium phosphate (BCP) nanopowders mixtures for the first time. 37S BG and BCP (50% HA-50% β-TCP) nanopowders were prepared via sol-gel technique. Characterization techniques such as X-ray diffraction, scanning electron microscopy, transition electron microscopy, and X-ray fluorescent. The antibacterial activity was studied using Escherichia coli and Salmonella typhi as gram-negative, and Staphylococcus aureus as gram-positive bacteria. The antibacterial effect of BG, BCP nanopowders, and their mixtures was evaluated at different concentrations. The 37S BG nanopowders showed minimum bactericidal concentration at 25 mg/ml. At broth concentrations below 300 mg/ml, BCP showed no antibacterial activity. BCP and BG nanopowders mixture (M2) with 60/40 ratio of BCP/BG showed noticeable antibacterial effect. It was concluded that BCP and 37S BG nanopowders mixture could be used as a good candidate for dental and orthopedic applications.

In Vitro Release and Bioavailability of Silybin from Micelle-Templated Porous Calcium Phosphate Microparticles.

PubMed

Zhu, Yuan; Wang, Miaomiao; Zhang, Ya; Zeng, Jin; Omari-Siaw, E; Yu, Jiangnan; Xu, Ximing

2016-10-01

Developing a promising carrier for the delivery of poorly water-soluble drugs, such as silybin, to improve oral absorption has become a very worthy of consideration. The goal of this study was to prepare a novel porous calcium phosphate microparticle using povidone-mixed micelles as template while evaluating its in vitro and in vivo properties with silybin as a model drug. The particle characterization, in vitro drug release behavior, and pharmacokinetic parameters of the prepared silybin-loaded calcium phosphate microparticle were investigated. The mean particle size was found to be 3.54 ± 0.32 μm with a rough surface porous structure. Additionally, the silybin-loaded calcium phosphate microparticle compared with the free silybin showed a prolonged 72-h release in vitro and a higher C max (418.5 ± 23.7 ng mL(-1)) with 167.5% oral relative bioavailability. A level A in vitro-in vivo correlation (IVIVC), established for the first time, demonstrated an excellent IVIVC of the formulated silybin in oral administration. In conclusion, this povidone-mixed micelle-based microparticle was successfully prepared to enhance the oral bioavailability of silybin. Therefore, application of this novel porous calcium phosphate microparticle holds a significant potential for the development of poorly water-soluble drugs.

A Study of BMP-2-Loaded Bipotential Electrolytic Complex around a Biphasic Calcium Phosphate-Derived (BCP) Scaffold for Repair of Large Segmental Bone Defect

PubMed Central

Paul, Kallyanashis; Padalhin, Andrew R.; Linh, Nguyen Thuy Ba; Kim, Boram; Sarkar, Swapan Kumar; Lee, Byong Taek

2016-01-01

A bipotential polyelectrolyte complex with biphasic calcium phosphate (BCP) powder dispersion provides an excellent option for protein adsorption and cell attachment and can facilitate enhanced bone regeneration. Application of the bipotential polyelectrolyte complex embedded in a spongy scaffold for faster healing of large segmental bone defects (LSBD) can be a promising endeavor in tissue engineering application. In the present study, a hollow scaffold suitable for segmental long bone replacement was fabricated by the sponge replica method applying the microwave sintering process. The fabricated scaffold was coated with calcium alginate at the shell surface, and genipin-crosslinked chitosan with biphasic calcium phosphate (BCP) dispersion was loaded at the central hollow core. The chitosan core was subsequently loaded with BMP-2. The electrolytic complex was characterized using SEM, porosity measurement, FTIR spectroscopy and BMP-2 release for 30 days. In vitro studies such as MTT, live/dead, cell proliferation and cell differentiation were performed. The scaffold was implanted into a 12 mm critical size defect of a rabbit radius. The efficacy of this complex is evaluated through an in vivo study, one and two month post implantation. BV/TV ratio for BMP-2 loaded sample was (42±1.76) higher compared with hollow BCP scaffold (32±0.225). PMID:27711142

Poly(lactide-co-glycolide acid)/biphasic calcium phosphate composite coating on a porous scaffold to deliver simvastatin for bone tissue engineering.

PubMed

Sadiasa, Alexander; Kim, Min Sung; Lee, Byong Taek

2013-09-01

In this study, simvastatin (SIM) drug incorporated poly(D,L-lactic-co-glycolide) (PLGA)/biphasic calcium phosphate (BCP) composite material (SPB) was coated on the BCP/ZrO2 (SPB-BCP/ZrO2) scaffold to enhance the mechanical and bioactive properties of the BCP/ZrO2 scaffold for bone engineering applications. The composite coating was prepared by combining different ratios of PLGA and BCP (1:2, 1:1, 2:1). After completion of the coating process, the compressive strength of the scaffolds was shown to increase with an increase in PLGA concentration from 8.5 ± 0.52 MPa for the SPB1-BCP/ZrO2 (1:2) to 11 ± 0.65 MPa for SPB3-BCP/ZrO2 (2:1) scaffolds when PLGA concentration was increased. Furthermore, the increase of PLGA in the coating composition corresponds to a decrease in porosity, degradation rate and weight loss of the scaffolds after 4 weeks. SIM release study demonstrated sustained release of the drug for the three kinds of scaffolds with improved biocompatibility. The increase of PLGA concentration also resulted in a lower release rate of SIM. Thus, the lower release rate of SIM brought upon by the increase of PLGA concentration further enhanced the performance of the scaffold in vitro making it a promising approach in the field of bone tissue regeneration.

The thermal stability of hydroxyapatite in biphasic calcium phosphate ceramics.

PubMed

Nilen, R W N; Richter, P W

2008-04-01

Biphasic calcium phosphate ceramics (BCP) comprising a mix of non-resorbable hydroxyapatite (HA) and resorbable beta-tricalcium phosphate (beta-TCP) are particularly suitable materials for synthetic bone substitute applications. In this study, HA synthesised by solid state reaction was mechanically mixed with beta-TCP, then sintered to form a suite of BCP materials with a wide range of HA/beta-TCP phase content ratios. The influence of sintering temperature and composition on the HA thermal stability was quantified by X-ray diffraction (XRD). The pre-sinter beta-TCP content was found to strongly affect the post-sinter HA/beta-TCP ratio by promoting the thermal decomposition of HA to beta-TCP, even at sintering temperatures as low as 850 degrees C. For BCP material with pre-sinter HA/beta-TCP = 40/60 wt%, approximately 80% of the HA decomposed to beta-TCP during sintering at 1000 degrees C. Furthermore, the HA content appeared to influence the reverse transformation of alpha-TCP to beta-TCP expected upon gradual cooling from sintering temperatures greater than 1125 degrees C. Because the HA/beta-TCP ratio dominantly determines the rate and extent of BCP resorption in vivo, the possible thermal decomposition of HA during BCP synthesis must be considered, particularly if high temperature treatments are involved.

Effect of Calcium-Infiltrated Hydroxyapatite Scaffolds on the Hematopoietic Fate of Human Umbilical Vein Endothelial Cells.

PubMed

Zhang, Qinghao; Gerlach, Jörg C; Schmelzer, Eva; Nettleship, Ian

2017-01-01

Foamed hydroxyapatite offers a three-dimensional scaffold for the development of bone constructs, mimicking perfectly the in vivo bone structure. In vivo, calcium release at the surface is assumed to provide a locally increased gradient supporting the maintenance of the hematopoietic stem cells niche. We fabricated hydroxyapatite scaffolds with high surface calcium concentration by infiltration, and used human umbilical vein endothelial cells (HUVECs) as a model to study the effects on hematopoietic lineage direction. HUVECs are umbilical vein-derived and thus possess progenitor characteristics, with a prospective potential to give rise to hematopoietic lineages. HUVECs were cultured for long term on three-dimensional porous hydroxyapatite scaffolds, which were either infiltrated biphasic foams or untreated. Controls were cultured in two-dimensional dishes. The release of calcium into culture medium was determined, and cells were analyzed for typical hematopoietic and endothelial gene expressions, surface markers by flow cytometry, and hematopoietic potential using colony-forming unit assays. Our results indicate that the biphasic foams promoted a hematopoietic lineage direction of HUVECs, suggesting an improved in vivo-like scaffold for hematopoietic bone tissue engineering. © 2017 S. Karger AG, Basel.

The Role of Magnesium Ion Substituted Biphasic Calcium Phosphate Spherical Micro-Scaffolds in Osteogenic Differentiation of Human Adipose Tissue-Derived Mesenchymal Stem Cells.

PubMed

Kim, Dong-Hyun; Shin, Keun-Koo; Jung, Jin Sup; Chun, Ho Hwan; Park, Seong Soo; Lee, Jong Kook; Park, Hong-Chae; Yoon, Seog-Young

2015-08-01

This study was investigated the role of magnesium (Mg2+) ion substituted biphasic calcium phosphate (Mg-BCP) spherical micro-scaffolds in osteogenic differentiation of human adipose tissue-derived mesenchymal stem cells (hAT-MSCs). Mg-BCP micro-scaffolds with spherical morphology were successfully prepared using in situ co-precipitation and spray drying atomization process. The in vitro cell proliferation and differentiation of hAT-MSCs were determined up to day 14. After in vitro biological tests, Mg-BCP micro-scaffolds with hAT-MSCs showed more enhanced osteogenicity than pure hAT-MSCs as control group by unique biodegradation of TCP phase and influence of substituted Mg2+ ion in biphasic nanostructure. Therefore, these results suggest that Mg-BCP micro-scaffolds promote osteogenic differentiation of hAT-MSCs.

Effect of calcium phosphate surface coating on bone ingrowth onto porous-surfaced titanium alloy implants in rabbit tibiae.

PubMed

Yang, Cheng

2002-04-01

The purpose of the present study was to determine whether calcium phosphate coating has a significant impact on bone ingrowth into a porous titanium implant. Porous-surfaced titanium alloy Ti-6Al-4V implants were prepared with or without the addition of a thin surface layer of calcium phosphate applied by sol-gel coating. Implants were placed into the tibiae of 16 rabbits. Implanted sites were allowed to heal for 2 weeks, after which specimens were retrieved for morphometric assessment using backscatter scanning electron microscopy. The data collected show that there is more extensive ingrowth into the porous regions of the calcium phosphate-coated implants than into the control implants. The weighted average ingrowth for the calcium phosphate-coated implants was 2.01, whereas that for the noncoated implants was 1.49; the difference is statistically significant (P <.01). The addition of a thin layer of calcium phosphate to these implants appears to promote a more extensive implant-to-bone interface by allowing the neck regions to become intimately ingrown with bone even after only 2 weeks of initial healing. Copyright 2002 American Association of Oral and Maxillofacial Surgeons

Injectable glycosaminoglycan-protein nano-complex in semi-interpenetrating networks: A biphasic hydrogel for hyaline cartilage regeneration.

PubMed

Radhakrishnan, Janani; Subramanian, Anuradha; Sethuraman, Swaminathan

2017-11-01

Articular hyaline cartilage regeneration remains challenging due to its less intrinsic reparability. The study develops injectable biphasic semi-interpenetrating polymer networks (SIPN) hydrogel impregnated with chondroitin sulfate (ChS) nanoparticles for functional cartilage restoration. ChS loaded zein nanoparticles (∼150nm) prepared by polyelectrolyte-protein complexation were interspersed into injectable SIPNs developed by blending alginate with poly(vinyl alcohol) and calcium crosslinking. The hydrogel exhibited interconnected porous microstructure (39.9±5.8μm pore diameter, 57.7±5.9% porosity), 92% swellability and >350Pa elastic modulus. Primary chondrocytes compatibility, chondrocyte-matrix interaction with cell-cell clustering and spheroidal morphology was demonstrated in ChS loaded hydrogel and long-term (42days) proliferation was also determined. Higher fold expression of cartilage-specific genes sox9, aggrecan and collagen-II was observed in ChS loaded hydrogel while exhibiting poor expression of collagen-I. Immunoblotting of aggregan and collagen II demonstrate favorable positive influence of ChS on chondrocytes. Thus, the injectable biphasic SIPNs could be promising composition-mimetic substitute for cartilage restoration at irregular defects. Copyright © 2017 Elsevier Ltd. All rights reserved.

Fabrication of porous low crystalline calcite block by carbonation of calcium hydroxide compact.

PubMed

Matsuya, Shigeki; Lin, Xin; Udoh, Koh-ichi; Nakagawa, Masaharu; Shimogoryo, Ryoji; Terada, Yoshihiro; Ishikawa, Kunio

2007-07-01

Calcium carbonate (CaCO(3)) has been widely used as a bone substitute material because of its excellent tissue response and good resorbability. In this experimental study, we propose a new method obtaining porous CaCO(3) monolith for an artificial bone substitute. In the method, calcium hydroxide compacts were exposed to carbon dioxide saturated with water vapor at room temperature. Carbonation completed within 3 days and calcite was the only product. The mechanical strength of CaCO(3) monolith increased with carbonation period and molding pressure. Development of mechanical strength proceeded through two steps; the first rapid increase by bonding with calcite layer formed at the surface of calcium hydroxide particles and the latter increase by the full conversion of calcium hydroxide to calcite. The latter process was thought to be controlled by the diffusion of CO(2) through micropores in the surface calcite layer. Porosity of calcite blocks thus prepared had 36.8-48.1% depending on molding pressure between 1 MPa and 5 MPa. We concluded that the present method may be useful for the preparation of bone substitutes or the preparation of source material for bone substitutes since this method succeeded in fabricating a low-crystalline, and thus a highly reactive, porous calcite block.

Structural and mechanical characterization of boron doped biphasic calcium phosphate produced by wet chemical method and subsequent thermal treatment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Albayrak, Onder, E-mail: albayrakonder@mersin.edu.tr

In the current study, boron doped biphasic calcium phosphate bioceramics consisting of a mixture of boron doped hydroxyapatite (BHA) and beta tricalcium phosphate (β-TCP) of varying BHA/β-TCP ratios were obtained after sintering stage. The effects of varying boron contents and different sintering temperatures on the BHA/β-TCP ratios and on the sinterability of the final products were investigated. Particle sizes and morphologies of the obtained precipitates were determined using SEM. XRD and FTIR investigation were conducted to detect the boron formation in the structure of HA and quantitative analysis was performed to determine the BHA/β-TCP ratio before and after sintering stage.more » In order to determine the sinterability of the obtained powders, pellets were prepared and sintered; the rates of densification were calculated and obtained results were correlated by SEM images. Also Vickers microhardness values of the sintered samples were determined. The experimental results verified that boron doped hydroxyapatite powders were obtained after sintering stage and the structure consists of a mixture of BHA and β-TCP. As the boron content used in the precipitation stage increases, β-TCP content of the BHA/β-TCP ratio increases but sinterability, density and microhardness deteriorate. As the sintering temperature increases, β-TCP content, density and microhardness of the samples increase and sinterability improves. - Highlights: • This is the first paper about boron doped biphasic calcium phosphate bioceramics. • Boron doping affects the structural and mechanical properties. • BHA/β-TCP ratio can be adjustable with boron content and sintering temperature.« less

Hydroxyapatite/polylactide biphasic combination scaffold loaded with dexamethasone for bone regeneration.

PubMed

Son, Jun-Sik; Kim, Su-Gwan; Oh, Ji-Su; Appleford, Mark; Oh, Sunho; Ong, Joo L; Lee, Kyu-Bok

2011-12-15

This study presents a novel design of a ceramic/polymer biphasic combination scaffold that mimics natural bone structures and is used as a bone graft substitute. To mimic the natural bone structures, the outside cortical-like shells were composed of porous hydroxyapatite (HA) with a hollow interior using a polymeric template-coating technique; the inner trabecular-like core consisted of porous poly(D,L-lactic acid) (PLA) that was loaded with dexamethasone (DEX) and was directly produced using a particle leaching/gas forming technique to create the inner diameter of the HA scaffold. It was observed that the HA and PLA parts of the fabricated HA/PLA biphasic scaffold contained open and interconnected pore structures, and the boundary between both parts was tightly connected without any gaps. It was found that the structure of the combination scaffold was analogous to that of natural bone based on micro-computed tomography analysis. Additionally, the dense, uniform apatite layer was formed on the surface of the HA/PLA biphasic scaffold through a biomimetic process, and DEX was successfully released from the PLA of the biphasic scaffold over a 1-month period. This release caused human embryonic palatal mesenchyme cells to proliferate, differentiate, produce ECM, and form tissue in vitro. Therefore, it was concluded that this functionally graded scaffold is similar to natural bone and represents a potential bone-substitute material. Copyright © 2011 Wiley Periodicals, Inc.

Influence of strontium on the synthesis and surface properties of biphasic calcium phosphate (BCP) bioceramics.

PubMed

Kanchana, Ponnusamy; Sekar, Chinnathambi

2010-01-01

Biphasic calcium phosphate (BCP) ceramics are suitable for synthetic bone applications. The strontium substituted calcium phosphate ceramics have potential for use in orthopedic surgeries. Aim of the present work is to introduce strontium into BCP (composed of hydroxyapatite and tricalcium phosphate) ceramics and to study their bioactivity and mechanical properties. BCP ceramics have been synthesized at room temperature under the physiological pH of 7.4 by gel method in the presence of strontium (5, 10 M %). The appropriate choice of anhydrous CaCl₂ as precursor solution has promoted the formation of BCP instead of pure HA for CaCl₂.2H₂O. Powder X-ray diffraction analysis confirmed the formation of BCP with different HA and ß -TCP ratios depending upon the Sr content. The presence of Sr has reduced the nucleation and growth rate of BCP when compared to pure system. The SEM micrographs showed that the microstructural morphology of BCP changes from fibrous to platelet. Nanoindentation studies indicate a significant decrease in the hardness and elastic modulus values of BCP ceramics due to Sr doping. In vitro bioactivity study has revealed the formation of apatite layer on the Sr doped BCP samples and the doping enhanced its bioactivity.

Influence of surface porosity and pH on bacterial adherence to hydroxyapatite and biphasic calcium phosphate bioceramics.

PubMed

Kinnari, Teemu J; Esteban, Jaime; Martin-de-Hijas, Nieves Z; Sánchez-Muñoz, Orlando; Sánchez-Salcedo, Sandra; Colilla, Montserrat; Vallet-Regí, María; Gomez-Barrena, Enrique

2009-01-01

Hydroxyapatite (HA) and biphasic calcium phosphate (BCP) ceramic materials are widely employed as bone substitutes due to their porous and osteoconductive structure. Their porosity and the lowering of surrounding pH as a result of surgical trauma may, however, predispose these materials to bacterial infections. For this reason, the influence of porosity and pH on the adherence of common Gram-positive bacteria to the surfaces of these materials requires investigation. Mercury intrusion porosimetry measurements revealed that the pore size distribution of both bioceramics had, on a logarithmic scale, a sinusoidal frequency distribution ranging from 50 to 300 nm, with a mean pore diameter of 200 nm. Moreover, total porosity was 20 % for HA and 50 % for BCP. Adherence of Staphylococcus aureus and Staphylococcus epidermidis was studied at a physiological pH of 7.4 and at a pH simulating bone infection of 6.8. Moreover, the effect of pH on the zeta potential of HA, BCP and of both staphylococci was evaluated. Results showed that when pH decreased from 7.4 to 6.8, the adherence of both staphylococci to HA and BCP surfaces decreased significantly, although at the same time the negative zeta-potential values of the ceramic surfaces and both bacteria diminished. At both pH values, the number of S. aureus adhered to the HA surface appeared to be lower than that for BCP. A decrease in pH to 6.8 reduced the adherence of both bacterial species (mean 57 %). This study provides evidence that HA and BCP ceramics do not have pores sufficiently large to allow the internalization of staphylococci. Their anti-adherent properties seemed to improve when pH value decreased, suggesting that HA and BCP bioceramics are not compromised upon orthopaedic use.

Development and Characterization of Biphasic Hydroxyapatite/β-TCP Cements

PubMed Central

Gallinetti, Sara; Canal, Cristina; Ginebra, Maria-Pau; Ferreira, J

2014-01-01

Biphasic calcium phosphate bioceramics composed of hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP) have relevant properties as synthetic bone grafts, such as tunable resorption, bioactivity, and intrinsic osteoinduction. However, they have some limitations associated to their condition of high-temperature ceramics. In this work self-setting Biphasic Calcium Phosphate Cements (BCPCs) with different HA/β-TCP ratios were obtained from self-setting α-TCP/β-TCP pastes. The strategy used allowed synthesizing BCPCs with modulated composition, compressive strength, and specific surface area. Due to its higher solubility, α-TCP was fully hydrolyzed to a calcium-deficient HA (CDHA), whereas β-TCP remained unreacted and completely embedded in the CDHA matrix. Increasing amounts of the non-reacting β-TCP phase resulted in a linear decrease of the compressive strength, in association to the decreasing amount of precipitated HA crystals, which are responsible for the mechanical consolidation of apatitic cements. Ca2+ release and degradation in acidic medium was similar in all the BCPCs within the timeframe studied, although differences might be expected in longer term studies once β-TCP, the more soluble phase was exposed to the surrounding media. PMID:25866411

Development and Characterization of Biphasic Hydroxyapatite/β-TCP Cements.

PubMed

Gallinetti, Sara; Canal, Cristina; Ginebra, Maria-Pau; Ferreira, J

2014-04-01

Biphasic calcium phosphate bioceramics composed of hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP) have relevant properties as synthetic bone grafts, such as tunable resorption, bioactivity, and intrinsic osteoinduction. However, they have some limitations associated to their condition of high-temperature ceramics. In this work self-setting Biphasic Calcium Phosphate Cements (BCPCs) with different HA/β-TCP ratios were obtained from self-setting α-TCP/β-TCP pastes. The strategy used allowed synthesizing BCPCs with modulated composition, compressive strength, and specific surface area. Due to its higher solubility, α-TCP was fully hydrolyzed to a calcium-deficient HA (CDHA), whereas β-TCP remained unreacted and completely embedded in the CDHA matrix. Increasing amounts of the non-reacting β-TCP phase resulted in a linear decrease of the compressive strength, in association to the decreasing amount of precipitated HA crystals, which are responsible for the mechanical consolidation of apatitic cements. Ca 2+ release and degradation in acidic medium was similar in all the BCPCs within the timeframe studied, although differences might be expected in longer term studies once β-TCP, the more soluble phase was exposed to the surrounding media.

Sol gel-derived hydroxyapatite films over porous calcium polyphosphate substrates for improved tissue engineering of osteochondral-like constructs.

PubMed

Lee, Whitaik David; Gawri, Rahul; Pilliar, Robert M; Stanford, William L; Kandel, Rita A

2017-10-15

Integration of in vitro-formed cartilage on a suitable substrate to form tissue-engineered implants for osteochondral defect repair is a considerable challenge. In healthy cartilage, a zone of calcified cartilage (ZCC) acts as an intermediary for mechanical force transfer from soft to hard tissue, as well as an effective interlocking structure to better resist interfacial shear forces. We have developed biphasic constructs that consist of scaffold-free cartilage tissue grown in vitro on, and interdigitated with, porous calcium polyphosphate (CPP) substrates. However, as CPP degrades, it releases inorganic polyphosphates (polyP) that can inhibit local mineralization, thereby preventing the formation of a ZCC at the interface. Thus, we hypothesize that coating CPP substrate with a layer of hydroxyapatite (HA) might prevent or limit this polyP release. To investigate this we tested both inorganic or organic sol-gel processing methods, asa barrier coating on CPP substrate to inhibit polyP release. Both types of coating supported the formation of ZCC in direct contact with the substrate, however the ZCC appeared more continuous in the tissue formed on the organic HA sol gel coated CPP. Tissues formed on coated substrates accumulated comparable quantities of extracellular matrix and mineral, but tissues formed on organic sol-gel (OSG)-coated substrates accumulated less polyP than tissues formed on inorganic sol-gel (ISG)-coated substrates. Constructs formed with OSG-coated CPP substrates had greater interfacial shear strength than those formed with ISG-coated and non-coated substrates. These results suggest that the OSG coating method can modify the location and distribution of ZCC and can be used to improve the mechanical integrity of tissue-engineered constructs formed on porous CPP substrates. Articular cartilage interfaces with bone through a zone of calcified cartilage. This study describes a method to generate an "osteochondral-like" implant that mimics this

Laser engineered multilayer coating of biphasic calcium phosphate/titanium nanocomposite on metal substrates.

PubMed

Zhang, Martin Yi; Ye, Chang; Erasquin, Uriel Joseph; Huynh, Toan; Cai, Chengzhi; Cheng, Gary J

2011-02-01

In this work, laser coating of biphasic calcium phosphate/titanium (BCP/Ti) nanocomposite on Ti-6Al-4 V substrates was developed. A continuous wave neodymium-doped yttrium aluminium garnet (Nd:YAG) laser was used to form a robust multilayer of BCP/Ti nanocomposite starting from hydroxyapatite and titanium nanoparticles. In this process, low power coating is realized because of the strong laser-nanoparticle interaction and good sinterability of nanosized titanium. To guide the optimization of laser processing conditions for the coating process, a multiphysics model coupling electromagnetic module with heat transfer module was developed. This model was validated by laser coating experiments. Important features of the coated samples, including microstructures, chemical compositions, and interfacial bonding strength, were characterized. We found that a multilayer of BCP, consisting of 72% hydroxyapatite (HA) and 28% beta-tricalcium phosphate (β-TCP), and titanium nanocomposite was formed on Ti-6Al-4 V substrates. Significantly, the coating/substrate interfacial bonding strength was found to be two times higher than that of the commercial plasma sprayed coatings. Preliminary cell culture studies showed that the resultant BCP/Ti nanocomposite coating supported the adhesion and proliferation of osteoblast-like UMR-106 cells.

Toward Highly Efficient Electrocatalyst for Li-O2 Batteries Using Biphasic N-Doping Cobalt@Graphene Multiple-Capsule Heterostructures.

PubMed

Tan, Guoqiang; Chong, Lina; Amine, Rachid; Lu, Jun; Liu, Cong; Yuan, Yifei; Wen, Jianguo; He, Kun; Bi, Xuanxuan; Guo, Yuanyuan; Wang, Hsien-Hau; Shahbazian-Yassar, Reza; Al Hallaj, Said; Miller, Dean J; Liu, Dijia; Amine, Khalil

2017-05-10

For the promotion of lithium-oxygen batteries available for practical applications, the development of advanced cathode catalysts with low-cost, high activity, and stable structural properties is demanded. Such development is rooted on certain intelligent catalyst-electrode design that fundamentally facilitates electronic and ionic transport and improves oxygen diffusivity in a porous environment. Here we design a biphasic nitrogen-doped cobalt@graphene multiple-capsule heterostructure, combined with a flexible, stable porous electrode architecture, and apply it as promising cathodes for lithium-oxygen cells. The biphasic nitrogen-doping feature improves the electric conductivity and catalytic activity; the multiple-nanocapsule configuration makes high/uniform electroactive zones possible; furthermore, the colander-like porous electrode facilitates the oxygen diffusion, catalytic reaction, and stable deposition of discharge products. As a result, the electrode exhibits much improved electrocatalytic properties associated with unique morphologies of electrochemically grown lithium peroxides.

Facile synthesis of biphasic calcium phosphate microspheres with engineered surface topography for controlled delivery of drugs and proteins.

PubMed

Zarkesh, Ibrahim; Ghanian, Mohammad Hossein; Azami, Mahmoud; Bagheri, Fatemeh; Baharvand, Hossein; Mohammadi, Javad; Eslaminejad, Mohamadreza Baghaban

2017-09-01

Biphasic calcium phosphate (BCP) microspheres are of great interest due to their high stability and osteoinductive properties at specific compositions. However, the need for optimal performance at a unique composition limits their flexibility for tuning drug release by modulation of bulk properties and presents the question of engineering surface topography as an alternative. It is necessary to have a facile method to control surface topography at a defined bulk composition. Here, we have produced BCP microspheres with different surface topographies that have the capability to be used as tunable drug release systems. We synthesized calcium deficient hydroxyapatite (CDHA) microparticles by precipitating calcium and phosphate ions onto ethylenediaminetetraacetic acid (EDTA) templates. The morphology and surface topography of CDHA microparticles were controlled using process parameters, which governed nucleation and growth. These parameters included template concentration, heat rate, and stirring speed. Under low heat rate and static conditions, we could obtain spherical microparticles with long and short nanosheets on their surfaces at low and high EDTA concentrations, respectively. These nanostructured microspheres were subsequently crystallized by thermal treatment to produce EDTA-free BCP microspheres with intact morphology. These biocompatible BCP microspheres were highly effective in loading and prolonged release of both small molecule [dexamethasone (Dex)] and protein [bovine serum albumin (BSA)] models. This strategy has enabled us to control the surface topography of BCP microspheres at defined compositions and holds tremendous promise for drug delivery and tissue engineering applications. Copyright © 2017 Elsevier B.V. All rights reserved.

Toward highly efficient electrocatalyst for Li–O 2 batteries using biphasic N-doping cobalt@graphene multiple-capsule heterostructures

DOE PAGES

Tan, Guoqiang; Chong, Lina; Amine, Rachid; ...

2017-04-12

To promote lithium-oxygen batteries available for practical applications, the development of advanced cathode catalysts with low-cost, high activity and stable structural properties is demanded. Such development is rooted on certain intelligent catalyst-electrode design that fundamentally facilitates electronic and ionic transport, and improves oxygen diffusivity in a porous environment. Here we design a biphasic nitrogen-doped cobalt@graphene multiple-capsule heterostructure, combined with a flexible, stable porous electrode architecture, and apply it as promising cathodes for lithium-oxygen cells. The biphasic nitrogen-doping feature improves the electric conductivity and catalytic activity; the multiple-nanocapsule configuration makes high/uniform electro-active zones possible; furthermore, the colander-like porous electrode facilitates themore » oxygen diffusion, catalytic reaction, and stable deposition of discharge products. Finally, the electrode exhibits much improved electrocatalytic properties associated with unique morphologies of electrochemically grown lithium peroxides.« less

Toward highly efficient electrocatalyst for Li–O 2 batteries using biphasic N-doping cobalt@graphene multiple-capsule heterostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tan, Guoqiang; Chong, Lina; Amine, Rachid

To promote lithium-oxygen batteries available for practical applications, the development of advanced cathode catalysts with low-cost, high activity and stable structural properties is demanded. Such development is rooted on certain intelligent catalyst-electrode design that fundamentally facilitates electronic and ionic transport, and improves oxygen diffusivity in a porous environment. Here we design a biphasic nitrogen-doped cobalt@graphene multiple-capsule heterostructure, combined with a flexible, stable porous electrode architecture, and apply it as promising cathodes for lithium-oxygen cells. The biphasic nitrogen-doping feature improves the electric conductivity and catalytic activity; the multiple-nanocapsule configuration makes high/uniform electro-active zones possible; furthermore, the colander-like porous electrode facilitates themore » oxygen diffusion, catalytic reaction, and stable deposition of discharge products. Finally, the electrode exhibits much improved electrocatalytic properties associated with unique morphologies of electrochemically grown lithium peroxides.« less

A New Biphasic Dicalcium Silicate Bone Cement Implant.

PubMed

Zuleta, Fausto; Murciano, Angel; Gehrke, Sergio A; Maté-Sánchez de Val, José E; Calvo-Guirado, José L; De Aza, Piedad N

2017-07-06

This study aimed to investigate the processing parameters and biocompatibility of a novel biphasic dicalcium silicate (C₂S) cement. Biphasic α´ L + β-C₂S ss was synthesized by solid-state processing, and was used as a raw material to prepare the cement. In vitro bioactivity and biocompatibility studies were assessed by soaking the cement samples in simulated body fluid (SBF) and human adipose stem cell cultures. Two critical-sized defects of 6 mm Ø were created in 15 NZ tibias. A porous cement made of the high temperature forms of C₂S, with a low phosphorous substitution level, was produced. An apatite-like layer covered the cement's surface after soaking in SBF. The cell attachment test showed that α´ L + β-C₂S ss supported cells sticking and spreading after 24 h of culture. The cement paste (55.86 ± 0.23) obtained higher bone-to-implant contact (BIC) percentage values (better quality, closer contact) in the histomorphometric analysis, and defect closure was significant compared to the control group (plastic). The residual material volume of the porous cement was 35.42 ± 2.08% of the initial value. The highest BIC and bone formation percentages were obtained on day 60. These results suggest that the cement paste is advantageous for initial bone regeneration.

A New Biphasic Dicalcium Silicate Bone Cement Implant

PubMed Central

Murciano, Angel; Maté-Sánchez de Val, José E.

2017-01-01

This study aimed to investigate the processing parameters and biocompatibility of a novel biphasic dicalcium silicate (C2S) cement. Biphasic α´L + β-C2Sss was synthesized by solid-state processing, and was used as a raw material to prepare the cement. In vitro bioactivity and biocompatibility studies were assessed by soaking the cement samples in simulated body fluid (SBF) and human adipose stem cell cultures. Two critical-sized defects of 6 mm Ø were created in 15 NZ tibias. A porous cement made of the high temperature forms of C2S, with a low phosphorous substitution level, was produced. An apatite-like layer covered the cement’s surface after soaking in SBF. The cell attachment test showed that α´L + β-C2Sss supported cells sticking and spreading after 24 h of culture. The cement paste (55.86 ± 0.23) obtained higher bone-to-implant contact (BIC) percentage values (better quality, closer contact) in the histomorphometric analysis, and defect closure was significant compared to the control group (plastic). The residual material volume of the porous cement was 35.42 ± 2.08% of the initial value. The highest BIC and bone formation percentages were obtained on day 60. These results suggest that the cement paste is advantageous for initial bone regeneration. PMID:28773119

Investigation of structural resorption behavior of biphasic bioceramics with help of gravimetry, μCT, SEM, and XRD.

PubMed

de Wild, Michael; Amacher, Fabienne; Bradbury, Christopher R; Molenberg, Aart

2016-04-01

Resorbable bone substitute materials are widely used for bone augmentation after tumor resection, parallel to implant placement, or in critical size bone defects. In this study, the structural dissolution of a biphasic calcium phosphate bone substitute material with a hydroxyapatite (HA)/tricalcium phosphate (β-TCP) ratio of 60/40 was investigated by repeatedly placing porous blocks in EDTA solution at 37 °C. At several time points, the blocks were investigated by SEM, µCT, and gravimetry. It was found that always complete 2-3 µm sized grains were removed from the structure and that the β-TCP is dissolved more rapidly. This selective dissolution of the β-TCP grains was confirmed by XRD measurements. The blocks were eroded from the outside toward the center. The structure remained mechanically stable because the central part showed a delayed degradation and because the slower dissolving HA grains preserved the integrity of the structure. © 2015 Wiley Periodicals, Inc.

Odontogenic Differentiation of Human Dental Pulp Stem Cells Stimulated by the Calcium Phosphate Porous Granules

PubMed Central

Nam, Sunyoung; Won, Jong-Eun; Kim, Cheol-Hwan; Kim, Hae-Won

2011-01-01

Effects of three-dimensional (3D) calcium phosphate (CaP) porous granules on the growth and odontogenic differentiation of human dental pulp stem cells (hDPSCs) were examined for dental tissue engineering. hDPSCs isolated from adult human dental pulps were cultured for 3-4 passages, and populated on porous granules. Cell growth on the culture dish showed an ongoing increase for up to 21 days, whereas the growth on the 3D granules decreased after 14 days. This reduction in proliferative potential on the 3D granules was more conspicuous under the osteogenic medium conditions, indicating that the 3D granules may induce the odontogenic differentiation of hDPSCs. Differentiation behavior on the 3D granules was confirmed by the increased alkaline phosphatase activity, up-regulation of odontoblast-specific genes, including dentin sialophosphoprotein (DSPP) and dentin matrix protein 1 (DMP1) by quantitative polymerase chain reaction, and greater level of dentin sialoprotein synthesis by western blot. Moreover, the cellular mineralization, as assessed by Alizarin red S and calcium quantification, was significantly higher in the 3D CaP granules than in the culture dish. Taken all, the 3D CaP porous granules should be useful for dental tissue engineering in combination with hDPSCs by providing favorable 3D substrate conditions for cell growth and odontogenic development. PMID:21772958

Production of porous Calcium Phosphate (CaP) ceramics with aligned pores using ceramic/camphene-based co-extrusion.

PubMed

Choi, Won-Young; Kim, Hyoun-Ee; Moon, Young-Wook; Shin, Kwan-Ha; Koh, Young-Hag

2015-01-01

Calcium phosphate (CaP) ceramics are one of the most valuable biomaterials for uses as the bone scaffold owing to their outstanding biocompatability, bioactivity, and biodegradation nature. In particular, these materials with an open porous structure can stimulate bone ingrowth into their 3-dimensionally interconnected pores. However, the creation of pores in bulk materials would inevitably cause a severe reduction in mechanical properties. Thus, it is a challenge to explore new ways of improving the mechanical properties of porous CaP scaffolds without scarifying their high porosity. Porous CaP ceramic scaffolds with aligned pores were successfully produced using ceramic/camphene-based co-extrusion. This aligned porous structure allowed for the achievement of high compressive strength when tested parallel to the direction of aligned pores. In addition, the overall porosity and mechanical properties of the aligned porous CaP ceramic scaffolds could be tailored simply by adjusting the initial CaP content in the CaP/camphene slurry. The porous CaP scaffolds showed excellent in vitro biocompatibility, suggesting their potential as the bone scaffold. Aligned porous CaP ceramic scaffolds with considerably enhanced mechanical properties and tailorable porosity would find very useful applications as the bone scaffold.

Probing the limit of magnesium uptake by β-tricalcium phosphate in biphasic mixtures formed from calcium deficient apatites

NASA Astrophysics Data System (ADS)

Kumar, P. Nandha; Mishra, Sandeep K.; Kannan, S.

2015-11-01

A series of magnesium doped non-stoichiometric calcium deficient apatites were synthesized through an aqueous precipitation route. The resultant structural changes during heat treatment were investigated by X-ray diffraction, Raman and FT-IR spectroscopy and Rietveld refinement. The results confirmed the formation of biphasic mixtures comprising Ca10(PO4)6(OH)2 and β-Ca3(PO4)2 after heat treatment at 1000 °C with the preferential occupancy of Mg2+ at the crystal lattice of β-Ca3(PO4)2. The concentration of Mg2+ uptake in β-Ca3(PO4)2 is limited till reaching the stoichiometric ratio of (Ca+Mg)/P=1.67 and beyond this stoichiometric value [(Ca+Mg)/P>1.67], Mg2+ precipitates as Mg(OH)2 and thereafter gets converted to MgO during heat treatment. Any kind of Mg2+ uptake in the crystal lattice of Ca10(PO4)6(OH)2 is discarded from the investigation.

Multi-layer porous fiber-reinforced composites for implants: in vitro calcium phosphate formation in the presence of bioactive glass.

PubMed

Nganga, Sara; Zhang, Di; Moritz, Niko; Vallittu, Pekka K; Hupa, Leena

2012-11-01

Glass-fiber-reinforced composites (FRCs), based on bifunctional methacrylate resin, have recently shown their potential for use as durable cranioplasty, orthopedic and oral implants. In this study we suggest a multi-component sandwich implant structure with (i) outer layers out of porous FRC, which interface the cortical bone, and (ii) inner layers encompassing bioactive glass granules, which interface with the cancellous bone. The capability of Bioglass(®) 45S5 granules (100-250μm) to induce calcium phosphate formation on the surface of the FRC was explored by immersing the porous FRC-Bioglass laminates in simulated body fluid (SBF) for up to 28d. In both static (agitated) and dynamic conditions, bioactive glass granules induced precipitation of calcium phosphate at the laminate surfaces as confirmed by scanning electron microscopy. The proposed dynamic flow system is useful for the in vitro simulation of bone-like apatite formation on various new porous implant designs containing bioactive glass and implant material degradation. Copyright © 2012 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Calcium binding properties of calcium dependent protein kinase 1 (CaCDPK1) from Cicer arietinum.

PubMed

Dixit, Ajay Kumar; Jayabaskaran, Chelliah

2015-05-01

Calcium plays a crucial role as a secondary messenger in all aspects of plant growth, development and survival. Calcium dependent protein kinases (CDPKs) are the major calcium decoders, which couple the changes in calcium level to an appropriate physiological response. The mechanism by which calcium regulates CDPK protein is not well understood. In this study, we investigated the interactions of Ca(2+) ions with the CDPK1 isoform of Cicer arietinum (CaCDPK1) using a combination of biophysical tools. CaCDPK1 has four different EF hands as predicted by protein sequence analysis. The fluorescence emission spectrum of CaCDPK1 showed quenching with a 5 nm red shift upon addition of calcium, indicating conformational changes in the tertiary structure. The plot of changes in intensity against calcium concentrations showed a biphasic curve with binding constants of 1.29 μM and 120 μM indicating two kinds of binding sites. Isothermal calorimetric (ITC) titration with CaCl2 also showed a biphasic curve with two binding constants of 0.027 μM and 1.7 μM. Circular dichroism (CD) spectra showed two prominent peaks at 208 and 222 nm indicating that CaCDPK1 is a α-helical rich protein. Calcium binding further increased the α-helical content of CaCDPK1 from 75 to 81%. Addition of calcium to CaCDPK1 also increased fluorescence of 8-anilinonaphthalene-1-sulfonic acid (ANS) indicating exposure of hydrophobic surfaces. Thus, on the whole this study provides evidence for calcium induced conformational changes, exposure of hydrophobic surfaces and heterogeneity of EF hands in CaCDPK1. Copyright © 2015 Elsevier GmbH. All rights reserved.

Micropore-induced Capillarity Enhances Bone Distribution in vivo in Biphasic Calcium Phosphate Scaffolds

PubMed Central

Rustom, Laurence E.; Boudou, Thomas; Lou, Siyu; Pignot-Paintrand, Isabelle; Nemke, Brett W.; Lu, Yan; Markel, Mark D.; Picart, Catherine; Wagoner Johnson, Amy J.

2016-01-01

The increasing demand for bone repair solutions calls for the development of efficacious bone scaffolds. Biphasic calcium phosphate (BCP) scaffolds with both macropores and micropores (MP) have improved healing compared to those with macropores and no micropores (NMP), but the role of micropores is unclear. Here, we evaluate capillarity induced by micropores as a mechanism that can affect bone growth in vivo. Three groups of cylindrical scaffolds were implanted in pig mandibles for three weeks: MP were implanted either dry (MP-Dry), or after submersion in phosphate buffered saline, which fills pores with fluid and therefore suppresses micropore-induced capillarity (MP-Wet); NMP were implanted dry. The amount and distribution of bone in the scaffolds were quantified using micro-computed tomography. MP-Dry had a more homogeneous bone distribution than MP-Wet, although the average bone volume fraction, BVF¯, was not significantly different for these two groups (0.45±0.03 and 0.37±0.03, respectively). There was no significant difference in the radial bone distribution of NMP and MP-Wet, but the BVF¯ of NMP was significantly lower among the three groups (0.25±0.02). These results suggest that micropore-induced capillarity enhances bone regeneration by improving the homogeneity of bone distribution in BCP scaffolds. The explicit design and use of capillarity in bone scaffolds may lead to more effective treatments of large and complex bone defects. PMID:27544807

Effect of filler content on mechanical and dynamic mechanical properties of particulate biphasic calcium phosphate--polylactide composites.

PubMed

Bleach, N C; Nazhat, S N; Tanner, K E; Kellomäki, M; Törmälä, P

2002-04-01

A bioabsorbable self-reinforced polylactide/biphasic calcium phosphate (BCP) composite is being developed for fracture fixation plates. One manufacturing route is to produce preimpregnated sheets by pulling polylactide (PLA) fibres through a suspension of BCP filler in a PLA solution and compression moulding the prepreg to the desired shape. To aid understanding of the process, interactions between the matrix and filler were investigated. Composite films containing 0-0.25 volume fraction filler, produced by solvent casting, were analysed using SEM, tensile testing and dynamic mechanical analysis (DMA). Homogeneous films could be made, although some particle agglomeration was seen at higher filler volume fractions. As the filler content increased, the failure strain decreased due to a reduction in the amount of ductile polymer present and the ultimate tensile strength (UTS) decreased because of agglomeration and void formation at higher filler content. The matrix glass transition temperature increased due to polymer chain adsorption and immobilization onto the BCP particles. Complex damping mechanisms, such as particle-particle agglomeration, may exist at the higher BCP volume fractions.

Toward Highly Efficient Electrocatalyst for Li–O 2 Batteries Using Biphasic N-Doping Cobalt@Graphene Multiple-Capsule Heterostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tan, Guoqiang; Chong, Lina; Amine, Rachid

For the promotion of lithium oxygen batteries available for :practical applications, the development of advanced cathode catalysts with low-high activity, and stable structural properties is demanded. Such development is rooted on certain intelligent catalyst-electrode design that fundamentally facilitates electronic and ionic transport and improves oxygen diffusivity in a porous environment. Here we design a biphasic nitrogen-doped cobalt@grapbene Multiple-capsule heterostructure, combined with a flexible, stable porous electrode architecture, and apply it as promising cathodes for lithium oxygen cells. 'The biphasic nitrogen-doping feature improves the electric conductivity and catalytic activity; the multiple-nanocapsule configuration makes high/uniform electroactive zones possible; furthermore the colander-like porousmore » electrode facilitates the oxygen diffusion, catalytic reaction,and stable deposition of discharge products. As a result, the electrode exhibits much improved electrocatalytic properties associated with unique morphologies of electrochemically grown lithium peroxides.« less

Biphasic regulation of intracellular calcium by gemfibrozil contributes to inhibiting L6 myoblast differentiation: implications for clinical myotoxicity.

PubMed

Liu, Aiming; Yang, Julin; Gonzalez, Frank J; Cheng, Gary Q; Dai, Renke

2011-02-18

Gemfibrozil is the most myotoxic fibrate drug commonly used for dyslipidemia, but the mechanism is poorly understood. The current study revealed that gemfibrozil inhibits myoblast differentiation through the regulation of intracellular calcium ([Ca(2+)]i) as revealed in L6 myoblasts by use of laser scan confocal microscopy and flow cytometry using Fluo-4 AM as a probe. Gemfibrozil at 20-400 μM, could regulate [Ca(2+)]i in L6 cells in a biphasic manner, and sustained reduction was observed when the concentration reached 200 μM. Inhibition of L6 differentiation by gemfibrozil was concentration-dependent with maximal effect noted between 200 and 400 μM, as indicated by creatine kinase activities and the differentiation index, respectively. In differentiating L6 myoblasts, gemfibrozil at concentrations below 400 μM led to no significant signs of apoptosis or cytotoxicity, whereas differentiation, inhibited by 200 μM gemfibrozil, was only partially recovered. A good correlation was noted between gemfibrozil concentrations that regulate [Ca(2+)]i and inhibit L6 myoblasts differentiation, and both are within the range of total serum concentrations found in the clinic. These data suggest a potential pharmacodynamic effect of gemfibrozil on myogenesis as a warning sign, in addition to the complex pharmacokinetic interactions. It is also noteworthy that mobilization of [Ca(2+)]i by gemfibrozil may trigger complex biological responses besides myocyte differentiation. Information revealed in this study explores the mechanism of gemfibrozil-induced myotoxicity through the regulation of intracellular calcium.

Micropore-induced capillarity enhances bone distribution in vivo in biphasic calcium phosphate scaffolds.

PubMed

Rustom, Laurence E; Boudou, Thomas; Lou, Siyu; Pignot-Paintrand, Isabelle; Nemke, Brett W; Lu, Yan; Markel, Mark D; Picart, Catherine; Wagoner Johnson, Amy J

2016-10-15

The increasing demand for bone repair solutions calls for the development of efficacious bone scaffolds. Biphasic calcium phosphate (BCP) scaffolds with both macropores and micropores (MP) have improved healing compared to those with macropores and no micropores (NMP), but the role of micropores is unclear. Here, we evaluate capillarity induced by micropores as a mechanism that can affect bone growth in vivo. Three groups of cylindrical scaffolds were implanted in pig mandibles for three weeks: MP were implanted either dry (MP-Dry), or after submersion in phosphate buffered saline, which fills pores with fluid and therefore suppresses micropore-induced capillarity (MP-Wet); NMP were implanted dry. The amount and distribution of bone in the scaffolds were quantified using micro-computed tomography. MP-Dry had a more homogeneous bone distribution than MP-Wet, although the average bone volume fraction, BVF‾, was not significantly different for these two groups (0.45±0.03 and 0.37±0.03, respectively). There was no significant difference in the radial bone distribution of NMP and MP-Wet, but the BVF‾, of NMP was significantly lower among the three groups (0.25±0.02). These results suggest that micropore-induced capillarity enhances bone regeneration by improving the homogeneity of bone distribution in BCP scaffolds. The explicit design and use of capillarity in bone scaffolds may lead to more effective treatments of large and complex bone defects. The increasing demand for bone repair calls for more efficacious bone scaffolds and calcium phosphate-based materials are considered suitable for this application. Macropores (>100μm) are necessary for bone ingrowth and vascularization. However, studies have shown that microporosity (<20μm) also enhances growth, but there is no consensus on the controlling mechanisms. In previous in vitro work, we suggested that micropore-induced capillarity had the potential to enhance bone growth in vivo. This work illustrates the

Direct deposited porous scaffolds of calcium phosphate cement with alginate for drug delivery and bone tissue engineering.

PubMed

Lee, Gil-Su; Park, Jeong-Hui; Shin, Ueon Sang; Kim, Hae-Won

2011-08-01

This study reports the preparation of novel porous scaffolds of calcium phosphate cement (CPC) combined with alginate, and their potential usefulness as a three-dimensional (3-D) matrix for drug delivery and tissue engineering of bone. An α-tricalcium phosphate-based powder was mixed with sodium alginate solution and then directly injected into a fibrous structure in a Ca-containing bath. A rapid hardening reaction of the alginate with Ca(2+) helps to shape the composite into a fibrous form with diameters of hundreds of micrometers, and subsequent pressing in a mold allows the formation of 3-D porous scaffolds with different porosity levels. After transformation of the CPC into a calcium-deficient hydroxyapatite phase in simulated biological fluid the scaffold was shown to retain its mechanical stability. During the process biological proteins, such as bovine serum albumin and lysozyme, used as model proteins, were observed to be effectively loaded onto and released from the scaffolds for up to more than a month, proving the efficacy of the scaffolds as a drug delivering matrix. Mesenchymal stem cells (MSCs) were isolated from rat bone marrow and then cultured on the CPC-alginate porous scaffolds to investigate the ability to support proliferation of cells and their subsequent differentiation along the osteogenic lineage. It was shown that MSCs increasingly actively populated and also permeated into the porous network with time of culture. In particular, cells cultured within a scaffold with a relatively high porosity level showed favorable proliferation and osteogenic differentiation. An in vivo pilot study of the CPC-alginate porous scaffolds after implantation into the rat calvarium for 6 weeks revealed the formation of new bone tissue within the scaffold, closing the defect almost completely. Based on these results, the newly developed CPC-alginate porous scaffolds could be potentially useful as a 3-D matrix for drug delivery and tissue engineering of bone

Clinical, radiological and histological evaluation of biphasic calcium phosphate bioceramic wedges filling medial high tibial valgisation osteotomies.

PubMed

Rouvillain, J L; Lavallé, F; Pascal-Mousselard, H; Catonné, Y; Daculsi, G

2009-10-01

We report clinical, radiological and histological findings following high tibial valgisation osteotomy (HTVO) using micro-macroporous biphasic calcium phosphate wedges fixed with a plate and locking screws. From 1999 to 2002, 43 knees were operated on and studied prospectively. All underwent clinical and radiological follow-up at days 1, 90, and 365 to evaluate consolidation and bone substitute interfaces. Additionally, biopsies were taken for histology at least 1 year after implantation from 10 patients who requested plate removal. Radiologically, consolidation was observed in 98% of cases. At 1 year, correction was unchanged in 95% of cases. Histological analysis revealed considerable MBCP resorption and bone ingrowth, both into the pores and replacing the bioceramic material. Polarised light microscopy confirmed normal bony architecture with trabecular and/or dense lamellar bone growth at the expense of the wedge implants. X-ray and micro-CT scan revealed a well organised and mineralised structure in the newly-formed bone. This study shows that using MBCP wedges in combination with orientable locking screws and a plate is a simple, safe and fast surgical technique for HTVO. The is the first study to examine the results by histological analysis, which confirmed good outcomes.

The Effect of Reduced Graphene Oxide-Coated Biphasic Calcium Phosphate Bone Graft Material on Osteogenesis.

PubMed

Kim, Jeong-Woo; Shin, Yong Cheol; Lee, Jin-Ju; Bae, Eun-Bin; Jeon, Young-Chan; Jeong, Chang-Mo; Yun, Mi-Jung; Lee, So-Hyoun; Han, Dong-Wook; Huh, Jung-Bo

2017-08-08

This study was conducted to evaluate the effect of biphasic calcium phosphate (BCP) coated with reduced graphene oxide (rGO) as bone graft materials on bone regeneration. The rGO-coated BCP bone graft material was fabricatied by mixing rGO and BCP at various concentrations. The surface charge of rGO-coated BCP was measured to be -14.43 mV, which formed a static electrostatic interaction. Cell viabilities were significantly diminished at higher concentrations of ≥100 μg/mL. The calvarial defects of 48 rats were implanted rGO-coated BCPs at a weight ratio of 2:1000 (rGO2), 4:1000 (rGO4), and 10:1000 (rGO10), repectively. BCP was used as a control group. The micro-CT and histological analysis were performed to evaluate new bone formation at 2 and 8 weeks after surgery. The results showed that the new bone volume (mm³) was significantly higher in the experimental groups than in the control group. Histological analysis showed that new bone areas (%) were significantly higher in the rGO2 and rGO10 than in the control, and significantly higher in rGO4 than in the rGO2 and rGO10. Conclusively, the rGO-coated BCP was found to be effective on osteogenesis and the concentration of the composite was an important factor.

Charge-balanced biphasic electrical stimulation inhibits neurite extension of spiral ganglion neurons.

PubMed

Shen, Na; Liang, Qiong; Liu, Yuehong; Lai, Bin; Li, Wen; Wang, Zhengmin; Li, Shufeng

2016-06-15

Intracochlear application of exogenous or transgenic neurotrophins, such as neurotrophin-3 (NT-3) and brain derived neurotrophic factor (BDNF), could promote the resprouting of spiral ganglion neuron (SGN) neurites in deafened animals. These resprouting neurites might reduce the gap between cochlear implant electrodes and their targeting SGNs, allowing for an improvement of spatial resolution of electrical stimulation. This study is to investigate the impact of electrical stimulation employed in CI on the extension of resprouting SGN neurites. We established an in vitro model including the devices delivering charge-balanced biphasic electrical stimulation, and spiral ganglion (SG) dissociated culture treated with BDNF and NT-3. After electrical stimulation with varying durations and intensities, we quantified neurite lengths and Schwann cell densities in SG cultures. Stimulations that were greater than 50μA or longer than 8h significantly decreased SG neurite length. Schwann cell density under 100μA electrical stimulation for 48h was significantly lower compared to that in non-stimulated group. These electrical stimulation-induced decreases of neurite extension and Schwann cell density were attenuated by various types of voltage-dependent calcium channel (VDCC) blockers, or completely prevented by their combination, cadmium or calcium-free medium. Our study suggested that charge-balanced biphasic electrical stimulation inhibited the extension of resprouting SGN neurites and decreased Schwann cell density in vitro. Calcium influx through multiple types of VDCCs was involved in the electrical stimulation-induced inhibition. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Calcium Carbonate Crystal Growth in Porous Media, in the presence of Water Miscible and Non-Miscible Organic Fluids

NASA Astrophysics Data System (ADS)

Jaho, Sofia; Sygouni, Varvara; Paraskeva, Christakis A.

2015-04-01

The deposition of sparingly soluble salts (scaling) within porous media is a major problem encountered in many industrial and environmental applications. In the oil industry scaling causes severe operational malfunctions and, therefore, increasing the total operating and maintenance cost [1]. The most common types of sparingly soluble salts located in oil fields include carbonate and sulfate salts of calcium, strondium and barium[1,2]. Multiple phase flow and tubing surface properties are some of the factors affecting scale formation [3]. The main purpose of the present work was the investigation of the precipitation mechanisms of calcium carbonate (CaCO3) through in situ mixing of two soluble salt solutions in a flow granular medium, in the presence of water miscible organic fluid (ethylene glycol) or non-miscible organic fluid (n-dodecane). All series of experiments were carried out in a two dimensional porous medium made of Plexiglas. For all solutions used in the experiments, the contact angles with the surface of the porous medium and the interfacial tensions were measured. During the experiments, the calcium carbonate crystal growth was continuously monitored and recorded through an optical microscope equipped with a digital programmed video camera. The snap-shots were taken within specific time intervals and their detailed procession gave information concerning the crystal growth rate and kinetics. The pH of the effluent was measured and fluids samples were collected for calcium analysis using Atomic Absorption Spectroscopy (AAS). In all experiments effluent calcium concentration decreased as a function of time, suggesting that CaCO3 precipitation took place inside the porous medium. Crystals of the precipitated salt were identified using Infrared Spectroscopy (IR) and the morphology of the crystals was examined using Scanning Electron Microscopy (SEM). The induction time for precipitation of CaCO3 crystals in the presence of n-dodecane was significantly

[A study of bone-like apatite formation on calcium phosphate ceramics in different kinds of animals in vivo].

PubMed

Duan, Yourong; Wu, Yao; Wang, Chaoyuan; Chen, Jiyong; Zhang, Xingdong

2003-03-01

Bone-like apatite formation on the surface of calcium phosphate ceramics has been believed to be necessary for new bone to grow on the ceramics and to be related to the osteoinductivity of the material. The research of bone-like apatite formation is a great help to understanding the mechanism of osteoinduction. Synthetic porous calcium phosphate ceramics (HA/TCP = 70/30) were implanted intramuscularly in pigs, dogs, rabbits and rats to make a comparative study of the bone-like apatite formation onto the porous HA/TCP ceramics in different animals. Specimens were harvested at 14 days after implantation. Samples were detected for the surface morphology with SEM. The chemical composition of the sample surface after implantation was analyzed with reflection infrared (R-IR). Obvious bone-like apatite formation could be detected in the sections of porous specimens harvested from all animals after 14 days intramuscular implantation. Crystal deposition could be only observed on the surface of the concave regions of the samples collected from dogs, rabbits and rat. On the contrary, evenly distributed flake-shaped crystal could be found on the pore surface and also on the outer surface of the materials implanted in pigs. The morphology of bone-like apatite in pigs was different from that in the others animals. Bone-like apatite was not observed in dense specimen implanted intramuscularly. Bone-like apatite formed faster on specimens implanted in rabbit than that in other animals. This formation sequence is different from the sequence of osteoinductivity of biphasic calcium phosphate ceramics implanted in these animals. The results demonstrated that the formation of bone-like apatite on materials is a prerequisite condition to their osteoinduction but other factors also play important roles in osteoinduction.

Torque test measurement in segmental bone defects using porous calcium phosphate cement implants.

PubMed

Kroese-Deutman, Henriette C; Wolke, Joop G C; Spauwen, Paul H M; Jansen, John A

2010-10-01

This study was performed to assess the bone healing supporting characteristics of porous calcium phosphate (Ca-P) cement when implanted in a rabbit segmental defect model as well as to determine the reliability of torque testing as a method to verify bone healing. The middiaphyseal radius was chosen as the area to create bilaterally increasing defect sizes (5, 10, and 15 mm), which were either filled with porous Ca-P cement or left open as a control. After 12 weeks of implantation, torque test measurements as well as histological and radiographic evaluation were performed. In two of the open 15 mm control defects, bone bridging was visible at the radiographic and histological evaluation. Bone was observed to be present in all porous Ca-P cement implants (5, 10, and 15 mm defects) after 12 weeks. No significant differences in torque measurements were observed between the 5 and 10 mm filled and open control defects using a t-test. In addition, the mechanical strength of all operated specimens was similar compared with nonoperated bone samples. The torsion data for the 15 mm open defect appeared to be lower compared with the filled 15 mm defect, but no significant difference could be proven. Within the limitation of the study design, porous Ca-P cement implants demonstrated osteoconductive properties and confirmed to be a suitable scaffold material in a weight-bearing situation. Further, the used torque testing method was found to be unreliable for testing the mechanical properties of the healed bone defect.

Fabrication of nano structural biphasic materials from phosphogypsum waste and their in vitro applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mohamed, Khaled R., E-mail: Kh_rezk966@yahoo.com; Mousa, Sahar M.; Inorganic Chemistry Department, National Research Centre, Dokki, P.O. Box 12622, 11787 Cairo

2014-02-01

Graphical abstract: (a) Schema of the process, (b) TEM of nano particles of biphasic materials and (c) SEM of post-immersion. - Highlights: • Ratio of HA and β-TCP phases were controlled by thermal treatment. • HA partially decomposed into β-TCP with other bioactive phases. • Calcined HA at 900 °C is the best for the bioactivity behavior. - Abstract: In this study, a novel process of preparing biphasic calcium phosphate (BCP) is proposed. Also its bioactivity for the utilization of the prepared BCP as a biomaterial is studied. A mixture of calcium hydroxyapatite (HAP) and tricalcium phosphate (β-TCP) could bemore » obtained by thermal treatment of HAP which was previously prepared from phosphogypsum (PG) waste. The chemical and phase composition, morphology and particle size of prepared samples was characterized by X-ray diffraction (XRD), Infrared spectroscopy (IR), Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM). The bioactivity was investigated by soaking of the calcined samples in simulated body fluid (SBF). Results confirmed that the calcination temperatures played an important role in the formation of calcium phosphate (CP) materials. XRD results indicated that HAP was partially decomposed into β-TCP. The in vitro data confirmed that the calcined HAP forming BCP besides other phases such as pyrophosphate and silica are bioactive materials. Therefore, BCP will be used as good biomaterials for medical applications.« less

Electroactive Film of Myoglobin Incorporated in a 3D-porous Calcium Alginate Film with Polyvinyl Alcohol, Glycerin and Gelatin.

PubMed

Zheng, Xueqin; Sun, Hong; Hou, Shifeng

2015-01-01

In this work, an electroactive porous Mb-CA's composite film was fabricated by incorporating myoglobin (Mb) in a three-dimension (3D) porous calcium alginate (CA) film with polyvinyl alcohol, glycerol, and gelatin. The porous Mb-CA's film modified electrodes exhibited a pair of well-defined, quasi-reversible cyclic voltammetric (CV) peaks at about -0.37 V vs. SCE in pH 7.0 buffers, characteristic of Mb heme Fe((III))/Fe((II)) redox couples. The electrochemical parameters, such as formal potentials (E(o')) and apparent heterogeneous electron-transfer rate constants (ks), were estimated by square-wave voltammetry with nonlinear regression analysis. The porous CA's composite film could form hydrogel in aqueous solution. The positions of the Soret absorbance band suggest that Mb in the CA's composite film kept its native states in the medium pH range. Hydrogen peroxide, oxygen, and nitrite were electrochemically catalyzed by the Mb-CA's composite film with significant lowering of the reduction overpotential.

The Effect of Reduced Graphene Oxide-Coated Biphasic Calcium Phosphate Bone Graft Material on Osteogenesis

PubMed Central

Kim, Jeong-Woo; Lee, Jin-Ju; Bae, Eun-Bin; Jeon, Young-Chan; Jeong, Chang-Mo; Yun, Mi-Jung; Lee, So-Hyoun; Huh, Jung-Bo

2017-01-01

This study was conducted to evaluate the effect of biphasic calcium phosphate (BCP) coated with reduced graphene oxide (rGO) as bone graft materials on bone regeneration. The rGO-coated BCP bone graft material was fabricatied by mixing rGO and BCP at various concentrations. The surface charge of rGO-coated BCP was measured to be −14.43 mV, which formed a static electrostatic interaction. Cell viabilities were significantly diminished at higher concentrations of ≥100 μg/mL. The calvarial defects of 48 rats were implanted rGO-coated BCPs at a weight ratio of 2:1000 (rGO2), 4:1000 (rGO4), and 10:1000 (rGO10), repectively. BCP was used as a control group. The micro-CT and histological analysis were performed to evaluate new bone formation at 2 and 8 weeks after surgery. The results showed that the new bone volume (mm3) was significantly higher in the experimental groups than in the control group. Histological analysis showed that new bone areas (%) were significantly higher in the rGO2 and rGO10 than in the control, and significantly higher in rGO4 than in the rGO2 and rGO10. Conclusively, the rGO-coated BCP was found to be effective on osteogenesis and the concentration of the composite was an important factor. PMID:28786931

Intrinsic Size Effect in Scaffolded Porous Calcium Silicate Particles and Mechanical Behavior of Their Self-Assembled Ensembles.

PubMed

Hwang, Sung Hoon; Shahsavari, Rouzbeh

2018-01-10

Scaffolded porous submicron particles with well-defined diameter, shape, and pore size have profound impacts on drug delivery, bone-tissue replacement, catalysis, sensors, photonic crystals, and self-healing materials. However, understanding the interplay between pore size, particle size, and mechanical properties of such ultrafine particles, especially at the level of individual particles and their ensemble states, is a challenge. Herein, we focus on porous calcium-silicate submicron particles with various diameters-as a model system-and perform extensive 900+ nanoindentations to completely map out their mechanical properties at three distinct structural forms from individual submicron particles to self-assembled ensembles to pressure-induced assembled arrays. Our results demonstrate a notable "intrinsic size effect" for individual porous submicron particles around ∼200-500 nm, induced by the ratio of particle characteristic diameter to pore characteristic size distribution. Increasing this ratio results in a brittle-to-ductile transition where the toughness of the submicron particles increases by 120%. This size effect becomes negligible as the porous particles form superstructures. Nevertheless, the self-assembled arrays collectively exhibit increasing elastic modulus as a function of applied forces, while pressure-induced compacted arrays exhibit no size effect. This study will impact tuning properties of individual scaffolded porous particles and can have implications on self-assembled superstructures exploiting porosity and particle size to impart new functionalities.

Sodium lauryl sulfate impedes drug release from zinc-crosslinked alginate beads: switching from enteric coating release into biphasic profiles.

PubMed

Taha, Mutasem O; Nasser, Wissam; Ardakani, Adel; Alkhatib, Hatim S

2008-02-28

The aim of this research is to investigate the effects of sodium lauryl sulfate (SLS) on ionotropically cross-linked alginate beads. Different levels of SLS were mixed with sodium alginate and chlorpheniramine maleate (as loaded model drug). The resulting viscous solutions were dropped onto aqueous solutions of zinc or calcium ions for ionotropic curing. The generated beads were assessed by their drug releasing profiles, infrared and differential scanning colorimetery (DSC) traits. SLS was found to exert profound concentration-dependent impacts on the characteristics of zinc-crosslinked alginate beads such that moderate modifications in the levels of SLS switched drug release from enteric coating-like behavior to a biphasic release modifiable to sustained-release by the addition of minute amounts of xanthan gum. Calcium cross-linking failed to reproduce the same behavior, probably due to the mainly ionic nature of calcium-carboxylate bonds compared to the coordinate character of their zinc-carboxylate counterparts. Apparently, moderate levels of SLS repel water penetration into the beads, and therefore minimize chlorpheniramine release. However, higher SLS levels seem to discourage polymeric cross-linking and therefore allow biphasic drug release.

Lipase in biphasic alginate beads as a biocatalyst for esterification of butyric acid and butanol in aqueous media.

PubMed

Ng, Choong Hey; Yang, Kun-Lin

2016-01-01

Esterification of organic acids and alcohols in aqueous media is very inefficient due to thermodynamic constraints. However, fermentation processes used to produce organic acids and alcohols are often conducted in aqueous media. To produce esters in aqueous media, biphasic alginate beads with immobilized lipase are developed for in situ esterification of butanol and butyric acid. The biphasic beads contain a solid matrix of calcium alginate and hexadecane together with 5 mg/mL of lipase as the biocatalyst. Hexadecane in the biphasic beads serves as an organic phase to facilitate the esterification reaction. Under optimized conditions, the beads are able to catalyze the production of 0.16 mmol of butyl butyrate from 0.5 mmol of butyric acid and 1.5 mmol of butanol. In contrast, when monophasic beads (without hexadecane) are used, only trace amount of butyl butyrate is produced. One main application of biphasic beads is in simultaneous fermentation and esterification (SFE) because the organic phase inside the beads is very stable and does not leach out into the culture medium. SFE is successfully conducted with an esterification yield of 6.32% using biphasic beads containing iso-octane even though the solvent is proven toxic to the butanol-producing Clostridium spp. Copyright © 2015 Elsevier Inc. All rights reserved.

Influence of a cellulosic ether carrier on the structure of biphasic calcium phosphate ceramic particles in an injectable composite material.

PubMed

Dupraz, A; Nguyen, T P; Richard, M; Daculsi, G; Passuti, N

1999-04-01

An injectable composite material based on biphasic calcium phosphate (BCP) and a nonionic cellulose ether has been elaborated for use in percutaneous surgery for spine fusion. This paper reports the characterization results of this material by spectroscopic techniques including X-ray diffraction (XRD), infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) fitted with an energy dispersive X-Ray analysis system and high-resolution transmission electron microscopy (HR-TEM). From FTIR and XPS results, it was observed that the adhesion between the polymer and the ceramic might be insured by oxygen bridging developed through an ionic bonding between calcium ions and (C-O) groups of the polymer. Moreover, XPS showed attraction of Ca2+ ions in the polymer matrix, while the ceramic surface was modified in a HPO4(2-) -rich layer. These results suggest a possible dissolution/precipitation process at the interface ceramic/polymer. HR-TEM observations supported this hypothesis, showing a light contrasted fringe at the surface of the ceramic grains in the composite paste. As well, changes in the XRD spectra could indicate a small decrease in the crystal size of the BCP powder through the contact to polymer solution. In addition, SEM observation showed a decrease of the initial BCP granulometry. Aggregates of 80-200 microm seemed to be mostly dissociated in micrograins. The ceramic grains were coated with and bonded between each other by the polymer matrix, which acted as spacer in between the ceramic grains, creating a macroporous-like material structure.

[Experiment of porous calcium phosphate/bone matrix gelatin composite cement for repairing lumbar vertebral bone defect in rabbit].

PubMed

Wang, Song; Yang, Han; Yang, Jian; Kang, Jianping; Wang, Qing; Song, Yueming

2017-12-01

To investigate the effect of a porous calcium phosphate/bone matrix gelatin (BMG) composite cement (hereinafter referred to as the "porous composite cement") for repairing lumbar vertebral bone defect in a rabbit model. BMG was extracted from adult New Zealand rabbits according to the Urist's method. Poly (lactic-co-glycolic) acid (PLGA) microsphere was prepared by W/O/W double emulsion method. The porous composite cement was developed by using calcium phosphate cement (CPC) composited with BMG and PLGA microsphere. The physicochemical characterizations of the porous composite cement were assessed by anti-washout property, porosity, and biomechanical experiment, also compared with the CPC. Thirty 2-month-old New Zealand rabbits were used to construct vertebral bone defect at L 3 in size of 4 mm×3 mm×3 mm. Then, the bone defect was repaired with porous composite cement (experimental group, n =15) or CPC (control group, n =15). At 4, 8, and 12 weeks after implantation, each bone specimen was assessed by X-ray films for bone fusion, micro-CT for bone mineral density (BMD), bone volume fraction (BVF), trabecular thickness (Tb. Th.), trabecular number (Tb.N.), and trabecular spacing (Tb. Sp.), and histological section with toluidine blue staining for new-born bone formation. The study demonstrated well anti-washout property in 2 groups. The porous composite cement has 55.06%±1.18% of porosity and (51.63±6.73) MPa of compressive strength. The CPC has 49.38%±1.75% of porosity and (63.34±3.27) MPa of compressive strength. There were significant differences in porosity and compressive strength between different cements ( t =4.254, P =0.006; t =2.476, P =0.034). X-ray films revealed that the zone between the cement and host bone gradually blurred with the time extending. At 12 weeks after implantation, the zone was disappeared in the experimental group, but clear in the control group. There were significant differences in BMD, BVF, Tb. Th., Tb. N., and Tb. Sp. between

Biphasic decay of the Ca transient results from increased sarcoplasmic reticulum Ca leak

PubMed Central

Sankaranarayanan, Rajiv; Li, Yatong; Greensmith, David J.; Eisner, David A.

2016-01-01

Key points Ca leak from the sarcoplasmic reticulum through the ryanodine receptor (RyR) reduces the amplitude of the Ca transient and slows its rate of decay.In the presence of β‐adrenergic stimulation, RyR‐mediated Ca leak produces a biphasic decay of the Ca transient with a fast early phase and a slow late phase.Two forms of Ca leak have been studied, Ca‐sensitising (induced by caffeine) and non‐sensitising (induced by ryanodine) and both induce biphasic decay of the Ca transient.Only Ca‐sensitising leak can be reversed by traditional RyR inhibitors such as tetracaine.Ca leak can also induce Ca waves. At low levels of leak, waves occur. As leak is increased, first biphasic decay and then slowed monophasic decay is seen. The level of leak has major effects on the shape of the Ca transient. Abstract In heart failure, a reduction in Ca transient amplitude and contractile dysfunction can by caused by Ca leak through the sarcoplasmic reticulum (SR) Ca channel (ryanodine receptor, RyR) and/or decreased activity of the SR Ca ATPase (SERCA). We have characterised the effects of two forms of Ca leak (Ca‐sensitising and non‐sensitising) on calcium cycling and compared with those of SERCA inhibition. We measured [Ca2+]i with fluo‐3 in voltage‐clamped rat ventricular myocytes. Increasing SR leak with either caffeine (to sensitise the RyR to Ca activation) or ryanodine (non‐sensitising) had similar effects to SERCA inhibition: decreased systolic [Ca2+]i, increased diastolic [Ca2+]i and slowed decay. However, in the presence of isoproterenol, leak produced a biphasic decay of the Ca transient in the majority of cells while SERCA inhibition produced monophasic decay. Tetracaine reversed the effects of caffeine but not of ryanodine. When caffeine (1 mmol l−1) was added to a cell which displayed Ca waves, the wave frequency initially increased before waves disappeared and biphasic decay developed. Eventually (at higher caffeine concentrations), the

Consolidation of degraded ornamental porous limestone stone by calcium carbonate precipitation induced by the microbiota inhabiting the stone.

PubMed

Jimenez-Lopez, C; Rodriguez-Navarro, C; Piñar, G; Carrillo-Rosúa, F J; Rodriguez-Gallego, M; Gonzalez-Muñoz, M T

2007-08-01

Although it has already been shown that calcareous stone can be consolidated by using a bacterially inoculated culture medium, a more user-friendly method is the in situ application of a sterile culture medium that is able to activate, among the microbial community of the stone, those bacteria with a potential for calcium carbonate precipitation. In order to test this new method for stone consolidation, non-sterilized decayed porous limestone was immersed in sterile nutritional media. Results were compared to those of the runs in which stone sterilized prior to the treatment was used. The effects of the microbial community on stone consolidation were determined by recording the evolution of the culture media chemistry. The treated stone was tested for mechanical resistance and porosity. Results demonstrate that the tested media were able to activate bacteria from the microbial community of the stone. As a consequence of the growth of these bacteria, an alkalinization occurred that resulted in calcium carbonate precipitation. The new precipitate was compatible with the substrate and consolidated the stone without pore plugging. Therefore, a good candidate to in situ consolidate decayed porous limestone is the application of a sterile culture medium with the characteristics specified in the present study.

The effect of sol-gel-formed calcium phosphate coatings on bone ingrowth and osteoconductivity of porous-surfaced Ti alloy implants.

PubMed

Nguyen, H Q; Deporter, D A; Pilliar, R M; Valiquette, N; Yakubovich, R

2004-02-01

Ti-6Al-4V implants formed with a sintered porous surface for implant fixation by bone ingrowth were prepared with or without the addition of a thin surface layer of calcium phosphate (Ca-P) formed using a sol-gel coating technique over the porous surface. The implants were placed transversely across the tibiae of 17 rabbits. Implanted sites were allowed to heal for 2 weeks, after which specimens were retrieved for morphometric assessment using backscattered scanning electron microscopy and quantitative image analysis. Bone formation along the porous-structured implant surface, was measured in relation to the medial and lateral cortices as an indication of implant surface osteoconductivity. The Absolute Contact Length measurements of endosteal bone growth along the porous-surfaced zone were greater with the Ca-P-coated implants compared to the non-Ca-P-coated implants. The Ca-P-coated implants also displayed a trend towards a significant increase in the area of bone ingrowth (Bone Ingrowth Fraction). Finally, there was significantly greater bone-to-implant contact within the sinter neck regions of the Ca-P-coated implants.

A microstructural study of the degradation and calcium release from hydroxyapatite-calcium oxide ceramics made by infiltration.

PubMed

Zhang, Qinghao; Schmelzer, Eva; Gerlach, Jörg C; Nettleship, Ian

2017-04-01

Hydroxyapatite pellets, partially densified in a low-temperature heat treatment, were infiltrated with calcium nitrate solution followed by in-situ precipitation of Ca(OH) 2 and CaCO 3 . The infiltrated bodies were then densified to high relative density and the calcium carbonate transformed to calcium oxide during sintering and resulted in biphasic hydroxyapatite-CaO ceramics. This work investigated the influence of the infiltration on surface morphology, weight change, and microstructural-level degradation caused by exposure to saline at pH=7.4 and a temperature of 20°C. The CaO rendered the materials more susceptible to degradation, and released calcium into the saline faster than single phase, calcium deficient hydroxyapatite (HA) that were used as a control. In consequence, these ceramics could be used to release calcium into the culture microenvironments of bone tissue or bone marrow cells next to a scaffold surface. Copyright © 2016 Elsevier B.V. All rights reserved.

Superiority of Biphasic Over Monophasic Defibrillation Shocks is Attributable to Less Intracellular Calcium Transient Heterogeneity

PubMed Central

Hwang, Gyo-Seung; Tang, Liang; Joung, Boyoung; Morita, Norishige; Hayashi, Hideki; Karagueuzian, Hrayr S.; Weiss, James N.; Lin, Shien-Fong; Chen, Peng-Sheng

2008-01-01

Objectives To test the hypothesis that superiority of biphasic waveform (BW) over monophasic waveform (MW) defibrillation shocks is attributable to less intracellular calcium (Cai) transient heterogeneity. Background The mechanism by which BW shocks have a higher defibrillation efficacy than MW shocks remains unclear. Methods We simultaneously mapped epicardial membrane potential (Vm) and Cai during 6 ms MW and 3/3 ms BW shocks in 19 Langendorff-perfused rabbit ventricles. After shock, the percentage of depolarized area was plotted over time. The maximum (peak) postshock values (VmP and CaiP, respectively) were used to measure heterogeneity. Higher VmP and CaiP imply less heterogeneity. Results The defibrillation threshold was for BW and MW shocks were 288±99 V and 399±155 V, respectively (p=0.0005). Successful BW shocks had higher VmP (88±9 %) and CaiP (70±13 %) than unsuccessful MW shocks (VmP 76 %±10, p<0.001; CaiP, 57±8 %, p<0.001) of the same shock strength. In contrast, for unsuccessful BW and MW shocks of the same shock strengths, the VmP and CaiP were not significantly different. MW shocks more frequently created regions of low Cai surrounded by regions of high Cai (postshock Cai sinkholes). The defibrillation threshold for MW and BW shocks became similar after disabling the sarcoplasmic reticulum with thapsigargin and ryanodine. Conclusions The greater efficacy of BW shocks is directly related to their less heterogeneous effects on shock-induced sarcoplasmic reticulum Ca release and Cai transients. Less heterogeneous Cai transients reduces the probability of Cai sinkhole formation, thereby preventing the postshock reinitiation of VF. PMID:18755345

Impact of non-thermal plasma surface modification on porous calcium hydroxyapatite ceramics for bone regeneration

PubMed Central

Moriguchi, Yu; Lee, Dae-Sung; Thamina, Khair; Masuda, Kazuto; Itsuki, Dai; Yoshikawa, Hideki; Hamaguchi, Satoshi; Myoui, Akira

2018-01-01

In the physiochemical sciences, plasma is used to describe an ionized gas. Previous studies have implicated plasma surface treatment in the enhancement of hydrophilicity of implanted musculoskeletal reconstructive materials. Hydroxyapatite (HA) ceramics, widely used in bone tissue regeneration, have made great advancements to skeletal surgery. In the present study, we investigate the impact of low-pressure plasma on the interconnected porous calcium hydroxyapatite (IP-CHA) both in vitro and in vivo. Our results indicate that dielectric barrier discharge (DBD) plasma, when used with oxygen, can augment the hydrophilicity of non-porous HA surfaces and the osteoconductivity of the IP-CHA disc via increased water penetration of inner porous structures, as demonstrated through microfocus computed tomography (μCT) assay. In vivo implantation of plasma-treated IP-CHA displayed superior bone ingrowth than untreated IP-CHA. Though plasma-treated IP-CHA did not alter osteoblast cell proliferation, it accelerated osteogenic differentiation of seeded marrow mesenchymal stem cells. In vitro X-ray photoelectron spectroscopy (XPS) revealed that this plasma treatment increases levels of oxygen, rather than nitrogen, on the plasma-treated IP-CHA surface. These findings suggest that plasma treatment, an easy and simple processing, can significantly improve the osteoconductive potential of commonly used artificial bones such as IP-CHA. Further optimization of plasma treatment and longer-term follow-up of in vivo application are required toward its clinical application. PMID:29538457

Applications of ionic liquids in biphasic separation: Aqueous biphasic systems and liquid-liquid equilibria.

PubMed

Shukla, Shashi Kant; Pandey, Shubha; Pandey, Siddharth

2018-07-20

Ionic liquids (ILs) have been receiving much attention in many fields of analytical chemistry because of their various interesting properties which distinguish them from volatile organic compounds. They offer both directional and non-directional forces towards a solute molecule and therefore act as excellent solvents for a wide range of polar and non-polar compounds. Because of the presence of various possible interactions, ILs easily undergo biphasic separation with water and other less polar/non-polar organic solvents. Their ability to create biphasic splitting makes them a promising candidate for liquid-liquid separation processes, such as aqueous biphasic systems and liquid-liquid equilibria. Various aspects of ILs in these separation methods are discussed in view of the origin of physical forces responsible for the biphasic interactions, the effect of structural components, temperature, pressure, pH and additives. The specific advantages of using ILs in aqueous biphasic systems and liquid-liquid equilibria in binary and ternary systems are discussed with a view to defining their future role in separation processes by giving major emphasis on developing non-toxic ILs with physical and solution properties tailored to the needs of specific sample preparation techniques. Copyright © 2017 Elsevier B.V. All rights reserved.

Preliminary study on removing Cs⁺/Sr²⁺ by activated porous calcium silicate-A by-product from high-alumina fly ash recycling industry.

PubMed

Chu, Yingying; Wang, Rong; Chen, Mengjun

2015-01-01

¹³⁷Cs⁺/⁹⁰Sr²⁺-containing radioactive wastewater is one of the most important problems that the world has been facing with. A by-product, activated porous calcium silicate, is generated at high levels by the pre-desiliconizing and soda-lime-sintering processes for producing Al₂O₃from high-alumina fly ash. In order to examine if this by-product could be used as an absorbent for removal of ¹³⁷Cs⁺/⁹⁰Sr²⁺ from radioactive wastewater, various parameters, such as pH, adsorbent dose, contact time, and initial concentration, were discussed. Results indicated that the equilibrium reached in about 2 hr. Activated porous calcium silicate was highly pH sensitive and able to remove Cs(+)/Sr²⁺ in a near-neutral environment. The adsorption equilibrium was best described by Freundlich isotherm equations, and the adsorption of Cs⁺/Sr²⁺ was a physical process. The adsorption kinetic data could be better fitted by the pseudo-second-order model, and the adsorption was controlled by multidiffusion. Current study showed that activated porous calcium silicate has a good adsorption of Cs⁺/Sr²⁺ for their removal. However, other characteristics, such as selectivity because of coexisting cations, elution and regeneration, thermal stability, and acid resistance, should be discussed carefully before using it in an actual field.

The calcium-frequency response in the rat ventricular myocyte: an experimental and modelling study.

PubMed

Gattoni, Sara; Røe, Åsmund Treu; Frisk, Michael; Louch, William E; Niederer, Steven A; Smith, Nicolas P

2016-08-01

In the majority of species, including humans, increased heart rate increases cardiac contractility. This change is known as the force-frequency response (FFR). The majority of mammals have a positive force-frequency relationship (FFR). In rat the FFR is controversial. We derive a species- and temperature-specific data-driven model of the rat ventricular myocyte. As a measure of the FFR, we test the effects of changes in frequency and extracellular calcium on the calcium-frequency response (CFR) in our model and three altered models. The results show a biphasic peak calcium-frequency response, due to biphasic behaviour of the ryanodine receptor and the combined effect of the rapid calmodulin buffer and the frequency-dependent increase in diastolic calcium. Alterations to the model reveal that inclusion of Ca(2+) /calmodulin-dependent protein kinase II (CAMKII)-mediated L-type channel and transient outward K(+) current activity enhances the positive magnitude calcium-frequency response, and the absence of CAMKII-mediated increase in activity of the sarco/endoplasmic reticulum Ca(2+) -ATPase induces a negative magnitude calcium-frequency response. An increase in heart rate affects the strength of cardiac contraction by altering the Ca(2+) transient as a response to physiological demands. This is described by the force-frequency response (FFR), a change in developed force with pacing frequency. The majority of mammals, including humans, have a positive FFR, and cardiac contraction strength increases with heart rate. However, the rat and mouse are exceptions, with the majority of studies reporting a negative FFR, while others report either a biphasic or a positive FFR. Understanding the differences in the FFR between humans and rats is fundamental to interpreting rat-based experimental findings in the context of human physiology. We have developed a novel model of rat ventricular electrophysiology and calcium dynamics, derived predominantly from experimental data

Superiority of biphasic over monophasic defibrillation shocks is attributable to less intracellular calcium transient heterogeneity.

PubMed

Hwang, Gyo-Seung; Tang, Liang; Joung, Boyoung; Morita, Norishige; Hayashi, Hideki; Karagueuzian, Hrayr S; Weiss, James N; Lin, Shien-Fong; Chen, Peng-Sheng

2008-09-02

The purpose of this study was to test the hypothesis that superiority of biphasic waveform (BW) over monophasic waveform (MW) defibrillation shocks is attributable to less intracellular calcium (Ca(i)) transient heterogeneity. The mechanism by which BW shocks have a higher defibrillation efficacy than MW shocks remains unclear. We simultaneously mapped epicardial membrane potential (Vm) and Ca(i) during 6-ms MW and 3-ms/3-ms BW shocks in 19 Langendorff-perfused rabbit ventricles. After shock, the percentage of depolarized area was plotted over time. The maximum (peak) post-shock values (VmP and Ca(i)P, respectively) were used to measure heterogeneity. Higher VmP and Ca(i)P imply less heterogeneity. The defibrillation thresholds for BW and MW shocks were 288 +/- 99 V and 399 +/- 155 V, respectively (p = 0.0005). Successful BW shocks had higher VmP (88 +/- 9%) and Ca(i)P (70 +/- 13%) than unsuccessful MW shocks (VmP 76 +/- 10%, p < 0.001; Ca(i)P 57 +/- 8%, p < 0.001) of the same shock strength. In contrast, for unsuccessful BW and MW shocks of the same shock strengths, the VmP and Ca(i)P were not significantly different. The MW shocks more frequently created regions of low Ca(i) surrounded by regions of high Ca(i) (post-shock Ca(i) sinkholes). The defibrillation threshold for MW and BW shocks became similar after disabling the sarcoplasmic reticulum (SR) with thapsigargin and ryanodine. The greater efficacy of BW shocks is directly related to their less heterogeneous effects on shock-induced SR Ca release and Ca(i) transients. Less heterogeneous Ca(i) transients reduces the probability of Ca(i) sinkhole formation, thereby preventing the post-shock reinitiation of ventricular fibrillation.

Coextrusion-Based 3D Plotting of Ceramic Pastes for Porous Calcium Phosphate Scaffolds Comprised of Hollow Filaments.

PubMed

Jo, In-Hwan; Koh, Young-Hag; Kim, Hyoun-Ee

2018-05-29

This paper demonstrates the utility of coextrusion-based 3D plotting of ceramic pastes (CoEx-3DP) as a new type of additive manufacturing (AM) technique, which can produce porous calcium phosphate (CaP) ceramic scaffolds comprised of hollow CaP filaments. In this technique, green filaments with a controlled core/shell structure can be produced by coextruding an initial feedrod, comprised of the carbon black (CB) core and CaP shell, through a fine nozzle in an acetone bath and then deposited in a controlled manner according to predetermined paths. In addition, channels in CaP filaments can be created through the removal of the CB cores during heat-treatment. Produced CaP scaffolds had two different types of pores with well-defined geometries: three-dimensionally interconnected pores (~360 × 230 μm² in sizes) and channels (>100 μm in diameter) in hollow CaP filaments. The porous scaffolds showed high compressive strengths of ~12.3 ± 2.2 MPa at a high porosity of ~73 vol % when compressed parallel to the direction of the hollow CaP filaments. In addition, the mechanical properties of porous CaP scaffolds could be tailored by adjusting their porosity, for example, compressive strengths of 4.8 ± 1.1 MPa at a porosity of ~82 vol %. The porous CaP scaffold showed good biocompatibility, which was assessed by in vitro cell tests, where several the cells adhered to and spread actively with the outer and inner surfaces of the hollow CaP filaments.

Osteoinduction and survival of osteoblasts and bone-marrow stromal cells in 3D biphasic calcium phosphate scaffolds under static and dynamic culture conditions.

PubMed

Rath, Subha N; Strobel, Leonie A; Arkudas, Andreas; Beier, Justus P; Maier, Anne-Kathrin; Greil, Peter; Horch, Raymund E; Kneser, Ulrich

2012-10-01

In many tissue engineering approaches, the basic difference between in vitro and in vivo conditions for cells within three-dimensional (3D) constructs is the nutrition flow dynamics. To achieve comparable results in vitro, bioreactors are advised for improved cell survival, as they are able to provide a controlled flow through the scaffold. We hypothesize that a bioreactor would enhance long-term differentiation conditions of osteogenic cells in 3D scaffolds. To achieve this either primary rat osteoblasts or bone marrow stromal cells (BMSC) were implanted on uniform-sized biphasic calcium phosphate (BCP) scaffolds produced by a 3D printing method. Three types of culture conditions were applied: static culture without osteoinduction (Group A); static culture with osteoinduction (Group B); dynamic culture with osteoinduction (Group C). After 3 and 6 weeks, the scaffolds were analysed by alkaline phosphatase (ALP), dsDNA amount, SEM, fluorescent labelled live-dead assay, and real-time RT-PCR in addition to weekly alamarBlue assays. With osteoinduction, increased ALP values and calcium deposition are observed; however, under static conditions, a significant decrease in the cell number on the biomaterial is observed. Interestingly, the bioreactor system not only reversed the decreased cell numbers but also increased their differentiation potential. We conclude from this study that a continuous flow bioreactor not only preserves the number of osteogenic cells but also keeps their differentiation ability in balance providing a suitable cell-seeded scaffold product for applications in regenerative medicine. © 2012 The Authors Journal of Cellular and Molecular Medicine © 2012 Foundation for Cellular and Molecular Medicine/Blackwell Publishing Ltd.

Hierarchically porous structure, mechanical strength and cell biological behaviors of calcium phosphate composite scaffolds prepared by combination of extrusion and porogen burnout technique and enhanced by gelatin.

PubMed

Feng, Shenglei; He, Fupo; Ye, Jiandong

2018-01-01

In this study, hierarchically porous calcium phosphate scaffolds (HTCP) with unidirectional pores, transversely interconnected pores, and micropores were fabricated by the combination of extrusion and porogen burnout technique. Gelatin was incorporated into the HTCP scaffolds by vacuum-impregnation of gelatin solution and subsequent freeze-drying. The phase composition, microstructure, physical and cytobiological properties were analyzed. The results showed that the HTCP scaffolds were composed of β-tricalcium phosphate with minor hydroxyapatite. The HTCP scaffolds had unidirectional pores (~400μm), transversely interconnected pores (~130μm) and micropores (~1μm). The incorporation of gelatin significantly increased the compressive strength, toughness, and cell seeding of the HTCP scaffolds. The composite scaffolds showed excellent cytocompatibility. The hierarchically porous calcium phosphate composite scaffolds may have potential application prospects in bone tissue engineering. Copyright © 2017 Elsevier B.V. All rights reserved.

Preparation and characterization of calcium phosphate ceramics and composites as bone substitutes

NASA Astrophysics Data System (ADS)

Zhang, Xing

Marine CaCO3 skeletons have tailored architectures created by nature, which give them structural support and other functions. For example, seashells have dense lamellar structures, while coral, cuttlebone and sea urchin spines have interconnected porous structures. In our experiments, seashells, coral and cuttlebone were hydrothermally converted to hydroxyapatite (HAP), and sea urchin spines were converted to Mg-substituted tricalcium phosphate (beta-TCMP), while maintaining their original structures. Partially converted shell samples have mechanical strength, which is close to that of compact human bone. After implantation of converted shell and spine samples in rat femoral defects for 6 weeks, there was newly formed bone growth up to and around the implants. Some new bone was found to migrate through the pores of converted spine samples and grow inward. These results show good bioactivity and osteoconductivity of the implants, indicating the converted shell and spine samples can be used as bone defect fillers. Calcium phosphate powders were prepared through different synthesis methods. Micro-size HAP rods were synthesized by hydrothermal method through a nucleation-growth mechanism. On the other hand, HAP particles, which have good crystallinity, were prepared by wet precipitation with further hydrothermal treatment. beta-TCP or beta-TCMP powders were prepared by a two-step process: wet precipitation of apatitic tricalcium phosphate ('precursor') and calcination of the precursor at 800°C for 3 hours. beta-TCMP or beta-TCP powders were also prepared by solid-state reactions from CaHPO4 and CaCO 3 with/without MgO. Biphasic calcium phosphate, which is mixture of HAP and beta-TCP, can be prepared though mechanical mixing of HAP and beta-TCP powders synthesized as above. Dense beta-TCP and beta-TCMP ceramics can be produced by pressing green bodies at 100MPa and further sintering above 1100°C for 2 hours. beta-TCMP ceramics ˜99.4% relative dense were prepared by

General quantitative analysis of stress partitioning and boundary conditions in undrained biphasic porous media via a purely macroscopic and purely variational approach

NASA Astrophysics Data System (ADS)

Serpieri, Roberto; Travascio, Francesco

2016-03-01

In poroelasticity, the effective stress law relates the external stress applied to the medium to the macroscopic strain of the solid phase and the interstitial pressure of the fluid saturating the mixture. Such relationship has been formerly introduced by Terzaghi in form of a principle. To date, no poroelastic theory is capable of recovering a stress partitioning law in agreement with Terzaghi's postulated one in the absence of ad hoc constitutive assumptions on the medium. We recently proposed a variational macroscopic continuum description of two-phase poroelasticity to derive a general biphasic formulation at finite deformations, termed variational macroscopic theory of porous media (VMTPM). Such approach proceeds from the inclusion of the intrinsic volumetric strain among the kinematic descriptors aside to macroscopic displacements, and as a variational theory, uses the Hamilton least-action principle as the unique primitive concept of mechanics invoked to derive momentum balance equations. In a previous related work it was shown that, for the subclass of undrained problems, VMTPM predicts that stress is partitioned in the two phases in strict compliance with Terzaghi's law, irrespective of the microstructural and constitutive features of a given medium. In the present contribution, we further develop the linearized framework of VMTPM to arrive at a general operative formula that allows the quantitative determination of stress partitioning in a jacketed test over a generic isotropic biphasic specimen. This formula is quantitative and general, in that it relates the partial phase stresses to the externally applied stress as function of partitioning coefficients that are all derived by strictly following a purely variational and purely macroscopic approach, and in the absence of any specific hypothesis on the microstructural or constitutive features of a given medium. To achieve this result, the stiffness coefficients of the theory are derived by using

Tailoring the structure of biphasic calcium phosphate via synthesis procedure

NASA Astrophysics Data System (ADS)

Mansour, S. F.; El-dek, S. I.; Ahmed, M. K.

2017-12-01

Nano calcium phosphate ceramics (CaPC) were synthesized using simple co-precipitation method at different preparation conditions. The selected Ca/P ratio with a variation of pH value lead to formation of dicalcium phosphate dihydrate (DCPD) at pH 5 and 6 while, hydroxyapatite (HAP) nano particles were formed at pH 9 and 12 at room temperature. The crystallite size was in the range of 15-55 nm depending on the obtained crystalline phase. The study displayed variation of decomposition depending on the annealing temperature. The significant note is the different transformation trend of each phase depending on the starting pH value. The HRTEM illustrated that the DCPD phase was formed as fibers with diameter around 4-6 nm, while HAP was formed in rod shape. The aspect ratio decreased from 6.6 at pH 9 to 4 at pH 12 which refer to the great influence of pH value on the morphology of calcium phosphates.

Porous calcium polyphosphate bone substitutes: additive manufacturing versus conventional gravity sinter processing-effect on structure and mechanical properties.

PubMed

Hu, Youxin; Shanjani, Yaser; Toyserkani, Ehsan; Grynpas, Marc; Wang, Rizhi; Pilliar, Robert

2014-02-01

Porous calcium polyphosphate (CPP) structures proposed as bone-substitute implants and made by sintering CPP powders to form bending test samples of approximately 35 vol % porosity were machined from preformed blocks made either by additive manufacturing (AM) or conventional gravity sintering (CS) methods and the structure and mechanical characteristics of samples so made were compared. AM-made samples displayed higher bending strengths (≈1.2-1.4 times greater than CS-made samples), whereas elastic constant (i.e., effective elastic modulus of the porous structures) that is determined by material elastic modulus and structural geometry of the samples was ≈1.9-2.3 times greater for AM-made samples. X-ray diffraction analysis showed that samples made by either method displayed the same crystal structure forming β-CPP after sinter annealing. The material elastic modulus, E, determined using nanoindentation tests also showed the same value for both sample types (i.e., E ≈ 64 GPa). Examination of the porous structures indicated that significantly larger sinter necks resulted in the AM-made samples which presumably resulted in the higher mechanical properties. The development of mechanical properties was attributed to the different sinter anneal procedures required to make 35 vol % porous samples by the two methods. A primary objective of the present study, in addition to reporting on bending strength and sample stiffness (elastic constant) characteristics, was to determine why the two processes resulted in the observed mechanical property differences for samples of equivalent volume percentage of porosity. An understanding of the fundamental reason(s) for the observed effect is considered important for developing improved processes for preparation of porous CPP implants as bone substitutes for use in high load-bearing skeletal sites. Copyright © 2013 Wiley Periodicals, Inc.

[Effects of simulated body fluid flowing rate on bone-like apatite formation on porous calcium phosphate ceramics].

PubMed

Duan, You-rong; Liu, Ke-wei; Chen, Ji-yong; Zhang, Xing-dong

2002-06-01

Objective. Bone-like apatite formation on the surface of calcium phosphate ceramics was believed to be the necessary step that new bone grows on the ceramics and to be relative to the osteoinductivity of the material. This study aimed at investigating the influence of the flow rate of simulated body fluid (SBF) (2 ml/min) in skeletal muscle upon the formation of bone-like apatite on porous calcium phosphate ceramics. Method. The dynamic condition was realized by controlling the SBF flowing in/out of the sample chamber of 100 ml. The flow rate of 2 ml/min is close to that in human muscle environment. The pH and inorganic ionic composition of SBF are close to those of human body fluid. Result. Bone-like apatite formation was relatively easier to occur in static SBF than in dynamic SBF. Experiment with flowing SBF (dynamic SBF) is better in mimicking the living body fluid than static SBF. Conclusion. The results from dynamic SBF may more truly show the relation between apatite layer formation and osteoinduction in biomaterials than that from in vitro experiments before.

Bone morphogenetic protein Smads signaling in mesenchymal stem cells affected by osteoinductive calcium phosphate ceramics.

PubMed

Tang, Zhurong; Wang, Zhe; Qing, Fangzhu; Ni, Yilu; Fan, Yujiang; Tan, Yanfei; Zhang, Xingdong

2015-03-01

Porous calcium phosphate ceramics (CaP ceramics) could induce ectopic bone formation which was regulated by various signal molecules. In this work, bone marrow mesenchymal stem cells (MSCs) were cultured on the surface of osteoinductive hydroxyapatite (HA) and biphasic calcium phosphate (BCP) ceramics in comparison with control (culture plate) for up to 14 days to detect the signal molecules which might be affected by the CaP ceramics. Without adding osteogenic factors, MSCs cultured on HA and BCP both expressed higher Runx2, Osterix, collagen type I, osteopontin, bone sialoprotein, and osteocalcin at various stages compared with control, thus confirmed the osteoblastic differentiation of MSCs. Later study demonstrated the messenger RNA level of bone morphogenetic protein 2 (BMP2) and BMP4 were also significantly enhanced by HA and BCP. Furthermore, Smad1, 4, 5, and Dlx5, the main molecules in the BMP/Smads signaling pathway, were upregulated by HA and BCP. Moreover, the higher expression of Smads and BMP2, 4 in BCP over HA, corresponded to the better performance of BCP in stimulating in vitro osteoblastic differentiation of MSCs. This was in accordance with the better osteoinductivity of BCP over HA in vivo. Altogether, these results implied that the CaP ceramics may initiate the osteoblastic differentiation of MSCs by influencing the expression of molecules in BMP/Smads pathway. © 2014 Wiley Periodicals, Inc.

Biphasic catalysis in water/carbon dioxide micellar systems

DOEpatents

Jacobson, Gunilla B.; Tumas, William; Johnston, Keith P.

2002-01-01

A process is provided for catalyzing an organic reaction to form a reaction product by placing reactants and a catalyst for the organic reaction, the catalyst of a metal complex and at least one ligand soluble within one of the phases of said aqueous biphasic system, within an aqueous biphasic system including a water phase, a dense phase fluid, and a surfactant adapted for forming an emulsion or microemulsion within the aqueous biphasic system, the reactants soluble within one of the phases of the aqueous biphasic system and convertible in the presence of the catalyst to a product having low solubility in the phase in which the catalyst is soluble; and, maintaining the aqueous biphasic system under pressures, at temperatures, and for a period of time sufficient for the organic reaction to occur and form the reaction product and to maintain sufficient density on the dense phase fluid, the reaction product characterized as having low solubility in the phase in which the catalyst is soluble.

Comparison between FEBio and Abaqus for biphasic contact problems.

PubMed

Meng, Qingen; Jin, Zhongmin; Fisher, John; Wilcox, Ruth

2013-09-01

Articular cartilage plays an important role in the function of diarthrodial joints. Computational methods have been used to study the biphasic mechanics of cartilage, and Abaqus has been one of the most widely used commercial software packages for this purpose. A newly developed open-source finite element solver, FEBio, has been developed specifically for biomechanical applications. The aim of this study was to undertake a direct comparison between FEBio and Abaqus for some practical contact problems involving cartilage. Three model types, representing a porous flat-ended indentation test, a spherical-ended indentation test, and a conceptual natural joint contact model, were compared. In addition, a parameter sensitivity study was also performed for the spherical-ended indentation test to investigate the effects of changes in the input material properties on the model outputs, using both FEBio and Abaqus. Excellent agreement was found between FEBio and Abaqus for all of the model types and across the range of material properties that were investigated.

Comparison between FEBio and Abaqus for biphasic contact problems

PubMed Central

Jin, Zhongmin; Fisher, John; Wilcox, Ruth

2013-01-01

Articular cartilage plays an important role in the function of diarthrodial joints. Computational methods have been used to study the biphasic mechanics of cartilage, and Abaqus has been one of the most widely used commercial software packages for this purpose. A newly developed open-source finite element solver, FEBio, has been developed specifically for biomechanical applications. The aim of this study was to undertake a direct comparison between FEBio and Abaqus for some practical contact problems involving cartilage. Three model types, representing a porous flat-ended indentation test, a spherical-ended indentation test, and a conceptual natural joint contact model, were compared. In addition, a parameter sensitivity study was also performed for the spherical-ended indentation test to investigate the effects of changes in the input material properties on the model outputs, using both FEBio and Abaqus. Excellent agreement was found between FEBio and Abaqus for all of the model types and across the range of material properties that were investigated. PMID:23804955

Mediated water electrolysis in biphasic systems.

PubMed

Scanlon, Micheál D; Peljo, Pekka; Rivier, Lucie; Vrubel, Heron; Girault, Hubert H

2017-08-30

The concept of efficient electrolysis by linking photoelectrochemical biphasic H 2 evolution and water oxidation processes in the cathodic and anodic compartments of an H-cell, respectively, is introduced. Overpotentials at the cathode and anode are minimised by incorporating light-driven elements into both biphasic reactions. The concepts viability is demonstrated by electrochemical H 2 production from water splitting utilising a polarised water-organic interface in the cathodic compartment of a prototype H-cell. At the cathode the reduction of decamethylferrocenium cations ([Cp 2 *Fe (III) ] + ) to neutral decamethylferrocene (Cp 2 *Fe (II) ) in 1,2-dichloroethane (DCE) solvent takes place at the solid electrode/oil interface. This electron transfer process induces the ion transfer of a proton across the immiscible water/oil interface to maintain electroneutrality in the oil phase. The oil-solubilised proton immediately reacts with Cp 2 *Fe (II) to form the corresponding hydride species, [Cp 2 *Fe (IV) (H)] + . Subsequently, [Cp 2 *Fe (IV) (H)] + spontaneously undergoes a chemical reaction in the oil phase to evolve hydrogen gas (H 2 ) and regenerate [Cp 2 *Fe (III) ] + , whereupon this catalytic Electrochemical, Chemical, Chemical (ECC') cycle is repeated. During biphasic electrolysis, the stability and recyclability of the [Cp 2 *Fe (III) ] + /Cp 2 *Fe (II) redox couple were confirmed by chronoamperometric measurements and, furthermore, the steady-state concentration of [Cp 2 *Fe (III) ] + monitored in situ by UV/vis spectroscopy. Post-biphasic electrolysis, the presence of H 2 in the headspace of the cathodic compartment was established by sampling with gas chromatography. The rate of the biphasic hydrogen evolution reaction (HER) was enhanced by redox electrocatalysis in the presence of floating catalytic molybdenum carbide (Mo 2 C) microparticles at the immiscible water/oil interface. The use of a superhydrophobic organic electrolyte salt was critical to

Enhanced Osteogenic and Vasculogenic Differentiation Potential of Human Adipose Stem Cells on Biphasic Calcium Phosphate Scaffolds in Fibrin Gels

PubMed Central

2016-01-01

For bone tissue engineering synthetic biphasic calcium phosphate (BCP) with a hydroxyapatite/β-tricalcium phosphate (HA/β-TCP) ratio of 60/40 (BCP60/40) is successfully clinically applied, but the high percentage of HA may hamper efficient scaffold remodelling. Whether BCP with a lower HA/β-TCP ratio (BCP20/80) is more desirable is still unclear. Vascular development is needed before osteogenesis can occur. We aimed to test the osteogenic and/or vasculogenic differentiation potential as well as degradation of composites consisting of human adipose stem cells (ASCs) seeded on BCP60/40 or BCP20/80 incorporated in fibrin gels that trigger neovascularization for bone regeneration. ASC attachment to BCP60/40 and BCP20/80 within 30 min was similar (>93%). After 11 days of culture BCP20/80-based composites showed increased alkaline phosphatase activity and DMP1 gene expression, but not RUNX2 and osteonectin expression, compared to BCP60/40-based composites. BCP20/80-based composites also showed enhanced expression of the vasculogenic markers CD31 and VEGF189, but not VEGF165 and endothelin-1. Collagen-1 and collagen-3 expression was similar in both composites. Fibrin degradation was increased in BCP20/80-based composites at day 7. In conclusion, BCP20/80-based composites showed enhanced osteogenic and vasculogenic differentiation potential compared to BCP60/40-based composites in vitro, suggesting that BCP20/80-based composites might be more promising for in vivo bone augmentation than BCP60/40-based composites. PMID:27547223

Quantitative Kinetics Evaluation of Blocks Versus Granules of Biphasic Calcium Phosphate Scaffolds (HA/β-TCP 30/70) by Synchrotron Radiation X-ray Microtomography: A Human Study.

PubMed

Giuliani, Alessandra; Manescu, Adrian; Mohammadi, Sara; Mazzoni, Serena; Piattelli, Adriano; Mangano, Francesco; Iezzi, Giovanna; Mangano, Carlo

2016-02-01

Successful bone regeneration using both granules and blocks of biphasic calcium phosphate materials has been reported in the recent literature, in some clinical applications for maxillary sinus elevation, but the long-term kinetics of bone regeneration has still not been fully investigated. Twenty-four bilateral sinus augmentation procedures were performed and grafted with hydroxyapatite/β-tricalcium phosphate 30/70, 12 with granules and 12 with blocks. The samples were retrieved at different time points and were evaluated for bone regeneration, graft resorption, neovascularization, and morphometric parameters by computed microtomography and histology. A large amount of newly formed bone was detected in the retrieved specimens, together with a good rate of biomaterial resorption and the formation of a homogeneous and rich net of new vessels. The morphometric values were comparable at 5/6 months from grafting but, 9 months after grafting, revealed that the block-based specimens mimicked slightly better than granule-based samples the healthy native bone of the maxillary site. The scaffold morphology was confirmed to influence the long-term kinetics of bone regeneration.

Biomimetic Coating on Porous Alumina for Tissue Engineering: Characterisation by Cell Culture and Confocal Microscopy

PubMed Central

Kolos, Elizabeth; Ruys, Andrew J

2015-01-01

In this study porous alumina samples were prepared and then coated using the biomimetic coating technique using a five times Simulated Body Fluid (5.0SBF) as the growth solution. A coating was achieved after pre-treatment with concentrated acid. From elemental analysis, the coating contained calcium and phosphorous, but also sodium and chlorine. Halite was identified by XRD, a sodium chloride phase. Sintering was done to remove the halite phase. Once halite was burnt off, the calcium phosphate crystals were not covered with halite and, therefore, the apatite phases can be clearly observed. Cell culturing showed sufficient cell attachment to the less porous alumina, Sample B, that has more calcium phosphate growth, while the porous alumina, Sample A, with minimal calcium phosphate growth attained very little cell attachment. This is likely due to the contribution that calcium phosphate plays in the attachment of bone-like cells to a bioinert ceramic such as alumina. These results were repeated on both SEM and confocal microscopy analysis. Confocal microscopy was a novel characterisation approach which gave useful information and was a visual aid.

Novel cyclodextrin nanosponges for delivery of calcium in hyperphosphatemia.

PubMed

Shende, Pravin; Deshmukh, Kiran; Trotta, Fransesco; Caldera, Fabrizio

2013-11-01

Cyclodextrin nanosponges are solid, porous nanoparticulate three dimensional structures, have been used as delivery system of different drugs. In this work, new cyclodextrin-based nanosponges of calcium carbonate were prepared by polymer condensation method to release the calcium in controlled manner in the treatment of hyperphosphatemia as novel carriers. SEM measurements revealed their roughly spherical shape, porous nature and mean particle size of about 400 nm. Zeta potentials of the nanosponges were sufficiently high to obtain stable formulations. The encapsulation efficiencies of calcium in nanosponge formulations were found to be 81-95%. The moisture contents of the nanosponges were in the range of 0.1-0.7%. The optimized formulation produces enteric and controlled release kinetics of calcium in the management and treatment of hyperphosphatemia. It was also observed that calcium ions bound efficiently to free phosphate in a pH-dependent fashion especially at pH 7. In accelerated stability study no significant changes occurred in physical appearance, size and nature of drug in formulation for 3 months. The results of FTIR and DSC confirmed that calcium carbonate was encapsulated in nanosponges structure. Copyright © 2013 Elsevier B.V. All rights reserved.

Aminoglycoside antibiotics as a tool for the study of the biological role of calcium ions. Historical overview.

PubMed

Corrado, A P; de Morais, I P; Prado, W A

1989-01-01

Beginning with the pioneering work of Vital-Brazil and Corrado (1957), which suggested a possible interaction between aminoglycoside antibiotics (AGA) and calcium ions at the neuromuscular junction, the authors review the studies that demonstrated the existence of a competitive antagonism between AGA and calcium ions. In view of the low liposolubility of AGA and their inability to cross biological membranes, this antagonism seems to occur exclusively at calcium-binding sites at the level of the outer opening of calcium channels of the N-subtype, which are also the sites of interaction of omega-conotoxin. Being highly water soluble, AGA are easily removed from their binding sites with a consequent rapid reversal of their effects, a factor of primary importance to explain their wide use as tools in the pharmacological analysis of the study of the biological role of calcium ion on the membrane's outer surface. This use has advantages over the use of inorganic di- and trivalent cations such as Mg2+, Mn2+, Cd2+, Ni2+, La3+, etc., since the latter, though they are considered to be the most specific competitive antagonists of calcium ions, may induce biphasic effects due to their ability to cross the membranes and replace calcium and/or increase intracellular calcium concentration. The performance of AGA is also superior when compared with the so-called "specific" organic calcium antagonists--verapamil and nifedipine derivatives--since the latter, in addition to inducing possible biphasic effects, antagonize calcium in a non-competitive manner. Finally, the authors remark that AGA-Ca2+ antagonism relevance is not limited only to basic aspects and that it may have therapeutic implications since it provides alternatives for reducing the toxic adverse effects of this important group of antibiotics.

Evaluation of bone regeneration with biphasic calcium phosphate substitute implanted with bone morphogenetic protein 2 and mesenchymal stem cells in a rabbit calvarial defect model.

PubMed

Kim, Beom-Su; Choi, Moon-Ki; Yoon, Jung-Hoon; Lee, Jun

2015-07-01

The aim of this study was to evaluate the in vivo osteogenic potential of biphasic calcium phosphate (BCP), bone morphogenetic protein 2 (BMP-2), and/or mesenchymal stem cell (MSC) composites by using a rabbit calvarial defect model. Bone formation was assessed by using three different kinds of implants in rabbit calvarial defects, BCP alone, BCP/recombinant human (rh) BMP-2, and BCP/rhBMP-2/MSCs composite. The implants were harvested after 2 or 8 weeks, and the area of new bone formation was quantified by micro-computed tomography (micro-CT) and histologic studies. The highest bone formation was achieved with the BCP/rhBMP-2/MSCs treatment, and it was significantly higher than that achieved with the empty or BCP-alone treatment. The quantity of new bone at 8 weeks was greater than at 4 weeks in each group. The relative density of osteocalcin immunoreactivity also increased during this interval. These results indicate that the combination of BCP, rhBMP-2, and MSCs synergistically enhances osteogenic potential during the early healing period and could be used as a bone graft substitute. Copyright © 2015 Elsevier Inc. All rights reserved.

Comparative Efficacies of Collagen-Based 3D Printed PCL/PLGA/β-TCP Composite Block Bone Grafts and Biphasic Calcium Phosphate Bone Substitute for Bone Regeneration.

PubMed

Hwang, Kyoung-Sub; Choi, Jae-Won; Kim, Jae-Hun; Chung, Ho Yun; Jin, Songwan; Shim, Jin-Hyung; Yun, Won-Soo; Jeong, Chang-Mo; Huh, Jung-Bo

2017-04-17

The purpose of this study was to compare bone regeneration and space maintaining ability of three-dimensional (3D) printed bone grafts with conventional biphasic calcium phosphate (BCP). After mixing polycaprolactone (PCL), poly (lactic-co-glycolic acid) (PLGA), and β-tricalcium phosphate (β-TCP) in a 4:4:2 ratio, PCL/PLGA/β-TCP particulate bone grafts were fabricated using 3D printing technology. Fabricated particulate bone grafts were mixed with atelocollagen to produce collagen-based PCL/PLGA/β-TCP composite block bone grafts. After formation of calvarial defects 8 mm in diameter, PCL/PLGA/β-TCP composite block bone grafts and BCP were implanted into bone defects of 32 rats. Although PCL/PLGA/β-TCP composite block bone grafts were not superior in bone regeneration ability compared to BCP, the results showed relatively similar performance. Furthermore, PCL/PLGA/β-TCP composite block bone grafts showed better ability to maintain bone defects and to support barrier membranes than BCP. Therefore, within the limitations of this study, PCL/PLGA/β-TCP composite block bone grafts could be considered as an alternative to synthetic bone grafts available for clinical use.

Repair of Cranial Bone Defects Using rhBMP2 and Submicron Particle of Biphasic Calcium Phosphate Ceramics with Through-Hole

PubMed Central

Jeong, Byung-Chul; Choi, Hyuck; Hur, Sung-Woong; Kim, Jung-Woo; Oh, Sin-Hye; Kim, Hyun-Seung; Song, Soo-Chang; Lee, Keun-Bae; Park, Kwang-Bum; Koh, Jeong-Tae

2015-01-01

Recently a submicron particle of biphasic calcium phosphate ceramic (BCP) with through-hole (donut-shaped BCP (d-BCP)) was developed for improving the osteoconductivity. This study was performed to examine the usefulness of d-BCP for the delivery of osteoinductive rhBMP2 and the effectiveness on cranial bone regeneration. The d-BCP was soaked in rhBMP2 solution and then freeze-dried. Scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), and Raman spectroscopy analyses confirmed that rhBMP2 was well delivered onto the d-BCP surface and the through-hole. The bioactivity of the rhBMP2/d-BCP composite was validated in MC3T3-E1 cells as an in vitro model and in critical-sized cranial defects in C57BL/6 mice. When freeze-dried d-BCPs with rhBMP2 were placed in transwell inserts and suspended above MC3T3-E1, alkaline phosphatase activity and osteoblast-specific gene expression were increased compared to non-rhBMP2-containing d-BCPs. For evaluating in vivo effectiveness, freeze-dried d-BCPs with or without rhBMP2 were implanted into critical-sized cranial defects. Microcomputed tomography and histologic analysis showed that rhBMP2-containing d-BCPs significantly enhanced cranial bone regeneration compared to non-rhBMP2-containing control. These results suggest that a combination of d-BCP and rhBMP2 can accelerate bone regeneration, and this could be used to develop therapeutic strategies in hard tissue healing. PMID:26491693

Repair of Cranial Bone Defects Using rhBMP2 and Submicron Particle of Biphasic Calcium Phosphate Ceramics with Through-Hole.

PubMed

Jeong, Byung-Chul; Choi, Hyuck; Hur, Sung-Woong; Kim, Jung-Woo; Oh, Sin-Hye; Kim, Hyun-Seung; Song, Soo-Chang; Lee, Keun-Bae; Park, Kwang-Bum; Koh, Jeong-Tae

2015-01-01

Recently a submicron particle of biphasic calcium phosphate ceramic (BCP) with through-hole (donut-shaped BCP (d-BCP)) was developed for improving the osteoconductivity. This study was performed to examine the usefulness of d-BCP for the delivery of osteoinductive rhBMP2 and the effectiveness on cranial bone regeneration. The d-BCP was soaked in rhBMP2 solution and then freeze-dried. Scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), and Raman spectroscopy analyses confirmed that rhBMP2 was well delivered onto the d-BCP surface and the through-hole. The bioactivity of the rhBMP2/d-BCP composite was validated in MC3T3-E1 cells as an in vitro model and in critical-sized cranial defects in C57BL/6 mice. When freeze-dried d-BCPs with rhBMP2 were placed in transwell inserts and suspended above MC3T3-E1, alkaline phosphatase activity and osteoblast-specific gene expression were increased compared to non-rhBMP2-containing d-BCPs. For evaluating in vivo effectiveness, freeze-dried d-BCPs with or without rhBMP2 were implanted into critical-sized cranial defects. Microcomputed tomography and histologic analysis showed that rhBMP2-containing d-BCPs significantly enhanced cranial bone regeneration compared to non-rhBMP2-containing control. These results suggest that a combination of d-BCP and rhBMP2 can accelerate bone regeneration, and this could be used to develop therapeutic strategies in hard tissue healing.

Generation of highly stable and active strong base sites on organized nano-porous alumina by calcium oxide

NASA Astrophysics Data System (ADS)

Tarlani, Aliakbar; Zarabadi, Mir Pouyan

2013-02-01

In a new approach, strong basic sites has been successfully prepared by loading of calcium nitrate (Ca) on organized nano-porous alumina (ONPA). The prepared CaONPAs were characterized by low-angle X-ray diffraction (XRD), N2 adsorption-desorption isotherms (Brunauer-Emmett-Teller (BET)-Barret-Joyner-Halenda (BJH)), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). Measuring of the amount of the basic sites and the basicity was carried out by titration method, temperature-programmed desorption (TPD-CO2) and Hammett indicators. Resistance of the basic sites was also tested by washing with water. N2 sorption measurements showed that supporting of the calcium nitrate on ONPA can lead to the bimodal porosity at lower loading. BET surface area of the bare ONPA was 212 m2/g which decreased to 111 m2/g for the 25% of loading of Ca (25CaONPA). The results pointed out that CaONPA samples have basicity between 18.4 < H_ < 22 for 15 and 25% of loadings and well-preserved of the basicity after washing with water especially for 5 and 15% samples. Also no crystalline phase of CaO was observed for 25CaONPA which was calcined at 600 °C.

Multi-scale osteointegration and neovascularization of biphasic calcium phosphate bone scaffolds

NASA Astrophysics Data System (ADS)

Lan, Sheeny K.

Bone grafts are utilized clinically to guide tissue regeneration. Autologous bone and allogeneic bone are the current clinical standards. However, there are significant limitations to their use. To address the need for alternatives to autograft and allograft, researchers have worked to develop synthetic grafts, also referred to as scaffolds. Despite extensive efforts in this area, a gap persists between basic research and clinical application. In particular, solutions for repairing critical size and/or load-bearing defects are lacking. The aim of this thesis work was to address two critical barriers preventing design of successful tissue engineering constructs for bone regeneration within critical size and/or load-bearing defects. Those barriers are insufficient osteointegration and slow neovascularization. In this work, the effects of scaffold microporosity, recombinant human bone morphogenetic protein-2 delivery and endothelial colony forming cell vasculogenesis were evaluated in the context of bone formation in vivo. This was accomplished to better understand the role of these factors in bone regeneration, which may translate to improvements in tissue engineering construct design. Biphasic calcium phosphate (BCP) scaffolds with controlled macro- and microporosity were implanted in porcine mandibular defects. Evaluation of the BCP scaffolds after in vivo implantation showed, for the first time, osteocytes embedded in bone within scaffold micropores (< 10 microm) as well as the most extensive bone growth into micropores to date with bone penetration throughout rods 394 microm in diameter. The result is the first truly osteointegrated bone scaffolds with integration occurring at both the macro and micro length scales, leaving no "dead space" or discontinuities of bone in the defect site. The scaffold forms a living composite upon integration with regenerating bone and this has significant implications with regard to improved scaffold mechanical properties. The

Novel Development of Phosphate Treated Porous Hydroxyapatite.

PubMed

Doi, Kazuya; Abe, Yasuhiko; Kobatake, Reiko; Okazaki, Yohei; Oki, Yoshifumi; Naito, Yoshihito; Prananingrum, Widyasri; Tsuga, Kazuhiro

2017-12-08

Phosphoric acid-etching treatment to the hydroxyapatite (HA) surface can modify the solubility calcium structure. The aim of the present study was to develop phosphate treated porous HA, and the characteristic structures and stimulation abilities of bone formation were evaluated to determine its suitability as a new type of bone graft material. Although the phosphoric acid-etching treatment did not alter the three-dimensional structure, a micrometer-scale rough surface topography was created on the porous HA surface. Compared to porous HA, the porosity of phosphate treated porous HA was slightly higher and the mechanical strength was lower. Two weeks after placement of the cylindrical porous or phosphate treated porous HA in a rabbit femur, newly formed bone was detected in both groups. At the central portion of the bone defect area, substantial bone formation was detected in the phosphate treated porous HA group, with a significantly higher bone formation ratio than detected in the porous HA group. These results indicate that phosphate treated porous HA has a superior surface topography and bone formation abilities in vivo owing to the capacity for both osteoconduction and stimulation abilities of bone formation conferred by phosphoric acid etching.

Novel Development of Phosphate Treated Porous Hydroxyapatite

PubMed Central

Doi, Kazuya; Abe, Yasuhiko; Kobatake, Reiko; Okazaki, Yohei; Oki, Yoshifumi; Naito, Yoshihito; Prananingrum, Widyasri; Tsuga, Kazuhiro

2017-01-01

Phosphoric acid-etching treatment to the hydroxyapatite (HA) surface can modify the solubility calcium structure. The aim of the present study was to develop phosphate treated porous HA, and the characteristic structures and stimulation abilities of bone formation were evaluated to determine its suitability as a new type of bone graft material. Although the phosphoric acid-etching treatment did not alter the three-dimensional structure, a micrometer-scale rough surface topography was created on the porous HA surface. Compared to porous HA, the porosity of phosphate treated porous HA was slightly higher and the mechanical strength was lower. Two weeks after placement of the cylindrical porous or phosphate treated porous HA in a rabbit femur, newly formed bone was detected in both groups. At the central portion of the bone defect area, substantial bone formation was detected in the phosphate treated porous HA group, with a significantly higher bone formation ratio than detected in the porous HA group. These results indicate that phosphate treated porous HA has a superior surface topography and bone formation abilities in vivo owing to the capacity for both osteoconduction and stimulation abilities of bone formation conferred by phosphoric acid etching. PMID:29292788

Changes in transthoracic impedance during sequential biphasic defibrillation.

PubMed

Deakin, Charles D; Ambler, Jonathan J S; Shaw, Steven

2008-08-01

Sequential monophasic defibrillation reduces transthoracic impedance (TTI) and progressively increases current flow for any given energy level. The effect of sequential biphasic shocks on TTI is unknown. We therefore studied patients undergoing elective cardioversion using a biphasic waveform to establish whether this is a phenomenon seen in the clinical setting. Adults undergoing elective DC cardioversion for atrial flutter or fibrillation received sequential transthoracic shocks using an escalating protocol (70J, 100J, 150J, 200J, and 300J) with a truncated exponential biphasic waveform. TTI was calculated through the defibrillator circuit and recorded electronically. Successful cardioversion terminated further defibrillation shocks. A total of 58 patients underwent elective cardioversion. Cardioversion was successful in 93.1% patients. First shock TTI was 92.2 [52.0-126.0]Omega (n=58) and decreased significantly with each sequential shock. Mean TTI in patients receiving five shocks (n=5) was 85.0Omega. Sequential biphasic defibrillation decreases TTI in a similar manner to that seen with monophasic waveforms. The effect is likely during defibrillation during cardiac arrest by the quick succession in which shocks are delivered and the lack of cutaneous blood flow which limits the inflammatory response. The ability of biphasic defibrillators to adjust their waveform according to TTI is likely to minimise any effect of these findings on defibrillation efficacy.

New porous monolithic membranes based on supported ionic liquid-like phases for oil/water separation and homogenous catalyst immobilisation.

PubMed

Porcar, Raúl; Nuevo, Daniel; García-Verdugo, Eduardo; Lozano, Pedro; Sanchez-Marcano, José; Burguete, M Isabel; Luis, Santiago V

2018-03-07

Porous monolithic advanced functional materials based on supported ionic liquid-like phase (SILLP) systems were used for the preparation of oleophilic and hydrophobic cylindrical membranes and successfully tested as eco-friendly and safe systems for oil/water separation and for the continuous integration of catalytic and separation processes in an aqueous-organic biphasic reaction system.

Biocompatibility of PCL/PLGA-BCP porous scaffold for bone tissue engineering applications.

PubMed

Thi Hiep, Nguyen; Chan Khon, Huynh; Dai Hai, Nguyen; Byong-Taek, Lee; Van Toi, Vo; Thanh Hung, Le

2017-06-01

In this study, biomimic porous polycaprolactone/poly (lactide-co-glycolide) loading biphasic tricalcium phosphate (PCL/PLGA-BCP) scaffolds were fabricated successfully by solvent evaporation method. The distribution of biphasic tricalcium phosphate (BCP) in polycaprolactone/poly (lactide-co-glycolide) (PCL/PLGA) scaffold was confirmed by micro-computed tomography (micro-CT) scanning, scanning electron microscope (SEM) observation and Energy-dispersive X-ray Spectroscopy (EDS) analysis. The hydrophilicity of the scaffolds was confirmed by contact angle measurement. In in vitro experiments, proliferation of human bone marrow mesenchymal stem cell (hBMSCs) and its osteoblastic differentiation on scaffold were assessed for 1, 2 and 3 weeks using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, fluorescence observation, hematoxylin & eosin (H&E) staining and real-time polymerase chain reaction (RT-PCR). In in vivo experiments, ossification was observed using micro-CT analysis and histological staining.

Behavior of osteoblast-like cells on calcium-deficient hydroxyapatite ceramics composed of particles with different shapes and sizes.

PubMed

Kamitakahara, Masanobu; Uno, Yuika; Ioku, Koji

2014-01-01

In designing the biomaterials, it is important to control their surface morphologies, because they affect the interactions between the materials and cells. We previously reported that porous calcium-deficient hydroxyapatite (HA) ceramics composed of rod-like particles had advantages over sintered porous HA ceramics; however, the effects of the surface morphology of calcium-deficient HA ceramics on cell behavior have remained unclear. Using a hydrothermal process, we successfully prepared porous calcium-deficient HA ceramics with different surface morphologies, composed of plate-like particles of 200-300, 500-800 nm, or 2-3 μm in width and rod-like particles of 1 or 3-5 μm in width, respectively. The effects of these surface morphologies on the behavior of osteoblast-like cells were examined. Although the numbers of cells adhered to the ceramic specimens did not differ significantly among the specimens, the proliferation rates of cells on the ceramics decreased with decreasing particle size. Our results reveal that controlling the surface morphology that is governed by particle shape and size is important for designing porous calcium-deficient HA ceramics.

Nano-biphasic calcium phosphate/polyvinyl alcohol composites with enhanced bioactivity for bone repair via low-temperature three-dimensional printing and loading with platelet-rich fibrin.

PubMed

Song, Yue; Lin, Kaifeng; He, Shu; Wang, Chunmei; Zhang, Shuaishuai; Li, Donglin; Wang, Jimeng; Cao, Tianqing; Bi, Long; Pei, Guoxian

2018-01-01

As a newly emerging three-dimensional (3D) printing technology, low-temperature robocasting can be used to fabricate geometrically complex ceramic scaffolds at low temperatures. Here, we aimed to fabricate 3D printed ceramic scaffolds composed of nano-biphasic calcium phosphate (BCP), polyvinyl alcohol (PVA), and platelet-rich fibrin (PRF) at a low temperature without the addition of toxic chemicals. Corresponding nonprinted scaffolds were prepared using a freeze-drying method. Compared with the nonprinted scaffolds, the printed scaffolds had specific shapes and well-connected internal structures. The incorporation of PRF enabled both the sustained release of bioactive factors from the scaffolds and improved biocompatibility and biological activity toward bone marrow-derived mesenchymal stem cells (BMSCs) in vitro. Additionally, the printed BCP/PVA/PRF scaffolds promoted significantly better BMSC adhesion, proliferation, and osteogenic differentiation in vitro than the printed BCP/PVA scaffolds. In vivo, the printed BCP/PVA/PRF scaffolds induced a greater extent of appropriate bone formation than the printed BCP/PVA scaffolds and nonprinted scaffolds in a critical-size segmental bone defect model in rabbits. These experiments indicate that low-temperature robocasting could potentially be used to fabricate 3D printed BCP/PVA/PRF scaffolds with desired shapes and internal structures and incorporated bioactive factors to enhance the repair of segmental bone defects.

Biphasic Scaffolds from Marine Collagens for Regeneration of Osteochondral Defects.

PubMed

Bernhardt, Anne; Paul, Birgit; Gelinsky, Michael

2018-03-13

Collagens of marine origin are applied increasingly as alternatives to mammalian collagens in tissue engineering. The aim of the present study was to develop a biphasic scaffold from exclusively marine collagens supporting both osteogenic and chondrogenic differentiation and to find a suitable setup for in vitro chondrogenic and osteogenic differentiation of human mesenchymal stroma cells (hMSC). Biphasic scaffolds from biomimetically mineralized salmon collagen and fibrillized jellyfish collagen were fabricated by joint freeze-drying and crosslinking. Different experiments were performed to analyze the influence of cell density and TGF-β on osteogenic differentiation of the cells in the scaffolds. Gene expression analysis and analysis of cartilage extracellular matrix components were performed and activity of alkaline phosphatase was determined. Furthermore, histological sections of differentiated cells in the biphasic scaffolds were analyzed. Stable biphasic scaffolds from two different marine collagens were prepared. An in vitro setup for osteochondral differentiation was developed involving (1) different seeding densities in the phases; (2) additional application of alginate hydrogel in the chondral part; (3) pre-differentiation and sequential seeding of the scaffolds and (4) osteochondral medium. Spatially separated osteogenic and chondrogenic differentiation of hMSC was achieved in this setup, while osteochondral medium in combination with the biphasic scaffolds alone was not sufficient to reach this ambition. Biphasic, but monolithic scaffolds from exclusively marine collagens are suitable for the development of osteochondral constructs.

Calcification capacity of porous pHEMA-TiO₂ composite hydrogels.

PubMed

Li, Chao; Zheng, Yu-Feng; Lou, Xia

2009-11-01

Many investigations have been attempted to promote calcification of synthetic polymers for applications as orthopaedic and dental implants. In this study, novel titanium dioxide (TiO(2)) reinforced porous poly(2-hydroxyethyl methacrylate) (pHEMA) hydrogels were synthesized. Calcification capacity of the composite polymers was examined using light microscopy, scanning electron microscopy and Fourier transform infrared spectroscopy after incubation of the materials in a simulated body fluid up to 53 days. Mechanical strength, porosity and in vitro cytotoxicity were also investigated. Calcification capacity of porous pHEMA was significantly enhanced by the addition of TiO(2) particulates. Infiltration of calcium phosphate, up to 1000 mum, was observed. The diffusion capacity of calcium ions was affected by the porosity and the interconnectivity of pores in the hydrogel polymers which were influenced by the presence of TiO(2) and the monomer concentration. Cell viability tests indicated that porous hydrogels containing 7.5% TiO(2) were not toxic to 3T3 fibroblast cells. These results demonstrate that incorporating TiO(2) nanoparticulates can promote enhanced formation of calcium phosphate whilst maintaining the porosity and interconnectivity of the hydrogel polymers and would be very useful for the development of orthopaedic tissue engineering scaffolds.

Ascending-ramp biphasic waveform has a lower defibrillation threshold and releases less troponin I than a truncated exponential biphasic waveform.

PubMed

Huang, Jian; Walcott, Gregory P; Ruse, Richard B; Bohanan, Scott J; Killingsworth, Cheryl R; Ideker, Raymond E

2012-09-11

We tested the hypothesis that the shape of the shock waveform affects not only the defibrillation threshold but also the amount of cardiac damage. Defibrillation thresholds were determined for 11 waveforms-3 ascending-ramp waveforms, 3 descending-ramp waveforms, 3 rectilinear first-phase biphasic waveforms, a Gurvich waveform, and a truncated exponential biphasic waveform-in 6 pigs with electrodes in the right ventricular apex and superior vena cava. The ascending, descending, and rectilinear waveforms had 4-, 8-, and 16-millisecond first phases and a 3.5-millisecond rectilinear second phase that was half the voltage of the first phase. The exponential biphasic waveform had a 60% first-phase and a 50% second-phase tilt. In a second study, we attempted to defibrillate after 10 seconds of ventricular fibrillation with a single ≈30-J shock (6 pigs successfully defibrillated with 8-millisecond ascending, 8-millisecond rectilinear, and truncated exponential biphasic waveforms). Troponin I blood levels were determined before and 2 to 10 hours after the shock. The lowest-energy defibrillation threshold was for the 8-milliseconds ascending ramp (14.6±7.3 J [mean±SD]), which was significantly less than for the truncated exponential (19.6±6.3 J). Six hours after shock, troponin I was significantly less for the ascending-ramp waveform (0.80±0.54 ng/mL) than for the truncated exponential (1.92±0.47 ng/mL) or the rectilinear waveform (1.17±0.45 ng/mL). The ascending ramp has a significantly lower defibrillation threshold and at ≈30 J causes 58% less troponin I release than the truncated exponential biphasic shock. Therefore, the shock waveform affects both the defibrillation threshold and the amount of cardiac damage.

[Subantral augmentation with porous titanium in experiment and clinic].

PubMed

Sirak, S V; Shchetinin, E V; Sletov, A A

2016-01-01

The article discusses the use of porous titanium for subantral augmentation. Experimental study was conducted on 12 yearling rams. Subantral augmentation using porous titanium was performed in 33 patients. In the control group consisting of 14 patients calcium phosphates and bone collagen based agents ("Bio-Оss" and "Collost") were used. In the main and control groups 46 and 32 implant were placed, respectively. Pilot histological and clinical studies proved that the granules of porous titanium are biocompatible with bone tissue, provide the optimal surface microrelief, thus creating good conditions for adhesion, expansion and migration of osteoforming cells, have negligible kinetics of resorption, are porous to ensure effective neovascularization of de novo formed bone tissue. Porous titanium is an effective alternative material for subantral bone augmentation for dental implantation and reconstructive operations on the maxillary sinus.

Nonlinear estimation of parameters in biphasic Arrhenius plots.

PubMed

Puterman, M L; Hrboticky, N; Innis, S M

1988-05-01

This paper presents a formal procedure for the statistical analysis of data on the thermotropic behavior of membrane-bound enzymes generated using the Arrhenius equation and compares the analysis to several alternatives. Data is modeled by a bent hyperbola. Nonlinear regression is used to obtain estimates and standard errors of the intersection of line segments, defined as the transition temperature, and slopes, defined as energies of activation of the enzyme reaction. The methodology allows formal tests of the adequacy of a biphasic model rather than either a single straight line or a curvilinear model. Examples on data concerning the thermotropic behavior of pig brain synaptosomal acetylcholinesterase are given. The data support the biphasic temperature dependence of this enzyme. The methodology represents a formal procedure for statistical validation of any biphasic data and allows for calculation of all line parameters with estimates of precision.

Preparation of flexible bone tissue scaffold utilizing sea urchin test and collagen.

PubMed

Manchinasetty, Naga Vijaya Lakshmi; Oshima, Sho; Kikuchi, Masanori

2017-10-13

Gonads of sea urchin are consumed in Japan and some countries as food and most parts including its tests are discarded as marine wastes. Therefore, utilization of them as functional materials would reduce the waste as well as encourage Japanese fishery. In this study, magnesium containing calcite granules collected from sea urchin tests were hydrothermally phosphatized and the obtained granules were identified as approximately 82% in mass of magnesium containing β-tricalcium phosphate and 18% in mass of nonstoichiometric hydroxyapatite, i.e., a biphasic calcium phosphate, maintaining the original porous network. Shape-controlled scaffolds were fabricated with the obtained biphasic calcium phosphate granules and collagen. The scaffolds showed good open porosity (83.84%) and adequate mechanical properties for handling during cell culture and subsequent operations. The MG-63 cells showed higher proliferation and osteogenic differentiation in comparison to a control material, the collagen sponge with the same size. Furthermore, cell viability assay proved that the scaffolds were not cytotoxic. These results suggest that scaffold prepared using sea urchin test derived calcium phosphate and collagen could be a potential candidate of bone void fillers for non-load bearing defects in bone reconstruction as well as scaffolds for bone tissue engineering.

Biphasic responses in multi-site phosphorylation systems.

PubMed

Suwanmajo, Thapanar; Krishnan, J

2013-12-06

Multi-site phosphorylation systems are repeatedly encountered in cellular biology and multi-site modification is a basic building block of post-translational modification. In this paper, we demonstrate how distributive multi-site modification mechanisms by a single kinase/phosphatase pair can lead to biphasic/partial biphasic dose-response characteristics for the maximally phosphorylated substrate at steady state. We use simulations and analysis to uncover a hidden competing effect which is responsible for this and analyse how it may be accentuated. We build on this to analyse different variants of multi-site phosphorylation mechanisms showing that some mechanisms are intrinsically not capable of displaying this behaviour. This provides both a consolidated understanding of how and under what conditions biphasic responses are obtained in multi-site phosphorylation and a basis for discriminating between different mechanisms based on this. We also demonstrate how this behaviour may be combined with other behaviour such as threshold and bistable responses, demonstrating the capacity of multi-site phosphorylation systems to act as complex molecular signal processors.

Nano-biphasic calcium phosphate/polyvinyl alcohol composites with enhanced bioactivity for bone repair via low-temperature three-dimensional printing and loading with platelet-rich fibrin

PubMed Central

Wang, Chunmei; Zhang, Shuaishuai; Li, Donglin; Wang, Jimeng; Cao, Tianqing; Bi, Long; Pei, Guoxian

2018-01-01

Background and aim As a newly emerging three-dimensional (3D) printing technology, low-temperature robocasting can be used to fabricate geometrically complex ceramic scaffolds at low temperatures. Here, we aimed to fabricate 3D printed ceramic scaffolds composed of nano-biphasic calcium phosphate (BCP), polyvinyl alcohol (PVA), and platelet-rich fibrin (PRF) at a low temperature without the addition of toxic chemicals. Methods Corresponding nonprinted scaffolds were prepared using a freeze-drying method. Compared with the nonprinted scaffolds, the printed scaffolds had specific shapes and well-connected internal structures. Results The incorporation of PRF enabled both the sustained release of bioactive factors from the scaffolds and improved biocompatibility and biological activity toward bone marrow-derived mesenchymal stem cells (BMSCs) in vitro. Additionally, the printed BCP/PVA/PRF scaffolds promoted significantly better BMSC adhesion, proliferation, and osteogenic differentiation in vitro than the printed BCP/PVA scaffolds. In vivo, the printed BCP/PVA/PRF scaffolds induced a greater extent of appropriate bone formation than the printed BCP/PVA scaffolds and nonprinted scaffolds in a critical-size segmental bone defect model in rabbits. Conclusion These experiments indicate that low-temperature robocasting could potentially be used to fabricate 3D printed BCP/PVA/PRF scaffolds with desired shapes and internal structures and incorporated bioactive factors to enhance the repair of segmental bone defects. PMID:29416332

Flow perfusion culture of MC3T3-E1 osteogenic cells on gradient calcium polyphosphate scaffolds with different pore sizes.

PubMed

Chen, Liang; Song, Wei; Markel, David C; Shi, Tong; Muzik, Otto; Matthew, Howard; Ren, Weiping

2016-02-01

Calcium polyphosphate is a biodegradable bone substitute. It remains a challenge to prepare porous calcium polyphosphate with desired gradient porous structures. In this study, a modified one-step gravity sintering method was used to prepare calcium polyphosphate scaffolds with desired-gradient-pore-size distribution. The differences of porous structure, mechanical strength, and degradation rate between gradient and homogenous calcium polyphosphate scaffolds were evaluated by micro-computed tomography, scanning electron microscopy, and mechanical testing. Preosteoblastic MC3T3-E1 cells were seeded onto gradient and homogenous calcium polyphosphate scaffolds and cultured in a flow perfusion bioreactor. The distribution, proliferation, and differentiation of the MC3T3-E1 cells were compared to that of homogenous calcium polyphosphate scaffolds. Though no significant difference of cell proliferation was found between the gradient and the homogenous calcium polyphosphate scaffolds, a much higher cell differentiation and mineralization were observed in the gradient calcium polyphosphate scaffolds than that of the homogenous calcium polyphosphate scaffolds, as manifested by increased alkaline phosphatase activity (p < 0.05). The improved distribution and differentiation of cultured cells within gradient scaffolds were further supported by both (18)F-fluorine micro-positron emission tomography scanning and in vitro tetracycline labeling. We conclude that the calcium polyphosphate scaffold with gradient pore sizes enhances osteogenic cell differentiation as well as mineralization. The in vivo performance of gradient calcium polyphosphate scaffolds warrants further investigation in animal bone defect models. © The Author(s) 2015.

Optimization of calcium phosphate fine ceramic powders preparation

NASA Astrophysics Data System (ADS)

Sezanova, K.; Tepavitcharova, S.; Rabadjieva, D.; Gergulova, R.; Ilieva, R.

2013-12-01

The effect of biomimetic synthesis method, reaction medium and further precursor treatments on the chemical and phase composition, crystal size and morphology of calcium phosphates was examined. Nanosized calcium phosphate precursors were biomimetically precipitated by the method of continuous precipitation in three types of reaction media at pH 8: (i) SBF as an inorganic electrolyte system; (ii) organic (glycerine) modified SBF (volume ratio of 1:1); (iii) polymer (10 g/l xanthan gum or 10 g/l guar gum) modified SBF (volume ratio of 1:1). After maturation (24 h) the samples were lyophilized, calcinated at 300°C for 3 hours, and washed with water, followed by new gelation, lyophilization and step-wise (200, 400, 600, 800, and 1000°C, each for 3 hours) sintering. The reaction medium influenced the chemical composition and particle size but not the morphology of the calcium phosphate powders. In all studied cases bi-phase calcium phosphate fine powders with well-shaped spherical grains, consisting of β-tricalcium phosphate (β-TCP) and hydroxyapatite (HA) with a Ca/P ratio of 1.3 - 1.6 were obtained. The SBF modifiers decreased the particle size of the product in the sequence guar gum ˜ xanthan gum < glycerin < SBF medium.

Generation of useful energy from process fluids using the biphase turbine

NASA Astrophysics Data System (ADS)

Helgeson, N. L.

1981-01-01

The six largest energy consuming industries in the United States were surveyed to determine the energy savings that could result from applying the Biphase turbine to industrial process streams. A national potential energy savings of 58 million barrels of oil per year (technical market) was identified. This energy is recoverable from flashing gas liquid process streams and is separate and distinct from exhaust gas waste heat recovery. The industries surveyed in this program were the petroleum chemical, primary metals, paper and pulp, stone-clay-glass, and food. It was required to determine the applicability of the Biphase turbine to flashing operations connected with process streams, to determine the energy changes associated with these flashes if carried out in a Biphase turbine, and to determine the suitability (technical and economical feasibility) of applying the Biphase turbine to these processes.

Velocity dependence of biphasic flow structuration: steady-state and oscillating flow effects

NASA Astrophysics Data System (ADS)

Tore Tallakstad, Ken; Jankov, Mihailo; Løvoll, Grunde; Toussaint, Renaud; Jørgen Mâløy, Knut; Grude Flekkøy, Eirik; Schmittbuhl, Jean; Schäfer, Gerhard; Méheust, Yves; Arendt Knudsen, Henning

2010-05-01

We study various types of biphasic flows in quasi-two-dimensional transparent porous models. These flows imply a viscous wetting fluid, and a lowly viscous one. The models are transparent, allowing the displacement process and structure to be monitored in space and time. Three different aspects will be presented: 1. In stationary biphasic flows, we study the relationship between the macroscopic pressure drop (related to relative permeability) and the average flow rate, and how this arises from the cluster size distribution of the lowly viscous fluid [1]. 2. In drainage situations, we study how the geometry of the invader can be explained, and how it gives rise to apparent dynamic capillary effects. We show how these can be explained by viscous effects on evolving geometries of invading fluid [2]. 3. We study the impact of oscillating pressure fields superimposed to a background flow over the flow regimes patterns [3]. Steady-State Two-Phase Flow in Porous Media: Statistics and Transport Properties. First, in stationary flow with a control of the flux of both fluids, we show how the pressure drop depends on the flow rate. We will show that the dynamics is dominated by the interplay between a viscous pressure field from the wetting fluid and bubble transport of a less viscous, nonwetting phase. In contrast with more studied displacement front systems, steady-state flow is in equilibrium, statistically speaking. The corresponding theoretical simplicity allows us to explain a data collapse in the cluster size distribution of lowly viscous fluid in the system, as well as the relation |?P|∞√Ca--. This allows to explain so called relative permeability effects by the morphological changes of the cluster size distribution. Influence of viscous fingering on dynamic saturation-pressure curves in porous media. Next, we study drainage in such models, and investigate the relationship between the pressure field and the morphology of the invading fluid. This allows to model

Calcium Orthophosphates in Nature, Biology and Medicine

PubMed Central

Dorozhkin, Sergey V.

2009-01-01

The present overview is intended to point the readers’ attention to the important subject of calcium orthophosphates. These materials are of the special significance because they represent the inorganic part of major normal (bones, teeth and dear antlers) and pathological (i.e. those appearing due to various diseases) calcified tissues of mammals. Due to a great chemical similarity with the biological calcified tissues, many calcium orthophosphates possess remarkable biocompatibility and bioactivity. Materials scientists use this property extensively to construct artificial bone grafts that are either entirely made of or only surface-coated with the biologically relevant calcium ortho-phosphates. For example, self-setting hydraulic cements made of calcium orthophosphates are helpful in bone repair, while titanium substitutes covered by a surface layer of calcium orthophosphates are used for hip joint endoprostheses and as tooth substitutes. Porous scaffolds made of calcium orthophosphates are very promising tools for tissue engineering applications. In addition, technical grade calcium orthophosphates are very popular mineral fertilizers. Thus ere calcium orthophosphates are of great significance for humankind and, in this paper, an overview on the current knowledge on this subject is provided.

Surface characterization of colloidal-sol gel derived biphasic HA/FA coatings.

PubMed

Cheng, Kui; Zhang, Sam; Weng, Wenjian

2007-10-01

Hydroxyapatite (HA) powders are ultrasonically dispersed in the precursor of fluoridated hydroxyapatite (FHA) or fluorapatite (FA) to form a "colloidal sol". HA/FA biphasic coatings are prepared on Ti6Al4V substrate via dip coating, 150 degrees C drying and 600 degrees C firing. The coatings show homogenous distribution of HA particles in the FA matrix. The relative phase proportion can be tailored by the amount of HA in the colloidal sol. The surfaces of the coatings consist of two kinds of distinct domains: HA and FA, resulting in a compositionally heterogeneous surface. The biphasic coating surface becomes increasingly rougher with HA powders, from around 200 nm of pure FA to 400-600 nm in Ra of biphasic coatings. The rougher biphasic HA/FA surfaces with chemically controllable domains will favor cell attachment, apatite layer deposition and necessary dissolution in clinical applications.

Calcium supplementation decreases BCP-induced inflammatory processes in blood cells through the NLRP3 inflammasome down-regulation.

PubMed

Lagadec, Patricia; Balaguer, Thierry; Boukhechba, Florian; Michel, Grégory; Bouvet-Gerbettaz, Sébastien; Bouler, Jean-Michel; Scimeca, Jean-Claude; Rochet, Nathalie

2017-07-15

Interaction of host blood with biomaterials is the first event occurring after implantation in a bone defect. This study aimed at investigating the cellular and molecular consequences arising at the interface between whole blood and biphasic calcium phosphate (BCP) particles. We observed that, due to calcium capture, BCP inhibited blood coagulation, and that this inhibition was reversed by calcium supplementation. Therefore, we studied the impact of calcium supplementation on BCP effects on blood cells. Comparative analysis of BCP and calcium supplemented-BCP (BCP/Ca) effects on blood cells showed that BCP as well as BCP/Ca induced monocyte proliferation, as well as a weak but significant hemolysis. Our data showed for the first time that calcium supplementation of BCP microparticles had anti-inflammatory properties compared to BCP alone that induced an inflammatory response in blood cells. Our results strongly suggest that the anti-inflammatory property of calcium supplemented-BCP results from its down-modulating effect on P2X7R gene expression and its capacity to inhibit ATP/P2X7R interactions, decreasing the NLRP3 inflammasome activation. Considering that monocytes have a vast regenerative potential, and since the excessive inflammation often observed after bone substitutes implantation limits their performance, our results might have great implications in terms of understanding the mechanisms leading to an efficient bone reconstruction. Although scaffolds and biomaterials unavoidably come into direct contact with blood during bone defect filling, whole blood-biomaterials interactions have been poorly explored. By studying in 3D the interactions between biphasic calcium phosphate (BCP) in microparticulate form and blood, we showed for the first time that calcium supplementation of BCP microparticles (BCP/Ca) has anti-inflammatory properties compared to BCP-induced inflammation in whole blood cells and provided information related to the molecular mechanisms

Cardioversion Efficacy Using Pulsed Biphasic or Biphasic Truncated Exponential Waveforms: A Randomized Clinical Trial.

PubMed

Schmidt, Anders S; Lauridsen, Kasper G; Adelborg, Kasper; Torp, Peter; Bach, Leif F; Jepsen, Simon M; Hornung, Nete; Deakin, Charles D; Rickers, Hans; Løfgren, Bo

2017-03-08

Several different defibrillators are currently used for cardioversion and defibrillation of cardiac arrhythmias. The efficacy of a novel pulsed biphasic (PB) waveform has not been compared to other biphasic waveforms. Accordingly, this study aims to compare the efficacy and safety of PB shocks with biphasic truncated exponential (BTE) shocks in patients undergoing cardioversion of atrial fibrillation or -flutter. This prospective, randomized study included patients admitted for elective direct current cardioversion. Patients were randomized to receive cardioversion using either PB or BTE shocks. We used escalating shocks until sinus rhythm was obtained or to a maximum of 4 shocks. Patients randomized to PB shocks received 90, 120, 150, and 200 J and patients randomized to BTE shocks received 100, 150, 200, and 250 J, as recommended by the manufacturers. In total, 69 patients (51%) received PB shocks and 65 patients (49%) BTE shocks. Successful cardioversion, defined as sinus rhythm 4 hours after cardioversion, was achieved in 43 patients (62%) using PB shocks and in 56 patients (86%) using BTE shocks; ratio 1.4 (95% CI 1.1-1.7) ( P =0.002). There was no difference in safety (ie, myocardial injury judged by changes in high-sensitive troponin I levels; ratio 1.1) (95% CI 1.0-1.3), P =0.15. The study was terminated prematurely because of an adverse event. Cardioversion using a BTE waveform was more effective when compared with a PB waveform. There was no difference in safety between the 2 waveforms, as judged by changes in troponin I levels. URL: http://www.clinicaltrials.gov. Unique identifier: NCT02317029. © 2017 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley Blackwell.

Poly(trimethylene carbonate)-based composite materials for reconstruction of critical-sized cranial bone defects in sheep.

PubMed

Zeng, Ni; van Leeuwen, Anne C; Grijpma, Dirk W; Bos, Ruud R M; Kuijer, Roel

2017-02-01

The use of ceramic materials in repair of bone defects is limited to non-load-bearing sites. We tested poly(trimethylene carbonate) (PTMC) combined with β-tricalcium phosphate or biphasic calcium phosphate particles for reconstruction of cranial defects. PTMC-calcium phosphate composite matrices were implanted in cranial defects in sheep for 3 and 9 months. Micro-computed tomography quantification and histological observation were performed for analysis. No differences were found in new bone formation among the defects left unfilled, filled with PTMC scaffolds, or filled with either kind of PTMC-calcium phosphate composite scaffolds. Porous β-TCP scaffolds as control led to a larger amount of newly formed bone in the defects than all other materials. Histology revealed abundant new bone formation in the defects filled with porous β-TCP scaffolds. New bone formation was limited in defects filled with PTMC scaffolds or different PTMC-calcium phosphate matrices. PTMC matrices were degraded uneventfully. New bone formation within the defects followed an orderly pattern. PTMC did not interfere with bone regeneration in sheep cranial defects and is suitable as a polymer matrix for incorporating calcium phosphate particles. Increasing the content of calcium phosphate particles in the composite matrices may enhance the beneficial effects of the particles on new bone formation. Copyright © 2016 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.

Porous polymer film calcium ion chemical sensor and method of using the same

DOEpatents

Porter, Marc D.; Chau, Lai-Kwan

1991-02-12

A method of measuring calcium ions is disclosed wherein a calcium sensitive reagent, calcichrome, is immobilized on a porour polymer film. The reaction of the calcium sensitive reagent to the Ca(II) is then measured and concentration determined as a function of the reaction.

Role of biphasic calcium phosphate ceramic-mediated secretion of signaling molecules by macrophages in migration and osteoblastic differentiation of MSCs.

PubMed

Wang, Jing; Liu, Dan; Guo, Bo; Yang, Xiao; Chen, Xuening; Zhu, Xiangdong; Fan, Yujiang; Zhang, Xingdong

2017-03-15

The inflammatory reaction initiates fracture healing and could play a role in the osteoinductive effect of calcium phosphate (CaP) ceramics, which has been widely confirmed; however, the underlying mechanism has not been fully elucidated. In this study, various signaling molecules from macrophages under the stimulation of osteoinductive biphasic calcium phosphate (BCP) ceramic and its degradation products were examined and evaluated for their influence on the migration and osteoblastic differentiation of mesenchymal stem cells (MSCs). The results of cellular experiments confirmed that the gene expression of most inflammatory factors (IL-1, IL-6 and MCP-1) and growth factors (VEGF, PDGF and EGF) by macrophages were up-regulated to varying degrees by BCP ceramic and its degradation products. Cell migration tests demonstrated that the conditioned media (CMs), which contained abundant signaling molecules secreted by macrophages cultured on BCP ceramic and its degradation products, promoted the migration of MSCs. qRT-PCR analysis indicated that CMs promoted the gene expression of osteogenic markers (ALP, COL-I, OSX, BSP and OPN) in MSCs. ALP activity and mineralization staining further confirmed that CMs promoted the osteoblastic differentiation of MSCs. The present study confirmed the correlation between the inflammatory reaction and osteoinductive capacity of BCP ceramic. The ceramic itself and its degradation products can induce macrophages to express and secrete various signaling molecules, which then recruit and promote the MSCs to differentiate into osteoblasts. Compared with BCP conditioned media, degradation particles played a more substantial role in this process. Thus, inflammation initiated by BCP ceramic and its degradation products could be necessary for osteoinduction by the ceramic. It is known that the inflammatory reaction initiates fracture healing. The aim of this study was to examine whether osteoinductive BCP ceramics could cause macrophages to

Intracellular calcium rise is not a necessary step for the stimulated actin polymerization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yassin, R.

1986-03-01

Stimulation of rabbit peritoneal neutrophils by many chemotactic (formyl Methionyl-Leucyl-Phenylalanine (fMLP), Leukotriene B/sub 4/ (LTB/sub 4/)) and non-chemotactic (phorbol 12-myristate, 13-acetate (PMA), platelet activating factor (PAF), and the calcium ionophore A23187) factors produces rapid and dose dependent increases in the amount of actin associated with the cytoskeleton. The stimulated increase in cytoskeletal actin does not appear to require a rise in the intracellular concentration of free calcium. The increase in cytoskeletal actin produced by A23187 is transient and does not depend on the presence of calcium in the suspending medium. In the presence of extracellular calcium, the effect of themore » ionophore is biphasic with respect to concentration. The increases in actin association with cytoskeletal produced by fMLP, LTB/sub 4/, and A23187 but not by PMA, are inhibited by hyperosmolarity and pertussis toxin pretreatment. On the other hand, the addition of hyperosmolarity or pertussis toxin has small effect on the rise in the intracellular calcium produced by A23187. The results presented here suggest that an increase in the intracellular concentration of free calcium is not necessary for the stimulated increases in cytoskeletal actin.« less

Direct stimulation of the transcellular and paracellular calcium transport in the rat cecum by prolactin.

PubMed

Kraidith, Kamonshanok; Jantarajit, Walailuk; Teerapornpuntakit, Jarinthorn; Nakkrasae, La-iad; Krishnamra, Nateetip; Charoenphandhu, Narattaphol

2009-09-01

Prolactin (PRL) is reported to stimulate calcium absorption in the rat's small intestine. However, little is known regarding its effects on the cecum, a part of the large intestine with the highest rate of intestinal calcium transport. We demonstrated herein by quantitative real-time polymerase chain reaction and Western blot analysis that the cecum could be a target organ of PRL since cecal epithelial cells strongly expressed PRL receptors. In Ussing chamber experiments, PRL enhanced the transcellular cecal calcium absorption in a biphasic dose-response manner. PRL also increased the paracellular calcium permeability and passive calcium transport in the cecum, which could be explained by the PRL-induced decrease in transepithelial resistance and increase in cation selectivity of the cecal epithelium. PRL actions in the cecum were abolished by inhibitors of phosphoinositide 3-kinase (PI3K), protein kinase C (PKC), and RhoA-associated coiled-coil forming kinase (ROCK), but not inhibitors of gene transcription and protein biosynthesis. In conclusion, PRL directly enhanced the transcellular and paracellular calcium transport in the rat cecum through the nongenomic signaling pathways involving PI3K, PKC, and ROCK.

The stability mechanisms of an injectable calcium phosphate ceramic suspension

PubMed Central

Fatimi, Ahmed; Tassin, Jean-François; Axelos, Monique A. V.; Weiss, Pierre

2010-01-01

Calcium phosphate ceramics are widely used as bone substitutes in dentistry and orthopedic applications. For minimally invasive surgery an injectable calcium phosphate ceramic suspension (ICPCS) was developed. It consists in a biopolymer (hydroxypropylmethylcellulose: HPMC) as matrix and bioactive calcium phosphate ceramics (biphasic calcium phosphate: BCP) as fillers. The stability of the suspension is essential to this generation of “ready to use” injectable biomaterial. But, during storage, the particles settle down. The engineering sciences have long been interested in models describing the settling (or sedimentation) of particles in viscous fluids. Our work is dedicated to the comprehension of the effect of the formulation on the stability of calcium phosphate suspension before and after steam sterilization. The rheological characterization revealed the macromolecular behavior of the suspending medium. The investigations of settling kinetics showed the influence of the BCP particle size and the HPMC concentration on the settling velocity and sediment compactness before and after sterilization. To decrease the sedimentation process, the granule size has to be smaller and the polymer concentration has to increase. A much lower sedimentation velocity, as compared to Stokes law, is observed and interpreted in terms of interactions between the polymer network in solution and the particles. This experimentation highlights the granules spacer property of hydrophilic macromolecules that is a key issue for interconnection control, one of the better ways to improve osteoconduction and bioactivity. PMID:20229185

The stability mechanisms of an injectable calcium phosphate ceramic suspension.

PubMed

Fatimi, Ahmed; Tassin, Jean-François; Axelos, Monique A V; Weiss, Pierre

2010-06-01

Calcium phosphate ceramics are widely used as bone substitutes in dentistry and orthopedic applications. For minimally invasive surgery an injectable calcium phosphate ceramic suspension (ICPCS) was developed. It consists in a biopolymer (hydroxypropylmethylcellulose: HPMC) as matrix and bioactive calcium phosphate ceramics (biphasic calcium phosphate: BCP) as fillers. The stability of the suspension is essential to this generation of "ready to use" injectable biomaterial. But, during storage, the particles settle down. The engineering sciences have long been interested in models describing the settling (or sedimentation) of particles in viscous fluids. Our work is dedicated to the comprehension of the effect of the formulation on the stability of calcium phosphate suspension before and after steam sterilization. The rheological characterization revealed the macromolecular behavior of the suspending medium. The investigations of settling kinetics showed the influence of the BCP particle size and the HPMC concentration on the settling velocity and sediment compactness before and after sterilization. To decrease the sedimentation process, the granule size has to be smaller and the polymer concentration has to increase. A much lower sedimentation velocity, as compared to Stokes law, is observed and interpreted in terms of interactions between the polymer network in solution and the particles. This experimentation highlights the granules spacer property of hydrophilic macromolecules that is a key issue for interconnection control, one of the better ways to improve osteoconduction and bioactivity.

Metal separations using aqueous biphasic partitioning systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chaiko, D.J.; Zaslavsky, B.; Rollins, A.N.

1996-05-01

Aqueous biphasic extraction (ABE) processes offer the potential for low-cost, highly selective separations. This countercurrent extraction technique involves selective partitioning of either dissolved solutes or ultrafine particulates between two immiscible aqueous phases. The extraction systems that the authors have studied are generated by combining an aqueous salt solution with an aqueous polymer solution. They have examined a wide range of applications for ABE, including the treatment of solid and liquid nuclear wastes, decontamination of soils, and processing of mineral ores. They have also conducted fundamental studies of solution microstructure using small angle neutron scattering (SANS). In this report they reviewmore » the physicochemical fundamentals of aqueous biphase formation and discuss the development and scaleup of ABE processes for environmental remediation.« less

[In vitro drug release behavior of carrier made of porous glass ceramics].

PubMed

Wang, De-ping; Huang, Wen-hai; Zhou, Nai

2002-09-01

To conduct the in vitro test on drug release of rifampin encapsulated in a carrier made of porous phosphate glass ceramics and to analyze main factors which affect the drug release rate. A certain quantitative of rifampin was sealed in a hollow cylindrical capsule which consisted of chopped calcium phosphate crystal fiber obtained from glass crystallization. The rifampin concentration was measured in the simulated physiological solution in which the capsule soaked. Rifampin could be released in a constant rate from the porous glass ceramic carrier in a long time. The release rate was dependent on the size of crystal fiber and the wall thickness of the capsule. This kind of calcium phosphate glass ceramics can be a candidate of the carrier materials used as long term drug therapy after osteotomy surgery.

Evaluation of the finite element software ABAQUS for biomechanical modelling of biphasic tissues.

PubMed

Wu, J Z; Herzog, W; Epstein, M

1998-02-01

The biphasic cartilage model proposed by Mow et al. (1980) has proven successful to capture the essential mechanical features of articular cartilage. In order to analyse the joint contact mechanics in real, anatomical joints, the cartilage model needs to be implemented into a suitable finite element code to approximate the irregular surface geometries of such joints. However, systematic and extensive evaluation of the capacity of commercial software for modelling the contact mechanics with biphasic cartilage layers has not been made. This research was aimed at evaluating the commercial finite element software ABAQUS for analysing biphasic soft tissues. The solutions obtained using ABAQUS were compared with those obtained using other finite element models and analytical solutions for three numerical tests: an unconfined indentation test, a test with the contact of a spherical cartilage surface with a rigid plate, and an axi-symmetric joint contact test. It was concluded that the biphasic cartilage model can be implemented into the commercial finite element software ABAQUS to analyse practical joint contact problems with biphasic articular cartilage layers.

Biphasic Synergistic Gel Materials with Switchable Mechanics and Self-Healing Capacity.

PubMed

Zhao, Ziguang; Liu, Yuxia; Zhang, Kangjun; Zhuo, Shuyun; Fang, Ruochen; Zhang, Jianqi; Jiang, Lei; Liu, Mingjie

2017-10-16

A fabrication strategy for biphasic gels is reported, which incorporates high-internal-phase emulsions. Closely packed micro-inclusions within the elastic hydrogel matrix greatly improve the mechanical properties of the materials. The materials exhibit excellent switchable mechanics and shape-memory performance because of the switchable micro- inclusions that are incorporated into the hydrogel matrix. The produced materials demonstrated a self-healing capacity that originates from the noncovalent effect of the biphasic heteronetwork. The aforementioned characteristics suggest that the biphasic gels may serve as ideal composite gel materials with validity in a variety of applications, such as soft actuators, flexible devices, and biological materials. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Porous Ti-6Al-4V alloy fabricated by spark plasma sintering for biomimetic surface modification.

PubMed

Kon, Masayuki; Hirakata, Luciana M; Asaoka, Kenzo

2004-01-15

Porous compacts with both biological and biomechanical compatibilities and high strength were developed. Spherical powders of Ti-6Al-4V alloy, which were either as received or surface modified with the use of calcium ions by hydrothermal treatment (HTT), were fabricated by a spark plasma sintering process. The porous compacts of pure Ti were used as reference materials. Porosity was approximately 30%, and compressive strengths were 113 and 125 MPa for the as-received Ti alloy powders and those modified by the HTT process, respectively. The bending strength and elastic modulus of as-received Ti alloy powders were 128-178 MPa and 16-18 GPa, respectively. Each of the compacts was immersed in simulated body fluid (SBF). The amount of adsorption/precipitation of calcium phosphate through the compacts was measured by weight change and was observed by SEM. The compacts were covered with calcium phosphate after 2 weeks of immersion in SBF. The compacts of Ti alloy had plenty of precipitated apatite crystals, and modification by HTT accumulated more precipitation. Because calcium phosphate is a mineral component of bone, apatite, which is precipitated on the surface of the compacts, could adsorb proteins and/or drugs such as antibiotics. It is expected that a large amount of proteins and/or drugs could be impregnated when the porous compacts developed are used. Copyright 2003 Wiley Periodicals, Inc.

A Structurally and Functionally Biomimetic Biphasic Scaffold for Intervertebral Disc Tissue Engineering

PubMed Central

Choy, Andrew Tsz Hang; Chan, Barbara Pui

2015-01-01

Tissue engineering offers high hopes for the treatment of intervertebral disc (IVD) degeneration. Whereas scaffolds of the disc nucleus and annulus have been extensively studied, a truly biomimetic and mechanically functional biphasic scaffold using naturally occurring extracellular matrix is yet to be developed. Here, a biphasic scaffold was fabricated with collagen and glycosaminoglycans (GAGs), two of the most abundant extracellular matrix components in the IVD. Following fabrication, the scaffold was characterized and benchmarked against native disc. The biphasic scaffold was composed of a collagen-GAG co-precipitate making up the nucleus pulposus-like core, and this was encapsulated in multiple lamellae of photochemically crosslinked collagen membranes comprising the annulus fibrosus-like lamellae. On mechanical testing, the height of our engineered disc recovered by ~82-89% in an annulus-independent manner, when compared with the 99% recovery exhibited by native disc. The annulus-independent nature of disc height recovery suggests that the fluid replacement function of the engineered nucleus pulposus core might mimic this hitherto unique feature of native disc. Biphasic scaffolds comprised of 10 annulus fibrosus-like lamellae had the best overall mechanical performance among the various designs owing to their similarity to native disc in most aspects, including elastic compliance during creep and recovery, and viscous compliance during recovery. However, the dynamic mechanical performance (including dynamic stiffness and damping factor) of all the biphasic scaffolds was similar to that of the native discs. This study contributes to the rationalized design and development of a biomimetic and mechanically viable biphasic scaffold for IVD tissue engineering. PMID:26115332

Flexible Neural Electrode Array Based-on Porous Graphene for Cortical Microstimulation and Sensing

NASA Astrophysics Data System (ADS)

Lu, Yichen; Lyu, Hongming; Richardson, Andrew G.; Lucas, Timothy H.; Kuzum, Duygu

2016-09-01

Neural sensing and stimulation have been the backbone of neuroscience research, brain-machine interfaces and clinical neuromodulation therapies for decades. To-date, most of the neural stimulation systems have relied on sharp metal microelectrodes with poor electrochemical properties that induce extensive damage to the tissue and significantly degrade the long-term stability of implantable systems. Here, we demonstrate a flexible cortical microelectrode array based on porous graphene, which is capable of efficient electrophysiological sensing and stimulation from the brain surface, without penetrating into the tissue. Porous graphene electrodes show superior impedance and charge injection characteristics making them ideal for high efficiency cortical sensing and stimulation. They exhibit no physical delamination or degradation even after 1 million biphasic stimulation cycles, confirming high endurance. In in vivo experiments with rodents, same array is used to sense brain activity patterns with high spatio-temporal resolution and to control leg muscles with high-precision electrical stimulation from the cortical surface. Flexible porous graphene array offers a minimally invasive but high efficiency neuromodulation scheme with potential applications in cortical mapping, brain-computer interfaces, treatment of neurological disorders, where high resolution and simultaneous recording and stimulation of neural activity are crucial.

A prospective, randomized controlled preclinical trial to evaluate different formulations of biphasic calcium phosphate in combination with a hydroxyapatite collagen membrane to reconstruct deficient alveolar ridges.

PubMed

Nevins, Myron; Nevins, Marc L; Schupbach, Peter; Kim, Soo-Woo; Lin, Zhao; Kim, David M

2013-04-01

Many patients and clinicians would prefer a synthetic particulate bone replacement graft, but most available alloplastic biomaterials have limited osteogenic potential. An alloplast with increased regenerative capacity would be advantageous for the treatment of localized alveolar ridge defects. This prospective, randomized controlled preclinical trial utilized 6 female foxhounds to analyze the osteogenic impact of different formulations of biphasic calcium phosphate (BCP) in combination with an hydroxyapatite-collagen membrane and their ability to reconstruct deficient alveolar ridges for future implant placement. The grafted sites were allowed to heal 3 months, and then trephine biopsies were obtained to perform light microscopic and histomorphometric analyses. All treated sites healed well with no early membrane exposure or adverse soft tissue responses during the healing period. The grafted sites exhibited greater radiopacity than the surrounding native bone with BCP particles seen as radiopaque granules. The graft particles appeared to be well-integrated and no areas of loose particles were observed. Histologic evaluation demonstrated BCP particles embedded in woven bone with dense connective tissue/marrow space. New bone growth was observed around the graft particles as well as within the structure of the graft particulate. There was intimate contact between the graft particles and newly formed bone, and graft particles were bridged by the newly formed bone in all biopsies from the tested groups. The present study results support the potential of these BCP graft particulates to stimulate new bone formation. Clinical studies are recommended to confirm these preclinical findings.

Cytosolic calcium rises and related events in ergosterol-treated Nicotiana cells.

PubMed

Vatsa, Parul; Chiltz, Annick; Luini, Estelle; Vandelle, Elodie; Pugin, Alain; Roblin, Gabriel

2011-07-01

The typical fungal membrane component ergosterol was previously shown to trigger defence responses and protect plants against pathogens. Most of the elicitors mobilize the second messenger calcium, to trigger plant defences. We checked the involvement of calcium in response to ergosterol using Nicotiana plumbaginifolia and Nicotiana tabacum cv Xanthi cells expressing apoaequorin in the cytosol. First, it was verified if ergosterol was efficient in these cells inducing modifications of proton fluxes and increased expression of defence-related genes. Then, it was shown that ergosterol induced a rapid and transient biphasic increase of free [Ca²⁺](cyt) which intensity depends on ergosterol concentration in the range 0.002-10 μM. Among sterols, this calcium mobilization was specific for ergosterol and, ergosterol-induced pH and [Ca²⁺](cyt) changes were specifically desensitized after two subsequent applications of ergosterol. Specific modulators allowed elucidating some events in the signalling pathway triggered by ergosterol. The action of BAPTA, LaCl₃, nifedipine, verapamil, neomycin, U73122 and ruthenium red suggested that the first phase was linked to calcium influx from external medium which subsequently triggered the second phase linked to calcium release from internal stores. The calcium influx and the [Ca²⁺](cyt) increase depended on upstream protein phosphorylation. The extracellular alkalinization and ROS production depended on calcium influx but, the ergosterol-induced MAPK activation was calcium-independent. ROS were not involved in cytosolic calcium rise as described in other models, indicating that ROS do not systematically participate in the amplification of calcium signalling. Interestingly, ergosterol-induced ROS production is not linked to cell death and ergosterol does not induce any calcium elevation in the nucleus. Copyright © 2011 Elsevier Masson SAS. All rights reserved.

Electron transport in zinc-blende wurtzite biphasic gallium nitride nanowires and GaNFETs

DOE PAGES

Jacobs, Benjamin W.; Ayres, Virginia M.; Stallcup, Richard E.; ...

2007-10-19

Two-point and four-point probe electrical measurements of a biphasic gallium nitride nanowire and current–voltage characteristics of a gallium nitride nanowire based field effect transistor are reported. The biphasic gallium nitride nanowires have a crystalline homostructure consisting of wurtzite and zinc-blende phases that grow simultaneously in the longitudinal direction. There is a sharp transition of one to a few atomic layers between each phase. Here, all measurements showed high current densities. Evidence of single-phase current transport in the biphasic nanowire structure is discussed.

A re-examination of the biphasic theory of skeletal muscle growth.

PubMed Central

Levine, A S; Hegarty, P V

1977-01-01

Because of the importance of fibre diameter measurements it was decided to re-evaluate the biphasic theory of skeletal muscle growth and development. This theory proposes an initial memophasic distribution of muscle fibres which changes to a biphasic distribution during development. The theory is based on observations made on certain muscles in mice, where two distinct populations of fibre diameters (20 and 40 micronm) contribute to the biphasic distribution. In the present investigation corss sections of frozen biceps brachii of mice in rigor mortis were examined. The rigor state was used to avoid complications produced by thaw-rigor contraction. The diameters of the outermost and innermost fibres were found to be significantly different. However, if the outer and inner fibres were combined to form one group, no significant difference between this group and other random groups was found. The distributions of all groups were monophasic. The diameters of isolated fibres from mice and rats also displayed a monophasic distribution. This evidence leads to the conclusion that the biphasic theory of muscle growth is untenable. Some of the variables which may occur in fibre size and shape are discussed. Images Fig. 1 PMID:858691

Ceramic modifications of porous titanium: effects on macrophage activation.

PubMed

Scislowska-Czarnecka, A; Menaszek, E; Szaraniec, B; Kolaczkowska, E

2012-12-01

Porous titanium is one of the most widely used implant materials because of its mechanical properties, however, it is also characterised by low bioactivity. To improve the above parameter we prepared three modifications of the porous (30 wt%) titanium (Ti) surface by covering it with bioactive hydroxyapatite (HA), bioglass (BG) and calcium silicate (CS). Subsequently we tested the impact of the modifications on macrophages directing the inflammatory response that might compromise the implant bioactivity. In the study we investigated the in vitro effects of the materials on murine cell line RAW 264.7 macrophage adherence, morphology and activation (production/release of metalloproteinase MMP-9 and pro- and anti-inflammatory cytokines). CS Ti decreased the macrophage adherence and up-regulated the release of several pro-inflammatory mediators, including TNF-α, IL-6, IL-12. Also HA Ti reduced the cell adherence but other parameters were generally not increased, except of TNF-α. In contrast, BG Ti improved macrophage adherence and either decreased production of multiple mediators (MMP-9, TNF-α, IFN-γ, MCP-1) or did not change it in comparison to the porous titanium. We can conclude that analyzing the effects on the inflammatory response initiated by macrophages in vitro, calcium silicate did not improve the biological properties of the porous titanium. The improved bioactivity of titanium was, however, achieved by the application of the hydroxyapatite and bioglass layers. The present in vitro results suggest that these materials, HA Ti and especially BG Ti, may be suitable for in vivo application and thus justify their further investigation. Copyright © 2012 Elsevier Ltd. All rights reserved.

Experimental investigation of the displacement dynamics during biphasic flow in porous media

NASA Astrophysics Data System (ADS)

Ayaz, Monem; Toussaint, Renaud; Måløy, Knut-Jørgen; Schafer, Gerhard

2016-04-01

We experimentally study the interface dynamics of an immiscible fluid as it displaces a fully saturated porous medium. The system is confined by a vertically oriented Hele-Shaw cell, with piezoelectric type acoustic sensors mounted along the centerline. During drainage potential surface energy is stored at the interface up to a given threshold in pressure, at which an instability occurs as new pores are invaded and the radius of curvature of the interface increases locally, the energy gets released, and part of this energy is detectable as acoustic emission. By detecting pore-scale events emanating from the interface at various points, we look to develop techniques for localizing the displacement front. To assess the quality, optical monitoring is done using a high speed camera.In our study we also aim to gain further insight into the interface dynamics by varying parameters such as the effective gravity, and the invasion speed and using other methods of probing the system such as active tomography. We here present our preliminary results of this study.

Biphasic Dose Response in Low Level Light Therapy – An Update

PubMed Central

Huang, Ying-Ying; Sharma, Sulbha K; Carroll, James; Hamblin, Michael R

2011-01-01

Low-level laser (light) therapy (LLLT) has been known since 1967 but still remains controversial due to incomplete understanding of the basic mechanisms and the selection of inappropriate dosimetric parameters that led to negative studies. The biphasic dose-response or Arndt-Schulz curve in LLLT has been shown both in vitro studies and in animal experiments. This review will provide an update to our previous (Huang et al. 2009) coverage of this topic. In vitro mediators of LLLT such as adenosine triphosphate (ATP) and mitochondrial membrane potential show biphasic patterns, while others such as mitochondrial reactive oxygen species show a triphasic dose-response with two distinct peaks. The Janus nature of reactive oxygen species (ROS) that may act as a beneficial signaling molecule at low concentrations and a harmful cytotoxic agent at high concentrations, may partly explain the observed responses in vivo. Transcranial LLLT for traumatic brain injury (TBI) in mice shows a distinct biphasic pattern with peaks in beneficial neurological effects observed when the number of treatments is varied, and when the energy density of an individual treatment is varied. Further understanding of the extent to which biphasic dose responses apply in LLLT will be necessary to optimize clinical treatments. PMID:22461763

Influence of substrate mineralogy on bacterial mineralization of calcium carbonate: implications for stone conservation.

PubMed

Rodriguez-Navarro, Carlos; Jroundi, Fadwa; Schiro, Mara; Ruiz-Agudo, Encarnación; González-Muñoz, María Teresa

2012-06-01

The influence of mineral substrate composition and structure on bacterial calcium carbonate productivity and polymorph selection was studied. Bacterial calcium carbonate precipitation occurred on calcitic (Iceland spar single crystals, marble, and porous limestone) and silicate (glass coverslips, porous sintered glass, and quartz sandstone) substrates following culturing in liquid medium (M-3P) inoculated with different types of bacteria (Myxococcus xanthus, Brevundimonas diminuta, and a carbonatogenic bacterial community isolated from porous calcarenite stone in a historical building) and direct application of sterile M-3P medium to limestone and sandstone with their own bacterial communities. Field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), powder X-ray diffraction (XRD), and 2-dimensional XRD (2D-XRD) analyses revealed that abundant highly oriented calcite crystals formed homoepitaxially on the calcitic substrates, irrespective of the bacterial type. Conversely, scattered spheroidal vaterite entombing bacterial cells formed on the silicate substrates. These results show that carbonate phase selection is not strain specific and that under equal culture conditions, the substrate type is the overruling factor for calcium carbonate polymorph selection. Furthermore, carbonate productivity is strongly dependent on the mineralogy of the substrate. Calcitic substrates offer a higher affinity for bacterial attachment than silicate substrates, thereby fostering bacterial growth and metabolic activity, resulting in higher production of calcium carbonate cement. Bacterial calcite grows coherently over the calcitic substrate and is therefore more chemically and mechanically stable than metastable vaterite, which formed incoherently on the silicate substrates. The implications of these results for technological applications of bacterial carbonatogenesis, including building stone conservation, are discussed.

Influence of Substrate Mineralogy on Bacterial Mineralization of Calcium Carbonate: Implications for Stone Conservation

PubMed Central

Jroundi, Fadwa; Schiro, Mara; Ruiz-Agudo, Encarnación; González-Muñoz, María Teresa

2012-01-01

The influence of mineral substrate composition and structure on bacterial calcium carbonate productivity and polymorph selection was studied. Bacterial calcium carbonate precipitation occurred on calcitic (Iceland spar single crystals, marble, and porous limestone) and silicate (glass coverslips, porous sintered glass, and quartz sandstone) substrates following culturing in liquid medium (M-3P) inoculated with different types of bacteria (Myxococcus xanthus, Brevundimonas diminuta, and a carbonatogenic bacterial community isolated from porous calcarenite stone in a historical building) and direct application of sterile M-3P medium to limestone and sandstone with their own bacterial communities. Field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), powder X-ray diffraction (XRD), and 2-dimensional XRD (2D-XRD) analyses revealed that abundant highly oriented calcite crystals formed homoepitaxially on the calcitic substrates, irrespective of the bacterial type. Conversely, scattered spheroidal vaterite entombing bacterial cells formed on the silicate substrates. These results show that carbonate phase selection is not strain specific and that under equal culture conditions, the substrate type is the overruling factor for calcium carbonate polymorph selection. Furthermore, carbonate productivity is strongly dependent on the mineralogy of the substrate. Calcitic substrates offer a higher affinity for bacterial attachment than silicate substrates, thereby fostering bacterial growth and metabolic activity, resulting in higher production of calcium carbonate cement. Bacterial calcite grows coherently over the calcitic substrate and is therefore more chemically and mechanically stable than metastable vaterite, which formed incoherently on the silicate substrates. The implications of these results for technological applications of bacterial carbonatogenesis, including building stone conservation, are discussed. PMID:22447589

Chemical transformation of some biologically relevant calcium phosphates in aqueous media during a steam sterilization.

PubMed

Dorozhkin, S V; Schmitt, M; Bouler, J M; Daculsi, G

2000-12-01

The purpose of this study was to investigate the effect of steam sterilization on some biologically relevant calcium phosphates: CaHPO4 . 2H2O (DCPD), calcium deficient apatite (CDA) and biphasic calcium phosphate (BCP). Suspensions of 0.2 g of each calcium phosphate compound with 5.0 ml of deionized water were prepared and steam sterilized in an autoclave (20 min at 121 degrees C). After sterilization the suspensions were filtered and the dried solids characterized with scanning electron microscopy, IR-spectroscopy and X-ray diffraction. The pH and calcium concentrations of the filtrates were determined with ion selective electrodes. Similar measurements were made with the same samples which were not sterilized. The sterilization procedure was found to result in the dehydration of DCPD and hydration of calcium oxide incorporated into the BCP. Solution pH was observed to change from 7.3 to 5.5 for the solutions in equilibrium with DCPD and from 8.5 to 10.6 for those in equilibrium with BCP. Minor changes both with the solid and liquid phases were found to occur during the steam sterilization of CDA. These results indicate that steam sterilization may have different effects on different calcium phosphate suspensions: it can result in dehydration of DCPD, fast hydration for CaO in BCP, but no significant effect on CDA. Copyright 2000 Kluwer Academic Publishers

Hydrothermal synthesis of porous triphasic hydroxyapatite/(alpha and beta) tricalcium phosphate.

PubMed

Vani, R; Girija, E K; Elayaraja, K; Prakash Parthiban, S; Kesavamoorthy, R; Narayana Kalkura, S

2009-12-01

A novel, porous triphasic calcium phosphate composed of nonresorbable hydroxyapatite (HAp) and resorbable tricalcium phosphate (alpha- and beta-TCP) has been synthesized hydrothermally at a relatively low temperature. The calcium phosphate precursor for hydrothermal treatment was prepared by gel method in the presence of ascorbic acid. XRD, FT-IR, Raman analyses confirmed the presence of HAp/TCP. The surface area and average pore size of the samples were found to be 28 m2/g and 20 nm, respectively. The samples were found to be bioactive in simulated body fluid (SBF).

Inhibition of Sphingosine Kinase 1 Ameliorates Angiotensin II-Induced Hypertension and Inhibits Transmembrane Calcium Entry via Store-Operated Calcium Channel

PubMed Central

Wilson, Parker C.; Fitzgibbon, Wayne R.; Garrett, Sara M.; Jaffa, Ayad A.; Luttrell, Louis M.; Brands, Michael W.

2015-01-01

Angiotensin II (AngII) plays a critical role in the regulation of vascular tone and blood pressure mainly via regulation of Ca2+ mobilization. Several reports have implicated sphingosine kinase 1 (SK1)/sphingosine 1-phosphate (S1P) in the mobilization of intracellular Ca2+ through a yet-undefined mechanism. Here we demonstrate that AngII-induces biphasic calcium entry in vascular smooth muscle cells, consisting of an immediate peak due to inositol tris-phosphate-dependent release of intracellular calcium, followed by a sustained transmembrane Ca2+ influx through store-operated calcium channels (SOCs). Inhibition of SK1 attenuates the second phase of transmembrane Ca2+ influx, suggesting a role for SK1 in AngII-dependent activation of SOC. Intracellular S1P triggers SOC-dependent Ca2+ influx independent of S1P receptors, whereas external application of S1P stimulated S1P receptor-dependent Ca2+ influx that is insensitive to inhibitors of SOCs, suggesting that the SK1/S1P axis regulates store-operated calcium entry via intracellular rather than extracellular actions. Genetic deletion of SK1 significantly inhibits both the acute hypertensive response to AngII in anaesthetized SK1 knockout mice and the sustained hypertensive response to continuous infusion of AngII in conscious animals. Collectively these data implicate SK1 as the missing link that connects the angiotensin AT1A receptor to transmembrane Ca2+ influx and identify SOCs as a potential intracellular target for SK1. PMID:25871850

Calcium Domains around Single and Clustered IP3 Receptors and Their Modulation by Buffers

PubMed Central

Rüdiger, S.; Nagaiah, Ch.; Warnecke, G.; Shuai, J.W.

2010-01-01

Abstract We study Ca2+ release through single and clustered IP3 receptor channels on the ER membrane under presence of buffer proteins. Our computational scheme couples reaction-diffusion equations and a Markovian channel model and allows our investigating the effects of buffer proteins on local calcium concentrations and channel gating. We find transient and stationary elevations of calcium concentrations around active channels and show how they determine release amplitude. Transient calcium domains occur after closing of isolated channels and constitute an important part of the channel's feedback. They cause repeated openings (bursts) and mediate increased release due to Ca2+ buffering by immobile proteins. Stationary domains occur during prolonged activity of clustered channels, where the spatial proximity of IP3Rs produces a distinct [Ca2+] scale (0.5–10 μM), which is smaller than channel pore concentrations (>100 μM) but larger than transient levels. While immobile buffer affects transient levels only, mobile buffers in general reduce both transient and stationary domains, giving rise to Ca2+ evacuation and biphasic modulation of release amplitude. Our findings explain recent experiments in oocytes and provide a general framework for the understanding of calcium signals. PMID:20655827

Macroporous Calcium Phosphate/Chitosan Composites Prepared via Unidirectional Ice Segregation and Subsequent Freeze-Drying

PubMed Central

Aranaz, Inmaculada; Martínez-Campos, Enrique; Moreno-Vicente, Carolina; Civantos, Ana; García-Arguelles, Sara; del Monte, Francisco

2017-01-01

Calcium phosphate chitosan-based composites have gained much interest in recent years for biomedical purposes. In this paper, three-dimensional calcium phosphate chitosan-based composites with different mineral contents were produced using a green method called ice segregation induced self-assembly (ISISA). In this methodology, ice crystals were used as a template to produce porous structures from an aqueous solution of chitosan (CS) and hydroxyapatite (Hap) also containing acetic acid (pH = 4.5). For better characterization of the nature of the inorganic matter entrapped within the resulting composite, we performed either oxygen plasma or calcination processes to remove the organic matter. The nature of the phosphate salts was studied by XRD and NMR studies. Amorphous calcium phosphate (ACP) was identified as the mineral phase in the composites submitted to oxygen plasma, whereas crystalline Hap was obtained after calcination. SEM microscopy revealed the formation of porous structures (porosity around 80–85%) in the original composites, as well as in the inorganic matrices obtained after calcination, with porous channels of up to 50 µm in diameter in the former case and of up to 20 µm in the latter. The biocompatibility of the composites was assessed using two different cell lines: C2C12GFP premyoblastic cells and MC3T3 preosteoblastic cells. PMID:28772874

Continuous Flow Science in an Undergraduate Teaching Laboratory: Bleach-Mediated Oxidation in a Biphasic System

ERIC Educational Resources Information Center

Kairouz, Vanessa; Collins, Shawn K.

2018-01-01

An undergraduate teaching laboratory experiment involving a continuous flow, bleach-mediated oxidation of aldehydes under biphasic conditions was developed that allowed students to explore concepts of mixing or mass transport, solvent sustainability, biphasic reactions, phase transfer catalysis, and continuous flow chemistry.

TSDC and impedance spectroscopy measurements on hydroxyapatite, β-tricalcium phosphate and hydroxyapatite/β-tricalcium phosphate biphasic bioceramics

NASA Astrophysics Data System (ADS)

Prezas, P. R.; Melo, B. M. G.; Costa, L. C.; Valente, M. A.; Lança, M. C.; Ventura, J. M. G.; Pinto, L. F. V.; Graça, M. P. F.

2017-12-01

Bone grafting and surgical interventions related with orthopaedic disorders consist in a big business, generating large revenues worldwide every year. There is a need to replace the biomaterials that currently still dominate this market, i.e., autografts and allografts, due to their disadvantages, such as limited availability, need for additional surgeries and diseases transmission possibilities. The most promising replacement materials are biomaterials with bioactive properties, such as the calcium phosphate-based bioceramics group. The bioactivity of these materials, i.e., the rate at which they promote the growth and directly bond with the new host biological bone, can be enhanced through their electrical polarization. In the present work, the electrical polarization features of pure hydroxyapatite (Hap), pure β-tricalcium phosphate (β-TCP) and biphasic hydroxyapatite/β-tricalcium phosphate composites (HTCP) were analyzed by measuring thermally stimulated depolarization currents (TSDC). The samples were thermoelectrically polarized at 500 °C under a DC electric field with a magnitude of 5 kV/cm. The biphasic samples were also polarized under electric fields with different magnitudes: 2, 3, 4 and 5 kV/cm. Additionally, the depolarization processes detected in the TSDC measurements were correlated with dielectric relaxation processes observed in impedance spectroscopy (IS) measurements. The results indicate that the β-TCP crystalline phase has a considerable higher ability to store electrical charge compared with the Hap phase. This indicates that it has a suitable composition and structure for ionic conduction and establishment of a large electric charge density, providing great potential for orthopaedic applications.

Calcium Orthophosphate-Based Bioceramics

PubMed Central

Dorozhkin, Sergey V.

2013-01-01

Various types of grafts have been traditionally used to restore damaged bones. In the late 1960s, a strong interest was raised in studying ceramics as potential bone grafts due to their biomechanical properties. A bit later, such synthetic biomaterials were called bioceramics. In principle, bioceramics can be prepared from diverse materials but this review is limited to calcium orthophosphate-based formulations only, which possess the specific advantages due to the chemical similarity to mammalian bones and teeth. During the past 40 years, there have been a number of important achievements in this field. Namely, after the initial development of bioceramics that was just tolerated in the physiological environment, an emphasis was shifted towards the formulations able to form direct chemical bonds with the adjacent bones. Afterwards, by the structural and compositional controls, it became possible to choose whether the calcium orthophosphate-based implants remain biologically stable once incorporated into the skeletal structure or whether they were resorbed over time. At the turn of the millennium, a new concept of regenerative bioceramics was developed and such formulations became an integrated part of the tissue engineering approach. Now calcium orthophosphate scaffolds are designed to induce bone formation and vascularization. These scaffolds are often porous and harbor different biomolecules and/or cells. Therefore, current biomedical applications of calcium orthophosphate bioceramics include bone augmentations, artificial bone grafts, maxillofacial reconstruction, spinal fusion, periodontal disease repairs and bone fillers after tumor surgery. Perspective future applications comprise drug delivery and tissue engineering purposes because calcium orthophosphates appear to be promising carriers of growth factors, bioactive peptides and various types of cells. PMID:28788309

Method of coating a substrate with a calcium phosphate compound

DOEpatents

Gao, Yufei; Campbell, Allison A.

2000-01-01

The present invention is a method of coating a substrate with a calcium phosphate compound using plasma enhanced MOCVD. The substrate is a solid material that may be porous or non-porous, including but not limited to metal, ceramic, glass and combinations thereof. The coated substrate is preferably used as an implant, including but not limited to orthopaedic, dental and combinations thereof. Calcium phosphate compound includes but is not limited to tricalcium phosphate (TCP), hydroxyapatite (HA) and combinations thereof. TCP is preferred on a titanium implant when implant resorbability is desired. HA is preferred when the bone bonding of new bone tissue into the structure of the implant is desired. Either or both of TCP and/or HA coated implants may be placed into a solution with an agent selected from the group of protein, antibiotic, antimicrobial, growth factor and combinations thereof that can be adsorbed into the coating before implantation. Once implanted, the release of TCP will also release the agent to improve growth of new bone tissues and/or to prevent infection.

The added predictive value of biphasic events in ST analysis of the fetal electrocardiogram for intrapartum fetal monitoring.

PubMed

Becker, Jeroen H; Krikhaar, Anniek; Schuit, Ewoud; Mårtendal, Annika; Maršál, Karel; Kwee, Anneke; Visser, Gerard H A; Amer-Wåhlin, Isis

2015-02-01

To study the predictive value of biphasic ST-events for interventions for suspected fetal distress and adverse neonatal outcome, when using ST-analysis of the fetal electrocardiogram (FECG) for intrapartum fetal monitoring. Prospective cohort study. Three academic hospitals in Sweden. Women in labor with a high-risk singleton fetus in cephalic position beyond 36 weeks of gestation. In women in labor who were monitored with conventional cardiotocography, ST-waveform analysis was recorded and concealed. Traces with biphasic ST-events of the FECG (index) were compared with traces without biphasic events of the FECG. The ability of biphasic events to predict interventions for suspected fetal distress and adverse outcome was assessed using univariable and multivariable logistic regression analyses. Interventions for suspected fetal distress and adverse outcome (defined as presence of metabolic acidosis (i.e. umbilical cord pH <7.05 and base deficit in extracellular fluid >12 mmol), umbilical cord pH <7.00, 5-min Apgar score <7, admittance to neonatal intensive care unit or perinatal death). Although the presence of biphasic events of the FECG was associated with more interventions for fetal distress and an increased risk of adverse outcome compared with cases with no biphasic events, the presence of significant (i.e. intervention advised according to cardiotocography interpretation) biphasic events showed no independent association with interventions for fetal distress [odds ratio (OR) 1.71, 95% confidence interval (CI) 0.65-4.50] or adverse outcome (OR 1.96, 95% CI 0.74-5.24). The presence of significant biphasic events did not discriminate in the prediction of interventions for fetal distress or adverse outcome. Therefore, biphasic events in relation to ST-analysis monitoring during birth should be omitted if future studies confirm our findings. © 2014 Nordic Federation of Societies of Obstetrics and Gynecology.

A prospective 1-year clinical and radiographic study of implants placed after maxillary sinus floor augmentation with synthetic biphasic calcium phosphate or deproteinized bovine bone.

PubMed

Lindgren, Christer; Mordenfeld, Arne; Hallman, Mats

2012-03-01

The technique of using bone grafts or different biomaterials for augmentation of the maxillary sinus prior to implant placement is well accepted by clinicians. However, clinical documentation of some bone substitutes is still lacking. This prospective study was designed to evaluate the success rate of implants placed after maxillary sinus augmentation with a novel synthetic biphasic calcium phosphate (BCP) or deproteinized bovine bone (DBB), the latter acting as control. Nine edentulous patients and two partially edentulous patients with a mean age of 67 years with a bilateral need for sinus augmentation, < 5 mm residual bone in the floor of the sinus and a crestal width ≥ 4 mm, were included in the study. After bilateral elevation of the Schneiderian membrane, all patients were randomized for augmentation with synthetic BCP in one side and DBB in the contralateral side. After 8 months of graft healing, 62 implants with an SLActive surface were placed. Implant survival, graft resorption, plaque index, bleeding on probing, sulcus bleeding index, probing pocket depth, and implant success rate were evaluated after 1 year of functional loading. After a mean of 118 days, all patients received their fixed prosthetic constructions. One implant was lost in each biomaterial, giving an overall survival rate of 96.8%. Success rates for implants placed in BCP and DBB were 91.7 and 95.7%, respectively. No significant difference in marginal bone loss was found around implants placed in BCP, DBB, or residual bone, respectively. The mean graft resorption was 0.43 mm (BCP) and 0.29 mm (DBB). In this limited study, implant success rate was not dependent on the biomaterial used for maxillary sinus augmentation. Similar results were found after 1 year of functional loading for implants placed after sinus augmentation using BCP or DBB. © 2010 Wiley Periodicals, Inc.

Dissolved nutrients and atrazine removal by column-scale monophasic and biphasic rain garden model systems.

PubMed

Yang, Hanbae; McCoy, Edward L; Grewal, Parwinder S; Dick, Warren A

2010-08-01

Rain gardens are bioretention systems that have the potential to reduce peak runoff flow and improve water quality in a natural and aesthetically pleasing manner. We compared hydraulic performance and removal efficiencies of nutrients and atrazine in a monophasic rain garden design versus a biphasic design at a column-scale using simulated runoff. The biphasic rain garden was designed to increase retention time and removal efficiency of runoff pollutants by creating a sequence of water saturated to unsaturated conditions. We also evaluated the effect of C substrate availability on pollutant removal efficiency in the biphasic rain garden. Five simulated runoff events with various concentrations of runoff pollutants (i.e. nitrate, phosphate, and atrazine) were applied to the monophasic and biphasic rain gardens once every 5d. Hydraulic performance was consistent over the five simulated runoff events. Peak flow was reduced by approximately 56% for the monophasic design and 80% for the biphasic design. Both rain garden systems showed excellent removal efficiency of phosphate (89-100%) and atrazine (84-100%). However, significantly (p<0.001) higher removal of nitrate was observed in the biphasic (42-63%) compared to the monophasic rain garden (29-39%). Addition of C substrate in the form of glucose increased removal efficiency of nitrate significantly (p<0.001), achieving up to 87% removal at a treatment C/N ratio of 2.0. This study demonstrates the importance of retention time, environmental conditions (i.e. saturated/unsaturated conditions), and availability of C substrate for bioremediation of pollutants, especially nitrates, in rain gardens. (c) 2010 Elsevier Ltd. All rights reserved.

Operation and Performance of a Biphase Turbine Power Plant at the Cerro Prieto Geothermal Field (Final Report)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hays, Lance G.

2000-09-01

A full scale, wellhead Biphase turbine was manufactured and installed with the balance of plant at Well 103 of the Cerro Prieto geothermal resource in Baja, California. The Biphase turbine was first synchronized with the electrical grid of Comision Federal de Electricidad on August 20, 1997. The Biphase power plant was operated from that time until May 23, 2000, a period of 2 years and 9 months. A total of 77,549 kWh were delivered to the grid. The power plant was subsequently placed in a standby condition pending replacement of the rotor with a newly designed, higher power rotor andmore » replacement of the bearings and seals. The maximum measured power output of the Biphase turbine, 808 kWe at 640 psig wellhead pressure, agreed closely with the predicted output, 840 kWe. When combined with the backpressure steam turbine the total output power from that flow would be increased by 40% above the power derived only from the flow by the present flash steam plant. The design relations used to predict performance and design the turbine were verified by these tests. The performance and durability of the Biphase turbine support the conclusion of the Economics and Application Report previously published, (Appendix A). The newly designed rotor (the Dual Pressure Rotor) was analyzed for the above power condition. The Dual Pressure Rotor would increase the power output to 2064 kWe by incorporating two pressure letdown stages in the Biphase rotor, eliminating the requirement for a backpressure steam turbine. The power plant availability was low due to deposition of solids from the well on the Biphase rotor and balance of plant problems. A great deal of plant down time resulted from the requirement to develop methods to handle the solids and from testing the apparatus in the Biphase turbine. Finally an online, washing method using the high pressure two-phase flow was developed which completely eliminated the solids problem. The availability of the Biphase turbine itself was

Critical review: Injectability of calcium phosphate pastes and cements.

PubMed

O'Neill, R; McCarthy, H O; Montufar, E B; Ginebra, M-P; Wilson, D I; Lennon, A; Dunne, N

2017-03-01

Calcium phosphate cements (CPC) have seen clinical success in many dental and orthopaedic applications in recent years. The properties of CPC essential for clinical success are reviewed in this article, which includes properties of the set cement (e.g. bioresorbability, biocompatibility, porosity and mechanical properties) and unset cement (e.g. setting time, cohesion, flow properties and ease of delivery to the surgical site). Emphasis is on the delivery of calcium phosphate (CaP) pastes and CPC, in particular the occurrence of separation of the liquid and solid components of the pastes and cements during injection; and established methods to reduce this phase separation. In addition a review of phase separation mechanisms observed during the extrusion of other biphasic paste systems and the theoretical models used to describe these mechanisms are discussed. Occurrence of phase separation of calcium phosphate pastes and cements during injection limits their full exploitation as a bone substitute in minimally invasive surgical applications. Due to lack of theoretical understanding of the phase separation mechanism(s), optimisation of an injectable CPC that satisfies clinical requirements has proven difficult. However, phase separation of pastes during delivery has been the focus across several research fields. Therefore in addition to a review of methods to reduce phase separation of CPC and the associated constraints, a review of phase separation mechanisms observed during extrusion of other pastes and the theoretical models used to describe these mechanisms is presented. It is anticipated this review will benefit future attempts to develop injectable calcium phosphate based systems. Crown Copyright © 2016. Published by Elsevier Ltd. All rights reserved.

Layer-by-Layer Assembled Nanotubes as Biomimetic Nanoreactors for Calcium Carbonate Deposition.

PubMed

He, Qiang; Möhwald, Helmuth; Li, Junbai

2009-09-17

Enzyme-loaded magnetic polyelectrolyte multilayer nanotubes prepared by layer-by-layer assembly combined with the porous template could be used as biomimetic nanoreactors. It is demonstrated that calcium carbonate can be biomimetically synthesized inside the cavities of the polyelectrolyte nanotubes by the catalysis of urease, and the size of the calcium carbonate precipitates was controlled by the cavity dimensions. The metastable structure of the calcium carbonate precipitates inside the nanotubes was protected by the outer shell of the polyelectrolyte multilayers. These features may allow polyelectrolyte nanotubes to be applied in the fields of nanomaterials synthesis, controlled release, and drug delivery. Copyright © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Biphasic non-adrenergic, non-cholinergic relaxations of the mouse anococcygeus muscle.

PubMed Central

Gibson, A.; Yu, O.

1983-01-01

Trains of field stimulation of 60 s duration caused a biphasic relaxation of carbachol (50 microM)-induced tone in the mouse anococcygeus. The optimal pulse frequency and width were 10 Hz and 1 ms respectively. Tetrodotoxin (31, 124, and 310 nM) caused a dose-dependent reduction in the magnitude of both phases. Neither phase was affected by (+/-)-propranolol (1 microM), neostigmine (1 microM), (+)-tubocurarine (100 microM), or apamin (500 nM). Biphasic relaxations were observed in muscles from 6-hydroxydopamine pretreated mice. Haemolysed blood (10, 40, and 100 microliter/ml) reduced the magnitude of the first phase of nerve-induced relaxation to a greater extent than the second. This effect was reversible. Following a prolonged train of inhibitory nerve stimulation (10 Hz; 10 min) the magnitude of the first phase was reduced only slightly, but the second markedly. The possible relationships between the biphasic relaxation to field stimulation and putative non-adrenergic, non-cholinergic transmitters in the mouse anococcygeus are discussed. PMID:6652345

Evaluation of a biphasic in vitro dissolution test for estimating the bioavailability of carbamazepine polymorphic forms.

PubMed

Deng, Jia; Staufenbiel, Sven; Bodmeier, Roland

2017-07-15

The purpose of this study was to discriminate three crystal forms of carbamazepine (a BCS II drug) by in vitro dissolution testing and to correlate in vitro data with published in vivo data. A biphasic dissolution system (phosphate buffer pH6.8 and octanol) was used to evaluate the dissolution of the three polymorphic forms and to compare it with conventional single phase dissolution tests performed under sink and non-sink conditions. Similar dissolution profiles of three polymorphic forms were observed in the conventional dissolution test under sink conditions. Although a difference in dissolution was seen in the single phase dissolution test under non-sink conditions as well as in the aqueous phase of the biphasic test, little relevance for in vivo data was observed. In contrast, the biphasic dissolution system could discriminate between the different polymorphic forms in the octanol phase with a ranking of form III>form I>dihydrate form. This was in agreement with the in vivo performance. The dissolved drug available for oral absorption, which was dominated by dissolution and solution-mediated phase transformation, could be reflected in the biphasic dissolution test. Moreover, a good correlation was established between in vitro dissolution in the octanol phase of the biphasic test and in vivo pharmacokinetic data (R 2 =0.99). The biphasic dissolution method is a valuable tool to discriminate between different crystal forms in the formulations of poorly soluble drugs. Copyright © 2017. Published by Elsevier B.V.

Osteal integration of porous implants from titanium nickelide.

PubMed

Kelmakov, V P; Itin, V I; Epifancev, A G; Lepakova, O K; Kitler, V D; Bulgakov, V N

2009-10-01

The microstructure of preparations from porous titanium nickelide was studied 4.5 months and 1.5 years after operations on the anterior compartments of the spine. Organic tissues of different morphology, compactness, and thickness occupied 100% of analyzed surface 1.5 years after implantation, while after 4.5 months the pores were filled by 60%. The content of calcium and phosphorus elements in surface pores after 1.5 years was close to their concentrations in human bones.

Shock-induced termination of reentrant cardiac arrhythmias: Comparing monophasic and biphasic shock protocols

NASA Astrophysics Data System (ADS)

Bragard, Jean; Simic, Ana; Elorza, Jorge; Grigoriev, Roman O.; Cherry, Elizabeth M.; Gilmour, Robert F.; Otani, Niels F.; Fenton, Flavio H.

2013-12-01

In this article, we compare quantitatively the efficiency of three different protocols commonly used in commercial defibrillators. These are based on monophasic and both symmetric and asymmetric biphasic shocks. A numerical one-dimensional model of cardiac tissue using the bidomain formulation is used in order to test the different protocols. In particular, we performed a total of 4.8 × 106 simulations by varying shock waveform, shock energy, initial conditions, and heterogeneity in internal electrical conductivity. Whenever the shock successfully removed the reentrant dynamics in the tissue, we classified the mechanism. The analysis of the numerical data shows that biphasic shocks are significantly more efficient (by about 25%) than the corresponding monophasic ones. We determine that the increase in efficiency of the biphasic shocks can be explained by the higher proportion of newly excited tissue through the mechanism of direct activation.

Influence of the λ780nm laser light on the repair of surgical bone defects grafted or not with biphasic synthetic micro-granular hydroxylapatite+Beta-Calcium triphosphate.

PubMed

Soares, Luiz Guilherme P; Marques, Aparecida Maria C; Guarda, Milena G; Aciole, Jouber Mateus S; dos Santos, Jean Nunes; Pinheiro, Antonio Luiz B

2014-02-05

The treatment of bone loss due to different etiologic factors is difficult and many techniques aim to improve repair, including a wide range of biomaterials and, recently, photobioengineering. This work aimed to assess, through histological analysis The aim of this study was to assess, by light microscopy, the repair of bone defects grafted or not with biphasic synthetic micro-granular Calcium hydroxyapatite (HA)+Beta-TCP associated or not with Laser phototherapy - LPT (λ780nm). Forty rats were divided into 4 groups each subdivided into 2 subgroups according to the time of sacrifice (15 and 30days). Surgical bone defects were made on femur of each animal with a trephine drill. On animals of Clot group the defect was filled only by blood clot, on Laser group the defect filled with the clot was further irradiated. On animals of Biomaterial and Laser+Biomaterial groups the defect was filled by biomaterial and the last one was further irradiated (λ780nm, 70mW, spot size∼0.4cm(2), 20J/cm(2)-session, 140J/cm(2)-treatment) in four points around the defect at 48-h intervals and repeated for 2weeks. At both 15th and 30th days following sacrifice, samples were taken and analyzed by light microscopy. Many similarities were observed histologically between groups on regards bone reabsorption and neoformation, inflammatory infiltrate and collagen deposition. The criterion degree of maturation, marked by the presence of basophilic lines, indicated that the use of LPT associated with HA+Beta TCP graft, resulted in more advanced stage of bone repair at the end of the experiment. Copyright © 2014 Elsevier B.V. All rights reserved.

The Effects of Void Geometry and Contact Angle on the Absorption of Liquids into Porous Calcium Carbonate Structures.

PubMed

Ridgway, Cathy J.; Schoelkopf, Joachim; Matthews, G. Peter; Gane, Patrick A. C.; James, Philip W.

2001-07-15

The absorption (permeation) of alcohols into porous blocks of calcium carbonate has been studied experimentally and with a computer model. The experimental measurement was of change in apparent weight of a block with time after contact with liquid. The modeling used the previously developed 'Pore-Cor' model, based on unit cells of 1000 cubic pores connected by cylindrical throats. To gain some insight into absorption into voids of complex geometry, and to provide a representation of heterogeneities in surface interaction energy, the cylindrical throats were converted to double cones. Relative to cylinders, such geometries caused hold-ups of the percolation of nonwetting fluids with respect to increasing applied pressure, and a change in the rate of absorption of wetting fluids. Both the measured absorption of the alcohols and the simulated absorption of the alcohols and of water showed significant deviations from that predicted by an effective hydraulic radius approximation. The simulation demonstrated the development of a highly heterogeneous wetting front, and of preferred wetting pathways that were perturbed by inertial retardation. The findings are useful in the design of high-performance, low-waste pigments for paper coatings, and environmentally friendly printing inks, as well as in wider industrial, environmental, and geological contexts. Copyright 2001 Academic Press.

Biphasic Effects of Alcohol on Delay and Probability Discounting

PubMed Central

Bidwell, L. Cinnamon; MacKillop, James; Murphy, James G.; Grenga, Andrea; Swift, Robert M.; McGeary, John E.

2014-01-01

Delay discounting and probability discounting are behavioral economic indices of impulsive and risky decision making that have been associated with addictive behavior, but the acute biphasic effects of alcohol on these decision-making processes are not well understood. This study sought to investigate the biphasic effects of alcohol on delay and probability discounting across the ascending and descending limbs of the breath alcohol concentration (BAC) curve, which are respectively characterized by the stimulant and sedative effects of alcohol. Delay and probability discounting were measured at four time points (Baseline, Ascending, Descending, and Endpoint) across the BAC curve at two target alcohol doses (40 mg/dl and 80 mg/dl) in healthy adults (N = 23 and 27, for both doses, respectively). There was no significant effect of alcohol on delay discounting at either dose. Alcohol significantly affected probability discounting, such that reduced discounting for uncertain rewards was evident during the descending limb of the BAC curve at the lower dose (p<.05) and during both the ascending and descending limb of the BAC curve at the higher dose (p<.05). Thus, alcohol resulted in increased risky decision making, particularly during the descending limb which is primarily characterized by the sedative effects of alcohol. These findings suggest that the biphasic effects of alcohol across the ascending and descending limbs of the BAC have differential effects on behavior related to decision-making for probabilistic, but not delayed, rewards. Parallels to and distinctions from previous findings are discussed. PMID:23750692

Shock-induced termination of reentrant cardiac arrhythmias: Comparing monophasic and biphasic shock protocols

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bragard, Jean, E-mail: jbragard@unav.es; Simic, Ana; Elorza, Jorge

2013-12-15

In this article, we compare quantitatively the efficiency of three different protocols commonly used in commercial defibrillators. These are based on monophasic and both symmetric and asymmetric biphasic shocks. A numerical one–dimensional model of cardiac tissue using the bidomain formulation is used in order to test the different protocols. In particular, we performed a total of 4.8 × 10{sup 6} simulations by varying shock waveform, shock energy, initial conditions, and heterogeneity in internal electrical conductivity. Whenever the shock successfully removed the reentrant dynamics in the tissue, we classified the mechanism. The analysis of the numerical data shows that biphasic shocksmore » are significantly more efficient (by about 25%) than the corresponding monophasic ones. We determine that the increase in efficiency of the biphasic shocks can be explained by the higher proportion of newly excited tissue through the mechanism of direct activation.« less

Additively Manufactured and Surface Biofunctionalized Porous Nitinol.

PubMed

Gorgin Karaji, Z; Speirs, M; Dadbakhsh, S; Kruth, J-P; Weinans, H; Zadpoor, A A; Amin Yavari, S

2017-01-18

Enhanced bone tissue regeneration and improved osseointegration are among the most important goals in design of multifunctional orthopedic biomaterials. In this study, we used additive manufacturing (selective laser melting) to develop multifunctional porous nitinol that combines superelasticity with a rationally designed microarchitecture and biofunctionalized surface. The rational design based on triply periodic minimal surfaces aimed to properly adjust the pore size, increase the surface area (thereby amplifying the effects of surface biofunctionalization), and resemble the curvature characteristics of trabecular bone. The surface of additively manufactured (AM) porous nitinol was biofunctionalized using polydopamine-immobilized rhBMP2 for better control of the release kinetics. The actual morphological properties of porous nitinol measured by microcomputed tomography (e.g., open/close porosity, and surface area) closely matched the design values. The superelasticity originated from the austenite phase formed in the nitinol porous structure at room temperature. Polydopamine and rhBMP2 signature peaks were confirmed by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy tests. The release of rhBMP2 continued until 28 days. The early time and long-term release profiles were found to be adjustable independent of each other. In vitro cell culture showed improved cell attachment, cell proliferation, cell morphology (spreading, spindle-like shape), and cell coverage as well as elevated levels of ALP activity and increased calcium content for biofunctionalized surfaces as compared to as-manufactured specimens. The demonstrated functionalities of porous nitinol could be used as a basis for deployable orthopedic implants with rationally designed microarchitectures that maximize bone tissue regeneration performance by release of biomolecules with adjustable and well-controlled release profiles.

Processing highly porous calcium phosphate ceramics for use in bioreactor cores for culturing human liver cells in-vitro

NASA Astrophysics Data System (ADS)

Finoli, Anthony

Chronic liver disease is the 11th highest cause of death in the United States claiming over 30,000 lives in 2009. The current treatment for chronic liver failure is liver transplantation but the availability of tissue is far less than the number of patients in need. To develop human liver tissue in the lab a 3D culturing environment must be created to support the growth of a complex tissue. Hydroxyapatite (HAp) has been chosen as a scaffold material because of its biocompatibility in the body and the ability to create a bioresorbable scaffold. By using a ceramic material, it is possible to create a three dimensional, protective environment in which tissue can grow. The first part of this study is to examine the behavior of adult human liver cells grown on composites of HAp and different biocompatible hydrogels. Porous HAp has been created using an emulsion foaming technique and cells are injected into the structure after being suspended in a hydrogel and are kept in culture for up to 28 days. Functional assays, gene expression and fluorescent microscopy will be used to examine these cultures. The second part of this study will be to develop a processing technique to create a resorbable scaffold that incorporates a vascular system template. Previous experiments have shown the high temperature decomposition of HAp into resorbable calcium phosphates will be used to create a multiphase material. By controlling the amount of transformation product formed, it is proposed that the resorption of the scaffold can be tailored. To introduce a pore network to guide the growth of a vascular system, a positive-negative casting technique has also been developed. A positive polymer copy can be made of a natural vascular system and ceramic is foamed around the copy. During sintering, the polymer is pyrolyzed leaving a multiscale pore network in the ceramic. By combining these techniques, it is proposed that a calcium phosphate bioreactor core can be processed that is suitable for

Liquid infused porous surfaces for mineral fouling mitigation.

PubMed

Charpentier, Thibaut V J; Neville, Anne; Baudin, Sophie; Smith, Margaret J; Euvrard, Myriam; Bell, Ashley; Wang, Chun; Barker, Richard

2015-04-15

Prevention of mineral fouling, known as scale, is a long-standing problem in a wide variety of industrial applications, such as oil production, water treatment, and many others. The build-up of inorganic scale such as calcium carbonate on surfaces and facilities is undesirable as it can result in safety risks and associated flow assurance issues. To date the overwhelming amount of research has mainly focused on chemical inhibition of scale bulk precipitation and little attention has been paid to deposition onto surfaces. The development of novel more environmentally-friendly strategies to control mineral fouling will most probably necessitate a multifunctional approach including surface engineering. In this study, we demonstrate that liquid infused porous surfaces provide an appealing strategy for surface modification to reduce mineral scale deposition. Microporous polypyrrole (PPy) coatings were fabricated onto stainless steel substrates by electrodeposition in potentiostatic mode. Subsequent infusion of low surface energy lubricants (fluorinated oil Fluorinert FC-70 and ionic liquid 1-Butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMIm)) into the porous coatings results in liquid-repellent slippery surfaces. To assess their ability to reduce surface scaling the coatings were subjected to a calcium carbonate scaling environment and the scale on the surface was quantified using Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES). PPy surfaces infused with BMIm (and Fluorinert to a lesser extent) exhibit remarkable antifouling properties with the calcium carbonate deposition reduced by 18 times in comparison to untreated stainless steel. These scaling tests suggest a correlation between the stability of the liquid infused surfaces in artificial brines and fouling reduction efficiency. The current work shows the great potential of such novel coatings for the management of mineral scale fouling. Copyright © 2014 Elsevier Inc. All rights

Preparation of highly infective Leishmania promastigotes by cultivation on SNB-9 biphasic medium.

PubMed

Grekov, Igor; Svobodová, Milena; Nohýnková, Eva; Lipoldová, Marie

2011-12-01

Protozoan hemoflagellates Leishmania are causative agents of leishmaniases and an important biological model for study of host-pathogen interaction. A wide range of methods of Leishmania cultivation on both biphasic and liquid media is available. Biphasic media are considered to be superior for initial isolation of the parasites and obtaining high promastigote infectivity; however, liquid media are more suitable for large-scale experiments. The aim of the present study was the adaptation and optimization of the cultivation of Leishmania promastigotes on a biphasic SNB-9 (saline-neopeptone-blood 9) medium that was originally developed for Trypanosoma cultivation and combines the advantages of biphasic and liquid media. SNB-9 medium is characterized with a large volume of the liquid phase, which facilitates the manipulation with the culture and provides parasite yields comparable to parasite yields on such liquid medium as Schneider's Insect Medium. We demonstrate that SNB-9 very considerably surpasses Schneider's Insect Medium in in vitro infectivity of the parasites. Additionally, we show that the ratio of apoptotic parasites, which are important for the infectivity of the inoculum, in Leishmania culture in SNB-9 is higher than in Leishmania culture in Schneider's Insect Medium. Thus, we demonstrate that the cultivation of Leishmania on SNB-9 reliably yields highly infective promastigotes suitable for experimental infection. Copyright © 2011 Elsevier B.V. All rights reserved.

Synthesis and synchrotron characterisation of novel dual-template of hydroxyapatite scaffolds with controlled size porous distribution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lima, Thiago A. R. M.; Ilavsky, Jan; Hammons, Joshua

Hydroxyapatite (HAP) scaffolds with a hierarchical porous architecture were prepared by a new dual-template (corn starch and cetyltrimethylammonium bromide (CTAB) surfactant) used to cast HAP nanoparticles and development scaffolds with size hierarchical porous distribution. The Powder X-Ray diffraction (XRD) results showed that only the HAP crystalline phase is present in the samples after calcination; the Scanning Electron Microscopy (SEM) combined with Small Angle (SAXS) and Ultra-Small Angle X-ray Scattering (USAXS) techniques showed that the porous arrangement is promoted by needle-like HAP nanoparticles, and that the pore size distributions depend on the drip-order of the calcium and the phosphate solutions duringmore » the template preparation stage.« less

Modeling and predictions of biphasic mechanosensitive cell migration altered by cell-intrinsic properties and matrix confinement.

PubMed

Pathak, Amit

2018-04-12

Motile cells sense the stiffness of their extracellular matrix (ECM) through adhesions and respond by modulating the generated forces, which in turn lead to varying mechanosensitive migration phenotypes. Through modeling and experiments, cell migration speed is known to vary with matrix stiffness in a biphasic manner, with optimal motility at an intermediate stiffness. Here, we present a two-dimensional cell model defined by nodes and elements, integrated with subcellular modeling components corresponding to mechanotransductive adhesion formation, force generation, protrusions and node displacement. On 2D matrices, our calculations reproduce the classic biphasic dependence of migration speed on matrix stiffness and predict that cell types with higher force-generating ability do not slow down on very stiff matrices, thus disabling the biphasic response. We also predict that cell types defined by lower number of total receptors require stiffer matrices for optimal motility, which also limits the biphasic response. For a cell type with robust biphasic migration on 2D surface, simulations in channel-like confined environments of varying width and height predict faster migration in more confined matrices. Simulations performed in shallower channels predict that the biphasic mechanosensitive cell migration response is more robust on 2D micro-patterns as compared to the channel-like 3D confinement. Thus, variations in the dimensionality of matrix confinement alters the way migratory cells sense and respond to the matrix stiffness. Our calculations reveal new phenotypes of stiffness- and topography-sensitive cell migration that critically depend on both cell-intrinsic and matrix properties. These predictions may inform our understanding of various mechanosensitive modes of cell motility that could enable tumor invasion through topographically heterogeneous microenvironments. © 2018 IOP Publishing Ltd.

Bone regeneration: molecular and cellular interactions with calcium phosphate ceramics

PubMed Central

Barrère, Florence; van Blitterswijk, Clemens A; de Groot, Klaas

2006-01-01

Calcium phosphate bioceramics are widely used in orthopedic and dental applications and porous scaffolds made of them are serious candidates in the field of bone tissue engineering. They have superior properties for the stimulation of bone formation and bone bonding, both related to the specific interactions of their surface with the extracellular fluids and cells, ie, ionic exchanges, superficial molecular rearrangement and cellular activity. PMID:17717972

Retention of 125I-labeled recombinant human bone morphogenetic protein-2 by biphasic calcium phosphate or a composite sponge in a rabbit posterolateral spine arthrodesis model.

PubMed

Louis-Ugbo, John; Kim, Hak-Sun; Boden, Scott D; Mayr, Matthew T; Li, Ronald C; Seeherman, Howard; D'Augusta, Darren; Blake, Cara; Jiao, Aiping; Peckham, Steve

2002-09-01

The purpose of this study was to characterize the retention kinetics of recombinant human bone morphogenetic protein-2 (rhBMP-2) applied to two calcium-based delivery matrices. Biphasic calcium phosphate (BCP) and a composite containing BCP in an absorbable collagen sponge (BCP/ACS) were evaluated using a spinal fusion model in rabbits. rhBMP-2 labeled with radioactive iodine (125I) was used as a tracer to assess in vivo retention of rhBMP-2 in the presence of these materials (nine animals per material studied). Over a 36 day study period, animals were assessed for the following: percent administered dose retained at the implant site as measured by scintigraphic imaging (counting) with a gamma camera (all animals), radiography of the implant site (all animals), radioactivity in blood and plasma (all animals), and radioactivity in the urine and feces (three animals for each material). Radioactivity data were corrected for the decay of 125I and the attenuation between the implant in vivo and the gamma camera. Differences observed between the two materials for the area under the retention vs. time profile (AUC; 988%*day for BCP vs. 1070%*day for BCP/ACS, p = 0.57) and the mean residence time (MRT; 10.2 days for BCP vs. 7.6 days for BCP/ACS, p = 0.06) were not statistically significant. Initial retention/incorporation of rhBMP-2 was slightly higher for rhBMP-2/BCP/ACS than for rhBMP-2/BCP (96.8% vs. 86.0%, p < 0.05). Animals receiving rhBMP-2/BCP showed a longer terminal retention half-life (t1/2) than did those receiving rhBMP-2/BCP/ACS (7.5 vs. 4.5 days, p < 0.05). The urinary radioactivity recovery data supported the data obtained by scintigraphy. Over the 36 day collection period, essentially complete recovery of radioactivity (dose) in urine was observed for rhBMP-2/BCP and rhBMP-2/BCP/ACS and the majority of the radioactivity (approximately 95%) was soluble in trichloroacetic acid, suggesting extensive catabolism of rhBMP-2 before renal excretion. Fecal recovery

Sintering and microstructure property relationships of porous hydroxyapatite

NASA Astrophysics Data System (ADS)

Zakaria, Fadzil Ayad

2000-09-01

The use of ceramics inside the body, as implant materials, is a relatively new technology, the first instance having been reported just 20 years ago. The ceramics used for the repair and reconstruction of diseased, damaged or 'worn out' parts of the body are referred to as bioceramics, and such a material is hydroxyapatite. The use of calcium phosphate to repair bone defects has been based on the rationale that calcium phosphate resembles vertebrate tooth and bone mineral, and is biologically compatible with these and surrounding tissues. The concept of preparing porous hydroxyapatite was developed to prevent loosening of implants by enhancing the ingrowth of tissue into the pores (biological fixation). A structural limitation of this type of implant is the requirement to have a minimal pore size between 80- 100 m in diameter to allow bone to grow into the pores. The presence of such porosity would lead to a lower strength of the bioceramic component, but this is offset by the advantages of biocompatibility. It is well known that hydroxyapatite is a brittle material and making it porous would reduce the existing mechanical properties. This study was carried out to optimise the mechanical properties by investigating the processing conditions and methods of preparation. The effect of forming method, pore geometry, pore size, sintering cycle, sintering atmosphere and types of spherical polymers on the microstructure and mechanical properties were studied. As a consequence of the experiments, it was observed that porous hydroxyapatite is formed using an isostatic pressing technique, with 53 vol. % of HMWPVC as the porosifier. Sintering in air, with a heating rate of 50C/h, held for 1h at 600C in the first stage, and a heating rate of 100C/h, held for 4h at between 1200 and 1250C, generated a spherical pore geometry which gave the best combination of properties. This fabrication route resulted in an interconnected porous hydroxyapatite with a pore size ~90 m, the volume

Pretreatment of Eucalyptus in biphasic system for furfural production and accelerated enzymatic hydrolysis.

PubMed

Zhang, Xiudong; Bai, Yuanyuan; Cao, Xuefei; Sun, Runcang

2017-08-01

Herein, an efficient biphasic pretreatment process was developed to improve the production of furfural (FF) and glucose from Eucalyptus. The influence of formic acid and NaCl on FF production from xylose in water and various biphasic systems was investigated. Results showed that the addition of formic acid and NaCl significantly promoted the FF yield, and the biphasic system of MIBK (methyl isobutyl ketone)/water exhibited the best performance for FF production. Then the Eucalyptus was pretreated in the MIBK/water system, and a maximum FF yield of 82.0% was achieved at 180°C for 60min. Surface of the pretreated Eucalyptus became relatively rough and loose, and its crystallinity index increased obviously due to the removal of hemicelluloses and lignin. The pretreated Eucalyptus samples showed much higher enzymatic hydrolysis rates (26.2-70.7%) than the raw Eucalyptus (14.5%). Copyright © 2017 Elsevier Ltd. All rights reserved.

Accelerated cell-surface interlocking on plasma polymer-modified porous ceramics.

PubMed

Rebl, Henrike; Finke, Birgit; Schmidt, Jürgen; Mohamad, Heba S; Ihrke, Roland; Helm, Christiane A; Nebe, J Barbara

2016-12-01

Excellent osseointegration of permanent implants is crucial for the long lasting success of the implantation. To improve the osseointegrative potential, bio-inert titanium alloy surfaces (Ti6Al4V) are modified by plasma chemical oxidation (PCO®) of the titanium-oxide layer to a non-stoichiometric, amorphous calcium phosphate layer. The native titanium-oxide film measuring only a few nanometers is converted by PCO® to a thick porous calcium phosphate layer of about 10μm. In a second step the PCO surface is combined with a cell adhesive plasma-polymerized allylamine (PPAAm) nano film (5 and 50nm). Independent of the PPAAm coating homogeneity, the human osteoblast-like MG-63 cells show a remarkable increase in cell size and well-developed filopodia. Analyses of the actin cytoskeleton reveal that the cells mold to the pore shape of the PPAAm-covered PCO, thereby establishing a strong attachment to the surface. Interestingly, we could demonstrate that even though our untreated PCO shows excellent hydrophilicity, this alone is not sufficient to facilitate fast cell spreading, but the positive surface charges mediated by PPAAm. This multilayer composite material guarantees enhanced interlocking of the cells with the porous surface. Copyright © 2016 Elsevier B.V. All rights reserved.

Preparation of micro-porous bioceramic containing silicon-substituted hydroxyapatite and beta-tricalcium phosphate.

PubMed

Fuh, Lih-Jyh; Huang, Ya-Jing; Chen, Wen-Cheng; Lin, Dan-Jae

2017-06-01

Dimensional instability caused by sintering shrinkage is an inevitable drawback for conventional processing of hydroxyapatite (HA). A new preparation method for biphasic calcium phosphates was developed to increase micro pores and biodegradation without significant dimensional change. Powder pressed HA discs, under 100MPa, were immersed in a colloidal mixture of tetraethoxysilane (TEOS) and ammonium hydroxide for 10min, followed by drying, and then were sintered at 900°C, 1050°C, and 1200°C, respectively. Comparing with pure HA discs, the newly prepared product sintered up to 1200°C contained silicon substituted HA, beta-tricalcium phosphate, and calcium silicate with better micro-porosity, high specific surface area, less sintering shrinkage and the strength maintained. The cytocompatibility test demonstrated a better viability for D1 mice stem cells cultured on TEOS treated HA for 14days compared to the pure HA. This simple TEOS sol-gel pretreatment has the potential to be applied to any existing manufacturing process of HA scaffold for better control of sintering shrinkage, create micropores, and increase biodegradation. Copyright © 2017 Elsevier B.V. All rights reserved.

Biphasic Effect of Nitric Oxide on the Cardiac Voltage-dependent Anion Channel

PubMed Central

Cheng, Qunli; Sedlic, Filip; Pravdic, Danijel; Bosnjak, Zeljko J.; Kwok, Wai-Meng

2010-01-01

Nitric oxide (NO˙) effects on the cardiac mitochondrial voltage-dependent anion channel (VDAC) are unknown. The effects of exogenous NO˙ on VDAC purified from rat hearts were investigated in this study. When incorporated into lipid bilayers, VDAC was inhibited directly by an NO˙ donor, PAPA NONOate, in a concentration-dependent biphasic manner. This was prevented by an NO˙ scavenger, PTIO. The effect paralleled that of NO˙ in delaying the opening of the mitochondrial permeability transition (PT) pore. These biphasic effects on the cardiac VDAC and the PT pore reveal a tandem impact of NO˙ on the two mitochondrial entities. PMID:21156174

Effect of glycerol concentrations on the mechanical properties of additive manufactured porous calcium polyphosphate structures for bone substitute applications.

PubMed

Sheydaeian, Esmat; Vlasea, Mihaela; Woo, Ami; Pilliar, Robert; Hu, Eugene; Toyserkani, Ehsan

2017-05-01

This article addresses the effects of glycerol (GLY) concentrations on the mechanical properties of calcium polyphosphate (CPP) bone substitute structures manufactured using binder jetting additive manufacturing. To achieve this goal, nine types of water-based binder solutions were prepared with 10, 12.5, and 15 wt % GLY liquid-binding agent, mixed, respectively, with 0, 0.75, and 1.5 wt % ethylene glycol diacetate (EGD) flow enhancer. The print quality of each of the solutions was established quantitatively using an image processing algorithm. The print quality analysis narrowed down the solutions to three batches containing 1.5 wt % EGD and variable amount of GLY. These solutions were used to manufacture porous CPP bone substitute samples, which were characterized physically to determine shrinkage, porosity, microstructure, and compression strength. The 12.5 wt % GLY, 1.5 wt % EGD solution resulted in the highest mechanical strength after sintering (34.6 ± 5.8 MPa), illustrating similar mechanical properties when compared to previous studies (33.9 ± 6.3 MPa) of additively manufactured CPP bone substitutes using a commercially available binder. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 828-835, 2017. © 2016 Wiley Periodicals, Inc.

Fabrication and characterization of poly(DL-lactic-co-glycolic acid)/zirconia-hybridized amorphous calcium phosphate composites

PubMed Central

WHITED, BRYCE M.; GOLDSTEIN, AARON S.; SKRTIC, DRAGO; LOVE, BRIAN J.

2010-01-01

Several minerals, such as hydroxyapatite and β-tricalcium phosphate, have been incorporated into bioresorbable polyester bone scaffolds to increase the osteoconductivity both in vitro and in vivo. More soluble forms of calcium phosphate that release calcium and phosphate ions have been postulated as factors that increase osteoblast differentiation and mineralization. Recently, a zirconia-hybridized pyrophosphate-stabilized amorphous calcium phosphate (Zr-ACP) has been synthesized allowing controlled release of calcium and phosphate ions. When incorporated into bioresorbable scaffolds, Zr-ACP has the potential to induce osteoconductivity. In this study, 80–90% (w/v) porous poly(DL-LActic-co-glycolic acid) (PLGA) scaffolds were formed by thermal phase separation from dioxane while incorporating Zr-ACP. Scanning electron microscopy revealed a highly porous structure with a pore size ranging from a few μm to about 100 μm, smaller than we had hoped for. Zr-ACP particles were evenly dispersed in the composite structure and incorporated into the pore walls. The amorphous structure of the Zr-ACP was maintained during composite fabrication, as found by X-ray diffraction. Composite scaffolds had larger compressive yield strengths and moduli compared to pure polymer scaffolds. These initial efforts demonstrate that PLGA/Zr-ACP composites can be formed in ways that ultimately serve as promising bone scaffolds in tissue engineering. PMID:16768292

Clinical and histologic evaluation of an enamel matrix derivative combined with a biphasic calcium phosphate for the treatment of human intrabony periodontal defects.

PubMed

Sculean, Anton; Windisch, Péter; Szendröi-Kiss, Dóra; Horváth, Attila; Rosta, Péter; Becker, Jürgen; Gera, István; Schwarz, Frank

2008-10-01

The goal of this study was to evaluate clinically and histologically the healing of advanced intrabony defects following regenerative periodontal surgery with an enamel matrix derivative (EMD) combined with a new biphasic calcium phosphate (BCP). Ten subjects, each of them displaying advanced combined 1- and 2-wall intrabony defects around teeth scheduled for extraction because of advanced chronic periodontitis and further prosthodontic considerations, were included in the study. The defects were consecutively treated with a combination of EMD + BCP. A notch was placed at the most apical extent of the calculus present on the root surface or at the most apical part of the defect (if no calculus was present) to serve as a reference for the histologic evaluation. At 9 months after regenerative surgery, nine of 10 teeth were extracted with some of their surrounding soft and hard tissues and processed for histologic evaluation. There were no adverse effects related to EMD or the graft material used in any of the treated subjects. One tooth was not extracted because of the excellent clinical outcome. The clinical measurements at the nine biopsied teeth demonstrated a mean probing depth reduction of 3.3 +/- 1.4 mm and a mean clinical attachment level gain of 3.0 +/- 1.6 mm. The histologic findings indicated formation of cementum with inserting collagen fibers to a varying extent. A long junctional epithelium was observed in three of the nine biopsies. Mean new connective tissue attachment (i.e., new cementum with inserting collagen fibers) varied from 0.0 to 2.1 mm. The amount of newly formed bone was limited and varied from 0.0 to 0.7 mm. At 9 months, graft particles were still present and were mostly encapsulated in connective tissue, whereas formation of bone around the graft particles was observed only occasionally. Direct contact between the graft particles and the root surface (cementum or dentin) was not observed in any of the analyzed specimens. The combination of

Enhancing productivity for cascade biotransformation of styrene to (S)-vicinal diol with biphasic system in hollow fiber membrane bioreactor.

PubMed

Gao, Pengfei; Wu, Shuke; Praveen, Prashant; Loh, Kai-Chee; Li, Zhi

2017-03-01

Biotransformation is a green and useful tool for sustainable and selective chemical synthesis. However, it often suffers from the toxicity and inhibition from organic substrates or products. Here, we established a hollow fiber membrane bioreactor (HFMB)-based aqueous/organic biphasic system, for the first time, to enhance the productivity of a cascade biotransformation with strong substrate toxicity and inhibition. The enantioselective trans-dihydroxylation of styrene to (S)-1-phenyl-1,2-ethanediol, catalyzed by Escherichia coli (SSP1) coexpressing styrene monooxygenase and an epoxide hydrolase, was performed in HFMB with organic solvent in the shell side and aqueous cell suspension in the lumen side. Various organic solvents were investigated, and n-hexadecane was found as the best for the HFMB-based biphasic system. Comparing to other reported biphasic systems assisted by HFMB, our system not only shield much of the substrate toxicity but also deflate the product recovery burden in downstream processing as the majority of styrene stayed in organic phase while the diol product mostly remained in the aqueous phase. The established HFMB-based biphasic system enhanced the production titer to 143 mM, being 16-fold higher than the aqueous system and 1.6-fold higher than the traditional dispersive partitioning biphase system. Furthermore, the combination of biphasic system with HFMB prevents the foaming and emulsification, thus reducing the burden in downstream purification. HFMB-based biphasic system could serve as a suitable platform for enhancing the productivity of single-step or cascade biotransformation with toxic substrates to produce useful and valuable chemicals.

Cell–material interactions on biphasic polyurethane matrix

PubMed Central

Dicesare, Patrick; Fox, Wade M.; Hill, Michael J.; Krishnan, G. Rajesh; Yang, Shuying; Sarkar, Debanjan

2013-01-01

Cell–matrix interaction is a key regulator for controlling stem cell fate in regenerative tissue engineering. These interactions are induced and controlled by the nanoscale features of extracellular matrix and are mimicked on synthetic matrices to control cell structure and functions. Recent studies have shown that nanostructured matrices can modulate stem cell behavior and exert specific role in tissue regeneration. In this study, we have demonstrated that nanostructured phase morphology of synthetic matrix can control adhesion, proliferation, organization and migration of human mesenchymal stem cells (MSCs). Nanostructured biodegradable polyurethanes (PU) with segmental composition exhibit biphasic morphology at nanoscale dimensions and can control cellular features of MSCs. Biodegradable PU with polyester soft segment and hard segment composed of aliphatic diisocyanates and dipeptide chain extender were designed to examine the effect polyurethane phase morphology. By altering the polyurethane composition, morphological architecture of PU was modulated and its effect was examined on MSC. Results show that MSCs can sense the nanoscale morphology of biphasic polyurethane matrix to exhibit distinct cellular features and, thus, signifies the relevance of matrix phase morphology. The role of nanostructured phases of a synthetic matrix in controlling cell–matrix interaction provides important insights for regulation of cell behavior on synthetic matrix and, therefore, is an important tool for engineering tissue regeneration. PMID:23255285

Sol-gel derived porous bioactive nanocomposites: Synthesis and in vitro bioactivity

NASA Astrophysics Data System (ADS)

Shankhwar, Nisha; Kothiyal, G. P.; Srinivasan, A.

2013-06-01

Porous bioactive composites consisting of SiO2-CaO-Na2O-P2O5 bioactive glass-ceramic and synthetic water soluble polymer Polyvinylpyrrolidone [PVP (C6H9NO)n, MW˜40000 g/mol] have been synthesized by sol-gel route. As-prepared polymeric composites were characterized by X-ray diffraction (XRD) technique. Two major bone mineral phases, viz., hydroxyapatite [Ca10(PO4)6(OH)2] and wollastonite [calcium silicate (CaSiO3)] have been identified in the XRD patterns of the composites. Presence of these bone minerals indicates the bioactive nature of the composites. In vitro bioactivity tests confirm bioactivity in the porous composites. The flexibility offered by these bioactive polymer composites is advantageous for its application as implant material.

A pilot trial of square biphasic pulse deep brain stimulation for dystonia: The BIP dystonia study.

PubMed

Almeida, Leonardo; Martinez-Ramirez, Daniel; Ahmed, Bilal; Deeb, Wissam; Jesus, Sol De; Skinner, Jared; Terza, Matthew J; Akbar, Umer; Raike, Robert S; Hass, Chris J; Okun, Michael S

2017-04-01

Dystonia often has inconsistent benefits and requires more energy-demanding DBS settings. Studies suggest that squared biphasic pulses could provide significant clinical benefit; however, dystonia patients have not been explored. To assess safety and tolerability of square biphasic DBS in dystonia patients. This study included primary generalized or cervical dystonia patients with bilateral GPi DBS. Square biphasic pulses were implemented and patients were assessed at baseline, immediately postwashout, post-30-minute washout, 1 hour post- and 2 hours postinitiation of investigational settings. Ten participants completed the study. There were no patient-reported or clinician-observed side effects. There was improvement across time on the Toronto Western Spasmodic Torticollis Rating Scale (χ 2  = 10.7; P = 0.031). Similar improvement was detected in objective gait measurements. Square biphasic stimulation appears safe and feasible in dystonia patients with GPi DBS. Further studies are needed to evaluate possible effectiveness particularly in cervical and gait features. © 2016 International Parkinson and Movement Disorder Society. © 2017 International Parkinson and Movement Disorder Society.

Fabrication and tritium release property of Li2TiO3-Li4SiO4 biphasic ceramics

NASA Astrophysics Data System (ADS)

Yang, Mao; Ran, Guangming; Wang, Hailiang; Dang, Chen; Huang, Zhangyi; Chen, Xiaojun; Lu, Tiecheng; Xiao, Chengjian

2018-05-01

Li2TiO3-Li4SiO4 biphasic ceramic pebbles have been developed as an advanced tritium breeder due to the potential to combine the advantages of both Li2TiO3 and Li4SiO4. Wet method was developed for the pebble fabrication and Li2TiO3-Li4SiO4 biphasic ceramic pebbles were successfully prepared by wet method using the powders synthesized by hydrothermal method. The tritium release properties of the Li2TiO3-Li4SiO4 biphasic ceramic pebbles were evaluated. The biphasic pebbles exhibited good tritium release property at low temperatures and the tritium release temperature was around 470 °C. Because of the isotope exchange reaction between H2 and tritium, the addition of 0.1%H2 to purge gas He could significantly enhance the tritium gas release and the fraction of molecular form of tritium increased from 28% to 55%. The results indicate that the Li2TiO3-Li4SiO4 biphasic ceramic pebbles fabricated by wet method exhibit good tritium release property and hold promising potential as advanced breeder pebbles.

HIV-1 dynamics revisited: biphasic decay by cytotoxic T lymphocyte killing?

PubMed Central

Arnaout, R A; Nowak, M A; Wodarz, D

2000-01-01

The biphasic decay of blood viraemia in patients being treated for human immunodeficiency virus type 1 (HIV-1) infection has been explained as the decay of two distinct populations of cells: the rapid death of productively infected cells followed by the much slower elimination of a second population the identity of which remains unknown. Here we advance an alternative explanation based on the immune response against a single population of infected cells. We show that the biphasic decay can be explained simply, without invoking multiple compartments: viral load falls quickly while cytotoxic T lymphocytes (CTL) are still abundant, and more slowly as CTL disappear. We propose a method to test this idea, and develop a framework that is readily applicable to treatment of other infections. PMID:10972131

Enhanced fatigue performance of porous coated Ti6Al4V biomedical alloy

NASA Astrophysics Data System (ADS)

Apachitei, I.; Leoni, A.; Riemslag, A. C.; Fratila-Apachitei, L. E.; Duszczyk, J.

2011-05-01

Biofunctional coatings are necessary to improve integration of titanium implants in the host tissue but they may be detrimental for the implant fatigue properties. This study presents an attempt towards enhancement of the in vitro fatigue strength of plasma electrolytic oxidation coated Ti6Al4V alloy by applying shot peening process prior to coating. The electrolytic oxidation was performed in calcium acetate and calcium glycerophosphate electrolytes that allowed formation of porous oxide coatings with high surface free energy and apatite like ability. A deformed surface layer coupled with induced residual compressive stresses seem to affect oxide growth rate and fatigue behavior of the titanium alloy.

OUTWARD MOTION OF POROUS DUST AGGREGATES BY STELLAR RADIATION PRESSURE IN PROTOPLANETARY DISKS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tazaki, Ryo; Nomura, Hideko, E-mail: rtazaki@kusastro.kyoto-u.ac.jp

2015-02-01

We study the dust motion at the surface layer of protoplanetary disks. Dust grains in the surface layer migrate outward owing to angular momentum transport via gas-drag force induced by the stellar radiation pressure. In this study we calculate the mass flux of the outward motion of compact grains and porous dust aggregates by the radiation pressure. The radiation pressure force for porous dust aggregates is calculated using the T-Matrix Method for the Clusters of Spheres. First, we confirm that porous dust aggregates are forced by strong radiation pressure even if they grow to be larger aggregates, in contrast tomore » homogeneous and spherical compact grains, for which radiation pressure efficiency becomes lower when their sizes increase. In addition, we find that the outward mass flux of porous dust aggregates with monomer size of 0.1 μm is larger than that of compact grains by an order of magnitude at the disk radius of 1 AU, when their sizes are several microns. This implies that large compact grains like calcium-aluminum-rich inclusions are hardly transported to the outer region by stellar radiation pressure, whereas porous dust aggregates like chondritic-porous interplanetary dust particles are efficiently transported to the comet formation region. Crystalline silicates are possibly transported in porous dust aggregates by stellar radiation pressure from the inner hot region to the outer cold cometary region in the protosolar nebula.« less

Triple-channel microreactor for biphasic gas-liquid reactions: Photosensitized oxygenations.

PubMed

Maurya, Ram Awatar; Park, Chan Pil; Kim, Dong-Pyo

2011-01-01

A triple-channel microreactor fabricated by means of a soft-lithography technique was devised for efficient biphasic gas-liquid reactions. The excellent performance of the microreactor was demonstrated by carrying out photosensitized oxygenations of α-terpinene, citronellol, and allyl alcohols.

Scaffolds with a standardized macro-architecture fabricated from several calcium phosphate ceramics using an indirect rapid prototyping technique

PubMed Central

Wilson, C. E.; van Blitterswijk, C. A.; Verbout, A. J.; de Bruijn, J. D.

2010-01-01

Calcium phosphate ceramics, commonly applied as bone graft substitutes, are a natural choice of scaffolding material for bone tissue engineering. Evidence shows that the chemical composition, macroporosity and microporosity of these ceramics influences their behavior as bone graft substitutes and bone tissue engineering scaffolds but little has been done to optimize these parameters. One method of optimization is to place focus on a particular parameter by normalizing the influence, as much as possible, of confounding parameters. This is difficult to accomplish with traditional fabrication techniques. In this study we describe a design based rapid prototyping method of manufacturing scaffolds with virtually identical macroporous architectures from different calcium phosphate ceramic compositions. Beta-tricalcium phosphate, hydroxyapatite (at two sintering temperatures) and biphasic calcium phosphate scaffolds were manufactured. The macro- and micro-architectures of the scaffolds were characterized as well as the influence of the manufacturing method on the chemistries of the calcium phosphate compositions. The structural characteristics of the resulting scaffolds were remarkably similar. The manufacturing process had little influence on the composition of the materials except for the consistent but small addition of, or increase in, a beta-tricalcium phosphate phase. Among other applications, scaffolds produced by the method described provide a means of examining the influence of different calcium phosphate compositions while confidently excluding the influence of the macroporous structure of the scaffolds. PMID:21069558

Monophasic versus biphasic defibrillation for pediatric out-of-hospital cardiac arrest patients: a nationwide population-based study in Japan

PubMed Central

2012-01-01

Introduction Conventional monophasic defibrillators for out-of-hospital cardiac-arrest patients have been replaced with biphasic defibrillators. However, the advantage of biphasic over monophasic defibrillation for pediatric out-of-hospital cardiac-arrest patients remains unknown. This study aimed to compare the survival outcomes of pediatric out-of-hospital cardiac-arrest patients who underwent monophasic defibrillation with those who underwent biphasic defibrillation. Methods This prospective, nationwide, population-based observational study included pediatric out-of-hospital cardiac-arrest patients from January 1, 2005, to December 31, 2009. The primary outcome measure was survival at 1 month with minimal neurologic impairment. The secondary outcome measures were survival at 1 month and the return of spontaneous circulation before hospital arrival. Multivariable logistic regression analysis was performed to identify the independent association between defibrillator type (monophasic or biphasic) and outcomes. Results Among 5,628 pediatric out-of-hospital cardiac-arrest patients (1 through 17 years old), 430 who received defibrillation shock with monophasic or biphasic defibrillator were analyzed. The number of patients who received defibrillation shock with monophasic defibrillator was 127 (30%), and 303 (70%) received defibrillation shock with biphasic defibrillator. The survival rates at 1 month with minimal neurologic impairment were 17.5% and 24.4%, the survival rates at 1 month were 32.3% and 35.6%, and the rates of return of spontaneous circulation before hospital arrival were 24.4% and 27.4% in the monophasic and biphasic defibrillator groups, respectively. Hierarchic logistic regression analyses by using generalized estimation equations found no significant difference between the two groups in terms of 1-month survival with minimal neurologic impairment (odds ratio (OR), 1.57; 95% confidence interval (CI), 0.87 to 2.83; P = 0.14) and 1-month survival (OR

Interconnected porous hydroxyapatite ceramics for bone tissue engineering

PubMed Central

Yoshikawa, Hideki; Tamai, Noriyuki; Murase, Tsuyoshi; Myoui, Akira

2008-01-01

Several porous calcium hydroxyapatite (HA) ceramics have been used clinically as bone substitutes, but most of them possessed few interpore connections, resulting in pathological fracture probably due to poor bone formation within the substitute. We recently developed a fully interconnected porous HA ceramic (IP-CHA) by adopting the ‘foam-gel’ technique. The IP-CHA had a three-dimensional structure with spherical pores of uniform size (average 150 μm, porosity 75%), which were interconnected by window-like holes (average diameter 40 μm), and also demonstrated adequate compression strength (10–12 MPa). In animal experiments, the IP-CHA showed superior osteoconduction, with the majority of pores filled with newly formed bone. The interconnected porous structure facilitates bone tissue engineering by allowing the introduction of mesenchymal cells, osteotropic agents such as bone morphogenetic protein or vasculature into the pores. Clinically, we have applied the IP-CHA to treat various bony defects in orthopaedic surgery, and radiographic examinations demonstrated that grafted IP-CHA gained radiopacity more quickly than the synthetic HA in clinical use previously. We review the accumulated data on bone tissue engineering using the novel scaffold and on clinical application in the orthopaedic field. PMID:19106069

Synthesis, characterization, and in-vitro cytocompatibility of amorphous β-tri-calcium magnesium phosphate ceramics.

PubMed

Singh, Satish S; Roy, Abhijit; Lee, Boeun; Banerjee, Ipsita; Kumta, Prashant N

2016-10-01

Biphasic mixtures of crystalline β-tricalcium magnesium phosphate (β-TCMP) and an amorphous calcium magnesium phosphate have been synthesized and reported to support enhanced hMSC differentiation in comparison to β-tricalcium phosphate (β-TCP) due to the release of increased amounts of bioactive ions. In the current study, completely amorphous β-TCMP has been synthesized which is capable of releasing increased amounts of Mg(2+) and PO4(3-) ions, rather than a biphasic mixture as earlier reported. The amorphous phase formed was observed to crystallize between temperatures of 400-600°C. The scaffolds prepared with amorphous β-TCMP were capable of supporting enhanced hMSC proliferation and differentiation in comparison to commercially available β-TCP. However, a similar gene expression of mature osteoblast markers, OCN and COL-1, in comparison to biphasic β-TCMP was observed. To further study the role of Mg(2+) and PO4(3-) ions in regulating hMSC osteogenic differentiation, the capability of hMSCs to mineralize in growth media supplemented with Mg(2+) and PO4(3-) ions was studied. Interestingly, 5mM PO4(3-) supported mineralization while the addition of 5mM Mg(2+) to 5mM PO4(3-) inhibited mineralization. It was therefore concluded that the release of Ca(2+) ions from β-TCMP scaffolds also plays a role in regulating osteogenic differentiation on these scaffolds and it is noted that further work is required to more accurately determine the exact role of Mg(2+) in regulating hMSC osteogenic differentiation. Copyright © 2016 Elsevier B.V. All rights reserved.

Aqueous biphasic extraction process with pH and particle control

DOEpatents

Chaiko, David J.; Mensah-Biney, R.

1995-01-01

A process for aqueous biphasic extraction of metallic oxides and the like from substances containing silica. Control of media pH enables efficient and effective partition of mixture components. The inventive method may be employed to remove excess silica from kaolin clay.

Triple-channel microreactor for biphasic gas–liquid reactions: Photosensitized oxygenations

PubMed Central

Maurya, Ram Awatar; Park, Chan Pil

2011-01-01

Summary A triple-channel microreactor fabricated by means of a soft-lithography technique was devised for efficient biphasic gas–liquid reactions. The excellent performance of the microreactor was demonstrated by carrying out photosensitized oxygenations of α-terpinene, citronellol, and allyl alcohols. PMID:21915221

The Role of Inorganic Polyphosphates in the Formation of Bioengineered Cartilage Incorporating a Zone of Calcified Cartilage In Vitro

NASA Astrophysics Data System (ADS)

St-Pierre, Jean-Philippe

The development of bioengineered cartilage for replacement of damaged articular cartilage has gained momentum in recent years. One such approach has been developed in the Kandel lab, whereby cartilage is formed by seeding primary articular chondrocytes on the top surface of a porous biodegradable calcium polyphosphate (CPP) bone substitute, permitting anchorage of the tissue within the pores of the substrate; however, the interfacial shear properties of the tissue-substrate interface of these biphasic constructs are 1 to 2 orders of magnitude lower than the native cartilage-subchondral bone interface. To overcome this limitation, a strategy was devised to generate a zone of calcified cartilage (ZCC), thereby mimicking the native architecture of the osteochondral junction; however, the ZCC was located slightly above the cartilage-CPP interface. Thus, it was hypothesized that polyphosphate released from the CPP substrate and accumulating in the tissue inhibits the formation of the ZCC at the tissue-substrate interface. Based on this information, a strategy was devised to generate biphasic constructs incorporating a properly located ZCC. This approach involved the application of a thin calcium phosphate film to the surfaces of porous CPP via a sol-gel procedure, thereby limiting the accumulation of polyphosphate in the cartilaginous tissue. This modification to the substrate surface did not negatively impact the quality of the in vitro-formed cartilage tissue or the ZCC. Interfacial shear testing of biphasic constructs demonstrated significantly improved interfacial shear properties in the presence of a properly located ZCC. These studies also led to the observation that chondrocytes produce endogenous polyphosphate and that its levels in deep zone cartilage appear inversely related to mineral deposition within the tissue. Using an in vitro model of cartilage calcification, it was demonstrated that polyphosphate levels are modulated in part by the inhibitory effects

Nucleation of biomimetic apatite in synthetic body fluids: dense and porous scaffold development.

PubMed

Landi, Elena; Tampieri, Anna; Celotti, Giancarlo; Langenati, Ratih; Sandri, Monica; Sprio, Simone

2005-06-01

The effectiveness of synthetic body fluids (SBF) as biomimetic sources to synthesize carbonated hydroxyapatite (CHA) powder similar to the biological inorganic phase, in terms of composition and microstructure, was investigated. CHA apatite powders were prepared following two widely experimented routes: (1) calcium nitrate tetrahydrate and diammonium hydrogen phosphate and (2) calcium hydroxide and ortophosphoric acid, but using SBF as synthesis medium instead of pure water. The characteristics of the as-prepared powders were compared, also with the features of apatite powders synthesized via pure water-based classical methods. The powder thermal resistance and behaviour during densification were studied together with the mechanical properties of the dense samples. The sponge impregnation process was used to prepare porous samples having morphological and mechanical characteristics suitable for bone substitution. Using this novel synthesis was it possible to prepare nanosized (approximately equal to 20 nm), pure, carbonate apatite powder containing Mg, Na, K ions, with morphological and compositional features mimicking natural apatite and with improved thermal properties. After sintering at 1250 degrees C the carbonate-free apatite porous samples showed a surprising, high compressive strength together with a biomimetic morphology.

Biphasic influence of dexamethasone exposure on embryonic vertebrate skeleton development

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng, Xin; Chen, Jian-long; Ma, Zheng-lai

Dexamethasone (Dex) has anti-inflammatory and immunomodulatory properties against many conditions. There is a potential teratogenic risk, however, for pregnant women receiving Dex treatment. It has been claimed that Dex exposure during pregnancy could affect osteogenesis in the developing embryo, which still remains highly controversial. In this study, we employed chick embryos to investigate the effects of Dex exposure on skeletal development using combined in vivo and in vitro approach. First, we demonstrated that Dex (10{sup −8}–10{sup −6} μmol/egg) exposure resulted in a shortening of the developing long bones of chick embryos, and it accelerated the deposition of calcium salts. Secondly,more » histological analysis of chick embryo phalanxes exhibited Dex exposure inhibited the proliferation of chondrocytes, increased apoptosis of chondrocytes and osteocytes, and led to atypical arranged hypertrophic chondrocytes. The expression of genes related to skeletogenesis was also analyzed by semi-quantitative RT-PCR. The expression of ALP, Col1a2 and Col2a1 was decreased in the Dex treated phalanxes. A detectable increase was observed in Runx-2 and Mmp-13 expression. We next examined how Dex affected the different stages of skeletogenesis in vitro. Utilizing limb bud mesenchyme micromass cultures, we determined that Dex exposure exerted no effect on apoptosis but impaired chondrogenic cell proliferation. Interestingly, low dose of Dex moderately prompted nodule formation as revealed by alcian blue staining, but higher doses of Dex significantly inhibited similar chondrogenic differentiation. Dex exposure did not induce apoptosis when the chondrogenic precursors were still at the mesenchymal stage, however, cell viability was suppressed when the mesenchyme differentiated into chondrocytes. Alizarin red staining revealed that the capacity to form mineralized bone nodules was correspondingly enhanced as Dex concentrations increased. The mRNA level of Sox-9 was

Biphasic Kinetic Behavior of Nitrate Reductase from Heterocystous, Nitrogen-Fixing Cyanobacteria 1

PubMed Central

Martin-Nieto, José; Flores, Enrique; Herrero, Antonia

1992-01-01

Nitrate reductase activity from filamentous, heterocyst-forming cyanobacteria showed a biphasic kinetic behavior with respect to nitrate as the variable substrate. Two kinetic components were detected, the first showing a higher affinity for nitrate (Km, 0.05-0.25 mm) and a lower catalytic activity and the second showing a lower affinity for nitrate (Km, 5-25 mm) and a higher (3- to 5-fold) catalytic activity. In contrast, among unicellular cyanobacteria, most representatives studied exhibited a monophasic, Michaelis-Menten kinetic pattern for nitrate reductase activity. Biphasic kinetics remained unchanged with the use of different assay conditions (i.e. cell disruption or permeabilization, two different electron donors) or throughout partial purification of the enzyme. PMID:16652939

Stem cell engineered bone with calcium-phosphate coated porous titanium scaffold or silicon hydroxyapatite granules for revision total joint arthroplasty.

PubMed

García-Gareta, Elena; Hua, Jia; Rayan, Faizal; Blunn, Gordon W

2014-06-01

Aseptic loosening in total joint replacements (TJRs) is mainly caused by osteolysis which leads to a reduction of the bone stock necessary for implant fixation in revision TJRs. Our aim was to develop bone tissue-engineered constructs based on scaffolds of clinical relevance in revision TJRs to reconstitute the bone stock at revision operations by using a perfusion bioreactor system (PBRS). The hypothesis was that a PBRS will enhance mesenchymal stem cells (MSCs) proliferation and osteogenic differentiation and will provide an even distribution of MSCs throughout the scaffolds when compared to static cultures. A PBRS was designed and implemented. Scaffolds, silicon substituted hydroxyapatite granules and calcium-phosphate coated porous TiAl6V4 cylinders, were seeded with MSCs and cultured either in static conditions or in the PBRS at 0.75 mL/min. Statistically significant increased cell proliferation and alkaline phosphatase activity was found in samples cultured in the PBRS. Histology revealed a more even cell distribution in the perfused constructs. SEM showed that cells arranged in sheets. Long cytoplasmic processes attached the cells to the scaffolds. We conclude that a novel tissue engineering approach to address the issue of poor bone stock at revision operations is feasible by using a PBRS.

Aqueous biphasic extraction process with pH and particle control

DOEpatents

Chaiko, D.J.; Mensah-Biney, R.

1995-05-02

A process for aqueous biphasic extraction of metallic oxides and the like from substances containing silica. Control of media pH enables efficient and effective partition of mixture components. The inventive method may be employed to remove excess silica from kaolin clay. 2 figs.

Predictive Feedback Can Account for Biphasic Responses in the Lateral Geniculate Nucleus

PubMed Central

Jehee, Janneke F. M.; Ballard, Dana H.

2009-01-01

Biphasic neural response properties, where the optimal stimulus for driving a neural response changes from one stimulus pattern to the opposite stimulus pattern over short periods of time, have been described in several visual areas, including lateral geniculate nucleus (LGN), primary visual cortex (V1), and middle temporal area (MT). We describe a hierarchical model of predictive coding and simulations that capture these temporal variations in neuronal response properties. We focus on the LGN-V1 circuit and find that after training on natural images the model exhibits the brain's LGN-V1 connectivity structure, in which the structure of V1 receptive fields is linked to the spatial alignment and properties of center-surround cells in the LGN. In addition, the spatio-temporal response profile of LGN model neurons is biphasic in structure, resembling the biphasic response structure of neurons in cat LGN. Moreover, the model displays a specific pattern of influence of feedback, where LGN receptive fields that are aligned over a simple cell receptive field zone of the same polarity decrease their responses while neurons of opposite polarity increase their responses with feedback. This phase-reversed pattern of influence was recently observed in neurophysiology. These results corroborate the idea that predictive feedback is a general coding strategy in the brain. PMID:19412529

Biphasic papillary renal cell carcinoma is a rare morphological variant with frequent multifocality: a study of 28 cases.

PubMed

Trpkov, Kiril; Athanazio, Daniel; Magi-Galluzzi, Cristina; Yilmaz, Helene; Clouston, David; Agaimy, Abbas; Williamson, Sean R; Brimo, Fadi; Lopez, Jose I; Ulamec, Monika; Rioux-Leclercq, Nathalie; Kassem, Maysoun; Gupta, Nilesh; Hartmann, Arndt; Leroy, Xavier; Bashir, Samir Al; Yilmaz, Asli; Hes, Ondřej

2018-04-01

To further characterise biphasic squamoid renal cell carcinoma (RCC), a recently proposed variant of papillary RCC. We identified 28 tumours from multiple institutions. They typically showed two cell populations-larger cells with eosinophilic cytoplasm and higher-grade nuclei, surrounded by smaller, amphophilic cells with scanty cytoplasm. The dual morphology was variable (median 72.5% of tumour, range 5-100%); emperipolesis was found in all cases. The male/female ratio was 2:1, and the median age was 55 years (range 39-86 years). The median tumour size was 20 mm (range 9-65 mm). Pathological stage pT1a was found in 21 cases, pT1b in three, and pT3a and pT3b in one each (two not available). Multifocality was found in 32%: multifocal biphasic RCC in one case, biphasic + papillary RCC in two cases, biphasic + clear cell RCC in three cases, biphasic + low-grade urothelial carcinoma of the renal pelvis in one case, and biphasic + Birt-Hogg-Dubé syndrome in one case. Positive immunostains included: PAX8, cytokeratin (CK) 7, α-methylacyl-CoA racemase, epithelial membrane antigen, and vimentin. Cyclin D1 was expressed only in the larger cells. The Ki67 index was higher in the larger cells (median 5% versus ≤1%). Negative stains included: carbonic anhydrase 9, CD117, GATA-3, WT1, CK5/6, and CK20; CD10 and 34βE12 were variably expressed. Gains of chromosomes 7 and 17 were found in two evaluated cases. Follow-up was available for 23 patients (median 24 months, range 1-244 months): 19 were alive without disease, one was alive with recurrence, and one had died of disease (two had died of other causes). Biphasic papillary RCC is a rare variant of papillary RCC, and is often multifocal. © 2017 John Wiley & Sons Ltd.

Biphasic patterns of diversification and the emergence of modules

PubMed Central

Mittenthal, Jay; Caetano-Anollés, Derek; Caetano-Anollés, Gustavo

2012-01-01

The intricate molecular and cellular structure of organisms converts energy to work, which builds and maintains structure. Evolving structure implements modules, in which parts are tightly linked. Each module performs characteristic functions. In this work we propose that a module can emerge through two phases of diversification of parts. Early in the first phase of this biphasic pattern, the parts have weak linkage—they interact weakly and associate variously. The parts diversify and compete. Under selection for performance, interactions among the parts increasingly constrain their structure and associations. As many variants are eliminated, parts self-organize into modules with tight linkage. Linkage may increase in response to exogenous stresses as well as endogenous processes. In the second phase of diversification, variants of the module and its functions evolve and become new parts for a new cycle of generation of higher-level modules. This linkage hypothesis can interpret biphasic patterns in the diversification of protein domain structure, RNA and protein shapes, and networks in metabolism, codes, and embryos, and can explain hierarchical levels of structural organization that are widespread in biology. PMID:22891076

Biphasic synovial sarcoma in the cervical spine: Case report.

PubMed

Foreman, Stephen M; Stahl, Michael J

2011-05-23

Synovial sarcoma is a rare malignant neoplasm of soft tissue that typically arising near large joints of the upper and lower extremities in young adult males. Only 3% of these neoplasms have been found to arise in the head and neck region. To our knowledge, there are limited reports in the literature of this neoplasm in the cervical spine.A case of biphasic synovial sarcoma of the cervical spine is reviewed. A 29 year-old male presented with pain on the left side of the cervical spine. Physical examination revealed a global loss of cervical motion and large, palpable mass in the left paravertebral area. The long-delayed Magnetic Resonance (MR) scan revealed a soft tissue mass measuring 8.3 centimeters (cm) × 5.7 cm that was surgically removed. A malignant biphasic synovial sarcoma was diagnosed on pathologic examination.The clinical and imaging findings of an atypically located synovial sarcoma are reviewed. This case report emphasizes the consequences of a limited differential diagnosis, prolonged treatment and the failure to perform timely diagnostic imaging in the presence of a paraspinal mass.

Confinement effects on dipolar relaxation by translational dynamics of liquids in porous silica glasses

NASA Astrophysics Data System (ADS)

Korb, J.-P.; Xu, Shu; Jonas, J.

1993-02-01

A theory of dipolar relaxation by translational diffusion of a nonwetting liquid confined in model porous media is presented. We obtain expressions of the rates of spin-lattice relaxation 1/T1, spin-spin relaxation 1/T2, and spin-lattice relaxation in the rotating frame 1/T1ρ, which depend on the average pore size d. The frequency variations of these rates are intermediate between the two-dimensional and three-dimensional results. At small frequency they vary logarithmically for small d and tend progressively to a constant with increasing d. For small pore sizes we obtain quadratic confinement dependences of these rates (∝1/d2), at variance with the linear (∝1/d) relation coming from the biphasic fast exchange model usually applied for a wetting liquid in porous media. We apply such a theory to the 1H NMR relaxation of methylcyclohexane liquid in sol-gel porous silica glasses with a narrow pore-size distribution. The experiments confirm the theoretical predictions for very weak interacting solvent in porous silica glasses of pore sizes varying in the range of 18.4-87.2 Å and in the bulk. At the limit of small pores, the logarithmic frequency dependencies of 1/T1ρ and 1/T1 observed over several decades of frequency are interpreted with a model of unbounded two-dimensional diffusion in a layered geometry. The leveling off of the 1/T1ρ low-frequency dependence is interpreted in terms of the bounded two-dimensional diffusion due to the finite length L of the pores. An estimate of a finite size of L=100 Å is in excellent agreement with the experimental results of the transmission electron microscopy study of platinium-carbon replicated xerogels.

Usefulness of p16/CDKN2A fluorescence in situ hybridization and BAP1 immunohistochemistry for the diagnosis of biphasic mesothelioma.

PubMed

Wu, Di; Hiroshima, Kenzo; Yusa, Toshikazu; Ozaki, Daisuke; Koh, Eitetsu; Sekine, Yasuo; Matsumoto, Shinji; Nabeshima, Kazuki; Sato, Ayuko; Tsujimura, Tohru; Yamakawa, Hisami; Tada, Yuji; Shimada, Hideaki; Tagawa, Masatoshi

2017-02-01

Malignant mesothelioma is a highly aggressive neoplasm, and the histologic subtype is one of the most reliable prognostic factors. Some biphasic mesotheliomas are difficult to distinguish from epithelioid mesotheliomas with atypical fibrous stroma. The aim of this study was to analyze p16/CDKN2A deletions in mesotheliomas by fluorescence in situ hybridization (FISH) and BAP1 immunohistochemistry to evaluate their potential role in the diagnosis of biphasic mesothelioma. We collected 38 cases of pleural mesotheliomas. The results of this study clearly distinguished 29 cases of biphasic mesothelioma from 9 cases of epithelioid mesothelioma. The proportion of biphasic mesotheliomas with homozygous deletions of p16/CDKN2A in total was 96.6% (28/29). Homozygous deletion of p16/CDKN2A was observed in 18 (94.7%) of 19 biphasic mesotheliomas with 100% concordance of the p16/CDKN2A deletion status between the epithelioid and sarcomatoid components in each case. Homozygous deletion of the p16/CDKN2A was observed in 7 (77.8%) of 9 epithelioid mesotheliomas but not in fibrous stroma. BAP1 loss was observed in 5 (38.5%) of 13 biphasic mesotheliomas and in both epithelioid and sarcomatoid components. BAP1 loss was observed in 5 (62.5%) of 8 epithelioid mesotheliomas but not in fibrous stroma. Homozygous deletion of p16/CDKN2A is common in biphasic mesotheliomas, and the analysis of only one component of mesothelioma is sufficient to show that the tumor is malignant. However, compared with histology alone, FISH analysis of the p16/CDKN2A status and BAP1 immunohistochemistry in the spindled mesothelium provide a more objective means to differentiate between biphasic mesothelioma and epithelioid mesothelioma with atypical stromal cells. Copyright © 2016 Elsevier Inc. All rights reserved.

Analysis of the Angle of Maximal Stability and Flow Regime Transitions in Different Proportions of Bi-phasic Granular Matter Mixtures

NASA Astrophysics Data System (ADS)

Maquiling, Joel Tiu; Visaga, Shane Marie

This study investigates the dependence of the critical angle θc of stability on different mass ratios γ of layered bi-phasic granular matter mixtures and on the critical angle of its mono-disperse individual components. It also aims to investigate and explain regime transitions of granular matter flowing down a tilted rough inclined plane. Critical angles and flow regimes for a bi-phasic mixture of sago spheres and bi-phasic pepper mixture of fine powder and rough spheres were observed and measured using video analysis. The critical angles θc MD of mono-disperse granular matter and θc BP of biphasic granular matter mixtures were observed and compared. All types of flow regimes and a supramaximal critical angle of stability exist at mass ratio γ = 0.5 for all biphasic granular matter mixtures. The θc BP of sago spheres was higher than the θc MD of sago spheres. Moreover, the θc BP of the pepper mixture was in between the θc MD of fine pepper and θc MD of rough pepper spheres. Comparison of different granular material shows that θc MD is not simply a function of particle diameter but of particle roughness as well. Results point to a superposition mechanism of the critical angles of biphasic sphere mixtures.

Porous silicon confers bioactivity to polycaprolactone composites in vitro.

PubMed

Henstock, J R; Ruktanonchai, U R; Canham, L T; Anderson, S I

2014-04-01

Silicon is an essential element for healthy bone development and supplementation with its bioavailable form (silicic acid) leads to enhancement of osteogenesis both in vivo and in vitro. Porous silicon (pSi) is a novel material with emerging applications in opto-electronics and drug delivery which dissolves to yield silicic acid as the sole degradation product, allowing the specific importance of soluble silicates for biomaterials to be investigated in isolation without the elution of other ionic species. Using polycaprolactone as a bioresorbable carrier for porous silicon microparticles, we found that composites containing pSi yielded more than twice the amount of bioavailable silicic acid than composites containing the same mass of 45S5 Bioglass. When incubated in a simulated body fluid, the addition of pSi to polycaprolactone significantly increased the deposition of calcium phosphate. Interestingly, the apatites formed had a Ca:P ratio directly proportional to the silicic acid concentration, indicating that silicon-substituted hydroxyapatites were being spontaneously formed as a first order reaction. Primary human osteoblasts cultured on the surface of the composite exhibited peak alkaline phosphatase activity at day 14, with a proportional relationship between pSi content and both osteoblast proliferation and collagen production over 4 weeks. Culturing the composite with J744A.1 murine macrophages demonstrated that porous silicon does not elicit an immune response and may even inhibit it. Porous silicon may therefore be an important next generation biomaterial with unique properties for applications in orthopaedic tissue engineering.

Design and Fabrication of Complex Scaffolds for Bone Defect Healing: Combined 3D Plotting of a Calcium Phosphate Cement and a Growth Factor-Loaded Hydrogel.

PubMed

Ahlfeld, Tilman; Akkineni, Ashwini Rahul; Förster, Yvonne; Köhler, Tino; Knaack, Sven; Gelinsky, Michael; Lode, Anja

2017-01-01

Additive manufacturing enables the fabrication of scaffolds with defined architecture. Versatile printing technologies such as extrusion-based 3D plotting allow in addition the incorporation of biological components increasing the capability to restore functional tissues. We have recently described the fabrication of calcium phosphate cement (CPC) scaffolds by 3D plotting of an oil-based CPC paste under mild conditions. In the present study, we have developed a strategy for growth factor loading based on multichannel plotting: a biphasic scaffold design was realised combining CPC with VEGF-laden, highly concentrated hydrogel strands. As hydrogel component, alginate and an alginate-gellan gum blend were evaluated; the blend exhibited a more favourable VEGF release profile and was chosen for biphasic scaffold fabrication. After plotting, two-step post-processing was performed for both, hydrogel crosslinking and CPC setting, which was shown to be compatible with both materials. Finally, a scaffold was designed and fabricated which can be applied for testing in a rat critical size femur defect. Optimization of CPC plotting enabled the fabrication of highly resolved structures with strand diameters of only 200 µm. Micro-computed tomography revealed a precise strand arrangement and an interconnected pore space within the biphasic scaffold even in swollen state of the hydrogel strands.

Sol-gel method to fabricate CaP scaffolds by robocasting for tissue engineering.

PubMed

Houmard, Manuel; Fu, Qiang; Saiz, Eduardo; Tomsia, Antoni P

2012-04-01

Highly porous calcium phosphate (CaP) scaffolds for bone-tissue engineering were fabricated by combining a robocasting process with a sol-gel synthesis that mixed Calcium Nitrate Tetrahydrate and Triethyl Phosphite precursors in an aqueous medium. The resulting gels were used to print scaffolds by robocasting without the use of binder to increase the viscosity of the paste. X-ray diffraction analysis confirmed that the process yielded hydroxyapatite and β-tricalcium phosphate biphasic composite powders. Thus, the scaffold composition after crystallization of the amorphous structure could be easily modified by varying the initial Ca/P ratio during synthesis. The compressive strengths of the scaffolds are ~6 MPa, which is in the range of human cancellous bone (2-12 MPa). These highly porous scaffolds (~73 vol% porosity) are composed of macro-pores of ~260 μm in size; such porosity is expected to enable bone ingrowth into the scaffold for bone repair applications. The chemistry, porosity, and surface topography of such scaffolds can also be modified by the process parameters to favor bone formation. The studied sol-gel process can be used to coat these scaffolds by dip-coating, which induces a significant enhancement of mechanical properties. This can adjust scaffold properties such as composition and surface morphology, which consequently may improve their performances.

Ectopic Osteoid and Bone Formation by Three Calcium-Phosphate Ceramics in Rats, Rabbits and Dogs

PubMed Central

Wang, Liao; Zhang, Bi; Bao, Chongyun; Habibovic, Pamela; Hu, Jing; Zhang, Xingdong

2014-01-01

Calcium phosphate ceramics with specific physicochemical properties have been shown to induce de novo bone formation upon ectopic implantation in a number of animal models. In this study we explored the influence of physicochemical properties as well as the animal species on material-induced ectopic bone formation. Three bioceramics were used for the study: phase-pure hydroxyapatite (HA) sintered at 1200°C and two biphasic calcium phosphate (BCP) ceramics, consisting of 60 wt.% HA and 40 wt.% TCP (β-Tricalcium phosphate), sintered at either 1100°C or 1200°C. 108 samples of each ceramic were intramuscularly implanted in dogs, rabbits, and rats for 6, 12, and 24 weeks respectively. Histological and histomorphometrical analyses illustrated that ectopic bone and/or osteoid tissue formation was most pronounced in BCP sintered at 1100°C and most limited in HA, independent of the animal model. Concerning the effect of animal species, ectopic bone formation reproducibly occurred in dogs, while in rabbits and rats, new tissue formation was mainly limited to osteoid. The results of this study confirmed that the incidence and the extent of material-induced bone formation are related to both the physicochemical properties of calcium phosphate ceramics and the animal model. PMID:25229501

Microstructures of Randall's plaques and their interfaces with calcium oxalate monohydrate kidney stones reflect underlying mineral precipitation mechanisms.

PubMed

Sethmann, Ingo; Wendt-Nordahl, Gunnar; Knoll, Thomas; Enzmann, Frieder; Simon, Ludwig; Kleebe, Hans-Joachim

2017-06-01

Randall's plaques (RP) are preferred sites for the formation of calcium oxalate monohydrate (COM) kidney stones. However, although processes of interstitial calcium phosphate (CaP) plaque formation are not well understood, the potential of plaque microstructures as indicators of CaP precipitation conditions received only limited attention. We investigated RP-associated COM stones for structural details of the calcified tissues and microstructural features of plaque-stone interfaces as indicators of the initial processes of stone formation. Significantly increased CaP supersaturation can be expected for interstitial fluid, if reabsorbed ions from the tubular system continuously diffuse into the collagenous connective tissue. Densely packed, fine-grained CaP particles were found in dense textures of basement membranes while larger, laminated particles were scattered in coarse-meshed interstitial tissue, which we propose to be due to differential spatial confinements and restrictions of ion diffusion. Particle morphologies suggest an initial precipitation as metastable amorphous calcium phosphate (ACP). Morphologies and arrangements of first COM crystals at the RP-stone interface ranged from stacked euhedral platelets to skeletal morphologies and even porous, dendritic structures, indicating, in this order, increasing levels of COM supersaturation. Furthermore, these first COM crystals were often coated with CaP. On this basis, we propose that ions from CaP-supersaturated interstitial fluid may diffuse through porous RP into the urine, where a resulting local increase in COM supersaturation could trigger crystal nucleation and, hence, initiate stone formation. Ion-depleted fluid in persistent pores of initial COM layers may get replenished from interstitial fluid, leading to CaP precipitation in porous COM.

In vivo testing of porous Ti-25Nb alloy serving as a femoral stem prosthesis in a rabbit model

PubMed Central

Weng, Xiaojun; Yang, Hailin; Xu, Jian; Li, Xiaosheng; Liao, Qiande; Wang, Jing

2016-01-01

The aim of the present study was to observe the performance of Ti-25Nb alloys with various porosities as femoral stem prostheses in a rabbit model, thus providing basic experimental evidence for the development of porous prostheses. The porous Ti-25Nb alloy prostheses were designed according to the morphology of the medullary cavity. These prostheses were placed into the femoral medullary cavities in 36 New Zealand white rabbits. Postoperative X-ray films, scanning electron microscopy (SEM) of the implant interface, energy-dispersive spectroscopy (EDS) analysis of the implant surface, pulling-out test and general observations were conducted. The specimens showed good biocompatibility; there was no obvious bone absorption in porous Ti-25Nb specimens with different porosities at different time points observed using X-ray films. Under SEM examination, calcium deposits were observed inside the pores and in the interface between bone and prostheses. The EDS analysis demonstrated that calcium deposits were present on the surface of the prostheses at the eight-week point postoperatively. The pulling-out test showed good bonding strength between bone and implant; after pulling out, the surface and inside the pores of the prostheses all presented bone mass. Porous Ti-25Nb alloy implants presents good biocompatibility as well as providing a biological fixation between the bone and implant. A porosity of 70% is more advantageous to the newborn bone ingrowth, combined with achieving a more solid bone-implant interface. PMID:27602063

Allosteric Effects of the Anti-Psychotic Drug Trifluoperazine on the Energetics of Calcium Binding by Calmodulin

PubMed Central

Feldkamp, Michael D.; O'Donnell, Susan E.; Yu, Liping; Shea, Madeline A.

2010-01-01

Trifluoperazine (TFP; Stelazine™) is an antagonist of calmodulin (CaM), an essential regulator of calcium-dependent signal transduction. Reports differ regarding whether, or where, TFP binds to apo CaM. Three crystallographic structures (1CTR, 1A29, 1LIN) show TFP bound to (Ca2+)4-CaM in ratios of 1, 2 or 4 TFP per CaM. In all of these, CaM domains adopt the “open” conformation seen in CaM-kinase complexes having increased calcium affinity. Most reports suggest TFP also increases calcium affinity of CaM. To compare TFP binding to apo CaM and (Ca2+)4-CaM, and explore differential effects on the N- and C-domains of CaM, stoichiometric TFP titrations of CaM were monitored by 15N-HSQC NMR. Two TFP bound to apo CaM, while four bound to (Ca2+)4-CaM. In both cases, the preferred site was in the C-domain. During the titrations, biphasic responses for some resonances suggested inter-site interactions. TFP-binding sites in apo CaM appeared distinct from those in (Ca2+)4-CaM. In equilibrium calcium titrations at defined ratios of TFP:CaM, TFP reduced calcium affinity at most levels tested; this is similar to the effect of many IQ-motifs on CaM. However, at the highest level tested, TFP raised the calcium affinity of the N-domain of CaM. A model of conformational switching is proposed to explain how TFP can exert opposing allosteric effects on calcium affinity by binding to different sites in the “closed”, “semi-open” and “open” domains of CaM. In physiological processes, apo CaM, as well as (Ca2+)4-CaM, needs to be considered a potential target of drug action. PMID:20544963

Fabrication and evaluation of interconnected porous carbonate apatite from alpha tricalcium phosphate spheres.

PubMed

Ishikawa, Kunio; Arifta, Tya Indah; Hayashi, Koichiro; Tsuru, Kanji

2018-03-26

Carbonate apatite (CO 3 Ap) blocks have attracted considerable attention as an artificial bone substitute material because CO 3 Ap is a component of and shares properties with bone, including high osteoconductivity and replacement by bone similar to autografts. In this study, we fabricated an interconnected porous CO 3 Ap block using α-tricalcium phosphate (TCP) spheres and evaluated the tissue response to this material in a rabbit tibial bone defect model. Interconnected porous α-TCP, the precursor of interconnected porous CO 3 Ap, could not be fabricated directly by sintering α-TCP spheres. It was therefore made via a setting reaction with α-TCP spheres, yielding interconnected porous calcium-deficient hydroxyapatite that was subjected to heat treatment. Immersing the interconnected porous α-TCP in Na-CO 3 -PO 4 solution produced CO 3 Ap, which retained the interconnected porous structure after the dissolution-precipitation reaction. The diametral tensile strength and porosity of the porous CO 3 Ap were 1.8 ± 0.4 MPa and 55% ± 3.2%, respectively. Both porous and dense (control) CO 3 Ap showed excellent tissue response and good osteoconductivity. At 4 weeks after surgery, approximately 15% ± 4.9% of the tibial bone defect was filled with new bone when reconstruction was performed using porous CO 3 Ap; this amount was five times greater than that obtained with dense CO 3 Ap. At 12 weeks after surgery, for porous CO 3 Ap, approximately 47% of the defect was filled with new bone as compared to 16% for dense CO 3 Ap. Thus, the interconnected porous CO 3 Ap block is a promising artificial bone substitute material for the treatment of bone defects caused by large fractures or bone tumor resection. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2018. © 2018 Wiley Periodicals, Inc.

Surface and interface investigation of aluminosilicate biomaterial by the “in vivo” experiments

NASA Astrophysics Data System (ADS)

Oudadesse, H.; Derrien, A. C.; Martin, S.; Chaair, H.; Cathelineau, G.

2008-11-01

Porous mixtures of aluminosilicate/calcium phosphate have been studied for biomaterials applications. Aluminosilicates formed with an inorganic polymeric constitution present amorphous zeolites because of their 3D network structure and present the ability to link to bone matrix. Amorphous geopolymers of the potassium-poly(sialate)-nanopolymer type were synthesised at low temperature and studied for their use as potential biomaterials. They were mixed with 13% weight of calcium phosphate like biphasic hydroxyapatite and β-tricalcium phosphate. In this study, " in vivo" experiments were monitored to evaluate the biocompatibility, the surface and the interface behaviour of these composites when used as bone implants. Moreover, it has been demonstrated using histological and physicochemical studies that the developed materials exhibited a remarkable bone bonding when implanted in a rabbit's thighbone for a period of 1 month. The easy synthesis conditions (low temperature) of this composite and the fast intimate links with bone constitute an improvement of synthetic bone graft biomaterial.

A Simplified Whole-Organ CT Perfusion Technique with Biphasic Acquisition: Preliminary Investigation of Accuracy and Protocol Feasibility in Kidneys.

PubMed

Yuan, XiaoDong; Zhang, Jing; Quan, ChangBin; Tian, Yuan; Li, Hong; Ao, GuoKun

2016-04-01

To determine the feasibility and accuracy of a protocol for calculating whole-organ renal perfusion (renal blood flow [RBF]) and regional perfusion on the basis of biphasic computed tomography (CT), with concurrent dynamic contrast material-enhanced (DCE) CT perfusion serving as the reference standard. This prospective study was approved by the institutional review board, and written informed consent was obtained from all patients. Biphasic CT of the kidneys, including precontrast and arterial phase imaging, was integrated with a first-pass dynamic volume CT protocol and performed and analyzed in 23 patients suspected of having renal artery stenosis. The perfusion value derived from biphasic CT was calculated as CT number enhancement divided by the area under the arterial input function and compared with the DCE CT perfusion data by using the paired t test, correlation analysis, and Bland-Altman plots. Correlation analysis was made between the RBF and the extent of renal artery stenosis. All postprocessing was independently performed by two observers and then averaged as the final result. Mean ± standard deviation biphasic and DCE CT perfusion data for RBF were 425.62 mL/min ± 124.74 and 419.81 mL/min ± 121.13, respectively (P = .53), and for regional perfusion they were 271.15 mL/min per 100 mL ± 82.21 and 266.33 mL/min per 100 mL ± 74.40, respectively (P = .31). Good correlation and agreement were shown between biphasic and DCE CT perfusion for RBF (r = 0.93; ±10% variation from mean perfusion data [P < .001]) and for regional perfusion (r = 0.90; ±13% variation from mean perfusion data [P < .001]). The extent of renal artery stenosis was negatively correlated with RBF with biphasic CT perfusion (r = -0.81, P = .012). Biphasic CT perfusion is clinically feasible and provides perfusion data comparable to DCE CT perfusion data at both global and regional levels in the kidney. Online supplemental material is available for this article.

Hexamethyldisilazane Removal with Mesoporous Materials Prepared from Calcium Fluoride Sludge.

PubMed

Kao, Ching-Yang; Lin, Min-Fa; Nguyen, Nhat-Thien; Tsai, Hsiao-Hsin; Chang, Luh-Maan; Chen, Po-Han; Chang, Chang-Tang

2018-05-01

A large amount of calcium fluoride sludge is generated by the semiconductor industry every year. It also requires a high amount of fuel consumption using rotor concentrators and thermal oxidizers to treat VOCs. The mesoporous adsorbent prepared by calcium fluoride sludge was used for VOCs treatment. The semiconductor industry employs HMDS to promote the adhesion of photo-resistant material to oxide(s) due to the formation of silicon dioxide, which blocks porous adsorbents. The adsorption of HMDS (Hexamethyldisiloxane) was tested with mesoporous silica materials synthesized from calcium fluoride (CF-MCM). The resulting samples were characterized by XRD, XRF, FTIR, N2-adsorption-desorption techniques. The prepared samples possessed high specific surface area, large pore volume and large pore diameter. The crystal patterns of CF-MCM were similar with Mobil composite matter (MCM-41) from TEM image. The adsorption capacity of HMDS with CF-MCM was 40 and 80 mg g-1, respectively, under 100 and 500 ppm HMDS. The effects of operation parameters, such as contact time and mixture concentration, on the performance of CF-MCM were also discussed in this study.

Fast pressure jumps can perturb calcium and magnesium binding to troponin C F29W.

PubMed

Pearson, David S; Swartz, Darl R; Geeves, Michael A

2008-11-18

We have used rapid pressure jump and stopped-flow fluorometry to investigate calcium and magnesium binding to F29W chicken skeletal troponin C. Increased pressure perturbed calcium binding to the N-terminal sites in the presence and absence of magnesium and provided an estimate for the volume change upon calcium binding (-12 mL/mol). We observed a biphasic response to a pressure change which was characterized by fast and slow reciprocal relaxation times of the order 1000/s and 100/s. Between pCa 8-5.4 and at troponin C concentrations of 8-28 muM, the slow relaxation times were invariant, indicating that a protein isomerization was rate-limiting. The fast event was only detected over a very narrow pCa range (5.6-5.4). We have devised a model based on a Monod-Wyman-Changeux cooperative mechanism with volume changes of -9 and +6 mL/mol for the calcium binding to the regulatory sites and closed to open protein isomerization steps, respectively. In the absence of magnesium, we discovered that calcium binding to the C-terminal sites could be detected, despite their position distal to the calcium-sensitive tryptophan, with a volume change of +25 mL/mol. We used this novel observation to measure competitive magnesium binding to the C-terminal sites and deduced an affinity in the range 200-300 muM (and a volume change of +35 mL/mol). This affinity is an order of magnitude tighter than equilibrium fluorescence data suggest based on a model of direct competitive binding. Magnesium thus indirectly modulates binding to the N-terminal sites, which may act as a fine-tuning mechanism in vivo.

Fast Pressure Jumps Can Perturb Calcium and Magnesium Binding to Troponin C F29W

PubMed Central

Pearson, David S.; Swartz, Darl R.; Geeves, Michael A.

2009-01-01

We have used rapid pressure jump and stopped-flow fluorimetry to investigate calcium and magnesium binding to F29W chicken skeletal troponin C. Increased pressure perturbed calcium binding to the N-terminal sites in the presence and absence of magnesium and provided an estimate for the volume change upon calcium binding (-12 mL.mol-1). We observed a biphasic response to a pressure change which was characterized by fast and slow reciprocal relaxation times of the order 1000 s-1 and 100 s-1. Between pCa 8-5.4 and at troponin C concentrations of 8-28 μM, the slow relaxation times were invariant indicating that a protein isomerization was rate-limiting. The fast event was only detected over a very narrow pCa range (5.6-5.4). We have devised a model based on a Monod-Wyman-Changeux cooperative mechanism with volume changes of -9 and +6 mL/mol for the calcium binding to the regulatory sites and closed to open protein isomerization steps respectively. In the absence of magnesium, we discovered that calcium binding to the C-terminal sites could be detected, despite their position distal to the calcium sensitive tryptophan, with a volume change of +25 mL/mol. We used this novel observation to measure competitive magnesium binding to the C-terminal sites and deduced an affinity in the range 200 - 300 μM (and a volume change of +35 mL/mol). This affinity is an order of magnitude tighter than equilibrium fluorescence data suggest based on a model of direct competitive binding. Magnesium thus indirectly modulates binding to the N-terminal sites, which may act as a fine-tuning mechanism in vivo. PMID:18942859

Electromigration and Deposition of Micro-Scale Calcium Carbonate Structures with Controlled Morphology and Polymorphism

DTIC Science & Technology

2013-04-01

precipitation of calcium carbonate in structured templates including microporous polycarbonate membranes and polyethylene foams. Para- meters...polyethylene foam). Microporous polycarbonate membranes and Medium-Density PolyEthylene (MDPE) foam specimens were used as the porous organic...voids in hardened concrete. DOI:10.1520/C624-06. West Conshohocken, PA: ASTM International . www.astm.org. Bersa, L., and M. Liu. 2007. A review on

Aqueous biphasic plutonium oxide extraction process with pH and particle control

DOEpatents

Chaiko, D.J.; Mensah-Biney, R.

1997-04-29

A method is described for simultaneously partitioning a metal oxide and silica from a material containing silica and the metal oxide, using a biphasic aqueous medium having immiscible salt and polymer phases. 2 figs.

Learning new meanings for known words: Biphasic effects of prior knowledge.

PubMed

Fang, Xiaoping; Perfetti, Charles; Stafura, Joseph

2017-01-01

In acquiring word meanings, learners are often confronted by a single word form that is mapped to two or more meanings. For example, long after how to roller-"skate", one may learn that "skate" is also a kind of fish. Such learning of new meanings for familiar words involves two potentially contrasting processes, relative to new form-new meaning learning: 1) Form-based familiarity may facilitate learning a new meaning, and 2) meaning-based interference may inhibit learning a new meaning. We examined these two processes by having native English speakers learn new, unrelated meanings for familiar (high frequency) and less familiar (low frequency) English words, as well as for unfamiliar (novel or pseudo-) words. Tracking learning with cued-recall tasks at several points during learning revealed a biphasic pattern: higher learning rates and greater learning efficiency for familiar words relative to novel words early in learning and a reversal of this pattern later in learning. Following learning, interference from original meanings for familiar words was detected in a semantic relatedness judgment task. Additionally, lexical access to familiar words with new meanings became faster compared to their exposure controls, but no such effect occurred for less familiar words. Overall, the results suggest a biphasic pattern of facilitating and interfering processes: Familiar word forms facilitate learning earlier, while interference from original meanings becomes more influential later. This biphasic pattern reflects the co-activation of new and old meanings during learning, a process that may play a role in lexicalization of new meanings.

Learning new meanings for known words: Biphasic effects of prior knowledge

PubMed Central

Fang, Xiaoping; Perfetti, Charles; Stafura, Joseph

2017-01-01

In acquiring word meanings, learners are often confronted by a single word form that is mapped to two or more meanings. For example, long after how to roller-“skate”, one may learn that “skate” is also a kind of fish. Such learning of new meanings for familiar words involves two potentially contrasting processes, relative to new form-new meaning learning: 1) Form-based familiarity may facilitate learning a new meaning, and 2) meaning-based interference may inhibit learning a new meaning. We examined these two processes by having native English speakers learn new, unrelated meanings for familiar (high frequency) and less familiar (low frequency) English words, as well as for unfamiliar (novel or pseudo-) words. Tracking learning with cued-recall tasks at several points during learning revealed a biphasic pattern: higher learning rates and greater learning efficiency for familiar words relative to novel words early in learning and a reversal of this pattern later in learning. Following learning, interference from original meanings for familiar words was detected in a semantic relatedness judgment task. Additionally, lexical access to familiar words with new meanings became faster compared to their exposure controls, but no such effect occurred for less familiar words. Overall, the results suggest a biphasic pattern of facilitating and interfering processes: Familiar word forms facilitate learning earlier, while interference from original meanings becomes more influential later. This biphasic pattern reflects the co-activation of new and old meanings during learning, a process that may play a role in lexicalization of new meanings. PMID:29399593

A case of mumps-related acute encephalopathy with biphasic seizures and late reduced diffusion.

PubMed

Hazama, Kyoko; Shiihara, Takashi; Tsukagoshi, Hiroyuki; Hasegawa, Shunji; Dowa, Yuri; Watanabe, Mio

2017-10-01

Mumps is a common childhood viral disease characterized by fever and swelling of the parotid gland. The prognosis is generally good, although some complications, such as encephalitis (0.1%), exist. Acute encephalopathy with biphasic seizures and late reduced diffusion is the most common type of acute encephalopathy. However, this type of encephalopathy has not been reported in association with mumps infection. A previously healthy 3-year-old Japanese boy had a brief convulsion after fever for 3days, and then had conscious disturbance and parotitis. After several days, he had a second brief convulsion and was admitted. Increased serum amylase levels and presence of anti-mumps immunoglobulin M antibody confirmed mumps parotitis. The patient had another brief seizure later the day of admission. He did not have status or cluster seizures, although the biphasic nature of his seizures, conscious disturbance between the seizures, no pleocytosis in cerebrospinal fluid, and brain magnetic resonance images were consistent with acute encephalopathy with biphasic seizures and late reduced diffusion. In Japan, the mumps vaccine is not administered as a part of routine immunizations. It thus has low coverage (30-40%), and as a result, mumps infections are still common. However, this is the first case of mumps-related acute encephalopathy with biphasic seizures and late reduced diffusion. This case may be representative of only a minority of patients with mumps-associated central nervous system involvement. Nevertheless, this diagnostic possibility may be considered. In order to prevent mumps-related complications, routine mumps vaccination might be warranted. Copyright © 2017 The Japanese Society of Child Neurology. Published by Elsevier B.V. All rights reserved.

Ikaite pseudomorphs in the Zaire deep-sea fan: An intermediate between calcite and porous calcite

NASA Astrophysics Data System (ADS)

Jansen, J. H. F.; Woensdregt, C. F.; Kooistra, M. J.; van der Gaast, S. J.

1987-03-01

Translucent brown aggregates of calcium-carbonate crystals have been found in cores from the Zaire deep-sea fan (west equatorial Africa). The aggregates are well preserved but very friable. Upon storage they become yellowish white and cloudy and release water. Chemical, mineralogical (XRD), petrographical, crystal-morphological, and stable-isotope data demonstrate that the crystals have passed through three phases: (1) an authigenic carbonate phase, probably calcium carbonate, which is represented by the external habit of the present crystals; (2) a translucent brown ikaite phase (CaCO3·6H2O), unstable at temperatures above 5 °C; and (3) a phase consisting of calcite microcrystals that are poorly cemented and form a porous mass within the crystal form of the morphologically unchanged first phase. The transformation from the first phase into ikaite was probably a kinetic replacement. The transformation from ikaite into the third phase occurred because of storage at room temperature. The presence of ikaite is indicative of a low-temperature, anaerobic, organic-carbon-rich marine environment. Ikaite is probably the precursor of a great number of porous calcite pseudomorphs, and possibly also of many marine authigenic microcrystalline carbonate nodules.

Biphasic Effects of Alcohol as a Function of Circadian Phase

PubMed Central

Van Reen, Eliza; Rupp, Tracy L.; Acebo, Christine; Seifer, Ronald; Carskadon, Mary A.

2013-01-01

Study Objectives: To assess how alcohol affects multiple sleep latency tests (MSLT) and subjective measures of stimulation/sedation when alcohol is given at different circadian phases. Participants: Twenty-seven healthy young adults (age 21-26 yr) were studied. Design: Double-blind placebo and alcohol (vodka tonic targeting 0.05 g% concentration) beverages were each administered three times during the 20-h forced desynchrony protocol. Sleep latency tests and Biphasic Effects of Alcohol Scale (BAES) were administered on each forced desynchrony day. The outcome variables for this study include sleep onset latency (SOL) and stimulation and sedation value (from the BAES). Each outcome variable was associated with the ascending or descending limb of the breath alcohol concentration (BrAC) curve and assigned a circadian phase within a 90° bin. Measurements and Results: BrAC confirmed targeted maximal levels. Only outcome variables associated with the ascending and descending limb of the alcohol curve were analyzed for this article. Alcohol administered at a circadian time associated with greatest sleepiness showed longer SOL compared with placebo when measured on the ascending limb of the BrAC curve. We also found longer SOL with alcohol on the ascending limb of the BrAC curve in a circadian bin that favors greatest alertness. We observed shorter SOLs on the descending limb of the BrAC curve, but with no circadian phase interaction. The subjective data were partially consistent with the objective data. Conclusions: The physiologic findings in this study support the biphasic stimulating and sedating properties of alcohol, but limit the effect to specific circadian times. Citation: Van Reen E; Rupp TL; Acebo C; Seifer R; Carskadon MA. Biphasic effects of alcohol as a function of circadian phase. SLEEP 2013;36(1):137-145. PMID:23288980

Attenuated adult biphasic shocks for prolonged pediatric ventricular fibrillation: support for pediatric automated defibrillators.

PubMed

Berg, Robert A

2004-09-01

To evaluate published data regarding the treatment of prolonged pediatric defibrillation, with special emphasis on the use of attenuated adult biphasic shocks for pediatric defibrillation. Review relevant human and animal literature. Rhythm analysis algorithms from two manufacturers of automated external defibrillators can accurately distinguish shockable from nonshockable rhythms in children. Theoretical considerations and transthoracic impedance data from animals and children suggest that pediatric defibrillation doses should not necessarily vary in a simple weight-based manner. Two piglet studies have established that an attenuated adult biphasic dosage can be successfully used for 3.5- to 24-kg animals in ventricular fibrillation. One study established that the attenuated adult biphasic dosage was at least as safe and effective as the standard monophasic weight-based dosing. This review supports the American Heart Association's new guidelines for pediatric automated external defibrillator usage: "Automated external defibrillators may be used for children 1 to 8 yrs of age who have no signs of circulation. Ideally the device should deliver a pediatric dose. The arrhythmia detection system used in the device should demonstrate high specificity for pediatric shockable rhythms, i.e., it will not recommend delivery of a shock for nonshockable rhythms."

A biphasic dialytic strategy for the treatment of neonatal hyperammonemia

PubMed Central

Avasare, Sonal; Tsai, Eileen; Yadin, Ora; Zaritsky, Joshua

2018-01-01

Background Neonates with inborn errors of metabolism (IEM) often develop hyperammonemia which, if not corrected quickly, may result in poor neurologic outcomes. As pharmacologic therapy cannot rapidly lower ammonia levels, dialysis is frequently required. Both hemodialysis (HD) and standard-dose continuous renal replacement therapy (CRRT) are effective; however, HD may be followed by post-dialytic ammonia rebound, and standard-dose CRRT may not effect a rapid enough decrease in ammonia levels. Case-Diagnosis/Treatment We present two cases of IEM-associated neonatal hyperammonemia in which we employed a biphasic, high-dose CRRT treatment strategy, initially using dialysate flow rates of 5,000 mL/h (approximately 40,000 mL/h/1.73 m2) in order to rapidly decrease ammonia levels, then decreasing the dialysate flow rates to 500 mL/h (approximately 4,000 mL/h/1.73 m2) in order to prevent ammonia rebound. Conclusions This biphasic dialytic treatment strategy for neonatal hyperammonemia effected rapid ammonia reduction without rebound and accomplished during a single dialysis run without equipment changes. PMID:24122260

Fortifying the Bone-Implant Interface Part 1: An In Vitro Evaluation of 3D-Printed and TPS Porous Surfaces

PubMed Central

Lindsey, Derek P.; Bahney, Chelsea S.; Woods, Shane A.; Wolfe, Mark L.; Yerby, Scott A.

2017-01-01

Background An aging society and concomitant rise in the incidence of impaired bone health have led to the need for advanced osteoconductive spinal implant surfaces that promote greater biological fixation (e.g. for interbody fusion cages, sacroiliac joint fusion implants, and artificial disc replacements). Additive manufacturing, i.e. 3D-printing, may improve bone integration by generating biomimetic spinal implant surfaces that mimic bone morphology. Such surfaces may foster an enhanced cellular response compared to traditional implant surfacing processes. Methods This study investigated the response of human osteoblasts to additive manufactured (AM) trabecular-like titanium implant surfaces compared to traditionally machined base material with titanium plasma spray (TPS) coated surfaces, with and without a nanocrystalline hydroxyapatite (HA) coating. For TPS-coated discs, wrought Ti6Al4V ELI was machined and TPS-coating was applied. For AM discs, Ti6Al4V ELI powder was 3D-printed to form a solid base and trabecular-like porous surface. The HA-coating was applied via a precipitation dip-spin method. Surface porosity, pore size, thickness, and hydrophilicity were characterized. Initial cell attachment, proliferation, alkaline phosphatase (ALP) activity, and calcium production of hFOB cells (n=5 per group) were measured. Results Cells on AM discs exhibited expedited proliferative activity. While there were no differences in mean ALP expression and calcium production between TPS and AM discs, calcium production on the AM discs trended 48% higher than on TPS discs (p=0.07). Overall, HA-coating did not further enhance results compared to uncoated TPS and AM discs. Conclusions Results demonstrate that additive manufacturing allows for controlled trabecular-like surfaces that promote earlier cell proliferation and trends toward higher calcium production than TPS coating. Results further showed that nanocrystalline HA may not provide an advantage on porous titanium

Fortifying the Bone-Implant Interface Part 1: An In Vitro Evaluation of 3D-Printed and TPS Porous Surfaces.

PubMed

MacBarb, Regina F; Lindsey, Derek P; Bahney, Chelsea S; Woods, Shane A; Wolfe, Mark L; Yerby, Scott A

2017-01-01

An aging society and concomitant rise in the incidence of impaired bone health have led to the need for advanced osteoconductive spinal implant surfaces that promote greater biological fixation ( e.g. for interbody fusion cages, sacroiliac joint fusion implants, and artificial disc replacements). Additive manufacturing, i.e. 3D-printing, may improve bone integration by generating biomimetic spinal implant surfaces that mimic bone morphology. Such surfaces may foster an enhanced cellular response compared to traditional implant surfacing processes. This study investigated the response of human osteoblasts to additive manufactured (AM) trabecular-like titanium implant surfaces compared to traditionally machined base material with titanium plasma spray (TPS) coated surfaces, with and without a nanocrystalline hydroxyapatite (HA) coating. For TPS-coated discs, wrought Ti6Al4V ELI was machined and TPS-coating was applied. For AM discs, Ti6Al4V ELI powder was 3D-printed to form a solid base and trabecular-like porous surface. The HA-coating was applied via a precipitation dip-spin method. Surface porosity, pore size, thickness, and hydrophilicity were characterized. Initial cell attachment, proliferation, alkaline phosphatase (ALP) activity, and calcium production of hFOB cells ( n =5 per group) were measured. Cells on AM discs exhibited expedited proliferative activity. While there were no differences in mean ALP expression and calcium production between TPS and AM discs, calcium production on the AM discs trended 48% higher than on TPS discs ( p =0.07). Overall, HA-coating did not further enhance results compared to uncoated TPS and AM discs. Results demonstrate that additive manufacturing allows for controlled trabecular-like surfaces that promote earlier cell proliferation and trends toward higher calcium production than TPS coating. Results further showed that nanocrystalline HA may not provide an advantage on porous titanium surfaces. Additive manufactured porous

β-TCP porous pellets as an orthopaedic drug delivery system: ibuprofen/carrier physicochemical interactions

NASA Astrophysics Data System (ADS)

Baradari, Hiba; Damia, Chantal; Dutreih-Colas, Maggy; Champion, Eric; Chulia, Dominique; Viana, Marylène

2011-10-01

Calcium phosphate bone substitute materials can be loaded with active substances for in situ, targeted drug administration. In this study, porous β-TCP pellets were investigated as an anti-inflammatory drug carrier. Porous β-TCP pellets were impregnated with an ethanolic solution of ibuprofen. The effects of contact time and concentration of ibuprofen solution on drug adsorption were studied. The ibuprofen adsorption equilibrium time was found to be one hour. The adsorption isotherms fitted to the Freundlich model, suggesting that the interaction between ibuprofen and β-TCP is weak. The physicochemical characterizations of loaded pellets confirmed that the reversible physisorption of ibuprofen on β-TCP pellets is due to Van der Waals forces, and this property was associated with the 100% ibuprofen release.

Efficient asymmetric hydrolysis of styrene oxide catalyzed by Mung bean epoxide hydrolases in ionic liquid-based biphasic systems.

PubMed

Chen, Wen-Jing; Lou, Wen-Yong; Zong, Min-Hua

2012-07-01

The asymmetric hydrolysis of styrene oxide to (R)-1-phenyl-1,2-ethanediol using Mung bean epoxide hydrolases was, for the first time, successfully conducted in an ionic liquid (IL)-containing biphasic system. Compared to aqueous monophasic system, IL-based biphasic systems could not only dissolve the substrate, but also effectively inhibit the non-enzymatic hydrolysis, and therefore markedly improve the reaction efficiency. Of all the tested ILs, the best results were observed in the biphasic system containing C(4)MIM·PF(6), which exhibited good biocompatibility with the enzyme and was an excellent solvent for the substrate. In the C(4)MIM·PF(6)/buffer biphasic system, it was found that the optimal volume ratio of IL to buffer, reaction temperature, buffer pH and substrate concentration were 1/6, 35°C, 6.5 and 100 mM, respectively, under which the initial reaction rate, the yield and the product e.e. were 18.4 mM/h, 49.4% and 97.0%. The biocatalytic process was shown to be feasible on a 500-mL preparative scale. Copyright © 2011 Elsevier Ltd. All rights reserved.

Non-conventional solvents in liquid phase microextraction and aqueous biphasic systems.

PubMed

An, Jiwoo; Trujillo-Rodríguez, María J; Pino, Verónica; Anderson, Jared L

2017-06-02

The development of rapid, convenient, and high throughput sample preparation approaches such as liquid phase microextraction techniques have been continuously developed over the last decade. More recently, significant attention has been given to the replacement of conventional organic solvents used in liquid phase microextraction techniques in order to reduce toxic waste and to improve selectivity and/or extraction efficiency. With these objectives, non-conventional solvents have been explored in liquid phase microextraction and aqueous biphasic systems. The utilized non-conventional solvents include ionic liquids, magnetic ionic liquids, and deep eutectic solvents. They have been widely used as extraction solvents or additives in various liquid phase microextraction modes including dispersive liquid-liquid microextraction, single-drop microextraction, hollow fiber-liquid phase microextraction, as well as in aqueous biphasic systems. This review provides an overview into the use of non-conventional solvents in these microextraction techniques in the past 5 years (2012-2016). Analytical applications of the techniques are also discussed. Copyright © 2017 Elsevier B.V. All rights reserved.

Biphasic magnetic nanoparticles-nanovesicle hybrids for chemotherapy and self-controlled hyperthermia.

PubMed

Gogoi, Manashjit; Sarma, Haladhar D; Bahadur, Dhirendra; Banerjee, Rinti

2014-05-01

The aim was to develop magnetic nanovesicles for chemotherapy and self-controlled hyperthermia that prevent overheating of tissues. Magnetic nanovesicles containing paclitaxel and a dextran-coated biphasic suspension of La0.75Sr0.25MnO3 and Fe3O4 nanoparticles (magnetic nanoparticles) were developed. Encapsulation efficiencies of magnetic nanoparticles and paclitaxel were 67 ± 5 and 83 ± 3%, respectively. Sequential release performed at 37°C for 1 h followed by 44°C for another 1 h (as expected for intratumoral injection), showed a cumulative release of 6.6% (109.6 µg), which was above the IC50 of the drug. In an alternating current magnetic field, the temperature remained controlled at 44°C and a synergistic cytotoxicity of paclitaxel and hyperthermia was observed in MCF-7 cells. Magnetic nanovesicles containing biphasic suspensions La0.75Sr0.25MnO3 and Fe3O4 nanoparticles encapsulating paclitaxel have potential for combined self-controlled hyperthermia and chemotherapy.

Separation and recovery of food coloring dyes using aqueous biphasic extraction chromatographic resins.

PubMed

Huddleston, J G; Willauer, H D; Boaz, K R; Rogers, R D

1998-06-26

Aqueous biphasic systems (ABS) and aqueous biphasic extraction chromatographic (ABEC) resins are currently under investigation for their utility in the removal of color from textile plant wastes. The structures of several widely used food colorings, suggest that these dyes would also be retained on the resins. In work currently in progress, we have begun to investigate the retention and resolution of several common food colorings including indigo carmine, amaranth, carminic acid. erythrosin B, tartrazine and quinoline yellow. The relationship between the uptake of these dyes on ABEC resins in terms of the binding strengths and capacities of the resins and their partitioning behavior in ABS is illustrated. Some possible theoretical and practical approaches to the prediction of the partitioning and retention behavior is discussed.

CORRELATION OF A BIPHASIC METABOLIC RESPONSE WITH A BIPHASIC RESPONSE IN RESISTANCE TO TUBERCULOSIS IN RABBITS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Allison, M.J.; Zappasodi, P.; Lurie, M.B.

Peritoneal exudate mononuclear cells obtained from BCG-vaccinated rabbits showed higher utilization of succinate, glycerophosphate, beta - hydroxybutyrate, and glycerol than cells from control animals. No differences in utilization of the following substrates were noted: lactate, glucose-6-phosphate, malate, isocitrate, alpha -ketoglutarate, and glutamic acid. A second, later stage of elevated metabolic activity was associated with heightened resistance to infection. When rabbits which had been irradiated with 400 r 2 years previously were vaccinated with BCG, they failed to respond as shown by their lack of resistance to infection and failure of their mononuclear cells to show the biphasic metabolic stimulation. Themore » results demonstrate the close relation between the metabolic capabilities of reticuloendothelial cells and their resistance to tuberculosis. (H.H.D.)« less

Low-concentration hydrogen peroxide can upregulate keratinocyte intracellular calcium and PAR-2 expression in a human keratinocyte-melanocyte co-culture system.

PubMed

Li, Jian; Tang, Lu-Yan; Fu, Wen-Wen; Yuan, Jin; Sheng, You-Yu; Yang, Qin-Ping

2016-12-01

Hydrogen peroxide (H 2 O 2 ) may have a biphasic effect on melanin synthesis and melanosome transfer. High H 2 O 2 concentrations are involved in impaired melanosome transfer in vitiligo. However, low H 2 O 2 concentration promotes the beneficial proliferation and migration of melanocytes. The aim of this study was to explore low H 2 O 2 and its mechanism in melanosome transfer, protease-activated receptor-2 (PAR-2) expression and calcium balance. Melanosomes were fluorescein-labeled for clear visualization of their transfer. The expression of protease-activated receptor-2 (PAR-2) in keratinocytes was determined by western blot analysis. Flow cytometry was employed to evaluate the effects of H 2 O 2 on calcium levels in keratinocytes. Fluorescence microscopy showed the upregulation of melanosome transfer into keratinocytes following 0.3 mM H 2 O 2 treatment in the co-cultures rather than in the untreated control groups, which was associated with higher expression of PAR-2 protein and increased calcium concentration. The addition of a PAR-2 antagonist inhibited the positive activity of H 2 O 2 and calcium flow in keratinocytes. When calcium flow was blocked by a calcium chelator, the addition of H 2 O 2 did not increase the PAR-2 expression level in keratinocytes, therefore, inhibiting dendrite formation and melanosome transfer. Low H 2 O 2 concentration promotes melanosome transfer with increased PAR-2 expression level and calcium concentration in keratinocytes. In addition, the interaction between melanocytes and keratinocytes is more beneficial to enhance calcium levels in keratinocytes which mediate melanin transfer. Moreover, low H 2 O 2 concentration promotes dendrite formation, in which extracellular calcium and Par-2 were involved.

Rapid hydrothermal flow synthesis and characterisation of carbonate- and silicate-substituted calcium phosphates

PubMed Central

Knowles, Jonathan C; Rehman, Ihtesham; Darr, Jawwad A

2013-01-01

A range of crystalline and nano-sized carbonate- and silicate-substituted hydroxyapatite has been successfully produced by using continuous hydrothermal flow synthesis technology. Ion-substituted calcium phosphates are better candidates for bone replacement applications (due to improved bioactivity) as compared to phase-pure hydroxyapatite. Urea was used as a carbonate source for synthesising phase pure carbonated hydroxyapatite (CO3-HA) with ≈5 wt% substituted carbonate content (sample 7.5CO3-HA) and it was found that a further increase in urea concentration in solution resulted in biphasic mixtures of carbonate-substituted hydroxyapatite and calcium carbonate. Transmission electron microscopy images revealed that the particle size of hydroxyapatite decreased with increasing urea concentration. Energy-dispersive X-ray spectroscopy result revealed a calcium deficient apatite with Ca:P molar ratio of 1.45 (±0.04) in sample 7.5CO3-HA. For silicate-substituted hydroxyapatite (SiO4-HA) silicon acetate was used as a silicate ion source. It was observed that a substitution threshold of ∼1.1 wt% exists for synthesis of SiO4-HA in the continuous hydrothermal flow synthesis system, which could be due to the decreasing yields with progressive increase in silicon acetate concentration. All the as-precipitated powders (without any additional heat treatments) were analysed using techniques including Transmission electron microscopy, X-ray powder diffraction, Differential scanning calorimetry, Thermogravimetric analysis, Raman spectroscopy and Fourier transform infrared spectroscopy. PMID:22983020

Effects of osmotic swelling on voltage-gated calcium channel currents in rat anterior pituitary cells.

PubMed

Ben-Tabou De-Leon, Shlomo; Blotnick, Edna; Nussinovitch, Itzhak

2003-10-01

Decrease in extracellular osmolarity ([Os]e) results in stimulation of hormone secretion from pituitary cells. Different mechanisms can account for this stimulation of hormone secretion. In this study we examined the possibility that hyposmolarity directly modulates voltage-gated calcium influx in pituitary cells. The effects of hyposmolarity on L-type (IL) and T-type (IT) calcium currents in pituitary cells were investigated by using two hyposmotic stimuli, moderate (18-22% decrease in [Os]e) and strong (31-32% decrease in [Os]e). Exposure to moderate hyposmotic stimuli resulted in three response types in IL (a decrease, a biphasic effect, and an increase in IL) and in increase in IT. Exposure to strong hyposmotic stimuli resulted only in increases in both IL and IT. Similarly, in intact pituitary cells (perforated patch method), exposure to either moderate or strong hyposmotic stimuli resulted only in increases in both IL and IT. Thus it appears that the main effect of decrease in [Os]e is increase in calcium channel currents. This increase was differential (IL were more sensitive than IT) and voltage independent. In addition, we show that these hyposmotic effects cannot be explained by activation of an anionic conductance or by an increase in cell membrane surface area. In conclusion, this study shows that hyposmotic swelling of pituitary cells can directly modulate voltage-gated calcium influx. This hyposmotic modulation of IL and IT may contribute to the previously reported hyposmotic stimulation of hormone secretion. The mechanisms underlying these hyposmotic effects and their possible physiological relevance are discussed.

Deriving sulfamethoxazole dissipation endpoints in pasture soils using first order and biphasic kinetic models.

PubMed

Srinivasan, Prakash; Sarmah, Ajit K; Rohan, Maheswaran

2014-08-01

Single first-order (SFO) kinetic model is often used to derive the dissipation endpoints of an organic chemical in soil. This model is used due to its simplicity and requirement by regulatory agencies. However, using the SFO model for all types of decay pattern could lead to under- or overestimation of dissipation endpoints when the deviation from first-order is significant. In this study the performance of three biphasic kinetic models - bi-exponential decay (BEXP), first-order double exponential decay (FODED), and first-order two-compartment (FOTC) models was evaluated using dissipation datasets of sulfamethoxazole (SMO) antibiotic in three different soils under varying concentration, depth, temperature, and sterile conditions. Corresponding 50% (DT50) and 90% (DT90) dissipation times for the antibiotics were numerically obtained and compared against those obtained using the SFO model. The fit of each model to the measured values was evaluated based on an array of statistical measures such as coefficient of determination (R(2)adj), root mean square error (RMSE), chi-square (χ(2)) test at 1% significance, Bayesian Information Criteria (BIC) and % model error. Box-whisker residual plots were also used to compare the performance of each model to the measured datasets. The antibiotic dissipation was successfully predicted by all four models. However, the nonlinear biphasic models improved the goodness-of-fit parameters for all datasets. Deviations from datasets were also often less evident with the biphasic models. The fits of FOTC and FODED models for SMO dissipation datasets were identical in most cases, and were found to be superior to the BEXP model. Among the biphasic models, the FOTC model was found to be the most suitable for obtaining the endpoints and could provide a mechanistic explanation for SMO dissipation in the soils. Copyright © 2014 Elsevier B.V. All rights reserved.

Sub-threshold depolarizing pre-pulses can enhance the efficiency of biphasic stimuli in transcutaneous neuromuscular electrical stimulation.

PubMed

Vargas Luna, Jose Luis; Mayr, Winfried; Cortés-Ramirez, Jorge-Armando

2018-06-09

There is multiple evidence in the literature that a sub-threshold pre-pulse, delivered immediately prior to an electrical stimulation pulse, can alter the activation threshold of nerve fibers and motor unit recruitment characteristics. So far, previously published works combined monophasic stimuli with sub-threshold depolarizing pre-pulses (DPPs) with inconsistent findings-in some studies, the DPPs decreased the activation threshold, while in others it was increased. This work aimed to evaluate the effect of DPPs during biphasic transcutaneous electrical stimulation and to study the possible mechanism underlying those differences. Sub-threshold DPPs between 0.5 and 15 ms immediately followed by biphasic or monophasic pulses were administered to the tibial nerve; the electrophysiological muscular responses (motor-wave, M-wave) were monitored via electromyogram (EMG) recording from the soleus muscle. The data show that, under the specific studied conditions, DPPs tend to lower the threshold for nerve fiber activation rather than elevating it. DPPs with the same polarity as the leading phase of biphasic stimuli are more effective to increase the sensitivity. This work assesses for the first time the effect of DPPs on biphasic pulses, which are required to achieve charge-balanced stimulation, and it provides guidance on the effect of polarity and intensity to take full advantage of this feature. Graphical abstract In this work, the effect of sub-threshold depolarizing pre-pulses (DPP) is investigated in a setup with transcutaneous electrical stimulation. We found that, within the tested 0-15 ms DPP duration range, the DPPs administered immediately before biphasic pulses proportionally increase the nerve excitability as visible in the M-waves recorded from the soleus muscle. Interestingly, these findings oppose published results, where DPPs, administered immediately before monophasic stimuli via implanted electrodes, led to decrease of nerve excitability.

Influence of bone morphogenetic protein and proportion of hydroxyapatite on new bone formation in biphasic calcium phosphate graft: two pilot studies in animal bony defect model.

PubMed

Yun, Pil-Young; Kim, Young-Kyun; Jeong, Kyung-In; Park, Ju-Cheol; Choi, Yeon-Jo

2014-12-01

The purpose of these two pilot studies using animal bony defect models was to evaluate the influence of bone morphogenetic protein (BMP) and proportion of hydroxyapatite (HA)/beta-tricalcium phosphate (β-TCP) in biphasic calcium phosphate (BCP) graft on new bone formation. In this study, four kinds of synthetic osteoconductive bone materials known for bone growth scaffold, OSTEON™II(HA:β-TCP 30:70), OSTEON™III (HA:β-TCP 20:80), OSTEON™II Collagen, and OSTEON™III Collagen, were prepared as BCP graft materials. In pilot study 1, three BCP materials (OSTEON™II, OSTEON™III, and OSTEON™II Collagen) were grafted in rabbit calvarial defects after impregnating in rhBMP-2. OSTEON™II without the rhBMP-2 impregnation was included in the study as the control. The amount of new bone was examined and measured histologically at 2, 4, and 8 weeks. In pilot study 2, four BCP materials (OSTEON™II, OSTEON™III, OSTEON™II Collagen, and OSTEON™III Collagen) were grafted in beagle dog mandibular defects after soaking in the rhBMP-2. The amount of total bone and new bone were measured three-dimensionally using microCT and healing process was examined histologically at 2, 4, and 8 weeks. In pilot study 1, rhBMP-2 impregnated groups showed more new bone formation than the rhBMP-2 free group. In pilot study 2, increased new bone formation was observed in time-dependent manner after graft of BCP and BCP-collagen (OSTEON™II, OSTEON™III, OSTEON™II Collagen, and OSTEON™III Collagen) impregnated with rhBMP-2. Also, BCP with a higher proportion of HA (30% HA) showed more favorable result in new bone formation and space maintenance, especially at the 8 weeks. From the results of the pilot studies, rhBMP-2 played positive roles in new bone formation and BCP could become a scaffold candidate for rhBMP-2 impregnation to induce new bone formation. Moreover, BCP with a higher proportion of HA (30% HA) could be considered more appropriate for rhBMP-2 carrier. Copyright

Mass dependence of calcium isotope fractionations in crown-ether resin chromatography.

PubMed

Fujii, Yasuhiko; Nomura, Masao; Kaneshiki, Tositaka; Sakuma, Yoichi; Suzuki, Tatsuya; Umehara, Saori; Kishimoto, Tadahumi

2010-06-01

Benzo 18-crown-6-ether resin was synthesised by the phenol condensation polymerisation process in porous silica beads, of which particle diameter was ca 60micro Calcium adsorption chromatography was performed with the synthesised resin packed in a glass column. The effluent was sampled in fractions, and the isotopic abundance ratios of (42)Ca, (43)Ca, (44)Ca, and (48)Ca against (40)Ca were measured by a thermo-ionisation mass spectrometer. The enrichment of heavier calcium isotopes was observed at the front boundary of calcium adsorption chromatogram. The mass dependence of mutual separation of calcium isotopes was analysed by using the three-isotope-plots method. The slopes of three-isotope-plots indicate the relative values of mutual separation coefficients for concerned isotopic pairs. The results have shown the normal mass dependence; isotope fractionation is proportional to the reduced mass difference, (M - M')/MM', where M and M' are masses of heavy and light isotope, respectively. The mass dependence clarifies that the isotope fractionations are originated from molecular vibration. The observed separation coefficient epsilon is 3.1x10(-3) for the pair of (40)Ca and (48)Ca. Productivity of enriched (48)Ca by crown-ether-resin was discussed as the function of the separation coefficient and the height equivalent to the theoretical plate.

Investigation of bone formation using calcium phosphate glass cement in beagle dogs

PubMed Central

Lee, Seung-Bum; Jung, Ui-Won; Choi, Youna; Jamiyandorj, Otgonbold; Kim, Chang-Sung; Lee, Yong-Keun; Chai, Jung-Kiu

2010-01-01

Purpose Among available biomaterials, bioceramics have drawn special interest due to their bioactivity and the possibility of tailoring their composition. The degradation rate and formulation of bioceramics can be altered to mimic the compositions of the mineral phase of bone. The aim of this study was to investigate the bone formation effect of amorphous calcium phosphate glass cement (CPGC) synthesized by a melting and quenching process. Methods In five male beagle dogs, 4 × 4 mm 1-wall intrabony defects were created bilaterally at the mesial or distal aspect of the mandibular second and fourth premolars. Each of the four defects was divided according to graft materials: CPGC with collagen membrane (CM), biphasic calcium phosphate (BCP) with CM, CM alone, or a surgical flap operation only. The dogs were sacrificed 8 weeks post-surgery, and block sections of the defects were collected for histologic and histometric analysis. Results There were significant differences in bone formation and cementum regeneration between the experimental and control groups. In particular, the CPGC and BCP groups showed greater bone formation than the CM and control groups. Conclusions In conclusion, CPGC was replaced rapidly with an abundant volume of new bone; CPGC also contributed slightly to regeneration of the periodontal apparatus. PMID:20607057

Anti-prelog reduction of prochiral carbonyl compounds by Oenococcus oeni in a biphasic system.

PubMed

Hu, Jian; Xu, Yan

2006-07-01

An aqueous-organic biphasic system was established and used with whole cells of Oenococcus oeni to reduce 2-octanone to (R)-2-octanol. The conversion reached 99% when the Tris/borate buffer was increased from 50 mM to 300 mM in the aqueous phase. In addition, the conversion increased as the log P value of the organic solvent changed from 0.5 to 6.6. Under optimized conditions, the conversion of (R)-2-octanol reached 99% from 0.5 M 2-octanone with an optical purity of 99% e.e. The biphasic system allows the anti-Prelog reduction of aliphatic and aromatic ketones to furnish (R)-configurated alcohols in high optical purity as well.

Development of porous lamellar poly(L-lactic acid) scaffolds by conventional injection molding process.

PubMed

Ghosh, Satyabrata; Viana, Júlio C; Reis, Rui L; Mano, João F

2008-07-01

A novel fabrication technique is proposed for the preparation of unidirectionally oriented, porous scaffolds by selective polymer leaching from lamellar structures created by conventional injection molding. The proof of the concept is implemented using a 50/50 wt.% poly(L-lactic acid)/poly(ethylene oxide) (PLLA/PEO) blend. With this composition, the PLLA and PEO blend is biphasic, containing a homogeneous PLLA/PEO phase and a PEO-rich phase. The two phases were structured using injection molding into well-defined alternating layers of homogeneous PLLA/PEO phase and PEO-rich phase. Leaching of water-soluble PEO from the PEO-rich phase produces macropores, and leaching of phase-separated PEO from the initially homogeneous PLLA/PEO phase produces micropores in the lamellae. Thus, scaffolds with a macroporous lamellar architecture with microporous walls can be produced. The lamellae are continuous along the flow direction, and a continuous lamellar thickness of less than 1 microm could be achieved. Porosities of 57-74% and pore sizes of around 50-100 microm can be obtained using this process. The tensile elastic moduli of the porous constructs were between 580 and 800 MPa. We propose that this organic-solvent-free method of preparing lamellar scaffolds with good mechanical properties, and the reproducibility associated with the injection molding technique, holds promise for a wide range of guided tissue engineering applications.

Mechanical properties of calcium phosphate scaffolds fabricated by robocasting.

PubMed

Miranda, Pedro; Pajares, Antonia; Saiz, Eduardo; Tomsia, Antoni P; Guiberteau, Fernando

2008-04-01

The mechanical behavior under compressive stresses of beta-tricalcium phosphate (beta-TCP) and hydroxyapatite (HA) scaffolds fabricated by direct-write assembly (robocasting) technique is analyzed. Concentrated colloidal inks prepared from beta-TCP and HA commercial powders were used to fabricate porous structures consisting of a 3-D tetragonal mesh of interpenetrating ceramic rods. The compressive strength and elastic modulus of these model scaffolds were determined by uniaxial testing to compare the relative performance of the selected materials. The effect of a 3-week immersion in simulated body fluid (SBF) on the strength of the scaffolds was also analyzed. The results are compared with those reported in the literature for calcium phosphate scaffolds and human bone. The robocast calcium phosphate scaffolds were found to exhibit excellent mechanical performances in terms of strength, especially the HA structures after SBF immersion, indicating a great potential of this type of scaffolds for use in load-bearing bone tissue engineering applications. Copyright 2007 Wiley Periodicals, Inc.

Optical performance of hybrid porous silicon-porous alumina multilayers

NASA Astrophysics Data System (ADS)

Cencha, L. G.; Antonio Hernández, C.; Forzani, L.; Urteaga, R.; Koropecki, R. R.

2018-05-01

In this work, we study the optical response of structures involving porous silicon and porous alumina in a multi-layered hybrid structure. We performed a rational design of the optimal sequence necessary to produce a high transmission and selective filter, with potential applications in chemical and biosensors. The combination of these porous materials can be used to exploit its distinguishing features, i.e., high transparency of alumina and high refractive index of porous silicon. We assembled hybrid microcavities with a central porous alumina layer between two porous silicon Bragg reflectors. In this way, we constructed a Fabry-Perot resonator with high reflectivity and low absorption that improves the quality of the filter compared to a microcavity built only with porous silicon or porous alumina. We explored a simpler design in which one of the Bragg reflectors is replaced by the aluminium that remains bound to the alumina after its fabrication. We theoretically explored the potential of the proposal and its limitations when considering the roughness of the layers. We found that the quality of a microcavity made entirely with porous silicon shows a limit in the visible range due to light absorption. This limitation is overcome in the hybrid scheme, with the roughness of the layers determining the ultimate quality. Q-factors of 220 are experimentally obtained for microcavities supported on aluminium, while Q-factors around 600 are reached for microcavities with double Bragg reflectors, centred at 560 nm. This represents a four-fold increase with respect to the optimal porous silicon microcavity at this wavelength.

Strontium Co-precipitation During Biomineralization of Calcite in Porous Media Using Differing Treatment Strategies

NASA Astrophysics Data System (ADS)

Lauchnor, E. G.; Schultz, L.; Mitchell, A.; Cunningham, A. B.; Gerlach, R.

2013-12-01

The process of ureolytically-induced calcium carbonate mineralization has been shown in laboratory studies to be effective in co-precipitation of heavy metals and radionuclides. During this process, the microbially catalyzed hydrolysis of urea increases alkalinity and pH, thus promoting CaCO3 precipitation in the presence of dissolved calcium. One proposed application of biomineralization includes the remediation of radionuclides such as strontium, which can be co-precipitated in situ within calcite. Strontium is of concern at several US DOE sites where it is a radioactive product of uranium fission and groundwater contaminant. Our research focuses on promoting attached bacteria, or biofilms, in subsurface environments where they serve as immobilized catalysts in biomineralization and can aide in co-precipitation of some contaminants. In this work, flat plate reactors with 1 mm etched flow channels designed to mimic a porous medium environment were used. Reactors were inoculated with the model ureolytic bacterium Sporosarcina pasteurii and addition of urea, calcium and strontium containing fluid was performed to induce biomineralization. Continuous flow and stopped-flow injection strategies were investigated to evaluate differences in strontium co-precipitation efficiency. During stopped-flow experiments, injection of cementation fluid containing urea, Ca2+ and Sr2+ was alternated with growth nutrients for stimulation of microbial activity. Control parameters such as urea and calcium concentration and injection flow rate are currently being varied to optimize rate and efficiency of strontium co-precipitation. Ureolytically induced calcite precipitation and strontium incorporation in the calcite was verified by chemical and mineralogical analyses, including X-ray diffraction and ICP-MS. Strontium co-precipitation efficiency was similar under different injection strategies. Alternating calcium-containing fluid with growth nutrients allowed for continued viability of

Electrophoretic deposition of porous CaO-MgO-SiO2 glass-ceramic coatings with B2O3 as additive on Ti-6Al-4V alloy.

PubMed

Zhang, Wei; Chen, Xianchun; Liao, Xiaoming; Huang, Zhongbing; Dan, Xiuli; Yin, Guangfu

2011-10-01

The sub-micron glass-ceramic powders in CaO-MgO-SiO(2) system with 10 wt% B(2)O(3) additive were synthesized by sol-gel process. Then bioactive porous CaO-MgO-SiO(2) glass-ceramic coatings on Ti-6Al-4V alloy substrates were fabricated using electrophoretic deposition (EPD) technique. After being calcined at 850°C, the above coatings with thickness of 10-150 μm were uniform and crack-free, possessing porous structure with sub-micron and micron size connected pores. Ethanol was employed as the most suitable solvent to prepare the suspension for EPD. The coating porous appearance and porosity distribution could be controlled by adjusting the suspension concentration, applied voltage and deposition time. The heat-treated coatings possessed high crystalline and was mainly composed of diopside, akermanite, merwinite, calcium silicate and calcium borate silicate. Bonelike apatite was formed on the coatings after 7 days of soaking in simulated body fluid (SBF). The bonding strength of the coatings was needed to be further improved.

Preparation and Evaluation of Solid Dispersion Tablets by a Simple and Manufacturable Wet Granulation Method Using Porous Calcium Silicate.

PubMed

Fujimoto, Yumi; Hirai, Nobuaki; Takatani-Nakase, Tomoka; Takahashi, Koichi

2016-01-01

The aim of this study was to prepare and evaluate solid dispersion tablets containing a poorly water-soluble drug using porous calcium silicate (PCS) by a wet granulation method. Nifedipine (NIF) was used as the model poorly water-soluble drug. Solid dispersion tablets were prepared with the wet granulation method using ethanol and water by a high-speed mixer granulator. The binder and disintegrant were selected from 7 and 4 candidates, respectively. The dissolution test was conducted using the JP 16 paddle method. The oral absorption of NIF was studied in fasted rats. Xylitol and crospovidone were selected as the binder and disintegrant, respectively. The dissolution rates of NIF from solid dispersion formulations were markedly enhanced compared with NIF powder and physical mixtures. Powder X-ray diffraction (PXRD) confirmed the reduced crystallinity of NIF in the solid dispersion formulations. Fourier transform infrared (FT-IR) showed the physical interaction between NIF and PCS in the solid dispersion formulations. NIF is present in an amorphous state in granules prepared by the wet granulation method using water. The area under the plasma concentration-time curve (AUC) and peak concentration (C(max)) values of NIF after dosing rats with the solid dispersion granules were significantly greater than those after dosing with NIF powder. The solid dispersion formulations of NIF prepared with PCS using the wet granulation method exhibited accelerated dissolution rates and superior oral bioavailability. This method is very simple, and may be applicable to the development of other poorly water-soluble drugs.

Characteristics and nutritional value of whole wheat cracker fortified with tuna bone bio-calcium powder.

PubMed

Benjakul, Soottawat; Karnjanapratum, Supatra

2018-09-01

Whole wheat cracker fortified with tuna bone bio-calcium (Bio-Ca) powder was developed as health-promoting food rich in calcium. Fortification with different levels of Bi-Ca, over the range of 0-50% of whole wheat flour (w/w) on quality and sensory properties of crackers, were determined. Color, thickness, weight and textural properties of crackers varied with the different levels of Bio-Ca powder added, but it was found that up to 30% could be added without detrimental effect on sensory properties. Scanning electron microscopic images showed that the developed crackers were less porous and had a denser structure, compared to the control. Based on scanning electron microscopy-energy dispersive X-ray spectroscopic (SEM-EDX), the cracker containing Bio-Ca powder had calcium and phosphorous distribution with higher intensity, compared to the control. The fortified crackers were rich in calcium and phosphorous with higher protein content but lower fat, carbohydrate, cholesterol and energy value, compared to the control. Copyright © 2018 Elsevier Ltd. All rights reserved.

Sol–gel method to fabricate CaP scaffolds by robocasting for tissue engineering

PubMed Central

Fu, Qiang; Saiz, Eduardo; Tomsia, Antoni P.

2012-01-01

Highly porous calcium phosphate (CaP) scaffolds for bone-tissue engineering were fabricated by combining a robocasting process with a sol–gel synthesis that mixed Calcium Nitrate Tetrahydrate and Triethyl Phosphite precursors in an aqueous medium. The resulting gels were used to print scaffolds by robocasting without the use of binder to increase the viscosity of the paste. X-ray diffraction analysis confirmed that the process yielded hydroxyapatite and β-tricalcium phosphate biphasic composite powders. Thus, the scaffold composition after crystallization of the amorphous structure could be easily modified by varying the initial Ca/P ratio during synthesis. The compressive strengths of the scaffolds are ~6 MPa, which is in the range of human cancellous bone (2–12 MPa). These highly porous scaffolds (~73 vol% porosity) are composed of macro-pores of ~260 μm in size; such porosity is expected to enable bone ingrowth into the scaffold for bone repair applications. The chemistry, porosity, and surface topography of such scaffolds can also be modified by the process parameters to favor bone formation. The studied sol–gel process can be used to coat these scaffolds by dip-coating, which induces a significant enhancement of mechanical properties. This can adjust scaffold properties such as composition and surface morphology, which consequently may improve their performances. PMID:22311079

The effect of collagen fibril orientation on the biphasic mechanics of articular cartilage.

PubMed

Meng, Qingen; An, Shuqiang; Damion, Robin A; Jin, Zhongmin; Wilcox, Ruth; Fisher, John; Jones, Alison

2017-01-01

The highly inhomogeneous distribution of collagen fibrils may have important effects on the biphasic mechanics of articular cartilage. However, the effect of the inhomogeneity of collagen fibrils has mainly been investigated using simplified three-layered models, which may have underestimated the effect of collagen fibrils by neglecting their realistic orientation. The aim of this study was to investigate the effect of the realistic orientation of collagen fibrils on the biphasic mechanics of articular cartilage. Five biphasic material models, each of which included a different level of complexity of fibril reinforcement, were solved using two different finite element software packages (Abaqus and FEBio). Model 1 considered the realistic orientation of fibrils, which was derived from diffusion tensor magnetic resonance images. The simplified three-layered orientation was used for Model 2. Models 3-5 were three control models. The realistic collagen orientations obtained in this study were consistent with the literature. Results from the two finite element implementations were in agreement for each of the conditions modelled. The comparison between the control models confirmed some functions of collagen fibrils. The comparison between Models 1 and 2 showed that the widely-used three-layered inhomogeneous model can produce similar fluid load support to the model including the realistic fibril orientation; however, an accurate prediction of the other mechanical parameters requires the inclusion of the realistic orientation of collagen fibrils. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

Two cases of traumatic head injury mimicking acute encephalopathy with biphasic seizures and late reduced diffusion.

PubMed

Nishiyama, Masahiro; Fujita, Kyoko; Maruyama, Azusa; Nagase, Hiroaki

2014-11-01

Acute encephalopathy with biphasic seizures and late reduced diffusion (AESD) presents a distinct clinical course of biphasic seizures and impaired consciousness. These symptoms are followed by reduced diffusion in the subcortical white matter on magnetic resonance imaging that is typically observed between 3 and 9 days after illness onset. Here, we report two cases of traumatic head injury with clinical and radiological features similar to those for AESD. The similarities between our cases and AESD may be useful in understanding the pathogenesis of AESD. Copyright © 2013 The Japanese Society of Child Neurology. Published by Elsevier B.V. All rights reserved.

Comparison of outcomes after use of biphasic or monophasic defibrillators among out-of-hospital cardiac arrest patients: a nationwide population-based observational study.

PubMed

Tanabe, Seizan; Yasunaga, Hideo; Ogawa, Toshio; Koike, Soichi; Akahane, Manabu; Horiguchi, Hiromasa; Hatanaka, Tetsuo; Yokota, Hiroyuki; Imamura, Tomoaki

2012-09-01

The use and popularity of the biphasic waveform defibrillator as a replacement for the monophasic waveform defibrillator are increasing, but it is unclear whether this can improve the rate of survival among out-of-hospital cardiac arrest patients. This study aimed to verify the hypothesis that the outcome of out-of-hospital cardiac arrest patients who received defibrillation shock with the biphasic waveform defibrillator was better than that of patients who received defibrillation shock with the monophasic defibrillator. This prospective, nationwide, population-based, observational study included 21 172 out-of-hospital cardiac arrest patients with initial ventricular fibrillation or pulseless ventricular tachycardia from January 1, 2005, through December 31, 2007. Defibrillation shock was performed by monophasic defibrillator on 8224 (39%) patients and by biphasic defibrillator on 12 948 (61%) patients. The rate of survival at 1 month with minimal neurological impairment was 11.6% (951/8192) in the monophasic defibrillator group and 12.8% (1653/12 928) in the biphasic defibrillator group. Hierarchical logistic regression analysis using a generalized estimation equation showed no significant difference between the biphasic and monophasic groups in 1-month survival with minimal neurological impairment (adjusted odds ratio, 1.07; 95% confidence interval, 0.91-1.26; P=0.42). Confirmatory propensity score analyses showed similar results. Although monophasic defibrillators are being replaced by biphasic defibrillators, our nationwide population-based observational study failed to demonstrate a statistically significant association between defibrillation waveform and 1-month survival rate with minimal neurological impairment.

Preparation of in situ hardening composite microcarriers: Calcium phosphate cement combined with alginate for bone regeneration

PubMed Central

Park, Jung-Hui; Lee, Eun-Jung; Knowles, Jonathan C

2014-01-01

Novel microcarriers consisting of calcium phosphate cement and alginate were prepared for use as three-dimensional scaffolds for the culture and expansion of cells that are effective for bone tissue engineering. The calcium phosphate cement-alginate composite microcarriers were produced by an emulsification of the composite aqueous solutions mixed at varying ratios (calcium phosphate cement powder/alginate solution = 0.8–1.2) in an oil bath and the subsequent in situ hardening of the compositions during spherodization. Moreover, a porous structure could be easily created in the solid microcarriers by soaking the produced microcarriers in water and a subsequent freeze-drying process. Bone mineral-like apatite nanocrystallites were shown to rapidly develop on the calcium phosphate cement–alginate microcarriers under moist conditions due to the conversion of the α-tricalcium phosphate phase in the calcium phosphate cement into a carbonate–hydroxyapatite. Osteoblastic cells cultured on the microspherical scaffolds were proven to be viable, with an active proliferative potential during 14 days of culture, and their osteogenic differentiation was confirmed by the determination of alkaline phosphatase activity. The in situ hardening calcium phosphate cement–alginate microcarriers developed herein may be used as potential three-dimensional scaffolds for cell delivery and tissue engineering of bone. PMID:23836845

Thermodynamics and kinetics of the sulfation of porous calcium silicate

NASA Technical Reports Server (NTRS)

Miller, R. A.; Kohl, F. J.

1981-01-01

The sulfation of plasma sprayed calcium silicate in flowing SO2/air mixtures at 900 and 1000 C was investigated thermogravimetrically. Reaction products were analyzed using electron microprobe and X-ray diffraction analysis techniques, and results were compared with thermodynamic predictions. The percentage, by volume, of SO2 in air was varied between 0.036 and 10 percent. At 10 percent SO2 the weight gain curve displays a concave downward shoulder early in the sulfation process. An analytical model was developed which treats the initial process as one which decays exponentially with increasing time and the subsequent process as one which decays exponentially with increasing weight gain. At lower SO2 levels the initial rate is controlled by the reactant flow rate. At 1100 C and 0.036 percent SO2 there is no reaction, in agreement with thermodynamic predictions.

Production of Furfural from Process-Relevant Biomass-Derived Pentoses in a Biphasic Reaction System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mittal, Ashutosh; Black, Stuart K.; Vinzant, Todd B.

Furfural is an important fuel precursor which can be converted to hydrocarbon fuels and fuel intermediates. In this work, the production of furfural by dehydration of process-relevant pentose rich corn stover hydrolyzate using a biphasic batch reaction system has been investigated. Methyl isobutyl ketone (MIBK) and toluene have been used to extract furfural and enhance overall furfural yield by limiting its degradation to humins. The effects of reaction time, temperature, and acid concentration (H 2SO 4) on pentose conversion and furfural yield were investigated. For the dehydration of 8 wt % pentose-rich corn stover hydrolyzate under optimum reaction conditions, 0.05more » M H 2SO 4, 170 degrees C for 20 min with MIBK as the solvent, complete conversion of xylose (98-100%) and a furfural yield of 80% were obtained. Under these same conditions, except with toluene as the solvent, the furfural yield was 77%. Additionally, dehydration of process-relevant pentose rich corn stover hydrolyzate using solid acid ion-exchange resins under optimum reaction conditions has shown that Purolite CT275 is as effective as H 2SO 4 for obtaining furfural yields approaching 80% using a biphasic batch reaction system. In conclusion, this work has demonstrated that a biphasic reaction system can be used to process biomass-derived pentose rich sugar hydrolyzates to furfural in yields approaching 80%.« less

Production of Furfural from Process-Relevant Biomass-Derived Pentoses in a Biphasic Reaction System

DOE PAGES

Mittal, Ashutosh; Black, Stuart K.; Vinzant, Todd B.; ...

2017-05-16

Furfural is an important fuel precursor which can be converted to hydrocarbon fuels and fuel intermediates. In this work, the production of furfural by dehydration of process-relevant pentose rich corn stover hydrolyzate using a biphasic batch reaction system has been investigated. Methyl isobutyl ketone (MIBK) and toluene have been used to extract furfural and enhance overall furfural yield by limiting its degradation to humins. The effects of reaction time, temperature, and acid concentration (H 2SO 4) on pentose conversion and furfural yield were investigated. For the dehydration of 8 wt % pentose-rich corn stover hydrolyzate under optimum reaction conditions, 0.05more » M H 2SO 4, 170 degrees C for 20 min with MIBK as the solvent, complete conversion of xylose (98-100%) and a furfural yield of 80% were obtained. Under these same conditions, except with toluene as the solvent, the furfural yield was 77%. Additionally, dehydration of process-relevant pentose rich corn stover hydrolyzate using solid acid ion-exchange resins under optimum reaction conditions has shown that Purolite CT275 is as effective as H 2SO 4 for obtaining furfural yields approaching 80% using a biphasic batch reaction system. In conclusion, this work has demonstrated that a biphasic reaction system can be used to process biomass-derived pentose rich sugar hydrolyzates to furfural in yields approaching 80%.« less

Computational solvent system screening for the separation of tocopherols with centrifugal partition chromatography using deep eutectic solvent-based biphasic systems.

PubMed

Bezold, Franziska; Weinberger, Maria E; Minceva, Mirjana

2017-03-31

Tocopherols are a class of molecules with vitamin E activity. Among those, α-tocopherol is the most important vitamin E source in the human diet. The purification of tocopherols involving biphasic liquid systems can be challenging since these vitamins are poorly soluble in water. Deep eutectic solvents (DES) can be used to form water-free biphasic systems and have already proven applicable for centrifugal partition chromatography separations. In this work, a computational solvent system screening was performed using the predictive thermodynamic model COSMO-RS. Liquid-liquid equilibria of solvent systems composed of alkanes, alcohols and DES, as well as partition coefficients of α-tocopherol, β-tocopherol, γ-tocopherol, and σ-tocopherol in these biphasic solvent systems were calculated. From the results the best suited biphasic solvent system, namely heptane/ethanol/choline chloride-1,4-butanediol, was chosen and a batch injection of a tocopherol mixture, mainly consisting of α- and γ-tocopherol, was performed using a centrifugal partition chromatography set up (SCPE 250-BIO). A separation factor of 1.74 was achieved for α- and γ-tocopherol. Copyright © 2017 Elsevier B.V. All rights reserved.

Calcium phosphate coating of nickel-titanium shape-memory alloys. Coating procedure and adherence of leukocytes and platelets.

PubMed

Choi, Jongsik; Bogdanski, Denise; Köller, Manfred; Esenwein, Stefan A; Müller, Dietmar; Muhr, Gert; Epple, Matthias

2003-09-01

Nickel-titanium shape-memory alloys (NiTi-SMA) were coated with calcium phosphate by dipping in oversaturated calcium phosphate solution. The layer thickness (typically 5-20 micrometer) can be varied by choice of the immersion time. The porous nature of the layer of microcrystals makes it mechanically stable enough to withstand both the shape-memory transition upon cooling and heating and also strong bending of the material (superelastic effect). This layer may improve the biocompatibility of NiTi-SMA, particulary for osteosynthetic devices by creating a more physiological surface and by restricting a potential nickel release. The adherence of human leukocytes (peripheral blood mononuclear cells and polymorphonuclear neutrophil granulocytes) and platelets to the calcium phosphate layer was analyzed in vitro. In comparison to non-coated NiTi-SMA, leukocytes and platelets showed a significantly increased adhesion to the coated NiTi-SMA.

Biphasic rattlesnake venom-induced thrombocytopenia.

PubMed

Offerman, Steven R; Barry, J David; Schneir, Aaron; Clark, Richard F

2003-04-01

Thrombocytopenia is a common occurrence in moderate to severe crotaline envenomation. The exact mechanism by which rattlesnake venom leads to thrombocytopenia is unclear, but aggressive treatment with crotaline-specific antivenom often leads to resolution of this disorder. Crotalinae Polyvalent Immune Fab (CroFab(TM), Protherics Inc., Nashville, TN) (crotaline Fab) is now available for the treatment of symptomatic rattlesnake envenomation. Although recurrence of thrombocytopenia has been reported in patients after envenomation treated with crotaline Fab, cases refractory to this therapy have not been described. We report a case of severe crotaline envenomation that appears to have exhibited two separate episodes of thrombocytopenia, only one of which responded to antivenom. The second, later phase was refractory to both crotaline Fab as well as traditional Antivenin (Crotalinae) Polyvalent (Wyeth-Ayerst Pharmaceuticals, Philadelphia, PA) (ACP). By reviewing the literature regarding venom-induced thrombocytopenia, we attempt to explain this "biphasic" phenomenon and the inability of crotaline Fab to reverse this toxic effect.

Impact of mineral precipitation on flow and mixing in porous media determined by microcomputed tomography and MRI

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bray, Joshua M.; Lauchnor, Ellen G.; Redden, George D.

Here, precipitation reactions in porous media influence transport properties of the environment and can control advective and dispersive transport. In subsurface environments, mixing of saline groundwater or injected solutions for remediation with fresh groundwater can induce supersaturation of constituents and drive precipitation reactions. Magnetic resonance imaging (MRI) and micro-computed tomography (µ-CT) were employed as complimentary techniques to evaluate advection, dispersion and formation of precipitate in a 3D porous media flow cell. Two parallel fluids were flowed concentrically through the porous media under two flow rate conditions with Na 2CO 3 and CaCl 2 in the inner and outer fluids, respectively.more » Upon mixing, calcium carbonate became supersaturated and formed a precipitate at the interface of the two fluids. Spatial maps of changing local velocity fields and dispersion in the flow cell were generated from MRI, while high resolution imaging of the precipitate formed in the porous media was achieved via µ-CT imaging. Formation of a precipitate layer minimized dispersive and advective transport between the two fluids and the shape of the precipitation was influenced by the flow rate condition.« less

Impact of mineral precipitation on flow and mixing in porous media determined by microcomputed tomography and MRI

DOE PAGES

Bray, Joshua M.; Lauchnor, Ellen G.; Redden, George D.; ...

2016-12-21

Here, precipitation reactions in porous media influence transport properties of the environment and can control advective and dispersive transport. In subsurface environments, mixing of saline groundwater or injected solutions for remediation with fresh groundwater can induce supersaturation of constituents and drive precipitation reactions. Magnetic resonance imaging (MRI) and micro-computed tomography (µ-CT) were employed as complimentary techniques to evaluate advection, dispersion and formation of precipitate in a 3D porous media flow cell. Two parallel fluids were flowed concentrically through the porous media under two flow rate conditions with Na 2CO 3 and CaCl 2 in the inner and outer fluids, respectively.more » Upon mixing, calcium carbonate became supersaturated and formed a precipitate at the interface of the two fluids. Spatial maps of changing local velocity fields and dispersion in the flow cell were generated from MRI, while high resolution imaging of the precipitate formed in the porous media was achieved via µ-CT imaging. Formation of a precipitate layer minimized dispersive and advective transport between the two fluids and the shape of the precipitation was influenced by the flow rate condition.« less

* Fabrication and Characterization of Biphasic Silk Fibroin Scaffolds for Tendon/Ligament-to-Bone Tissue Engineering.

PubMed

Font Tellado, Sònia; Bonani, Walter; Balmayor, Elizabeth R; Foehr, Peter; Motta, Antonella; Migliaresi, Claudio; van Griensven, Martijn

2017-08-01

Tissue engineering is an attractive strategy for tendon/ligament-to-bone interface repair. The structure and extracellular matrix composition of the interface are complex and allow for a gradual mechanical stress transfer between tendons/ligaments and bone. Thus, scaffolds mimicking the structural features of the native interface may be able to better support functional tissue regeneration. In this study, we fabricated biphasic silk fibroin scaffolds designed to mimic the gradient in collagen molecule alignment present at the interface. The scaffolds had two different pore alignments: anisotropic at the tendon/ligament side and isotropic at the bone side. Total porosity ranged from 50% to 80% and the majority of pores (80-90%) were <100-300 μm. Young's modulus varied from 689 to 1322 kPa depending on the type of construct. In addition, human adipose-derived mesenchymal stem cells were cultured on the scaffolds to evaluate the effect of pore morphology on cell proliferation and gene expression. Biphasic scaffolds supported cell attachment and influenced cytoskeleton organization depending on pore alignment. In addition, the gene expression of tendon/ligament, enthesis, and cartilage markers significantly changed depending on pore alignment in each region of the scaffolds. In conclusion, the biphasic scaffolds fabricated in this study show promising features for tendon/ligament-to-bone tissue engineering.

Protein encapsulation via porous CaCO3 microparticles templating.

PubMed

Volodkin, Dmitry V; Larionova, Natalia I; Sukhorukov, Gleb B

2004-01-01

Porous microparticles of calcium carbonate with an average diameter of 4.75 microm were prepared and used for protein encapsulation in polymer-filled microcapsules by means of electrostatic layer-by-layer assembly (ELbL). Loading of macromolecules in porous CaCO3 particles is affected by their molecular weight due to diffusion-limited permeation inside the particles and also by the affinity to the carbonate surface. Adsorption of various proteins and dextran was examined as a function of pH and was found to be dependent both on the charge of the microparticles and macromolecules. The electrostatic effect was shown to govern this interaction. This paper discusses the factors which can influence the adsorption capacity of proteins. A new way of protein encapsulation in polyelectrolyte microcapsules is proposed exploiting the porous, biocompatible, and decomposable microparticles from CaCO3. It consists of protein adsorption in the pores of the microparticles followed by ELbL of oppositely charged polyelectrolytes and further core dissolution. This resulted in formation of polyelectrolyte-filled capsules with protein incorporated in interpenetrating polyelectrolyte network. The properties of CaCO3 microparticles and capsules prepared were characterized by scanning electron microscopy, microelectrophoresis, and confocal laser scanning microscopy. Lactalbumin was encapsulated by means of the proposed technique yielding a content of 0.6 pg protein per microcapsule. Horseradish peroxidase saves 37% of activity after encapsulation. However, the thermostability of the enzyme was improved by encapsulation. The results demonstrate that porous CaCO3 microparticles can be applied as microtemplates for encapsulation of proteins into polyelectrolyte capsules at neutral pH as an optimal medium for a variety of bioactive material, which can also be encapsulated by the proposed method. Microcapsules filled with encapsulated material may find applications in the field of

Evaluation of a Unique Defibrillation Unit with Dual-Vector Biphasic Waveform Capabilities: Towards a Miniaturized Defibrillator.

PubMed

Okamura, Hideo; Desimone, Christopher V; Killu, Ammar M; Gilles, Emily J; Tri, Jason; Asirvatham, Roshini; Ladewig, Dejae J; Suddendorf, Scott H; Powers, Joanne M; Wood-Wentz, Christina M; Gray, Peter D; Raymond, Douglas M; Savage, Shelley J; Savage, Walter T; Bruce, Charles J; Asirvatham, Samuel J; Friedman, Paul A

2017-02-01

Automated external defibrillators can provide life-saving therapies to treat ventricular fibrillation. We developed a prototype unit that can deliver a unique shock waveform produced by four independent capacitors that is delivered through two shock vectors, with the rationale of providing more robust shock pathways during emergent defibrillation. We describe the initial testing and feasibility of this unique defibrillation unit, features of which may enable downsizing of current defibrillator devices. We tested our defibrillation unit in four large animal models (two canine and two swine) under general anesthesia. Experimental defibrillation thresholds (DFT) were obtained by delivery of a unique waveform shock pulse via a dual-vector pathway with four defibrillation pads (placed across the chest). DFTs were measured and compared with those of a commercially available biphasic defibrillator (Zoll M series, Zoll Medical, Chelmsford, MA, USA) tested in two different vectors. Shocks were delivered after 10 seconds of stable ventricular fibrillation and the output characteristics and shock outcome recorded. Each defibrillation series used a step-down to failure protocol to define the defibrillation threshold. A total of 96 shocks were delivered during ventricular fibrillation in four large animals. In comparison to the Zoll M series, which delivered a single-vector, biphasic shock, the energy required for successful defibrillation using the unique dual-vector biphasic waveform did not differ significantly (P = 0.65). Our early findings support the feasibility of a unique external defibrillation unit using a dual-vector biphasic waveform approach. This warrants further study to leverage this unique concept and work toward a miniaturized, portable shock delivery system. © 2016 Wiley Periodicals, Inc.

Porous organic cages

NASA Astrophysics Data System (ADS)

Tozawa, Tomokazu; Jones, James T. A.; Swamy, Shashikala I.; Jiang, Shan; Adams, Dave J.; Shakespeare, Stephen; Clowes, Rob; Bradshaw, Darren; Hasell, Tom; Chong, Samantha Y.; Tang, Chiu; Thompson, Stephen; Parker, Julia; Trewin, Abbie; Bacsa, John; Slawin, Alexandra M. Z.; Steiner, Alexander; Cooper, Andrew I.

2009-12-01

Porous materials are important in a wide range of applications including molecular separations and catalysis. We demonstrate that covalently bonded organic cages can assemble into crystalline microporous materials. The porosity is prefabricated and intrinsic to the molecular cage structure, as opposed to being formed by non-covalent self-assembly of non-porous sub-units. The three-dimensional connectivity between the cage windows is controlled by varying the chemical functionality such that either non-porous or permanently porous assemblies can be produced. Surface areas and gas uptakes for the latter exceed comparable molecular solids. One of the cages can be converted by recrystallization to produce either porous or non-porous polymorphs with apparent Brunauer-Emmett-Teller surface areas of 550 and 23m2g-1, respectively. These results suggest design principles for responsive porous organic solids and for the modular construction of extended materials from prefabricated molecular pores.

Calcium bioavailability and kinetics of calcium ascorbate and calcium acetate in rats.

PubMed

Cai, Jianwei; Zhang, Qinmin; Wastney, Meryl E; Weaver, Connie M

2004-01-01

The objective was to investigate the bioavailability and mechanism of calcium absorption of calcium ascorbate (ASC) and calcium acetate (AC). A series of studies was performed in adult Sprague-Dawley male rats. In the first study, each group of rats (n = 10/group) was assigned to one of the five test meals labeled with (45)Ca: (i) 25 mg calcium as heated ASC or (ii) unheated ASC, (iii) 25 mg calcium as unheated AC, (iv) 3.6 mg Ca as unheated ASC, or (v) unheated AC. Femur uptake indicated better calcium bioavailability from ASC than AC at both calcium loads. A 5-min heat treatment partly reduced bioavailability of ASC. Kinetic studies were performed to further investigate the mechanism of superior calcium bioavailability from ASC. Two groups of rats (n = 10/group) received oral doses of 25 mg Ca as ASC or AC. Each dose contained 20 micro Ci (45)Ca. Two additional groups of rats (n = 10/group) received an intravenous injection (iv) of 10 micro Ci (45)Ca after receiving an unlabeled oral dose of 25 mg calcium as ASC or AC. Sequential blood samples were collected over 48 hrs. Urine and fecal samples were collected every 12 hrs for 48 hrs and were analyzed for total calcium and (45)Ca content. Total calcium and (45)Ca from serum, urine, and feces were fitted by a compartment kinetics model with saturable and nonsaturable absorption pathways by WinSAAM (Windows-based Simulation Analysis and Modeling). The difference in calcium bioavailability between the two salts was due to differences in saturable rather than passive intestinal absorption and not to endogenous secretion or calcium deposition rate. The higher bioavailability of calcium ascorbate was due to a longer transit time in the small intestine compared with ASC.

Biomimetic fabrication of a three-level hierarchical calcium phosphate/collagen/hydroxyapatite scaffold for bone tissue engineering.

PubMed

Zhou, Changchun; Ye, Xingjiang; Fan, Yujiang; Ma, Liang; Tan, Yanfei; Qing, Fangzu; Zhang, Xingdong

2014-09-01

A three-level hierarchical calcium phosphate/collagen/hydroxyapatite (CaP/Col/HAp) scaffold for bone tissue engineering was developed using biomimetic synthesis. Porous CaP ceramics were first prepared as substrate materials to mimic the porous bone structure. A second-level Col network was then composited into porous CaP ceramics by vacuum infusion. Finally, a third-level HAp layer was achieved by biomimetic mineralization. The three-level hierarchical biomimetic scaffold was characterized using scanning electron microscopy, energy-dispersive x-ray spectra, x-ray diffraction and Fourier transform infrared spectroscopy, and the mechanical properties of the scaffold were evaluated using dynamic mechanical analysis. The results show that this scaffold exhibits a similar structure and composition to natural bone tissues. Furthermore, this three-level hierarchical biomimetic scaffold showed enhanced mechanical strength compared with pure porous CaP scaffolds. The biocompatibility and osteoinductivity of the biomimetic scaffolds were evaluated using in vitro and in vivo tests. Cell culture results indicated the good biocompatibility of this biomimetic scaffold. Faster and increased bone formation was observed in these scaffolds following a six-month implantation in the dorsal muscles of rabbits, indicating that this biomimetic scaffold exhibits better osteoinductivity than common CaP scaffolds.

A biphasic parameter estimation method for quantitative analysis of dynamic renal scintigraphic data

NASA Astrophysics Data System (ADS)

Koh, T. S.; Zhang, Jeff L.; Ong, C. K.; Shuter, B.

2006-06-01

Dynamic renal scintigraphy is an established method in nuclear medicine, commonly used for the assessment of renal function. In this paper, a biphasic model fitting method is proposed for simultaneous estimation of both vascular and parenchymal parameters from renal scintigraphic data. These parameters include the renal plasma flow, vascular and parenchymal mean transit times, and the glomerular extraction rate. Monte Carlo simulation was used to evaluate the stability and confidence of the parameter estimates obtained by the proposed biphasic method, before applying the method on actual patient study cases to compare with the conventional fitting approach and other established renal indices. The various parameter estimates obtained using the proposed method were found to be consistent with the respective pathologies of the study cases. The renal plasma flow and extraction rate estimated by the proposed method were in good agreement with those previously obtained using dynamic computed tomography and magnetic resonance imaging.

Effect of enzymatic degradation of chitosan in polyhydroxybutyrate/chitosan/calcium phosphate composites on in vitro osteoblast response.

PubMed

Giretova, Maria; Medvecky, Lubomir; Stulajterova, Radoslava; Sopcak, Tibor; Briancin, Jaroslav; Tatarkova, Monika

2016-12-01

Polyhydroxybutyrate/chitosan/calcium phosphate composites are interesting biomaterials for utilization in regenerative medicine and they may by applied in reconstruction of deeper subchondral defects. Insufficient informations were found in recent papers about the influence of lysozyme degradation of chitosan in calcium phosphate/chitosan based composites on in vitro cytotoxicity and proliferation activity of osteoblasts. The effect of enzymatic chitosan degradation on osteoblasts proliferation was studied on composite films in which the porosity of origin 3D scaffolds was eliminated and the surface texture was modified. The significantly enhanced proliferation activity with faster population growth of osteoblasts were found on enzymatically degraded biopolymer composite films with α-tricalcium phosphate and nanohydroxyapatite. No cytotoxicity of composite films prepared from lysozyme degraded scaffolds containing a large fraction of low molecular weight chitosans (LMWC), was revealed after 10 days of cultivation. Contrary to above in the higher cytotoxicity origin untreated nanohydroxyapatite films and porous composite scaffolds. The results showed that the synergistic effect of surface distribution, morphology of nanohydroxyapatite particles, microtopography and the presence of LMWC due to chitosan degradation in composite films were responsible for compensation of the cytotoxicity of nanohydroxyapatite composite films or porous composite scaffolds.

A randomised controlled trial of the effect of biphasic or monophasic waveform on the incidence and severity of cutaneous burns following external direct current cardioversion.

PubMed

Ambler, Jonathan J S; Deakin, Charles D

2006-12-01

Cutaneous burns are a common cause of morbidity following direct current (DC) cardioversion. We designed a prospective randomised double-blinded controlled study to determine the effect of biphasic or monophasic waveform on the pain and inflammation occurring after elective cardioversion. One hundred and thirty nine patients undergoing elective DC cardioversion were randomised to receive monophasic (HP Codemaster XL; 100, 200, 300, 360, and 360 J) or biphasic (Welch Allyn-MRL PIC defibrillator; 70, 100, 150, 200, and 300 J) waveforms. Two hours after DC cardioversion, skin temperature, erythema index and sensory threshold to light and sharp touch was measured at the centre and edge of paddle sites. Visual analogue pain score (VAS) was recorded at 2 and 24 h. There was significantly less pain following biphasic cardioversion as assessed by VAS at both 2 h (p < 0.001; 95% confidence intervals of difference of medians (CI) 0.2-0.8 cm) and 24 h (p = 0.004; 95% CI 0.0-0.4 cm). There was significantly less erythema in patients receiving biphasic cardioversion at the edge of the sternal site (p = 0.046; 95% CI 0.41-4.5). There was no difference in any other variable at any site between biphasic and monophasic cardioversion. The use of a biphasic waveform for DC cardioversion reduces the inflammation and pain of burns as measured by erythema index and visual analogue scale.

Biphasic and monophasic repair: comparative implications for biologically equivalent dose calculations in pulsed dose rate brachytherapy of cervical carcinoma

PubMed Central

Millar, W T; Davidson, S E

2013-01-01

Objective: To consider the implications of the use of biphasic rather than monophasic repair in calculations of biologically-equivalent doses for pulsed-dose-rate brachytherapy of cervix carcinoma. Methods: Calculations are presented of pulsed-dose-rate (PDR) doses equivalent to former low-dose-rate (LDR) doses, using biphasic vs monophasic repair kinetics, both for cervical carcinoma and for the organ at risk (OAR), namely the rectum. The linear-quadratic modelling calculations included effects due to varying the dose per PDR cycle, the dose reduction factor for the OAR compared with Point A, the repair kinetics and the source strength. Results: When using the recommended 1 Gy per hourly PDR cycle, different LDR-equivalent PDR rectal doses were calculated depending on the choice of monophasic or biphasic repair kinetics pertaining to the rodent central nervous and skin systems. These differences virtually disappeared when the dose per hourly cycle was increased to 1.7 Gy. This made the LDR-equivalent PDR doses more robust and independent of the choice of repair kinetics and α/β ratios as a consequence of the described concept of extended equivalence. Conclusion: The use of biphasic and monophasic repair kinetics for optimised modelling of the effects on the OAR in PDR brachytherapy suggests that an optimised PDR protocol with the dose per hourly cycle nearest to 1.7 Gy could be used. Hence, the durations of the new PDR treatments would be similar to those of the former LDR treatments and not longer as currently prescribed. Advances in knowledge: Modelling calculations indicate that equivalent PDR protocols can be developed which are less dependent on the different α/β ratios and monophasic/biphasic kinetics usually attributed to normal and tumour tissues for treatment of cervical carcinoma. PMID:23934965

Effects of Pore Size on the Osteoconductivity and Mechanical Properties of Calcium Phosphate Cement in a Rabbit Model.

PubMed

Zhao, Yi-Nan; Fan, Jun-Jun; Li, Zhi-Quan; Liu, Yan-Wu; Wu, Yao-Ping; Liu, Jian

2017-02-01

Calcium phosphate cement (CPC) porous scaffold is widely used as a suitable bone substitute to repair bone defect, but the optimal pore size is unclear yet. The current study aimed to evaluate the effect of different pore sizes on the processing of bone formation in repairing segmental bone defect of rabbits using CPC porous scaffolds. Three kinds of CPC porous scaffolds with 5 mm diameters and 12 mm length were prepared with the same porosity but different pore sizes (Group A: 200-300 µm, Group B: 300-450 µm, Group C: 450-600 µm, respectively). Twelve millimeter segmental bone defects were created in the middle of the radius bone and filled with different kinds of CPC cylindrical scaffolds. After 4, 12, and 24 weeks, alkaline phosphatase (ALP), histological assessment, and mechanical properties evaluation were performed in all three groups. After 4 weeks, ALP activity increased in all groups but was highest in Group A with smallest pore size. The new bone formation within the scaffolds was not obvious in all groups. After 12 weeks, the new bone formation within the scaffolds was obvious in each group and highest in Group A. At 24 weeks, no significant difference in new bone formation was observed among different groups. Besides the osteoconductive effect, Group A with smallest pore size also had the best mechanical properties in vivo at 12 weeks. We demonstrate that pore size has a significant effect on the osteoconductivity and mechanical properties of calcium phosphate cement porous scaffold in vivo. Small pore size favors the bone formation in the early stage and may be more suitable for repairing segmental bone defect in vivo. © 2016 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

Evaluation of parallel milliliter-scale stirred-tank bioreactors for the study of biphasic whole-cell biocatalysis with ionic liquids.

PubMed

Dennewald, Danielle; Hortsch, Ralf; Weuster-Botz, Dirk

2012-01-01

As clear structure-activity relationships are still rare for ionic liquids, preliminary experiments are necessary for the process development of biphasic whole-cell processes involving these solvents. To reduce the time investment and the material costs, the process development of such biphasic reaction systems would profit from a small-scale high-throughput platform. Exemplarily, the reduction of 2-octanone to (R)-2-octanol by a recombinant Escherichia coli in a biphasic ionic liquid/water system was studied in a miniaturized stirred-tank bioreactor system allowing the parallel operation of up to 48 reactors at the mL-scale. The results were compared to those obtained in a 20-fold larger stirred-tank reactor. The maximum local energy dissipation was evaluated at the larger scale and compared to the data available for the small-scale reactors, to verify if similar mass transfer could be obtained at both scales. Thereafter, the reaction kinetics and final conversions reached in different reactions setups were analysed. The results were in good agreement between both scales for varying ionic liquids and for ionic liquid volume fractions up to 40%. The parallel bioreactor system can thus be used for the process development of the majority of biphasic reaction systems involving ionic liquids, reducing the time and resource investment during the process development of this type of applications. Copyright © 2011. Published by Elsevier B.V.

Variably porous structures

DOEpatents

Braun, Paul V [Savoy, IL; Yu, Xindi [Urbana, IL

2011-01-18

A method of making a monolithic porous structure, comprises electrodepositing a material on a template; removing the template from the material to form a monolithic porous structure comprising the material; and electropolishing the monolithic porous structure.

The biphasic effect of extracellular glucose concentration on carbachol-induced fluid secretion from mouse submandibular glands.

PubMed

Terachi, Momomi; Hirono, Chikara; Kitagawa, Michinori; Sugita, Makoto

2018-06-01

Cholinergic agonists evoke elevations of the cytoplasmic free-calcium concentration ([Ca 2+ ] i ) to stimulate fluid secretion in salivary glands. Salivary flow rates are significantly reduced in diabetic patients. However, it remains elusive how salivary secretion is impaired in diabetes. Here, we used an ex vivo submandibular gland perfusion technique to characterize the dependency of salivary flow rates on extracellular glucose concentration and activities of glucose transporters expressed in the glands. The cholinergic agonist carbachol (CCh) induced sustained fluid secretion, the rates of which were modulated by the extracellular glucose concentration in a biphasic manner. Both lowering the extracellular glucose concentration to less than 2.5 mM and elevating it to higher than 5 mM resulted in decreased CCh-induced fluid secretion. The CCh-induced salivary flow was suppressed by phlorizin, an inhibitor of the sodium-glucose cotransporter 1 (SGLT1) located basolaterally in submandibular acinar cells, which is altered at the protein expression level in diabetic animal models. Our data suggest that SGLT1-mediated glucose uptake in acinar cells is required to maintain the fluid secretion by sustaining Cl - secretion in real-time. High extracellular glucose levels may suppress the CCh-induced secretion of salivary fluid by altering the activities of ion channels and transporters downstream of [Ca 2+ ] i signals. © 2018 Eur J Oral Sci.

Acute exercise induces biphasic increase in respiratory mRNA in skeletal muscle

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ikeda, Shin-ichi; Kizaki, Takako; Haga, Shukoh

2008-04-04

Peroxisome proliferator-activated receptor {gamma} coactivator-1{alpha} (PGC-1{alpha}) promotes the expression of oxidative enzymes in skeletal muscle. We hypothesized that activation of the p38 MAPK (mitogen-activated protein kinase) in response to exercise was associated with exercise-induced PGC-1{alpha} and respiratory enzymes expression and aimed to demonstrate this under the physiological level. We subjected mice to a single bout of treadmill running and found that the exercise induced a biphasic increase in the expression of respiratory enzymes mRNA. The second phase of the increase was accompanied by an increase in PGC-1{alpha} protein, but the other was not. Administration of SB203580 (SB), an inhibitor ofmore » p38 MAPK, suppressed the increase in PGC-1{alpha} expression and respiratory enzymes mRNA in both phases. These data suggest that p38 MAPK is associated with the exercise-induced expression of PGC-1{alpha} and biphasic increase in respiratory enzyme mRNAs in mouse skeletal muscle under physiological conditions.« less

Occurrence of amylose-lipid complexes in teff and maize starch biphasic pastes.

PubMed

Wokadala, Obiro Cuthbert; Ray, Suprakas Sinha; Emmambux, Mohammad Naushad

2012-09-01

The occurrence of amylose-lipid complexes was determined in maize and teff starch biphasic pastes i.e. peak viscosity pastes at short and prolonged pasting times. Maize and teff starches were pasted for 11.5 and 130 min with or without added stearic acid followed by thermo-stable alpha-amylase hydrolysis in a rapid visco-analyzer. X-ray diffraction analysis of pastes before and residues after hydrolysis showed crystalline V-amylose diffraction patterns for the starches pasted for a prolonged time with added stearic acid while less distinct V-amylose patterns with non-complexed stearic acid peaks were observed with a short pasting time. Differential scanning calorimetry of pastes before and residues after paste hydrolysis showed that Type I amylose-lipid complexes were formed after pasting for the short duration with added stearic acid, while Type II complexes are formed after pasting for the prolonged time. The present research provides evidence that amylose-lipid complexes play an important role in starch biphasic pasting. Copyright © 2012 Elsevier Ltd. All rights reserved.

Origin and Correction of Magnetic Field Inhomogeneity at the Interface in Biphasic NMR Samples

PubMed Central

Martin, Bryan T.; Chingas, G. C.

2012-01-01

The use of susceptibility matching to minimize spectral distortion of biphasic samples layered in a standard 5 mm NMR tube is described. The approach uses magic angle spinning (MAS) to first extract chemical shift differences by suppressing bulk magnetization. Then, using biphasic coaxial samples, magnetic susceptibilities are matched by titration with a paramagnetic salt. The matched phases are then layered in a standard NMR tube where they can be shimmed and examined. Line widths of two distinct spectral lines, selected to characterize homogeneity in each phase, are simultaneously optimized. Two-dimensional distortion-free, slice-resolved spectra of an octanol/water system illustrate the method. These data are obtained using a 2D stepped-gradient pulse sequence devised for this application. Advantages of this sequence over slice-selective methods are that acquisition efficiency is increased and processing requires only conventional software. PMID:22459062

Subcellular localization of calcium deposits in the noble crayfish Astacus astacus spermatophore: Implications for post-mating spermatophore hardening and spermatozoon maturation.

PubMed

Niksirat, Hamid; Kouba, Antonín

2016-04-01

The freshly ejaculated spermatophore of crayfish undergoes a hardening process during post-mating storage on the body surface of female. The ultrastructural distribution of calcium deposits were studied and compared in freshly ejaculated and post-mating noble crayfish spermatophores, using the oxalate-pyroantimonate technique, to determine possible roles of calcium in post-mating spermatophore hardening and spermatozoon maturation. Small particles of sparsely distributed calcium deposits were visible in the wall of freshly ejaculated spermatophore. Also, large amount of calcium deposits were visible in the membranes of the freshly ejaculated spermatozoon. Five minutes post-ejaculation, granules in the spermatophore wall appeared as porous formations with numerous electron lucent spaces. Calcium deposits were visible within the spaces and scattered in the spermatophore wall matrix, where smaller calcium deposits combined to form globular calcium deposits. Large numbers of the globular calcium deposits were visible in the wall of the post-mating spermatophore. Smaller calcium deposits were detected in the central area of post-mating spermatophore, which contains the sperm mass, and in the extracellular matrix and capsule. While the density of calcium deposits decreased in the post-mating spermatozoon membranes, numerous small calcium deposits appeared in the subacrosomal zone and nucleus. Substantial changes in calcium deposit distribution in the crayfish spermatophore during post-mating storage on the body of female may be involved in the processes of the spermatophore hardening and spermatozoon maturation. © 2016 Wiley Periodicals, Inc.

Elemental calcium intake associated with calcium acetate/calcium carbonate in the treatment of hyperphosphatemia

PubMed Central

Wilson, Rosamund J; Copley, J Brian

2017-01-01

Background Calcium-based and non-calcium-based phosphate binders have similar efficacy in the treatment of hyperphosphatemia; however, calcium-based binders may be associated with hypercalcemia, vascular calcification, and adynamic bone disease. Scope A post hoc analysis was carried out of data from a 16-week, Phase IV study of patients with end-stage renal disease (ESRD) who switched to lanthanum carbonate monotherapy from baseline calcium acetate/calcium carbonate monotherapy. Of the intent-to-treat population (N=2520), 752 patients with recorded dose data for calcium acetate (n=551)/calcium carbonate (n=201) at baseline and lanthanum carbonate at week 16 were studied. Elemental calcium intake, serum phosphate, corrected serum calcium, and serum intact parathyroid hormone levels were analyzed. Findings Of the 551 patients with calcium acetate dose data, 271 (49.2%) had an elemental calcium intake of at least 1.5 g/day at baseline, and 142 (25.8%) had an intake of at least 2.0 g/day. Mean (95% confidence interval [CI]) serum phosphate levels were 6.1 (5.89, 6.21) mg/dL at baseline and 6.2 (6.04, 6.38) mg/dL at 16 weeks; mean (95% CI) corrected serum calcium levels were 9.3 (9.16, 9.44) mg/dL and 9.2 (9.06, 9.34) mg/dL, respectively. Of the 201 patients with calcium carbonate dose data, 117 (58.2%) had an elemental calcium intake of at least 1.5 g/day, and 76 (37.8%) had an intake of at least 2.0 g/day. Mean (95% CI) serum phosphate levels were 5.8 (5.52, 6.06) mg/dL at baseline and 5.8 (5.53, 6.05) mg/dL at week 16; mean (95% CI) corrected serum calcium levels were 9.7 (9.15, 10.25) mg/dL and 9.2 (9.06, 9.34) mg/dL, respectively. Conclusion Calcium acetate/calcium carbonate phosphate binders, taken to control serum phosphate levels, may result in high levels of elemental calcium intake. This may lead to complications related to calcium balance. PMID:28182142

Effect of molecular weight of hyaluronic acid (HA) on viscoelasticity and particle texturing feel of HA dermal biphasic fillers.

PubMed

Chun, Cheolbyong; Lee, Deuk Yong; Kim, Jin-Tae; Kwon, Mi-Kyung; Kim, Young-Zu; Kim, Seok-Soon

2016-01-01

Hyaluronic acid (HA) dermal biphasic fillers are synthesized for their efficacy in correcting aesthetic defects such as wrinkles, scars and facial contouring defects. The fillers consist of crosslinked HA microspheres suspended in a noncrosslinked HA. To extend the duration of HAs within the dermis and obtain the particle texturing feel, HAs are crosslinked to obtain the suitable mechanical properties. Hyaluronic acid (HA) dermal biphasic fillers are prepared by mixing the crosslinked HA microspheres and the noncrosslinked HAs. The elastic modulus of the fillers increased with raising the volume fraction of the microspheres. The mechanical properties and the particle texturing feel of the fillers made from crosslinked HA (1058 kDa) microspheres suspended in noncrosslinked HA (1368 kDa) are successfully achieved, which are adequate for the fillers. Dermal biphasic HA fillers made from 1058 kDa exhibit suitable elastic moduli (211 to 420 Pa) and particle texturing feel (scale 7 ~ 9).

Steroid biotransformations in biphasic systems with Yarrowia lipolytica expressing human liver cytochrome P450 genes

PubMed Central

2012-01-01

Background Yarrowia lipolytica efficiently metabolizes and assimilates hydrophobic compounds such as n-alkanes and fatty acids. Efficient substrate uptake is enabled by naturally secreted emulsifiers and a modified cell surface hydrophobicity and protrusions formed by this yeast. We were examining the potential of recombinant Y. lipolytica as a biocatalyst for the oxidation of hardly soluble hydrophobic steroids. Furthermore, two-liquid biphasic culture systems were evaluated to increase substrate availability. While cells, together with water soluble nutrients, are maintained in the aqueous phase, substrates and most of the products are contained in a second water-immiscible organic solvent phase. Results For the first time we have co-expressed the human cytochromes P450 2D6 and 3A4 genes in Y. lipolytica together with human cytochrome P450 reductase (hCPR) or Y. lipolytica cytochrome P450 reductase (YlCPR). These whole-cell biocatalysts were used for the conversion of poorly soluble steroids in biphasic systems. Employing a biphasic system with the organic solvent and Y. lipolytica carbon source ethyl oleate for the whole-cell bioconversion of progesterone, the initial specific hydroxylation rate in a 1.5 L stirred tank bioreactor was further increased 2-fold. Furthermore, the product formation was significantly prolonged as compared to the aqueous system. Co-expression of the human CPR gene led to a 4-10-fold higher specific activity, compared to the co-overexpression of the native Y. lipolytica CPR gene. Multicopy transformants showed a 50-70-fold increase of activity as compared to single copy strains. Conclusions Alkane-assimilating yeast Y. lipolytica, coupled with the described expression strategies, demonstrated its high potential for biotransformations of hydrophobic substrates in two-liquid biphasic systems. Especially organic solvents which can be efficiently taken up and/or metabolized by the cell might enable more efficient bioconversion as compared

Mammary-Specific Ablation of the Calcium-Sensing Receptor During Lactation Alters Maternal Calcium Metabolism, Milk Calcium Transport, and Neonatal Calcium Accrual

PubMed Central

Mamillapalli, Ramanaiah; VanHouten, Joshua; Dann, Pamela; Bikle, Daniel; Chang, Wenhan; Brown, Edward

2013-01-01

To meet the demands for milk calcium, the lactating mother adjusts systemic calcium and bone metabolism by increasing dietary calcium intake, increasing bone resorption, and reducing renal calcium excretion. As part of this adaptation, the lactating mammary gland secretes PTHrP into the maternal circulation to increase bone turnover and mobilize skeletal calcium stores. Previous data have suggested that, during lactation, the breast relies on the calcium-sensing receptor (CaSR) to coordinate PTHrP secretion and milk calcium transport with calcium availability. To test this idea genetically, we bred BLG-Cre mice with CaSR-floxed mice to ablate the CaSR specifically from mammary epithelial cells only at the onset of lactation (CaSR-cKO mice). Loss of the CaSR in the lactating mammary gland did not disrupt alveolar differentiation or milk production. However, it did increase the secretion of PTHrP into milk and decreased the transport of calcium from the circulation into milk. CaSR-cKO mice did not show accelerated bone resorption, but they did have a decrease in bone formation. Loss of the mammary gland CaSR resulted in hypercalcemia, decreased PTH secretion, and increased renal calcium excretion in lactating mothers. Finally, loss of the mammary gland CaSR resulted in decreased calcium accrual by suckling neonates, likely due to the combination of increased milk PTHrP and decreased milk calcium. These results demonstrate that the mammary gland CaSR coordinates maternal bone and calcium metabolism, calcium transport into milk, and neonatal calcium accrual during lactation. PMID:23782944

BMP-7 Preserves Surface Integrity of Degradable-ceramic Cranioplasty in a Göttingen Minipig Model

PubMed Central

Schulz, Peter; Klünter, Tim; Deisinger, Ulrike; Diez, Claudius; Waiss, Waltraud; Kirschneck, Christian; Reichert, Torsten E.; Detsch, Rainer

2017-01-01

Background: The aim of the study was to evaluate the integrity of a craniotomy grafted site in a minipig model using different highly porous calcium phosphate ceramic scaffolds either loaded or nonloaded with bone morphogenetic protein-7 (BMP-7). Methods: Four craniotomies with a diameter of 15 mm (critical-size defect) were grafted with different highly porous (92–94 vol%) calcium phosphate ceramics [hydroxyapatite (HA), tricalcium phosphate (TCP), and biphasic calcium phosphate (BCP; a mixture of HA and TCP)] in 10 Göttingen minipigs: (a) group I (n = 5): HA versus BCP; (b) group II (n = 5): TCP versus BCP. One scaffold of each composition was supplied with 250 μg of BMP-7. In vivo computed tomography scan and fluorochrome bone labeling were performed. Specimens were evaluated 14 weeks after surgery by environmental scanning electron microscopy, fluorescence microscopy, and Giemsa staining histology. Results: BMP-7 significantly enhanced bone formation in TCP (P = 0.047). Slightly enhanced bone formation was observed in BCP (P = 0.059) but not in HA implants. BMP-7 enhanced ceramic degradation in TCP (P = 0.05) and BCP (P = 0.05) implants but not in HA implants. Surface integrity of grafted site was observed in all BMP-7-loaded implants after successful creeping substitution by the newly formed bone. In 9 of 10 HA implants without BMP-7, partial collapse of the implant site was observed. All TCP implants without BMP-7 collapsed. Fluorescent labeling showed bone formation at week 1 in BMP-7-stimulated implants. Conclusions: BMP-7 supports bone formation, ceramic degradation, implant integration, and surface integrity of the grafted site. PMID:28458969

Clinical experience with biphasic insulin aspart in people with type 2 diabetes: Results from the Libya cohort of the A1chieve study.

PubMed

Hajjaji, Issam M; Sherif, Ibrahim; Elazrag, Aisha; Jaber, Suhair; Chakkarwar, Praful N; Eltabal, Salem

2013-11-01

The A1chieve, a multicentric (28 countries), 24-week, non-interventional study evaluated the safety and effectiveness of insulin detemir, biphasic insulin aspart and insulin aspart in people with T2DM (n = 66,726) in routine clinical care across four continents. Data was collected at baseline, at 12 weeks and at 24 weeks. This short communication presents the results for patients enrolled in biphasic insulin aspart sub group from Libya. A total of 179 patients were enrolled in the biphasic insulin aspart subgroup. All the patients were prior insulin users. At baseline glycaemic control was poor (mean HbA1c: 9.3%). After 24 weeks of treatment there was an improvement in HbA1c (-0.9%). Hypoglycaemic events reduced from 7.2 events/patient-year to 3.7 events/patient-year in 24 weeks. SADRs did not occur in any of the study patients. Starting or switching to biphasic insulin aspart was associated with improvement in glycaemic control with a low rate of hypoglycaemia.

Photochromism of 7-(N,N-diethylamino)-4'-hydroxyflavylium in a water-ionic liquid biphasic system.

PubMed

Pina, Fernando; Parola, A Jorge; Melo, Maria João; Laia, César A T; Afonso, Carlos A M

2007-04-28

Photochromism of trans-4-(N,N-diethylamino)-2,4'-dihydroxychalcone, with formation of the photoproduct 7-(N,N-diethylamino)-4'-hydroxyflavylium, is promoted in the ionic liquid phase of a water/[bmim][PF6] biphasic system.

Safety and effectiveness of biphasic insulin aspart 30 in people with type 2 diabetes switching from basal-bolus insulin regimens in the A1chieve study.

PubMed

Dieuzeide, Guillermo; Chuang, Lee-Ming; Almaghamsi, Abdulrahman; Zilov, Alexey; Chen, Jian-Wen; Lavalle-González, Fernando J

2014-07-01

Biphasic insulin aspart 30 allows fewer daily injections versus basal-bolus insulin regimens, which may improve adherence and treatment outcome. This sub-analysis of the observational A1chieve study assessed clinical safety and effectiveness of biphasic insulin aspart 30 in people with type 2 diabetes previously receiving basal-bolus insulin regimens. A1chieve was an international, open-label, 24-week study in people with type 2 diabetes starting/switching to biphasic insulin aspart 30, insulin detemir or insulin aspart. This sub-analysis assessed patients switching from insulin glargine- or neutral protamine Hagedorn insulin-based basal-bolus insulin regimens to biphasic insulin aspart 30. 1024 patients were included. At 24 weeks, glycated haemoglobin and fasting plasma glucose were significantly reduced from baseline in both cohorts (all p<0.001). The proportion reporting any hypoglycaemia, major hypoglycaemia or nocturnal hypoglycaemia was significantly reduced after 24 weeks (all p<0.05). No serious adverse drug reactions were reported. Both cohorts had significantly improved health-related quality of life (HRQoL; p<0.001). 24 weeks after switching from basal-bolus insulin regimens to biphasic insulin aspart 30, glycaemic control and HRQoL were significantly improved, and hypoglycaemia was significantly reduced. This suggests that people with type 2 diabetes inadequately controlled on basal-bolus insulin regimens can consider biphasic insulin aspart 30. Copyright © 2013 Primary Care Diabetes Europe. Published by Elsevier Ltd. All rights reserved.

Surface modification using the biomimetic method in alumina-zirconia porous ceramics obtained by the replica method.

PubMed

Silva, André D R; Rigoli, Willian R; Osiro, Denise; Mello, Daphne C R; Vasconcellos, Luana M R; Lobo, Anderson O; Pallone, Eliria M J A

2018-01-12

The modification of biomaterials approved by the Food and Drug Administration could be an alternative to reduce the period of use in humans. Porous bioceramics are widely used as support structures for bone formation and repair. This composite has essential characteristics for an implant, including good mechanical properties, high chemical stability, biocompatibility and adequate aesthetic appearance. Here, three-dimensional porous scaffolds of Al 2 O 3 containing 5% by volume of ZrO 2 were produced by the replica method. These scaffolds had their surfaces chemically treated with phosphoric acid and were coated with calcium phosphate using the biomimetic method simulated body fluid (SBF, 5×) for 14 days. The scaffolds, before and after biomimetic coating, were characterized mechanically, morphologically and structurally by axial compression tests, scanning electron microscopy, microtomography, apparent porosity, X-ray diffractometry, near-infrared spectroscopy, inductively coupled plasma optical emission spectroscopy, energy dispersive X-ray spectroscopy and reactivity. The in vitro cell viability and formation of mineralization nodules were used to identify the potential for bone regeneration. The produced scaffols after immersion in SBF were able to induce the nodules formation. These characteristics are advantaged by the formation of different phases of calcium phosphates on the material surface in a reduced incubation period. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2018. © 2018 Wiley Periodicals, Inc.

Development of bioactive porous α-TCP/HAp beads for bone tissue engineering.

PubMed

Asaoka, Teruo; Ohtake, Shoji; Furukawa, Katsuko S; Tamura, Akito; Ushida, Takashi

2013-11-01

Porous beads of bioactive ceramics such as hydroxyapatite (HAp) and tribasic calcium phosphate (TCP) are considered a promising scaffold for cultivating bone cells. To realize this, α-TCP/HAp functionally graded porous beads are fabricated with two main purposes: to maintain the function of the scaffold with sufficient strength up to the growth of new bone, and is absorbed completely after the growth. HAp is a bioactive material that has both high strength and strong tissue-adhesive properties, but is not readily absorbed by the human body. On the contrary, α-TCP is highly bioabsorbable, resulting in a scaffold that is absorbed before it is completely replaced by bone. In this study, we produced porous, bead-shaped carriers as scaffolds for osteoblast culture. To control the solubility in vivo, the fabricated beads contained α-TCP at the center and HAp at the surface. Cell adaptability of these beads for bone tissue engineering was confirmed in vitro. It was found that α-TCP/HAp bead carriers exhibit low toxicity in the initial stages of cell seeding and cell adhesion. The presence of HAp in the composite bead form effectively increased ALP activity. In conclusion, it is suggested that these newly developed α-TCP/HAp beads are a promising tool for bone tissue engineering. Copyright © 2013 Wiley Periodicals, Inc.

Biphasic growth of orbital volume in Chinese children.

PubMed

Wei, Nan; Bi, Hua; Zhang, Bin; Li, Xue; Sun, Fengyuan; Qian, Xuehan

2017-09-01

The aim of this study was to map out the developmental curve of the orbital volume of Chinese children aged 1-15 years. CT scanning was performed on 109 children and the orbital volume, interlateral orbital rim distance (IORD), and extent of exophthalmos were measured on the CT images and plotted against age. The development of the orbit structure followed a biphasic pattern. The first growth phase was before 3 years and the second growth phase was between 7 years and 12 years of age. The growth speed in the first phase was about 3 times that of the second one (first vs second phase: 2.28 cm 3 /year vs 0.67 cm 3 /year for orbital volume, 5.01 mm/year vs 1.57 mm/year for IORD, 1.29 mm/year vs 0.42 mm/year for the exophthalmos). During development, there was no significant difference between the left and right orbits. There was no significant difference between boys and girls before 12 years of age. However, after 12 years of age, boys had significantly larger orbital volumes (22.16±2.28 cm 3 /year vs 18.57±1.16 cm 3 /year, p<0.001) and a greater IORD (96.29±3.18 mm/year vs 91.00±4.54 mm/year, p<0.001) than girls. In Chinese children, the development of orbital volume follows a biphasic pattern and a sex difference becomes significant after the age of 12 years. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

Calcium

MedlinePlus

... You'll also find calcium in broccoli and dark green, leafy vegetables (especially collard and turnip greens, ... can enjoy good sources of calcium such as dark green, leafy vegetables, broccoli, chickpeas, and calcium-fortified ...

Application of aqueous biphasic systems as strategy to purify tannase from Aspergillus tamarii URM 7115.

PubMed

de Sena, Amanda Reges; Barros Oliveira, Flávio Manoel; Campos Leite, Tonny Cley; Evaristo da Silva Nascimento, Talita Camila; Moreira, Keila Aparecida; de Assis, Sandra Aparecida

2017-10-21

The aims of the current study are to assess the influence of polyethylene glycol (PEG) concentration, molar mass, pH, and citrate concentrations on aqueous biphasic systems based on 2 4 factorial designs, as well as to check their capacity to purify tannase secreted by Aspergillus tamarii URM 7115. Tannase was produced through submerged fermentation at 26°C for 67 h in Czapeck-Dox modified broth and added with yeast extract and tannic acid. The factorial design was followed to assess the influence of PEG molar mass (M PEG 600; 4,000 and 8,000 g/ mol), and PEG (C PEG 20.0; 22.0 and 24.0% w/w) and citrate concentrations (C CIT 15.0, 17.5, and 20.0%, w/w), as well as of pH (6.0, 7.0, and 8.0) on the response variables; moreover, partition coefficient (K), yield (Y), and purification factor (PF) were analyzed. The most suitable parameters to purify tannase secreted by A. tamarii URM 7115 through a biphasic system were 600 (g/mol) M PEG , 24% (w/w) C PEG , 15% (w/w) C CIT at pH 6.0 and they resulted in 6.33 enzyme partition, 131.25% yield, 19.80 purification factor and 195.08 selectivity. Tannase secreted by A. tamarii URM 7115 purified through aqueous biphasic systems composed of PEG/citrate can be used for industrial purposes, since it presents suitable purification factor and yield.

A Human Clinical, Histological, Histomorphometrical, and Radiographical Study on Biphasic HA-Beta-TCP 30/70 in Maxillary Sinus Augmentation.

PubMed

Mangano, Carlo; Sinjari, Bruna; Shibli, Jamil A; Mangano, Francesco; Hamisch, Sabine; Piattelli, Adriano; Perrotti, Vittoria; Iezzi, Giovanna

2015-06-01

By mixing hydroxyapatite (HA) and tricalcium phosphate (TCP), biphasic calcium phosphate ceramics can be obtained, and by varying their ratio it is possible to tailor the characteristics of the biomaterial. The aim of the present human study was to evaluate the histological and radiographical aspects of bone formation in maxillary sinus augmentation using a 30/70 HA-beta-TCP with a reticular structure. A total of 12 patients, undergoing two-stage sinus augmentation procedure using HA-beta-TCP at a ratio of 30/70, were included in the present study. After a 6-month healing period, during implant insertion, radiographical analysis was performed, and then the bone core biopsies were harvested and processed for histology. At radiographic evaluation, the bone gain was on average 6.85 ± 0.60 mm. HA-beta-TCP 30/70 appeared to be lined by newly formed bone, with no gaps at the interface. The histomorphometric analysis revealed 26 ± 2% of residual grafted biomaterial, 29 ± 3% of newly formed bone, and 45 ± 2% of marrow spaces. The present results indicate histologically the high biocompatibility and osteoconductivity of HA-beta-TCP 30/70, and clinically its successful use for sinus augmentation procedures. © 2013 Wiley Periodicals, Inc.

A promising tritium breeding material: Nanostructured 2Li2TiO3-Li4SiO4 biphasic ceramic pebbles

NASA Astrophysics Data System (ADS)

Dang, Chen; Yang, Mao; Gong, Yichao; Feng, Lan; Wang, Hailiang; Shi, Yanli; Shi, Qiwu; Qi, Jianqi; Lu, Tiecheng

2018-03-01

As an advanced tritium breeder material for the fusion reactor blanket of the International Thermonuclear Experimental Reactor (ITER), Li2TiO3-Li4SiO4 biphasic ceramic has attracted widely attention due to its merits. In this paper, the uniform precursor powders were prepared by hydrothermal method, and nanostructured 2Li2TiO3-Li4SiO4 biphasic ceramic pebbles were fabricated by an indirect wet method at the first time. In addition, the composition dependence (x/y) of their microstructure characteristics and mechanical properties were investigated. The results indicated that the crush load of biphasic ceramic pebbles was better than that of single phase ceramic pebbles under identical conditions. The 2Li2TiO3-Li4SiO4 ceramic pebbles have good morphology, small grain size (90 nm), satisfactory crush load (37.8 N) and relative density (81.8 %T.D.), which could be a promising breeding material in the future fusion reactor.

Formation of a Fluorous/Organic Biphasic Supramolecular Octopus Assembly for Enhanced Porphyrin Phosphorescence in Air

DOE PAGES

Yang, Chi; Arvapally, Ravi K.; Tekarli, Sammer M.; ...

2015-03-03

The trinuclear triangle-shaped system [tris{3,5-bis(heptafluoropropyl)-1,2,4-triazolatosilver(I)}] (1) and the multi-armed square-shaped metalloporphyrin PtOEP or the free porphyrin base H2OEP serve as excellent octopus hosts (OEP=2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphine). Coupling of the fluorous/organic molecular octopi 1 and H2OEP or PtOEP by strong quadrupole-quadrupole and metal- interactions affords the supramolecular assemblies [1PtOEP] or [1H(2)OEP] (2a), which feature nanoscopic cavities surrounding the upper triangular and lower square cores. The fluorous/organic biphasic configuration of [1PtOEP] leads to an increase in the phosphorescence of PtOEP under ambient conditions. Guest molecules can be included in the biphasic double-octopus assembly in three different site-selective modes.

Aqueous biphasic extraction of uranium and thorium from contaminated soils. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chaiko, D.J.; Gartelmann, J.; Henriksen, J.L.

1995-07-01

The aqueous biphasic extraction (ABE) process for soil decontamination involves the selective partitioning of solutes and fine particulates between two immiscible aqueous phases. The biphase system is generated by the appropriate combination of a water-soluble polymer (e.g., polyethlene glycol) with an inorganic salt (e.g., sodium carbonate). Selective partitioning results in 99 to 99.5% of the soil being recovered in the cleaned-soil fraction, while only 0.5 to 1% is recovered in the contaminant concentrate. The ABE process is best suited to the recovery of ultrafine, refractory material from the silt and clay fractions of soils. During continuous countercurrent extraction tests withmore » soil samples from the Fernald Environmental Management Project site (Fernald, OH), particulate thorium was extracted and concentrated between 6- and 16-fold, while the uranium concentration was reduced from about 500 mg/kg to about 77 mg/kg. Carbonate leaching alone was able to reduce the uranium concentration only to 146 mg/kg. Preliminary estimates for treatment costs are approximately $160 per ton of dry soil. A detailed flowsheet of the ABE process is provided.« less

Porous Shape Memory Polymers

PubMed Central

Hearon, Keith; Singhal, Pooja; Horn, John; Small, Ward; Olsovsky, Cory; Maitland, Kristen C.; Wilson, Thomas S.; Maitland, Duncan J.

2013-01-01

Porous shape memory polymers (SMPs) include foams, scaffolds, meshes, and other polymeric substrates that possess porous three-dimensional macrostructures. Porous SMPs exhibit active structural and volumetric transformations and have driven investigations in fields ranging from biomedical engineering to aerospace engineering to the clothing industry. The present review article examines recent developments in porous SMPs, with focus given to structural and chemical classification, methods of characterization, and applications. We conclude that the current body of literature presents porous SMPs as highly interesting smart materials with potential for industrial use. PMID:23646038

Method for separating water soluble organics from a process stream by aqueous biphasic extraction

DOEpatents

Chaiko, David J.; Mego, William A.

1999-01-01

A method for separating water-miscible organic species from a process stream by aqueous biphasic extraction is provided. An aqueous biphase system is generated by contacting a process stream comprised of water, salt, and organic species with an aqueous polymer solution. The organic species transfer from the salt-rich phase to the polymer-rich phase, and the phases are separated. Next, the polymer is recovered from the loaded polymer phase by selectively extracting the polymer into an organic phase at an elevated temperature, while the organic species remain in a substantially salt-free aqueous solution. Alternatively, the polymer is recovered from the loaded polymer by a temperature induced phase separation (cloud point extraction), whereby the polymer and the organic species separate into two distinct solutions. The method for separating water-miscible organic species is applicable to the treatment of industrial wastewater streams, including the extraction and recovery of complexed metal ions from salt solutions, organic contaminants from mineral processing streams, and colorants from spent dye baths.

Design and development of a low-cost biphasic charge-balanced functional electric stimulator and its clinical validation.

PubMed

Shendkar, Chandrashekhar; Lenka, Prasanna K; Biswas, Abhishek; Kumar, Ratnesh; Mahadevappa, Manjunatha

2015-10-01

Functional electric stimulators that produce near-ideal, charge-balanced biphasic stimulation waveforms with interphase delay are considered safer and more efficacious than conventional stimulators. An indigenously designed, low-cost, portable FES device named InStim is developed. It features a charge-balanced biphasic single channel. The authors present the complete design, mathematical analysis of the circuit and the clinical evaluation of the device. The developed circuit was tested on stroke patients affected by foot drop problems. It was tested both under laboratory conditions and in clinical settings. The key building blocks of this circuit are low dropout regulators, a DC-DC voltage booster and a single high-power current source OP-Amp with current-limiting capabilities. This allows the device to deliver high-voltage, constant current, biphasic pulses without the use of a bulky step-up transformer. The advantages of the proposed design over the currently existing devices include improved safety features (zero DC current, current-limiting mechanism and safe pulses), waveform morphology that causes less muscle fatigue, cost-effectiveness and compact power-efficient circuit design with minimal components. The device is also capable of producing appropriate ankle dorsiflexion in patients having foot drop problems of various Medical Research Council scale grades.

Utilisation of steel furnace slag coarse aggregate in a low calcium fly ash geopolymer concrete

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khan, M. S.H.,; Castel, Arnaud; Akbarnezhad, A.

This paper evaluates the performance of steel furnace slag (SFS) coarse aggregate in blended slag and low calcium fly ash geopolymer concrete (GPC). The geopolymer binder is composed of 90% of low calcium fly ash and 10% of ground granulated blast furnace slag (GGBFS). Mechanical and physical properties, shrinkage, and detailed microstructure analysis were carried out. The results showed that geopolymer concrete with SFS aggregate offered higher compressive strength, surface resistivity and pulse velocity than that of GPC with traditional aggregate. The shrinkage results showed no expansion or swelling due to delayed calcium oxide (CaO) hydration after 320 days. Nomore » traditional porous interfacial transition zone (ITZ) was detected using scanning electron microscopy, indicating a better bond between SFS aggregate and geopolymer matrix. Energy dispersive spectroscopy results further revealed calcium (Ca) diffusion at the vicinity of ITZ. Raman spectroscopy results showed no new crystalline phase formed due to Ca diffusion. X-ray fluorescence result showed Mg diffusion from SFS aggregate towards geopolymer matrix. The incorporation of Ca and Mg into the geopolymer structure and better bond between SFS aggregate and geopolymer matrix are the most likely reasons for the higher compressive strength observed in GPC with SFS aggregate.« less

Ru-Catalyzed Estragole Isomerization under Homogeneous and Ionic Liquid Biphasic Conditions

PubMed Central

2017-01-01

The isomerization of estragole to trans-anethole is an important reaction and is industrially performed using an excess of NaOH or KOH in ethanol at high temperatures with very low selectivity. Simple Ru-based transition-metal complexes, under homogeneous, ionic liquid (IL)-supported (biphasic) and “solventless” conditions, can be used for this reaction. The selectivity of this reaction is more sensitive to the solvent/support used than the ligands associated with the metal catalyst. Thus, under the optimized reaction conditions, 100% conversion can be achieved in the estragole isomerization, using as little as 4 × 10–3 mol % (40 ppm) of [RuHCl(CO)(PPh3)3] in toluene, reflecting a total turnover number (TON) of 25 000 and turnover frequencies (TOFs) of up to 500 min–1 at 80 °C. Using a dimeric Ru precursor, [RuCl(μ-Cl)(η3:η3-C10H16)]2, in ethanol associated with P(OEt)3, a TON of 10 000 and a TOF of 125 min–1 are obtained with 100% conversion and 99% selectivity. These two Ru catalytic systems can be transposed to biphasic IL systems by using ionic-tagged P-ligands such as 1-(3-(diphenylphosphanyl)propyl)-2,3-dimethylimidazolium bis(trifluoromethanesulfonyl)imide immobilized in 1-(3-hydroxypropyl)-2,3-dimethylimidazolium bis(trifluoromethanesulfonyl) imide with up to 99% selectivity and almost complete estragole conversion. However, the reaction is much slower than that performed under solventless or homogeneous conditions. The use of ionic-tagged ligands significantly reduces the Ru leaching to the organic phase, compared to that in reactions performed under homogeneous conditions, where the catalytic system loses catalytic performance after the second recycling. Detailed kinetic investigations of the reaction catalyzed by [RuHCl(CO)(PPh3)3] indicate that a simplified kinetic model (a monomolecular reversible first-order reaction) is adequate for fitting the homogeneous reaction at 80 °C and under biphasic conditions. However, the kinetics of

Atomically resolved calcium phosphate coating on a gold substrate.

PubMed

Metoki, Noah; Baik, Sung-Il; Isheim, Dieter; Mandler, Daniel; Seidman, David N; Eliaz, Noam

2018-05-10

Some articles have revealed that the electrodeposition of calcium phosphate (CaP) coatings entails a precursor phase, similarly to biomineralization in vivo. The chemical composition of the initial layer and its thickness are, however, still arguable, to the best of our knowledge. Moreover, while CaP and electrodeposition of metal coatings have been studied utilizing atom-probe tomography (APT), the electrodeposition of CaP ceramics has not been heretofore studied. Herein, we present an investigation of the CaP deposition on a gold substrate. Using APT and transmission electron microscopy (TEM) it is found that a mixture of phases, which could serve as transient precursor phases to hydroxyapatite (HAp), can be detected. The thickness of these phases is tens of nanometers, and they consist of amorphous CaP (ACP), dibasic calcium phosphate dihydrate (DCPD), and octacalcium phosphate (OCP). This demonstrates the value of using atomic-resolved characterization techniques for identifying the precursor phases. It also indicates that the kinetics of their transformation into the more stable HAp is not too fast to enable their observation. The coating gradually displays higher Ca/P atomic ratios, a porous nature, and concomitantly a change in its density.

Graphene Oxide-Copper Nanocomposite-Coated Porous CaP Scaffold for Vascularized Bone Regeneration via Activation of Hif-1α.

PubMed

Zhang, Wenjie; Chang, Qing; Xu, Ling; Li, Guanglong; Yang, Guangzheng; Ding, Xun; Wang, Xiansong; Cui, Daxiang; Jiang, Xinquan

2016-06-01

Graphene has been studied for its in vitro osteoinductive capacity. However, the in vivo bone repair effects of graphene-based scaffolds remain unknown. The aqueous soluble graphene oxide-copper nanocomposites (GO-Cu) are fabricated, which are used to coat porous calcium phosphate (CaP) scaffolds for vascularized bone regeneration. The GO-Cu nanocomposites, containing crystallized CuO/Cu2 O nanoparticles of ≈30 nm diameters, distribute uniformly on the surfaces of the porous scaffolds and maintain a long-term release of Cu ions. In vitro, the GO-Cu coating enhances the adhesion and osteogenic differentiation of rat bone marrow stem cells (BMSCs). It is also found that by activating the Erk1/2 signaling pathway, the GO-Cu nanocomposites upregulate the expression of Hif-1α in BMSCs, resulting in the secretion of VEGF and BMP-2 proteins. When transplanted into rat with critical-sized calvarial defects, the GO-Cu-coated calcium phosphate cement (CPC) scaffolds (CPC/GO-Cu) significantly promote angiogenesis and osteogenesis. Moreover, it is observed via histological sections that the GO-Cu nanocomposites are phagocytosed by multinucleated giant cells. The results suggest that GO-Cu nanocomposite coatings can be utilized as an attractive strategy for vascularized bone regeneration. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Characterization of Biogenic Gas and Mineral Formation Process by Denitrification in Porous Media

NASA Astrophysics Data System (ADS)

Hall, C. A.; Kim, D.; Mahabadi, N.; van Paassen, L. A.

2017-12-01

Biologically mediated processes have been regarded and developed as an alternative approach to traditional ground improvement techniques. Denitrification has been investigated as a potential ground improvement process towards liquefaction hazard mitigation. During denitrification, microorganisms reduce nitrate to dinitrogen gas and facilitate calcium carbonate precipitation as a by-product under adequate environmental conditions. The formation of dinitrogen gas desaturates soils and allows for potential pore pressure dampening during earthquake events. While, precipitation of calcium carbonate can improve the mechanical properties by filling the voids and cementing soil particles. As a result of small changes in gas and mineral phases, the mechanical properties of soils can be significantly affected. Prior research has primarily focused on quantitative analysis of overall residual calcium carbonate mineral and biogenic gas products in lab-scale porous media. However, the distribution of these products at the pore-scale has not been well-investigated. In this research, denitrification is activated in a microfluidic chip simulating a homogenous pore structure. The denitrification process is monitored by sequential image capture, where gas and mineral phase changes are evaluated by image processing. Analysis of these images correspond with previous findings, which demonstrate that biogenic gas behaviour at the pore scale is affected by the balance between reaction, diffusion, and convection rates.

21 CFR 172.330 - Calcium pantothenate, calcium chloride double salt.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Calcium pantothenate, calcium chloride double salt... FOOD FOR HUMAN CONSUMPTION Special Dietary and Nutritional Additives § 172.330 Calcium pantothenate, calcium chloride double salt. The food additive calcium chloride double salt of calcium pantothenate may...

Short-term effects of mineral particle sizes on cellular degradation activity after implantation of injectable calcium phosphate biomaterials and the consequences for bone substitution.

PubMed

Gauthier, O; Bouler, J M; Weiss, P; Bosco, J; Aguado, E; Daculsi, G

1999-08-01

This in vivo study investigated the influence of two calcium phosphate particle sizes (40-80 microm and 200-500 microm) on the cellular degradation activity associated with the bone substitution process of two injectable bone substitutes (IBS). The tested biomaterials were obtained by associating a biphasic calcium phosphate (BCP) ceramic mineral phase and a 3% aqueous solution of a cellulosic polymer (hydroxypropylmethylcellulose). Both were injected into osseous defects at the distal end of rabbit femurs for 2- and 3-week periods. Quantitative results for tartrate-resistant acid phosphatase (TRAP) cellular activity, new bone formation, and ceramic resorption were studied for statistical purposes. Positive TRAP-stained degradation cells were significantly more numerous for IBS 40-80 than IBS 200-500, regardless of implantation time. BCP degradation was quite marked during the first 2 weeks for IBS 40-80, and bone colonization occurred more extensively for IBS 40-80 than for IBS 200-500. The resorption-bone substitution process occurred earlier and faster for IBS 40-80 than IBS 200-500. Both tested IBS displayed similar biological efficiency, with conserved in vivo bioactivity and bone-filling ability. Differences in calcium phosphate particle sizes influenced cellular degradation activity and ceramic resorption but were compatible with efficient bone substitution.

Fixed-energy biphasic waveform defibrillation in a pediatric model of cardiac arrest and resuscitation.

PubMed

Tang, Wanchun; Weil, Max Harry; Jorgenson, Dawn; Klouche, Kada; Morgan, Carl; Yu, Ting; Sun, Shijie; Snyder, David

2002-12-01

For adults, 150-J fixed-energy, impedance-compensating biphasic truncated exponential (ICBTE) shocks are now effectively used in automated defibrillators. However, the high energy levels delivered by adult automated defibrillators preclude their use for pediatric patients. Accordingly, we investigated a method by which adult automated defibrillators may be adapted to deliver a 50-J ICBTE shock for pediatric defibrillation. Prospective, randomized study. A university-affiliated research institution. Domestic piglets. We initially investigated four groups of anesthetized mechanically ventilated piglets weighing 3.8, 7.5, 15, and 25 kg. Ventricular fibrillation was induced with an AC current delivered to the right ventricular endocardium. After 7 mins of untreated ventricular fibrillation, a conventional manual defibrillator was used to deliver up to three 50-J ICBTE shocks. If ventricular fibrillation was not reversed, a 1-min interval of precordial compression preceded a second sequence of up to three shocks. The protocol was repeated until spontaneous circulation was restored, or for a total of 15 mins. In a second set of experiments, we evaluated a 150-J biphasic adult automated defibrillator that was operated in conjunction with energy-reducing electrodes such as to deliver 50-J shocks. The same resuscitation protocol was then exercised on piglets weighing 3.7, 13.5, and 24.2 kg. All animals were successfully resuscitated. Postresuscitation hemodynamic and myocardial function quickly returned to baseline values in both experimental groups, and all animals survived. An adaptation of a 150-J biphasic adult automated defibrillator in which energy-reducing electrodes delivered 50-J shocks successfully resuscitated animals ranging from 3.7 to 25 kg without compromise of postresuscitation myocardial function or survival.

Short-term implantation effects of a DCPD-based calcium phosphate cement.

PubMed

Frayssinet, P; Gineste, L; Conte, P; Fages, J; Rouquet, N

1998-06-01

Calcium phosphate cements can be handled in paste form and set in a wet medium after precipitation of calcium phosphate crystals in the implantation site. Depending on the products entering into the chemical reaction leading to the precipitation of calcium phosphates, different phases can be obtained with different mechanical properties, setting times and injectability. We tested a cement composed of a powder, containing beta-tricalcium phosphate (beta-TCP) and sodium pyrophosphate mixed with a solution of phosphoric and sulphuric acids. The cement set under a dicalcium phosphate dihydrate (DCPD)-based matrix containing beta-TCP particles. This was injected with a syringe into a defect drilled in rabbit condyles, the control being an identical defect left empty in the opposite condyle. The condyles were analysed histologically 2, 6 and 18 weeks after implantation. After injection into the bone defect the cement set and formed a porous calcium phosphate structure. Two different calcium phosphate phases with different solubility rates could be identified by scanning electron microscopy (SEM) observation. The less-soluble fragments could be degraded by cell phagocytosis in cell compartments of low pH or integrated in the newly formed bone matrix. The degradation rate of the material was relatively high but compatible with the ingrowth of bone trabeculae within the resorbing material. The ossification process was different from the creeping substitution occurring at the ceramic contact. Bone did not form directly at the cement surface following the differentiation of osteoblasts at the material surface. The trabeculae came to the material surface from the edges of the implantation site. Bone formation in the implantation site was significantly higher than in the control region during the first week of implantation. In conclusion, this material set in situ was well tolerated, inducing a mild foreign-body reaction, which did not impair its replacement by newly formed

Design and characterization of calcium alginate microparticles coated with polycations as protein delivery system.

PubMed

Zarate, J; Virdis, L; Orive, G; Igartua, M; Hernández, R M; Pedraz, J L

2011-01-01

Bovine serum albumin (BSA) loaded calcium alginate microparticles (MPs) produced in this study by a w/o emulsification and external gelation method exhibited spherical and fairly smooth and porous morphology with 1.052 ± 0.057 µm modal particle size. The high permeability of the calcium alginate hydrogel lead to a potent burst effect and too fast protein release. To overcome these problems, MPs were coated with polycations, such as chitosan, poly-L-lysine and DEAE-dextran. Our results demonstrated that coated MPs showed slower release and were able to significantly reduce the release of BSA in the first hour. Therefore, this method can be applied to prepare coated alginate MPs which could be an optimal system for the controlled release of biotherapeutic molecules. Nevertheless, further studies are needed to optimize delivery properties which could provide a sustained release of proteins.

Partitioning of mercury in aqueous biphasic systems and on ABEC resins.

PubMed

Rogers, R D; Griffin, S T

1998-06-26

Poly(ethylene glycol)-based aqueous biphasic systems (PEG-ABS) can be utilized to separate and recover metal ions in environmental and hydrometallurgical applications. A concurrent study was conducted comparing the partitioning of mercury between aqueous layers in an ABS [Me-PEG-5000/(NH4)2SO4] and partitioning of mercury from aqueous solutions to aqueous biphasic extraction chromatographic (ABEC-5000) resins. In ammonium sulfate solutions, mercury partitions to the salt-rich phase in ABS, but by using halide ion extractants, mercury will partition to the PEG-rich phase after formation of a chloro, bromo or iodo complex. The efficacy of the extractant increases in the order Cl-

Calcium-deficient apatite synthesized by ammonia hydrolysis of dicalcium phosphate dihydrate: influence of temperature, time, and pressure.

PubMed

Obadia, Laetitia; Rouillon, Thierry; Bujoli, Bruno; Daculsi, Guy; Bouler, Jean Michel

2007-01-01

In this work, calcium-deficient apatites (CDA) were synthesized by ammonia hydrolysis reaction of dicalcium phosphate dihydrate (DCPD; CaHPO4 x 2 H2O) to obtain biphasic calcium phosphates (BCP) without any extraionic substitution. The influence of three parameters was studied: temperature of the reaction (70 and 100 degrees C), time of the reaction (4 and 18 h), and the pressure (open and closed system). Experiments were made according to a factorial design method (FDM) allowing optimization of the number of samples as well as statistical analysis of results. Moreover, the influence of temperature (until 200 degrees C) was investigated. The crystal size of CDA was determined according to the Scherrer's formula and from Rietveld refinements taking the CDA anisotropy into account. The last method seems to be a reliable method to determine crystallite sizes of CDA, since crystallite sizes of CDA along <00l> and directions were accessible. The results describe the hydroxyapatite % (HA%) in BCP by a first-order polynomial equation in the experimental area studied and the HA content was found to increase by raising time and temperature of the reaction. Moreover, the type of reaction system (open/closed vessel) appeared to have little influence on HA%. 2006 Wiley Periodicals, Inc.

Strontium-doped calcium silicate bioceramic with enhanced in vitro osteogenic properties.

PubMed

No, Young Jung; Roohaniesfahani, Seyediman; Lu, Zufu; Shi, Jeffrey; Zreiqat, Hala

2017-06-05

Gehlenite (GLN, Ca 2 SiAl 2 O 7 ) is a bioceramic that has been recently shown to possess excellent mechanical strength and in vitro osteogenic properties for bone regeneration. Substitutional incorporation of strontium in place of calcium is an effective way to further enhance biological properties of calcium-based bioceramics and glasses. However, such strategy has the potential to affect other important physicochemical parameters such as strength and degradation due to differences in the ionic radius of strontium and calcium. This study is the first to investigate the effect of a range of concentrations of strontium substitution of calcium at 1, 2, 5, 10 mol% (S1-GLN, S2-GLN, S5-GLN and S10-GLN) on the physicochemical and biological properties of GLN. We showed that up to 2 mol% strontium ion substitution retains the monophasic GLN structure when sintered at 1450 °C, whereas higher concentrations resulted in presence of calcium silicate impurities. Increased strontium incorporation resulted in changes in grain morphology and reduced densification when the ceramics were sintered at 1450 °C. Porous GLN, S1-GLN and S2-GLN scaffolds (∼80% porosity) showed compressive strengths of 2.05 ± 0.46 MPa, 1.76 ± 0.79 MPa and 1.57 ± 0.52 MPa respectively. S1-GLN and S2-GLN immersed in simulated body fluid showed increased strontium ion release but reduced calcium and silicon ion release compared to GLN without affecting overall weight loss and pH over a 21 d period. The bioactivity of the S2-GLN ceramics was significantly improved as reflected in the significant upregulation of HOB proliferation and differentiation compared to GLN. Overall, these results suggest that increased incorporation of strontium presents a trade-off between bioactivity and mechanical strength for GLN bioceramics. This is an important consideration in the development of strontium-doped bioceramics.

A randomized controlled trial of efficacy and ST change following use of the Welch-Allyn MRL PIC biphasic waveform versus damped sine monophasic waveform for external DC cardioversion.

PubMed

Ambler, Jonathan J S; Deakin, Charles D

2006-11-01

Biphasic waveforms have similar or greater efficacy at cardioverting atrial and ventricular arrhythmias at lower energy levels than monophasic waveforms, and cause less ST depression following defibrillation of ventricular fibrillation. No studies have investigated this effect on ST change with atrial arrhythmias. We studied the efficacy of the Welch Allyn-MRL PIC biphasic defibrillator. One hundred and thirty-nine patients undergoing elective DC cardioversion for atrial arrhythmias were randomised to cardioversion by monophasic (Hewlett Packard Codemaster XL; 100, 200, 300, 360 and 360J) or biphasic (Welch Allyn-MRL PIC; 70, 100, 150, 200 and 300J) defibrillator. We analysed success of cardioversion after 0 and 30min, cumulative energy, number of shocks and energy at successful cardioversion. The ST change in the recorded electrocardiogram was measured at 15s after all shocks using electronic callipers. Immediately after cardioversion 59/68 (86.8%) of the monophasic group versus 56/60 (93.3%) of the biphasic group were in sinus rhythm. Of the monophasic group, 55/67 (82.1%) remained in sinus rhythm at 30min versus 53/58 (91.4%) of the biphasic group. These differences were not significant at 0min (P=0.35) or 30min (P=0.21). The biphasic group required significantly fewer shocks (P=0.006), less cumulative energy (P<0.0001) and required lower total energy for successful cardioversion (P<0.0001). Of the 102 patients with electrocardiogram recordings suitable for analysis, ST segment change was greater in the monophasic group (P=0.037). The Welch Allyn-MRL biphasic waveform for DC cardioversion results in fewer shocks, with less cumulative energy delivered and less post shock ST change than with a Hewlett Packard Codemaster XL damped sine wave monophasic waveform.

Biomimetic porous high-density polyethylene/polyethylene- grafted-maleic anhydride scaffold with improved in vitro cytocompatibility.

PubMed

Sharma, Swati; Bhaskar, Nitu; Bose, Surjasarathi; Basu, Bikaramjit

2018-05-01

A major challenge for tissue engineering is to design and to develop a porous biocompatible scaffold, which can mimic the properties of natural tissue. As a first step towards this endeavour, we here demonstrate a distinct methodology in biomimetically synthesized porous high-density polyethylene scaffolds. Co-extrusion approach was adopted, whereby high-density polyethylene was melt mixed with polyethylene oxide to form an immiscible binary blend. Selective dissolution of polyethylene oxide from the biphasic system revealed droplet-matrix-type morphology. An attempt to stabilize such morphology against thermal and shear effects was made by the addition of polyethylene- grafted-maleic anhydride as a compatibilizer. A maximum ultimate tensile strength of 7 MPa and elastic modulus of 370 MPa were displayed by the high-density polyethylene/polyethylene oxide binary blend with 5% maleated polyethylene during uniaxial tensile loading. The cell culture experiments with murine myoblast C2C12 cell line indicated that compared to neat high-density polyethylene and high-density polyethylene/polyethylene oxide, the high-density polyethylene/polyethylene oxide with 5% polyethylene- grafted-maleic anhydride scaffold significantly increased muscle cell attachment and proliferation with distinct elongated threadlike appearance and highly stained nuclei, in vitro. This has been partly attributed to the change in surface wettability property with a reduced contact angle (∼72°) for 5% PE- g-MA blends. These findings suggest that the high-density polyethylene/polyethylene oxide with 5% polyethylene- grafted-maleic anhydride can be treated as a cell growth substrate in bioengineering applications.

Characteristics of hydroxyapatite coated titanium porous coatings on Ti-6Al-4V substrates by plasma sprayed method.

PubMed

Yang, C Y; Chen, C R; Chang, E; Lee, T M

2007-08-01

A porous metal coating applied to solid substrate implants has been shown, in vivo, to anchor implants by bone ingrowth. Calcium phosphate ceramics, in particular hydroxyapatite [Ca(10)(PO(4))(6)(OH)(2), HA], are bioactive ceramics, which are known to be biocompatible and osteoconductive, and these ceramics deposited on to porous-coated devices may enhance bone ingrowth and implant fixation. In this study, bi-feedstock of the titanium powder and composite (Na(2)CO(3)/HA) powder were simultaneously deposited on a Ti-6Al-4V substrate by a plasma sprayed method. At high temperature of plasma torch, the solid state of Na(2)CO(3) would decompose to release CO(2) gas and then eject the molten Ti powder to induce the interconnected pores in the coatings. After cleaning and soaking in deionized water, the residual Na(2)CO(3) in the coating would dissolve to form the open pores, and the HA would exist at the surface of pores in the inner coatings. By varying the particle size of the composite powder, the porosity of porous coating could be varied from 25.0 to 34.0%, and the average pore size of the porous coating could be varied to range between 158.5 and 202.0 microm. Using a standard adhesive test (ASTM C-633), the bonding strength of the coating is between 27.3 and 38.2 MPa. By SEM, the HA was observed at the surface of inner pore in the porous coating. These results suggest that the method exhibits the potential to manufacture the bioactive ceramics on to porous-coated specimen to achieve bone ingrowth fixation for biomedical applications.

Average current is better than peak current as therapeutic dosage for biphasic waveforms in a ventricular fibrillation pig model of cardiac arrest.

PubMed

Chen, Bihua; Yu, Tao; Ristagno, Giuseppe; Quan, Weilun; Li, Yongqin

2014-10-01

Defibrillation current has been shown to be a clinically more relevant dosing unit than energy. However, the effects of average and peak current in determining shock outcome are still undetermined. The aim of this study was to investigate the relationship between average current, peak current and defibrillation success when different biphasic waveforms were employed. Ventricular fibrillation (VF) was electrically induced in 22 domestic male pigs. Animals were then randomized to receive defibrillation using one of two different biphasic waveforms. A grouped up-and-down defibrillation threshold-testing protocol was used to maintain the average success rate of 50% in the neighborhood. In 14 animals (Study A), defibrillations were accomplished with either biphasic truncated exponential (BTE) or rectilinear biphasic waveforms. In eight animals (Study B), shocks were delivered using two BTE waveforms that had identical peak current but different waveform durations. Both average and peak currents were associated with defibrillation success when BTE and rectilinear waveforms were investigated. However, when pathway impedance was less than 90Ω for the BTE waveform, bivariate correlation coefficient was 0.36 (p=0.001) for the average current, but only 0.21 (p=0.06) for the peak current in Study A. In Study B, a high defibrillation success (67.9% vs. 38.8%, p<0.001) was observed when the waveform delivered more average current (14.9±2.1A vs. 13.5±1.7A, p<0.001) while keeping the peak current unchanged. In this porcine model of VF, average current was better than peak current to be an adequate parameter to describe the therapeutic dosage when biphasic defibrillation waveforms were used. The institutional protocol number: P0805. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Superabsorbent biphasic system based on poly(lactic acid) and poly(acrylic acid)

NASA Astrophysics Data System (ADS)

Sartore, Luciana; Pandini, Stefano; Baldi, Francesco; Bignotti, Fabio

2016-05-01

In this research work, biocomposites based on crosslinked particles of poly(acrylic acid), commonly used as superabsorbent polymer (SAP), and poly-L-lactic acid (PLLA) were developed to elucidate the role of the filler (i.e., polymeric crosslinked particles) on the overall physico-mechanical behavior and to obtain superabsorbent thermoplastic products. Samples prepared by melt-blending of components in different ratios showed a biphasic system with a regular distribution of particles, with diameter ranging from 5 to 10 μm, within the PLLA polymeric matrix. The polymeric biphasic system, coded PLASA i.e. superabsorbent poly(lactic acid), showed excellent swelling properties, demonstrating that cross-linked particles retain their superabsorbent ability, as in their free counterparts, even if distributed in a thermoplastic polymeric matrix. The thermal characteristics of the biocomposites evidence enhanced thermal stability in comparison with neat PLLA and also mechanical properties are markedly modified by addition of crosslinked particles which induce regular stiffening effect. Furthermore, in aqueous environments the particles swell and are leached from PLLA matrix generating very high porosity. These new open-pore PLLA foams, produced in absence of organic solvents and chemical foaming agents, with good physico-mechanical properties appear very promising for several applications, for instance in tissue engineering for scaffold production.

The Role of Carboxydothermus hydrogenoformans in the Conversion of Calcium Phosphate from Amorphous to Crystalline State

PubMed Central

Haddad, Mathieu; Vali, Hojatollah; Paquette, Jeanne; Guiot, Serge R.

2014-01-01

Two previously unknown modes of biomineralization observed in the presence of Carboxydothermus hydrogenoformans are presented. Following the addition of NaHCO3 and the formation of an amorphous calcium phosphate precipitate in a DSMZ medium inoculated with C. hydrogenoformans, two distinct crystalline solids were recovered after 15 and 30 days of incubation. The first of these solids occurred as micrometric clusters of blocky, angular crystals, which were associated with bacterial biofilm. The second solid occurred as 30–50 nm nanorods that were found scattered among the organic products of bacterial lysis. The biphasic mixture of solids was clearly dominated by the first phase. The X-ray diffractometry (XRD) peaks and Fourier transform infrared spectroscopy (FTIR) spectrum of this biphasic material consistently showed features characteristic of Mg-whitlockite. No organic content or protein could be identified by dissolving the solids. In both cases, the mode of biomineralization appears to be biologically induced rather than biologically controlled. Since Mg is known to be a strong inhibitor of the nucleation and growth of CaP, C. hydrogenoformans may act by providing sites that chelate Mg or form complexes with it, thus decreasing its activity as nucleation and crystal growth inhibitor. The synthesis of whitlockite and nano-HAP-like material by C. hydrogenoformans demonstrates the versatility of this organism also known for its ability to perform the water-gas shift reaction, and may have applications in bacterially mediated synthesis of CaP materials, as an environmentally friendly alternative process. PMID:24586811

Biphasic regulation of the transcription factor ABORTED MICROSPORES (AMS) is essential for tapetum and pollen development in Arabidopsis.

PubMed

Ferguson, Alison C; Pearce, Simon; Band, Leah R; Yang, Caiyun; Ferjentsikova, Ivana; King, John; Yuan, Zheng; Zhang, Dabing; Wilson, Zoe A

2017-01-01

Viable pollen is essential for plant reproduction and crop yield. Its production requires coordinated expression at specific stages during anther development, involving early meiosis-associated events and late pollen wall formation. The ABORTED MICROSPORES (AMS) transcription factor is a master regulator of sporopollenin biosynthesis, secretion and pollen wall formation in Arabidopsis. Here we show that it has complex regulation and additional essential roles earlier in pollen formation. An inducible-AMS reporter was created for functional rescue, protein expression pattern analysis, and to distinguish between direct and indirect targets. Mathematical modelling was used to create regulatory networks based on wild-type RNA and protein expression. Dual activity of AMS was defined by biphasic protein expression in anther tapetal cells, with an initial peak around pollen meiosis and then later during pollen wall development. Direct AMS-regulated targets exhibit temporal regulation, indicating that additional factors are associated with their regulation. We demonstrate that AMS biphasic expression is essential for pollen development, and defines distinct functional activities during early and late pollen development. Mathematical modelling suggests that AMS may competitively form a protein complex with other tapetum-expressed transcription factors, and that biphasic regulation is due to repression of upstream regulators and promotion of AMS protein degradation. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

Calcium deprivation increases the palatability of calcium solutions in rats.

PubMed

McCaughey, Stuart A; Forestell, Catherine A; Tordoff, Michael G

2005-02-15

Calcium-deprived rats have elevated intakes of CaCl2, other calcium salts, and some non-calcium compounds. We used taste reactivity to examine the effects of calcium deprivation on the palatability of CaCl2 and other solutions. Nine male Sprague-Dawley rats were calcium-deprived by maintenance on a low-calcium diet, and eight replete rats were used as controls. All rats were videotaped during intraoral infusion of the following solutions: 30 and 300 mM CaCl2, 30 mM calcium lactate, 100 and 600 mM NaCl, 30 mM MgCl2, 1 mM quinine.HCl, 2.5 mM sodium saccharin, and deionized water. We counted individual orofacial and somatic movements elicited by the infusions and used them to calculate total ingestive and aversive scores. Relative to controls, calcium-deprived rats gave a significantly larger number of tongue protrusions and had higher total ingestive scores for CaCl2, calcium lactate, NaCl, and MgCl2. Our results suggest that CaCl2, calcium lactate, NaCl, and MgCl2 taste more palatable to rats when they are calcium-deprived than replete, and this may be responsible for the increased intake of these solutions following calcium deprivation.

Development of a discriminative biphasic in vitro dissolution test and correlation with in vivo pharmacokinetic studies for differently formulated racecadotril granules.

PubMed

Deng, Jia; Staufenbiel, Sven; Hao, Shilei; Wang, Bochu; Dashevskiy, Andriy; Bodmeier, Roland

2017-06-10

The purpose of this study was to discriminate the release behavior from three differently formulated racecadotril (BCS II) granules and to establish an in vitro-in vivo correlation. Three granule formulations of the lipophilic drug were prepared with equivalent composition but prepared with different manufacturing processes (dry granulation, wet granulation with or without binder). In vitro release of the three granules was investigated using a biphasic dissolution system (phosphate buffer pH6.8 and octanol) and compared to the conventional single phase USP II dissolution test performed under sink and non-sink conditions. In vivo studies with each granule formulation were performed in rats. Interestingly, the granule formulations exhibited pronouncedly different behavior in the different dissolution systems depending on different wetting and dissolution conditions. Single phase USP II dissolution tests lacked discrimination. In contrast, remarkable discrimination between the granule formulations was observed in the octanol phase of biphasic dissolution system with a rank order of release from granules prepared by wet granulation with binder>wet granulation without binder>dry granulation. This release order correlated well with the wettability of these granules. An excellent correlation was also established between in vitro release in the octanol phase of the biphasic test and in vivo data (R 2 =0.999). Compared to conventional dissolution methods, the biphasic method provides great potential to discriminate between only minor formulation and process changes within the same dosage form for poorly soluble drugs. Copyright © 2017 Elsevier B.V. All rights reserved.

Biphasic effects of alcohol as a function of circadian phase.

PubMed

Van Reen, Eliza; Rupp, Tracy L; Acebo, Christine; Seifer, Ronald; Carskadon, Mary A

2013-01-01

To assess how alcohol affects multiple sleep latency tests (MSLT) and subjective measures of stimulation/sedation when alcohol is given at different circadian phases. Twenty-seven healthy young adults (age 21-26 yr) were studied. Double-blind placebo and alcohol (vodka tonic targeting 0.05 g% concentration) beverages were each administered three times during the 20-h forced desynchrony protocol. Sleep latency tests and Biphasic Effects of Alcohol Scale (BAES) were administered on each forced desynchrony day. The outcome variables for this study include sleep onset latency (SOL) and stimulation and sedation value (from the BAES). Each outcome variable was associated with the ascending or descending limb of the breath alcohol concentration (BrAC) curve and assigned a circadian phase within a 90° bin. BrAC confirmed targeted maximal levels. Only outcome variables associated with the ascending and descending limb of the alcohol curve were analyzed for this article. Alcohol administered at a circadian time associated with greatest sleepiness showed longer SOL compared with placebo when measured on the ascending limb of the BrAC curve. We also found longer SOL with alcohol on the ascending limb of the BrAC curve in a circadian bin that favors greatest alertness. We observed shorter SOLs on the descending limb of the BrAC curve, but with no circadian phase interaction. The subjective data were partially consistent with the objective data. The physiologic findings in this study support the biphasic stimulating and sedating properties of alcohol, but limit the effect to specific circadian times.

Accounting for phase drifts in SSVEP-based BCIs by means of biphasic stimulation.

PubMed

Wu, Hung-Yi; Lee, Po-Lei; Chang, Hsiang-Chih; Hsieh, Jen-Chuen

2011-05-01

This study proposes a novel biphasic stimulation technique to solve the issue of phase drifts in steady-state visual evoked potential (SSVEPs) in phase-tagged systems. Phase calibration was embedded in stimulus sequences using a biphasic flicker, which is driven by a sequence with alternating reference and phase-shift states. Nine subjects were recruited to participate in off-line and online tests. Signals were bandpass filtered and segmented by trigger signals into reference and phase-shift epochs. Frequency components of SSVEP in the reference and phase-shift epochs were extracted using the Fourier method with a 50% overlapped sliding window. The real and imaginary parts of the SSVEP frequency components were organized into complex vectors in each epoch. Hotelling's t-square test was used to determine the significances of nonzero mean vectors. The rejection of noisy data segments and the validation of gaze detections were made based on p values. The phase difference between the valid mean vectors of reference and phase-shift epochs was used to identify user's gazed targets in this system. Data showed an average information transfer rate of 44.55 and 38.21 bits/min in off-line and online tests, respectively. © 2011 IEEE

Application of a Three-Dimensional Poroelastic BEM to Modeling the Biphasic Mechanics of Cell-Matrix Interactions in Articular Cartilage (REVISION)

PubMed Central

Haider, Mansoor A.; Guilak, Farshid

2009-01-01

Articular cartilage exhibits viscoelasticity in response to mechanical loading that is well described using biphasic or poroelastic continuum models. To date, boundary element methods (BEMs) have not been employed in modeling biphasic tissue mechanics. A three dimensional direct poroelastic BEM, formulated in the Laplace transform domain, is applied to modeling stress relaxation in cartilage. Macroscopic stress relaxation of a poroelastic cylinder in uni-axial confined compression is simulated and validated against a theoretical solution. Microscopic cell deformation due to poroelastic stress relaxation is also modeled. An extended Laplace inversion method is employed to accurately represent mechanical responses in the time domain. PMID:19851478

Application of a Three-Dimensional Poroelastic BEM to Modeling the Biphasic Mechanics of Cell-Matrix Interactions in Articular Cartilage (REVISION).

PubMed

Haider, Mansoor A; Guilak, Farshid

2007-06-15

Articular cartilage exhibits viscoelasticity in response to mechanical loading that is well described using biphasic or poroelastic continuum models. To date, boundary element methods (BEMs) have not been employed in modeling biphasic tissue mechanics. A three dimensional direct poroelastic BEM, formulated in the Laplace transform domain, is applied to modeling stress relaxation in cartilage. Macroscopic stress relaxation of a poroelastic cylinder in uni-axial confined compression is simulated and validated against a theoretical solution. Microscopic cell deformation due to poroelastic stress relaxation is also modeled. An extended Laplace inversion method is employed to accurately represent mechanical responses in the time domain.

Calcium ionization balance and argon/calcium abundance in solar flares

NASA Astrophysics Data System (ADS)

Antonucci, E.; Marocchi, D.; Gabriel, A. H.; Doschek, G. A.

1987-12-01

An earlier analysis of solar flare calcium spectra from XRP and P78-1 aimed at measuring the calcium ionization balance resulted in an ambiguity due to a line blend between the calcium q line and an Ar XVII line. In the present work the calcium line 'r' is included in the analysis in order to resolve this problem. It is shown that the correct calcium ionization balance is that indicated in the earlier paper as corresponding to an argon/calcium abundance ratio of 0.2. The argon/calcium abundance ratio in the group of solar flares studied is shown to be 0.2 + or - 0.2. It is further argued that while the abundance of heavy elements may be enhanced in energetic flare events, this enhancement is less for argon than for calcium, leading to an argon/calcium ratio smaller than that present in the quiet sun.

Clogging and Cementation Caused by Calcium or Iron Biogrouts

NASA Astrophysics Data System (ADS)

Ivanov, V.; Chu, J.; Naeimi, M.

2012-12-01

function of the precipitated metal content (X, % ww-1) according to the following equations: Y = 14.7X^2 -0.72 X for calcium-based biogrout, and Y = 13.6X^2 + 37.0 X for iron-based biogrout. The strength of wet biocemented sand at the content of precipitated metals below 1.5 % w/w was very low and only at the content of precipitated metal above 3% w/w it was increased to 230 - 240 kPa. Therefore, major geotechnical applications of calcium-based and iron-based biogrouts at the contents of the precipitated metal below 1.5% could be bioclogging of the porous soil rather than its strengthening. This bioclogging could be applicable to the sealing the aquaculture or wastewater treatment ponds, construction of the algal biofuel production ponds, landfill sites, as well as for the plugging of the piping in dams, retaining walls, channels or reservoirs in sandy soil.

Calcium Carbonate

MedlinePlus

... Maalox® (as a combination product containing Calcium Carbonate, Simethicone) ... Relief (as a combination product containing Calcium Carbonate, Simethicone) ... Plus (as a combination product containing Calcium Carbonate, Simethicone)

Preparation of asymmetric porous materials

DOEpatents

Coker, Eric N [Albuquerque, NM

2012-08-07

A method for preparing an asymmetric porous material by depositing a porous material film on a flexible substrate, and applying an anisotropic stress to the porous media on the flexible substrate, where the anisotropic stress results from a stress such as an applied mechanical force, a thermal gradient, and an applied voltage, to form an asymmetric porous material.

Characterizing liquid redistribution in a biphasic vibrating vocal fold using finite element analysis.

PubMed

Kvit, Anton A; Devine, Erin E; Jiang, Jack J; Vamos, Andrew C; Tao, Chao

2015-05-01

Vocal fold tissue is biphasic and consists of a solid extracellular matrix skeleton swelled with interstitial fluid. Interactions between the liquid and solid impact the material properties and stress response of the tissue. The objective of this study was to model the movement of liquid during vocal fold vibration and to estimate the volume of liquid accumulation and stress experienced by the tissue near the anterior-posterior midline, where benign lesions are observed to form. A three-dimensional biphasic finite element model of a single vocal fold was built to solve for the liquid velocity, pore pressure, and von Mises stress during and just after vibration using the commercial finite element software COMSOL Multiphysics (Version 4.3a, 2013, Structural Mechanics and Subsurface Flow Modules). Vibration was induced by applying direct load pressures to the subglottal and intraglottal surfaces. Pressure ranges, frequency, and material parameters were chosen based on those reported in the literature. Postprocessing included liquid velocity, pore pressure, and von Mises stress calculations as well as the frequency-stress and amplitude-stress relationships. Resulting time-averaged velocity vectors during vibration indicated liquid movement toward the midline of the fold, as well as upward movement in the inferior-superior direction. Pore pressure and von Misses stresses were higher in this region just after vibration. A linear relationship was found between the amplitude and pore pressure, whereas a nonlinear relationship was found between the frequency and pore pressure. Although this study had certain computational simplifications, it is the first biphasic finite element model to use a realistic geometry and demonstrate the ability to characterize liquid movement due to vibration. Results indicate that there is a significant amount of liquid that accumulates at the midline; however, the role of this accumulation still requires investigation. Further investigation of

Characterizing liquid redistribution in a biphasic vibrating vocal fold using finite element analysis

PubMed Central

Kvit, Anton A.; Devine, Erin E.; Vamos, Andrew C.; Tao, Chao; Jiang, Jack J.

2015-01-01

OBJECTIVE Vocal fold tissue is biphasic and consists of a solid extracellular matric skeleton swelled with interstitial fluid. Interactions between the liquid and solid impact the material properties and stress response of the tissue. The objective of this study was to model the movement of liquid during vocal fold vibration and estimate the volume of liquid accumulation and stress experienced by the tissue near the anterior-posterior midline, where benign lesions are observed to form. METHODS A three-dimensional biphasic finite element model of a single vocal fold was built to solve for the liquid velocity, pore pressure, and von Mises stress during and just after vibration using the commercial finite element software COMSOL Multiphysics (Version 4.3a, 2013, Structural Mechanics and Subsurface Flow Modules). Vibration was induced by applying direct-load pressures to the subglottal and intraglottal surfaces. Pressure ranges, frequency and material parameters were chosen based on those reported in the literature. Post-processing included liquid velocity, pore pressure and von Mises stress calculations, as well as the frequency-stress and amplitude-stress relationships. RESULTS Resulting time-averaged velocity vectors during vibration indicated liquid movement towards the midline of the fold, as upwards movement in the inferior-superior direction. Pore pressure and von Misses stresses were higher in this region just following vibration. A linear relationship was found between the amplitude and pore pressure, while a nonlinear relationship was found between the frequency and pore pressure. CONCLUSIONS While this study had certain computational simplifications, it is the first biphasic finite element model to employ a realistic geometry and demonstrated the ability to characterize liquid movement due to vibration. Results indicate that there is a significant amount of liquid that accumulates at the midline, however the role of this accumulation still requires

Risk of calcium oxalate nephrolithiasis in postmenopausal women supplemented with calcium or combined calcium and estrogen.

PubMed

Domrongkitchaiporn, Somnuek; Ongphiphadhanakul, Boonsong; Stitchantrakul, Wasana; Chansirikarn, Sirinthorn; Puavilai, Gobchai; Rajatanavin, Rajata

2002-02-26

Recent studies showed that postmenopausal women lost less bone mass when supplemented with calcium or estrogen therapy. However, the safety of the treatments in terms of the risk of calcium oxalate stone formation is unknown. We therefore conducted this study to determine the alteration in calcium oxalate supersaturation after calcium supplement or after combined calcium and estrogen therapy in postmenopausal osteoporotic women. Fifty-six postmenopausal women were enrolled in this study. All subjects were more than 10 years postmenopausal with vertebral or femoral osteoporosis by bone mineral density criteria. They were randomly allocated to receive either 625 mg of calcium carbonate (250 mg of elemental calcium) at the end of a meal three times a day (group A, n=26) or calcium carbonate in the same manner plus 0.625 mg/day of conjugated equine estrogen and 5 mg medrogestone acetate from day 1-12 each month (group B, n=30). The age (mean +/- S.E.M.) was 66.3 +/- 1.2 and 65.1 +/- 1.1 years, weight 54.1 +/- 1.2 and 55.3 +/- 2.1 kg, in group A and group B, respectively. Urine specimens (24-h) were collected at baseline and 3 months after treatment for the determination of calcium oxalate saturation by using Tiselius's index (AP(CaOx)) and calcium/citrate ratio. After 3 months of treatment, there was no significant alteration from baseline for urinary excretion of calcium, citrate and oxalate. Urinary phosphate excretion was significantly reduced (6.3 +/- 0.7 vs. 5.1 +/- 0.7 mmol/day for group A and 8.2 +/- 0.9 vs. 5.8 +/- 0.7 mmol/day for group B, P<0.05), whereas net alkaline absorption was significantly elevated (10.1 +/- 3.6 vs. 20.1 +/- 4.4 meq/day for group A and 4.8 +/- 3.2 vs. 19.9 +/- 3.6 meq/day for group B, P<0.05). Calcium/citrate ratio and AP(CaOx) determined at baseline were not different from the corresponding values after treatment in both groups; calcium/citrate: 10.1 +/- 3.1 vs. 10.1 +/- 2.5 for group A and 9.3 +/- 1.8 vs. 11.9 +/- 2.5 for group B and

Porous block nanofiber composite filters

DOEpatents

Ginley, David S.; Curtis, Calvin J.; Miedaner, Alexander; Weiss, Alan J.; Paddock, Arnold

2016-08-09

Porous block nano-fiber composite (110), a filtration system (10) and methods of using the same are disclosed. An exemplary porous block nano-fiber composite (110) includes a porous block (100) having one or more pores (200). The porous block nano-fiber composite (110) also includes a plurality of inorganic nano-fibers (211) formed within at least one of the pores (200).

Biphasic investigation of contact mechanics in natural human hips during activities.

PubMed

Li, Junyan; Hua, Xijin; Jin, Zhongmin; Fisher, John; Wilcox, Ruth K

2014-06-01

The aim of this study was to determine the cartilage contact mechanics and the associated fluid pressurisation of the hip joint under eight daily activities, using a three-dimensional finite element hip model with biphasic cartilage layers and generic geometries. Loads with spatial and temporal variations were applied over time and the time-dependent performance of the hip cartilage during walking was also evaluated. It was found that the fluid support ratio was over 90% during the majority of the cycles for all the eight activities. A reduced fluid support ratio was observed for the time at which the contact region slid towards the interior edge of the acetabular cartilage, but these occurred when the absolute level of the peak contact stress was minimal. Over 10 cycles of gait, the peak contact stress and peak fluid pressure remained constant, but a faster process of fluid exudation was observed for the interior edge region of the acetabular cartilage. The results demonstrate the excellent function of the hip cartilage within which the solid matrix is prevented from high levels of stress during activities owing to the load shared by fluid pressurisation. The findings are important in gaining a better understanding of the hip function during daily activities, as well as the pathology of hip degeneration and potential for future interventions. They provide a basis for future subject-specific biphasic investigations of hip performance during activities. © IMechE 2014.

Biphasic investigation of contact mechanics in natural human hips during activities

PubMed Central

Hua, Xijin; Jin, Zhongmin; Fisher, John; Wilcox, Ruth K

2014-01-01

The aim of this study was to determine the cartilage contact mechanics and the associated fluid pressurisation of the hip joint under eight daily activities, using a three-dimensional finite element hip model with biphasic cartilage layers and generic geometries. Loads with spatial and temporal variations were applied over time and the time-dependent performance of the hip cartilage during walking was also evaluated. It was found that the fluid support ratio was over 90% during the majority of the cycles for all the eight activities. A reduced fluid support ratio was observed for the time at which the contact region slid towards the interior edge of the acetabular cartilage, but these occurred when the absolute level of the peak contact stress was minimal. Over 10 cycles of gait, the peak contact stress and peak fluid pressure remained constant, but a faster process of fluid exudation was observed for the interior edge region of the acetabular cartilage. The results demonstrate the excellent function of the hip cartilage within which the solid matrix is prevented from high levels of stress during activities owing to the load shared by fluid pressurisation. The findings are important in gaining a better understanding of the hip function during daily activities, as well as the pathology of hip degeneration and potential for future interventions. They provide a basis for future subject-specific biphasic investigations of hip performance during activities. PMID:24898443

CALCIUM CHLORIDE PLANT LOOKING EAST. CALCIUM CHLORIDE BUILDING IN CENTER, ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

CALCIUM CHLORIDE PLANT LOOKING EAST. CALCIUM CHLORIDE BUILDING IN CENTER, CALCIUM CHLORIDE STORAGE BUILDING ON RIGHT WITH SA (SODA ASH) BUILDING IN RIGHT BACKGROUND. - Solvay Process Company, Calcium Chloride Plant, Between Willis & Milton Avenues, Solvay, Onondaga County, NY

Selective laser sintering of calcium phosphate materials for orthopedic implants

NASA Astrophysics Data System (ADS)

Lee, Goonhee

Two technologies, Solid Freeform Fabrication (SFF) and bioceramics are combined in this work to prepare bone replacement implants with complex geometry. SFF has emerged as a crucial technique for rapid prototyping in the last decade. Selective Laser Sintering (SLS) is one of the established SFF manufacturing processes that can build three-dimensional objects directly from computer models without part-specific tooling or human intervention. Meanwhile, there have been great efforts to develop implantable materials that can assist in regeneration of bone defects and injuries. However, little attention has been focused in shaping bones from these materials. The main thrust of this research was to develop a process that can combine those two separate efforts. The specific objective of this research is to develop a process that can construct bone replacement material of complex geometry from synthetic calcium phosphate materials by using the SLS process. The achievement of this goal can have a significant impact on the quality of health care in the sense that complete custom-fit bone and tooth structures suitable for implantation can be prepared within 24--48 hours of receipt of geometric information obtained either from patient Computed Tomographic (CT) data, from Computer Aided Design (CAD) software or from other imaging systems such as Magnetic Resonance Imaging (MRI) and Holographic Laser Range Imaging (HLRI). In this research, two different processes have been developed. First is the SLS fabrication of porous bone implants. In this effort, systematic procedures have been established and calcium phosphate implants were successfully fabricated from various sources of geometric information. These efforts include material selection and preparation, SLS process parameter optimization, and development of post-processing techniques within the 48-hour time frame. Post-processing allows accurate control of geometry and of the chemistry of calcium phosphate, as well as

Elution of Clindamycin and Enrofloxacin From Calcium Sulfate Hemihydrate Beads In Vitro.

PubMed

Phillips, Heidi; Boothe, Dawn M; Bennett, R Avery

2015-11-01

To compare the in vitro elution characteristics of clindamycin and enrofloxacin from calcium sulfate hemihydrate beads containing a single antibiotic, both antibiotics, and each antibiotic incubated in the same eluent well. Experimental in vitro study. Calcium sulfate hemihydrate beads were formed by mixing with clindamycin and/or enrofloxacin to create 4 study groups: (1) 160 mg clindamycin/10 beads; (2) 160 mg enrofloxacin/10 beads; (3) 160 mg clindamycin + 160 mg enrofloxacin/10 beads; and (4) 160 mg clindamycin/5 beads and 160 mg enrofloxacin/5 beads. Chains of beads were formed in triplicate and placed in 5 mL phosphate buffered saline (PBS; pH 7.4 and room temperature) with constant agitation. Antibiotic-conditioned PBS was sampled at 14 time points from 1 hour to 30 days. Clindamycin and enrofloxacin concentrations in PBS were determined using high-performance liquid chromatography. Eluent concentrations from clindamycin-impregnated beads failed to remain sufficiently above minimum inhibitory concentration (MIC) for common infecting bacteria over the study period. Enrofloxacin eluent concentrations remained sufficiently above MIC for common wound pathogens of dogs and cats and demonstrated an atypical biphasic release pattern. No significant differences in elution occurred as a result of copolymerization of the antibiotics into a single bead or from individual beads co-eluting in the same eluent well. Clindamycin-impregnated beads cannot be recommended for treatment of infection at the studied doses; however, use of enrofloxacin-impregnated beads may be justified when susceptible bacteria are cultured. © Copyright 2015 by The American College of Veterinary Surgeons.

21 CFR 172.330 - Calcium pantothenate, calcium chloride double salt.

Code of Federal Regulations, 2010 CFR

2010-04-01

... SERVICES (CONTINUED) FOOD FOR HUMAN CONSUMPTION (CONTINUED) FOOD ADDITIVES PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN CONSUMPTION Special Dietary and Nutritional Additives § 172.330 Calcium pantothenate, calcium chloride double salt. The food additive calcium chloride double salt of calcium pantothenate may...

21 CFR 172.330 - Calcium pantothenate, calcium chloride double salt.

Code of Federal Regulations, 2012 CFR

2012-04-01

... SERVICES (CONTINUED) FOOD FOR HUMAN CONSUMPTION (CONTINUED) FOOD ADDITIVES PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN CONSUMPTION Special Dietary and Nutritional Additives § 172.330 Calcium pantothenate, calcium chloride double salt. The food additive calcium chloride double salt of calcium pantothenate may...

21 CFR 172.330 - Calcium pantothenate, calcium chloride double salt.

Code of Federal Regulations, 2013 CFR

2013-04-01

... SERVICES (CONTINUED) FOOD FOR HUMAN CONSUMPTION (CONTINUED) FOOD ADDITIVES PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN CONSUMPTION Special Dietary and Nutritional Additives § 172.330 Calcium pantothenate, calcium chloride double salt. The food additive calcium chloride double salt of calcium pantothenate may...

CALCIUM CHLORIDE PLANT LOOKING EAST. CALCIUM CHLORIDE BUILDING ON LEFT, ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

CALCIUM CHLORIDE PLANT LOOKING EAST. CALCIUM CHLORIDE BUILDING ON LEFT, CALCIUM CHLORIDE STORAGE BUILDING ON RIGHT OF CENTER WITH TOP OF SA (SODA ASH) BUILDING IN RIGHT BACKGROUND. - Solvay Process Company, Calcium Chloride Plant, Between Willis & Milton Avenues, Solvay, Onondaga County, NY

Application of a biphasic test for characterization of in vitro drug release of immediate release formulations of celecoxib and its relevance to in vivo absorption.

PubMed

Shi, Yi; Gao, Ping; Gong, Yuchuan; Ping, Haili

2010-10-04

A biphasic in vitro test method was used to examine release profiles of a poorly soluble model drug, celecoxib (CEB), from its immediate release formulations. Three formulations of CEB were investigated in this study, including a commercial Celebrex capsule, a solution formulation (containing cosolvent and surfactant) and a supersaturatable self-emulsifying drug delivery system (S-SEDDS). The biphasic test system consisted of an aqueous buffer and a water-immiscible organic solvent (e.g., octanol) with the use of both USP II and IV apparatuses. The aqueous phase provided a nonsink dissolution medium for CEB, while the octanol phase acted as a sink for CEB partitioning. For comparison, CEB concentration-time profiles of these formulations in the aqueous medium under either a sink condition or a nonsink condition were also explored. CEB release profiles of these formulations observed in the aqueous medium from either the sink condition test, the nonsink condition test, or the biphasic test have little relevance to the pharmacokinetic observations (e.g., AUC, C(max)) in human subjects. In contrast, a rank order correlation among the three CEB formulations is obtained between the in vitro AUC values of CEB from the octanol phase up to t = 2 h and the in vivo mean AUC (or C(max)) values. As the biphasic test permits a rapid removal of drug from the aqueous phase by partitioning into the organic phase, the amount of drug in the organic phase represents the amount of drug accumulated in systemic circulation in vivo. This hypothesis provides the scientific rationale for the rank order relationship among these CEB formulations between their CEB concentrations in the organic phase and the relative AUC or C(max). In addition, the biphasic test method permits differentiation and discrimination of key attributes among the three different CEB formulations. This work demonstrates that the biphasic in vitro test method appears to be useful as a tool in evaluating performance of

Nanostructures formed by displacement of porous silicon with copper: from nanoparticles to porous membranes

PubMed Central

2012-01-01

The application of porous silicon as a template for the fabrication of nanosized copper objects is reported. Three different types of nanostructures were formed by displacement deposition of copper on porous silicon from hydrofluoric acid-based solutions of copper sulphate: (1) copper nanoparticles, (2) quasi-continuous copper films, and (3) free porous copper membranes. Managing the parameters of porous silicon (pore sizes, porosity), deposition time, and wettability of the copper sulphate solution has allowed to achieve such variety of the copper structures. Elemental and structural analyses of the obtained structures are presented. Young modulus measurements of the porous copper membrane have been carried out and its modest activity in surface enhanced Raman spectroscopy is declared. PMID:22916840

21 CFR 172.330 - Calcium pantothenate, calcium chloride double salt.

Code of Federal Regulations, 2014 CFR

2014-04-01

... SERVICES (CONTINUED) FOOD ADDITIVES PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN CONSUMPTION Special Dietary and Nutritional Additives § 172.330 Calcium pantothenate, calcium chloride double salt. The food additive calcium chloride double salt of calcium pantothenate may be safely used in foods for special...

Complex three dimensional modelling of porous media using high performance computing and multi-scale incompressible approach

NASA Astrophysics Data System (ADS)

Martin, R.; Orgogozo, L.; Noiriel, C. N.; Guibert, R.; Golfier, F.; Debenest, G.; Quintard, M.

2013-05-01

computed by sending batteries of codes in a mass production procedure. Some constraints can now be provided for poro-elastic imaging at the scale of reservoirs, for CO2 storage monitoring or geophysical exploration. 1. Golfier F. et al., Biofilms in porous media: Development of macroscopic transport equations va volume averaging with closure for local mass equilibrium conditions, Advances in Water Resources, 32, 463-485 (2009). 2. Orgogozo L. et al., Upscaling of transport processes in porous media with biofilms in non-equilibrium conditions, Advances in Water Resources, 33(5), 585-600 (2010). 3. Davit Y. et al., Modeling non-equilibrium mass transport in biologically reactive porous media, Advances in Water Resources, 33, 1075-1093, (2010). 4. Davit Y. et al., Imaging biofilm in porous media using X-ray computed micro-tomography, Journal of Microscopy, 242(1), 15-25 (2010). 5. Noiriel C. et al., Upscaling calcium carbonate precipitation rates from pore to continuum scale, Chemical Geology, 318-319, 60-74 (2012).

Porous ionic liquids: synthesis and application.

PubMed

Zhang, Shiguo; Dokko, Kaoru; Watanabe, Masayoshi

2015-07-15

Solidification of fluidic ionic liquids into porous materials yields porous ionic networks that combine the unique characteristics of ionic liquids with the common features of polymers and porous materials. This minireview reports the most recent advances in the design of porous ionic liquids. A summary of the synthesis of ordered and disordered porous ionic liquid-based nanoparticles or membranes with or without templates is provided, together with the new concept of room temperature porous ionic liquids. As a versatile platform for functional materials, porous ionic liquids have shown widespread applications in catalysis, adsorption, sensing, actuation, etc. This new research direction towards ionic liquids chemistry is still in its early stages but has great potential.

Role of cytosolic calcium diffusion in cardiac purkinje cells.

PubMed

Limbu, Bijay; Shah, Kushal; Deo, Makarand

2016-08-01

The Cardiac Purkinje cells (PCs) exhibit distinct calcium (Ca2+) homeostasis than that in ventricular myocytes (VMs). Due to lack of t-tubules in PCs, the Ca2+ ions entering the cell have to diffuse through the cytoplasm to reach the sarcoplasmic reticulum (SR) before triggering Ca2+-induced-Ca2+-release (CICR). In recent experimental studies PCs have been shown to be more susceptible to action potential (AP) abnormalities than the VMs, however the exact mechanisms are poorly understood. In this study, we utilize morphologically realistic detailed biophysical mathematical model of a murine PC to systematically examine the role intracellular Ca2+ diffusion in the APs of PCs. A biphasic spatiotemporal Ca2+ diffusion process, as observed experimentally, was implemented in the model which includes radial Ca2+ wavelets and cell wide longitudinal Ca2+ diffusion wave (CWW). The AP morphology, specifically plateau, is affected due to changes in intracellular Ca2+ dynamics. When Ca2+ concentration in sarcolemmal region is elevated, it activated inward sodium Ca2+ exchanger (NCX) current resulting into prolongation of the plateau at faster diffusion rates. Our results demonstrate that the cytosolic Ca2+ diffusion waves play a significant role in shaping APs of PCs and could provide mechanistic insights into the increased arrhythmogeneity of PCs.

Calcium waves.

PubMed

Jaffe, Lionel F

2008-04-12

Waves through living systems are best characterized by their speeds at 20 degrees C. These speeds vary from those of calcium action potentials to those of ultraslow ones which move at 1-10 and/or 10-20 nm s(-1). All such waves are known or inferred to be calcium waves. The two classes of calcium waves which include ones with important morphogenetic effects are slow waves that move at 0.2-2 microm s(-1) and ultraslow ones. Both may be propagated by cycles in which the entry of calcium through the plasma membrane induces subsurface contraction. This contraction opens nearby stretch-sensitive calcium channels. Calcium entry through these channels propagates the calcium wave. Many slow waves are seen as waves of indentation. Some are considered to act via cellular peristalsis; for example, those which seem to drive the germ plasm to the vegetal pole of the Xenopus egg. Other good examples of morphogenetic slow waves are ones through fertilizing maize eggs, through developing barnacle eggs and through axolotl embryos during neural induction. Good examples of ultraslow morphogenetic waves are ones during inversion in developing Volvox embryos and across developing Drosophila eye discs. Morphogenetic waves may be best pursued by imaging their calcium with aequorins.

Calcium mobilizations in response to changes in the gravity vector in Arabidopsis seedlings

PubMed Central

Tatsumi, Hitoshi; Toyota, Masatsugu; Furuichi, Takuya; Sokabe, Masahiro

2014-01-01

Gravity influences the growth direction of higher plants. Changes in the gravity vector (gravistimulation) immediately promote the increase in the cytoplasmic free calcium ion concentration ([Ca2+]c) in Arabidopsis (Arabidopsis thaliana) seedlings. When the seedlings are gravistimulated by reorientation at 180°, a transient two peaked (biphasic) [Ca2+]c-increase arises in their hypocotyl and petioles. Parabolic flights (PFs) can generate a variety of gravity-stimuli, and enables us to measure gravity-induced [Ca2+]c-increases without specimen rotation, which demonstrate that Arabidopsis seedlings possess a rapid gravity-sensing mechanism linearly transducing a wide range of gravitational changes into Ca2+ signals on a sub-second timescale. Hypergravity by centrifugation (20 g or 300 g) also induces similar transient [Ca2+]c-increases. In this review, we propose models for possible cellular processes of the garavi-stimulus-induced [Ca2+]c-increase, and evaluate those by examining whether the model fits well with the kinetic parameters derived from the [Ca2+]c-increases obtained by applying gravistimulus with different amplitudes and time sequences. PMID:25763612

Composition and structure of calcium aluminosilicate microspheres

NASA Astrophysics Data System (ADS)

Sharonova, O. M.; Oreshkina, N. A.; Zhizhaev, A. M.

2017-06-01

The composition was studied of calcium aluminosilicate microspheres of three morphological types in high-calcium fly ash from combustion of brown coal from the Kansk-Achinsk basin in slag-tap boilers at temperatures from 1400 to 1500°C and sampled in the first field of electrostatic precipitators at the Krasnoyarsk Cogeneration Power Station no. 2 (TETs-2). Gross compositions and the composition of local areas were determined using a scanning electron microscopy technique and an energy-dispersive analysis with full mapping of globules. With a high content of basic oxides O ox (68 to 79 wt %) and a low content of acid oxides K ox (21 to 31 wt %), type 1 microspheres are formed. They consist of heterogeneous areas having a porous structure and crystalline components in which the content of CaO, SiO2, or Al2O3 differs by two to three times and the content of MgO differs by seven times. With a lower content of O ox (55 to 63 wt %) and an elevated content of K ox (37 to 45 wt %), type 2 microspheres are formed. They are more homogeneous in the composition and structure and consist of similar crystalline components. Having a close content of O ox (46 to 53 wt %) and K ox (47 to 54 wt %), type 3 microspheres, which are a dense matter consisting of amorphous substance with submicron- and nanostructure of crystalline components, are formed. The basic precursor in formation of high-calcium aluminosilicate microspheres is calcium from the organomineral matter of coals with various contribution of Mg, Fe, S, or Na from the coal organic matter and Al, Fe, S, or Si in the form of single mineral inclusions in a coal particle. On the basis of the available data, the effect was analyzed of the composition of a CaO-MgO-Al2O3-SiO2-FeO system on the melting and viscous properties of the matter in microspheres and formation of globules of different morphology. The results of this analysis will help to find a correlation with properties of microspheres in their use as functional

Uniform Deposition of Protein Incorporated Mineral Layer on Three-Dimensional Porous Polymer Scaffolds

PubMed Central

Segvich, Sharon; Smith, Hayes C.; Luong, Linh N.; Kohn, David H.

2009-01-01

Inorganic–organic hybrid materials designed to facilitate bone tissue regeneration use a calcium phosphate mineral layer to encourage cell adhesion, proliferation, and osteogenic differentiation. Mineral formed on porous materials is often discontinuous through the thickness of the scaffold. This study aimed to uniformly coat the pores of three-dimensional (3D) porous, polymer scaffolds with a bone-like mineral layer in addition to uniformly incorporating a model protein within this mineral layer. A filtration system designed to induce simulated body fluid flow through the interstices of 3D polylactic-co-glycolic acid scaffolds (10-mm diameter × 2-mm thickness) illustrated that a uniform, continuous mineral layer can be precipitated on the pore surfaces of a 3D porous structure within 5 days. MicroCT analysis showed increased mineral volume percent (MV%) (7.86 ± 3.25 MV%, p = 0.029) and continuous mineralization of filtered scaffolds compared with two static control groups (floating, 0.16 ± 0.26 MV% and submerged, 0.20 ± 0.01 MV%). Furthermore, the system was effective in coprecipitating a model protein, bone sialoprotein (BSA), within the mineral layer. A 10-fold increase in BSA incorporation was seen when coprecipitated filtered scaffolds (1308 ± 464 μg) were compared to a submerged static control group (139 ± 45 μg), p < 0.001. Confocal microscopy visually confirmed uniform coprecipitation of BSA throughout the thickness of the filtration scaffolds. The designed system enables 3D mineralization through the thickness of porous materials, and provides the option of including coprecipitated biomolecular cues within the mineral layer. This approach of providing a 3D conductive and osteoinductive environment could be conducive to bone tissue regeneration. PMID:17618505

Calcium - urine

MedlinePlus

Urinary Ca+2; Kidney stones - calcium in urine; Renal calculi - calcium in your urine; Parathyroid - calcium in urine ... A 24-hour urine sample is most often needed: On day 1, urinate into the toilet when you wake up in the morning. ...

Porous Hydrogen-Bonded Organic Frameworks.

PubMed

Han, Yi-Fei; Yuan, Ying-Xue; Wang, Hong-Bo

2017-02-13

Ordered porous solid-state architectures constructed via non-covalent supramolecular self-assembly have attracted increasing interest due to their unique advantages and potential applications. Porous metal-coordination organic frameworks (MOFs) are generated by the assembly of metal coordination centers and organic linkers. Compared to MOFs, porous hydrogen-bonded organic frameworks (HOFs) are readily purified and recovered via simple recrystallization. However, due to lacking of sufficiently ability to orientate self-aggregation of building motifs in predictable manners, rational design and preparation of porous HOFs are still challenging. Herein, we summarize recent developments about porous HOFs and attempt to gain deeper insights into the design strategies of basic building motifs.

Genetically Encoded Calcium Indicators For Studying Long-Term Calcium Dynamics During Apoptosis

PubMed Central

Garcia, M. Iveth; Chen, Jessica J.; Boehning, Darren

2017-01-01

Intracellular calcium release is essential for regulating almost all cellular functions. Specific spatio-temporal patterns of cytosolic calcium elevations are critical determinants of cell fate in response to pro-apoptotic cellular stressors. As the apoptotic program can take hours or days, measurement of long-term calcium dynamics are essential for understanding the mechanistic role of calcium in apoptotic cell death. Due to the technical limitations of using calcium-sensitive dyes to measure cytosolic calcium little is known about long-term calcium dynamics in living cells after treatment with apoptosis-inducing drugs. Genetically encoded calcium indicators could potentially overcome some of the limitations of calcium-sensitive dyes. Here, we compared the performance of the genetically encoded calcium indicators GCaMP6s and GCaMP6f with the ratiometric dye Fura-2. GCaMP6s performed as well or better than Fura-2 in detecting agonist-induced calcium transients. We then examined the utility of GCaMP6s for continuously measuring apoptotic calcium release over the course of ten hours after treatment with staurosporine. We found that GCaMP6s was suitable for measuring apoptotic calcium release over long time courses and revealed significant heterogeneity in calcium release dynamics in individual cells challenged with staurosporine. Our results suggest GCaMP6s is an excellent indicator for monitoring long-term changes cytosolic calcium during apoptosis. PMID:28073595

Metabolic and miRNA Profiling of TMV Infected Plants Reveals Biphasic Temporal Changes

PubMed Central

Bazzini, Ariel A.; Manacorda, Carlos A.; Tohge, Takayuki; Conti, Gabriela; Rodriguez, Maria C.; Nunes-Nesi, Adriano; Villanueva, Sofía; Fernie, Alisdair R.; Carrari, Fernando; Asurmendi, Sebastian

2011-01-01

Plant viral infections induce changes including gene expression and metabolic components. Identification of metabolites and microRNAs (miRNAs) differing in abundance along infection may provide a broad view of the pathways involved in signaling and defense that orchestrate and execute the response in plant-pathogen interactions. We used a systemic approach by applying both liquid and gas chromatography coupled to mass spectrometry to determine the relative level of metabolites across the viral infection, together with a miRs profiling using a micro-array based procedure. Systemic changes in metabolites were characterized by a biphasic response after infection. The first phase, detected at one dpi, evidenced the action of a systemic signal since no virus was detected systemically. Several of the metabolites increased at this stage were hormone-related. miRs profiling after infection also revealed a biphasic alteration, showing miRs alteration at 5 dpi where no virus was detected systemically and a late phase correlating with virus accumulation. Correlation analyses revealed a massive increase in the density of correlation networks after infection indicating a complex reprogramming of the regulatory pathways, either in response to the plant defense mechanism or to the virus infection itself. Our data propose the involvement of a systemic signaling on early miRs alteration. PMID:22174812

Exocyst sec5 regulates exocytosis of newcomer insulin granules underlying biphasic insulin secretion.

PubMed

Xie, Li; Zhu, Dan; Kang, Youhou; Liang, Tao; He, Yu; Gaisano, Herbert Y

2013-01-01

The exocyst complex subunit Sec5 is a downstream effector of RalA-GTPase which promotes RalA-exocyst interactions and exocyst assembly, serving to tether secretory granules to docking sites on the plasma membrane. We recently reported that RalA regulates biphasic insulin secretion in pancreatic islet β cells in part by tethering insulin secretory granules to Ca(2+) channels to assist excitosome assembly. Here, we assessed β cell exocytosis by patch clamp membrane capacitance measurement and total internal reflection fluorescence microscopy to investigate the role of Sec5 in regulating insulin secretion. Sec5 is present in human and rodent islet β cells, localized to insulin granules. Sec5 protein depletion in rat INS-1 cells inhibited depolarization-induced release of primed insulin granules from both readily-releasable pool and mobilization from the reserve pool. This reduction in insulin exocytosis was attributed mainly to reduction in recruitment and exocytosis of newcomer insulin granules that undergo minimal docking time at the plasma membrane, but which encompassed a larger portion of biphasic glucose stimulated insulin secretion. Sec5 protein knockdown had little effect on predocked granules, unless vigorously stimulated by KCl depolarization. Taken together, newcomer insulin granules in β cells are more sensitive than predocked granules to Sec5 regulation.

A Physicochemically Optimized and Neuroconductive Biphasic Nerve Guidance Conduit for Peripheral Nerve Repair.

PubMed

Ryan, Alan J; Lackington, William A; Hibbitts, Alan J; Matheson, Austyn; Alekseeva, Tijna; Stejskalova, Anna; Roche, Phoebe; O'Brien, Fergal J

2017-12-01

Clinically available hollow nerve guidance conduits (NGCs) have had limited success in treating large peripheral nerve injuries. This study aims to develop a biphasic NGC combining a physicochemically optimized collagen outer conduit to bridge the transected nerve, and a neuroconductive hyaluronic acid-based luminal filler to support regeneration. The outer conduit is mechanically optimized by manipulating crosslinking and collagen density, allowing the engineering of a high wall permeability to mitigate the risk of neuroma formation, while also maintaining physiologically relevant stiffness and enzymatic degradation tuned to coincide with regeneration rates. Freeze-drying is used to seamlessly integrate the luminal filler into the conduit, creating a longitudinally aligned pore microarchitecture. The luminal stiffness is modulated to support Schwann cells, with laminin incorporation further enhancing bioactivity by improving cell attachment and metabolic activity. Additionally, this biphasic NGC is shown to support neurogenesis and gliogenesis of neural progenitor cells and axonal outgrowth from dorsal root ganglia. These findings highlight the paradigm that a successful NGC requires the concerted optimization of both a mechanical support phase capable of bridging a nerve defect and a neuroconductive phase with an architecture capable of supporting both Schwann cells and neurons in order to achieve functional regenerative outcome. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The effect of variable calcium and very low calcium diets on human calcium metabolism. Ph.D. Thesis. Final Report

NASA Technical Reports Server (NTRS)

Chu, J.

1971-01-01

The effects of a very low calcium diet, with variable high and low protein intake, on the dynamics of calcium metabolism and the mechanism of calciuretics, are examined. The experiment, using male subjects, was designed to study the role of intestinal calcium absorption on urinary calcium excretion, and the rate of production of endogeneously secreted calcium in the gastrointestinal tract. The study showed an average of 70% fractional absorption rate during very low calcium intake, and that a decrease in renal tubular reabsorption of calcium is responsible for calciuretic effects of high protein intake. The study also indicates that there is a tendency to develop osteoporosis after long periods of low calcium intake, especially with a concurrent high protein intake.

The activity of calcium in calcium-metal-fluoride fluxes

NASA Astrophysics Data System (ADS)

Ochifuji, Yuichiro; Tsukihashi, Fumitaka; Sano, Nobuo

1995-08-01

The standard Gibbs energy of reaction Ca (1) + O (mass pct, in Zr) = CaO (s) has been determined as follows by equilibrating molten calcium with solid zirconium in a CaO crucible: Δ G° = -64,300(±700) + 19.8(±3.5) T J/mol (1373 to 1623 K) The activities of calcium in the CaOsatd-Ca- MF2 ( M: Ca, Ba, Mg) and CaOsatd-Ca-NaF systems were measured as a function of calcium composition at high calcium contents at 1473 K on the basis of the standard Gibbs energy. The activities of calcium increase in the order of CaF2, BaF2, and MgF2 at the same calcium fraction of these fluxes. The observed activities are compared with those estimated by using the Temkin model for ionic solutions. Furthermore, the possibility of the removal of tramp elements such as tin, arsenic, antimony, bismuth, and lead from carbon-saturated iron by using calcium-metal-fluoride fluxes is discussed.

Biphasic fermentation is an efficient strategy for the overproduction of δ-endotoxin from Bacillus thuringiensis.

PubMed

Jisha, Veloorvalappil Narayanan; Smitha, Robinson Babysarojam; Priji, Prakasan; Sajith, Sreedharan; Benjamin, Sailas

2015-02-01

This study illustrates a biphasic solid-state fermentation (SSF) strategy for the overproduction of δ-endotoxin from Bacillus thuringiensis subsp. kurstaki (Btk) and also purification of δ-endotoxin from the solid-fermented medium. The fermentation strategy had two phases (biphasic); i.e., the first short phase was semisolid state (12 h), and the remaining long phase was strict SSF. To achieve the biphasic SSF, after 12 h (150 rpm, 37 °C) fermentation of the medium [Luria-Bertani (LB) supplemented with 30 % (w/v) raw soybean flour (phase I)], the supernatant in it was completely centrifuged out (1,000 × g, 10 min) aseptically for harvesting the extracellular enzymes as by-product. The resultant wet solid matter without free-flowing liquid but with embedded Btk was incubated 60 h more (phase II) for enhancing δ-endotoxin production at static condition (37 °C). Coupled with this, δ-endotoxin was purified by the modified phase separation method, and its purity was physically confirmed by both staining and microscopic techniques. The maximum δ-endotoxin yield from solid medium (48 h) was 15.8 mg/mL (recovery was 55-59 %) LB-equivalent, while that of LB control (recovery was 95 %) was only 0.43 mg/mL (72 h), i.e., thus, in comparison, 36.74-fold more yield in solid medium obtained by 24 h less gestation period. The purified crystal proteins showed apparent molecular weights (MWs) of 45, 35, and 6 kDa on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Briefly, this unique study physically demonstrates how Btk δ-endotoxin is purified (95-99 % purity) from solid-fermented matter for the first time, coupled with its overproduction at the expense of only 21.5 % higher production cost.

Lignocellulose fractionation into furfural and glucose by AlCl3-catalyzed DES/MIBK biphasic pretreatment.

PubMed

Wang, Zhi-Kun; Shen, Xiao-Jun; Chen, Jun-Jie; Jiang, Ying-Qiu; Hu, Zhi-Yan; Wang, Xing; Liu, Li

2018-06-01

Herein, an efficient DES/MIBK biphasic pretreatment system for preparation of furfural and fermentable glucose from lignocellulose was developed with AlCl 3 as catalysis. The low-cost and renewable DES (Choline chloride-Oxalic acid) served not only as a Brønsted acid catalyst, but also as a pretreatment solvent in present work, and MIBK as an extracting reagent which can increase the yield of furfural in DES phase. The effects of this biphasic pretreatment on the furfural yield and saccharification of the lignocellulose before and after pretreatment were explored using HPLC, HAPEC, FT-IR, XRD and SEM. Under the best pretreatment condition (at 140 °C for 90 min), furfural could be obtained in 70.3% yield and 80.8% of the pretreated lignocellulose was saccharified, which was 8.4 times higher than that of the raw lignocellulose without pretreatment. In a word, this pretreatment system can be considered as a potential technique for efficient valorization of lignocellulose for production of furfural and fermentable glucose. Copyright © 2018. Published by Elsevier B.V.

Online Epileptic Seizure Prediction Using Wavelet-Based Bi-Phase Correlation of Electrical Signals Tomography.

PubMed

Vahabi, Zahra; Amirfattahi, Rasoul; Shayegh, Farzaneh; Ghassemi, Fahimeh

2015-09-01

Considerable efforts have been made in order to predict seizures. Among these methods, the ones that quantify synchronization between brain areas, are the most important methods. However, to date, a practically acceptable result has not been reported. In this paper, we use a synchronization measurement method that is derived according to the ability of bi-spectrum in determining the nonlinear properties of a system. In this method, first, temporal variation of the bi-spectrum of different channels of electro cardiography (ECoG) signals are obtained via an extended wavelet-based time-frequency analysis method; then, to compare different channels, the bi-phase correlation measure is introduced. Since, in this way, the temporal variation of the amount of nonlinear coupling between brain regions, which have not been considered yet, are taken into account, results are more reliable than the conventional phase-synchronization measures. It is shown that, for 21 patients of FSPEEG database, bi-phase correlation can discriminate the pre-ictal and ictal states, with very low false positive rates (FPRs) (average: 0.078/h) and high sensitivity (100%). However, the proposed seizure predictor still cannot significantly overcome the random predictor for all patients.

Genetically encoded calcium indicators for studying long-term calcium dynamics during apoptosis.

PubMed

Garcia, M Iveth; Chen, Jessica J; Boehning, Darren

2017-01-01

Intracellular calcium release is essential for regulating almost all cellular functions. Specific spatio-temporal patterns of cytosolic calcium elevations are critical determinants of cell fate in response to pro-apoptotic cellular stressors. As the apoptotic program can take hours or days, measurement of long-term calcium dynamics are essential for understanding the mechanistic role of calcium in apoptotic cell death. Due to the technical limitations of using calcium-sensitive dyes to measure cytosolic calcium little is known about long-term calcium dynamics in living cells after treatment with apoptosis-inducing drugs. Genetically encoded calcium indicators could potentially overcome some of the limitations of calcium-sensitive dyes. Here, we compared the performance of the genetically encoded calcium indicators GCaMP6s and GCaMP6f with the ratiometric dye Fura-2. GCaMP6s performed as well or better than Fura-2 in detecting agonist-induced calcium transients. We then examined the utility of GCaMP6s for continuously measuring apoptotic calcium release over the course of ten hours after treatment with staurosporine. We found that GCaMP6s was suitable for measuring apoptotic calcium release over long time courses and revealed significant heterogeneity in calcium release dynamics in individual cells challenged with staurosporine. Our results suggest GCaMP6s is an excellent indicator for monitoring long-term changes cytosolic calcium during apoptosis. Copyright © 2017 Elsevier Ltd. All rights reserved.

Electronic and structural characteristics of zinc-blende wurtzite biphasic homostructure GaN nanowires

DOE PAGES

Jacobs, Benjamin W.; Ayres, Virginia M.; Petkov, Mihail P.; ...

2007-04-07

Here, we report a new biphasic crystalline wurtzite/zinc-blende homostructure in gallium nitride nanowires. Cathodoluminescence was used to quantitatively measure the wurtzite and zinc-blende band gaps. High-resolution transmission electron microscopy was used to identify distinct wurtzite and zinc-blende crystalline phases within single nanowires through the use of selected area electron diffraction, electron dispersive spectroscopy, electron energy loss spectroscopy, and fast Fourier transform techniques. A mechanism for growth is identified.

Electronic and structural characteristics of zinc-blende wurtzite biphasic homostructure GaN nanowires.

PubMed

Jacobs, Benjamin W; Ayres, Virginia M; Petkov, Mihail P; Halpern, Joshua B; He, Maoqi; Baczewski, Andrew D; McElroy, Kaylee; Crimp, Martin A; Zhang, Jiaming; Shaw, Harry C

2007-05-01

We report a new biphasic crystalline wurtzite/zinc-blende homostructure in gallium nitride nanowires. Cathodoluminescence was used to quantitatively measure the wurtzite and zinc-blende band gaps. High-resolution transmission electron microscopy was used to identify distinct wurtzite and zinc-blende crystalline phases within single nanowires through the use of selected area electron diffraction, electron dispersive spectroscopy, electron energy loss spectroscopy, and fast Fourier transform techniques. A mechanism for growth is identified.

Calcium orthophosphates

PubMed Central

Dorozhkin, Sergey V.

2011-01-01

The present overview is intended to point the readers’ attention to the important subject of calcium orthophosphates. This type of materials is of special significance for human beings, because they represent the inorganic part of major normal (bones, teeth and antlers) and pathological (i.e., those appearing due to various diseases) calcified tissues of mammals. For example, atherosclerosis results in blood vessel blockage caused by a solid composite of cholesterol with calcium orthophosphates, while dental caries and osteoporosis mean a partial decalcification of teeth and bones, respectively, that results in replacement of a less soluble and harder biological apatite by more soluble and softer calcium hydrogenphosphates. Therefore, the processes of both normal and pathological calcifications are just an in vivo crystallization of calcium orthophosphates. Similarly, dental caries and osteoporosis might be considered an in vivo dissolution of calcium orthophosphates. Thus, calcium orthophosphates hold a great significance for humankind, and in this paper, an overview on the current knowledge on this subject is provided. PMID:23507744

Acute Biphasic Effects of Ayahuasca

PubMed Central

Schenberg, Eduardo Ekman; Alexandre, João Felipe Morel; Filev, Renato; Cravo, Andre Mascioli; Sato, João Ricardo; Muthukumaraswamy, Suresh D.; Yonamine, Maurício; Waguespack, Marian; Lomnicka, Izabela; Barker, Steven A.; da Silveira, Dartiu Xavier

2015-01-01

Ritual use of ayahuasca, an amazonian Amerindian medicine turned sacrament in syncretic religions in Brazil, is rapidly growing around the world. Because of this internationalization, a comprehensive understanding of the pharmacological mechanisms of action of the brew and the neural correlates of the modified states of consciousness it induces is important. Employing a combination of electroencephalogram (EEG) recordings and quantification of ayahuasca's compounds and their metabolites in the systemic circulation we found ayahuasca to induce a biphasic effect in the brain. This effect was composed of reduced power in the alpha band (8–13 Hz) after 50 minutes from ingestion of the brew and increased slow- and fast-gamma power (30–50 and 50–100 Hz, respectively) between 75 and 125 minutes. Alpha power reductions were mostly located at left parieto-occipital cortex, slow-gamma power increase was observed at left centro-parieto-occipital, left fronto-temporal and right frontal cortices while fast-gamma increases were significant at left centro-parieto-occipital, left fronto-temporal, right frontal and right parieto-occipital cortices. These effects were significantly associated with circulating levels of ayahuasca’s chemical compounds, mostly N,N-dimethyltryptamine (DMT), harmine, harmaline and tetrahydroharmine and some of their metabolites. An interpretation based on a cognitive and emotional framework relevant to the ritual use of ayahuasca, as well as it's potential therapeutic effects is offered. PMID:26421727

Acute Biphasic Effects of Ayahuasca.

PubMed

Schenberg, Eduardo Ekman; Alexandre, João Felipe Morel; Filev, Renato; Cravo, Andre Mascioli; Sato, João Ricardo; Muthukumaraswamy, Suresh D; Yonamine, Maurício; Waguespack, Marian; Lomnicka, Izabela; Barker, Steven A; da Silveira, Dartiu Xavier

2015-01-01

Ritual use of ayahuasca, an amazonian Amerindian medicine turned sacrament in syncretic religions in Brazil, is rapidly growing around the world. Because of this internationalization, a comprehensive understanding of the pharmacological mechanisms of action of the brew and the neural correlates of the modified states of consciousness it induces is important. Employing a combination of electroencephalogram (EEG) recordings and quantification of ayahuasca's compounds and their metabolites in the systemic circulation we found ayahuasca to induce a biphasic effect in the brain. This effect was composed of reduced power in the alpha band (8-13 Hz) after 50 minutes from ingestion of the brew and increased slow- and fast-gamma power (30-50 and 50-100 Hz, respectively) between 75 and 125 minutes. Alpha power reductions were mostly located at left parieto-occipital cortex, slow-gamma power increase was observed at left centro-parieto-occipital, left fronto-temporal and right frontal cortices while fast-gamma increases were significant at left centro-parieto-occipital, left fronto-temporal, right frontal and right parieto-occipital cortices. These effects were significantly associated with circulating levels of ayahuasca's chemical compounds, mostly N,N-dimethyltryptamine (DMT), harmine, harmaline and tetrahydroharmine and some of their metabolites. An interpretation based on a cognitive and emotional framework relevant to the ritual use of ayahuasca, as well as it's potential therapeutic effects is offered.

Image-based Modeling of Biofilm-induced Calcium Carbonate Precipitation

NASA Astrophysics Data System (ADS)

Connolly, J. M.; Rothman, A.; Jackson, B.; Klapper, I.; Cunningham, A. B.; Gerlach, R.

2013-12-01

Pore scale biological processes in the subsurface environment are important to understand in relation to many engineering applications including environmental contaminant remediation, geologic carbon sequestration, and petroleum production. Specifically, biofilm induced calcium carbonate precipitation has been identified as an attractive option to reduce permeability in a lasting way in the subsurface. This technology may be able to replace typical cement-based grouting in some circumstances; however, pore-scale processes must be better understood for it to be applied in a controlled manor. The work presented will focus on efforts to observe biofilm growth and ureolysis-induced mineral precipitation in micro-fabricated flow cells combined with finite element modelling as a tool to predict local chemical gradients of interest (see figure). We have been able to observe this phenomenon over time using a novel model organism that is able to hydrolyse urea and express a fluorescent protein allowing for non-invasive observation over time with confocal microscopy. The results of this study show the likely existence of a wide range of local saturation indices even in a small (1 cm length scale) experimental system. Interestingly, the locations of high predicted index do not correspond to the locations of higher precipitation density, highlighting the need for further understanding. Figure 1 - A micro-fabricated flow cell containing biofilm-induced calcium carbonate precipitation. (A) Experimental results: Active biofilm is in green and dark circles are calcium carbonate crystals. Note the channeling behavior in the top of the image, leaving a large hydraulically inactive area in the biofilm mass. (B) Finite element model: The prediction of relative saturation of calcium carbonate (as calcite). Fluid enters the system at a low saturation state (blue) but areas of high supersaturation (red) are predicted within the hydraulically inactive area in the biofilm. If only effluent

Evolution of a mini-scale biphasic dissolution model: Impact of model parameters on partitioning of dissolved API and modelling of in vivo-relevant kinetics.

PubMed

Locher, Kathrin; Borghardt, Jens M; Frank, Kerstin J; Kloft, Charlotte; Wagner, Karl G

2016-08-01

Biphasic dissolution models are proposed to have good predictive power for the in vivo absorption. The aim of this study was to improve our previously introduced mini-scale dissolution model to mimic in vivo situations more realistically and to increase the robustness of the experimental model. Six dissolved APIs (BCS II) were tested applying the improved mini-scale biphasic dissolution model (miBIdi-pH-II). The influence of experimental model parameters including various excipients, API concentrations, dual paddle and its rotation speed was investigated. The kinetics in the biphasic model was described applying a one- and four-compartment pharmacokinetic (PK) model. The improved biphasic dissolution model was robust related to differing APIs and excipient concentrations. The dual paddle guaranteed homogenous mixing in both phases; the optimal rotation speed was 25 and 75rpm for the aqueous and the octanol phase, respectively. A one-compartment PK model adequately characterised the data of fully dissolved APIs. A four-compartment PK model best quantified dissolution, precipitation, and partitioning also of undissolved amounts due to realistic pH profiles. The improved dissolution model is a powerful tool for investigating the interplay between dissolution, precipitation and partitioning of various poorly soluble APIs (BCS II). In vivo-relevant PK parameters could be estimated applying respective PK models. Copyright © 2016 Elsevier B.V. All rights reserved.

Comparison of low-energy versus high-energy biphasic defibrillation shocks following prolonged ventricular fibrillation.

PubMed

Walcott, Gregory P; Melnick, Sharon B; Killingsworth, Cheryl R; Ideker, Raymond E

2010-01-01

Since the initial development of the defibrillator, there has been concern that, while delivery of a large electric shock would stop fibrillation, it would also cause damage to the heart. This concern has been raised again with the development of the biphasic defibrillator. To compare defibrillation efficacy, postshock cardiac function, and troponin I levels following 150-J and 360-J shocks. Nineteen swine were anesthetized with isoflurane and instrumented with pressure catheters in the left ventricle, aorta, and right atrium. The animals were fibrillated for 6 minutes, followed by defibrillation with either low-energy (n = 8) or high-energy (n = 11) shocks. After defibrillation, chest compressions were initiated and continued until return of spontaneous circulation (ROSC). Epinephrine, 0.01 mg/kg every 3 minutes, was given for arterial blood pressure < 50 mmHg. Hemodynamic parameters were recorded for four hours. Transthoracic echocardiography was performed and troponin I levels were measured at baseline and four hours following ventricular fibrillation (VF). Survival rates at four hours were not different between the two groups (low-energy, 5 of 8; high-energy, 7 of 11). Results for arterial blood pressure, positive dP/dt (first derivative of pressure measured over time, a measure of left ventricular contractility), and negative dP/dt at the time of lowest arterial blood pressure (ABP) following ROSC were not different between the two groups (p = not significant [NS]), but were lower than at baseline. All hemodynamic measures returned to baseline by four hours. Ejection fractions, stroke volumes, and cardiac outputs were not different between the two groups at four hours. Troponin I levels at four hours were not different between the two groups (12 +/- 11 ng/mL versus 21 +/- 26 ng/mL, p = NS) but were higher at four hours than at baseline (19 +/- 19 ng/mL versus 0.8 +/- 0.5 ng/mL, p < 0.05, groups combined). Biphasic 360-J shocks do not cause more cardiac damage

Laboratory study on the high-temperature capture of HCl gas by dry-injection of calcium-based sorbents.

PubMed

Shemwell, B; Levendis, Y A; Simons, G A

2001-01-01

This is a laboratory study on the reduction of combustion-generated hydrochloric acid (HCl) emissions by in-furnace dry-injection of calcium-based sorbents. HCl is a hazardous gaseous pollutant emitted in significant quantities by municipal and hazardous waste incinerators, coal-fired power plants, and other industrial furnaces. Experiments were conducted in a laboratory furnace at gas temperatures of 600-1000 degrees C. HCl gas diluted with N2, and sorbent powders fluidized in a stream of air were introduced into the furnace concurrently. Chlorination of the sorbents occurred in the hot zone of the furnace at gas residence times approximately 1 s. The sorbents chosen for these experiments were calcium formate (CF), calcium magnesium acetate (CMA), calcium propionate (CP), calcium oxide (CX), and calcium carbonate (CC). Upon release of organic volatiles, sorbents calcine to CaO at approximately 700 degrees C, and react with the HCl according to the reaction CaO + 2HCl <=> CaCl2 + H2O. At the lowest temperature case examined herein, 600 degrees C, direct reaction of HCl with CaCO3 may also be expected. The effectiveness of the sorbents to capture HCl was interpreted using the "pore tree" mathematical model for heterogeneous diffusion reactions. Results show that the thin-walled, highly porous cenospheres formed from the pyrolysis and calcination of CF, CMA, and CP exhibited high relative calcium utilization at the upper temperatures of this study. Relative utilizations under these conditions reached 80%. The less costly low-porosity sorbents, calcium carbonate and calcium oxide also performed well. Calcium carbonate reached a relative utilization of 54% in the mid-temperature range, while the calcium oxide reached an 80% relative utilization at the lowest temperature examined. The data matched theoretical predictions of sorbent utilization using the mathematical model, with activation energy and pre-exponential factors for the calcination reaction of 17,000 K and

Calcium

MedlinePlus

... Guidelines for Americans and the U.S. Department of Agriculture's MyPlate . Where can I find out more about ... on food sources of calcium: U.S. Department of Agriculture's (USDA) National Nutrient Database Nutrient List for calcium ( ...

"Washing-out" ionic liquids from polyethylene glycol to form aqueous biphasic systems.

PubMed

Tomé, Luciana I N; Pereira, Jorge F B; Rogers, Robin D; Freire, Mara G; Gomes, José R B; Coutinho, João A P

2014-02-14

The molecular-level mechanisms behind the formation of aqueous biphasic systems (ABS) composed of ionic liquids (ILs) and polymers are hitherto not completely understood. For the first time, it is herein shown that polymer-IL-based ABS are a result of a "washing-out" phenomenon, and not of a salting-out effect of the IL over the polymer as assumed in the past few years. Novel evidence is herein provided by experimental results combined with molecular dynamics (MD) simulations and density functional theory (DFT) calculations.

Controlled and reversible induction of differentiation and activation of adult human hepatocytes by a biphasic culture technique

PubMed Central

Auth, Marcus K.H.; Boost, Kim A.; Leckel, Kerstin; Beecken, Wolf-Dietrich; Engl, Tobias; Jonas, Dietger; Oppermann, Elsie; Hilgard, Philip; Markus, Bernd H.; Bechstein, Wolf-Otto; Blaheta, Roman A.

2005-01-01

AIM: Clinical application of human hepatocytes (HC) is hampered by the progressive loss of growth and differentiation in vitro. The object of the study was to evaluate the effect of a biphasic culture technique on expression and activation of growth factor receptors and differentiation of human adult HC. METHODS: Isolated HC were sequentially cultured in a hormone enriched differentiation medium (DM) containing nicotinamide, insulin, transferrin, selenium, and dexame-thasone or activation medium (AM) containing hepatocyte growth factor (HGF), epidermal growth factor (EGF), and granulocyte-macrophage colony-stimulating factor (GM-CSF). Expression, distribution and activation of the HC receptors (MET and EGFR) and the pattern of characteristic cytokeratin (CK) filaments were measured by fluorometry, confocal microscopy and Western blotting. RESULTS: In the biphasic culture system, HC underwent repeated cycles of activation (characterized by expression and activation of growth factor receptors) and re-differentiation (illustrated by distribution of typical filaments CK-18 but low or absent expression of CK-19). In AM increased expression of MET and EGFR was associated with receptor translocation into the cytoplasm and induction of atypical CK-19. In DM low expression of MET and EGFR was localized on the cell membrane and CK-19 was reduced. Receptor phosphorylation required embedding of HC in collagen type I gel. CONCLUSION: Control and reversible modulation of growth factor receptor activation of mature human HC can be accomplished in vitro, when defined signals from the extracellular matrix and sequential growth stimuli are provided. The biphasic technique helps overcome de-differentiation, which occurs during continuous stimulation by means of growth factors. PMID:15810072

Controlled and reversible induction of differentiation and activation of adult human hepatocytes by a biphasic culture technique.

PubMed

Auth, Marcus-K H; Boost, Kim A; Leckel, Kerstin; Beecken, Wolf-Dietrich; Engl, Tobias; Jonas, Dietger; Oppermann, Elsie; Hilgard, Philip; Markus, Bernd H; Bechstein, Wolf-Otto; Blaheta, Roman A

2005-04-14

Clinical application of human hepatocytes (HC) is hampered by the progressive loss of growth and differentiation in vitro. The object of the study was to evaluate the effect of a biphasic culture technique on expression and activation of growth factor receptors and differentiation of human adult HC. Isolated HC were sequentially cultured in a hormone enriched differentiation medium (DM) containing nicotinamide, insulin, transferrin, selenium, and dexame-thasone or activation medium (AM) containing hepatocyte growth factor (HGF), epidermal growth factor (EGF), and granulocyte-macrophage colony-stimulating factor (GM-CSF). Expression, distribution and activation of the HC receptors (MET and EGFR) and the pattern of characteristic cytokeratin (CK) filaments were measured by fluorometry, confocal microscopy and Western blotting. In the biphasic culture system, HC underwent repeated cycles of activation (characterized by expression and activation of growth factor receptors) and re-differentiation (illustrated by distribution of typical filaments CK-18 but low or absent expression of CK-19). In AM increased expression of MET and EGFR was associated with receptor translocation into the cytoplasm and induction of atypical CK-19. In DM low expression of MET and EGFR was localized on the cell membrane and CK-19 was reduced. Receptor phosphorylation required embedding of HC in collagen type I gel. Control and reversible modulation of growth factor receptor activation of mature human HC can be accomplished in vitro, when defined signals from the extracellular matrix and sequential growth stimuli are provided. The biphasic technique helps overcome de-differentiation, which occurs during continuous stimulation by means of growth factors.

Porous silicon carbide (SIC) semiconductor device

NASA Technical Reports Server (NTRS)

Shor, Joseph S. (Inventor); Kurtz, Anthony D. (Inventor)

1996-01-01

Porous silicon carbide is fabricated according to techniques which result in a significant portion of nanocrystallites within the material in a sub 10 nanometer regime. There is described techniques for passivating porous silicon carbide which result in the fabrication of optoelectronic devices which exhibit brighter blue luminescence and exhibit improved qualities. Based on certain of the techniques described porous silicon carbide is used as a sacrificial layer for the patterning of silicon carbide. Porous silicon carbide is then removed from the bulk substrate by oxidation and other methods. The techniques described employ a two-step process which is used to pattern bulk silicon carbide where selected areas of the wafer are then made porous and then the porous layer is subsequently removed. The process to form porous silicon carbide exhibits dopant selectivity and a two-step etching procedure is implemented for silicon carbide multilayers.

Selective formation of porous silicon

NASA Technical Reports Server (NTRS)

Fathauer, Jones (Inventor)

1993-01-01

A pattern of porous silicon is produced in the surface of a silicon substrate by forming a pattern of crystal defects in said surface, preferably by applying an ion milling beam through openings in a photoresist layer to the surface, and then exposing said surface to a stain etchant, such as HF:HNO3:H20. The defected crystal will preferentially etch to form a pattern of porous silicon. When the amorphous content of the porous silicon exceeds 70 percent, the porous silicon pattern emits visible light at room temperature.

Selective formation of porous silicon

NASA Technical Reports Server (NTRS)

Fathauer, Robert W. (Inventor); Jones, Eric W. (Inventor)

1993-01-01

A pattern of porous silicon is produced in the surface of a silicon substrate by forming a pattern of crystal defects in said surface, preferably by applying an ion milling beam through openings in a photoresist layer to the surface, and then exposing said surface to a stain etchant, such as HF:HNO3:H2O. The defected crystal will preferentially etch to form a pattern of porous silicon. When the amorphous content of the porous silicon exceeds 70 percent, the porous silicon pattern emits visible light at room temperature.

The improved biological response of shark tooth bioapatites in a comparative in vitro study with synthetic and bovine bone grafts.

PubMed

López-Álvarez, M; Pérez-Davila, S; Rodríguez-Valencia, C; González, P; Serra, J

2016-06-07

Autologous bone is considered to be the gold standard for bone tissue regeneration, providing more highly efficient functional responses compared to synthetic materials, and avoiding the rejection risks of allogenic grafts. However, it presents limitations for certain types of surgery due to its high resorption levels and donor site morbidity. Different biphasic synthetic composites, based onnon-apatitic calcium phosphates enriched with apatitic phases-such as hydroxyapatite, and bioderived bone grafts of bovine and porcine origin-are proposed as lower resorption materials due to their higher crystalline structure. The present work proposes two new sources of bioapatites for bone filler applications obtained from the dentine and enameloid of shark teeth, respectively. These bioapatites each present a characteristic apatite-based composition and additional enrichments of specific trace elements, such as magnesium and fluorine, with proven roles in bone metabolism. Their processing and physicochemical characterization (SEM, FT-Raman and XRD) is presented, together with an in vitro evaluation of osteogenic activity compared to a commercial bovine mineralized matrix and synthetic HA/β TCP grafts. The results proved the globular morphology (0.5-1.5 μm) and porosity (~50 μm and ~0.5-1 μm) of shark dentine bioapatites with biphasic composition: apatitic (hydroxyapatite and apatite-(CaF)), non-apatitic (whitlockite), and an apatitic phase (fluorapatite), organized in oriented crystals in enameloid bioapatites. An evaluation of the pre-osteoblast MC3T3-E1 morphology revealed the colonization of pores in dentine bioapatites and an aligned cell growth in the oriented enameloid crystals. A higher proliferation (p  <  0.01) was detected at up to 21 d in both the shark bioapatites and synthetic biphasic graft with respect to the bovine mineralized matrix. Finally, the great potential of porous biphasic dentine bioapatites enriched with Mg and the aligned

Aluminum hydroxide, calcium carbonate and calcium acetate in chronic intermittent hemodialysis patients.

PubMed

Janssen, M J; van der Kuy, A; ter Wee, P M; van Boven, W P

1996-02-01

Prevention of secondary hyperparathyroidism in uremia necessitates correction of hyperphosphatemia and hypocalcemia. In order to avoid aluminum toxicity, calcium containing phosphate binders are used increasingly, instead of aluminium hydroxide. Recent studies have shown that calcium acetate has many characteristics of an ideal phosphate binder. It is, for instance, a more readily soluble salt compared with calcium carbonate. This advantage might, however, disappear if calcium carbonate is taken on an empty stomach, a few minutes before meals. We examined the efficacy of three different phosphate binding agents in a randomized prospective study of 53 patients on regular hemodialysis. Bicarbonate dialyses were performed with a dialysate calcium concentration of 1.75 mmol/l. After a three-week wash-out period, patients received either aluminum hydroxide (control group), calcium acetate, or calcium carbonate as their phosphate binder. Patients were instructed to take the calcium salts a few minutes before meals on an empty stomach, and aluminum hydroxide during meals. Serum calcium, phosphate, intact parathormone, and alkaline phosphatase levels were determined every month. Patient compliance was estimated every month by asking the patients which phosphate binder and what daily dose they had used. Aluminum hydroxide tended to be the most effective phosphate binder. The mean +/- SEM required daily dose of calcium acetate at 12 months was 5.04 +/- 0.60 g, corresponding to 10.1 +/- 1.20 tablets of 500 mg. Co-medication with aluminum hydroxide, however, was needed (1.29 +/- 0.54 g per day, corresponding to 2.6 +/- 1.08 tablets of 500 mg). The required daily calcium carbonate dose appeared to be 2.71 +/- 0.48 g, corresponding to 5.4 +/- 0.95 capsules of 500 mg, with an adjuvant daily aluminum hydroxide dose of 0.69 +/- 0.27 g, corresponding to 1.4 +/- 0.55 tablets of 500 mg (p = 0.0055). Thus, the mean daily doses of elemental calcium were comparable between the calcium

A comparative biomechanical study of bone ingrowth in two porous hydroxyapatite bioceramics

NASA Astrophysics Data System (ADS)

Ren, Li-Mei; Todo, Mitsugu; Arahira, Takaaki; Yoshikawa, Hideki; Myoui, Akira

2012-12-01

Calcium phosphate-based bioceramics have been widely used as artificial bone substitute materials because of their superior biocompatibility and osteoconductivity. In the present study, mechanical properties changes of two hydroxyapatite (HA) ceramics induced by bone ingrowth were tested and evaluated in a rabbit model. Both materials (NEOBONE®, Apaceram-AX®) have highly interconnected pores with a porosity of 75-85%. The major structural difference between them lies in that Apaceram-AX® has micropores smaller than 10 micrometers in diameter, whereas NEOBONE® does not contain such micropores. Both materials were implanted into the femoral condyles of rabbits for the specified observation period (1, 5, 12, 24, and 48 weeks) and then evaluated by experimental approach in combination with finite element method (FEM). Results indicate that two porous bioceramics exhibit different degradability in vivo, and remarkably different variation of total stiffness, elastic modulus distribution, as well as strain energy density distribution calculated by FE simulation. These results demonstrate how the internal microstructures affect the progress of bone regeneration and mechanical properties with the duration of implantation, emphasizing the importance of biomaterial design tailored to various clinic applications. Additionally, this study showed a potential for applying the computational method to monitor the time-dependent biomechanical changes of implanted porous bioceramics.

Electrostatic-Assisted Liquefaction of Porous Carbons

DOE PAGES

Li, Peipei; Schott, Jennifer A.; Zhang, Jinshui; ...

2017-10-10

Porous liquids are a newly developed porous material that combine unique fluidity with permanent porosity, which exhibit promising functionalities for a variety of applications. However, the apparent incompatibility between fluidity and permanent porosity makes the stabilization of porous nanoparticle with still empty pores in the dense liquid phase a significant challenging. For this study, by exploiting the electrostatic interaction between carbon networks and polymerized ionic liquids, we demonstrate that carbon-based porous nanoarchitectures can be well stabilized in liquids to afford permanent porosity, and thus opens up a new approach to prepare porous carbon liquids. Furthermore, we hope this facile synthesismore » strategy can be widely applicated to fabricate other types of porous liquids, such as those (e.g., carbon nitride, boron nitride, metal–organic frameworks, covalent organic frameworks etc.) also having the electrostatic interaction with polymerized ionic liquids, evidently advancing the development and understanding of porous liquids.« less

Porous Silicon Nanowires

PubMed Central

Qu, Yongquan; Zhou, Hailong; Duan, Xiangfeng

2011-01-01

In this minreview, we summarize recent progress in the synthesis, properties and applications of a new type of one-dimensional nanostructures — single crystalline porous silicon nanowires. The growth of porous silicon nanowires starting from both p- and n-type Si wafers with a variety of dopant concentrations can be achieved through either one-step or two-step reactions. The mechanistic studies indicate the dopant concentration of Si wafers, oxidizer concentration, etching time and temperature can affect the morphology of the as-etched silicon nanowires. The porous silicon nanowires are both optically and electronically active and have been explored for potential applications in diverse areas including photocatalysis, lithium ion battery, gas sensor and drug delivery. PMID:21869999

Direct transformation of xylan-type hemicelluloses to furfural via SnCl₄ catalysts in aqueous and biphasic systems.

PubMed

Wang, Wenju; Ren, Junli; Li, Huiling; Deng, Aojie; Sun, Runcang

2015-05-01

Direct catalytic transformation of xylan-type hemicelluloses to furfural in the aqueous system and the biphasic system were comparatively investigated under mild conditions. Screening of several promising chlorides for conversion of beech xylan in the aqueous system revealed the Lewis acid SnCl4 was the most effective catalyst. Comparing to the single aqueous system, the bio-based 2-methyltetrahydrofuran (2-MTHF)/H2O biphasic system was more conducive to the synthesis of furfural, in which the highest furfural yield of 78.1% was achieved by using SnCl4 as catalysts under the optimized reaction conditions (150°C, 120 min). Additionally, the influences of xylan-type hemicelluloses with different chemical and structural features from beech, corncob and bagasse on the furfural production were studied. It was found that furfural yield to some extent was determined by the xylose content in hemicelluloses and also had relationships with the molecular weight of hemicelluloses and the degree of crystallization. Copyright © 2015 Elsevier Ltd. All rights reserved.

Porous biomorphic silicon carbide ceramics coated with hydroxyapatite as prospective materials for bone implants.

PubMed

Gryshkov, Oleksandr; Klyui, Nickolai I; Temchenko, Volodymyr P; Kyselov, Vitalii S; Chatterjee, Anamika; Belyaev, Alexander E; Lauterboeck, Lothar; Iarmolenko, Dmytro; Glasmacher, Birgit

2016-11-01

Porous and cytocompatible silicon carbide (SiC) ceramics derived from wood precursors and coated with bioactive hydroxyapatite (HA) and HA-zirconium dioxide (HA/ZrO2) composite are materials with promising application in engineering of bone implants due to their excellent mechanical and structural properties. Biomorphic SiC ceramics have been synthesized from wood (Hornbeam, Sapele, Tilia and Pear) using a forced impregnation method. The SiC ceramics have been coated with bioactive HA and HA/ZrO2 using effective gas detonation deposition approach (GDD). The surface morphology and cytotoxicity of SiC ceramics as well as phase composition and crystallinity of deposited coatings were analyzed. It has been shown that the porosity and pore size of SiC ceramics depend on initial wood source. The XRD and FTIR studies revealed the preservation of crystal structure and phase composition of in the HA coating, while addition of ZrO2 to the initial HA powder resulted in significant decomposition of the final HA/ZrO2 coating and formation of other calcium phosphate phases. In turn, NIH 3T3 cells cultured in medium exposed to coated and uncoated SiC ceramics showed high re-cultivation efficiency as well as metabolic activity. The recultivation efficiency of cells was the highest for HA-coated ceramics, whereas HA/ZrO2 coating improved the recultivation efficiency of cells as compared to uncoated SiC ceramics. The GDD method allowed generating homogeneous HA coatings with no change in calcium to phosphorus ratio. In summary, porous and cytocompatible bio-SiC ceramics with bioactive coatings show a great promise in construction of light, robust, inexpensive and patient-specific bone implants for clinical application. Copyright © 2016 Elsevier B.V. All rights reserved.

Porous silicon technology for integrated microsystems

NASA Astrophysics Data System (ADS)

Wallner, Jin Zheng

With the development of micro systems, there is an increasing demand for integrable porous materials. In addition to those conventional applications, such as filtration, wicking, and insulating, many new micro devices, including micro reactors, sensors, actuators, and optical components, can benefit from porous materials. Conventional porous materials, such as ceramics and polymers, however, cannot meet the challenges posed by micro systems, due to their incompatibility with standard micro-fabrication processes. In an effort to produce porous materials that can be used in micro systems, porous silicon (PS) generated by anodization of single crystalline silicon has been investigated. In this work, the PS formation process has been extensively studied and characterized as a function of substrate type, crystal orientation, doping concentration, current density and surfactant concentration and type. Anodization conditions have been optimized for producing very thick porous silicon layers with uniform pore size, and for obtaining ideal pore morphologies. Three different types of porous silicon materials: meso porous silicon, macro porous silicon with straight pores, and macro porous silicon with tortuous pores, have been successfully produced. Regular pore arrays with controllable pore size in the range of 2mum to 6mum have been demonstrated as well. Localized PS formation has been achieved by using oxide/nitride/polysilicon stack as masking materials, which can withstand anodization in hydrofluoric acid up to twenty hours. A special etching cell with electrolytic liquid backside contact along with two process flows has been developed to enable the fabrication of thick macro porous silicon membranes with though wafer pores. For device assembly, Si-Au and In-Au bonding technologies have been developed. Very low bonding temperature (˜200°C) and thick/soft bonding layers (˜6mum) have been achieved by In-Au bonding technology, which is able to compensate the potentially

Short-term effectiveness of bi-phase oscillatory waves versus hyperthermia for isolated long head biceps tendinopathy

PubMed Central

Oliva, Francesco; Via, Alessio Giai; Rossi, Silvio

2011-01-01

Summary Introduction: Long head biceps (LHB) tendinopathy is a common cause of anterior shoulder pain. Isolated LHB pathology is most common among younger people who practise overhead sports. The authors conducted a short-term prospective randomised study to test the effectiveness of two different methods for the treatment of isolated LHB tendinopathy: biphasic oscillatory waves and hyperthermia. Study design: The study is a prospective randomised study (Level II). Material and methods: The authors identified 20 patients who had clinical and ultrasound (US) evidence of LHB tendinopathy. No patient was a high-level athlete. The patients were randomly assigned to two groups. Group A (10 patients) was treated with bi-phasic oscillatory waves, while Group B received hyperthermia. During the treatment period, no other electromedical therapy, injections with corticosteroids, oral analgesics or nonsteroidal anti-inflammatory drugs were allowed. All the patients were assessed at baseline (T0), immediately after the end of the treatment period (T1) and 6 months after the end of treatment (T2) using a visual analogic scale (VAS) and Constant-Murley Score (CMS). Furthermore, all patients underwent US examinations at T0 and at T1. All the US examinations were performed by the same radiologist. Results: The VAS scores showed a highly statistically significant reduction of pain at T1 both in Group A (65%; p=0,004) and in Group B (50%; p=0,0002). The CMS also showed a statistically significant improvement between the pre-intervention, the post-treatment and the short-term follow-up in both groups. In addition, the peritendinous fluid evident on US examination at T0 was no longer present in all cases at T1. Conclusion: These findings suggest that both bi-phasic oscillatory waves and hyperthermia are able to relieve pain in patients with isolated LHB tendinopathy. This is a Class II level of evidence. PMID:23738257

Biological evaluation and finite-element modeling of porous poly(para-phenylene) for orthopaedic implants.

PubMed

Ahn, Hyunhee; Patel, Ravi R; Hoyt, Anthony J; Lin, Angela S P; Torstrick, F Brennan; Guldberg, Robert E; Frick, Carl P; Carpenter, R Dana; Yakacki, Christopher M; Willett, Nick J

2018-05-01

Poly(para-phenylene) (PPP) is a novel aromatic polymer with higher strength and stiffness than polyetheretherketone (PEEK), the gold standard material for polymeric load-bearing orthopaedic implants. The amorphous structure of PPP makes it relatively straightforward to manufacture different architectures, while maintaining mechanical properties. PPP is promising as a potential orthopaedic material; however, the biocompatibility and osseointegration have not been well investigated. The objective of this study was to evaluate biological and mechanical behavior of PPP, with or without porosity, in comparison to PEEK. We examined four specific constructs: 1) solid PPP, 2) solid PEEK, 3) porous PPP and 4) porous PEEK. Pre-osteoblasts (MC3T3) exhibited similar cell proliferation among the materials. Osteogenic potential was significantly increased in the porous PPP scaffold as assessed by ALP activity and calcium mineralization. In vivo osseointegration was assessed by implanting the cylindrical materials into a defect in the metaphysis region of rat tibiae. Significantly more mineral ingrowth was observed in both porous scaffolds compared to the solid scaffolds, and porous PPP had a further increase compared to porous PEEK. Additionally, porous PPP implants showed bone formation throughout the porous structure when observed via histology. A computational simulation of mechanical push-out strength showed approximately 50% higher interfacial strength in the porous PPP implants compared to the porous PEEK implants and similar stress dissipation. These data demonstrate the potential utility of PPP for orthopaedic applications and show improved osseointegration when compared to the currently available polymeric material. PEEK has been widely used in orthopaedic surgery; however, the ability to utilize PEEK for advanced fabrication methods, such as 3D printing and tailored porosity, remain challenging. We present a promising new orthopaedic biomaterial, Poly

Gravimetric Determination of Calcium as Calcium Carbonate Hydrate.

ERIC Educational Resources Information Center

Henrickson, Charles H.; Robinson, Paul R.

1979-01-01

The gravimetric determination of calcium as calcium carbonate is described. This experiment is suitable for undergraduate quantitative analysis laboratories. It is less expensive than determination of chloride as silver chloride. (BB)

Progranulin haploinsufficiency causes biphasic social dominance abnormalities in the tube test.

PubMed

Arrant, A E; Filiano, A J; Warmus, B A; Hall, A M; Roberson, E D

2016-07-01

Loss-of-function mutations in progranulin (GRN) are a major autosomal dominant cause of frontotemporal dementia (FTD), a neurodegenerative disorder in which social behavior is disrupted. Progranulin-insufficient mice, both Grn(+/-) and Grn(-/-) , are used as models of FTD due to GRN mutations, with Grn(+/-) mice mimicking the progranulin haploinsufficiency of FTD patients with GRN mutations. Grn(+/-) mice have increased social dominance in the tube test at 6 months of age, although this phenotype has not been reported in Grn(-/-) mice. In this study, we investigated how the tube test phenotype of progranulin-insufficient mice changes with age, determined its robustness under several testing conditions, and explored the associated cellular mechanisms. We observed biphasic social dominance abnormalities in Grn(+/-) mice: at 6-8 months, Grn(+/-) mice were more dominant than wild-type littermates, while after 9 months of age, Grn(+/-) mice were less dominant. In contrast, Grn(-/-) mice did not exhibit abnormal social dominance, suggesting that progranulin haploinsufficiency has distinct effects from complete progranulin deficiency. The biphasic tube test phenotype of Grn(+/-) mice was associated with abnormal cellular signaling and neuronal morphology in the amygdala and prefrontal cortex. At 6-9 months, Grn(+/-) mice exhibited increased mTORC2/Akt signaling in the amygdala and enhanced dendritic arbors in the basomedial amygdala, and at 9-16 months Grn(+/-) mice exhibited diminished basal dendritic arbors in the prelimbic cortex. These data show a progressive change in tube test dominance in Grn(+/-) mice and highlight potential underlying mechanisms by which progranulin insufficiency may disrupt social behavior. © 2016 John Wiley & Sons Ltd and International Behavioural and Neural Genetics Society.

Calcium binding to Procambarus clarkii sarcoplasmic calcium binding protein splice variants.

PubMed

Rohrback, Suzanne E; Wheatly, Michele G; Gillen, Christopher M

2015-01-01

Sarcoplasmic calcium binding protein (SCP) is a high-affinity calcium buffering protein expressed in muscle of crayfish and other invertebrates. In previous work, we identified three splice variants of Procambarus clarkii SCP (pcSCP1a, pcSCP1b, and pcSCP1c) that differ in a 37 amino acid region that lies mainly between the 2nd and 3ed EF-hand calcium binding domain. To evaluate the function of the proteins encoded by the pcSCP1 transcripts, we produced recombinant pcSCP1 and used tryptophan fluorescence to characterize calcium binding. Tryptophan fluorescence of pcSCP1a decreased in response to increased calcium, while tryptophan fluorescence of the pcSCP1b and pcSCP1c variants increased. We estimated calcium binding constants and Hill coefficients with two different equations: the standard Hill equation and a modified Hill equation that accounts for contributions from two different tryptophans. The approaches gave similar results. Steady-state calcium binding constants (Kd) ranged from 2.7±0.7×10(-8)M to 5.6±0.1×10(-7)M, consistent with previous work. Variants displayed significantly different apparent calcium affinities, which were decreased in the presence of magnesium. Calcium Kd was lowest for pcSCP1a and highest for pcSCP1c. Site-directed mutagenesis of pcSCP1c residues to the amino acids of pcSCP1b decreased the calcium Kd, identifying residues outside the EF-hand domains that contribute to calcium binding in crayfish SCP. Copyright © 2014 Elsevier Inc. All rights reserved.

Why Calcium? How Calcium Became the Best Communicator*

PubMed Central

Carafoli, Ernesto; Krebs, Joachim

2016-01-01

Calcium carries messages to virtually all important functions of cells. Although it was already active in unicellular organisms, its role became universally important after the transition to multicellular life. In this Minireview, we explore how calcium ended up in this privileged position. Most likely its unique coordination chemistry was a decisive factor as it makes its binding by complex molecules particularly easy even in the presence of large excesses of other cations, e.g. magnesium. Its free concentration within cells can thus be maintained at the very low levels demanded by the signaling function. A large cadre of proteins has evolved to bind or transport calcium. They all contribute to buffer it within cells, but a number of them also decode its message for the benefit of the target. The most important of these “calcium sensors” are the EF-hand proteins. Calcium is an ambivalent messenger. Although essential to the correct functioning of cell processes, if not carefully controlled spatially and temporally within cells, it generates variously severe cell dysfunctions, and even cell death. PMID:27462077

Calcium

MedlinePlus

... and enzymes and to send messages through the nervous system. It is important to get plenty of calcium in the foods you eat. Foods rich in calcium include Dairy products such as milk, cheese, and yogurt Leafy, green vegetables Fish with soft bones that you eat, such as ...

Porous metal for orthopedics implants

PubMed Central

Matassi, Fabrizio; Botti, Alessandra; Sirleo, Luigi; Carulli, Christian; Innocenti, Massimo

2013-01-01

Summary Porous metal has been introduced to obtain biological fixation and improve longevity of orthopedic implants. The new generation of porous metal has intriguing characteristics that allows bone healing and high osteointegration of the metallic implants. This article gives an overview about biomaterials properties of the contemporary class of highly porous metals and about the clinical use in orthopaedic surgery. PMID:24133527

Management of postprandial glucose: Recommended targets and treatment with biphasic insulin.

PubMed

Liebl, Andreas

2016-12-01

Increases in glycaemia, particularly following meals, have been independently associated with diabetes complications, most notably cardiovascular disease. Control of postprandial plasma glucose (PPG) therefore plays an important role in diabetes management. International diabetes guidelines acknowledge the value of PPG monitoring yet place relatively little emphasis on PPG control. This article considers the impact of suboptimal PPG control and current recommendations with regard to management of PPG. Specific consideration is given to the role of biphasic insulins, one of the treatment options recognised by the International Diabetes Federation as preferentially lowering PPG levels. Copyright © 2016 Primary Care Diabetes Europe. Published by Elsevier Ltd. All rights reserved.

Antibacterial action of calcium hydroxide vehicles and calcium hydroxide pastes.

PubMed

Pacios, María Gabriela; Silva, Clara; López, María Elena; Cecilia, Marta

2012-11-01

To evaluate the in vitro action of vehicles alone and with calcium hydroxide against different bacterial species. Agar plates were inoculated with the microbial suspensions, and wells were made and filled with the calcium hydroxide pastes and the vehicles used to prepare the pastes. The zones of inhibited bacterial growth were recorded, and the resulting measurements were statistically analyzed. Enterococcus faecalis was the most resistant microorganism to all medicaments. Calcium hydroxide + p-monochlorophenol; calcium hydroxide + p-monochlorophenol-propylene glycol pastes; and p-monochlorophenol, p-monochlorophenol-propylene glycol, and chlorhexidine gluconate gel alone showed the largest zones of inhibition against all the tested microorganisms. The vehicle used to prepare the calcium hydroxide paste might contribute to its antibacterial action. Chlorhexidine gluconate gel used alone, and camphorated p-monochlorophenol and camphorated p-monochlorophenol-propylene glycol as vehicles of calcium hydroxide, could be recommended, in an antimicrobial sense. © 2012 Wiley Publishing Asia Pty Ltd.

Calcium and Calcium Supplements: Achieving the Right Balance

MedlinePlus

... soy products, cereal and fruit juices, and milk substitutes To absorb calcium, your body also needs vitamin ... Nutrition/default.asp. Accessed June 25, 2015. Calcium. Natural Medicines Comprehensive Database. http://www.naturaldatabase.com. Accessed ...

Biphasic Role of Chondroitin Sulfate in Cardiac Differentiation of Embryonic Stem Cells through Inhibition of Wnt/β-Catenin Signaling

PubMed Central

Prinz, Robert D.; Willis, Catherine M.; van Kuppevelt, Toin H.; Klüppel, Michael

2014-01-01

The glycosaminoglycan chondroitin sulfate is a critical component of proteoglycans on the cell surface and in the extracellular matrix. As such, chondroitin sulfate side chains and the sulfation balance of chondroitin play important roles in the control of signaling pathways, and have a functional importance in human disease. In contrast, very little is known about the roles of chondroitin sulfate molecules and sulfation patterns during mammalian development and cell lineage specification. Here, we report a novel biphasic role of chondroitin sulfate in the specification of the cardiac cell lineage during embryonic stem cell differentiation through modulation of Wnt/beta-catenin signaling. Lineage marker analysis demonstrates that enzymatic elimination of endogenous chondroitin sulfates leads to defects specifically in cardiac differentiation. This is accompanied by a reduction in the number of beating cardiac foci. Mechanistically, we show that endogenous chondroitin sulfate controls cardiac differentiation in a temporal biphasic manner through inhibition of the Wnt/beta-catenin pathway, a known regulatory pathway for the cardiac lineage. Treatment with a specific exogenous chondroitin sulfate, CS-E, could mimic these biphasic effects on cardiac differentiation and Wnt/beta-catenin signaling. These results establish chondroitin sulfate and its sulfation balance as important regulators of cardiac cell lineage decisions through control of the Wnt/beta-catenin pathway. Our work suggests that targeting the chondroitin biosynthesis and sulfation machinery is a novel promising avenue in regenerative strategies after heart injury. PMID:24667694

Biphasic role of chondroitin sulfate in cardiac differentiation of embryonic stem cells through inhibition of Wnt/β-catenin signaling.

PubMed

Prinz, Robert D; Willis, Catherine M; van Kuppevelt, Toin H; Klüppel, Michael

2014-01-01

The glycosaminoglycan chondroitin sulfate is a critical component of proteoglycans on the cell surface and in the extracellular matrix. As such, chondroitin sulfate side chains and the sulfation balance of chondroitin play important roles in the control of signaling pathways, and have a functional importance in human disease. In contrast, very little is known about the roles of chondroitin sulfate molecules and sulfation patterns during mammalian development and cell lineage specification. Here, we report a novel biphasic role of chondroitin sulfate in the specification of the cardiac cell lineage during embryonic stem cell differentiation through modulation of Wnt/beta-catenin signaling. Lineage marker analysis demonstrates that enzymatic elimination of endogenous chondroitin sulfates leads to defects specifically in cardiac differentiation. This is accompanied by a reduction in the number of beating cardiac foci. Mechanistically, we show that endogenous chondroitin sulfate controls cardiac differentiation in a temporal biphasic manner through inhibition of the Wnt/beta-catenin pathway, a known regulatory pathway for the cardiac lineage. Treatment with a specific exogenous chondroitin sulfate, CS-E, could mimic these biphasic effects on cardiac differentiation and Wnt/beta-catenin signaling. These results establish chondroitin sulfate and its sulfation balance as important regulators of cardiac cell lineage decisions through control of the Wnt/beta-catenin pathway. Our work suggests that targeting the chondroitin biosynthesis and sulfation machinery is a novel promising avenue in regenerative strategies after heart injury.

3D printing of Mg-substituted wollastonite reinforcing diopside porous bioceramics with enhanced mechanical and biological performances.

PubMed

He, Dongshuang; Zhuang, Chen; Xu, Sanzhong; Ke, Xiurong; Yang, Xianyan; Zhang, Lei; Yang, Guojing; Chen, Xiaoyi; Mou, Xiaozhou; Liu, An; Gou, Zhongru

2016-09-01

Mechanical strength and its long-term stability of bioceramic scaffolds is still a problem to treat the osteonecrosis of the femoral head. Considering the long-term stability of diopside (DIO) ceramic but poor mechanical strength, we developed the DIO-based porous bioceramic composites via dilute magnesium substituted wollastonite reinforcing and three-dimensional (3D) printing. The experimental results showed that the secondary phase (i.e. 10% magnesium substituting calcium silicate; CSM10) could readily improve the sintering property of the bioceramic composites (DIO/CSM10- x , x  = 0-30) with increasing the CSM10 content from 0% to 30%, and the presence of the CSM10 also improved the biomimetic apatite mineralization ability in the pore struts of the scaffolds. Furthermore, the flexible strength (12.5-30 MPa) and compressive strength (14-37 MPa) of the 3D printed porous bioceramics remarkably increased with increasing CSM10 content, and the compressive strength of DIO/CSM10-30 showed a limited decay (from 37 MPa to 29 MPa) in the Tris buffer solution for a long time stage (8 weeks). These findings suggest that the new CSM10-reinforced diopside porous constructs possess excellent mechanical properties and can potentially be used to the clinic, especially for the treatment of osteonecrosis of the femoral head work as a bioceramic rod.

Biogenic Cracks in Porous Rock

NASA Astrophysics Data System (ADS)

Hemmerle, A.; Hartung, J.; Hallatschek, O.; Goehring, L.; Herminghaus, S.

2014-12-01

Microorganisms growing on and inside porous rock may fracture it by various processes. Some of the mechanisms of biofouling and bioweathering are today identified and partially understood but most emphasis is on chemical weathering, while mechanical contributions have been neglected. However, as demonstrated by the perseverance of a seed germinating and cracking up a concrete block, the turgor pressure of living organisms can be very significant. Here, we present results of a systematic study of the effects of the mechanical forces of growing microbial populations on the weathering of porous media. We designed a model porous medium made of glass beads held together by polydimethylsiloxane (PDMS), a curable polymer. The rheological properties of the porous medium, whose shape and size are tunable, can be controlled by the ratio of crosslinker to base used in the PDMS (see Fig. 1). Glass and PDMS being inert to most chemicals, we are able to focus on the mechanical processes of biodeterioration, excluding any chemical weathering. Inspired by recent measurements of the high pressure (~0.5 Mpa) exerted by a growing population of yeasts trapped in a microfluidic device, we show that yeast cells can be cultured homogeneously within porous medium until saturation of the porous space. We investigate then the effects of such an inner pressure on the mechanical properties of the sample. Using the same model system, we study also the complex interplay between biofilms and porous media. We focus in particular on the effects of pore size on the penetration of the biofilm within the porous sample, and on the resulting deformations of the matrix, opening new perspectives into the understanding of life in complex geometry. Figure 1. Left : cell culture growing in a model porous medium. The white spheres represent the grains, bonds are displayed in grey, and microbes in green. Right: microscopy picture of glass beads linked by PDMS bridges, scale bar: 100 μm.

Calcium content of different compositions of gallstones and pathogenesis of calcium carbonate gallstones.

PubMed

Yu, Ji-Kuen; Pan, Huichin; Huang, Shing-Moo; Huang, Nan-Lan; Yao, Chung-Chin; Hsiao, Kuang-Ming; Wu, Chew-Wun

2013-01-01

Our aim was to investigate the calcium content of different gallstone compositions and the pathogenic mechanisms of calcium carbonate gallstones. Between August 2001 and July 2007, gallstones from 481 patients, including 68 calcium carbonate gallstones, were analyzed for total calcium content. Gallbladder bile samples from 33 cases and six controls were analyzed for pH, carbonate anion level, free-ionized calcium concentration and saturation index for calcium carbonate. Total calcium content averaged 75.6 %, 11.8 %, and 4.2 % for calcium carbonate, calcium bilirubinate and cholesterol gallstones. In 29.4 % of patients, chronic and/or intermittent cystic duct obstructions were caused by polypoid lesions in the neck region and 70.6 % were caused by stones. A total of 82 % of patients had chronic low-grade inflammation of the gallbladder wall and 18.0 % had acute inflammatory exacerbations. In the bile, we found the mean pH, mean carbonate anion, free-ionized calcium concentrations, and mean saturation index for calcium carbonate to be elevated in comparison to controls. From our study, we found chronic and/or intermittent cystic duct obstructions and low-grade GB wall inflammation lead to GB epithelium hydrogen secretion dysfunction. Increased calcium ion efflux into the GB lumen combined with increased carbonate anion presence increases SI_CaCO(3) from 1 to 22.4. Thus, in an alkaline milieu with pH 7.8, calcium carbonate begins to aggregate and precipitate. Copyright © 2012. Published by Elsevier B.V.

Calcium source (image)

MedlinePlus

Getting enough calcium to keep bones from thinning throughout a person's life may be made more difficult if that person has ... as a tendency toward kidney stones, for avoiding calcium-rich food sources. Calcium deficiency also effects the ...

Thermally conductive porous element-based recuperators

NASA Technical Reports Server (NTRS)

Du, Jian Hua (Inventor); Chow, Louis C (Inventor); Lin, Yeong-Ren (Inventor); Wu, Wei (Inventor); Kapat, Jayanta (Inventor); Notardonato, William U. (Inventor)

2012-01-01

A heat exchanger includes at least one hot fluid flow channel comprising a first plurality of open cell porous elements having first gaps there between for flowing a hot fluid in a flow direction and at least one cold fluid flow channel comprising a second plurality of open cell porous elements having second gaps therebetween for flowing a cold fluid in a countercurrent flow direction relative to the flow direction. The thermal conductivity of the porous elements is at least 10 W/mK. A separation member is interposed between the hot and cold flow channels for isolating flow paths associated these flow channels. The first and second plurality of porous elements at least partially overlap one another to form a plurality of heat transfer pairs which transfer heat from respective ones of the first porous elements to respective ones of the second porous elements through the separation member.

Biphasic regulation of polymorphonuclear leukocyte spreading by polyphenolic compounds with pyrogallol moieties.

PubMed

Kori, Soichiro; Namiki, Hideo; Suzuki, Kingo

2009-09-01

Green tea polyphenols have been reported to have anti-inflammatory activities, although the molecular mechanisms responsible for this effect remain unclear. In the present study, we examined the effect of green tea extract and a variety of polyphenolic compounds on spreading of peripheral blood polymorphonuclear leukocytes (PMNs) over fibrinogen-coated surfaces. Green tea extract exerted a biphasic effect on PMN spreading; it induced or suppressed spreading at low and high concentrations, respectively. We also found that pyrogallol-bearing compounds have spreading induction activity. Among the compounds tested, tannic acid (TA) had the strongest activity; the concentrations required for induction of maximal spreading were 2 microM for TA, 200 microM for (-)-epigallocatechin gallate, and 2000 microM for the other active compounds. Furthermore, TA was the only compound showing a biphasic effect similar to that of green tea extract; TA at 20 or 200 microM suppressed spreading. The spreading-stimulatory signal was still latent during PMN exposure to TA at concentrations that inhibited spreading, because the pre-exposed PMNs underwent spreading when plated after removal of free TA by centrifugation. The spreading-inhibitory effect of TA at high concentrations overcame the induction of spreading by other stimuli, including phorbol 12-myristate 13-acetate, hydrogen peroxide, denatured fibrinogen surfaces, and naked plastic surfaces. These results suggest that TA as well as green tea extract is bi-functional, having pro-inflammatory and anti-inflammatory effects at low and high concentrations, respectively. Pharmacological use of TA may thus provide new strategies aimed at regulation of PMN spreading for control of inflammation.

The effect of habitat geology on calcium intake and calcium status of wild rodents.

PubMed

Shore, R F; Balment, R J; Yalden, D W

1991-12-01

Calcium is essential for normal physiological function, reproduction and growth in mammals but its distribution in the natural environment is heterogeneous. Spatial variation in calcium soil content is especially marked in the Peak District, United Kingdom, where both calcium-rich limestone and calcium-poor gritstone rock types occur. Wood mice Apodemus sylvaticus (L) and bank voles Clethrionomys glareolus (Schreber 1780) from limestone areas had significantly higher calcium concentrations in stomach contents and in faeces compared with their counterparts from gritstone areas. Calcium status was assessed from serum calcium concentration, femur weight, ash content of the body, calcium concentration in the femur and body ash. There was no significant difference in serum calcium concentration, femur calcium concentration and body ash calcium concentration between animals from the limestone and the gritstone. However, on the limestone, bank voles, but not wood mice, had significantly heavier femora and a greater proportion of ash in the body compared with their gritstone counterparts.

Porous Silicon as Antireflecting Layer

NASA Astrophysics Data System (ADS)

Kosoglu, Gulsen; Yumak, Mehmet; Okmen, Selim; Ozatay, Ozhan; Skarlatos, Yani; Garcia, Carlos

2013-03-01

The main aim in photovoltaic industry is to produce efficient and energy competitive solar cell modules at low cost. Efficient AntiReflection Coatings (ARC) improve light collection and thereby increase the current output of solar cells. Broadband ARCs are desirable for efficient application over the entire solar spectrum and porous silicon layers as antireflective coating layers provide successful light collection. In the study the most critical physical parameters of porous silicon are examined, homogeneous and uniform porous layers are produced. The photoluminescence spectrum and optical parameters of porous layers have been investigated, and we are now in the process of improving the efficiency of the device by modulating the structure of the porous silicon layers and studying its photovoltaic characteristics. We would like to thank to Mr. Aziz U. Caliskan and his group for their valuable support from TUBITAK YITAL. This Project is supported by Bogazici University Research Funding: 5782, TUBITAK Grant : 209T099, and Bogazici University Infrared Funding: 6121.

Porous and non-porous water soluble polymer nanospheres

NASA Astrophysics Data System (ADS)

Henselwood, Fred William

Water soluble polymer nanospheres have been prepared from the photo-cross-linking of diblock copolymer micelles formed either in water or in N,N-dimethylformamide/water mixtures. The diblock copolymers utilized in this study were poly(2-cinnamoyl-ethyl methacrylate)-block-poly(acrylic acid), poly ((2-cinnamoylethyl methacrylate)-random-(2-octanoylethyl methacrylate)) -block-poly(acrylic acid), and poly ((2-cinnamoyl-ethyl methacrylate)-random-(2-oleoylethyl methacrylate)) -block-poly(acrylic acid). These polymers were synthesized by the functionalization of diblock copolymers prepared by anionic polymerization. The photo-cross-linking was achieved through the dimerization of cinnamoyl groups by ultraviolet irradiation. Transmission electron microscopy confirmed that the polymer nanospheres had an inner core region formed by the cinnamoyl containing polymer blocks, and an outer shell layer formed by the acrylic acid polymer blocks. The hydrodynamic radius of the polymer nanospheres in water was approximately 50 to 75 nm as determined by dynamic light scattering. It has been found that the polymer nanospheres, when in water, could be readily impregnated with organic molecules. Fluorescence measurements showed that the polymer nanospheres could uptake polyaromatic hydrocarbons by the direct mixing of polyaromatic hydrocarbons with the polymer nanospheres in water. Perylene was found to be between 2.0 × 10sp5 and 4.0 × 10sp5 times more soluble in the core region of the polymer nanospheres than in water. The addition of divalent cations was shown to induce aggregation of the polymer nanospheres and resulted in the precipitation of the polymer nanospheres along with any captured perylene. This suggests that the polymer nanospheres may be useful in water remediation. Porous polymer nanospheres were prepared by the incorporation of low molecular weight polymeric porogens within the core region of the polymer nanospheres. Following photo-cross-linking the polymeric

Calcium fertilization increases the concentration of calcium in sapwood and calcium oxalate in foliage of red spruce

Treesearch

Kevin T. Smith; Walter C. Shortle; Jon H. Connolly; Rakesh Minocha; Jody Jellison

2009-01-01

Calcium cycling plays a key role in the health and productivity of red spruce forests in the northeastern US. A portion of the flowpath of calcium within forests includes translocation as Ca2+ in sapwood and accumulation as crystals of calcium oxalate in foliage. Concentrations of Ca in these tree tissues have been used as markers of...

Why Calcium? How Calcium Became the Best Communicator.

PubMed

Carafoli, Ernesto; Krebs, Joachim

2016-09-30

Calcium carries messages to virtually all important functions of cells. Although it was already active in unicellular organisms, its role became universally important after the transition to multicellular life. In this Minireview, we explore how calcium ended up in this privileged position. Most likely its unique coordination chemistry was a decisive factor as it makes its binding by complex molecules particularly easy even in the presence of large excesses of other cations, e.g. magnesium. Its free concentration within cells can thus be maintained at the very low levels demanded by the signaling function. A large cadre of proteins has evolved to bind or transport calcium. They all contribute to buffer it within cells, but a number of them also decode its message for the benefit of the target. The most important of these "calcium sensors" are the EF-hand proteins. Calcium is an ambivalent messenger. Although essential to the correct functioning of cell processes, if not carefully controlled spatially and temporally within cells, it generates variously severe cell dysfunctions, and even cell death. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Enhanced Raman scattering in porous silicon grating.

PubMed

Wang, Jiajia; Jia, Zhenhong; Lv, Changwu

2018-03-19

The enhancement of Raman signal on monocrystalline silicon gratings with varying groove depths and on porous silicon grating were studied for a highly sensitive surface enhanced Raman scattering (SERS) response. In the experiment conducted, porous silicon gratings were fabricated. Silver nanoparticles (Ag NPs) were then deposited on the porous silicon grating to enhance the Raman signal of the detective objects. Results show that the enhancement of Raman signal on silicon grating improved when groove depth increased. The enhanced performance of Raman signal on porous silicon grating was also further improved. The Rhodamine SERS response based on Ag NPs/ porous silicon grating substrates was enhanced relative to the SERS response on Ag NPs/ porous silicon substrates. Ag NPs / porous silicon grating SERS substrate system achieved a highly sensitive SERS response due to the coupling of various Raman enhancement factors.

A soft porous drop in linear flows

NASA Astrophysics Data System (ADS)

Young, Yuan-Nan; Miksis, Michael; Mori, Yoichiro; Shelley, Michael

2017-11-01

The cellular cytoplasm consists a viscous fluid filled with fibrous networks that also have their own dynamics. Such fluid-structure interactions have been modeled as a soft porous material immersed in a viscous fluid. In this talk we focus on the hydrodynamics of a viscous drop filled with soft porous material inside. Suspended in a Stokes flow, such a porous viscous drop is allowed to deform, both the drop interface and the porous structures inside. Special focus is on the deformation dynamics of both the porosity and the shape of the drop under simple flows such as a uniform streaming flow and linear flows. We examine the effects of flow boundary conditions at interface between the porous drop and the surrounding viscous fluid. We also examine the dynamics of a porous drop with active stress from the porous network.

Porosity change after gypsum crust formation on macro-porous limestones

NASA Astrophysics Data System (ADS)

Dewanckele, Jan; Cnudde, Veerle; de Kock, Tim; Boone, Marijn; Boone, Matthieu; van Hoorebeke, Luc; Jacobs, Patric

2010-05-01

The deterioration of stone is a complex process in which physical, biological and chemical mechanisms are involved. In this research, pore structure changes inside two types of porous limestone were analyzed before, during and after strong acid tests with SO2. Sulphatation and crust formation phenomena on natural building stones exposed to a polluted environment, are largely described in literature. As far as rocks rich in calcium carbonate are concerned, the main processes involved are the dissolution of the calcium carbonate and the formation of gypsum (CaSO4.2H2O) in presence of an acid atmosphere. The low mobility of this newly formed salt favours its accumulation in porous materials and at the surface of less porous media. The main actor in the process of gypsum crystallization on limestone is the aggressive sulphur dioxide gas (SO2). In this study, the Savonnières and Euville limestone were subjected to tests with a strong acid. According to the standard EN 13919:2002E, samples were put in acid environment for 21 days. At the bottom of the container a mixture of 500 ± 10 ml H2SO3 and 150 ± 10 ml de-mineralized H2O was added. No airborne particles or oxides of nitrogen (NOx) were added. Before exposure, after 6 days in the polluted environment and at the end of the test, the two samples were scanned with X-ray computed tomography (X-ray CT) at the Centre for X-ray Tomography at Ghent University, Belgium (UGCT; www.ugct.ugent.be). This visualization technique allows 2D and 3D reconstructions on a micrometer scale of the internal structure of an object without damaging the material. It thus enables to scan the same sample in a sequential way. In order to obtain information about the sample's interior of which the characteristics can be compared before, during and after the test, the same scanning parameters (exposure time, amount of frames, energy, etc.) were used. In addition, the same adjustments like beam hardening correction, normalizing, ring and spot

3D porous calcium-alginate scaffolds cell culture system improved human osteoblast cell clusters for cell therapy.

PubMed

Chen, Ching-Yun; Ke, Cherng-Jyh; Yen, Ko-Chung; Hsieh, Hui-Chen; Sun, Jui-Sheng; Lin, Feng-Huei

2015-01-01

Age-related orthopedic disorders and bone defects have become a critical public health issue, and cell-based therapy is potentially a novel solution for issues surrounding bone tissue engineering and regenerative medicine. Long-term cultures of primary bone cells exhibit phenotypic and functional degeneration; therefore, culturing cells or tissues suitable for clinical use remain a challenge. A platform consisting of human osteoblasts (hOBs), calcium-alginate (Ca-Alginate) scaffolds, and a self-made bioreactor system was established for autologous transplantation of human osteoblast cell clusters. The Ca-Alginate scaffold facilitated the growth and differentiation of human bone cell clusters, and the functionally-closed process bioreactor system supplied the soluble nutrients and osteogenic signals required to maintain the cell viability. This system preserved the proliferative ability of cells and cell viability and up-regulated bone-related gene expression and biological apatite crystals formation. The bone-like tissue generated could be extracted by removal of calcium ions via ethylenediaminetetraacetic acid (EDTA) chelation, and exhibited a size suitable for injection. The described strategy could be used in therapeutic application and opens new avenues for surgical interventions to correct skeletal defects.

Additively manufactured porous tantalum implants.

PubMed

Wauthle, Ruben; van der Stok, Johan; Amin Yavari, Saber; Van Humbeeck, Jan; Kruth, Jean-Pierre; Zadpoor, Amir Abbas; Weinans, Harrie; Mulier, Michiel; Schrooten, Jan

2015-03-01

The medical device industry's interest in open porous, metallic biomaterials has increased in response to additive manufacturing techniques enabling the production of complex shapes that cannot be produced with conventional techniques. Tantalum is an important metal for medical devices because of its good biocompatibility. In this study selective laser melting technology was used for the first time to manufacture highly porous pure tantalum implants with fully interconnected open pores. The architecture of the porous structure in combination with the material properties of tantalum result in mechanical properties close to those of human bone and allow for bone ingrowth. The bone regeneration performance of the porous tantalum was evaluated in vivo using an orthotopic load-bearing bone defect model in the rat femur. After 12 weeks, substantial bone ingrowth, good quality of the regenerated bone and a strong, functional implant-bone interface connection were observed. Compared to identical porous Ti-6Al-4V structures, laser-melted tantalum shows excellent osteoconductive properties, has a higher normalized fatigue strength and allows for more plastic deformation due to its high ductility. It is therefore concluded that this is a first step towards a new generation of open porous tantalum implants manufactured using selective laser melting. Copyright © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Anatase/rutile bi-phasic titanium dioxide nanoparticles for photocatalytic applications enhanced by nitrogen doping and platinum nano-islands.

PubMed

Bear, Joseph C; Gomez, Virginia; Kefallinos, Nikolaos S; McGettrick, James D; Barron, Andrew R; Dunnill, Charles W

2015-12-15

Titanium dioxide (TiO2) bi-phasic powders with individual particles containing an anatase and rutile hetero-junction have been prepared using a sequential layer sol-gel deposition technique to soluble substrates. Sequential thin films of rutile and subsequently anatase TiO2 were deposited onto sodium chloride substrates yielding extremely fragile composite layered discs that fractured into "Janus-like" like powders on substrate dissolution. Nitrogen doped and platinum sputtered analogues were also prepared, and analysed for photocatalytic potential using the photodegradation of Rhodamine B, a model organic pollutant under UV and visible light irradiation. The materials were characterised using X-ray diffraction, X-ray photoelectron spectroscopy, energy dispersive X-ray spectroscopy, Raman spectroscopy and scanning electron microscopy. This paper sheds light on the relationship between anatase and rutile materials when in direct contact and demonstrates a robust method for the synthesis of bi-phasic nanoparticles, ostensibly of any two materials, for photocatalytic reactions or otherwise. Copyright © 2015 Elsevier Inc. All rights reserved.

Association of Urinary Calcium Excretion with Serum Calcium and Vitamin D Levels

PubMed Central

Rathod, Anita; Bonny, Olivier; Guessous, Idris; Suter, Paolo M.; Conen, David; Erne, Paul; Binet, Isabelle; Gabutti, Luca; Gallino, Augusto; Muggli, Franco; Hayoz, Daniel; Péchère-Bertschi, Antoinette; Paccaud, Fred

2015-01-01

Background and objectives Population-based data on urinary calcium excretion are scarce. The association of serum calcium and circulating levels of vitamin D [25(OH)D2 or D3] with urinary calcium excretion in men and women from a population-based study was explored. Design, settings, participants, & measurements Multivariable linear regression was used to explore factors associated with square root–transformed 24-hour urinary calcium excretion (milligrams per 24 hours) taken as the dependent variable with a focus on month-specific vitamin D tertiles and serum calcium in the Swiss Survey on Salt Study. Results In total, 624 men and 669 women were studied with mean ages of 49.2 and 47.0 years, respectively (age range=15–95 years). Mean urinary calcium excretion was higher in men than in women (183.05 versus 144.60 mg/24 h; P<0.001). In adjusted models, the association (95% confidence interval) of square root urinary calcium excretion with protein–corrected serum calcium was 1.78 (95% confidence interval, 1.21 to 2.34) mg/24 h per milligram per deciliter in women and 0.59 (95% confidence interval, −0.11 to 1.29) mg/24 h per milligram per deciliter in men. Men in the third 25(OH)D3 tertile had higher square root urinary calcium excretion than men in the first tertile (0.99; 95% confidence interval, 0.36 to 1.63 mg/24 h per nanogram per milliliter), and the corresponding association was 0.32 (95% confidence interval, −0.22 to 0.85) mg/24 h per nanogram per milliliter in women. These sex differences were more marked under conditions of high urinary sodium or urea excretions. Conclusions There was a positive association of serum calcium with urinary calcium excretion in women but not men. Vitamin 25(OH)D3 was associated with urinary calcium excretion in men but not women. These results suggest important sex differences in the hormonal and dietary control of urinary calcium excretion. PMID:25518946

Association of urinary calcium excretion with serum calcium and vitamin D levels.

PubMed

Rathod, Anita; Bonny, Olivier; Guessous, Idris; Suter, Paolo M; Conen, David; Erne, Paul; Binet, Isabelle; Gabutti, Luca; Gallino, Augusto; Muggli, Franco; Hayoz, Daniel; Péchère-Bertschi, Antoinette; Paccaud, Fred; Burnier, Michel; Bochud, Murielle

2015-03-06

Population-based data on urinary calcium excretion are scarce. The association of serum calcium and circulating levels of vitamin D [25(OH)D2 or D3] with urinary calcium excretion in men and women from a population-based study was explored. Multivariable linear regression was used to explore factors associated with square root-transformed 24-hour urinary calcium excretion (milligrams per 24 hours) taken as the dependent variable with a focus on month-specific vitamin D tertiles and serum calcium in the Swiss Survey on Salt Study. In total, 624 men and 669 women were studied with mean ages of 49.2 and 47.0 years, respectively (age range=15-95 years). Mean urinary calcium excretion was higher in men than in women (183.05 versus 144.60 mg/24 h; P<0.001). In adjusted models, the association (95% confidence interval) of square root urinary calcium excretion with protein-corrected serum calcium was 1.78 (95% confidence interval, 1.21 to 2.34) mg/24 h per milligram per deciliter in women and 0.59 (95% confidence interval, -0.11 to 1.29) mg/24 h per milligram per deciliter in men. Men in the third 25(OH)D3 tertile had higher square root urinary calcium excretion than men in the first tertile (0.99; 95% confidence interval, 0.36 to 1.63 mg/24 h per nanogram per milliliter), and the corresponding association was 0.32 (95% confidence interval, -0.22 to 0.85) mg/24 h per nanogram per milliliter in women. These sex differences were more marked under conditions of high urinary sodium or urea excretions. There was a positive association of serum calcium with urinary calcium excretion in women but not men. Vitamin 25(OH)D3 was associated with urinary calcium excretion in men but not women. These results suggest important sex differences in the hormonal and dietary control of urinary calcium excretion. Copyright © 2015 by the American Society of Nephrology.

Process of preparing tritiated porous silicon

DOEpatents

Tam, Shiu-Wing

1997-01-01

A process of preparing tritiated porous silicon in which porous silicon is equilibrated with a gaseous vapor containing HT/T.sub.2 gas in a diluent for a time sufficient for tritium in the gas phase to replace hydrogen present in the pore surfaces of the porous silicon.

From Red Cells to Soft Porous Lubrication

NASA Astrophysics Data System (ADS)

Gacka, T.; Nathan, R.; Wu, L.; Wu, Q.; Cbmss Laboratory Team; Chinese Academy Of Sci. Team

2011-11-01

Feng and Weinbaum (J. Fluid. Mech., 422, 282, 2000), inspired by the enhanced lift phenomena in downhill skiing, developed a new lubrication theory for highly compressible porous media where significantly increased lifting force was predicted as a planing surface glided over a soft porous layer; suggesting superior potential use of porous media for soft lubrication. In this study, we experimentally examine the lift generation phenomena by developing a novel soft porous bearing that consists of a running conveyer belt covered with a soft, 100% polyester, porous sheet, and a stationary, fully instrumented, inclined, planar, upper board. Pore pressure was generated as the upper boundary glides over the soft porous bearing and was measured by pressure sensors. One observed that the pore pressure distribution is consistent with predictions by Feng and Weinbaum (2000), and is a function of the relative velocity between the planing surface and the running belt, the mechanical properties (e.g. porosity, permeability and stiffness) and thickness of the porous layer, as well as the compression ratios at the leading and trailing edges. A load cell is used to characterize the performance of the porous bearing, by comparing pore pressure to total lifting forces. The study presented herein significantly improves our understanding of the behavior of highly compressible porous media under fast compression.

Calcium and Mitosis

NASA Technical Reports Server (NTRS)

Hepler, P.

1983-01-01

Although the mechanism of calcium regulation is not understood, there is evidence that calcium plays a role in mitosis. Experiments conducted show that: (1) the spindle apparatus contains a highly developed membrane system that has many characteristics of sarcoplasmic reticulum of muscle; (2) this membrane system contains calcium; and (3) there are ionic fluxes occurring during mitosis which can be seen by a variety of fluorescence probes. Whether the process of mitosis can be modulated by experimentally modulating calcium is discussed.

Calcium ion binding properties of Medicago truncatula calcium/calmodulin-dependent protein kinase.

PubMed

Swainsbury, David J K; Zhou, Liang; Oldroyd, Giles E D; Bornemann, Stephen

2012-09-04

A calcium/calmodulin-dependent protein kinase (CCaMK) is essential in the interpretation of calcium oscillations in plant root cells for the establishment of symbiotic relationships with rhizobia and mycorrhizal fungi. Some of its properties have been studied in detail, but its calcium ion binding properties and subsequent conformational change have not. A biophysical approach was taken with constructs comprising either the visinin-like domain of Medicago truncatula CCaMK, which contains EF-hand motifs, or this domain together with the autoinhibitory domain. The visinin-like domain binds three calcium ions, leading to a conformational change involving the exposure of hydrophobic surfaces and a change in tertiary but not net secondary or quaternary structure. The affinity for calcium ions of visinin-like domain EF-hands 1 and 2 (K(d) = 200 ± 50 nM) was appropriate for the interpretation of calcium oscillations (~125-850 nM), while that of EF-hand 3 (K(d) ≤ 20 nM) implied occupancy at basal calcium ion levels. Calcium dissociation rate constants were determined for the visinin-like domain of CCaMK, M. truncatula calmodulin 1, and the complex between these two proteins (the slowest of which was 0.123 ± 0.002 s(-1)), suggesting the corresponding calcium association rate constants were at or near the diffusion-limited rate. In addition, the dissociation of calmodulin from the protein complex was shown to be on the same time scale as the dissociation of calcium ions. These observations suggest that the formation and dissociation of the complex between calmodulin and CCaMK would substantially mirror calcium oscillations, which typically have a 90 s periodicity.

Calcium-dependent inactivation of calcium channels in cochlear hair cells of the chicken.

PubMed

Lee, Seunghwan; Briklin, Olga; Hiel, Hakim; Fuchs, Paul

2007-09-15

Voltage-gated calcium channels support both spontaneous and sound-evoked neurotransmitter release from ribbon synapses of cochlear hair cells. A variety of regulatory mechanisms must cooperate to ensure the appropriate level of activity in the restricted pool of synaptic calcium channels ( approximately 100) available to each synaptic ribbon. One potential feedback mechanism, calcium-dependent inactivation (CDI) of voltage-gated, L-type calcium channels, can be modulated by calmodulin-like calcium-binding proteins. CDI of voltage-gated calcium current was studied in hair cells of the chicken's basilar papilla (analogous to the mammalian cochlea) after blocking the predominant potassium conductances. For inactivating currents produced by 2.5 s steps to the peak of the current-voltage relation (1 mm EGTA internal calcium buffer), single exponential fits yielded an average decay time constant of 1.92 +/- 0.18 s (mean +/- s.e.m., n = 12) at 20-22 degrees C, while recovery occurred with a half-time of approximately 10 s. Inactivation produced no change in reversal potential, arguing that the observed relaxation did not result from alternative processes such as calcium accumulation or activation of residual potassium currents. Substitution of external calcium with barium greatly reduced inactivation, while inhibition of endoplasmic calcium pumps with t-benzohydroquinone (BHQ) or thapsigargin made inactivation occur faster and to a greater extent. Raising external calcium 10-fold (from 2 to 20 mm) increased peak current 3-fold, but did not alter the extent or time course of CDI. However, increasing levels of internal calcium buffer consistently reduced the rate and extent of inactivation. With 1 mm EGTA buffering and in 2 mm external calcium, the available pool of calcium channels was half-inactivated near the resting membrane potential (-50 mV). CDI may be further regulated by calmodulin-like calcium-binding proteins (CaBPs). mRNAs for several CaBPs are expressed in

An overview of techniques for the measurement of calcium distribution, calcium fluxes, and cytosolic free calcium in mammalian cells.

PubMed Central

Borle, A B

1990-01-01

An array of techniques can be used to study cell calcium metabolism that comprises several calcium compartments and many types of transport systems such as ion channels, ATP-dependent pumps, and antiporters. The measurement of total cell calcium brings little information of value since 60 to 80% of total cell calcium is actually bound to the extracellular glycocalyx. Cell fractionation and differential centrifugation have been used to study intracellular Ca2+ compartmentalization, but the methods suffer from the possibility of Ca2+ loss or redistribution among cell fractions. Steady-state kinetic analyses of 45Ca uptake or desaturation curves have been used to study the distribution of Ca2+ among various kinetic pools in living cells and their rate of Ca2+ exchange, but the analyses are constrained by many limitations. Nonsteady-state tracer studies can provide information about rapid changes in calcium influx or efflux in and out of the cell. Zero-time kinetics of 45Ca uptake can detect instantaneous changes in calcium influx, while 45Ca fractional efflux ratio, can detect rapid stimulations or inhibitions of calcium efflux out of cells. Permeabilized cells have been successfully used to gauge the relative role of intracellular organelles in controlling [Ca2+]i. The measurement of the cytosolic ionized calcium ([Ca2+]i) is undoubtedly the most important and, physiologically, the most relevant method available. The choice of the appropriate calcium indicator, fluorescent, bioluminescent, metallochromic, or Ca2(+)-sensitive microelectrodes depends on the cell type and the magnitude and time constant of the event under study. Each probe has specific assets and drawbacks. The study of plasma membrane vesicles derived from baso-lateral or apical plasmalemma can also bring important information on the (Ca2(+)-Mg2+) ATPase-dependent calcium pump and on the kinetics and stoichiometry of the Na(+)-Ca2+ antiporter. The best strategy to study cell calcium metabolism is to

Calcium mobilizations in response to changes in the gravity vector in Arabidopsis seedlings: possible cellular mechanisms.

PubMed

Tatsumi, Hitoshi; Toyota, Masatsugu; Furuichi, Takuya; Sokabe, Masahiro

2014-01-01

Gravity influences the growth direction of higher plants. Changes in the gravity vector (gravistimulation) immediately promote the increase in the cytoplasmic free calcium ion concentration ([Ca(2+)]c) in Arabidopsis (Arabidopsis thaliana) seedlings. When the seedlings are gravistimulated by reorientation at 180°, a transient two peaked (biphasic) [Ca(2+)]c-increase arises in their hypocotyl and petioles. Parabolic flights (PFs) can generate a variety of gravity-stimuli, and enables us to measure gravity-induced [Ca(2+)]c-increases without specimen rotation, which demonstrate that Arabidopsis seedlings possess a rapid gravity-sensing mechanism linearly transducing a wide range of gravitational changes into Ca(2+) signals on a sub-second timescale. Hypergravity by centrifugation (20 g or 300 g) also induces similar transient [Ca(2+)]c-increases. In this review, we propose models for possible cellular processes of the garavi-stimulus-induced [Ca(2+)]c-increase, and evaluate those by examining whether the model fits well with the kinetic parameters derived from the [Ca(2+)]c-increases obtained by applying gravistimulus with different amplitudes and time sequences.

Na+/Ca2+ exchange and regulation of cytoplasmic concentration of calcium in rat cerebellar neurons treated with glutamate.

PubMed

Storozhevykh, T P; Sorokina, E G; Vabnitz, A V; Senilova, Ya E; Tukhbatova, G R; Pinelis, V G

2007-07-01

In the present work, the forward and/or reversed Na+/Ca2+ exchange in cerebellar granular cells was suppressed by substitution of Na+o by Li+ before, during, and after exposure to glutamate for varied time and also using the inhibitor KB-R7943 of the reversed exchange. After glutamate challenge for 1 min, Na+o/Li+ substitution did not influence the recovery of low [Ca2+]i in a calcium-free medium. A 1-h incubation with 100 microM glutamate induced in the neurons a biphasic and irreversible [Ca2+]i rise (delayed calcium deregulation (DCD)), enhancement of [Na+]i, and decrease in the mitochondrial potential. If Na+o had been substituted by Li+ before the application of glutamate, i.e. the exchange reversal was suppressed during the exposure to glutamate, the number of cells with DCD was nearly fourfold lowered. However, addition of the Na+/K+-ATPase inhibitor ouabain (0.5 mM) not preventing the exchange reversal also decreased DCD in the presence of glutamate. Both exposures decreased the glutamate-caused loss of intracellular ATP. Glucose deprivation partially abolished protective effects of the Na+o/Li+ substitution and ouabain. KB-R7943 (10 microM) increased 7.4-fold the number of cells with the [Ca2+]i decreased to the basal level after the exposure to glutamate. Thus, reversal of the Na+/Ca2+ exchange reinforced the glutamate-caused perturbations of calcium homeostasis in the neurons and slowed the recovery of the decreased [Ca2+]i in the post-glutamate period. However, for development of DCD, in addition to the exchange reversal, other factors are required, in particular a decrease in the intracellular concentration of ATP.

Calcium Blood Test

MedlinePlus

... Your health care provider may order a calcium test if you have a pre-existing condition that may affect your calcium levels. These include: Kidney disease Thyroid disease Malnutrition Certain types of cancer What happens during a calcium blood test? A health care professional will take a blood ...

Ultrasonic Nondestructive Characterization of Porous Materials

NASA Astrophysics Data System (ADS)

Yang, Ningli

2011-12-01

Wave propagation in porous media is studied in a wide range of technological applications. In the manufacturing industry, determining porosity of materials in the manufacturing process is required for strict quality control. In the oil industry, acoustic signals and seismic surveys are used broadly to determine the physical properties of the reservoir rock which is a porous media filled with oil or gas. In porous noise control materials, a precise prediction of sound absorption with frequency and evaluation of tortuosity are necessary. Ultrasonic nondestructive methods are a very important tool for characterization of porous materials. The dissertation deals with two types of porous media: materials with relatively low and closed porosity and materials with comparatively high and open porosity. Numerical modeling, Finite Element simulations and experimental characterization are all discussed in this dissertation. First, ultrasonic scattering is used to determine the porosity in porous media with closed pores. In order get a relationship between the porosity in porous materials and ultrasonic scattering independently and to increase the sensitivity to obtain scattering information, ultrasonic imaging methods are applied and acoustic waves are focused by an acoustic lens. To verify the technique, engineered porous acrylic plates with varying porosity are measured by ultrasonic scanning and ultrasonic array sensors. Secondly, a laser based ultrasonic technique is explored for predicting the mechanical integrity and durability of cementitious materials. The technique used involves the measurement of the phase velocity of fast and slow longitudinal waves in water saturated cement paste. The slow wave velocity is related to the specimen's tortuosity. The fast wave speed is dependent on the elastic properties of porous solid. Experimental results detailing the generation and detection of fast and slow wave waves in freshly prepared and aged water-saturated cement samples

Composite porous scaffold of PEG/PLA support improved bone matrix deposition in vitro compared to PLA-only scaffolds.

PubMed

Bhaskar, Birru; Owen, Robert; Bahmaee, Hossein; Wally, Zena; Sreenivasa Rao, Parcha; Reilly, Gwendolen C

2018-05-01

Controllable pore size and architecture are essential properties for tissue-engineering scaffolds to support cell ingrowth colonization. To investigate the effect of polyethylene glycol (PEG) addition on porosity and bone-cell behavior, porous polylactic acid (PLA)-PEG scaffolds were developed with varied weight ratios of PLA-PEG (100/0, 90/10, 75/25) using solvent casting and porogen leaching. Sugar 200-300 µm in size was used as a porogen. To assess scaffold suitability for bone tissue engineering, MLO-A5 murine osteoblast cells were cultured and cell metabolic activity, alkaline phosphatase (ALP) activity and bone-matrix production determined using (alizarin red S staining for calcium and direct red 80 staining for collagen). It was found that metabolic activity was significantly higher over time on scaffolds containing PEG, ALP activity and mineralized matrix production were also significantly higher on scaffolds containing 25% PEG. Porous architecture and cell distribution and penetration into the scaffold were analyzed using SEM and confocal microscopy, revealing that inclusion of PEG increased pore interconnectivity and therefore cell ingrowth in comparison to pure PLA scaffolds. The results of this study confirmed that PLA-PEG porous scaffolds support mineralizing osteoblasts better than pure PLA scaffolds, indicating they have a high potential for use in bone tissue engineering applications. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1334-1340, 2018. © 2018 Wiley Periodicals, Inc.

Porous substrates filled with nanomaterials

DOEpatents

Worsley, Marcus A.; Baumann, Theodore F.; Satcher, Jr., Joe H.; Stadermann, Michael

2018-04-03

A composition comprising: at least one porous carbon monolith, such as a carbon aerogel, comprising internal pores, and at least one nanomaterial, such as carbon nanotubes, disposed uniformly throughout the internal pores. The nanomaterial can be disposed in the middle of the monolith. In addition, a method for making a monolithic solid with both high surface area and good bulk electrical conductivity is provided. A porous substrate having a thickness of 100 microns or more and comprising macropores throughout its thickness is prepared. At least one catalyst is deposited inside the porous substrate. Subsequently, chemical vapor deposition is used to uniformly deposit a nanomaterial in the macropores throughout the thickness of the porous substrate. Applications include electrical energy storage, such as batteries and capacitors, and hydrogen storage.

Porous substrates filled with nanomaterials

DOEpatents

Worsley, Marcus A.; Baumann, Theodore F.; Satcher, Jr., Joe H.; Stadermann, Michael

2014-08-19

A composition comprising: at least one porous carbon monolith, such as a carbon aerogel, comprising internal pores, and at least one nanomaterial, such as carbon nanotubes, disposed uniformly throughout the internal pores. The nanomaterial can be disposed in the middle of the monolith. In addition, a method for making a monolithic solid with both high surface area and good bulk electrical conductivity is provided. A porous substrate having a thickness of 100 microns or more and comprising macropores throughout its thickness is prepared. At least one catalyst is deposited inside the porous substrate. Subsequently, chemical vapor deposition is used to uniformly deposit a nanomaterial in the macropores throughout the thickness of the porous substrate. Applications include electrical energy storage, such as batteries and capacitors, and hydrogen storage.

Catalytic conversion of corncob and corncob pretreatment hydrolysate to furfural in a biphasic system with addition of sodium chloride.

PubMed

Qing, Qing; Guo, Qi; Zhou, Linlin; Wan, Yilun; Xu, Youqing; Ji, Huilong; Gao, Xiaohang; Zhang, Yue

2017-02-01

Catalytic conversion of corncob pretreatment hydrolysate and raw corncob into furfural in a modified biphasic system by SO 4 2- /SnO 2 - MMT solid catalyst has been developed. The influence of the organic solvent type, organic to water phase ratio, sodium chloride concentration, reaction temperature and time on the furfural production were comparatively evaluated. The results showed that furfural yields of 81.7% and 66.1% were achieved at 190°C for 15mins and 190°C for 20mins, respectively, for corncob pretreatment hydrolysate and raw corncob by this solid catalyst. The solid catalyst used in this study exhibited good stability and high efficiency applied in the modified biphasic system in addition to excellent recyclability. The proposed catalytic system displayed high performance for catalytic conversion of lignocellulosic biomass into important platform chemicals and has great potential in industrial application. Copyright © 2016 Elsevier Ltd. All rights reserved.

Fabricating porous silicon carbide

NASA Technical Reports Server (NTRS)

Shor, Joseph S. (Inventor); Kurtz, Anthony D. (Inventor)

1994-01-01

The formation of porous SiC occurs under electrochemical anodization. A sample of SiC is contacted electrically with nickel and placed into an electrochemical cell which cell includes a counter electrode and a reference electrode. The sample is encapsulated so that only a bare semiconductor surface is exposed. The electrochemical cell is filled with an HF electrolyte which dissolves the SiC electrochemically. A potential is applied to the semiconductor and UV light illuminates the surface of the semiconductor. By controlling the light intensity, the potential and the doping level, a porous layer is formed in the semiconductor and thus one produces porous SiC.

Effect of anions or foods on absolute bioavailability of calcium from calcium salts in mice by pharmacokinetics.

PubMed

Ueda, Yukari; Taira, Zenei

2013-01-01

We studied the absolute bioavailability of calcium from calcium L-lactate in mice using pharmacokinetics, and reviewed the absolute bioavailability of calcium from three other calcium salts in mice previously studied: calcium chloride, calcium acetate, and calcium ascorbate. The results showed that calcium metabolism is linear between intravenous administration of 15 mg/kg and 30 mg/kg, and is not affected by anions. Results after oral calcium administration of 150 mg/kg showed that the intestinal absorption process was significantly different among the four calcium salts. The rank of absolute bioavailability of calcium was calcium ascorbate > calcium L-lactate ≥ calcium acetate > calcium chloride. The mean residence time (MRTab) of calcium from calcium ascorbate (32.2 minutes) in the intestinal tract was much longer than that from calcium L-lactate (9.5 minutes), calcium acetate (15.0 minutes) and calcium chloride (13.6 minutes). Furthermore, the foods di-D-fructo-furanose-1,2':2,3'-dianhydride, sudachi (Citrus sudachi) juice, and moromi-su (a Japanese vinegar) increased the absolute bioavailability of calcium from calcium chloride by 2.46-fold, 2.86-fold, and 1.23-fold, respectively, and prolonged MRTab by 48.5 minutes, 43.1 minutes, and 44.9 minutes, respectively. In conclusion, the prolonged MRTab of calcium in the intestinal tract by anion or food might cause the increased absorbability of calcium.

Effect of anions or foods on absolute bioavailability of calcium from calcium salts in mice by pharmacokinetics

PubMed Central

Ueda, Yukari; Taira, Zenei

2013-01-01

We studied the absolute bioavailability of calcium from calcium L-lactate in mice using pharmacokinetics, and reviewed the absolute bioavailability of calcium from three other calcium salts in mice previously studied: calcium chloride, calcium acetate, and calcium ascorbate. The results showed that calcium metabolism is linear between intravenous administration of 15 mg/kg and 30 mg/kg, and is not affected by anions. Results after oral calcium administration of 150 mg/kg showed that the intestinal absorption process was significantly different among the four calcium salts. The rank of absolute bioavailability of calcium was calcium ascorbate > calcium L-lactate ≥ calcium acetate > calcium chloride. The mean residence time (MRTab) of calcium from calcium ascorbate (32.2 minutes) in the intestinal tract was much longer than that from calcium L-lactate (9.5 minutes), calcium acetate (15.0 minutes) and calcium chloride (13.6 minutes). Furthermore, the foods di-D-fructo-furanose-1,2′:2,3′-dianhydride, sudachi (Citrus sudachi) juice, and moromi-su (a Japanese vinegar) increased the absolute bioavailability of calcium from calcium chloride by 2.46-fold, 2.86-fold, and 1.23-fold, respectively, and prolonged MRTab by 48.5 minutes, 43.1 minutes, and 44.9 minutes, respectively. In conclusion, the prolonged MRTab of calcium in the intestinal tract by anion or food might cause the increased absorbability of calcium. PMID:27186137

Process of preparing tritiated porous silicon

DOEpatents

Tam, S.W.

1997-02-18

A process of preparing tritiated porous silicon is described in which porous silicon is equilibrated with a gaseous vapor containing HT/T{sub 2} gas in a diluent for a time sufficient for tritium in the gas phase to replace hydrogen present in the pore surfaces of the porous silicon. 1 fig.

Trophic Ecology of Benthic Marine Invertebrates with Bi-Phasic Life Cycles: What Are We Still Missing?

PubMed

Calado, Ricardo; Leal, Miguel Costa

2015-01-01

The study of trophic ecology of benthic marine invertebrates with bi-phasic life cycles is critical to understand the mechanisms shaping population dynamics. Moreover, global climate change is impacting the marine environment at an unprecedented level, which promotes trophic mismatches that affect the phenology of these species and, ultimately, act as drivers of ecological and evolutionary change. Assessing the trophic ecology of marine invertebrates is critical to understanding maternal investment, larval survival to metamorphosis, post-metamorphic performance, resource partitioning and trophic cascades. Tools already available to assess the trophic ecology of marine invertebrates, including visual observation, gut content analysis, food concentration, trophic markers, stable isotopes and molecular genetics, are reviewed and their main advantages and disadvantages for qualitative and quantitative approaches are discussed. The challenges to perform the partitioning of ingestion, digestion and assimilation are discussed together with different approaches to address each of these processes for short- and long-term fingerprinting. Future directions for research on the trophic ecology of benthic marine invertebrates with bi-phasic life cycles are discussed with emphasis on five guidelines that will allow for systematic study and comparative meta-analysis to address important unresolved questions. © 2015 Elsevier Ltd. All rights reserved.

Open wedge high tibial osteotomies: Calcium-phosphate ceramic spacer versus autologous bonegraft.

PubMed

Gouin, F; Yaouanc, F; Waast, D; Melchior, B; Delecrin, J; Passuti, N

2010-10-01

Valgus tibial osteotomy (VTO) is a well-known procedure for the treatment of medial compartment femoro-tibial osteoarthritis. Good and very good results have been reported with calcium phosphate wedges, which avoid the inconveniences of autologous grafts use. The hypothesis of this study is that with equivalent results in the treatment of osteoarthritis of the knee, the use of calcium phosphate wedges (BMCaPh) to fill the bone defect created by osteotomy would result in fewer specific complications and less pain associated with autologous grafts (AUTO) harvesting. This prospective, controlled, randomised study included one arm that received a macroporous, biphasic calcium phosphate wedge (BMCaPh group) and one arm that received an autologous tricortical graft (AUTO group) for filling. The same plate with locked screws was used for fixation in all cases. All patients underwent at least two years of clinical and radiographic post-operative follow-up. Forty patients were included. Loss of correction occurred in six of the twenty-two patients in the BMCaPh group (27%), resulting in three early surgical revisions, compared to one loss of correction in the AUTO group. Lateral cortical hinge tears were a risk factor for loss of correction for the entire cohort and in the BMCaPh group. (relative risk 13.3 [1.9-92]. Moreover, union took significantly longer and pain lasted significantly longer in the BMCaPh group, although results were comparable at 6 months. A significant number of undesirable events (loss of correction) occurred in this study, limiting the number of included patients. Nevertheless, the results show that although there was no difference in the two groups for overall complications, number of revisions all causes combined, or clinical results, filling with BMCaPh was less tolerated and increased the risk of loss of correction when local mechanical conditions of the knee were unfavourable (lateral cortical hinge tears). Moreover, although it is not possible

Calcium - ionized

MedlinePlus

... diuretics Thrombocytosis (high platelet count) Tumors Vitamin A excess Vitamin D excess Lower-than-normal levels may be due to: Hypoparathyroidism Malabsorption Osteomalacia Pancreatitis Renal failure Rickets Vitamin D deficiency Alternative Names Free calcium; Ionized calcium ...

Intracellular Calcium Mobilization in Response to Ion Channel Regulators via a Calcium-Induced Calcium Release Mechanism

PubMed Central

Petrou, Terry; Olsen, Hervør L.; Thrasivoulou, Christopher; Masters, John R.; Ashmore, Jonathan F.

2017-01-01

Free intracellular calcium ([Ca2+]i), in addition to being an important second messenger, is a key regulator of many cellular processes including cell membrane potential, proliferation, and apoptosis. In many cases, the mobilization of [Ca2+]i is controlled by intracellular store activation and calcium influx. We have investigated the effect of several ion channel modulators, which have been used to treat a range of human diseases, on [Ca2+]i release, by ratiometric calcium imaging. We show that six such modulators [amiodarone (Ami), dofetilide, furosemide (Fur), minoxidil (Min), loxapine (Lox), and Nicorandil] initiate release of [Ca2+]i in prostate and breast cancer cell lines, PC3 and MCF7, respectively. Whole-cell currents in PC3 cells were inhibited by the compounds tested in patch-clamp experiments in a concentration-dependent manner. In all cases [Ca2+]i was increased by modulator concentrations comparable to those used clinically. The increase in [Ca2+]i in response to Ami, Fur, Lox, and Min was reduced significantly (P < 0.01) when the external calcium was reduced to nM concentration by chelation with EGTA. The data suggest that many ion channel regulators mobilize [Ca2+]i. We suggest a mechanism whereby calcium-induced calcium release is implicated; such a mechanism may be important for understanding the action of these compounds. PMID:27980039

A comparative study of calcium absorption following a single serving administration of calcium carbonate powder versus calcium citrate tablets in healthy premenopausal women

PubMed Central

Wang, Haiyuan; Bua, Peter; Capodice, Jillian

2014-01-01

Background Calcium is an essential mineral often taken as a daily, long-term nutritional supplement. Data suggests that once-daily dosing is important with regard to long-term compliance of both drugs and nutritional supplements. Objective This study was undertaken to compare the bioavailability of a single serving of two calcium supplements in healthy, premenopausal women. Design A two-period, crossover bioavailability study of a single serving of calcium citrate tablets (two tablets=500 mg calcium) versus a single serving of calcium carbonate powder (one packet of powder=1,000 mg calcium) was performed in healthy women aged between 25 and 45. All subjects were on a calcium-restricted diet 7 days prior to testing and fasted for 12 h before being evaluated at 0, 1, 2, and 4 h after oral administration of the test agents. Blood measurements for total and ionized calcium and parathyroid hormone were performed and adverse events were monitored. Results Twenty-three women were evaluable with a mean age of 33.2±8.71. Results showed that administration of a single serving of a calcium carbonate powder resulted in greater absorption in total and ionized calcium versus a single serving of calcium citrate tablets at 4 h (4.25±0.21 vs. 4.16±0.16, p=0.001). There were minimal side effects and no reported serious adverse events. Conclusions This study shows that a single serving of a calcium carbonate powder is more bioavailable than a single serving of calcium citrate tablets. This may be beneficial for long-term compliance. PMID:24772062

Measuring calcium dynamics in living cells with Genetically Encodable Calcium Indicators

PubMed Central

McCombs, Janet E.

2008-01-01

Genetically encoded calcium indicators (GECIs) allow researchers to measure calcium dynamics in specific targeted locations within living cells. Such indicators enable dissection of the spatial and temporal control of calcium signaling processes. Here we review recent progress in the development of GECIs, highlighting which indicators are most appropriate for measuring calcium in specific organelles and localized domains in mammalian tissue culture cells. An overview of recent approaches that have been undertaken to ensure that the GECIs are minimally perturbed by the cellular environment is provided. Additionally, the procedures for introducing GECIs into mammalian cells, conducting calcium imaging experiments, and analyzing data are discussed. Because organelle-targeted indicators often pose an additional challenge, we underscore strategies for calibrating GECIs in these locations. PMID:18848629

INVESTIGATION OF AQUEOUS BIPHASIC SYSTEMS FOR THE SEPARATIONS OF LIGNINS FROM CELLULOSE IN THE PAPER PULPING PROCESS. (R826732)

EPA Science Inventory

In efforts to apply a polymer-based aqueous biphasic system (ABS) extraction to the paper pulping process, the study of the distribution of various lignin and cellulosic fractions in ABS and the effects of temperature on system composition and solute partitioning have been inv...

Porous Molecular Solids and Liquids

PubMed Central

2017-01-01

Until recently, porous molecular solids were isolated curiosities with properties that were eclipsed by porous frameworks, such as metal–organic frameworks. Now molecules have emerged as a functional materials platform that can have high levels of porosity, good chemical stability, and, uniquely, solution processability. The lack of intermolecular bonding in these materials has also led to new, counterintuitive states of matter, such as porous liquids. Our ability to design these materials has improved significantly due to advances in computational prediction methods. PMID:28691065