Note: This page contains sample records for the topic calcium phosphates from
While these samples are representative of the content of,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of
to obtain the most current and comprehensive results.
Last update: November 12, 2013.

Calcium Phosphate  

Microsoft Academic Search

Early childhood dental caries is defined by its complex etiology of intersecting causations. Diet in combination with good\\u000a oral hygiene, is the most prominently alterable component of this etiology.\\u000a \\u000a Providing enough calcium phosphate in the diet of the pregnant and nursing mother and eventually in the weaning infant ensures\\u000a that a prominent component (calcium phosphate deficiency) of the complex diagram

Rainy Dawn Warf; Ronald Ross Watson


Osteoinduction by calcium phosphate biomaterials  

Microsoft Academic Search

Different materials were implanted in muscles of dogs to study the osteoinduction of calcium phosphate biomaterials. Bone formation was only seen in calcium phosphate biomaterials with micropores, and could be found in hydroxyapatite (HA) ceramic, tricalcium phosphate\\/hydroxyapatite ceramic (BCP), ß-TCP ceramic and calcium phosphate cement. The osteoinductive potential was different in different materials. The results indicate that osteoinduction can be

Huipin Yuan; Zongjian Yang; Yubao Li; Xingdong Zhang; J. D. De Bruijn; K. De Groot



21 CFR 182.8217 - Calcium phosphate.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 2013-04-01 false Calcium phosphate. 182.8217 Section 182.8217 Food...RECOGNIZED AS SAFE Nutrients § 182.8217 Calcium phosphate. (a) Product. Calcium phosphate (mono-, di-, and tribasic)....



21 CFR 182.1217 - Calcium phosphate.  

Code of Federal Regulations, 2010 CFR

...2009-04-01 2009-04-01 false Calcium phosphate. 182.1217 Section 182.1217 Food...Purpose GRAS Food Substances § 182.1217 Calcium phosphate. (a) Product. Calcium phosphate (mono-, di-, and tribasic)....



21 CFR 182.1217 - Calcium phosphate.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 2013-04-01 false Calcium phosphate. 182.1217 Section 182.1217 Food...Purpose GRAS Food Substances § 182.1217 Calcium phosphate. (a) Product. Calcium phosphate (mono-, di-, and tribasic)....



21 CFR 182.8217 - Calcium phosphate.  

Code of Federal Regulations, 2010 CFR

...2009-04-01 2009-04-01 false Calcium phosphate. 182.8217 Section 182.8217 Food...RECOGNIZED AS SAFE Nutrients § 182.8217 Calcium phosphate. (a) Product. Calcium phosphate (mono-, di-, and tribasic)....



21 CFR 182.8217 - Calcium phosphate.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2009-04-01 true Calcium phosphate. 182.8217 Section 182.8217 Food...RECOGNIZED AS SAFE Nutrients § 182.8217 Calcium phosphate. (a) Product. Calcium phosphate (mono-, di-, and tribasic)....



21 CFR 182.1217 - Calcium phosphate.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2009-04-01 true Calcium phosphate. 182.1217 Section 182.1217 Food...Purpose GRAS Food Substances § 182.1217 Calcium phosphate. (a) Product. Calcium phosphate (mono-, di-, and tribasic)....



Complexes in Calcium Phosphate Solutions.  

National Technical Information Service (NTIS)

Potentiometric measurements were used to determine the association constants for the formation of the complexes CaH2PO4(+), CaHPO4, and CaPO4(-) in solutions of calcium phosphate at 25.0 and 37.0C. Approximate values of the thermodynamic functions for the...

A. Chughtai R. Marshall G. H. Nancollas



Calcium Phosphate Precipitation in Wastewater Treatment.  

National Technical Information Service (NTIS)

Precipitation of calcium phosphate from both synthetically derived wastewater and from actual wastewater was investigated. An amorphous tricalcium phosphate was the steady state solid phase that controlled dissolved phosphate residuals. The solubility of ...

A. B. Menar D. Jenkins



Sintering of calcium phosphate bioceramics.  


Calcium phosphate ceramics have become of prime importance for biological applications in the field of bone tissue engineering. This paper reviews the sintering behaviour of these bioceramics. Conventional pressureless sintering of hydroxyapatite, Ca10(PO4)6(OH)2, a reference compound, has been extensively studied. Its physico-chemistry is detailed. It can be seen as a competition between two thermally activated phenomena that proceed by solid-state diffusion of matter: densification and grain growth. Usually, the objective is to promote the first and prevent the second. Literature data are analysed from sintering maps (i.e. grain growth vs. densification). Sintering trajectories of hydroxyapatite produced by conventional pressureless sintering and non-conventional techniques, including two-step sintering, liquid phase sintering, hot pressing, hot isostatic pressing, ultrahigh pressure, microwave and spark plasma sintering, are presented. Whatever the sintering technique may be, grain growth occurs mainly during the last step of sintering, when the relative bulk density reaches 95% of the maximum value. Though often considered very advantageous, most assisted sintering techniques do not appear very superior to conventional pressureless sintering. Sintering of tricalcium phosphate or biphasic calcium phosphates is also discussed. The chemical composition of calcium phosphate influences the behaviour. Similarly, ionic substitutions in hydroxyapatite or in tricalcium phosphate create lattice defects that modify the sintering rate. Depending on their nature, they can either accelerate or slow down the sintering rate. The thermal stability of compounds at the sintering temperature must also be taken into account. Controlled atmospheres may be required to prevent thermal decomposition, and flash sintering techniques, which allow consolidation at low temperature, can be helpful. PMID:23212081

Champion, E



Characterization of calcium phosphate cements modified by addition of amorphous calcium phosphate  

Microsoft Academic Search

In this study the influence of amorphous calcium phosphate (ACP) on the setting of, and the formed apatite crystallite size in, a calcium phosphate cement (CPC) based on ?-tricalcium phosphate (?-TCP) or tetracalcium phosphate (TTCP)\\/monocalcium phosphate monohydrate (MCPM) was investigated. Setting times at 22°C were measured in air atmosphere; those at 37°C were measured at 100% relative humidity. The phase

Natasja M. F. Van den Vreken; Ilse Y. Pieters; Heidi A. Declercq; Maria J. Cornelissen; Ronald M. H. Verbeeck



Development of Calcium Phosphate-gelatin Composites  

NSDL National Science Digital Library

This study was performed to investigate and develop a biomaterial of calcium phosphate/gelatin to be used as an injectable bone substitute. Gelatin is an ideal medium to transfer calcium phosphate because it is biocompatible, biodegradable, cheap, and can be injected without open surgery. The interaction of calcium and phosphate with gelatin will be studied; these include solubility, titration and precipitation. The calcium phosphate/gelatin composites will be characterized by chemical analysis, x-ray powder diffraction, and infrared spectroscopy. The mechanical strength, such as DTS, will also be investigated.

Hwang, Jesse



Application of Calcium Phosphate Materials in Dentistry  

PubMed Central

Calcium phosphate materials are similar to bone in composition and in having bioactive and osteoconductive properties. Calcium phosphate materials in different forms, as cements, composites, and coatings, are used in many medical and dental applications. This paper reviews the applications of these materials in dentistry. It presents a brief history, dental applications, and methods for improving their mechanical properties. Notable research is highlighted regarding (1) application of calcium phosphate into various fields in dentistry; (2) improving mechanical properties of calcium phosphate; (3) biomimetic process and functionally graded materials. This paper deals with most common types of the calcium phosphate materials such as hydroxyapatite and tricalcium phosphate which are currently used in dental and medical fields.

Al-Sanabani, Jabr S.; Al-Sanabani, Fadhel A.



21 CFR 182.6215 - Monobasic calcium phosphate.  

Code of Federal Regulations, 2010 CFR

... 2009-04-01 false Monobasic calcium phosphate. 182.6215 Section 182.6215...Sequestrants 1 § 182.6215 Monobasic calcium phosphate. (a) Product. Monobasic calcium phosphate. (b) Conditions of use....



21 CFR 582.6215 - Monobasic calcium phosphate.  

Code of Federal Regulations, 2010 CFR

... 2009-04-01 false Monobasic calcium phosphate. 582.6215 Section 582.6215...Sequestrants 2 § 582.6215 Monobasic calcium phosphate. (a) Product. Monobasic calcium phosphate. (b) Conditions of use....



21 CFR 182.6215 - Monobasic calcium phosphate.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 2013-04-01 false Monobasic calcium phosphate. 182.6215 Section 182...Sequestrants 1 § 182.6215 Monobasic calcium phosphate. (a) Product. Monobasic calcium phosphate. (b) Conditions of...



21 CFR 582.6215 - Monobasic calcium phosphate.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 2013-04-01 false Monobasic calcium phosphate. 582.6215 Section 582...Sequestrants 2 § 582.6215 Monobasic calcium phosphate. (a) Product. Monobasic calcium phosphate. (b) Conditions of...



Nanocrystalline calcium phosphate ceramics in biomedical engineering  

Microsoft Academic Search

Nanocrystalline calcium phosphate based bioceramics are the new rage in biomaterials research. Conventionally, calcium phosphates based materials are preferred as bone grafts in hard tissue engineering because of their superior biocompatibility and bioactivity. However, this group of bioceramics exhibits poor mechanical performance, which restricts their uses in load bearing applications. The recent trend in bioceramic research is mainly concentrated on

Samar J. Kalita; Abhilasha Bhardwaj; Himesh A. Bhatt



Polymeric calcium phosphate cements: setting reaction modifiers.  


In this study, the effects of several additives on the setting behavior and mechanical properties of polymeric calcium phosphate cements were investigated. The cements were derived from a polycarboxylic acid (PCA) and a calcium phosphate cement (CPC) powder that consisted of equimolar amounts of tetracalcium phosphate (TTCP) and dicalcium phosphate (DCPA). Retardation of the setting reaction in the PCA-CPC cements was observed by adding tribasic sodium phosphate and fluorides such as stannous fluoride, zirconium(IV) fluoride and titanium(IV) fluoride. It was found that increasing the concentration of these additives decreased the mechanical strength of the cements. However, improvements in both setting and mechanical properties for the PCA-CPC cements were observed by the combined use of 8% (w/w) stannous fluoride and 10% (w/w) tartaric acid. The mechanical properties of the PCA-CPC cement also were improved by adding calcium acetate, calcium methacrylate, zirconium(IV) sulfate and phosphonoacetic acid. PMID:8299870

Miyazaki, K; Horibe, T; Antonucci, J M; Takagi, S; Chow, L C



Calcium and Phosphate Control by Dialysis Treatments  

Microsoft Academic Search

Calcium and phosphate changes, besides their involvement in bone disease, have been claimed to also be involved in the increased vascular morbidity and mortality of dialysis patients. Even after the recent advances of therapeutic options, their control still remains a challenging problem. Dialysis treatment is a basic approach to the control of these two electrolytes. Calcium control by dialysis is

Piergiorgio Messa; Roberta Cerutti; Brigida Brezzi; Carlo Alfieri; Mario Cozzolino



Formation of hydroxyapatite in new calcium phosphate cements  

Microsoft Academic Search

SynopsisTetracalcium phosphate (TTCP) has been shown previously to be an essential component of self-setting calcium phosphate cements that form hydroxyapatite (HA) as the only end-product. We report herein on a new self-setting calcium phosphate cement that does not contain TTCP. These cements consist of dicalcium phosphate anhydrous (DCPA), dicalcium phosphate dihydrate (DCPD), ?-tricalcium phosphate, or amorphous calcium phosphate and, as

S. Takagi; L. C. Chow; K. Ishikawa



Physiology of Calcium and Phosphate Metabolism: 1980 Refresher Course, Syllabus.  

ERIC Educational Resources Information Center

|This syllabus reviews information concerning calcium and phosphate regulation. Topics of interest include the following: calcium metabolism, phosphorus metabolism, bone, parathyroid hormone, calcitonin, and vitamin D. (CS)|

Knox, Franklyn G., Ed.



Topotactic exchange and intercalation of calcium phosphate  

Microsoft Academic Search

The precursor (NH4)2Ca(H2PO4)2?H2O (CaAP) compound was obtained by combining a calcium chloride solution with dibasic ammonium phosphate. After submitting it to a thermal treatment, crystalline calcium phosphate, Ca(H2PO4)2?H2O (CaP) was isolated. X-ray diffraction patterns for this compound indicated good crystallinity, with a peak at 2?=12.8°, to give an interlamellar distance of 697 pm, which changed to 1550 pm, when the

Cicero B. A. Lima; Claudio Airoldi



In vivo study of a calcium phosphate cement consisting of ?-tricalcium phosphate\\/dicalcium phosphate dibasic\\/tetracalcium phosphate monoxide  

Microsoft Academic Search

Prehardened calcium phosphate cement consisting of ?-tricalcium phosphate (?-TCP), dicalcium phosphate dibasic (DCPD) and tetracalcium phosphate monoxide (TeCP) was implanted in rabbit mandibles and back muscles, and studied histologically and microradiographically. In the mandibles, new bone formation occurred around the implants and increased in quantity the longer the implant period lasted. Histology, microradiography and scanning electron microscopy (SEM) demonstrated direct

K. Kurashina; H. Kurita; A. Kotani; H. Takeuchi; M. Hirano



Role of Iron in Calcium Phosphate Glasses.  

National Technical Information Service (NTIS)

Some physical properties of calcium phosphate glasses containing up to about 26 mol% Fe2O3 were studied. Pronounced changes in properties were observed at compositions containing about 6, 10, and 13 mol% Fe2O3. The X-ray diffraction spectra of devitrified...

A. M. Bishay L. Makar



Calcium orthophosphates in medicine: from ceramics to calcium phosphate cements  

Microsoft Academic Search

Calcium phosphate (CaP) compounds are becoming of increasingly great importance in the fiel of biomaterials and, in particular, as bone substitutes. Recent discoveries have accelerated this process, but have simultaneously rendered the field more complicated for the everyday user. Subtle differences in composition and structure of CaP compounds may have a profound effect on their in vivo behaviour. Therefore, the

M. Bohner



Calcium phosphate ceramics in drug delivery  

NASA Astrophysics Data System (ADS)

Calcium phosphate (CaP) particulates, cements and scaffolds have attracted significant interest as drug delivery vehicles. CaP systems, including both hydroxyapaptite and tricalcium phosphates, possess variable stoichiometry, functionality and dissolution properties which make them suitable for cellular delivery. Their chemical similarity to bone and thus biocompatibility, as well as variable surface charge density contribute to their controlled release properties. Among specific research areas, nanoparticle size, morphology, surface area due to porosity, and chemistry controlled release kinetics are the most active. This article discusses CaP systems in their particulate, cements, and scaffold forms for drug, protein, and growth factor delivery toward orthopedic and dental applications.

Bose, Susmita; Tarafder, Solaiman; Edgington, Joe; Bandyopadhyay, Amit



Hydrolyses of calcium phosphates-allografts composite in physiological solutions.  


Hydrolysis of calcium phosphates cement- allografts composite in calf serum and that in saline were examined in comparison with those of the calcium phosphates cement in both the solutions. The calcium phosphates cement consists of alpha-tricalcium phosphate (alpha-TCP), tetracalcium phosphate (TetCP), dicalcium phosphate dihydrate (DCPD), and hydroxyapatite (HAP), which is clinically used as Biopex. In the hydrolyses of Biopex-allografts composite in both the solutions, the calcium phosphates cement was transformed into HAP. On the other hand, in the hydrolyses of Biopex, HAP was formed after 1 day and octacalcium phosphate (OCP) was gradually formed after 7 days. In the presence of allografts, plate-like crystals were deposited and in the absence of allografts, needle-like crystals were deposited in both the solutions. By the addition of allografts, the hydrolysis process of the calcium phosphates cement was significantly changed. PMID:16617417

Nomoto, Takuya; Haraguchi, Keiji; Yamaguchi, Shunro; Sugano, Nobuhiko; Nakayama, Hirokazu; Sekino, Tohru; Niihara, Koichi



Physiology of calcium, phosphate and magnesium.  


The physiology of calcium and the other minerals involved in its metabolism is complex and intimately tied in with the physiology of bone. Five principal humoral factors are involved in maintaining plasma levels of calcium, magnesium and phosphate and coordinating the balance between these and their content in bone. The transmembrane transport of these elements is dependent on a series of complex mechanisms that are controlled by these hormones. The plasma concentration of calcium is initially sensed by a calcium-sensing receptor which then sets up a cascade of events that initially determines parathyroid hormone secretion and eventually results in a specific action within the target organs, mainly bone and kidney. This chapter describes the physiology of these humoral factors and relates them to the pathological processes that give rise to disorders of calcium and bone metabolism. It details the stages in the calcium cascade and describes the effects on the various target organs. The pathology of disorders of bone and calcium metabolism is described in detail in the relevant chapters. PMID:19494658

Allgrove, Jeremy



Calorimetric investigations of calcium phosphate precipitation  

NASA Astrophysics Data System (ADS)

The kinetics of the early stages of crystallization of calcium phosphate under different initial solution compositions have been studied by calorimetric and light scattering methods. It is found that the total heat of formation of calcium phosphate is negative and depends on the molar ratio Ca/P and the initial pH of the mixture. At initial pH 7.40 and pH 8.62, there are relatively strong repeated endothermic heat effects. The character of this heat conversion is not clear. The light scattering studies do not rule out the possibility of the existence of Ca 4 H(PO 4 ) 3 ·½H 2 O (OCP) crystals in this region at these initial solution pH's rather than Ca 5 (PO 4 ) 3 OH (HAP) and CaHPO 4 ·2H 2 O (DCPD) expected to crystallize at initial higher and lower values of pH, respectively.

Kibalczyc, Wiktor



Calcium phosphate cements comprising autologous bone  

US Patent & Trademark Office Database

Aspects of the invention include methods for producing flowable compositions, e.g. pastes, that set into calcium phosphate containing products, where the products include autologous bone. Aspects of the invention further include compositions produced by the methods, as well as kits for preparing the same. The subject methods and compositions produced thereby find use in a variety of applications, including hard tissue repair applications.

Constantz; Brent R. (Cupertino, CA)



Hydroxyapatite formation from a hydrated calcium monohydrogen phosphate precursor  

Microsoft Academic Search

Hydrated calcium monohydrogen phosphate is proposed as the logical precursor in the formation of hydroxyapatite and a unifying theory for the formation of low calcium, or defect apatites, is presented. Structural relationships between calcium monohydrogen phosphate dihydrate and hydroxyapatite indicate that either material can provide the atomic arrangment for the epitaxial growth of one on the other. The formation of

Marion D. Francis; Ned C. Webb



Amorphous calcium phosphate and its application in dentistry  

Microsoft Academic Search

Amorphous Calcium Phosphate (ACP) is an essential mineral phase formed in mineralized tissues and the first commercial product\\u000a as artificial hydroxyapatite. ACP is unique among all forms of calcium phosphates in that it lacks long-range, periodic atomic\\u000a scale order of crystalline calcium phosphates. The X-ray diffraction pattern is broad and diffuse with a maximum at 25 degree\\u000a 2 theta, and

Jie Zhao; Yu Liu; Wei-bin Sun; Hai Zhang



Microstructure analysis of calcium phosphate formed in tendon  

Microsoft Academic Search

The surface of soft tendon tissue has been modified using calcium phosphate in order for the tendon to directly connect with hard bone and reconstruct an injured ligament. Calcium phosphate was coated onto the tendon in a soaking process using alternating a CaCl2 (200 mM) and a Na2HPO4 (120 mM) solution. According to SEM\\/EDX observations, calcium phosphate was formed, not

I. Yamaguchi; T. Kogure; M. Sakane; S. Tanaka; A. Osaka; J. Tanaka



Properties and mechanisms of fast-setting calcium phosphate cements  

Microsoft Academic Search

The setting time of a calcium phosphate cement consisting of tetracalcium phosphate (TTCP) and dicalcium phosphate anhydrous (DCPA) was reduced from 30 to 5 min by use of a cement liquid that contained a phosphate concentration of 0.25 mol\\/l or higher. The diametral tensile strength and conversion of the cement ingredients to hydroxyapatite (OHAp) during the first 3 h were

Kunio Ishikawa; Shozo Takagi; Laurence C. Chow; Yoshiko Ishikawa



Histopathological reactions of calcium phosphate cement.  


Calcium phosphate cement (CPC) consisting of Ca4 (PO4)2O and CaHPO4 (2H2O) was recently developed. This study evaluated in vivo aspects of CPC and CPC mixtures compared to those of commercial hydroxyapatite (HP) and several endodontic materials: Grossman's cement (GC), calcium hydroxide-iodine paste (CHP) and gutta-percha plate (GP). Biocompatibility of subcutaneous implants in Donryu rats was evaluated after one month. Results showed very slight inflammatory reactions from CPC, CPC mixtures and HP. The materials were surrounded by thin fibrous connective tissues with a small number of lymphocytes and plasma cells. Severe inflammatory reactions were provoked by GC. Granulation tissues induced by CHP resembled those of pseudoxanthomatous granuloma. The GP material was encapsulated by relatively thick fibrous connective tissues with little inflammatory reactions. PMID:1327659

Sugawara, A; Nishiyama, M; Kusama, K; Moro, I; Nishimura, S; Kudo, I; Chow, L C; Takagi, S



Dissolution kinetics of calcium phosphate coatings.  


Plasma spray and high velocity oxy-fuel (HVOF) techniques produce coatings with varying composition and amounts of amorphous and crystalline phases. For coatings containing greater amorphous phases, a higher release of calcium ions is evident when samples are placed in Hank's calcium-free balanced salt solutions. Calcium is released from the amorphous phases in the coating, a conclusion that is supported by x-ray powder diffraction (XRD) results. Ion beam sputtering and RF magnetron sputtering under lower energy conditions produce amorphous coatings that will dissolve in a very short time period. When heat treated, crystalline phases are produced in the coatings. Heat-treated coatings are significantly more stable than the amorphous coatings. The dissolution rates of both amorphous and crystalline coatings produced by RF magnetron sputtering have been measured under constant solution conditions at pH 6.50. No reprecipitation is possible under these conditions. The amorphous coating dissolved at a significantly higher rate than the heat-treated coating. Reprecipitation of calcium phosphate onto amorphous coatings is possible in a physiological pH solution. Under these conditions, the dissolution rate of the amorphous coating is four times slower than at the pH 6.50 conditions. PMID:10196809

Burke, E M; Lucas, L C



[Bone and tooth in calcium and phosphate metabolism].  


Tight regulation of serum concentrations of calcium and phosphate is indispensable for maintaining normal physiological condition. Imbalance of this regulation leads to pathophysiological disorders including heart disease, chronic kidney disease, and ectopic calcification. Formation and mineralization of bone and tooth are greatly influenced by calcium and phosphate metabolism since both organs are mainly consist of calcium-phosphate. Calcium and phosphate homeostasis is under hormonal control on its target organs such as kidney, bone and intestine. Calcium and phosphate are absorbed in intestine and reabsorbed and excreted in kidney. Bone store and release them in response to changing physiological demand by osteoblastic bone formation and osteoclastic bone resorption. Bone is also important as an endocrine organ that releases FGF23 from osteocytes, a novel hormone that targets the kidney to inhibit phosphate reabsorption and 1?, 25 (OH) (2)D(3) production. PMID:22201094

Tamamura, Yoshihiro; Yamaguchi, Akira



Agronomic effectiveness of partially acidulated rock phosphate and fused calcium-magnesium phosphate compared with superphosphate  

Microsoft Academic Search

The agronomic effectiveness of two partially acidulated rock phosphate (PARP) fertilizers, made from either North Carolina or Moroccan apatite rock phosphate, and a fused calcium-magnesium phosphate (thermal phosphate or TP), was compared with the effectiveness of superphosphate in two glasshouse experiments. A different lateritic soil from Western Australia was used for each experiment. Oats (Avena sativa) were grown in one

M. D. A. Bolland; R. N. Glencross; R. J. Gilkes; Vijay Kumar



Tissue responses of calcium phosphate cement: a study in dogs  

Microsoft Academic Search

The in vivo properties of a new kind of calcium phosphate cement were investigated in this study. Calcium phosphate cement was implanted as paste into femoral bone and dorsal muscle of dogs for 3 and 6 months, and as prehardened form into thigh muscles of dogs for 1, 2 and 6 months. Histology was performed on thin un-decalcified sections. No

Huipin Yuan; Yubao Li; JD de Bruijn; K de Groot; Xingdong Zhang



Fiber-enriched double-setting calcium phosphate bone cement  

Microsoft Academic Search

Calcium phosphate bone cements are useful in orthopedics and traumatology, their main advantages being their biocompatibility and bioactivity, which render bone tissue osteoconductive, providing in situ hardening and easy handling. However, their low mechanical strength, which, in the best of cases, is equal to the trabecular bone, and their very low toughness are disadvantages. Calcium phosphate cement compositions with mechanical

Luis Alberto dos Santos; Raul Garcia Carrodeguas; Anselmo Ortega Boschi


Nanostructured calcium phosphates for biomedical applications: novel synthesis and characterization  

Microsoft Academic Search

Materials play a key role in several biomedical applications, and it is imperative that both the materials and biological aspects are clearly understood for attaining a successful biological outcome. This paper illustrates our approach to implement calcium phosphates as gene delivery agents. Calcium phosphates (CaP) belong to the family of biocompatible apatites and there are several CaP phases, the most

Prashant N. Kumta; Charles Sfeir; Dong-Hyun Lee; Dana Olton; Daiwon Choi



Setting Reaction and Hardening of an Apatitic Calcium Phosphate Cement  

Microsoft Academic Search

The combination of self-setting and biocompatibility makes calcium phosphate cements potentially useful materials for a variety of dental applications. The objective of this study was to investigate the setting and hardening mechanisms of a cement-type reaction leading to the formation of calcium-deficient hydroxyapatite at low temperature. Reactants used were a-tricalcium phosphate containing 17 wt% ?-tricalcium phosphate, and 2 wt% of

M. P. Ginebra; E. Fernández; E. A. P. De Maeyer; R. M. H. Verbeeck; M. G. Boltong; J. Ginebra; F. C. M. Driessens; J. A. Planell



Biphasic calcium phosphate bioceramics: preparation, properties and applications  

Microsoft Academic Search

Biphasic calcium phosphate (BCP) bioceramics belong to a group of bone substitute biomaterials that consist of an intimate mixture of hydroxyapatite (HA), Ca10(PO4)6(OH)2, and beta-tricalcium phosphate (ß-TCP), Ca3(PO4)2, of varying HA\\/ß-TCP ratios. BCP is obtained when a synthetic or biologic calcium-deficient apatite is sintered at temperatures at and above 700 °C. Calcium deficiency depends on the method of preparation (precipitation,

R. Z. LeGeros; S. Lin; R. Rohanizadeh; D. Mijares; J. P. LeGeros



Effect of the calcium to phosphate ratio of tetracalcium phosphate on the properties of calcium phosphate bone cement.  


Six different tetracalcium phosphate (TTCP) products were synthesized by solid state reaction at high temperature by varying the overall calcium to phosphate ratio of the synthesis mixture. The objective was to evaluate the effect of the calcium to phosphate ratio on a TTCP-dicalcium phosphate dihydrate (DCPD) cement. The resulting six TTCP-DCPD cement mixtures were characterized using X-ray diffraction analysis, scanning electron microscopy, and pH measurements. Setting times and compressive strength (CS) were also measured. Using the TTCP product with a Ca/P ratio of 2.0 resulted in low strength values (25.61 MPa) when distilled water was used as the setting liquid, even though conversion to hydroxyapatite was not prevented, as confirmed by X-ray diffraction. The suspected CaO presence in this TTCP may have affected the cohesiveness of the cement mixture but not the cement setting reaction, however no direct evidence of CaO presence was found. Lower Ca/P ratio products yielded cements with CS values ranging from 46.7 MPa for Ca/P ratio of 1.90 to 38.32 MPa for Ca/P ratio of 1.85. When a dilute sodium phosphate solution was used as the setting liquid, CS values were 15.3% lower than those obtained with water as the setting liquid. Setting times ranged from 18 to 22 min when water was the cement liquid and from 7 to 8 min when sodium phosphate solution was used, and the calcium to phosphate ratio did not have a marked effect on this property. PMID:17876802

Burguera, Elena F; Guitian, Francisco; Chow, Laurence C



Are we mismanaging calcium and phosphate metabolism in renal failure?  

Microsoft Academic Search

Secondary hyperparathyroidism and renal osteodystrophy are the consequences of abnormal calcium, phosphate, and calcitriol metabolism ensuing from renal failure. Evidence suggests that calcium balance tends to become negative as we grow older than 35 years of age; however, the current dialysis modalities provide patients regardless of age with excessive calcium during dialysis. Administration of calcitriol in the management of hyperparathyroidism

Chen H. Hsu



Calcium phosphate nanoparticles for transcutaneous vaccine delivery.  


The main objective of this study was to investigate the potential of calcium phosphate (CAP) nanoparticles for transcutaneous vaccine delivery. CAP nanoparticles were prepared by nanoprecipitation method followed by sequential adsorption of sugars and ovalbumin. Nanoparticles were characterized using dynamic light scattering, XRD, ATR-FTIR, and microscopy methods. In-vitro release of ovalbumin from nanoparticles was studied in phosphate buffer (pH 7.4). In-vivo immunization studies were carried out in Balb/C mice. The size and zeta potential of ovalbumin-sugar adsorbed CAP nanoparticles was 350 +/- 22.5 nm and -12.93 +/- 1.02 mV respectively. Around 60% ovalbumin was released from nanoparticles within 24 hrs. To test the feasibility for transcutaneous vaccine delivery, the nanoparticles were applied in mice after removing the stratum corneum by tape-stripping. In the positive control group, the nanoparticles were administered by intradermal injection. Ovalbumin-sugar coated CAP nanoparticles showed significantly higher antibody titers (Total IgG and IgG1) compared to ovalbumin alone. IgG2a antibodies were only seen with intradermal injection. Both topical and intradermal treatment groups showed splenocyte proliferation when re-stimulated with ovalbumin. The results from this study demonstrate the potential of using CAP nanoparticles for transcutaneous vaccine delivery. PMID:23627076

Sahdev, Preety; Podaralla, Satheesh; Kaushik, Radhey S; Perumal, Omathanu



Reaction of calcium phosphate cements with different amounts of tetracalcium phosphate and dicalcium phosphate anhydrous.  


Calcium phosphate cements (CPCs) with different amounts of tetracalcium phosphate (TTCP) and dicalcium phosphate anhydrous (DCPA) (TTCP/DCPA molar ratio from 0.25 to 2.00) were prepared to further understand the setting reaction and the factors that could influence the properties of CPCs. Quantitative X-ray diffraction patterns, Fourier transform IR spectra, and diametral tensile strength of the set mass were measured along with pH measurements of the CPC suspension. Calcium-deficient hydroxyapatite (d-HAP) with a calcium to phosphate molar ratio of approximately 1.5 was formed initially in the CPC setting consisting of an equimolar mixture of TTCP and DCPA. This gradually transformed into stoichiometric HA (s-HA) with increasing incubation time. The s-HA was formed in the initial stage when the CPC contained an excess amount of TTCP. In contrast, maturation to s-HAP was slow when the CPC contained excess amounts of DCPA. The highest mechanical strength of set CPC was associated with an equimolar mixture of TTCP and DCPA, and the mechanical strength decreased as the TTCP/DCPA molar ratio deviated from 1.00. We concluded, therefore, that the setting reaction and the nature of the resulting set mass are dependent on the molar ratios of TTCP and DCPA. PMID:10398011

Ishikawa, K; Takagi, S; Chow, L C; Suzuki, K



Chemistry misconceptions associated with understanding calcium and phosphate homeostasis.  


Successful learning of many aspects in physiology depends on a meaningful understanding of fundamental chemistry concepts. Two conceptual diagnostic questions measured student understanding of the chemical equilibrium underlying calcium and phosphate homeostasis. One question assessed the ability to predict the change in phosphate concentration when calcium ions were added to a saturated calcium phosphate solution. Fifty-two percent of the students correctly predicted that the phosphate concentration would decrease in accord with the common ion effect. Forty-two percent of the students predicted that the phosphate concentration would not change. Written explanations showed that most students failed to evoke the idea of competing chemical equilibria. A second question assessed the predicted change in calcium concentration after solid calcium phosphate was added to a saturated solution. Only 11% of the students correctly predicted no change in calcium concentration; 86% of the students predicted an increase, and many based their prediction on a mistaken application of Le Chatelier's principle to heterogeneous equilibria. These results indicate that many students possess misconceptions about chemical equilibrium that may hamper understanding of the processes of calcium and phosphate homeostasis. Instructors can help students gain greater understanding of these physiochemical phenomena by adopting strategies that enable students achieve more accurate conceptions of chemical equilibria. PMID:19948683

Cliff, William H



Chemistry misconceptions associated with understanding calcium and phosphate homeostasis  

NSDL National Science Digital Library

Successful learning of many aspects in physiology depends on a meaningful understanding of fundamental chemistry concepts. Two conceptual diagnostic questions measured student understanding of the chemical equilibrium underlying calcium and phosphate homeostasis. One question assessed the ability to predict the change in phosphate concentration when calcium ions were added to a saturated calcium phosphate solution. Fifty-two percent of the students correctly predicted that the phosphate concentration would decrease in accord with the common ion effect. Forty-two percent of the students predicted that the phosphate concentration would not change. Written explanations showed that most students failed to evoke the idea of competing chemical equilibria. A second question assessed the predicted change in calcium concentration after solid calcium phosphate was added to a saturated solution. Only 11% of the students correctly predicted no change in calcium concentration; 86% of the students predicted an increase, and many based their prediction on a mistaken application of Le Chatelier's principle to heterogeneous equilibria. These results indicate that many students possess misconceptions about chemical equilibrium that may hamper understanding of the processes of calcium and phosphate homeostasis. Instructors can help students gain greater understanding of these physiochemical phenomena by adopting strategies that enable students achieve more accurate conceptions of chemical equilibria.

William H. Cliff (Niagara University Biology)



Effects of dietary calcium and phosphate on the intestinal interactions between calcium, phosphate, fatty acids, and bile acids.  

PubMed Central

Luminal free fatty acids and bile acids may damage the colonic epithelium and stimulate proliferation, which may increase the risk of colon cancer. It has been suggested that only soluble calcium ions (Ca2+) precipitate fatty acids and bile acids, thus reducing their lytic activity. Consequently, precipitation of luminal Ca2+ by dietary phosphate should inhibit these effects. To evaluate the proposed antagonistic effects of dietary calcium and phosphate, we studied the intestinal interactions between calcium, phosphate, fatty acids, and bile acids in rats fed purified diets that differed only in the concentrations of calcium and phosphate. Increased dietary calcium drastically decreased the solubility of fatty acids in the ileum, colon, and faeces, as well as the solubility of bile acids in the colon and faeces. Although dietary calcium strongly increased the total faecal fatty acid concentration and hardly affected the total faecal bile acid concentration, the fatty acid and bile acid concentrations in faecal water were drastically decreased by dietary calcium. Consequently, the lytic activity of faecal water was decreased. Dietary phosphate did not interfere with these intestinal effects of calcium. These results indicate that dietary phosphate does not inhibit the protective effects of dietary calcium on luminal solubility and the lytic activity of fatty and bile acids.

Govers, M J; Van der Meet, R



Osteoclastic resorption of calcium phosphate ceramics with different hydroxyapatite\\/?-tricalcium phosphate ratios  

Microsoft Academic Search

To study the influence of calcium phosphate ceramic solubility on osteoclastic resorption, neonatal rabbit bone cells were cultured for 2 days on hydroxyapatite (HA), ?-tricalcium phosphate (?-TCP) and two types of biphasic calcium phosphate (BCP) with HA\\/?-TCP ratios of 2575 and 7525. Solubility was regulated by varying the ratio of less-soluble HA and more-soluble ?-TCP. After removal of stromal cells

S. Yamada; D. Heymann; J.-M. Bouler; G. Daculsi



An equilibrium thermodynamic model of the sequestration of calcium phosphate by casein phosphopeptides  

Microsoft Academic Search

Sequestration of calcium phosphate by caseins occurs in the Golgi region of mammary secretory cells during lactation, where it helps to prevent calcification of the gland and to deliver high concentrations of calcium and phosphate to the neonate in the form of milk. Calcium phosphate nanoclusters are formed when a core of amorphous calcium phosphate is sequestered within a shell

Elaine M. Little; Carl Holt



An intermediate state in hydrolysis of amorphous calcium phosphate  

Microsoft Academic Search

Summary  The hydrolysis of previously prepared amorphous calcium phosphate (ACP) was studied in a solution “saturated” with ACP; this\\u000a eliminated the initial consumption of acid due to ACP dissolution. The procedure established that conversion of a high-concentration\\u000a ACP slurry to an apatite involves two processes: the first process consumes acid and indicates the formation of a more acidic\\u000a calcium phosphate intermediary

M. S. Tung; W. E. Brown



Calcium phosphate-based ceramic and composite materials for medicine  

NASA Astrophysics Data System (ADS)

The topical problems in chemistry and technology of materials based on calcium phosphates aimed at both the replacement of damaged bone tissue and its regeneration are discussed. Specific features of the synthesis of nanocrystalline powders and the fabrication of ceramic implants are described. Advances in the development of porous scaffolds from resorbable and osteoconductive calcium phosphates and of hybrid composites that form the basis of bone tissue engineering are considered.

Barinov, Sergei M.



Effective formulations for the preparation of calcium phosphate bone cements  

Microsoft Academic Search

In the system CaO-P2O5-H2O 13 different solids with varying Ca\\/P ratios are known. In addition calcium phosphates containing other biocompatible constituents like Na, or K, or Mg or Cl or carbonate, are known. Therefore, a large number of combinations of such compounds is possible which might result in the formation of calcium phosphate cements upon mixing with water. However, the

F. C. M. Driessens; M. G. Boltong; O. Bermúdez; J. A. Planell; M. P. Ginebra; E. Fernández



Amorphous calcium phosphate in casein micelles of bovine milk  

Microsoft Academic Search

Summary  The calcium phosphate remaining after hydrazine deproteination of casein micelles isolated from bulk skim milk exhibits under\\u000a the electron microscope a very fine and uniform granularity being formed by small subunits with a true diameter of approximately\\u000a 2.5 nm. This material, which is about 10 percent by weight citrate, termed calcium phosphate citrate (CPC) complex, also contains\\u000a Mg and Zn

T. C. A. McGann; R. D. Kearney; W. Buchheim; A. S. Posner; F. Betts; N. C. Blumenthal



Premixed macroporous calcium phosphate cement scaffold  

PubMed Central

Calcium phosphate cement (CPC) sets in situ to form resorbable hydroxyapatite and is promising for orthopaedic applications. However, it requires on-site powder-liquid mixing during surgery, which prolongs surgical time and raises concerns of inhomogeneous mixing. The objective of this study was to develop a premixed CPC scaffold with macropores suitable for tissue ingrowth. To avoid the on-site powder-liquid mixing, the CPC paste was mixed in advance and did not set in storage; it set only after placement in a physiological solution. Using 30% and 40% mass fractions of mannitol porogen, the premixed CPC scaffold with fibers had flexural strength (mean ± sd; n = 5) of (3.9 ± 1.4) MPa and (1.8 ± 0.8) MPa, respectively. The scaffold porosity reached (68.6 ± 0.7)% and (74.7 ± 1.2)%, respectively. Osteoblast cells colonized in the surface macropores of the scaffold and attached to the hydroxyapatite crystals. Cell viability values for the premixed CPC scaffold was not significantly different from that of a conventional non-premixed CPC known to be biocompatible (P > 0.1). In conclusion, using fast-dissolving porogen and slow-dissolving fibers, a premixed macroporous CPC scaffold was developed with strength approaching the reported strengths of sintered porous hydroxyapatite implants and cancellous bone, and non-cytotoxicity similar to a biocompatible non-premixed CPC.

Carey, Lisa E.; Simon, Carl G.



Transient amorphous calcium phosphate in forming enamel.  


Enamel, the hardest tissue in the body, begins as a three-dimensional network of nanometer size mineral particles, suspended in a protein gel. This mineral network serves as a template for mature enamel formation. To further understand the mechanisms of enamel formation we characterized the forming enamel mineral at an early secretory stage using X-ray absorption near-edge structure (XANES) spectromicroscopy, transmission electron microscopy (TEM), FTIR microspectroscopy and polarized light microscopy. We show that the newly formed enamel mineral is amorphous calcium phosphate (ACP), which eventually transforms into apatitic crystals. Interestingly, the size, shape and spatial organization of these amorphous mineral particles and older crystals are essentially the same, indicating that the mineral morphology and organization in enamel is determined prior to its crystallization. Mineralization via transient amorphous phases has been previously reported in chiton teeth, mollusk shells, echinoderm spicules and spines, and recent reports strongly suggest the presence of transient amorphous mineral in forming vertebrate bones. The present finding of transient ACP in murine tooth enamel suggests that this strategy might be universal. PMID:19217943

Beniash, Elia; Metzler, Rebecca A; Lam, Raymond S K; Gilbert, P U P A



Formation of hydroxyapatite in new calcium phosphate cements.  


Tetracalcium phosphate (TTCP) has been shown previously to be an essential component of self-setting calcium phosphate cements that form hydroxyapatite (HA) as the only end-product. We report herein on a new self-setting calcium phosphate cement that does not contain TTCP. These cements consist of dicalcium phosphate anhydrous (DCPA), dicalcium phosphate dihydrate (DCPD), alpha-tricalcium phosphate, or amorphous calcium phosphate and, as an additional source of calcium, calcium hydroxide or calcium carbonate. These cements require the use of a phosphate (0.2 moll(-1) or higher) solution or a high pH solution as the cement liquid. The cements harden in relatively short time (5-30 min) and form HA as the dominant end-product in 24 h. The diametral tensile strengths of the 24-h samples are in the range of 0.2 to 7.5 MPa. Results from X-ray diffraction studies suggest that the cement setting is caused by rapid HA formation induced by the high phosphate concentration of the cement liquid. Because DCPA and DCPD are highly soluble at pH values above 12.7, which is the pK3 of phosphoric acid, high phosphate concentration in the slurry solution was also attainable by using a highly alkaline solution as the cement liquid. The physicochemical properties of these cements are comparable to those of TTCP-containing cements, and the new cements may be expected to have in vivo characteristics similar to those of TTCP-containing cements as well. PMID:9830985

Takagi, S; Chow, L C; Ishikawa, K



Fabrication of calcium phosphate-calcium sulfate injectable bone substitute using chitosan and citric acid  

Microsoft Academic Search

In this study, an injectable bone substitute (IBS) consisting of citric acid, chitosan solution as the liquid phase and tetra\\u000a calcium phosphate (TTCP), dicalcium phosphate anhydrous (DCPA) and calcium sulfate hemihydrate (CSH) powders as the solid\\u000a phase was prepared. Four groups containing different percentages (0–30%) of calcium sulfate hemihydrate (CSH, CaSO4 · 0.5H2O) were investigated. Initial setting times for IBS with CSH

Ho-Yeon Song; A. H. M. Esfakur Rahman; Byong-Taek Lee



Chemistry Misconceptions Associated with Understanding Calcium and Phosphate Homeostasis  

ERIC Educational Resources Information Center

|Successful learning of many aspects in physiology depends on a meaningful understanding of fundamental chemistry concepts. Two conceptual diagnostic questions measured student understanding of the chemical equilibrium underlying calcium and phosphate homeostasis. One question assessed the ability to predict the change in phosphate concentration…

Cliff, William H.



On the development of an apatitic calcium phosphate bone cement  

Microsoft Academic Search

Development of an apatitic calcium phosphate bone cement is reported. 100 ? Particles of tetracalcium phosphate (TTCP) and\\u000a dicalcium phosphate dihydrate (DCPD) were mixed in equimolar ratio to form the cement powder. The wetting medium used was\\u000a distilled water with Na2HPO4 as accelerator to manipulate the setting time. The cement powder, on wetting with the medium, formed a workable putty.

Manoj Komath; H. K. Varma; R. Sivakumar



Modulation of ileal calcium transport by phosphate-exchanging compounds.  


Calcium transport in the ileal-ligated loop was studied in the adult rat in the presence of either phosphate alone or phosphate-binding compounds, namely either hydroxylated or aminated substances. Sorbitol or creatine (50 mM) added to a 10-mM CaCl2 solution, which was instilled into ileal loop, markedly enhanced calcium transport, as determined by 45Ca radioactivity appearing in plasma and from 45Ca radioactivity disappearing from the loop. The presence of both compounds maintained Ca soluble in an instilled solution at a constant concentration, whereas with a control solution the Ca concentration progressively decreased towards zero after an incubation period of 60 min. Phosphate, which was either simultaneously added with sorbitol or creatine or which was present as sorbitol or creatine phosphate, led to an equally marked decrease in calcium transport. Calcium transfer was even more reduced when phosphate alone was present with calcium in the ileal loop, in the absence of sorbitol. Similar to the above phosphate-binding compounds, adenosine and its constitutive component, ribose, increased calcium transfer, whereas adenine, the other constitutive component of adenosine, was ineffective. Guanosine was twice more active than adenosine in stimulating ileal calcium transport. Interestingly, the structure of guanosine allows the binding of two phosphates, with one binding site being on the ribose and the other on the guanine base moiety. Thus guanosine is capable of binding a greater amount of phosphate than the two other aminated compounds examined, namely adenosine and alanine, when transphosphorylation from ATP is studied with intestinal microvilli preparations.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1328835

Dupuis, Y; Tardivel, S; Lacour, B; Fournier, P



Properties of Calcium Phosphate Cements With Different Tetracalcium Phosphate and Dicalcium Phosphate Anhydrous Molar Ratios.  


Calcium phosphate cements (CPCs) were prepared using mixtures of tetracalcium phosphate (TTCP) and dicalcium phosphate anhydrous (DCPA), with TTCP/DCPA molar ratios of 1/1, 1/2, or 1/3, with the powder and water as the liquid. Diametral tensile strength (DTS), porosity, and phase composition (powder x-ray diffraction) were determined after the set specimens have been immersed in a physiological-like solution (PLS) for 1 d, 5 d, and 10 d. Cement dissolution rates in an acidified PLS were measured using a dual constant composition method. Setting times ((30 ± 1) min) were the same for all cements. DTS decreased with decreasing TTCP/DCPA ratio and, in some cases, also decreased with PLS immersion time. Porosity and hydroxyapatite (HA) formation increased with PLS immersion time. Cements with TTCP/DCPA ratios of 1/2 and 1/3, which formed calcium-deficient HA, dissolved more rapidly than the cement with a ratio of 1/1. In conclusion, cements may be prepared with a range of TTCP/DCPA ratios, and those with lower ratio had lower strengths but dissolved more rapidly in acidified PLS. PMID:19779581

Hirayama, Satoshi; Takagi, Shozo; Markovic, Milenko; Chow, Laurence C



Evidence of calcium phosphate supersaturation in the loop of Henle.  


We have used published rat micropuncture data to construct a matrix of ion concentrations along the rat nephron. With an iterative computer model of known ion interactions, we calculated relative supersaturation ratios in all nephron segments. The collecting ducts and urine showed expected supersaturation with stone-forming salts. Fluid in the thin segment of the loop of Henle may be supersaturated with calcium carbonate and calcium phosphate under certain conditions. Because calculations cannot predict the actual course of crystallization, we made solutions to mimic, in vitro, presumed conditions in the loop of Henle. The solid phases that formed were analyzed by X-ray powder diffraction, electron microprobe, and infrared spectroscopy. All samples were identified as poorly crystallized or immature apatite. The descending limb of Henle's loop creates a unique condition as it extracts water but not sodium, bicarbonate, calcium, or phosphate, giving a calcium concentration at the bend of 3 mM, pH 7.4, and a phosphate concentration that varies from 0.8 to 48 mM, depending on parathyroid hormone and dietary phosphate. We conclude that conditions in the thin segment potentially could create a solid calcium phosphate phase, which may initiate nucleation of calcium oxalate salts in the collecting ducts, potentiating nephrolithiasis and nephrocalcinosis. PMID:8967338

Asplin, J R; Mandel, N S; Coe, F L



The Nucleation and growth of Calcium Phosphate by Amelogenin  

SciTech Connect

The nucleation processes involved in calcium phosphate formation in tooth enamel are not well understood but are believed to involve proteins in the extracellular matrix. The ability of one enamel protein, amelogenin, to promote the nucleation and growth of calcium phosphate was studied in an in vitro system involving metastable supersaturated solutions. It was found that recombinant amelogenin (rM179 and rp(H)M180) promoted the nucleation of calcium phosphate compared to solutions without protein. The amount of calcium phosphate increased with increasing supersaturation of the solutions and increasing protein concentrations up to 6.5 µg/ml. At higher protein concentrations, the amount of calcium phosphate decreased. The kinetics of nucleation were studied in situ and in real time using a quartz crystal microbalance (QCM) and showed that the protein reduced the induction time for nucleation compared to solutions without protein. This work shows a nucleation role for amelogenin in vitro which may be promoted by the association of amelogenin into nanosphere templates, exposing charged functionality at the surface. This research was performed at Pacific Northwest National Laboratory, operated by Battelle for the US-DOE. A portion of the research was performed in the EMSL, a national scientific user facility sponsored by the DOE-OBER at PNNL.

Tarasevich, Barbara J.; Howard, Christopher J.; Larson, Jenna L.; Snead, Malcolm L.; Simmer, Jim; Paine, Michael L.; Shaw, Wendy J.



The nucleation and growth of calcium phosphate by amelogenin  

PubMed Central

The nucleation processes involved in calcium phosphate formation in tooth enamel are not well understood but are believed to involve proteins in the extracellular matrix. The ability of one enamel protein, amelogenin, to promote the nucleation and growth of calcium phosphate was studied in an in vitro system involving metastable supersaturated solutions. It was found that recombinant amelogenin (rM179 and rp(H)M180) promoted the nucleation of calcium phosphate compared to solutions without protein. The amount of calcium phosphate increased with increasing supersaturation of the solutions and increasing protein concentrations up to 6.5 ?g/mL. At higher protein concentrations, the amount of calcium phosphate decreased. The kinetics of nucleation was studied in situ and in real time using a quartz crystal microbalance (QCM) and showed that the protein reduced the induction time for nucleation compared to solutions without protein. This work shows a nucleation role for amelogenin in vitro which may be promoted by the association of amelogenin into nanosphere templates, exposing charged functionality at the surface.

Tarasevich, Barbara J.; Howard, Christopher J.; Larson, Jenna L.; Snead, Malcolm L.; Simmer, James P.; Paine, Michael; Shaw, Wendy J.



Calcium phosphates in pharmaceutical tableting. 2. Comparison of tableting properties.  


Ten calcium phosphates suitable for direct compression (dibasic calcium phosphate dihydrate, dibasic calcium phosphate anhydrous and hydroxylapatite) were investigated with respect to their compressional behaviour. Except for Di-Cafos A all products gave tablets with sufficient to good mechanical strength. Nevertheless, there were differences between the products. All tablets prepared from the different products showed a high friability. This seems to be a problem of the calcium phosphates in general. On the other hand, the influence of magnesium stearate on the mechanical strength of the tablets was negligible for all products investigated. Moreover, a considerable effect of the particle size on the tensile strength of the tablets was found. The ejection forces and residual pressures were high in general, but critical only in the case of hydroxylapatites. Heckel plots were used to differentiate between plastic deformation and brittle fracture of the particles. In the case of calcium phosphates the slope of the Heckel plots indicated the hardness of the particles rather than their deformation behaviour. PMID:8348107

Schmidt, P C; Herzog, R



Phosphate-binding capacity of ferrihydrite versus calcium acetate in rats  

Microsoft Academic Search

Calcium salts, such as calcium carbonate and calcium acetate, are the principal compounds used as phosphate binders in patients with chronic renal failure. The dose required is three to six times the normal requirement for calcium. Use of these large doses of calcium salts in the diet can result in hypercalcemia. Other compounds have been investigated as phosphate binders with

Connie M. Weaver; Darrell G. Schulze; Louise W. Peck; Helen M. Magnusen; Berdine R. Martin; Sara E. Gruenhagen



Phosphate-bonded calcium aluminate cements  


A method is described for making a rapid-setting phosphate-bonded cementitious material. A powdered aluminous cement is mixed with an aqueous solution of ammonium phosphate. The mixture is allowed to set to form an amorphous cementitious material which also may be hydrothermally treated at a temperature of from about C. to about C. to form a crystal-containing phosphate-bonded material. Also described are the cementitious products of this method and the cement composition which includes aluminous cement and ammonium polyphosphate.

Sugama, Toshifumi (Mastic Beach, NY)



The Role of Polycarboxylic Acids in Calcium Phosphate Mineralization  

Microsoft Academic Search

The role of two polyelectrolytes, poly-L-glutamate and poly-L-aspartate, in the growth of calcium phosphate crystal phases, has been investigated at constant supersaturation. Both molecules are strong inhibitors of HAP growth when present in the solution phase but also act as hydroxyapatite and (octacalcium phosphate)-like crystal nucleators when adsorbed on germanium surfaces. The structure of the polymers in solution is presented

Achilles Tsortos; George H. Nancollas



Solubilization of inorganic calcium phosphates—Solubilization mechanisms  

Microsoft Academic Search

Two species [Penicillium aurantiogriseum and Pseudomonas sp. (PI1889)] having high abilities in solubilizing inorganic phosphates (hydroxylapatite and brushite) were used to examine solubilization mechanisms. No direct contact between microorganisms and calcium phosphates (Ca-Ps) were necessary for effective solubilization. The P-concentration in solution did not increase according to a sigmoid curve type. Therefore, sampling time is of particular importance for estimating

P. Illmer; F. Schinner



Dual-Setting Calcium Phosphate Cement Modified with Ammonium Polyacrylate  

Microsoft Academic Search

a-Tricalcium phosphate bone cement, as for- merly designed and developed by Driessens et al., consists of a powder composed by a-tricalcium phosphate (a-TCP) and hydroxyapatite (HA) seeds, and an aqueous solution of Na2HPO4 as mixing liquid. After mixing powder and liquid, a-TCP dissolves into the liquid and calcium defi- cient hydroxyapatite (CDHA), more insoluble than the former, precipitates as an

Raúl García Carrodeguas; Anselmo Ortega Boschi; Antônio Celso; Fonseca de Arruda


Fiber-enriched double-setting calcium phosphate bone cement.  


Calcium phosphate bone cements are useful in orthopedics and traumatology, their main advantages being their biocompatibility and bioactivity, which render bone tissue osteoconductive, providing in situ hardening and easy handling. However, their low mechanical strength, which, in the best of cases, is equal to the trabecular bone, and their very low toughness are disadvantages. Calcium phosphate cement compositions with mechanical properties more closely resembling those of human bone would broaden the range of applications, which is currently limited to sites subjected to low loads. This study investigated the influence of added polypropylene, nylon, and carbon fibers on the mechanical properties of double setting alpha-tricalcium phosphate-based cement, using calcium phosphate cement added to an in situ polymerizable acrylamide-based system recently developed by the authors. Although the addition of fibers was found to reduce the compression strength of the double-setting calcium phosphate cement because of increased porosity, it strongly increased the cement's toughness (J(IC)) and tensile strength. The composites developed in this work, therefore, have a potential application in shapes subjected to flexure. PMID:12734819

dos Santos, Luís Alberto; Carrodéguas, Raúl Garcia; Boschi, Anselmo Ortega; Fonseca de Arruda, Antônio Celso



The NEXAFS of biological calcium phosphates  

SciTech Connect

The absorption cross section of a number of calcium salts has been assessed at the calcium [ital L] edge by measuring the total electron yield (TEY) at the NSLS U13UA beamline. TEY was used because of distortions introduced by instrumentation when using a transmission signal. The effect of these distortions has been evaluated and is presented. The TEY signal was normalized to the incident beam using the signal from a new beam monitor which is detailed here. Comparative spectra are presented for some calcium salts associated with osteoarthritis.

Buckley, C.J.; Bellamy, S.J. (Department of Physics, King's College London, Strand, London WC2R 2LS (United Kingdom)); Zhang, X. (Department of Physics, SUNY at Stony Brook, Stony Brook, New York 11794 (United States)); Dermody, G. (Department of Physics, King's College London, Strand, London WC2R 2LS (United Kingdom)); Hulbert, S. (NSLS, Brookhaven National Lab, New York 11973 (United States))



Molecular mechanisms of crystallization impacting calcium phosphate cements  

PubMed Central

The biomineral calcium hydrogen phosphate dihydrate (CaHPO4·2H2O), known as brushite, is a malleable material that both grows and dissolves faster than most other calcium minerals, including other calcium phosphate phases, calcium carbonates and calcium oxalates. Within the body, this ready formation and dissolution can play a role in certain diseases, such as kidney stone and plaque formation. However, these same properties, along with brushite’s excellent biocompatibility, can be used to great benefit in making resorbable biomedical cements. To optimize cements, additives are commonly used to control crystallization kinetics and phase transformation. This paper describes the use of in situ scanning probe microscopy to investigate the role of several solution parameters and additives in brushite atomic step motion. Surprisingly, this work demonstrates that the activation barrier for phosphate (rather than calcium) incorporation limits growth kinetics and that additives such as magnesium, citrate and bisphosphonates each influence step motion in distinctly different ways. Our findings provide details of how, and where, molecules inhibit or accelerate kinetics. These insights have the potential to aid in designing molecules to target specific steps and to guide synergistic combinations of additives.

Giocondi, Jennifer L.; El-Dasher, Bassem S.; Nancollas, George H.; Orme, Christine A.



Calcium phosphate composite layers for surface-mediated gene transfer.  


In this review, the surface-mediated gene transfer system using calcium phosphate composite layers is described. Calcium phosphate ceramics are osteoconductive bioceramics used typically in orthopedic and dental applications. Additionally, calcium phosphate particles precipitated by a liquid-phase process have long been used as a safe and biocompatible transfection reagent in molecular biology. Recently, calcium phosphate composite layers immobilizing DNA were fabricated on the surfaces of base materials through a biomimetic process using supersaturated solutions. These composite layers possess useful characteristics of both osteoconductive bioceramics and transfection reagents; they thus provide a biocompatible surface to support cell adhesion and growth, and can stimulate the cell effectively via surface-mediated gene transfer. By modifying the fabrication conditions, physicochemical and biological properties of the composite layers can be varied. With such an approach, these composite layers can be designed to have improved affinity for cells and to exhibit increased gene transfer efficiency over that of conventional lipid transfection reagents. The composite layers with the increased gene transfer efficiency induced specific cell differentiation and tissue regeneration in vivo. These composite layers, given their good biocompatibility and the potential to control cell behavior on their surfaces, have great potential in tissue engineering applications. PMID:22343517

Oyane, Ayako; Wang, Xiupeng; Sogo, Yu; Ito, Atsuo; Tsurushima, Hideo



Agronomic effectiveness of calcium phosphate recovered from liquid swine manure  

Technology Transfer Automated Retrieval System (TEKTRAN)

A new manure treatment technology developed as an alternative to anaerobic lagoons on swine (Sus scrofa domesticus) farms includes solid-liquid separation and subsequent recovery of soluble phosphorus (P) as calcium phosphate from the wastewater. The objective was to determine the agronomic effectiv...


Bone regeneration: molecular and cellular interactions with calcium phosphate ceramics  

PubMed Central

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.

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



Calcium phosphate coating on titanium using laser and plasma spray  

Microsoft Academic Search

Though calcium phosphate (CaP) coated implants are commercially available, its acceptance is still not wide spread due to challenges related to weaker interfacial bonding between metal and ceramic, and low crystallinity of hydroxyapatite (HA). The objectives of this research are to improve interfacial strength, crystallinity, phase purity and bioactivity of CaP coated metallic implants for orthopaedic applications. The rationale is

Mangal Roy



Biomimetic calcium phosphate coatings on recombinant spider silk fibres.  


Calcium phosphate ceramic coatings, applied on surfaces of metallic and polymeric biomaterials, can improve their performance in bone repair and regeneration. Spider silk is biocompatible, strong and elastic, and hence an attractive biomaterial for applications in connective tissue repair. Recently, artificial spider silk, with mechanical and structural characteristics similar to those of native spider silk, has been produced from recombinant minispidroins. In the present study, supersaturated simulated body fluid was used to deposit calcium phosphate coatings on recombinant spider silk fibres. The mineralization process was followed in time using scanning electron microscopy equipped with an energy dispersive x-ray (EDX) detector and Raman spectroscope. Focused ion beam technology was used to produce a cross section of a coated fibre, which was further analysed by EDX. Preliminary in vitro experiments using a culture of bone marrow-derived human mesenchymal stem cells (hMSCs) on coated fibres were also performed. This study showed that recombinant spider silk fibres were successfully coated with a homogeneous and thick crystalline calcium phosphate layer. In the course of the mineralization process from modified simulated body fluid, sodium chloride crystals were first deposited on the silk surface, followed by the deposition of a calcium phosphate layer. The coated silk fibres supported the attachment and growth of hMSCs. PMID:20539057

Yang, Liang; Hedhammar, My; Blom, Tobias; Leifer, Klaus; Johansson, Jan; Habibovic, Pamela; van Blitterswijk, Clemens A



Biomimetic calcium phosphate coatings on recombinant spider silk fibres  

Microsoft Academic Search

Calcium phosphate ceramic coatings, applied on surfaces of metallic and polymeric biomaterials, can improve their performance in bone repair and regeneration. Spider silk is biocompatible, strong and elastic, and hence an attractive biomaterial for applications in connective tissue repair. Recently, artificial spider silk, with mechanical and structural characteristics similar to those of native spider silk, has been produced from recombinant

Liang Yang; My Hedhammar; Tobias Blom; Klaus Leifer; Jan Johansson; Pamela Habibovic; Clemens A. van Blitterswijk



Calcium phosphate cements: Competitive drug carriers for the musculoskeletal system?  

Microsoft Academic Search

This paper attempts to provide an insight in the application of calcium phosphate cements (CPC) in the field of drug delivery devices for the musculoskeletal system. Their ability to set once implanted within the body, giving a highly microporous material, allows incorporation of many types of drugs and biologically active molecules, without losing activity and denaturalization. Additionally, by being injectable

Maria-Pau Ginebra; Tania Traykova; Josep A. Planell



Surface properties of calcium phosphate particles for self setting bone cements  

Microsoft Academic Search

Calcium phosphate cements (CPC), consist of multicomponent powder mixtures of calcium orthophosphates with grain sizes in the region of 1–20 ?m. Due to the small particle sizes surface properties as the zeta potential and adsorption processes play a significant role during manufacturing and application. In the context of this work zeta potentials of different calcium phosphates, like dicalcium phosphate anhydride

U. Gbureck; J. Probst; R. Thull



Polymeric calcium phosphate cements: analysis of reaction products and properties.  


Chemical and mechanical properties of water-based polymeric calcium phosphate cements (PCPC) were investigated. These cements were derived from mixing several types of water-soluble polymers, e.g., gelatin, poly(vinyl alcohol) (PVA), and poly(alkenoic acids) such as poly(acrylic acid), with a calcium phosphate cement (CPC) mixture consisting of equimolar amounts of tetracalcium phosphate (TTCP) and anhydrous dicalcium phosphate (DCPA) as well as several other TTCP-containing mixtures. Cement formation was observed with all of the PCPCs. With the gelatin and PVA cements, significant amounts of hydroxyapatite (HA) formation were observed within 24 h. Their setting times and mechanical properties were similar to those of the purely inorganic CPC that is derived from the reaction of TTCP and DCPA in water. Although the mechanical properties of a gelatin-CPC cement were only slightly improved, its handling characteristics were superior to that of CPC. Significantly faster setting and stronger cements were obtained using polycarboxylic acid polymers with CPC. However, only small amounts of HA were observed in these types of polymeric cements even after 1 mon storage in distilled water at 37 degrees C. This research demonstrates the feasibility of preparing several new types of dental cements based on the interaction of water-soluble polymers with a self-setting calcium phosphate powder mixture. PMID:8299869

Miyazaki, K; Horibe, T; Antonucci, J M; Takagi, S; Chow, L C



Compression behaviour of biphasic calcium phosphate and biphasic calcium phosphate-agarose scaffolds for bone regeneration.  


There is an acknowledged need for shaping 3-D scaffolds with adequate porosity and mechanical properties for biomedical applications. The mechanical properties under static and cyclic compressive testing of dense and designed porous architecture bioceramic scaffolds based on the biphasic calcium phosphate (BCP) systems and BCP-agarose systems have been evaluated. The dense and designed porous architecture scaffolds in BCP systems exhibited a brittle behaviour. Agarose, a biocompatible and biodegradable hydrogel, has been used to shape designed architecture ceramic-agarose scaffolds following a low-temperature shaping method. Agarose conferred toughness, ductility and a rubbery consistency for strains of up to 60% of in ceramic BCP-agarose systems. This combination of ceramic and organic matrix helps to avoid the inherent brittleness of the bioceramic and enhances the compression resistance of hydrogel. The presence of mechanical hysteresis, permanent deformation after the first cycle and recovery of the master monotonous curve indicate a Mullins-like effect such as that observed in carbon-filled rubber systems. We report this type of mechanical behaviour, the Mullins effect, for the first time in bioceramics and bioceramic-agarose systems. PMID:20709633

Puértolas, J A; Vadillo, J L; Sánchez-Salcedo, S; Nieto, A; Gómez-Barrena, E; Vallet-Regí, M



Behavior in simulated body fluid of calcium phosphate coatings obtained by laser ablation  

Microsoft Academic Search

Three types of calcium phosphate coatings onto titanium alloy substrates, deposited by the laser ablation technique, were immersed in a simulated body fluid in order to determine their behavior in conditions similar to the human blood plasma. Neither the hydroxyapatite coating nor the amorphous calcium phosphate coating do dissolve and the ?-tricalcium phosphate phase of the coating of ?-tricalcium phosphate

L Clèries; J. M Fernández-Pradas; J. L Morenza



Involvement of intracellular calcium in the phosphate efflux from mammalian nonmyelinated nerve fibers  

Microsoft Academic Search

Summary Phosphate efflux was measured as the fractional rate of loss of radioactivity from desheathed rabbit vagus nerves after loading with radiophosphate. The effects of strategies designed to increase intracellular calcium were investigated. At the same time, the exchangeable calcium content was measured using45Ca. Application of calcium ionophore A23187 increased phosphate efflux in the presence of external calcium in parallel

P. Jirounek; J. Vitus; G. J. Jones; W. F. Pralong; R. W. Straub



Effects of Calcium and Elevated Phosphate  

Microsoft Academic Search

A B ST R A C T Force (F) and stiffness (K)were measured in glycerinated psoas fibers at various calcium levels with 0, 10, 20, and 30 mM orthophosphate (Pi) added to the bathing solutions. The concentrations of bathing solution constituents were as follows: 110 mM potassium, 40 mM sodium, 4 mM MgATP, 10 mM total EGTA, and variable amounts



Theoretical analysis of calcium phosphate precipitation in simulated body fluid.  


The driving force and nucleation rate of calcium phosphate (Ca-P) precipitation in simulated body fluid (SBF) were analyzed based on the classical crystallization theory. SBF supersaturation with respect to hydroxyapatite (HA), octacalcium phosphate (OCP) and dicalcium phosphate (DCPD) was carefully calculated, considering all the association/dissociation reactions of related ion groups in SBF. The nucleation rates of Ca-P were calculated based on a kinetics model of heterogeneous nucleation. The analysis indicates that the nucleation rate of OCP is substantially higher than that of HA, while HA is most thermodynamically stable in SBF. The difference in nucleation rates between HA and OCP reduces with increasing pH in SBF. The HA nucleation rate is comparable with that of OCP when the pH value approaches 10. DCPD precipitation is thermodynamically impossible in normal SBF, unless calcium and phosphate ion concentrations of SBF increase. In such case, DCPD precipitation is the most likely because of its highest nucleation rates among Ca-P phases. We examined the influences of different SBF recipes, interfacial energies, contact angle and molecular volumes, and found that the parameter variations do not have significant impacts on analysis results. The effects of carbonate incorporation and calcium deficiency in HA were also estimated with available data. Generally, such apatite precipitations are more kinetically favorable than HA. PMID:15451629

Lu, Xiong; Leng, Yang



Comparative chemistry of amorphous and apatitic calcium phosphate preparations  

Microsoft Academic Search

Unwashed samples of amorphous calcium phosphate (ACP) contain an irreplaceable labile fraction, rich in acid phosphate and low in Ca\\/P ratio, which is irreversibly lost during the washing process. Native ACP precipitated in the pH range 6.6–10.6 varied in Ca\\/P molar ratio from 1.18 to 1.50 and in HPO42?\\/total P from 33.0% to 10.1%. At pH 7.40, native ACP had

J. D. Termine; E. D. Eanes



Formation of a calcium phosphate-rich layer on absorbable calcium carbonate bone graft substitutes  

Microsoft Academic Search

The use of natural coral as a bone graft substitute is common in Europe. However, the bone-coral bonding mechanism remains elusive. A rat subcutaneous model was used to demonstrate changes at the surface of resorbable calcium carbonate in the form of natural coral. Histological results indicated in vivo formation of a calcium phosphate (CaP)-rich layer on the surface of the

C. J. Damien; J. L. Ricci; P. Christel; H. Alexander; J.-L. Patat



Transmission electron microscopic study on setting mechanism of tetracalcium phosphate/dicalcium phosphate anhydrous-based calcium phosphate cement.  


This work studied transmission electron microscopy on the setting mechanism of tetracalcium phosphate/dicalcium phosphate anhydrous (TTCP/DCPA)-based calcium phosphate cement. The results suggest the process for early-stage apatite formation as the follows: when TTCP and DCPA powders are mixed in the phosphate-containing solution, the TTCP powder is quickly dissolved because of its higher solubility in the acidic solution. The dissolved calcium and phosphate ions, along with those ions readily in the solution, are then precipitated predominantly on the surface of DCPA particles. Few apatite crystals were observed on the surface of TTCP powder. During the later stages of reaction, the extensive growth of apatite crystals/whiskers, with a calcium/phosphorous ratio very close to that of hydroxyapatite, effectively linked DCPA particles together and also bridged the larger TTCP particles. It is suggested that, when the large TTCP particles are locked in place by the bridging apatite crystals/whiskers, the CPC is set and would not dissolve when immersed in Hanks' solution after 20-40 min of reaction. PMID:12601778

Chen, Wen-Cheng; Lin, Jiin-Huey Chern; Ju, Chien-Ping



Calcium phosphate-based composites as injectable bone substitute materials.  


A major weakness of current orthopedic implant materials, for instance sintered hydroxyapatite (HA), is that they exist as a hardened form, requiring the surgeon to fit the surgical site around an implant to the desired shape. This can cause an increase in bone loss, trauma to the surrounding tissue, and longer surgical time. A convenient alternative to harden bone filling materials are injectable bone substitutes (IBS). In this article, recent progress in the development and application of calcium phosphate (CP)-based composites use as IBS is reviewed. CP materials have been used widely for bone replacement because of their similarity to the mineral component of bone. The main limitation of bulk CP materials is their brittle nature and poor mechanical properties. There is significant effort to reinforce or improve the mechanical properties and injectability of calcium phosphate cement (CPC) and this review resumes different alternatives presented in this specialized literature. PMID:20336722

Low, Kah Ling; Tan, Soon Huat; Zein, Sharif Hussein Sharif; Roether, Judith A; Mouriño, Viviana; Boccaccini, Aldo R



Photophysics of Cy3Encapsulated Calcium Phosphate Nanoparticles  

Microsoft Academic Search

ABSTRACT Progress toward clinical application of biodegradable fluorescent calcium phosphate (CP) nanoparticles as a bioimaging agent requires detailed knowledge of chromophore interaction with CP. As readouts of this cargo-matrix interaction, we determined the principle photophysical properties of Cy3 encapsulated in CP nanparticles (CPNPs) using steady-state and time-resolved fluorescence spectroscopy. Fluorescence correlation spectroscopy (FCS)-determined diffusion coefficients and associated hydrodynamic radii confirmed

Hari S. Muddana; Thomas T. Morgan; James H. Adair; Peter J. Butler



Silver-doped calcium phosphate nanopowders prepared by electrostatic spraying  

Microsoft Academic Search

Silver-doped calcium phosphate nanopowders were successfully prepared by the cost-effective electrostatic spray-pyrolysis\\u000a process. The properties of the silver-doped nanopowder annealed at 500°C for 30 min were investigated through X-ray diffraction\\u000a analysis, field emission scanning electron microscope, and Fourier transform infrared spectroscopy. The silver-doped nanopowders\\u000a with 70–90 nm particle size showed an antibacterial performance against Escherichia coli.

Kyu-Seog Hwang; Seung Hwangbo; Jin-Tae Kim



Fluoride and Casein Phosphopeptide-Amorphous Calcium Phosphate  

Microsoft Academic Search

Casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) slows the progression of caries and remineralizes enamel subsurface lesions. The aim of this study was to determine the ability of CPP-ACP to increase the incorporation of fluoride into plaque and to promote enamel remineralization in situ. Randomized, double-blind, cross-over studies involved mouthrinses and dentifrices containing CPP-ACP and fluoride. The mouthrinses were used for 60

E. C. Reynolds; F. Cai; N. J. Cochrane; P. Shen; G. D. Walker; M. V. Morgan; C. Reynolds



Composites of Calcium Phosphate and Polymers as Bone Substitution Materials  

Microsoft Academic Search

The state of the art of calcium phosphate\\/polymer composites for bone substitution is reviewed. Many combinations are possible\\u000a which were proposed to improve the mechanical properties and the biocompatibility. However, the way from the laboratory to\\u000a the clinical application is long, and potential candidates for new bone substitution materials have to meet many different\\u000a requirements.

Markus Neumann; Matthias Epple



Calcium and phosphate homeostasis: concerted interplay of new regulators  

Microsoft Academic Search

Calcium (Ca(2+)) and phosphate (P(i)) are essential to many vital physiological processes. Consequently the maintenance of Ca(2+) and P(i) homeostasis is essential to a healthy existence. This occurs through the concerted action of intestinal, renal, and skeletal regulatory mechanisms. Ca(2+) and P(i) handling by these organs is under tight hormonal control. Disturbances in their homeostasis have been linked to pathophysiological

Kirsten Y. Renkema; R. Todd Alexander; René J. Bindels; Joost G. Hoenderop



Coprecipitation of phosphate with calcium carbonate in Lake Veluwe  

Microsoft Academic Search

Coprecipitation of dissolved phosphate with calcite (CaCO3) has been observed in many lakes. In 1979\\/1980 white flocks occurred in Lake Veluwe after the inlet of water with a high calcium content. A high oversaturation with respect to calcite occurred at that time, presently (1985–1987) the oversaturation is much smaller. The intense photosynthesis decreased and maximum summer pH values came down

Heleen J. Danen-Louwerse; Lambertus Lijklema; Monique Coenraats



In–vitro calcium phosphate growth over functionalized cotton fibers  

Microsoft Academic Search

Biomimetic growth of calcium phosphate compound on cotton sheets treated with tetraethoxy silane and soaked in simulated body fluid solution was studied using scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), micro-Fourier transform infrared spectroscopy (FTIR) and X-ray diffractometry (XRD). Micro-FTIR and EDAX results show that silicon was coupled to the cotton fiber when cotton was treated with tetra-ethoxy

H. K. Varma; Y. Yokogawa; F. F. Espinosa; Y. Kawamoto; K. Nishizawa; F. Nagata; T. Kameyama



Fourier transform raman spectroscopy of synthetic and biological calcium phosphates  

Microsoft Academic Search

Fourier-transform (FT) Raman spectroscopy was used to characterize the organic and mineral components of biological and synthetic calcium phosphate minerals. Raman spectroscopy provides information on biological minerals that is complimentary to more widely used infrared methodologies as some infrared-inactive vibrational modes are Raman-active. The application of FT-Raman technology has, for the first time, enabled the problems of high sample fluorescence

G. R. Sauer; W. B. Zunic; J. R. Durig; R. E. Wuthier



Amorphous calcium silicate as a chemisorbent for phosphate  

Microsoft Academic Search

Amorphous calcium silicate (ACS), a novel silicate material developed as filler for use in paper manufacture, has shown an affinity for the chemisorption of orthophosphate from an aqueous solution obeying a Freundlich isotherm. Removal efficiencies of up to 100% were achieved at environmental- and waste-scale concentrations of phosphate of between 0.01 and 100 mg P l?1. Chemisorption studies indicated loadings

D. C. Southam; T. W. Lewis; A. J. McFarlane; J. H. Johnston



Iodine measurement in porous matrices based on calcium phosphate compounds  

Microsoft Academic Search

Porous ceramic materials based on calcium phosphate compounds (CFC) have been studied and developed for several biomedical\\u000a applications such as implants, controlled drug delivery, and radioactive sources for brachytherapy. Two kinds of hydroxyapatite\\u000a (HAp) powders and their ceramic bodies were characterized. In this study, non-radioactive iodine was incorporated in two types\\u000a of biodegradable hydroxyapatite-based porous matrices (HA and HACL). The

K. A. Lacerda; F. S. Lameiras; V. V. Silva



In vivo evaluation of an injectable Macroporous Calcium Phosphate Cement  

Microsoft Academic Search

Although Calcium Phosphate Cements (CPC) are highly biocompatible and osteconductive materials, its resorption rate still\\u000a remains too slow for some applications. In this work the introduction of Macroporosity in an injectable CPC is evaluated as\\u000a a way to accelerate resorption and to increase bone ingrowth. A Macroporous and a standard CPC were injected just after preparation\\u000a in a defect drilled

Sergio del Valle; Natalia Miño; Fernando Muñoz; Antonio González; Josep A. Planell; Maria-Pau Ginebra



Formation of silver incorporated calcium phosphate film for medical applications  

Microsoft Academic Search

Calcium phosphate coating layers were formed by electron beam evaporation of hydroxyapatite as an evaporant with and without simultaneous Ar ion bombardments. The Ca\\/P ratio of film, which determined the biological properties, was controlled by ion beam current. Without ion beam bombardments, the film had the low Ca\\/P ratio of 1.30, however, the ratio increased to 2.02 by bombarding of

In-Seop Lee; Chung-Nam Whang; Kyung-Sik Oh; Jong-Chul Park; Kwon-Yong Lee; Gun-Hwan Lee; Sung-Min Chung; Xiao-Dan Sun



Electrolytic deposition of lithium into calcium phosphate coatings  

Microsoft Academic Search

ObjectivesLithium ions stimulate the Wnt signaling pathway and the authors previously demonstrated that lithium enhances the proliferation of tissue cultured human mesenchymal stem cells. The aim of this study was to prepare and characterize a calcium phosphate\\/lithium coating by means of electrolytic deposition. It was hypothesized that the hybrid coatings would enhance the proliferation of MG63 osteoblast-like cells in vitro.

Jiawei Wang; Klaas de Groot; Clemens van Blitterswijk; Jan de Boer



Development of magnesium calcium phosphate biocement for bone regeneration  

PubMed Central

Magnesium calcium phosphate biocement (MCPB) with rapid-setting characteristics was fabricated by using the mixed powders of magnesium oxide (MgO) and calcium dihydrogen phosphate (Ca(H2PO4)2·H2O). The results revealed that the MCPB hardened after mixing the powders with water for about 7 min, and the compressive strength reached 43 MPa after setting for 1 h, indicating that the MCPB had a short setting time and high initial mechanical strength. After the acid–base reaction of MCPB containing MgO and Ca(H2PO4)2·H2O in a molar ratio of 2 : 1, the final hydrated products were Mg3(PO4)2 and Ca3(PO4)2. The MCPB was degradable in Tris–HCl solution and the degradation ratio was obviously higher than calcium phosphate biocement (CPB) because of its fast dissolution. The attachment and proliferation of the MG63 cells on the MCPB were significantly enhanced in comparison with CPB, and the alkaline phosphatase activity of MG63 cells on the MCPB was significantly higher than on the CPB at 7 and 14 days. The MG63 cells with normal phenotype spread well on the MCPB surfaces, and were attached in close proximity to the substrate, as seen by scanning electron microscopy (SEM). The results demonstrated that the MCPB had a good ability to support cell attachment, proliferation and differentiation, and exhibited good cytocompatibility.

Jia, Junfeng; Zhou, Huanjun; Wei, Jie; Jiang, Xin; Hua, Hong; Chen, Fangping; Wei, Shicheng; Shin, Jung-Woog; Liu, Changsheng



Single Step Sintered Calcium Phosphate Fibers from Avian EGG Shell  

NASA Astrophysics Data System (ADS)

Different forms of calcium-phosphate (Hydoxyapatite, ?-TCP, ?-TCP, CDHA) minerals are found to be major component of bone tissue. Development of calcium-phosphate (CaP) based fibrous microstructures is of significant research interest worldwide owing to its improved mechanical properties and higher interconnectivity. Here we represent a method for single step sintered wet-spun Fibers of calcium phosphate from avian egg shells for biomedical applications. Raw egg shell powder was mixed with chitosan solution and Phosphoric acid. The mixture is milled in a ball mill overnight and then filtered. The slurry was de-aired using 100 microliter 1-octanol per 100 ml of slurry as antifoaming and wet spun in coagulation bath. Fiber was dried overnight and sintered at different temperatures for microstructure and phase analysis. Both green and sintered Fibers were physico-chemical characterized by SEM, EDX, XRD, TGA, DSC, FTIR, and stereo-zoom microscopy. The fibers obtained in this procedure are found to have highly porous interconnected structures which can provide good cell adhesion and therefore can be used for bioactive scaffold making.

Dadhich, Prabhash; Das, Bodhisatwa; Dhara, Santanu



Vibrational spectroscopic characterization of new calcium phosphate bioactive coatings.  


In this work calcium phosphate (CaP) compounds with different PO(3-)(4)/HPO(2-)(4) R molar ratios in the 0.65-149 range were synthesized. In fact, all these CaPs contain different amounts of HPO(2-)(4) and PO(3-)(4) ions as well as the amorphous precursors (tricalcium phosphate and octacalcium phosphate) of hydroxyapatite deposition, which was shown by in vitro and in vivo measurements. Spectroscopical IR and Raman results showed the presence of bands whose intensity ratio can be related to the molar ratio R; in particular, the Raman I(962)/I(987) and the IR I(1035)/I(1125) intensity ratios were characterized as markers of the molar ratio. For these CaP compounds a nucleation model, which was based on the ability of HPO(2-)(4) ions to form strong H bonds with PO(3-)(4) ions, was proposed. PMID:10805911

Taddei, P; Tinti, A; Bottura, G; Bertoluzza, A



Biomimetic coprecipitation of calcium phosphate and bovine serum albumin on titanium alloy  

Microsoft Academic Search

Titanium alloy implants were precoated biomimetically with a thin and dense layer of calcium phosphate and then incubated either in a supersaturated solution of calcium phosphate or in phosphate-buffered saline, each containing bovine serum albumin (BSA) at various concentrations, under physiological conditions for 48 h. Coated implants then underwent scanning electron microscopy, immunohistochemical evaluation, Fourier transform infrared spectroscopy, and X-ray

Yuelian Liu; Pierre Layrolle; Bruijn de Joost; Blitterswijk van Clemens; Groot de Klaas



Of the in vivo behavior of calcium phosphate cements and glasses as bone substitutes  

Microsoft Academic Search

The use of injectable self-setting calcium phosphate cements or soluble glass granules represent two different strategies for bone regeneration, each with distinct advantages and potential applications. This study compares the in vivo behavior of two calcium phosphate cements and two phosphate glasses with different composition, microstructure and solubility, using autologous bone as a control, in a rabbit model. The implanted

E. S. Sanzana; M. Navarro; F. Macule; S. Suso; J. A. Planell; M. P. Ginebra



Comparison of patients with idiopathic calcium phosphate and calcium oxalate stones.  


Our primary objective was to test the hypothesis that a defect in acidification is more common in patients who have idiopathic calcium phosphate kidney stones than in those whose stones are formed mainly of calcium oxalate. Additionally, other risk factors might differ for these 2 stone types. Urine pH was measured serially over 24 hours, and along with ammonium and titratable acid, it was measured before and serially after ingestion of ammonium chloride in 3 groups of subjects: 24 patients with predominantly calcium phosphate stones, 30 patients with calcium oxalate stones, and 15 health non-stone-formers. Twenty-six parameters potentially related to stone formation and acidification were assayed on urines collected over 24 hours, and 15 parameters on blood. The data base was a computerized list of 5900 analyses of stones from patients living in Newfoundland. Patients not known by their physician to have had urinary tract infection, anatomical abnormality, hyperparathyroidism, or renal tubular acidosis were asked to participate in the study. Differences between means were considered significant if p values were less than 0.05 for F by analysis of variance and also less than 0.01 by t-test. In all patients with calcium oxalate stones and all non-stone-formers, urine acidified to pH less than 5.25, but in 8 of the 23 phosphate stone formers who completed the ammonium chloride study urine failed to acidify to pH less than 5.25. As all 8 had normal values for venous pH, total CO2, and chloride, they were considered to have incomplete renal tubular acidosis (IRTA). The 8 phosphate stone formers with IRTA had greater mean values for urine pH on all 9 specimens collected serially over 24 hours (all means greater than 6.2), and after administration of ammonium chloride (p less than 0.01), as well as lower mean values for urine titratable acid excretion (p less than 0.01), both after administration of ammonium chloride and in 24-hour urine samples, compared with the remaining phosphate stone formers whose urine acidified and the oxalate and non-stone-forming control groups. Nearly all the phosphate stone formers had 1 or more risk factors for stone formation, but with frequencies not significantly higher than those found in the oxalate group. Hypercalciuria and hypocitruria were the commonest, but increased oxalate or urate also occurred. Thus, idiopathic calcium phosphate stone formation can be associated with 1 or more of several risk factors, and, with the possible exception of those with IRTA, treatment should be similar to that given to patients with calcium oxalate stones. PMID:1956278

Gault, M H; Chafe, L L; Morgan, J M; Parfrey, P S; Harnett, J D; Walsh, E A; Prabhakaran, V M; Dow, D; Colpitts, A



Preparation and characterization of an electrodeposited calcium phosphate coating associated with a calcium alginate matrix.  


A new way of optimizing osteoconduction of biomaterials is to bring to them biological properties. In this work, we associated a novel release system with an electrodeposited calcium phosphate (CaP) coated titanium alloy Ti6Al4V. The characterization of this material was performed by means of light microscopy, scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM) and X-ray energy dispersive spectroscopy (EDXS). The electrodeposited CaP coating was a tricalcium phosphate, and the release system was composed of microcapsules entrapped in an alginate film. We observed that the alginate matrix had a close contact with the coating. An intermediate layer containing calcium and phosphorus appeared at the interface between the alginate matrix and the CaP coating. These results allowed us to conclude that the association of two techniques, i.e. electrodeposition followed by deposition of a calcium alginate matrix, led to the elaboration of a new biomaterial. PMID:15754138

Hurteaux, R; Benhayoune, H; Edwards-Levy, F; Bouthors, S; Balossier, G; Laurent-Maquin, D



Effects on whole saliva of chewing gums containing calcium phosphates.  


To evaluate chewing gums as a vehicle to increase salivary mineral saturation levels and enhance salivation, monocalcium phosphate monohydrate (MCPM) and an equimolar mixture of tetracalcium phosphate (TTCP) with dicalcium phosphate anhydrous (DCPA) were chosen as experimental chewing gum additives. Each of eight subjects chewed a commercial sugarless bubble gum (control) for 16 min or the same gum to which 5 wt% of MCPM or the TTCP-DCPM mixture had been added. The saliva samples collected every 2 min were analyzed for weight, pH, and total calcium (Ca) and phosphate (P) concentrations. Both experimental gums were found to increase significantly the Ca and P concentrations of saliva during the 16-minute period even more than with a previously evaluated gum that contained dicalcium phosphate dihydrate. The degree of saturation of tooth mineral was significantly increased by both experimental gums, with the greater increase being produced by the TTCP-DCPA gum. The MCPM gum produced a significantly greater saliva flow and a lower salivary pH than did the control and TTCP-DCPA gums. The results suggest that the experimental gums may be useful for promoting remineralization in general and for inducing salivation in xerostomic patients. PMID:8294615

Chow, L C; Takagi, S; Shern, R J; Chow, T H; Takagi, K K; Sieck, B A



Response to "Chemistry misconceptions associated with understanding calcium and phosphate homeostasis"  

NSDL National Science Digital Library

I enjoyed Dr. Cliff's "conceptual diagnostic test" regarding calcium phosphate equilibrium and was relieved that I chose the correct answers (1). Question 2 was the more difficult one, and I hesitated before almost answering it incorrectly. Dr. Cliff asks what would happen if more calcium phosphate is added to a beaker containing calcium, phosphate, and calcium phosphate "at equilibrium." His answer states the question differently: "Only 11% of the students correctly answered the conceptual diagnostic question about the addition of solid calcium phosphate to a saturated [emphasis added] solution of calcium phosphate." The question did not specify that the solution was saturated but that it was "at equilibrium." It is not simply a question about understanding "mass action." One also needs to realize that the solvent is saturated if a solid in the solvent is at equilibrium. That is an additional concept itself and, when not made explicit, might explain why only 11% of the students answered it correctly.

David S. Goldfarb (St. Vincent's Hospital, and New York University School of Medicine)



Calcium phosphate bioceramics induce mineralization modulated by proteins.  


Proteins play an important role in the process of biomineralization, which is considered the critical process of new bone formation. The calcium phosphate (Ca-P) mineralization happened on hydroxyapatite (HA), ?-tricalcium phosphate (?-TCP) and biphasic calcium phosphate (BCP) when proteins presented were investigated systematically. The results reveal that the presence of protein in the revised simulated body fluid (RSBF) did not alter the shape and crystal structure of the precipitated micro-crystals in the Ca-P layer formed on the three types of bioceramics. However, the morphology of the Ca-P precipitates was regulated but the structure of Ca-P crystal was unchanged in vivo. The presence of proteins always inhibits Ca-P mineralization in RSBF and the degree of inhibitory effect is concentration dependent. Furthermore, Protein presence can increase the possibility of HA precipitation in vitro and in vivo. The results obtained in this study can be helpful for better understanding the mechanism of biomineralization induced by the Ca-P bioceramics. PMID:23706207

Wang, Kefeng; Leng, Yang; Lu, Xiong; Ren, Fuzeng



Method of coating a substrate with a calcium phosphate compound  


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.

Gao, Yufei (Kennewick, WA); Campbell, Allison A. (Kennewick, WA)



Phase Transformation of Calcium Phosphates by Electrodeposition and Heat Treatment  

NASA Astrophysics Data System (ADS)

The effect of heat treatment on the calcium phosphate deposited on Ti-6Al-4V substrate using an electrolytic process is investigated. The calcium phosphate was deposited in a 0.04 M Ca(H2PO4)2·H2O (MCPM) solution on a Ti-6Al-4V substrate at 333 K (60 °C), 10 V, and 80 Torr for 1 hour, and calcined at various temperatures for 4 hours. The X-ray diffraction (XRD) results demonstrate that the phases are dicalcium phosphate (CaHPO4, DCPD) and hydroxyapatile [Ca(PO4)6 (OH)2, HAP] for the as-deposited samples. When the deposited sample was calcined at 873 K (600 °C) for 4 hours, the XRD results show that the transformation of DCPD to HAP occurs. Moreover, HAP converts to ?-TCP, CPP, and CaO. For the sample calcined at 1073 K (800 °C) for 4 hours, the scanning electron microscopy (SEM) micrograph reveals that the crack of the calcined sample propagates with a width of about 3 ?m. This result is due to HAP becoming decomposed and converting to ?-TCP, CPP, CaO, and H2O. The vaporization of H2O within the calcined sample promotes the crack propagation and growth.

Shih, Wei-Jen; Wang, Moo-Chin; Chang, Kuo-Ming; Wang, Cheng-Li; Wang, Szu-Hao; Li, Wang-Long; Huang, Hong-Hsin



Bioresorption behavior of tetracalcium phosphate-derived calcium phosphate cement implanted in femur of rabbits  

Microsoft Academic Search

One primary focus of the present study was to clarify the crucial resorption–location relationship of a recently developed single-phase TTCP-derived calcium phosphate cement (CPC) implanted in rabbit femur in a systematic and quantitative way. Gross examination of retrieved CPC\\/bone composite samples indicated that the CPC implant did not evoke inflammatory response, necrosis or fibrous encapsulation in surrounding bony tissues. Histological

Chih-Hung Tsai; Ruey-Mo Lin; Chien-Ping Ju; Jiin-Huey Chern Lin



Effect of strontium ions substitution on gene delivery related properties of calcium phosphate nanoparticles  

Microsoft Academic Search

Gene therapy has been considered a strategy for delivery of therapeutic nucleic acids to a specific site. Calcium phosphates\\u000a are one gene delivery vector group of interest. However, low transfection efficiency has limited the use of calcium phosphate\\u000a in gene delivery applications. Present work aims at studying the fabrication of strontium substituted calcium phosphate nanoparticles\\u000a with improved gene delivery related

A. HanifiM; M. H. Fathi; H. Mir Mohammad Sadeghi



Enamel Subsurface Lesion Remineralisation with Casein Phosphopeptide Stabilised Solutions of Calcium, Phosphate and Fluoride  

Microsoft Academic Search

Casein phosphopeptide stabilised amorphous calcium phosphate (CPP-ACP) and amorphous calcium fluoride phosphate (CPP-ACFP) solutions have been shown to remineralise enamel subsurface lesions. The aim of this study was to determine the effect of ion composition of CPP-ACP and CPP-ACFP solutions on enamel subsurface lesion remineralisation in vitro. CPP-bound and free calcium, phosphate and fluoride ion concentrations in the solutions were

N. J. Cochrane; S. Saranathan; F. Cai; K. J. Cross; E. C. Reynolds



Remineralization of Enamel Subsurface Lesions by Casein Phosphopeptide-stabilized Calcium Phosphate Solutions  

Microsoft Academic Search

Casein phosphopeptides (CPP) stabilize amorphous calcium phosphate (ACP), localize ACP in dental plaque, and are anticariogenic in animal and in situ human caries models. In this in vitro study, CPP-stabilized calcium phosphate solutions were shown to remineralize subsurface lesions in human third-molar enamel. Solutions were used to examine the effect of CPP-calcium phosphate concentration on remineralization. Other solutions were used

E. C. Reynolds



Effect of the calcium to phosphorus ratio on the setting properties of calcium phosphate bone cements.  


?-Tricalcium phosphate (?-TCP) has become the main reactant of most experimental and commercial ceramic bone cements. It has calcium-to-phosphorus (Ca/P) ratio of 1.50. The present study expands and reports on the microstructures and mechanical properties of calcium phosphate (CP) cements containing sintered monolithic reactants obtained in the interval 1.29 < Ca/P < 1.77. The study focuses on their cement setting and hardening properties as well as on their microstructure and crystal phase evolution. The results showed that: (a) CP-cements made with reactants with Ca/P ratio other than 1.50 have longer setting and lower hardening properties; (b) CP-cements reactivity was clearly affected by the Ca/P ratio of the starting reactant; (c) reactants with Ca/P < 1.50 were composed of several phases, calcium pyrophosphate and ?- and ?-TCP. Similarly, reactants with Ca/P > 1.50 were composed of ?-TCP, tetracalcium phosphate and hydroxyapatite; (d) only the reactant with Ca/P = 1.50 was monophasic and was made of ?-TCP, which transformed during the setting into calcium deficient hydroxyapatite; (e) CP-cements developed different crystal microstructures with specific features depending on the Ca/P ratio of the starting reactant. PMID:22639154

Vlad, M D; Gómez, S; Barracó, M; López, J; Fernández, E



Low temperature solution deposition of calcium phosphate coatings for orthopedic implants.  

National Technical Information Service (NTIS)

Calcium phosphate coatings were grown from aqueous solution onto a derivatized self-assembled monolayer (SAM) which was covalently bound to a titanium metal substrate. The SAM molecules provided an idea connection between the metal surface and the calcium...

A. A. Campbell G. L. Graff



Selective laser sintering of calcium phosphate materials for orthopedic implants  

NASA Astrophysics Data System (ADS)

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 control of micro and macro pore structure, to maximize bone healing and provide sufficient mechanical strength. It also permits the complete removal of the polymeric binders that are resided in the SLS process. In collaboration with the University of Texas Health Science Center at San Antonio and BioMedical Enterprises, Inc., porous implants based on anatomical geometry have been successfully implanted in rabbits and dogs. These histologic animal studies reveal excellent biocompatibility and show its great potential for commercial custom-fit implant manufacture. The second research effort involves fabrication of fully dense bone for application in dental restoration and load-bearing orthopedic functions. Calcium phosphate glass melts, proven to be biocompatible in the first effort, were cast into carbon molds. Processes were developed for preparing the molds. These carbon molds of anatomic shape can be prepared from either Computer Numerical Control (CNC) milling of slab stock or SLS processing of thermoset-coated graphite powder. The CNC milling method provides accurate dimension of the molds in a short period of time, however, the capable geometries are limited; generally two pieces of molds are required for complex shapes. The SLS method provides very complex shape green molds. However, they need to go through pyrolysis of thermoset binder to provide the high temperature capability reached at calcium phosphate melt temperatures (1100°C) and noticeable shrinkage was observed during pyrolysis. The cast glass was annealed to develop polycrystalline calcium phosphate. This process also exhibits great potential.

Lee, Goonhee


Characterization of biomimetic calcium phosphate on phosphorylated chitosan films.  


This study examined the effect of chitosan degree of deacetylation (DDA), concentration of simulated body fluid (SBF), and mineralization time on the composition, structure, and crystallinity of calcium phosphate (CaP) biomimetically deposited on chitosan and on osteoblast cell growth. Phosphorylated chitosan films of 92.3%, 87.4%, and 80.6% DDA were soaked in SBF (1.0x or 1.5x) for 7, 14, or 21 days. Scanning electron microscopy revealed that CaP precipitated from 1.5x SBF had a porous, granular morphology; while the coatings precipitated in 1.0x SBF were smoother and more uniform. X-ray diffraction showed that films mineralized in 1.0x SBF were amorphous, while films mineralized in 1.5x SBF for 21 days exhibited crystalline peaks similar to hydroxyapatite, with the most crystalline peaks seen on 92.3% DDA chitosan. When mineralized films were placed in cell media for 14 days, more calcium phosphate precipitated onto all films, and the most calcium phosphate was found on 92.3% DDA films mineralized in 1.5x SBF. After seven days of osteoblast culture, there were approximately three times as many cells (based on DNA measurements, p < 0.05) on 92.3% DDA films soaked in 1.0x SBF for seven or 21 days than on 80.6% DDA films soaked in 1.0x SBF for any length of time or any films soaked in 1.5x SBF. The DDA of chitosan, concentration of SBF and mineralization time affect the structure of and biological response to chitosan/biomimetic CaP films, and these factors must be considered when designing new materials to be used in orthopaedic and dental/craniofacial implant applications. PMID:17295230

Chesnutt, B M; Yuan, Y; Brahmandam, N; Yang, Y; Ong, J L; Haggard, W O; Bumgardner, J D



Biogenic calcium phosphate transformation in soils over millennial time scales  

Microsoft Academic Search

Background, aim, and scope  Changes in bioavailability of phosphorus (P) during pedogenesis and ecosystem development have been shown for geogenic calcium\\u000a phosphate (Ca-P). However, very little is known about long-term changes of biogenic Ca-P in soil.\\u000a \\u000a \\u000a \\u000a Materials and methods  Long-term transformation characteristics of biogenic Ca-P were examined using anthropogenic soils along a chronosequence from\\u000a centennial to millennial time scales.\\u000a \\u000a \\u000a \\u000a Results and discussion  Phosphorus

Shinjiro Sato; Eduardo G. Neves; Dawit Solomon; Biqing Liang; Johannes Lehmann



Properties of calcium phosphate powder synthesized from calcium acetate and sodium hydrophosphate  

Microsoft Academic Search

The properties of powder synthesized from calcium acetate and sodium hydrophosphate with the ratio $$ \\\\left[ {{\\\\text{C}}{{\\\\text{a}}^{{2 + }}}} \\\\right]\\/\\\\left[ {{\\\\text{PO}}_4^{3 - }} \\\\right] $$ of the starting reagents equal to 1 have been investigated. After synthesis brushite, monetite, and octacalcium phosphate\\u000a were found in the powder. A substantial mass loss, equal to 26%, on heating is due to not

T. V. Safronova; V. I. Putlyaev; A. V. Kuznetsov; N. A. Ketov; A. G. Veresov



Premixed injectable calcium phosphate cement with excellent suspension stability.  


Premixed injectable calcium phosphate cement (p-ICPC) pastes have advantages over aqueous injectable calcium phosphate cement (a-ICPC) because p-ICPC remain stable during storage and harden only after placement into the defect. This paper focused on the suspension stability of p-ICPC paste by using fumed silica as a stabilizing agent and propylene glycol (PEG) as a continuous phase. Multiple light scanning techniques were first applied to evaluate the suspension stability. The results indicated that fumed silica effectively enhanced the suspension stability of p-ICPC pastes. The stabilizing effect of fumed silica results from the network structure formed in PEG because of its thixotropy. The p-ICPC could be eventually hydrated to form hydroxyapatite under aqueous circumstances by the unique replacement between water and PEG. p-ICPC (1) not only possesses proper thixotropy and compressive strength but has good injectability as well. p-ICPC (1) was cytocompatible and had no adverse effect on the attachment and proliferation of MG-63 cells in vitro. These observations may have applicability to the development of other nonaqueous injectable biomaterials for non-immediate filling and long-term storage. PMID:23563980

Chen, Fangping; Mao, Yuhao; Liu, Changsheng



Biomimetic Calcium Phosphate Crystallization: Synchrotron X-ray Studies  

NASA Astrophysics Data System (ADS)

The nucleation and growth of calcium phosphate by organic templates attract great attention due to its relevance to bone biomineralization. In spite of the vast studies in the field, the role of the organic templates in the process is still not well understood. One reason for this drawback is the lack of experimental tools to probe the organic template structure during the process. We studied the nucleation and growth of calcium phosphate under floating Langmuir monolayers, at the air/water interface, using two complementary X-ray scattering methods. We show that Grazing Incidence X-ray Diffraction (GID) and Grazing Incidence X-ray off-Specular Scattering (GIXOS) can reveal the organic-inorganic interface properties in situ. By using GID and GIXOS together, we can simultaneously determine the lateral interface structure and the electron density profile normal to the interface. Combined with ex situ methods, these techniques can improve our understanding of the role of the organic template during biomineralization.

Uysal, Ahmet; Stripe, Benjamin; Dutta, Pulak; Lin, Binhua; Meron, Mati



Regulation of calcium phosphate formation by amelogenins under physiological conditions  

PubMed Central

Amelogenin is essential for proper enamel formation. The present in vitro study extends our previous work at low (10 mM) ionic strength (IS) by examining the effect of amelogenin on mineralization under higher (162 mM) IS conditions found in developing enamel. Full-length phosphorylated (P173) and non-phosphorylated (rP172) amelogenins were examined, along with P148 and rP147 that lack the hydrophilic C-terminus. Calcium phosphate formation was assessed by pH change, while minerals formed were characterized using transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy. Amelogenin self-assembly was also studied using dynamic light scattering and TEM. Results indicate that IS does not influence the effects of rP147, rP172 and P173 have on mineralization. However, in contrast to low IS findings, where both P173 and P148 stabilize initially formed amorphous calcium phosphate (ACP) nanoparticles for >1 d, elongated hydroxyapatite crystals were observed after 24 h using P148 at high IS, unlike that seen with P173. Differences in self-assembly help explain these findings, which suggest that P173 and P148 may play different roles in regulating enamel mineral formation. Present data support the notion that proteolytic processing of P173 is required in vivo to induce the transformation of initial ACP phases to apatitic enamel crystals.

Kwak, Seo-Young; Green, Samantha; Wiedemann-Bidlack, Felicitas B.; Beniash, Elia; Yamakoshi, Yasuo; Simmer, James P.; Margolis, Henry C.



Physical characterization of dibasic calcium phosphate dihydrate and anhydrate.  


The dehydration of different commercial brands of dibasic calcium phosphate dihydrate (DCPD; CaHPO(4).2H(2)O) was examined over a range of temperatures and water vapor pressures. To determine the main factors affecting the physical stability of DCPD, the baseline characterization of DCPD and dibasic calcium phosphate anhydrate (DCPA; CaHPO(4)) was conducted by thermogravimetric analysis, differential scanning calorimetry and X-ray diffractometry. The surface area and the DCPA content (present as an impurity) depended on the commercial source of DCPD. The larger particles contained a higher concentration of DCPA and the anhydrate exhibited a concentration-dependent acceleratory effect on the dehydration of DCPD. Unlike DCPD, DCPA is physically stable and resisted hydration even when dispersed in water for over 7 months in the temperature range of 4-50 degrees C. In dosage forms containing DCPD, there is a potential for phase transformation to DCPA, while the reverse transition, that is, DCPA --> DCPD appears to be extremely unlikely. Thus, the risk of physical transformation can be minimized by using DCPA in formulations. PMID:18563795

Miyazaki, Tamaki; Sivaprakasam, Kannan; Tantry, Jaidev; Suryanarayanan, Raj



Geometrically structured implants for cranial reconstruction made of biodegradable polyesters and calcium phosphate/calcium carbonate.  


The aim of this study was the development of a processing pathway for manufacturing of biodegradable skull implants with individual geometry. The implants on the basis of polylactide and calcium phosphate/calcium carbonate were prepared by a combination of hot pressing and gas foaming. On the inside, the implant consists of a macroporous and faster degradable material (poly(D,L-lactide)+CaCO3) to allow the ingrowth of bone cells. The pore size is in the range of 200-400 microm. On the outside, the implant consists of a compact and slower biodegradable material (poly(L-lactide) and calcium phosphate) to ensure mechanical stability and protection. To overcome problems like inflammatory reactions caused by acidic degradation products of polylactide, the polyester was combined with basic filling materials (calcium salts). The filler neutralises the lactic acid produced during polymer degradation and increases the bioactivity of the material. The stabilised pH was demonstrated by long-term in vitro pH studies. Over a time period of 250 d in demineralised water, the pH was in the physiological range. The in vitro biocompatibility was shown by cell cultures with human osteoblasts. A good proliferation of the cells was observed over the whole test period of 4 weeks. PMID:14643598

Schiller, Carsten; Rasche, Christian; Wehmöller, Michael; Beckmann, Felix; Eufinger, Harald; Epple, Matthias; Weihe, Stephan


Setting reactions and compressive strengths of calcium phosphate cements.  


Setting reactions and compressive strengths of a self-hardening calcium phosphate cement (CPC) were investigated. The CPC consists of tetracalcium phosphate (TTCP) and anhydrous dicalcium phosphate (DCPA). The cement specimens were prepared by mixing 0.7 g of the powder (TTCP 72.9 wt% + DCPA 27.1 wt%) with 0.175 mL of the liquid (25 mmol/L H3PO4 and 1.32 mmol/L sodium fluoride). The specimens were removed from the molds at pre-determined time intervals after being mixed, and their compressive strengths were measured. Immediately afterward, the fractured specimens were rapidly frozen in ethanol (-80 degrees C), lyophilized, and examined by powder x-ray diffraction and scanning electron microscopy (SEM). The results showed that (1) hydroxyapatite was the only reaction product; (2) the reaction was nearly completed within four h, during which both the reaction product and compressive strength increased linearly with time, resulting in a strong correlation between the two; and (3) fully set CPC consisted primarily of small rod-like crystals and some platy crystals. PMID:2250090

Fukase, Y; Eanes, E D; Takagi, S; Chow, L C; Brown, W E



Biocompatibility and resorption of a brushite calcium phosphate cement.  


A hydraulic calcium phosphate cement with beta-tricalcium phosphate (TCP) granules embedded in a matrix of dicalcium phosphate dihydrate (DCPD) was implanted in experimentally created defects in sheep. One type of defect consisted of a drill hole in the medial femoral condyle. The other, partial metaphyseal defect was located in the proximal aspect of the tibia plateau and was stabilized using a 3.5 mm T-plate. The bone samples of 2 animals each per group were harvested after 2, 4, 6 and 8 weeks. Samples were evaluated for cement resorption and signs of immediate reaction, such as inflammation, caused by the cement setting in situ. Differences regarding these aspects were assessed for both types of defects using macroscopical, radiological, histological and histomorphometrical evaluations. In both defects the brushite matrix was resorbed faster than the beta-TCP granules. The resorption front was followed directly by a front of new bone formation, in which residual beta-TCP granules were embedded. Cement resorption occurred through (i) extracellular liquid dissolution with cement disintegration and particle formation, and (ii) phagocytosis of the cement particles through macrophages. Signs of inflammation or immunologic response leading to delayed new bone formation were not noticed at any time. Cement degradation and new bone formation occurred slightly faster in the femur defects. PMID:15701367

Theiss, Felix; Apelt, Detlef; Brand, Bastian; Kutter, Annette; Zlinszky, Katalin; Bohner, Marc; Matter, Sandro; Frei, Christian; Auer, Joerg A; von Rechenberg, Brigitte



The effects of inorganic additives to calcium phosphate on in vitro behavior of osteoblasts and osteoclasts  

Microsoft Academic Search

This study describes a medium-throughput system based on deposition of calcium phosphate films in multi-well tissue culture plates that can be used to study the effect of inorganic additives on the behavior of osteoblasts and osteoclasts in a standardized manner. All tested elements, copper, zinc, strontium, fluoride and carbonate were homogenously deposited into calcium phosphate films in varying concentrations by

Liang Yang; Soledad Perez-Amodio; Florence Y. F. Barrère-de Groot; Vincent Everts; Clemens A. van Blitterswijk; Pamela Habibovic



Studies on the Mechanisms Underlying the Transfer of Calcium and Phosphate from Bone to Blood.  

National Technical Information Service (NTIS)

The skeleton is recognized as a crucial organ in the minute-to-minute regulation of the blood levels of calcium and phosphate. The fluxes of calcium and phosphate to and from bone greatly exceed the entry and exit of these ions occurring in the intestine ...

R. J. Brommage



Biphasic calcium phosphate concept applied to artificial bone, implant coating and injectable bone substitute  

Microsoft Academic Search

The development of calcium phosphate ceramics and other related biomaterials for bone graft involved a better control of the process of biomaterials resorption and bone substitution. The bioactive concept was developed for biphasic calcium phosphate ceramics (BCP). An optimum balance of the more stable phase of HA and more soluble TCP was obtained for controlling gradual dissolution in the body,

G. Daculsi



The flame photometric determination of calcium in phosphate, carbonate, and silicate rocks  

USGS Publications Warehouse

A flame photometric method of determining calcium in phosphate, carbonate, and silicate locks has been developed Aluminum and phosphate interference was overcome by the addition of a large excess of magnesium. The method is rapid and suitable for routine analysis Results obtained are within ?? 2% of the calcium oxide content. ?? 1957.

Kramer, H.



Preparation of tricalcium phosphate\\/calcium pyrophosphate structures via rapid prototyping  

Microsoft Academic Search

Custom made tricalcium phosphate\\/calcium pyrophosphate bone substitutes with a well-defined architecture were fabricated in\\u000a this study using 3D powder printing with tricalcium phosphate (TCP) powder and a liquid phase of phosphoric acid. The primary\\u000a formed matrix of dicalcium phosphate dihydrate (DCPD, brushite) was converted in a second step to calcium pyrophosphate (CPP)\\u000a by heat treatment in the temperature range 1,100–1,300°C.

Uwe Gbureck; Tanja Hölzel; Isabell Biermann; Jake E. Barralet; Liam M. Grover



Fabrication of calcium phosphate–calcium sulfate injectable bone substitute using hydroxy-propyl-methyl-cellulose and citric acid  

Microsoft Academic Search

In this study, an injectable bone substitute (IBS) consisting of citric acid, chitosan, and hydroxyl propyl methyl cellulose\\u000a (HPMC) as the liquid phase and tetra calcium phosphate (TTCP), dicalcium phosphate dihydrate (DCPD) and calcium sulfate dehydrate\\u000a (CSD, CaSO4·2H2O) powders as the solid phase, were fabricated. Two groups were classified based on the percent of citric acid in the liquid\\u000a phase

Van Viet Thai; Byong-Taek Lee



Studies on the mechanisms underlying the transfer of calcium and phosphate from bone to blood  

Microsoft Academic Search

The skeleton is recognized as a crucial organ in the minute-to-minute regulation of the blood levels of calcium and phosphate. The fluxes of calcium and phosphate to and from bone greatly exceed the entry and exit of these ions occurring in the intestine and kidneys. Parathyroid hormone, calcitonin, and 1,25-dihydroxyvitamin Dâ (1,25-(OH)âDâ are known to influence the transfer of calcium

Brommage; R. J. Jr



Calcium phosphate supersaturation regulates stone formation in genetic hypercalciuric stone-forming rats  

Microsoft Academic Search

Calcium phosphate supersaturation regulates stone formation in genetic hypercalciuric stone-forming rats.BackgroundHypercalciuria is the most common metabolic abnormality observed in patients with nephrolithiasis. Hypercalciuria raises urine supersaturation with respect to the solid phases of calcium oxalate and calcium phosphate, leading to an enhanced probability for nucleation and growth of crystals into clinically significant stones. However, there is little direct proof that

David A Bushinsky; Walter R Parker; John R Asplin



Urease-induced crystallizations of calcium phosphate and magnesium ammonium phosphate in synthetic urine and human urine.  


An aggregometer technique was used to study urease-induced crystallizations in synthetic urine and human urine from healthy subjects and patients with chronic spinal cord injuries. The two different phases of crystallization, calcium phosphate and magnesium ammonium phosphate, were easily evaluated with a single assay using this technique. The crystallization of calcium phosphate and magnesium ammonium phosphate varied markedly among the different urine specimens after incubation with urease. The turbidity curves from human urine were divided into four patterns. We assumed that the variations in the patterns of the turbidity curves appeared to be mainly due to differences in the composition of the urine and in the original pH, and that the calcium and magnesium concentrations were very important in the urinary constituents. PMID:9286035

Ebisuno, S; Komura, T; Yamagiwa, K; Ohkawa, T



In vivo Dentin Microhardness beneath a Calcium-Phosphate Cement  

PubMed Central

A minimally invasive caries-removal technique preserves potentially repairable, caries-affected dentin. Mineral-releasing cements may promote remineralization of soft residual dentin. This study evaluated the in vivo remineralization capacity of resin-based calcium-phosphate cement (Ca-PO4) used for indirect pulp-capping. Permanent carious and sound teeth indicated for extraction were excavated and restored either with or without the Ca-PO4 base (control), followed by adhesive restoration. Study teeth were extracted after 3 months, followed by sectioning and in vitro microhardness analysis of the cavity floor to 115-µm depth. Caries-affected dentin that received acid conditioning prior to Ca-PO4 basing showed significantly increased Knoop hardness near the cavity floor. The non-etched group presented results similar to those of the non-treated group. Acid etching prior to cement application increased microhardness of residual dentin near the interface after 3 months in situ.

Bresciani, E.; Wagner, W.C.; Navarro, M.F.L.; Dickens, S.H.; Peters, M.C.



Preparation of Mineralized Nanofibers: Collagen Fibrils Containing Calcium Phosphate  

PubMed Central

We report a straightforward, bottom-up, scalable process for preparing mineralized nanofibers. Our procedure is based on flowing feed solution, containing both inorganic cations and polymeric molecules, through a nanoporous membrane into a receiver solution with anions, which leads to the formation of mineralized nanofibers at the exit of the pores. With this strategy, we were able to achieve size control of the nanofiber diameters. We illustrate this approach by producing collagen fibrils with calcium phosphate incorporated inside the fibrils. This structure, which resembles the basic constituent of bones, assembles itself without the addition of noncollagenous proteins or their polymeric substitutes. Rheological experiments demonstrated that the stiffness of gels derived from these fibrils is enhanced by mineralization. Growth experiments of human adipose derived stem cells on these gels showed the compatibility of the fibrils in a tissue-regeneration context.

Maas, Michael; Guo, Peng; Keeney, Michael; Yang, Fan; Hsu, Tammy M.; Fuller, Gerald G.; Martin, Charles R.; Zare, Richard N.



Surface modification of biphasic calcium phosphate bioceramic powders  

NASA Astrophysics Data System (ADS)

Biphasic calcium phosphate (BCP)/poly L-lactide (PLLA) biocomposite is proven to be a promising bone graft material or scaffold for bone tissue engineering. To improve the interfacial compatibility of BCP bioceramic with biopolymer-PLLA, BCP powders were surface-modified in different condition to graft polymer groups onto the surface of the BCP powders. L-lactide and L-lactic acid (LA) oligomer were used to modify the BCP surface with stannous octanoate (Sn(Oct) 2) and stannous chloride (SnCl 2) as catalyst, respectively. Results show that the surface modification effect is obvious and the amount of grafted organic group is above 6.5 wt.%. Sn(Oct) 2 and SnCl 2 are the optimal catalysts for the surface grafting reaction of L-lactide and L-LA oligomer, respectively. The surface grafting slightly increase the particle size of BCP powders and reduce the tendency for their agglomeration.

Yang, W. Z.; Zhou, D. L.; Yin, G. F.; Li, G. D.



Effects of the SERM raloxifene on calcium and phosphate metabolism in healthy middle-aged men  

PubMed Central

Background. Sex hormones are important regulators of calcium and phosphate homeostasis. Estradiol appears to be a major determinant of bone health in the male gender. However, physiological effects of estrogens on calcium and phosphate homeostatic fluxes in men are still poorly understood. Objective. We investigated the influence of 6 weeks of the SERM raloxifene, an estrogen agonist in bone, but devoid of feminizing actions, on calcium and phosphate metabolism in healthy middle-aged men. Design. In a double-blind, randomized, placebo-controled, cross-over study, we evaluated the influence of 120 mg/day of raloxifene on calciotropic hormones levels, renal tubular reabsorption of calcium and phosphate, and intestinal calcium absorption, as assessed by the calciuric response to an oral calcium load. Results. As compared to the placebo period, raloxifene treatment decreased the response to an oral calcium load, together with a decrease in 1,25(OH)2D3 and in IGF-I serum levels. Maximal renal tubular phosphate reabsorption was decreased in raloxifene-treated men following the calcium load. The renal handling of calcium was not changed. Conclusion. These results are compatible with the hypothesis that raloxifene is associated with lower IGF-I and 1,25(OH)2D3 levels, with consequently reduced intestinal calcium absorption capacity.

Uebelhart, Brigitte; Herrmann, Francois; Rizzoli, Rene



[Preparation and properties of medical calcium phosphate cement].  


The preparation of tetracalcium phosphate (Ca4(PO4)2O, TTCP)was studied. Then calcium phosphate cement (CPC) was prepared. The setting time, pH value, compressive strength, X-ray diffraction (XRD) and scanning electron microscope (SEM) analysis of CPC were studied. The results show that TTCP containing small amount of CaO can be successfully attained heated at 1 500 degrees C for 6 h in vacuum condition. The initial setting time and final setting time of CPC is 4 min and 15 min, respectively. Its compressive strength is 20 MPa after 1-day immersion and 35 MPa after 7-day immersion. The pH value of the solution changes between 6.4 and 8.9. These properties can satisfy the clinical requirements of CPC. The final product of CPC is flake-like or needle-like hydroxyapatite (Ca5(P04)3OH, HA). The continuous network structure of HA appears in the microstructure, this leads to increase the strength of the material. This CPC can be used as bone substitute material. PMID:17121352

Zheng, Zhi; Xiang, Qijun; Liu, Yong; Su, Zhean; Wang, Jianlong; Xiao, Fei



Influence of solution concentration on controlled crystallization of calcium phosphate  

NASA Astrophysics Data System (ADS)

To investigate the influence of solution concentration on controlled crystallization of calcium phosphate, controlled crystallization in the presence of stearic acid monolayer from solutions of hydroxyapatite with different [Ca2+] have been studied by SEM, TEM with ED, IR, XRD. When [Ca2+] is 0.4 mM, octacalcium phosphate (OCP) which is a thermodynamically undersaturated phase in this condition precipitates due to the 'concentration effect' of charged headgroup -COO- of stearic monolayer to Ca2+ in the solution; while solution is supersaturated in which [Ca2+] is 4 mM, the first precipitates phase is hydroxyapatite (HAP) with (0001) parallel to the surface of stearic monolayer. Subsequent growth results in oriented OCP crystals, and all the crystals show a white semi- globular characters; while [Ca2+] is up to 5 mM, the increasing of mineralization rate results to the rapid nucleation of HAP into some core-like structure and the later growth of platelet-like OCP as the 'shell.' Nucleation of DCPD between OCP showing a flower-like structure also found at LB film/solution interface. The mechanism of influence of concentration was discussed.

Ma, C. L.; Qian, F.; Lu, H. B.



The thermophysical properties of calcium and barium zirconium phosphate  

NASA Astrophysics Data System (ADS)

The thermophysical and structural properties of calcium and barium zirconium phosphate ceramics (CZP and BZP) have been investigated for their potential candidacy as actinide hosts for inert matrix fuels (IMF) in nuclear reactors. These phosphate ceramics, which can accommodate minor actinides as well as the resulting fission products, are found to be thermally stable to 1600 °C in air, however they begin to decompose in an inert atmosphere above approximately 1400 °C. The heat capacity, thermal conductivity and bulk thermal-expansion were measured from room temperature up to 1200 °C. Structural changes in this temperature region as well as the anisotropic thermal-expansion behaviour were studied using high-temperature X-ray diffraction. A phase change from R-3 to R-3c was identified for Ba0.5Zr2(PO4)3 near 880 °C. The thermal conductivity for these ceramics at 1000 °C was found to be 1.0 W m-1 K-1, a relatively low thermal conductivity that was increased to 5.0 W m-1 K-1 at 1000 °C for BZP:Ni (25:75 mass ratio) cermet composites.

Gregg, Daniel J.; Karatchevtseva, Inna; Triani, Gerry; Lumpkin, Gregory R.; Vance, Eric R.



Studies on the role of calcium phosphate in the process of calcium oxalate crystal formation  

Microsoft Academic Search

Crystals of calcium phosphate (CaP) added to solutions with a composition corresponding to that at different levels of the\\u000a collecting duct (CD) and with different pH were rapidly dissolved at pH 5.0, 5.25 and 5.5. Only minor or no dissolution was\\u000a observed at higher pH levels. Despite this effect, CaP crystals induced nucleation or heterogeneous crystallization of CaOx\\u000a up to

Hans-Göran Tiselius; Bengt Lindbäck; Anne-Marie Fornander; Mari-Anne Nilsson



Investigating calcium polyphosphate addition to a conventional calcium phosphate cement for bone-interfacing applications  

NASA Astrophysics Data System (ADS)

Calcium phosphate cements (CPCs) are of great interest in bone regeneration applications because of their biocompatibility and osteoconductivity, and as delivery vehicles for therapeutics; however, delivery applications have been limited by adverse interactions between therapeutics and the cement setting reaction. Amorphous calcium polyphosphate (CPP) yields a biodegradable material with a demonstrated drug delivery capacity following appropriate processing. The incorporation of drug-loaded CPP into a CPC is under consideration as a method of minimizing adverse interactions and extending drug release. This thesis represents the first investigation into the effects of CPP addition on the properties, setting and antibiotic release profile of a conventional apatitic calcium phosphate cement. As-made, gelled and vancomycin-loaded CPP particulate were added to the powder component of a conventional dicalcium phosphate/tetracalcium phosphate CPC. The setting behaviour, set properties and microstructure of the resulting CPP-CPCs were evaluated with setting time testing (Gilmore needle method), pH testing, mechanical testing, SEM imaging, XRD and FTIR analysis. In vitro degradation and elution behaviour were evaluated by monitoring calcium release (atomic absorbance spectroscopy), mechanical strength and vancomycin release (UV-visual spectrophotometry). CPP addition was found to increase the setting time, reduce the mechanical strength and inhibit the conversion of the CPC starting powders to the set apatitic phase. The most likely mechanism for the observed effect of CPP addition was the adsorption of polyphosphate chains on the particle surfaces, which would inhibit the dissolution of the starting powders and the conversion of apatite precursor phases to apatite, leading to reduced mechanical properties. The detrimental effects of CPP were reduced by limiting the CPP fraction to less than a few weight per cent and increasing the size of the CPP particulate. CPP-containing CPCs were found to degrade more rapidly than the CPP-free controls. The ability of drug-loaded CPP to minimize adverse interactions between drug and cement could not be determined because of the adverse effect of CPP itself and the low vancomycin loads studied, but there was evidence that vancomycin release from apatitic CPCs could be extended through the use of loaded CPP.

Krausher, Jennifer Lynn


Polymeric additives to enhance the functional properties of calcium phosphate cements.  


The vast majority of materials used in bone tissue engineering and regenerative medicine are based on calcium phosphates due to their similarity with the mineral phase of natural bone. Among them, calcium phosphate cements, which are composed of a powder and a liquid that are mixed to obtain a moldable paste, are widely used. These calcium phosphate cement pastes can be injected using minimally invasive surgery and adapt to the shape of the defect, resulting in an entangled network of calcium phosphate crystals. Adding an organic phase to the calcium phosphate cement formulation is a very powerful strategy to enhance some of the properties of these materials. Adding some water-soluble biocompatible polymers in the calcium phosphate cement liquid or powder phase improves physicochemical and mechanical properties, such as injectability, cohesion, and toughness. Moreover, adding specific polymers can enhance the biological response and the resorption rate of the material. The goal of this study is to overview the most relevant advances in this field, focusing on the different types of polymers that have been used to enhance specific calcium phosphate cement properties. PMID:22511991

Perez, Roman A; Kim, Hae-Won; Ginebra, Maria-Pau



An efficient calcium phosphate nanoparticle-based nonviral vector for gene delivery  

PubMed Central

Background: Smaller nanoparticles facilitate the delivery of DNA into cells through endocytosis and improve transfection efficiency. The aim of this study was to determine whether protamine sulfate-coated calcium phosphate (PS-CaP) could stabilize particle size and enhance transfection efficiency. Methods: pEGFP-C1 green fluorescence protein was employed as an indicator of transfection efficiency. Atomic force microscopy was used to evaluate the morphology and the size of the particles, and an MTT assay was introduced to detect cell viability and inhibition. The classical calcium phosphate method was used as the control. Results: Atomic force microscopy images showed that the PS-CaP were much smaller than classical calcium phosphate particles. In 293 FT, HEK 293, and NIH 3T3 cells, the transfection efficiency of PS-CaP was higher than for the classical calcium phosphate particles. The difference in efficiencies implies that the smaller nanoparticles may promote the delivery of DNA into cells through endocytosis and could improve transfection efficiency. In addition, PS-CaP could be used to transfect HEK 293 cells after one week of storage at 4°C with a lesser extent of efficiency loss compared with classical calcium phosphate, indicating that protamine sulfate may increase the stability of calcium phosphate nanoparticles. The cell viability inhibition assay indicated that both nanoparticles show similar low cell toxicity. Conclusion: PS-CaP can be used as a better nonviral transfection vector compared with classical calcium phosphate.

Liu, Yachun; Wang, Tao; He, Fangli; Liu, Qian; Zhang, Dexi; Xiang, Shuanglin; Su, Shengpei; Zhang, Jian



Long-Term (6 Months) Cross-Over Comparison of Calcium Acetate with Calcium Carbonate as Phosphate Binder  

Microsoft Academic Search

A previous short-term study of 10 weeks in 8 patients had shown us that with half the dose of elemental calcium, calcium acetate (CaAc) could control predialysis plasma phosphate (PPO4) as well as calcium carbonate (CaCO3) but that the incidence of hypercalcemia was not decreased. To better appreciate the value of CaAc in comparison to CaCO3, CaAc was given to

F. Ben Hamida; I. El Esper; M. Compagnon; Ph. Morinière; A. Fournier



Inorganic-organic hybrid nanoparticles with biocompatible calcium phosphate thin shells for fluorescence enhancement.  


Polymeric micelles consisting of asymmetric triblock copolymers were successfully used for fabrication of robust hybrid nanoparticles with highly biocompatible calcium phosphate shells. The hydrophobic polystyrene core encapsulates hydrophobic fluorescent dyes such as Nile red. The anionic polyacrylic acid provides the site for the mineralization reaction of calcium phosphate. The polyethylene glycol corona stabilizes the hybrid nanoparticles. Fluorescent dyes can be used as imaging agents for determining the location of the nanoparticles and to give an observable indication of drug delivery, while the calcium phosphate shell can enhance the fluorescence of the encapsulated dye. PMID:23526653

Bastakoti, Bishnu Prasad; Hsu, Yin-Chu; Liao, Shih-Hsiang; Wu, Kevin C-W; Inoue, Masamichi; Yusa, Shin-ichi; Nakashima, Kenichi; Yamauchi, Yusuke



Low temperature solution deposition of calcium phosphate coatings for orthopedic implants  

SciTech Connect

Calcium phosphate coatings were grown from aqueous solution onto a derivatized self-assmebled monolayer (SAM) which was covalently bound to a titanium metal substrate. The SAM molecules provided an idea connection between the metal surface and the calcium phosphate coating. The trichlorosilane terminus of the SAM molecule insured covalent attachment to the surface, while the functionalized ``tail`` induced heterogeneous nucleation of the calcium phosphate coating from supersaturated solutions. This low temperature process allowed for uniform coatings to be produced onto complex-shaped and/or microporous surfaces and provided better control of phase purity.

Campbell, A.A.; Graff, G.L.



Injectable and rapid-setting calcium phosphate bone cement with dicalcium phosphate dihydrate.  


Calcium phosphate cement (CPC) sets in situ with intimate adaptation to the contours of defect surfaces, and forms an implant having a structure and composition similar to hydroxyapatite, the putative mineral in teeth and bones. The objective of the present study was to develop an injectable CPC using dicalcium phosphate dihydrate (DCPD) with a high solubility for rapid setting. Two agents were incorporated to impart injectability and fast-hardening to the cement: a hardening accelerator (sodium phosphate) and a gelling agent (hydroxypropyl methylcellulose, HPMC). The cement with DCPD was designated as CPC(D), and the conventional cement was referred to as CPC(A). Using water without sodium phosphate, CPC(A) had a setting time of 82 +/- 6 min. In contrast, CPC(D) exhibited rapid setting with a time of 17 +/- 1 min. At 0.2 mol/L sodium phosphate, setting time for CPC(D) was 15 +/- 1 min, significantly faster than 40 +/- 2 min for CPC(A) (Tukey's at 0.95). Sodium phosphate decreased the paste injectability (measured as the paste mass extruded from the syringe divided by the original paste mass inside the syringe). However, the addition of HPMC dramatically increased the paste injectability. For CPC(D), the injectability was increased from 65% +/- 12% without HPMC to 98% +/- 1% with 1% HPMC. Injectability of CPC(A) was also doubled to 99% +/- 1%. The injectable and rapid-setting CPC(D) possessed flexural strength and elastic modulus values overlapping the reported values for sintered porous hydroxyapatite implants and cancellous bone. In summary, the rapid setting and relatively high strength and elastic modulus of CPC(D) should help the graft to quickly attain strength and geometrical integrity within a short period of time postoperatively. Furthermore, the injectability of CPC(D) may have potential for procedures involving defects with limited accessibility or narrow cavities, when there is a need for precise placement of the paste, and when using minimally invasive surgical techniques. PMID:16184538

Burguera, Elena F; Xu, Hockin H K; Weir, Michael D



Ethoxylated bisphenol dimethacrylate-based amorphous calcium phosphate composites.  


Improving the anti-demineralizing/remineralizing and mechanical properties of amorphous calcium phosphate (ACP) composites has been the focus of our recent research. In this study, an ethoxylated bisphenol A dimethacrylate (EBPADMA) was blended with triethylene glycol dimethacrylate (TEGDMA), 2-hydroxyethyl methacrylate (HEMA) and methacryloxyethyl phthalate (MEP) to form experimental resins with different EBPADMA/TEGDMA molar ratios (0.50, 0.85 and 1.35) and a constant HEMA/MEP molar ratio (8.26). Composites were prepared by admixture of either unmilled or milled zirconia-ACP filler (40% by mass) and photo-activated resin (60% by mass). One aim was to test if improved ion release can be achieved by elevating the EBPADMA/TEGDMA ratio while lowering the level of surface active methacryloxyethyl phthalate in the resin without adversely affecting the biaxial flexure strength (BFS), degree of vinyl conversion (DC) and water sorption (WS) of composites. A second aim was to assess the effect of using milled vs. unmilled ACP on these properties. Ion release of all composites was significantly above the theoretical minimum necessary for remineralization. Calcium ion release was not impeded by binding with the carboxylic acid groups of MEP. Increased supersaturation was attained with increasing EBPADMA/TEGDMA ratio in the resin. Variations in resin composition had no effect on BFS or DC of composites. The BFS of the milled ACP composites was higher than the BFS of unmilled ACP composites (56% and 79%, respectively for dry and wet specimens). DC of composites was only moderately reduced (13.6% and 7.3%, for unmilled and milled ACP, respectively) compared to unfilled resins. WS decreased in the following order: unmilled ACP composites>milled ACP composites>copolymers. Fine-tuning of the resin and utilizing milled ACP filler improved the remineralizing potential of ACP composites without impeding their DC, BFS or WS. PMID:16701862

Skrtic, Drago; Antonucci, Joseph M; Liu, Da-Wei



TEM studies of calcium phosphates for the understanding of biomineralization  

NASA Astrophysics Data System (ADS)

Calcium phosphate (Ca-P) formation and bone minerals have been the focus of research for several decades because achievements in these areas could provide valuable insights into the understanding of biomineralization. In this thesis work, Ca-P formation, octacalcium phosphate (OCP) to hydroxyapatite (HA) transformation and bone minerals were systematically studied by transmission electron microscopy (TEM) techniques. Ca-P formations on various bioceramics in simulated body fluid and in rabbit muscle sites were investigated. The bioceramics included sintered bioglass RTM, A-W glass-ceramics, HA, alpha-tricalcium phosphate (TCP), beta-TCP and HA-TCP. The comparative studies showed that OCP formation occurred on all types of bioceramic surfaces in vitro and in vivo, except on beta-TCP; however HA formation did not occur on every type of bioceramics; it less likely occurred on the surfaces of HA and alpha-TCP. These findings were contradicted to the common statements in literatures. OCP to HA transformations in vitro and in vivo were observed by high-resolution TEM (HRTEM). The in vitro transformation was induced by electron beam irradiations of in situ TEM on synthetic OCP crystals. The in vivo transformation was revealed on rod-like HA precipitates formed in dog muscle sites. Based on HRTEM examinations and image simulations, OCP/HA crystallographic orientations were determined to be OCP (010) // HA (01¯0) and OCP (001) // HA (001¯), which differed from a well known model proposed by Brown et al. The minerals of cortical bone were extracted from human tibiae and rat femurs using 10% neutral ethylenediamine tetraacetic acid (EDTA) solution. TEM examinations showed that the dominance of bone minerals was plate-like and a few were needle-like. The length of most plate-like minerals ranged from 50 to 150 nm but could be up to 200 nm. To the author's knowledge, OCP structure was for the first time, identified in a number of plate-like bone minerals by selected area electron diffraction (SAED) and HRTEM.

Xin, Renlong


Characterization of a silver-incorporated calcium phosphate film by RBS and its antimicrobial effects.  


A thin calcium phosphate film was synthesized on both commercially pure Ti and Si wafers by electron beam evaporation of hydroxyapatite as an evaporant with simultaneous Ar ion beam bombardments. Silver was introduced into an ion-beam-assisted deposition of a calcium phosphate thin film for antimicrobial effect. The amount of incorporated silver ions was controlled by immersing calcium-phosphate-coated samples in different AgNO(3) concentrations, and Rutherford backscattering spectrometry (RBS) was employed to measure the amounts of substituted silver. The higher concentration of silver in the calcium phosphate film was more effective in reducing the bacteria of Escherichia coli ATCC 8739 and Streptococcus mutans OMZ 65 on contact with respect to controls. PMID:18458466

Han, I-H; Lee, I-S; Song, J-H; Lee, M-H; Park, J-C; Lee, G-H; Sun, X-D; Chung, S-M



A randomised study to compare salivary pH, calcium, phosphate and calculus formation after using anticavity dentifrices containing Recaldent® and functionalized tri-calcium phosphate  

PubMed Central

Aims: The aim of this study was to estimate the pH of saliva, concentration of calcium and inorganic phosphate, and calculus formation before and after usage of Recaldent® (GC Tooth Mousse Plus™), Functionalized Tricalcium Phosphate (3M ESPE ClinPro™ Tooth Crème) and standard dentifrice (Colgate dental cream). Settings and Design: Randomized double-blind study. Materials and Methods: A total of 50 subjects were recruited, the subjects were assessed at their first visit, on the 21st day and on the 42nd day. At the first visit, scaling was carried out and oral hygiene instructions were given. After 21 days, the subjects were given coded dentifrices where the operator and the subjects both were unaware of the type of dentifrice. Clinical parameters assessed were Plaque index, Gingival index, and Calculus index. Salivary samples were obtained to measure calcium, phosphate levels, and pH at 21st day and 42nd day. Statistical Analysis: ANOVA test, t-test, Mann–Whitney test, Kruskal–Wallis test. Results: The mean salivary calcium level and mean salivary phosphate level were higher in Group III (functionalized tricalcium phosphate (3M ESPE ClinPro™ Tooth Creme) as compared to Group II (Recaldent® GC Tooth Mousse Plus™) and Group I (Colgate dental cream) on the 42nd day after using dentifrices, which was statistically significant. This showed that the usage of remineralizing dentifrices led to an increase in the salivary calcium, phosphate, and pH but it did not reach the level of super saturation of the ions caused by elevated pH which could lead to calculus formation. Conclusions: Thought here was a statistically significant increase in salivary calcium and phosphate level in all three groups from baseline to 42nd day, there was no calculus formation.

Sharma, Ena; Vishwanathamurthy, Ramesh Alampalli; Nadella, Manjari; Savitha, A. N.; Gundannavar, Gayatri; Hussain, M. Ahad



Adsorption of 5'-adenosine monophosphate onto precipitated calcium phosphate: Effects of inorganic polyphosphates and carbamyl phosphate  

NASA Astrophysics Data System (ADS)

In this paper it is shown that the adsorption of 5'-adenosine monophosphate (5'-AMP) onto precipitated calcium phosphate exhibits a sigmoidal profile as revealed by isotherms at 45 °C. This result indicates a cooperative behavior in the adsorption of 5'-AMP. The relationship between adsorption capacity and surface area of the sedimented matrix may be interpreted as an indication that there is a monolayer of the adsorbed nucleotide on the solid surface. The pH dependence of adsorption suggests that the negatively charged phosphoryl group of 5'-AMP interacts with a positively charged site (possibly Ca2+) on the matrix surface. The adsorption of the nucleotide is markedly decreased at pH values above 8.0. The Dixon-like plot of the effect of pH suggests an inhibitory role of hydroxyl ions in the adsorption of 5'-AMP. At pH 7.5, other anions such as pyrophosphate, tripolyphosphate and carbamyl phosphate also inhibit the adsorption of the nucleotide, probably by interacting with its adsorption site. We suggest that these phosphorylated molecules could have played a role in chemical evolution by modulating the amount of nucleotides adsorbed onto mineral surfaces. The significance of these phenomena in chemical evolution is discussed.

Hermes-Lima, Marcelo; Tessis, Ana Claudia; Vieyra, Adalberto



Calcium phosphate coating on magnesium alloy by biomimetic method: Investigation of morphology, composition and formation process  

Microsoft Academic Search

Magnesium alloy has similar mechanical properties with natural bone and can degrade via corrosion in the electrolytic environment\\u000a of the human body. Calcium phosphate has been proven to possess bioactivity and bone inductivity. In order to integrate both\\u000a advantages, calcium phosphate coating was fabricated on magnesium alloy by a biomimetic method. Supersaturated calcification\\u000a solutions (SCSs) with different Ca\\/P ratio and

Jing-xin Yang; Yan-peng Jiao; Qing-shui Yin; Yu Zhang; Tao Zhang



Electrochemistry of AISI 316L stainless steel in calcium phosphate and protein solutions  

Microsoft Academic Search

The influence of calcium phosphate and serum on the corrosion resistance of AISI 316L stainless steel in 0.9% NaCl solution was investigated. Both substances are responsible for an increase in the pitting corrosion resistance. Calcium phosphate accelerates the rate of film formation, enhances the release of iron and nickel, and retards that of chromium from a corroding surface. Proteins induce

S. R. Sousa; M. A. Barbosa



Phosphate supplementation in young men: lack of effect on calcium homeostasis and bone turnover  

Microsoft Academic Search

Objective: To examine the effect of phosphate supplements on calcium homeostasis and bone turnover in young men.Design: Study 1 was a randomised, controlled, cross-over trial of 1000 mg elemental phosphate given for one week, with a standard diet of 800 mg\\/d each of calcium and phosphorus. Study 2 was an escalating dose study of 0, 1000, 1500 and 2000 mg\\/d

A Whybro; H Jagger; M Barker; R Eastell



Transfecting mammalian cells: optimization of critical parameters affecting calcium-phosphate precipitate formation  

Microsoft Academic Search

DNA-calcium phosphate co-precipitates arise spontaneously in supersaturated solutions. Highly effective precipitates for transfection purposes, however, can be generated only in a very narrow range of physico-chemical conditions that control the initiation and growth of precipitate complexes. The concentrations of calcium and phosphate are the main factors influencing characteristics of the precipitate complex, but other parameters, such as temperature, DNA concentration

Martin Jordan; Annette Schallhorn; Florian M. Wurm



Preparation of copolymer MMA-MA-AM and its performance as inhibitor of calcium phosphate  

Microsoft Academic Search

A scale inhibiting copolymer MMA-MA-AM has been synthesized with methyl methacrylate (MMA), maleic anhydride (MA), acrylamide(AM) as monomers and ammonium persulfate as initiator. Its performance as an inhibitor of calcium phosphate scaling has been investigated by static-state method. The results showed that MMA-MA-AM performed well in anti- calcium phosphate scaling and in dispersing iron trioxide . Inhibiting efficiency was above

Ai-jiang He; Lixiu Liu; Huiling Yu



Effects of vitamin D on renal handling of calcium, magnesium, and phosphate in the hamster  

Microsoft Academic Search

Effects of vitamin D on renal handling of calcium, magnesium, and phosphate in the hamster. The effects of 1,25(OH)2D3 on the renal handling of calcium (Ca), magnesium (Mg), and phosphate (Pi) in the thyroparathyroidectomized (TPTX) hamster were studied in the presence of exogenous PTH. Clearance experiments were performed in the following groups: acutely TPTX animals (group 1), acute TPTX plus

Maria A Burnatowska; Carol A Harris; Roger A L Sutton; John F Seely; M Burnatowska-Hledin



Synergistic Effect of Phosphate and Calcium-Containing Pigments on the Corrosion Resistance of Galvanized Steel  

Microsoft Academic Search

We studied the corrosion inhibition of galvanized steel in artificial acid rain solution by chromate-free pigments containing phosphate and calcium ions. We used the methods of electrochemical impedance spectroscopy, potentiodynamic polarization, electron microscopy, and X-ray microspectrum analysis. It was established that the combination of modified zinc phosphate and ion-exchange-type calcium-containing pigment provides a significant synergistic anticorrosion effect on galvanized steel

V. I. Pokhmurs'kyi; S. B. Layon; L. M. Bilyi



In Situ Laser Coating of Calcium Phosphate on TC4 Surface for Enhancing Bioactivity  

Microsoft Academic Search

Titanium alloy has been a successful implant material owing to its excellent ratio of strength to weight, toughness, and bio-inert oxide surface. Significant progress has been made in improving the bioactivity of titanium alloy by coating its oxide surface with calcium phosphates. In the present study, in situ coating was reported on Ti6Al4V (TC4) surface with calcium phosphate (Ca-P) bioceramics

Chi DENG; Yong WANG; Ya-ping ZHANG; Jia-cheng GAO



Porous calcium phosphate cement for alveolar bone regeneration.  


The present study aimed to provide information on material degradation and subsequent alveolar bone formation, using composites consisting of calcium phosphate cement (CPC) and poly(lactic-co-glycolic) acid (PLGA) with different microsphere morphology (hollow vs dense). In addition to the plain CPC-PLGA composites, loading the microspheres with the growth factors platelet-derived growth factor (PDGF) and insulin-like growth factor (IGF) was investigated. A total of four different CPC composites were applied into one-wall mandible bone defects in beagle dogs in order to evaluate them as candidates for alveolar bone regeneration. These composites consisted of CPC and hollow or dense PLGA microspheres, with or without the addition of PDGF-IGF growth factor combination (CPC-hPLGA, CPC-dPLGA, CPC-hPLGA(GF) , CPC-dPLGA(GF) ). Histological evaluation revealed significantly more bone formation in CPC-dPLGA than in CPC-hPLGA composites. The combination PDGF-IGF enhanced bone formation in CPC-hPLGA materials, but significantly more bone formation occurred when CPC-dPLGA was used, with or without the addition of growth factors. The findings demonstrated that CPC-dPLGA composite was the biologically superior material for use as an off-the-shelf material, due to its good biocompatibility, enhanced degradability and superior bone formation. Copyright © 2012 John Wiley & Sons, Ltd. PMID:22777771

Félix Lanao, R P; Hoekstra, J W M; Wolke, J G C; Leeuwenburgh, S C G; Plachokova, A S; Boerman, O C; van den Beucken, J J J P; Jansen, J A



The physicochemical properties of the solidification of calcium phosphate cement.  


In this article, the physicochemical properties of the solidification of calcium phosphate cement (CPC) were investigated, and the components of the solidified body and the characteristics involved in the application were measured. The setting process of CPC was moderate and slightly exothermic, the heat liberation rate was slow, and the temperature increased little. At the initial stage of the hydration, the compressive strength rose linearly with time, and reached the maximum value after 4 hours. The volume was slightly shrunken by 1% during the setting process, and the total heavy metal content was below 2 ppm. The porosity of the solidified body was about 30%, which was mainly the gel pore with size below 0.1 microm. The final product of hydration was low crystalline hydroxyapatite (HAP). Its real density was 2.859 g/cm(3), which was lower than the theoretical value. This may be due to the existence of lattice defects, which will lead to a slight rise in solubility when leached in physiological saline. PMID:15015213

Liu, Changsheng; Huang, Yue; Chen, Jianguo



Mechanical properties of novel calcium phosphate-mullite biocomposites.  


Herein, the results of systematic mechanical property measurements of pressureless sintered calcium phosphate (CaP)-mullite composites are discussed. Our experimental results demonstrated how the mullite addition (upto 30 wt%) influenced hardness, elastic modulus, strength and toughness properties of the composites. In assessing each of these fundamental material properties, either a range of load or a number of complimentary techniques were used to obtain reliable measure of mechanical properties. Importantly, the results of single edge V notch beam measurements revealed that a reliable toughness value of ~1.5 MPa m(0.5) could be obtained in composites containing 20 or 30 wt% mullite. Our results clearly illustrated that a combination of elastic modulus (~80 GPa), compressive strength of more than 350 MPa, three-point flexural strength of 70-80 MPa, hardness of 4-5 GPa were achievable with the investigated composites. Such a combination of material properties, in addition to modest toughness property appeared to indicate that CaP-mullite composites could be used as a biomaterial for hard tissue replacement. PMID:21343213

Nath, Shekhar; Dubey, Ashutosh Kumar; Basu, Bikramjit



Dibasic calcium phosphate dihydrate, USP material compatibility with gamma radiation  

NASA Astrophysics Data System (ADS)

Gamma radiation is a commonly used method to reduce the microbial bioburden in compatible materials when it is applied at appropriate dose levels. Gamma irradiation kills bacteria and mold by breaking down the organism’s DNA and inhibiting cell division. The purpose of this study is to determine the radiation dosage to be used to treat Dibasic Calcium Phosphate Dihydrate, USP (DCPD) and to evaluate its physicochemical effects if any, on this material. This material will be submitted to various doses of gamma radiation that were selected based on literature review and existing regulations that demonstrate that this method is effective to reduce or eliminate microbial bioburden in natural source and synthetic materials. Analytical testing was conducted to the DCPD exposed material in order to demonstrate that gamma radiation does not alter the physicochemical properties and material still acceptable for use in the manufacture of pharmaceutical products. The results obtained through this study were satisfactory and demonstrated that the gamma irradiation dosages from 5 to 30 kGy can be applied to DCPD without altering its physicochemical properties. These are supported by the Assay test data evaluation of lots tested before and after gamma irradiation implementation that show no significant statistical difference between irradiated and non irradiated assay results. The results of this study represent an achievement for the industry since they provide as an alternative the use of Gamma irradiation technology to control the microbial growth in DCPD.

Betancourt Quiles, Maritza


RANKL delivery from calcium phosphate containing PLGA microspheres.  


Ideally, bone substitute materials would undergo cell-mediated degradation during the remodeling process of the host bone tissue while being replaced by newly formed bone. In an attempt to exploit the capacity of Receptor Activator of Nuclear factor Kappa-B Ligand (RANKL) to stimulate osteoclast-like cells formation, this study explored different loading methods for RANKL in injectable calcium phosphate cement (CPC) and the effect on release and biological activity. RANKL was loaded via the liquid phase of CPC by adsorption onto or incorporation into poly(lactic-co-glycolic acid) (PLGA) microspheres with two different morphologies (i.e., hollow and dense), which were subsequently embedded in CPC. As controls nonembedded PLGA-microspheres were used as well as plain CPC scaffolds with RANKL adsorbed onto the surface. RANKL release and activity were evaluated by Reverse Phase High-Performance Liquid Chromatography (RP-HPLC) and osteoclast-like cells formation in cell culture experiments. Results indicated that sustained release of active RANKL can be achieved upon RANKL adsorption to PLGA microspheres, whereas inactive RANKL was released from CPC-PLGA formulations with RANKL incorporated within the microspheres or within the liquid phase of the CPC. These results demonstrate that effective loading of RANKL in injectable CPC is only possible via adsorption to PLGA microspheres, which are subsequently embedded within the CPC-matrix. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 101A: 3123-3130, 2013. PMID:23529979

Félix Lanao, Rosa P; Bosco, Ruggero; Leeuwenburgh, Sander C G; Kersten-Niessen, Monique J F; Wolke, Joop G C; van den Beucken, Jeroen J J P; Jansen, John A



Calcium-phosphate-coated Oral Implants Promote Osseointegration in Osteoporosis.  


Osteoporotic conditions are anticipated to affect the osseointegration of dental implants. This study aimed to evaluate the effect of a radiofrequent magnetron-sputtered calcium phosphate (CaP) coating on dental implant integration upon installment in the femoral condyles of both healthy and osteoporotic rats. At 8 weeks post-implantation, bone volume and histomorphometric bone area were lower around non-coated implants in osteoporotic rats compared with healthy rats. Interestingly, push-out tests revealed significantly enhanced implant fixation for CaP-coated compared with non-coated implants in both osteoporotic (i.e., 2.9-fold) and healthy rats (i.e., 1.5-fold), with similar implant fixation for CaP-coated implants in osteoporotic conditions compared with that of non-coated implants in healthy conditions. Further, the presence of a CaP coating significantly increased bone-to-implant contact compared with that in non-coated implants in both osteoporotic (i.e., 1.3-fold) and healthy rats (i.e., 1.4-fold). Sequential administration of fluorochrome labels showed significantly increased bone dynamics close to CaP-coated implants at 3 weeks of implantation in osteoporotic conditions and significantly decreased bone dynamics in osteoporotic compared with healthy conditions. In conclusion, analysis of the data obtained demonstrated that dental implant modification with a thin CaP coating effectively improves osseointegration in both healthy and osteoporotic conditions. PMID:24056224

Alghamdi, H S; Cuijpers, V M J I; Wolke, J G C; van den Beucken, J J J P; Jansen, J A



Remineralization of Demineralized Enamel via Calcium Phosphate Nanocomposite  

PubMed Central

Secondary caries remains the main problem limiting the longevity of composite restorations. The objective of this study was to investigate the remineralization of demineralized human enamel in vitro via a nanocomposite containing nanoparticles of amorphous calcium phosphate (NACP). NACP were synthesized by a spray-drying technique and incorporated into a dental resin. First, caries-like subsurface enamel lesions were created via an acidic solution. Then, NACP nanocomposite or a commercial fluoride-releasing control composite was placed on the demineralized enamel, along with control enamel without a composite. These specimens were then treated with a cyclic demineralization/remineralization regimen for 30 days. Quantitative microradiography showed typical enamel subsurface demineralization before cyclic demineralization/remineralization treatment, and significant remineralization in enamel under the NACP nanocomposite after the demineralization/remineralization treatment. The NACP nanocomposite had the highest enamel remineralization (mean ± SD; n = 6) of 21.8 ± 3.7%, significantly higher than the 5.7 ± 6.9% for fluoride-releasing composite (p < 0.05). The enamel group without composite had further demineralization of ?26.1 ± 16.2%. In conclusion, a novel NACP nanocomposite was effective in remineralizing enamel lesions in vitro. Its enamel remineralization was 4-fold that of a fluoride-releasing composite control. Combined with the good mechanical and acid-neutralization properties reported earlier, the new NACP nanocomposite is promising for remineralization of demineralized tooth structures.

Weir, M.D.; Chow, L.C.; Xu, H.H.K.



Stem Cell-Calcium Phosphate Constructs for Bone Engineering  

PubMed Central

While human bone-marrow-derived mesenchymal stem cells (hBMSCs) have been investigated, human umbilical cord mesenchymal stem cells (hUCMSCs) are a relatively new cell source. Little has been reported on hUCMSC encapsulation in scaffolds for bone tissue engineering. The objective of this study was to encapsulate hBMSCs and hUCMSCs in calcium phosphate cement (CPC) scaffolds for dental, craniofacial, and orthopedic applications. Stem-cell-encapsulating CPC construct with chitosan and fiber reinforcement reached the strength of cancellous bone, which was much stronger than previous injectable carriers for cell delivery. hUCMSCs and hBMSCs inside the constructs showed excellent viability and osteo-differentiation. The encapsulated hUCMSCs synthesized nearly three-fold more bone minerals than the hBMSCs in vitro. Hence, stem-cell-encapsulating CPC-chitosan-fiber construct may be promising for dental and orthopedic applications. This study indicated that the hUCMSCs were a potent alternative to the gold-standard hBMSCs, which may have a broad impact on regenerative medicine and dental tissue engineering.

Xu, H.H.K.; Zhao, L.; Weir, M.D.



Antibacterial nanocomposite with calcium phosphate and quaternary ammonium.  


Secondary caries is a frequent reason for restoration failure, resulting from acidogenic bacteria and their biofilms. The objectives of this study were to: (1) develop a novel nanocomposite containing nanoparticles of amorphous calcium phosphate (NACP) and quaternary ammonium dimethacrylate (QADM); and (2) investigate its mechanical and antibacterial durability. A spray-drying technique yielded NACP with particle size of 116 nm. The nanocomposite contained NACP and reinforcement glass fillers, with QADM in the resin. Two commercial composites were tested as controls. Composites were inoculated with Streptococcus mutans. After 180-day water-aging, NACP+QADM nanocomposite had flexural strength and elastic modulus matching those of commercial controls (p > 0.1). NACP+QADM nanocomposite reduced the biofilm colony-forming units (CFU) by 3-fold, compared with commercial composites (p < 0.05). Metabolic activity and lactic acid production of biofilms on NACP+QADM were much less than those on commercial composites (p < 0.05). The antibacterial properties of NACP+QADM were maintained after water-aging for 30, 90, and 180 d (p > 0.05). In conclusion, the novel NACP-QADM nanocomposite greatly decreased biofilm metabolic activity, CFU, and lactic acid, while matching the load-bearing capability of commercial composites without antibacterial properties. The NACP-QADM nanocomposite with strong and durable antibacterial properties, together with its previously reported Ca-PO(4) release capability, may render it useful for caries-inhibiting restorations. PMID:22403412

Cheng, L; Weir, M D; Zhang, K; Xu, S M; Chen, Q; Zhou, X; Xu, H H K



Remineralization of demineralized enamel via calcium phosphate nanocomposite.  


Secondary caries remains the main problem limiting the longevity of composite restorations. The objective of this study was to investigate the remineralization of demineralized human enamel in vitro via a nanocomposite containing nanoparticles of amorphous calcium phosphate (NACP). NACP were synthesized by a spray-drying technique and incorporated into a dental resin. First, caries-like subsurface enamel lesions were created via an acidic solution. Then, NACP nanocomposite or a commercial fluoride-releasing control composite was placed on the demineralized enamel, along with control enamel without a composite. These specimens were then treated with a cyclic demineralization/remineralization regimen for 30 days. Quantitative microradiography showed typical enamel subsurface demineralization before cyclic demineralization/remineralization treatment, and significant remineralization in enamel under the NACP nanocomposite after the demineralization/remineralization treatment. The NACP nanocomposite had the highest enamel remineralization (mean ± SD; n = 6) of 21.8 ± 3.7%, significantly higher than the 5.7 ± 6.9% for fluoride-releasing composite (p < 0.05). The enamel group without composite had further demineralization of -26.1 ± 16.2%. In conclusion, a novel NACP nanocomposite was effective in remineralizing enamel lesions in vitro. Its enamel remineralization was 4-fold that of a fluoride-releasing composite control. Combined with the good mechanical and acid-neutralization properties reported earlier, the new NACP nanocomposite is promising for remineralization of demineralized tooth structures. PMID:22933607

Weir, M D; Chow, L C; Xu, H H K



Amelogenin-collagen interactions regulate calcium phosphate mineralization in vitro.  


Collagen and amelogenin are two major extracellular organic matrix proteins of dentin and enamel, the mineralized tissues comprising a tooth crown. They both are present at the dentin-enamel boundary (DEB), a remarkably robust interface holding dentin and enamel together. It is believed that interactions of dentin and enamel protein assemblies regulate growth and structural organization of mineral crystals at the DEB, leading to a continuum at the molecular level between dentin and enamel organic and mineral phases. To gain insight into the mechanisms of the DEB formation and structural basis of its mechanical resiliency we have studied the interactions between collagen fibrils, amelogenin assemblies, and forming mineral in vitro, using electron microscopy. Our data indicate that collagen fibrils guide assembly of amelogenin into elongated chain or filament-like structures oriented along the long axes of the fibrils. We also show that the interactions between collagen fibrils and amelogenin-calcium phosphate mineral complexes lead to oriented deposition of elongated amorphous mineral particles along the fibril axes, triggering mineralization of the bulk of collagen fibril. The resulting structure was similar to the mineralized collagen fibrils found at the DEB, with arrays of smaller well organized crystals inside the collagen fibrils and bundles of larger crystals on the outside of the fibrils. These data suggest that interactions between collagen and amelogenin might play an important role in the formation of the DEB providing structural continuity between dentin and enamel. PMID:20404336

Deshpande, Atul S; Fang, Ping-An; Simmer, James P; Margolis, Henry C; Beniash, Elia



RBS and XPS analyses of the composite calcium phosphate coatings for biomedical applications  

NASA Astrophysics Data System (ADS)

The calcium phosphate coatings on metallic implants are widely used for biomedical applications. The calcium phosphate coatings require mechanical strength, strong adhesion to the metallic implants, chemical stability and low dissolution into the human body fluid for stable functioning in the corrosive environment of the human body. In this study, a novel approach for improving the calcium phosphate coatings is utilized by adding trace metallic element into the coatings. We focused on teeth enamel, which is the hardest calcium phosphate tissue in the human body. Zn concentration increases exponentially from the interior to the surface of the enamel. As the Zn concentration increases, so the local hardness increases. Our previous studies suggest that Zn has influence on the hardness and other properties of enamel, calcium phosphate tissue. Calcium phosphate coatings doped with Zn was fabricated and characterized. The atomic composition and chemical state were investigated by using Rutherford backscattering spectroscopy (RBS) and X-ray photoelectron spectrometer (XPS), respectively. Scratch test was also carried out for measuring the adhesion of the coatings.

Ide-Ektessabi, Ari; Yamaguchi, Tetsuro; Tanaka, Yoshikazu



Calcium-phosphate microprecipitates mimic microparticles when examined with flow cytometry.  


There are increased levels of circulating microparticles (MPs) in several disease states. Flow cytometry is a common method to examine MPs, but their small size necessitates the use of markers to distinguish specifically MPs from artifact. Annexin V, which binds phosphatidylserine, is a commonly used marker for MP detection. Annexin V requires millimolar calcium ion for optimum binding. Ca(++) can precipitate with phosphate in phosphate-buffered saline (PBS). Calcium-phosphate microprecipitates were formed by titrating Ca(++) into PBS and examined using flow cytometry. Calcium-phosphate microprecipitates were compared with MPs derived from aged donor blood units. Microprecipitates were ?0.7-0.9 ?m in diameter compared with standard beads of known size. The microprecipitates disappeared with the addition of Ca(++) chelator. When we added fluorescently labeled antibodies to microprecipitates, the median fluorescent signal increased with increasing Ca(++) concentration regardless of specificity of the antibody. When repeated with a biological sample, there was an apparent increase in the fluorescent signal that returned to baseline after Ca(++) chelation. The flow cytometry signal of calcium-phosphate microprecipitates overlaps with the MP signal. Since Ca(++) is essential for annexin V binding, it is essential to avoid artifacts from calcium-phosphate microprecipitates when using any buffer or biological fluid containing phosphate. This also highlights the potential utility of flow cytometry for the analysis of crystals in biological fluids. PMID:23125136

Larson, Michael C; Luthi, Maia R; Hogg, Neil; Hillery, Cheryl A



Calcium and phosphate ion releasing composite: Effect of pH on release and mechanical properties  

Microsoft Academic Search

ObjectivesSecondary caries and restoration fracture are the two main challenges facing tooth cavity restorations. The objective of this study was to develop a composite using tetracalcium phosphate (TTCP) fillers and whiskers to be stress-bearing, and to be “smart” to increase the calcium (Ca) and phosphate (PO4) ion release at cariogenic pH.

Hockin H. K. Xu; Michael D. Weir; Limin Sun



Procedure for the study of acidic calcium phosphate precursor phases in enamel mineral formation  

Microsoft Academic Search

Summary Considerable evidence suggests that an acidic calcium phosphate, such as octacalcium phosphate (OCP) or brushite, is involved as a precursor in enamel and other hard tissue formation. Additionally, there is in vitro evidence suggesting that fluoride accelerates and magnesium inhibits the hydrolysis of OCP to hydroxyapatite (OHAp). As the amount of OCP or brushite in enamel cannot be measured

C. Siew; S. E. Gruninger; L. C. Chow; W. E. Brown



Biodegradation of four calcium phosphate ceramics; in vivo rates and tissue interactions  

Microsoft Academic Search

To prevent exposure of artificial tooth root implants, a resorbable root implant may be developed, that in time will resorb in a vertical direction at the same rate as the alveolar ridge does after the loss of the natural teeth. Implants of four calcium phosphates: rhenanite, ß-tricalcium phosphate, hydroxylapatite and magnesium-whitlockite were measured duringin vivo resorption and their interactions with

M. M. A. Ramselaar; F. C. M. Driessens; W. Kalk; J. R. Wijn; P. J. VAN MULLEM



A comparison of the calcium-free phosphate binder sevelamer hydrochloride with calcium acetate in the treatment of hyperphosphatemia in hemodialysis patients  

Microsoft Academic Search

Current phosphate binders used in hemodialysis patients include calcium-based binders that result in frequent hypercalcemia and aluminum-based binders that result in total body aluminum accumulation over time. This investigation describes the use of a calcium- and aluminum-free phosphate-binding polymer in hemodialysis patients and compares it with a standard calcium-based phosphate binder. An open-label, randomized, crossover study was performed to evaluate

Anthony J. Bleyer; Steven K. Burke; Maureen Dillon; Bruce Garrett; K. Shashi Kant; David Lynch; S. Noor Rahman; Patricia Schoenfeld; Isaac Teitelbaum; Steven Zeig; Eduardo Slatopolsky



Osteogenic responses to extraskeletally implanted synthetic porous calcium phosphate ceramics: an early stage histomorphological study in dogs  

Microsoft Academic Search

In this experiment, synthetic porous calcium phosphate ceramics (hydroxyapatite–tricalcium phosphate) were prepared and implanted in dorsal muscles of dogs. The purpose was to study the biological processes prior to and during the morphogenesis of bone in extraskeletally implanted porous calcium phosphate ceramics. Specimens were harvested after implantation for 7, 15, 30, 45, 60, 90 and 120 days. Decalcified and undecalcified




Addition of sodium hyaluronate and the effect on performance of the injectable calcium phosphate cement  

Microsoft Academic Search

An injectable calcium phosphate cement (CPC) with porous structure and excellent anti-washout ability was developed in the\\u000a study. Citric acid and sodium bicarbonate were added into the CPC powder consisting of tetracalcium phosphate (TTCP) and dicalcium\\u000a phosphate dihydrate (DCPD) to form macro-pores, then different concentrations of sodium hyaluronate (NaHA) solution, as liquid\\u000a phase, was added into the cement to investigate

Dan Kai; Dongxiao Li; Xiangdong Zhu; Lei Zhang; Hongsong Fan; Xingdong Zhang



Effects onWholeSaliva ofChewingGums Containing Calcium Phosphates  

Microsoft Academic Search

Toevaluate chewing gumsasavehicle toincrease salivary mineral saturation levels andenhance salivation, monocalcium phosphate monohydrate (MCPM)andan equimolar mixture oftetracalcium phosphate (TTCP) with dicalcium phosphate anhydrous (DCPA) werechosen asex- perimental chewing gumadditives. Eachofeight subjects chewed acommercial sugarless bubble gum(control) for16 minorthesamegumtowhich 5wt%ofMCPMortheTTCP- DCPAmixture hadbeen added. Thesaliva samples collected every 2minwereanalyzed forweight, pH,andtotal calcium (Ca) andphosphate (P) concentrations. Bothexperimental gumswerefound toincrease significantly theCaandPcon- centrations

L. C. Chow; S. Takagi; T. H. Chow; K. K. Takagi; A. Sieck


A comparative study of calcium phosphate formation on bioceramics in vitro and in vivo  

Microsoft Academic Search

Formation of calcium phosphate (Ca-P) on various bioceramic surfaces in simulated body fluid (SBF) and in rabbit muscle sites was investigated. The bioceramics were sintered porous solids, including bioglass, glass-ceramics, hydroxyapatite, ?-tricalcium phosphate and ?-tricalcium phosphate. The ability of inducing Ca-P formation was compared among the bioceramics. The Ca-P crystal structures were identified using single-crystal diffraction patterns in transmission electron

Renlong Xin; Yang Leng; Jiyong Chen; Qiyi Zhang



Retardation of Phosphate Release from Freshwater Benthic Sediments by Application of Ocher Pellets with Calcium Nitrate  

Microsoft Academic Search

This article presents an in situ treatment method for retardation of phosphate release from freshwater benthic sediments. The method is based on the addition of ocher pellets into benthic sediments. The pellets consist of ocher and calcium nitrate (OCN pellet). The OCN pellet slowly releases calcium and nitrate, together with ocher, into the sediment–water interface, where all three components play

Yu-Mee Na; Seok S. Park



Technology for recovery of phosphorus from animal wastewater through calcium phosphate precipitation  

Technology Transfer Automated Retrieval System (TEKTRAN)

A wastewater treatment process was developed for removal of phosphorus from livestock wastewater. The phosphorus is recovered as calcium phosphate with addition of only small quantities of liquid lime. The process is based on the distinct chemical equilibrium between phosphorus and calcium ions when...


Low temperature preparation of calcium phosphate structure via phosphorization of 3D-printed calcium sulfate hemihydrate based material  

Microsoft Academic Search

The conversion of newly developed three dimensionally printed calcium sulfate hemihydrate (70–90% wt\\/wt CaSO4·0.5·H2O) based materials to calcium phosphate bioceramics by phosphorization in di-sodium hydrogen phosphate solution at 80°C for\\u000a 4, 8, 16 and 24 h was studied. It was found that transformation rate, phase composition and mechanical properties were influenced\\u000a by porosity in the fabricated samples and by the duration of

J. Suwanprateeb; W. Suvannapruk; K. Wasoontararat



Concurrent elution of calcium phosphate and macromolecules from alginate/chitosan hydrogel coatings.  


The concurrent release of calcium phosphate and biomacromolecules may improve wound healing responses at the interface with ceramic materials of orthopaedic and dental implants. Hydrogel coatings consisting of a mixture of alginate and chitosan were doped and applied onto solid carriers with the aim of investigating their use as local delivery vehicles. Coatings containing both the model macromolecule FITC-dextran 70 kDa (FD 70) and dispersed calcium phosphate carbonate (CPC) nanoparticles were coated onto a solid, nonporous model substrate to study the concurrent release of FD 70 and calcium and phosphate ions from within the hydrogel. Hydrogel coatings containing only FD 70 were cast onto porous calcium phosphate coatings, similar to hydroxyapatite, to study the release of FD 70 from, and calcium and phosphate ions through, the hydrogel coating. Transmission electron microscopy showed good dispersion of the CPC nanoparticles, and scanning electron microscopy and atomic force microscopy showed that increased CPC loading resulted in an increase in surface roughness but to extents well below those affecting cell responses. The release of FD 70 from CPC-loaded coatings was similar to release from the hydrogel alone, although higher CPC loadings resulted in small changes. The release of FD 70 was better described by double or triple phase zero order release kinetics; this complex time dependence indicates that in addition to outdiffusion, other, time-dependent factors apply, such as swelling of the gel, as expected from the known effects of calcium ions on alginate. Calcium and phosphate ions were also released, with similar release kinetics, through the hydrogel layer from the underlying CaP layer. In either case, release decreased to negligible levels after 3 days, suggesting that the systems of this study are suitable for short-term concurrent release of water-soluble biomacromolecules and calcium and phosphate ions. PMID:20408707

Peng, Ping; Voelcker, Nicolas H; Kumar, Sunil; Griesser, Hans J



Calcium phosphate coating on titanium using laser and plasma spray  

NASA Astrophysics Data System (ADS)

Though calcium phosphate (CaP) coated implants are commercially available, its acceptance is still not wide spread due to challenges related to weaker interfacial bonding between metal and ceramic, and low crystallinity of hydroxyapatite (HA). The objectives of this research are to improve interfacial strength, crystallinity, phase purity and bioactivity of CaP coated metallic implants for orthopaedic applications. The rationale is that forming a diffuse and gradient metal-ceramic interface will improve the interfacial strength. Moreover, reducing CaP particles exposure to high temperature during coating preparation, can lead to improvement in both crystallinity and phase purity of CaP. In this study, laser engineered net shaping (LENS(TM)) was used to coat Ti metal with CaP. LENS(TM) processing enabled generation of Ti+TCP (tricalcium phosphate) composite coating with diffused interface, that also increased the coating hardness to 1049+/-112 Hv compared to a substrate hardness of 200+/-15 Hv. In vitro bone cell-material interaction studies confirmed the bioactivity of TCP coatings. Antimicrobial properties of the TCP coatings were improved by silver (Ag) electrodeposition. Along with LENS(TM), radio frequency induction plasma spray, equipped with supersonic plasma nozzle, was used to prepare HA coatings on Ti with improved crystallinity and phase purity. The coating was made of multigrain HA particles of ˜200 nm in size, which consisted of 15--20 nm HA grains. In vitro bone cell-material interaction and in vivo rat model studies confirmed the HA coatings to be bioactive. Furthermore, incorporation of Sr2+ improved bone cell of HA coatings interaction. A combination of LENS(TM) and plasma spray was used to fabricate a compositionally graded HA coatings on Ti where the microstructure varied from pure HA at the surface to pure Ti substrate with a diffused Ti+TCP composite region in between. The plasma spray system was used to synthesize spherical HA nano powder from HA sol, where the production rate was 20 g/h, which is only 16% of the total powder produced. The effects of Sr2+ and Mg2+ doping on bone cell-CaP interaction was further studied with osteoclast cells. Mg2+ doing was found to be an effective way of controlling osteoclast differentiation.

Roy, Mangal


Use of a calcium sulfate-calcium phosphate synthetic bone graft composite in the surgical management of primary bone tumors.  


Benign primary bone tumors are commonly treated with intralesional curettage with or without the use of surgical adjuvants. The reconstructive approach to the resulting contained bone defects is controversial, and clinical practice is varied. Synthetic bone substitutes may provide early mechanical support while minimizing the risks of disease transmission, nonunion, infection, and donor-site morbidity. Limited data exists regarding the use of calcium sulfate-calcium phosphate composite bone substitute for this purpose. The authors retrospectively reviewed the clinical outcomes of 24 patients with benign primary bone tumors who underwent intralesional curettage followed by reconstruction with a calcium sulfate-calcium phosphate composite bone substitute. Mean follow-up was 23 months. The most common diagnosis was giant cell tumor of bone. Six patients had upper-extremity tumors and 18 had lower-extremity tumors. Mean preoperative radiographic tumor volume was 41.0 cm(3). Mean volume of PRO-DENSE (Wright Medical Technology, Arlington, Tennessee) used in each patient was 15.6 cm(3). Mean time to full weight bearing for all patients was 7.3 weeks. Two patients sustained local tumor recurrences. No postoperative fractures occurred, and no complications occurred related to the use of the calcium sulfate-calcium phosphate composite. One case of deep infection occurred secondary to wound breakdown. The use of a calcium sulfate-calcium phosphate composite was associated with rapid biological integration and an early return to activities of daily living, with no composite-related complications. This technique is a viable option in the reconstruction of cavitary bone defects following intralesional curettage of primary benign bone tumors. PMID:23380017

Evaniew, Nathan; Tan, Victoria; Parasu, Naveen; Jurriaans, Erik; Finlay, Karen; Deheshi, Benjamin; Ghert, Michelle



Nucleation and growth of calcium phosphate on Ca-implanted titanium surface  

NASA Astrophysics Data System (ADS)

Calcium phosphate formation on Ca-implanted titanium surfaces is studied. Experimental results show that octacalcium phosphate (OCP) is the more energetically favorable phase to precipitate on the positively charged Ca-implanted titanium surfaces compared to hydroxylapatite (HA), especially with the existence of a large amount of CO32- ions. A solution-based cluster theory is employed to explain the process of the formation of calcium phosphate on the Ca-implanted titanium surfaces. Thermodynamic and kinetic calculations show that OCP is the kinetically favored phase to precipitate in the SBF solution than HA. The nucleation rate is much higher than that of HA, but HA is more stable thermodynamically.

Xie, Youtao; Liu, Xuanyong; Chu, Paul K.; Ding, Chuanxian



Evaluation of the mechanical properties of hot isostatically pressed titania and titania-calcium phosphate composites.  


A number of composites based on titania and calcium phosphates, hydroxyapatite, bone ash or beta-tricalcium phosphate, were sintered by glass-encapsulated hot isostatic pressing at 925 degrees C. The mechanical properties of the titania and titania-calcium phosphate composites--three-point bending strength, fracture toughness and Young's modulus--were 250-450 MPa, 2.5-2.9 MPa m1/2 and 230-270 GPa, respectively. Hardness and density were also measured. The results suggest that these composites have potential applications in medicine as implant materials. PMID:1888813

Li, J; Forberg, S; Hermansson, L



Effects on Whole Saliva of Chewing Gums Containing Calcium Phosphates  

Microsoft Academic Search

To evaluate chewing gums as a vehicle to increase salivary mineral saturation levels and enhance salivation, monocalcium phosphate monohydrate (MCPM) and an equimolar mixture of tetracalcium phosphate (TTCP) with dicalcium phosphate anhydrous (DCPA) were chosen as experimental chewing gum additives. Each of eight subjects chewed a commercial sugarless bubble gum (control) for 16 min or the same gum to which

L. C. Chow; S. Takagi; R. J. Shern; T. H. Chow; K. K. Takagi; B. A. Sieck



Premixed calcium phosphate cements: Synthesis, physical properties, and cell cytotoxicity  

PubMed Central

Objectives Calcium phosphate cement (CPC) is a promising material for dental, periodontal, and craniofacial repairs. However, its use requires on-site powder–liquid mixing that increases the surgical placement time and raises concerns of insufficient and inhomogeneous mixing. The objective of this study was to determine a formulation of premixed CPC (PCPC) with rapid setting, high strength, and good in vitro cell viability. Methods PCPCs were formulated from CPC powder + non-aqueous liquid + gelling agent + hardening accelerator. Five PCPCs were thus developed: PCPC-Tartaric, PCPC-Malonic, PCPC-Citric, PCPC-Glycolic, and PCPC-Malic. Formulations and controls were compared for setting time, diametral tensile strength, and osteoblast cell compatibility. Results Setting time (mean ± S.D.; n = 4) for PCPC-Tartaric was 8.2 ± 0.8 min, significantly less than the 61.7 ± 1.5 min for the Premixed Control developed previously (p < 0.001). On 7th day immersion, the diametral tensile strength of PCPC-Tartaric reached 6.5 ± 0.8 MPa, higher than 4.5 ± 0.8 MPa of Premixed Control (p = 0.036). Osteoblast cells displayed a polygonal morphology and attached to the nano-hydroxyapatite crystals in the PCPCs. All cements had similar live cell density values (p = 0.126), indicating that the new PCPCs were as cell compatible as a non-premixed CPC control known to be biocompatible. Each of the new PCPCs had a cell viability that was not significantly different (p > 0.1) from that of the non-premixed CPC control. Significance PCPCs will eliminate the powder–liquid mixing during surgery and may also improve the cement performance. The new PCPCs supported cell attachment and yielded a high cell density and viability. Their mechanical strengths approached the reported strengths of sintered porous hydroxyapatite implants and cancellous bone. These nano-crystalline hydroxyapatite cements may be useful in dental, periodontal, and craniofacial repairs.

Xu, Hockin H.K.; Carey, Lisa E.; Simon, Carl G.; Takagi, Shozo; Chow, Laurence C.



Incorporation of bioactive glass in calcium phosphate cement: An evaluation.  


Bioactive glasses (BGs) are known for their unique ability to bond to living bone. Consequently, the incorporation of BGs into calcium phosphate cement (CPC) was hypothesized to be a feasible approach to improve the biological performance of CPC. Previously, it has been demonstrated that BGs can successfully be introduced into CPC, with or without poly(d,l-lactic-co-glycolic) acid (PLGA) microparticles. Although an in vitro physicochemical study on the introduction of BG into CPC was encouraging, the biocompatibility and in vivo bone response to these formulations are still unknown. Therefore, the present study aimed to evaluate the in vivo performance of BG supplemented CPC, either pure or supplemented with PLGA microparticles, via both ectopic and orthotopic implantation models in rats. Pre-set scaffolds in four different formulations (1: CPC; 2: CPC/BG; 3: CPC/PLGA; and 4: CPC/PLGA/BG) were implanted subcutaneously and into femoral condyle defects of rats for 2 and 6 weeks. Upon ectopic implantation, incorporation of BG into CPC improved the soft tissue response by improving capsule and interface quality. Additionally, the incorporation of BG into CPC and CPC/PLGA showed 1.8- and 4.7-fold higher degradation and 2.2- and 1.3-fold higher bone formation in a femoral condyle defect in rats compared to pure CPC and CPC/PLGA, respectively. Consequently, these results highlight the potential of BG to be used as an additive to CPC to improve the biological performance for bone regeneration applications. Nevertheless, further confirmation is necessary regarding long-term in vivo studies, which also have to be performed under compromised wound-healing conditions. PMID:23159565

Renno, A C M; van de Watering, F C J; Nejadnik, M R; Crovace, M C; Zanotto, E D; Wolke, J G C; Jansen, J A; van den Beucken, J J J P



Bone formation in calcium-phosphate-coated titanium mesh.  


The osteogenic activity of porous titanium fiber mesh and calcium phosphate (Ca-P)-coated titanium fiber mesh loaded with cultured syngeneic osteogenic cells was compared in a syngeneic rat ectopic assay model. In 30 syngeneic rats, (Ca-P)-coated and non-coated porous titanium implants were subcutaneously placed either without or loaded with cultured rat bone marrow (RBM) cells. Fluorochrome bone markers were injected at 2, 4, and 6 weeks. The rats were sacrificed, and the implants were retrieved at 2, 4, and 8 weeks post-operatively. Histological analysis demonstrated that none of the (Ca-P)-coated and non-coated meshes alone supported bone formation at any time period. In RBM-loaded implants, bone formation started at 2 weeks. At 4 weeks, bone formation increased. However, at 8 weeks bone formation was absent in the non-coated titanium implants, while it had remained in the (Ca-P)-coated titanium implants. Also, in (Ca-P)-coated implants more bone was formed than in non-coated samples. In general, osteogenesis was characterized by the occurrence of multiple spheres in the porosity of the mesh. The accumulation sequence of the fluorochrome markers showed that the newly formed bone was deposited in a centrifugal manner starting at the center of a pore. Our results show that the combination of Ti-mesh with RBM cells can indeed generate bone formation. Further, our results confirm that a thin Ca-P coating can have a beneficial effect on the bone-generating properties of a scaffold material. PMID:10941922

Vehof, J W; Spauwen, P H; Jansen, J A



Dissolution properties of calcium phosphate granules with different compositions in simulated body fluid.  


Calcium phosphate granules were produced through the calcination of three hydroxyapatites (HAs) at 1150 degrees C: nearly-stoichiometric (NS-HA), calcium-deficient (CD-HA), and carbonated (Carb-HA). The characterization using scanning electron microscope (SEM), X-ray diffraction (XRD), and Fourier-transformed infrared spectroscopy (FT-IR) showed that those granules exhibit strong differences in chemical composition, surface texture, and dissolution behavior. Sample dissolution in a simulated body fluid (SBF) and precipitation of a calcium phosphate layer on the granule surface were followed up for 7 days by chemical analysis of calcium content in SBF. After 80-min reaction, precipitation of new calcium phosphate phases predominates over the dissolution of original granules. Comparison between SEM images and XRD/FT-IR analysis revealed that the composition of the calcium phosphate layer and its precipitation rate depend on the HA composition and its heat treatment. Calcined carbonated apatite induces the precipitation of an octacalcium phosphate (OPC) layer, whereas a carbonated apatite layer is formed from calcined-deficient HA. The calcined nearly-stoichiometric HA exhibits low efficiency in producing carbonated apatite layer. PMID:12734825

Monteiro, Magna Maria; Campos da Rocha, Nilce Carbonel; Rossi, Alexandre Malta; de Almeida Soares, Gloria



Effect of biomedical organic compounds on the setting reaction of calcium phosphates.  


In the present study, the effect of biomedical organic compounds (starch, sodium alginate, chitosan and gelatin) on the hydration of calcium phosphates was studied using X-ray diffraction, infrared spectroscopy, scanning electron microscopy and XPS analysis. Amorphous calcium phosphate (ACP) was prepared by a mechanochemical route and mixed with biomedical organic compounds. A solidification reaction occurred between ACP and dicalcium phosphate dihydrate (DCPD); the hydration product was poorly crystallized hydroxyapatite (HA). During the setting reaction of ACP and DCPD, the presence of biomedical organic compounds had an effect on the hydration product: the bonding energies of the primary elements (Ca, P) in the hydration product (HA) were changed; also different hydration morphologies, self-setting properties, rheological properties and mechanical strength of the cement were obtained. This work will allow advances in the synthesis of bionic composite calcium phosphate cement (CPC). PMID:19811895

Yu, Tao; Ye, Jiandong; Gao, Chengying; Yu, Long; Wang, Yingjun



Single-step rapid microwave-assisted synthesis of polyacrylamide–calcium phosphate nanocomposites in aqueous solution  

Microsoft Academic Search

Organic–inorganic polyacrylamide–calcium phosphate (PAM–CP) nanocomposites with calcium phosphate (CP) nanoparticles homogeneously dispersed in the polymer matrix have been successfully synthesized using calcium salt, phosphate and acrylamide monomer in aqueous solution by a single-step microwave-assisted method. When the experiment is conducted in a basic medium, the CP phase obtained consists of hexagonal hydroxyapatite (HAP) nanorods, and HAP nanorods are homogeneously dispersed

Qi-Li Tang; Ke-Wei Wang; Ying-Jie Zhu; Feng Chen



Bioresorption behavior of tetracalcium phosphate-derived calcium phosphate cement implanted in femur of rabbits.  


One primary focus of the present study was to clarify the crucial resorption-location relationship of a recently developed single-phase TTCP-derived calcium phosphate cement (CPC) implanted in rabbit femur in a systematic and quantitative way. Gross examination of retrieved CPC/bone composite samples indicated that the CPC implant did not evoke inflammatory response, necrosis or fibrous encapsulation in surrounding bony tissues. Histological examination revealed excellent CPC-host bone bonding. At 4 weeks, the resorption-induced voids between terminals of bone defects and implants were largely filled with new bone. CPC resorption, new blood vessels, osteocytes, osteons and osteoblast-like cells lining up with active new bone were observed at remodeling sites. At 12 weeks, a new bone network was developed within femoral defect, while CPC became islands incorporated in the new bone. At this stage, crevices filled with lamellar new bone structure were frequently observed. At 24 weeks, bone ingrowth and remodeling activities became so extensive that the interface between residual cement and new bone became less identifiable. In general, at all implant locations the resorption ratio values increased with implantation time, while at all implantation times the resorption ratios decreased from the exterior (cortical site) to the interior (cancellous site) of implants. At the end of 24 weeks, CPC was almost completely resorbed and bone remodeling almost finished at the cortical site. PMID:18096221

Tsai, Chih-Hung; Lin, Ruey-Mo; Ju, Chien-Ping; Chern Lin, Jiin-Huey



Biomimetic synthesis of poly(propylene-fumarate)-calcium phosphate composites for tissue engineering  

NASA Astrophysics Data System (ADS)

A novel in-situ co-precipitation process for the synthesis of poly(propylene-fumarate)-calcium phosphate composites was developed. In this process the calcium phosphate phase nucleates and grows in the presence of poly(propylene-fumarate) (PPF), in a novel two-solvent system including tetrahydrofuran (THF) and water. It was found that the presence of the organic solvent (THF) does not affect the phase evolution of the calcium phosphate. Both in the presence and absence of THF crystalline dicalcium phosphate dihydrate (DCPD, brushite) and poorly crystalline hydroxyapatite (HAp) form, and transform to crystalline HAp after 24 hours of synthesis time. Contrary to the organic solvent, PPF has a significant influence on the calcium phosphate phase that forms in its presence. It is found that PPF provides a template for the formation of the calcium phosphate phase through a coordination bond between the calcium ion and the carbonyl group of the polymer. As a result of this templating, hydroxyapatite can form in a significantly shorter period of time (˜1 hr) compared to the system where PPF is not present (24 hrs). The nature of the calcium phosphate phase that forms in the presence of PPF depends on the molecular weight and concentration of PPF. High concentration of PPF in the composite (e.g. 80%) stabilizes an amorphous calcium phosphate (ACP) phase and hinders its transformation to crystalline apatite, while low concentration of PPF (e.g. 5%) promotes the formation of crystalline apatite. Higher molecular weight PPF (Mw = 4500) is found to be more efficient in stabilizing the amorphous phase compared to lower molecular weight PPF (Mw = 1800). While high molecular weight PPF stabilizes ACP, low molecular weight PPF promotes its conversion to crystalline apatite. TEM observations revealed that flake-like hydroxyapatite crystals form in the absence of PPF while spherical ACP particles form in a composite containing 80% PPF. The ACP nano-particles (50-100 nm in diameter) are homogeneously distributed within the PPF matrix. The PPF-calcium phosphate composite can crosslink into a 3D structure by UV irradiation.

Hakimi Mehr, Dorna


High-calcium vs high-phosphate intake and small artery tone in advanced experimental renal insufficiency  

Microsoft Academic Search

Background. Disturbed calcium-phosphorus balance significantly contributes to uraemic changes in large arteries. We examined the influences of high-calcium and high-phosphate intake on small artery tone in experimental renal insufficiency. Methods. Sixty-five rats were assigned to 5\\/6 nephrec- tomy (NTX) or sham operation. After 15 week disease progression, NTX rats were given high-calcium (3%), high-phosphate (1.5%) or control diet (0.3% calcium,

Peeter Koobi; Tuija I. Vehmas; Pasi Jolma; Jarkko Kalliovalkama; Meng Fan; Onni Niemela; Heikki Saha; Mika Kahonen; Pauli Ylitalo; Jaana Rysa; Heikki Ruskoaho; Ilkka Porsti


New developments in polymer-controlled, bioinspired calcium phosphate mineralization from aqueous solution.  


The polymer-controlled and bioinspired precipitation of inorganic minerals from aqueous solution at near-ambient or physiological conditions avoiding high temperatures or organic solvents is a key research area in materials science. Polymer-controlled mineralization has been studied as a model for biomineralization and for the synthesis of (bioinspired and biocompatible) hybrid materials for a virtually unlimited number of applications. Calcium phosphate mineralization is of particular interest for bone and dental repair. Numerous studies have therefore addressed the mineralization of calcium phosphate using a wide variety of low- and high-molecular-weight additives. In spite of the growing interest and increasing number of experimental and theoretical data, the mechanisms of polymer-controlled calcium phosphate mineralization are not entirely clear to date, although the field has made significant progress in the last years. A set of elegant experiments and calculations has shed light on some details of mineral formation, but it is currently not possible to preprogram a mineralization reaction to yield a desired product for a specific application. The current article therefore summarizes and discusses the influence of (macro)molecular entities such as polymers, peptides, proteins and gels on biomimetic calcium phosphate mineralization from aqueous solution. It focuses on strategies to tune the kinetics, morphologies, final dimensions and crystal phases of calcium phosphate, as well as on mechanistic considerations. PMID:23291492

Bleek, Katrin; Taubert, Andreas



Direct transformation from amorphous to crystalline calcium phosphate facilitated by motif-programmed artificial proteins  

PubMed Central

An animal's hard tissue is mainly composed of crystalline calcium phosphate. In vitro, small changes in the reaction conditions affect the species of calcium phosphate formed, whereas, in vivo, distinct types of crystalline calcium phosphate are formed in a well-controlled spatiotemporal-dependent manner. A variety of proteins are involved in hard-tissue formation; however, the mechanisms by which they regulate crystal growth are not yet fully understood. Clarification of these mechanisms will not only lead to the development of new therapeutic regimens but will also provide guidance for the application of biomineralization in bionanotechnology. Here, we focused on the peptide motifs present in dentin matrix protein 1 (DMP1), which was previously shown to enhance hydroxylapatite (HAP) formation when immobilized on a glass substrate. We synthesized a set of artificial proteins composed of combinatorial arrangements of these motifs and successfully obtained clones that accelerated formation of HAP without immobilization. Time-resolved static light-scattering analyses revealed that, in the presence of the protein, amorphous calcium phosphate (ACP) particles increased their fractal dimension and molecular mass without increasing their gyration radii during a short period before precipitation. The protein thus facilitated reorganization of the internal structure of amorphous particles into ordered crystalline states, i.e., the direct transformation of ACP to HAP, thereby acting as a nucleus for precipitation of crystalline calcium phosphate. Without the protein, the fractal dimension, molecular mass, and gyration radii of ACP particles increased concurrently, indicating heterogeneous growth transformation.

Tsuji, Toru; Onuma, Kazuo; Yamamoto, Akira; Iijima, Mayumi; Shiba, Kiyotaka



Templating route for mesostructured calcium phosphates with carboxylic acid- and amine-type surfactants.  


Mesostructured calcium phosphates constructed by ionic frameworks were synthesized using carboxylic acid- and amine-type surfactants in mixed solvent systems of ethanol and water. A lamellar mesostructured calcium phosphate was prepared using palmitic acid as an anionic surfactant, as in the case using n-alkylamines. A wormhole-like mesostructured calcium phosphate can be obtained using dicarboxyl N-lauroyl- l-glutamic acid, whose headgroup is larger than that of palmitic acid. Similar mesostructured product was obtained using 4-dodecyldiethylenetriamine with a large headgroup containing two primary amine groups. Interactions of carboxyl and primary amino groups in the surfactant molecules with inorganic species are quite important for the formation of mesostructured calcium phosphates. The Ca/P molar ratio of mesostructured calcium phosphates was strongly affected by the molecular structure of surfactants containing carboxyl and primary amino groups. Ca-rich materials can be obtained using carboxylic acid-type surfactants (Ca/P approximately 1.7) rather than amine-type surfactants (Ca/P approximately 1.0). PMID:18947246

Ikawa, Nobuaki; Hori, Hideki; Kimura, Tatsuo; Oumi, Yasunori; Sano, Tsuneji



Lipid-coated nano-calcium-phosphate (LNCP) for gene delivery  

PubMed Central

While calcium-phosphate has been used to deliver plasmid DNA (pDNA) for decades, the method is typically characterized by low and irreproducible transfection efficiency relative to the other non-viral approaches, such as liposomes and polymers. Here we report a novel gene transfer vector comprising lipid-coated nano-calcium-phosphate (LNCP) that provides consistently efficient and satisfactory pDNA delivery. It is based on core-shell nanoparticles comprising a calcium-phosphate core and a cationic lipid shell. This method, in contrast to the solution precipitation methods used in the past, yields colloidally stable calcium-phosphate nanoparticles inside the cationic liposomes. Our results indicate that the particle size and the size distribution of the LNCP remain virtually unchanged even after 21 days of storage. Atomic force microscopy measurements reveal that the LNCP have a 5-fold higher rigidity than common cationic liposomes. The LNCP transfected pDNA 24 times greater than the naked pDNA and 10-fold greater relative to the standard calcium-phosphate precipitation preparations, suggesting that the LNCP may have potential as a novel transfection agent for gene therapy.

Zhou, Chenguang; Yu, Bo; Yang, Xiaojuan; Huo, Tianyao; Lee, L. James; Barth, Rolf F.; Lee, Robert J.



Encapsulation of plasmid DNA in calcium phosphate nanoparticles: stem cell uptake and gene transfer efficiency  

PubMed Central

Background The purpose of this study was to develop calcium phosphate nanocomposite particles encapsulating plasmid DNA (CP-pDNA) nanoparticles as a nonviral vector for gene delivery. Methods CP-pDNA nanoparticles employing plasmid transforming growth factor beta 1 (TGF-?1) were prepared and characterized. The transfection efficiency and cell viability of the CP-pDNA nanoparticles were evaluated in mesenchymal stem cells, which were identified by immunofluorescence staining. Cytotoxicity of plasmid TGF-?1 and calcium phosphate to mesenchymal stem cells were evaluated by MTT assay. Results The integrity of TGF-?1 encapsulated in the CP-pDNA nanoparticles was maintained. The well dispersed CP-pDNA nanoparticles exhibited an ultralow particle size (20–50 nm) and significantly lower cytotoxicity than Lipofectamine™ 2000. Immunofluorescence staining revealed that the cultured cells in this study were probably mesenchymal stem cells. The cellular uptake and transfection efficiency of the CP-pDNA nanoparticles into the mesenchymal stem cells were higher than that of needle-like calcium phosphate nanoparticles and a standard calcium phosphate transfection kit. Furthermore, live cell imaging and confocal laser microscopy vividly showed the transportation process of the CP-pDNA nanoparticles in mesenchymal stem cells. The results of a cytotoxicity assay found that both plasmid TGF-?1 and calcium phosphate were not toxic to mesenchymal stem cells. Conclusion CP-pDNA nanoparticles can be developed into an effective alternative as a nonviral gene delivery system that is highly efficient and has low cytotoxicity.

Cao, Xia; Deng, Wenwen; Wei, Yuan; Su, Weiyan; Yang, Yan; Wei, Yawei; Yu, Jiangnan; Xu, Ximing



Biomimetic coprecipitation of calcium phosphate and bovine serum albumin on titanium alloy.  


Titanium alloy implants were precoated biomimetically with a thin and dense layer of calcium phosphate and then incubated either in a supersaturated solution of calcium phosphate or in phosphate-buffered saline, each containing bovine serum albumin (BSA) at various concentrations, under physiological conditions for 48 h. Coated implants then underwent scanning electron microscopy, immunohistochemical evaluation, Fourier transform infrared spectroscopy, and X-ray diffraction. The quantity of BSA taken up by coatings and the kinetics of protein release were monitored colorimetrically. In coatings prepared by the coprecipitation of calcium phosphate and BSA, protein had become incorporated into the mineral crystal latticework. With increasing BSA concentration, matrices decreased in thickness, became more dense, showed lower crystallinity, and underwent a change in crystal geometry. The octacalcium phosphate structure manifested in the absence of protein was gradually transformed into a carbonated apatite form. Preformed mineral coatings became only superficially mantled with a layer of BSA, and the morphology of the mineral matrices themselves remained unchanged. At equivalent protein concentrations, coatings prepared by the coprecipitation of calcium phosphate released only a minute fraction of its protein component under physiological conditions, whereas preformed mineral matrices showed a "burst" release of their associated protein within a single 2-h period. The biomimetic coating can be a carrier for osteoinductive agents. PMID:11523027

Liu, Y; Layrolle, P; de Bruijn, J; van Blitterswijk, C; de Groot, K



Formation of hydroxyapatite in soils using calcium citrate and sodium phosphate for control of strontium migration.  

SciTech Connect

{sup 90}Sr contamination is a major problem at several U.S. sites. At some sites, {sup 90}Sr has migrated deep underground making site remediation difficult. In this paper, we describe a novel method for precipitation of hydroxyapatite, a strong sorbent for {sup 90}Sr, in soil. The method is based on mixing a solution of calcium citrate and sodium phosphate in soil. As the indigenous soil microorganisms mineralize the citrate, the calcium is released and forms hydroxyapatite. Soil, taken from the Albuquerque desert, was treated with a sodium phosphate solution or a sodium phosphate/calcium citrate solution. TEM and EDS were used to identify hydroxyapatite with CO{sub 3}{sup 2-} substitutions, with a formula of (Ca{sub 4.8}Na{sub 0.2})[(PO{sub 4}){sub 2.8}(CO{sub 3}){sub 0.2}](OH), in the soil treated with the sodium phosphate/calcium citrate solution. Untreated and treated soils were used in batch sorption experiments for Sr uptake. Average Sr uptake was 19.5, 77.0 and 94.7% for the untreated soil, soil treated with sodium phosphate, and soil with apatite, respectively. In desorption experiments, the untreated soil, phosphate treated soil and apatite treated soil released an average of 34.2, 28.8 and 4.8% respectively. The results indicate the potential of forming apatite in soil using soluble reagents for retardation of radionuclide migration.

Moore, Robert Charles; Hasan, Ahmed Ali Mohamed; Sanchez, Charles Anthony (University of Arizona, Yuma, AZ); Zhao, Hongting; Salas, Fred Manuel; Hasan, Mahmoud A. (Egyptian Atomic Energy Authority, Cairo, Egypt); Holt, Kathleen Caroline



Phosphate removal from wastewaters by a naturally occurring, calcium-rich sepiolite.  


Developing an easily handled and cost-effective phosphate absorbent is crucial for the control of water eutrophication. In this study, a naturally occurring, calcium-rich sepiolite (NOCS) was evaluated for its feasibility as a phosphate absorbent candidate. Batch studies showed that phosphate sorption on NOCS followed a stepwise isotherm for concentrations between 5 and 1000 mg P/l, and the phosphate sorption was fitted well by the Freundlich equation. The estimated maximum phosphorus sorption capacity was 32.0 mg P/g, which was quite high compared with other natural materials and was comparable to some efficient manmade P absorbents. The NOCS sorption kinetics followed a pseudo-first-order model with an R(2) value of 0.999. The adsorption of phosphate was highly pH dependent. Phosphate adsorption decreased moderately with increasing pH values from 3.0 to 6.0, and it decreased sharply in alkaline conditions. Ionic strength, sulfate, nitrate and chloride anions had no effects on the phosphate removal capacity of NOCS, but fluoride and bicarbonate anions exerted large effects. Phosphorus fractionation indicated that phosphate removed from the solution was primarily formed as a calcium-bound phosphorus precipitation, which was further confirmed by SEM-EDS analysis. Moreover, phosphate was barely (<1.5%) desorbed from the phosphorus-adsorbed sepiolite regardless of pH value. PMID:22088501

Yin, Hongbin; Yun, Ye; Zhang, Yinlong; Fan, Chengxin



Comparative reduction of enamel demineralization by calcium and phosphate in vitro.  


In theory, calcium and phosphate in the plaque fluid exert a large influence on the demineralization of enamel surface. In order to know the effect of increasing the concentration of either of these factors, the following in vitro experiment was conducted. Three thin sections, about 150 Im thick, were cut out from each of 13 human premolars. All surfaces of the sections, except for the original enamel surface, were coated with nail varnish. These sections were immersed into one of two sets of demineralizing solutions for 1 week at 25 degrees C. Each set, the 'calcium set' and the 'phosphate set', contained three solutions. The composition of these solutions differed mainly in calcium or phosphate concentrations. After 1 week, the degree of demineralization was determined by image analysis of contact microradiograms from each section. The subsurface demineralization in enamel was reduced by 95% by increasing the calcium concentration of the demineralizing solution from 7 to 21 mmol/l. A similar reduction (87%) was observed by increasing the phosphate concentration. However, the amount of phosphate needed was approximately 20 times more than that of calcium. The larger inhibitory effect that calcium has on enamel demineralization was related to the larger effect it has on the degree of saturation of the solution. Even though no statistically significant difference was found between the effect of calcium and phosphate on the demineralization of enamel (when the solutions had the same degree of saturation), the difference in the standard deviation of demineralization suggests the existence of some other factors which have an influence on the demineralization reaction. PMID:10867423

Tanaka, M; Kadoma, Y


Calcium acetate versus calcium carbonate as oral phosphate binder in pediatric and adolescent hemodialysis patients  

Microsoft Academic Search

Calcium carbonate is widely used as an oral phosphorus binder to control hyperphosphatemia in children on maintenance hemodialysis.\\u000a Intestinal calcium absorption may induce hypercalcemia, particularly if calcitriol is given simultaneously. In adults, calcium\\u000a acetate binds phosphorus more effectively than calcium carbonate, while reducing the frequency of hypercalcemic events. We\\u000a therefore compared calcium acetate with calcium carbonate in nine pediatric patients

Michael Wallot; Klaus-Eugen Bonzel; Andreas Winter; Birgit Geiirger; Bernhard Lettgen; Martin Bald



Dense and porous titanium substrates with a biomimetic calcium phosphate coating  

NASA Astrophysics Data System (ADS)

The present work studied a biomimetic method using a simplified solution (SS) with calcium and phosphorus ions for coating titanium substrates, in order to improve their bioactivity. Commercially pure titanium dense sheet, microporous and macroporous titanium samples, both produced by powder metallurgy, were treated in NaOH solution followed by heat-treating and immersed in SS for 7, 14 or 21 days. The samples characterization was performed by quantitative metallographic analysis, confocal scanning optical microscopy, scanning electron microscopy, energy dispersive spectroscopy and low angle X-ray diffraction. The results showed coatings with calcium phosphate precipitation in all samples, with globular or plate-like morphology, typical of hydroxyapatite and octacalcium phosphate, respectively, indicating that the solution (SS) has potential for coating titanium substrates. In addition, the different surfaces of substrates had an effect on the formed calcium phosphate phase and thickness of coatings, depending on the substrate type and imersion time in the simplified solution.

Ribeiro, A. A.; Balestra, R. M.; Rocha, M. N.; Peripolli, S. B.; Andrade, M. C.; Pereira, L. C.; Oliveira, M. V.



Steel corrosion protection by means of alkyd paints pigmented with calcium acid phosphate  

SciTech Connect

The use of classic anticorrosive pigments is becoming more and more restricted by increasing environmental concerns; they are gradually being replaced by zinc phosphate and related compounds. Other anticorrosive pigments such as surface-exchanged silicas were also proposed. The object of this research is to study the anticorrosive properties of calcium acid phosphate as an inhibitive pigment, introducing a careful selection of complementary pigments in order to achieve an efficient anticorrosive protection. Several alkyd paints were prepared and evaluated through accelerated and electrochemical tests. The nature of the passive film formed was also studied. Paint containing zinc oxide and calcium carbonate (50/50) as complementary pigments showed the best performance in the salt spray test. Zinc oxide and calcium carbonate decreased film permeability and improved steel passivation. The passive film was composed of ferric oxyhydroxide, the pores of which became plugged by ferric phosphate.

Amo, B. del; Romagnoli, R.; Vetere, V.F. [CIC-CONICET, La Plata (Argentina)



Preparation of tricalcium phosphate/calcium pyrophosphate structures via rapid prototyping.  


Custom made tricalcium phosphate/calcium pyrophosphate bone substitutes with a well-defined architecture were fabricated in this study using 3D powder printing with tricalcium phosphate (TCP) powder and a liquid phase of phosphoric acid. The primary formed matrix of dicalcium phosphate dihydrate (DCPD, brushite) was converted in a second step to calcium pyrophosphate (CPP) by heat treatment in the temperature range 1,100-1,300 degrees C. The structures exhibited compressive strengths between 0.8 MPa and 4 MPa after sintering at 1,100-1,250 degrees C, higher strengths were obtained by increasing the amount of pyrophosphate formed in the matrix due to a post-hardening regime prior sintering as well as by the formation of a glass phase from TCP and calcium pyrophosphate above 1,280 degrees C, which resulted in a strong densification of the samples and compressive strength of >40 MPa. PMID:18236137

Gbureck, Uwe; Hölzel, Tanja; Biermann, Isabell; Barralet, Jake E; Grover, Liam M



Ossification vesicles with calcium phosphate in the eyes of the insect Copium teucrii (Hemiptera: Tingidae).  


Arthropod eyes are built of repeating units named ommatidia. Each single ommatidium unit contains a cluster of photoreceptor cells surrounded by support cells and pigment cells. The insect Copium eye ommatidia include additional calcium-phosphate deposits, not described in insects to date, which can be examined today using a combined set of modern microscopy and spectroscopy techniques. Teucrium gnaphalodes L'Her plants, growing in central Spain, develop galls induced by Copium insects. A survey of C. teucrii adult specimens resulted in surprising environmental scanning electron microscopy (ESEM) images, showing that their bright red eyes contain a calcium-phosphate mineralization. A complete survey of Copium eye specimens was performed by ESEM using energy-dispersive spectroscopy, backscattered electron detector and cathodoluminescence (CL) probes, field emission scanning electron microscopy, micro-Raman spectroscopy, and confocal laser scanning microscopy in order to learn ommatidia features, such as chemical composition, molecular structure, cell membrane, and internal ommatidium eye fluids and calcium-phosphate distribution deposits. The CL panchromatic images distinguish between the calcium-phosphate ommatidium and calcium-phosphate setae, which are more apatite rich. They show Raman bands attributable to bone tissue apatite biomaterials, such as bone, collagen, lipids, and blood, i.e., peptides, amide-S, amide-II, amide-III, and cytochrome P-450 scc. The chemical composition of both galls and leaves of T. gnaphalodes was determined by gas chromatography-mass spectrometry (GC-MS) of their extracts. The spectrometric and microscopic images reveal that the calcium-phosphate mineralization is formed and constrained to Copium ommatidia, which are both matrix vesicles generating mixtures of apatite collagen and operational compound eyes of the insect. PMID:21258761

Garcia-Guinea, Javier C; Jorge, Alberto C; Tormo, Laura; Furio, Marta; Crespo-Feo, Elena; Correcher, Virgilio; Prado-Herrero, Pedro; Soria, Ana C; Sanz, Jesus; Nieves-Aldrey, Jose L



Fabrication and characterization of poly(lactic-co-glycolic acid) microsphere/amorphous calcium phosphate scaffolds.  


Although hydroxyapatite (HAP) and ?-tricalcium phosphate have been used extensively as osteoconductive minerals in biomaterial scaffolds for bone regeneration, they lack the capacity to stimulate osteoblastic differentiation of progenitor cells. In contrast, amorphous calcium phosphates (ACPs), which convert to HAP under aqueous conditions, have the potential to facilitate osteoblastic differentiation through the transient local release of calcium and phosphate ions. Therefore, in this study ACPs were synthesized using zinc and zirconia divalent cations as stabilizers (denoted ZnACP and ZrACP, respectively) and compared to HAP. Analysis of ion release into serum-containing cell culture medium revealed transiently elevated levels of calcium and phosphorous, consistent with the enhanced solubility of ZrACP and ZnACP relative to HAP. In addition, X-ray diffraction analysis revealed partial conversion of ZrACP to HAP but no conversion of ZnACP after 96 h. Next, scaffolds were fabricated by sintering mixtures of 300-500 µm poly(D,L-lactic-co-glycolic acid) (PLGA) microspheres and 0.5 wt% calcium phosphate mineral (HAP, ZrACP or ZnACP) at 70 °C for 24 h. Scanning electron microscopy revealed a porous microsphere matrix with calcium phosphate particulates clinging to the microsphere surfaces both prior to and after 14 days in culture medium. Finally, the incorporation of calcium phosphate resulted in a lower compressive modulus in the range 127 to 74-89 MPa. Taken together, these results indicate that ZrACP, ZnACP and HAP minerals exhibit very different properties, and therefore may elicit different osteoblastic responses in vitro. PMID:21312335

Popp, Jenni R; Laflin, Kate E; Love, Brian J; Goldstein, Aaron S



A composite coating by electrolysis-induced collagen self-assembly and calcium phosphate mineralization.  


A composite coating that is composed of collagen protein and calcium phosphate minerals is considered to be bioactive and may enhance bone growth and fixation of metallic orthopedic implants. In this study, we have successfully developed a uniform collagen fibril/octacalcium phosphate composite coating on silicon substrate by electrolytic deposition (ELD). The coating deposition was done through applying a constant potential to the cathode in a three-electrode electrochemistry cell that contain a mild acidic (pH 4.8-5.3) aqueous solution of collagen molecules, calcium and phosphate ions. The coating process involved self-assembly of collagen fibrils and the deposition of calcium phosphate minerals as a result of cathode reaction and local pH increase. The two steps could be synchronized to form a bone-like composite at nanometer scale through proper adjustment of the solution and deposition parameters. Coating morphology, crystal structure and compositions were analyzed by optical and fluorescence microscopy, scanning and transmission electron microscopy, energy dispersive X-ray analysis, inductively coupled argon plasma optical emission spectrophotometry, and Fourier-transformed infrared spectroscopy. Under typical deposition conditions, the cathode (Si) surface formed a thin (100 nm) layer of calcium phosphate coating, on top of which a thick (approximately 100 microm) composite layer formed. The porous composite layer consists of a collagen fibril network on which clusters of octacalcium phosphate crystals nucleate and grow. By combining photolithography and ELD, we were also able to pattern the composite coating into regular arrays of squares. Preliminary results by nanoindentation tests showed that properly prepared composite coating may have higher elastic modulus and scratch resistance than monolithic porous calcium phosphate coating. The results not only provide a novel bioactive coating for biomedical implants, but also establish a new experimental protocol for studying biomineralization mechanisms of collagen based biological tissues. PMID:15576136

Fan, Yuwei; Duan, Ke; Wang, Rizhi



Optimization of the mineral content in polymeric gels: The effect of calcium to phosphate molar ratio  

Microsoft Academic Search

The influence of calcium to phosphate (Ca\\/P) molar ratio on the extent of mineralization in a model (poly)acrylamide gel was investigated under simulated physiological conditions. We hypothesized that the optimal growth of hydroxyapatite crystals will take place at the stoichiometric Ca\\/P molar ratio of 1.67. Phosphate ions were incorporated during the polymerization of the gel and mineralization was initiated by

Prasenjit Das; Ozan Akkus; Abdul-Majeed Azad



Biomimetic Nanocomposites of Calcium Phosphate and Self-Assembling Triblock and Pentablock Copolymers  

SciTech Connect

In an effort to mimic the growth of natural bone, self-assembling, micelle and gel-forming copolymers were used as a template for calcium phosphate precipitation. Because of the cationic characteristics imparted by PDEAEM end group additions to commercially available Pluronic{reg_sign} Fl27, a direct ionic attraction mechanism was utilized and a polymer-brushite nanocomposite spheres were produced. Brushite coated spherical micelles with diameters of {approx}40 nm, and agglomerates of these particles (on the order of 0.5 {mu}m) were obtained. Thickness and durability of the calcium phosphate coating, and the extent of agglomeration were studied. The coating has been shown to be robust enough to retain its integrity even below polymer critical micelle concentration and/or temperature. Calcium phosphate-polymer gel nanocomposites were also prepared. Gel samples appeared as a single phase network of agglomerated spherical micelles, and had a final calcium phosphate concentration of up to 15 wt%. Analysis with x-ray diffraction and NMR indicated a disordered brushite phase with the phosphate groups linking inorganic phase to the polymer.

Drew Lenzen Enlow



A multi-textured calcium phosphate coating for hard tissue via laser surface engineering  

NASA Astrophysics Data System (ADS)

Surface engineering continues to play an important role in improving the biocompatibility of hard tissue replacements. Recently, the hierarchical organization of natural biomaterials has been realized as an important property that guides the attachment of tissues, cells, and proteins at various levels of interactions. Currently, researchers are focusing interest on developing hierarchical bioactive structures for effective osseointegration. The present effort discusses a multi-textured calcium-phosphate-based coating produced by laser surface engineering. The chemical and morphological evolution of these bio-actively textured coatings was studied along with biomimetic precipitation of calcium phosphates when immersed in simulated body fluids.

Kurella, Anil; Dahotre, Narendra B.



Prebiotic Formation of ADP and ATP from AMP, Calcium Phosphates and Cyanate in Aqueous Solution  

NASA Astrophysics Data System (ADS)

Adenosine-5'-triphosphate was synthesized by the phosphorylation of adenosine-5'-diphosphate in aqueous solution containing cyanate as a condensing reagent and insoluble calcium phosphate produced from phosphate and calcium chloride. In a similar manner, adenosine-5'-diphosphate was synthesized from adenosine-5'-monophosphate. When the experiment was carried out in the conditions of 4 °C and pH 5.75, the formation of adenosine-5'-diphosphate and adenosine-5'-triphosphate from adenosine-5'-monophosphate was observed in the yields of 19 and 7%, respectively. The other nucleoside-5'-triphosphates were also produced from their respective diphosphates.

Yamagata, Yukio



Anticariogenicity of Calcium Phosphate Complexes of Tryptic Casein Phosphopeptides in the Rat  

Microsoft Academic Search

Casein phosphopeptides (CPP) stabilize calcium phosphate through the formation of casein-phosphopeptide amorphous calcium-phosphate complexes (CPP-CP). The ability of CPP-CP to reduce caries activity was investigated by use of specific-pathogen-free rats inoculated with Streptococcus sobrinus. The animals consumed a defined cariogenic diet free of dairy products. Solutions (100 pL) of the CPP-CP (0.1, 0.2, 0.5, 1.0% w\\/v) were applied to the

E. C. Reynolds; C. J. Cain; EL Webber; C. L. Black; P. F. Riley; I. H. Johnson; J. W. Perich



Influence of annealing temperature on RF magnetron sputtered calcium phosphate coatings.  


The effect of different annealing temperatures on the characteristics of thin calcium phosphate coatings fabricated by radiofrequency magnetron sputtering was studied. Annealing of the as-sputtered films was necessary to change the amorphous coating to a crystalline coating. The films were annealed for 2 and 4 h at 400, 600, 800, 1000 and 1200 degrees C under dry argon or argon and water vapour flow. After annealing, the structure and the chemical composition of these films were characterized with incident light microscopy, Rutherford backscattering spectrometry (RBS), X-ray diffraction (XRD), and Fourier transform infrared absorption spectrometry (FTIR). Incident light microscopy showed cracks in the coatings annealed at a higher temperature than 400 degrees C. RBS revealed that the as-sputtered coatings had a high Ca/P ratio which decreased with increasing annealing temperature. After annealing at a temperature of 600 degrees C or more the XRD showed crystalline hydroxyapatite (HA) coatings. However, the second phase, present in the coatings, changed from tetra-calcium phosphate to calcium oxide to beta-tri-calcium phosphate with increasing annealing temperature. FTIR measurements showed the existence of OH- and PO- bonds in all coatings, although the PO- bonds varied for different annealed coatings, from the PO- bonds due to HA to PO- bonds due to other calcium phosphates. From the results of this study we suggest that 600 degrees C is probably the best annealing temperature to obtain a better characterization and understanding of the coating. PMID:8938234

van Dijk, K; Schaeken, H G; Wolke, J G; Jansen, J A



In vitro characterisation of calcium phosphate biomaterials loaded with lidocaine hydrochloride and morphine hydrochloride  

Microsoft Academic Search

Calcium phosphate substitutes drug delivery systems are well known substances used in minor bone void-filling to release their\\u000a therapeutic agent in situ. Few studies associating anaesthetics and analgesics have been performed to date. The aim of this\\u000a work was to study the association of the analgesic, morphine, and the local anaesthetic, lidocaine, with a calcium deficient\\u000a apatite matrix. Three types

H. Gautier; V. Chamblain; P. Weiss; C. Merle; J. M. Bouler



Absorption of calcium from milks enriched with fructo- oligosaccharides, caseinophosphopeptides, tricalcium phosphate  

Microsoft Academic Search

Background: Adequate intakes of calcium are required for optimal bone health and protection against chronic disease. Dairy products are an excellent source of calcium. Objective:Theabsorptionofcalciumfromarangeoffortifiedmilks was measured in humans with the use of stable isotopes. Design:Fifteenvolunteersparticipatedinarandomized,controlled, double-blind crossover study. Five types of semi-skimmed (1.9% fat) milk drinks were administered with a light breakfast: standard milk(controlmilk);milkenrichedwithcalciumfrommilksolidsand tricalcium phosphate ((TCP) MSS milk);

Eduardo Lopez-Huertas; Birgit Teucher; Julio J Boza; Antonio Martínez-Férez; Gosia Majsak-Newman; Luis Baro; Juan J Carrero; María Gonzalez-Santiago; Juristo Fonolla; Susan Fairweather-Tait


Surface properties of calcium phosphate particles for self setting bone cements.  


Calcium phosphate cements (CPC), consist of multicomponent powder mixtures of calcium orthophosphates with grain sizes in the region of 1-20 microm. Due to the small particle sizes surface properties as the zeta potential and adsorption processes play a significant role during manufacturing and application. In the context of this work zeta potentials of different calcium phosphates, like dicalcium phosphate anhydride (DPCA) tetracalcium phosphate (TTCP) and hydroxyapatite were measured in various organic/aqueous media with different pH values. The results show a strong dependency of the zeta potential on the kind of suspension medium used associated with different milling properties. The addition of sodium phosphate leads to a pH value dependent stabilization of the particles in the liquid phase; the zeta potential of the surface increases from about -15 to -18 mV in water and from -35 to -45 mV in 0.05 mol/l sodium phosphate solution. Besides the interaction of particles with various antibiotics was determined on the basis of the zeta potential of the surface. The substances partly cause a tremendous change of the surface load. This is accompanied by a change of the rheological properties of the cement paste, the morphology of the hardened cement matrix and a significant deterioration of the application-relevant properties as setting time or mechanical strength. PMID:12202161

Gbureck, U; Probst, J; Thull, R



Inorganic phosphate regulates Glvr-1 and -2 expression: role of calcium and ERK1/2.  


Sodium-dependent phosphate cotransporters are key regulators of phosphate homeostasis and play a major role in mineralized tissues remodelling. However, factors influencing their expression remain under consideration. In our study, modulation of type III sodium-dependent phosphate cotransporters expression by inorganic phosphate (Pi) was investigated in the murine odontoblast-like cell line MO6-G3. Experiments were designed to determine the effects of phosphate release on dental cells during tooth decay. By real-time RT-PCR we demonstrated that Glvr-1 and -2 expressions are up-regulated by Pi. The increase in Glvr-1 and -2 expressions was correlated with ERK1/2 phosphorylation and calcium/phosphate crystals formation in cultured wells. Using calcium-free culture conditions or the specific inhibitor of ERK phosphorylation (UO126), we demonstrated that Pi effects on Glvr-1 and -2 up-regulation require the presence of calcium and involve ERK signalling pathways. This study contributes to give new insights in the control of Pi transport during carious diseases. PMID:19232318

Wittrant, Y; Bourgine, A; Khoshniat, S; Alliot-Licht, B; Masson, M; Gatius, M; Rouillon, T; Weiss, P; Beck, L; Guicheux, J



Effects of additives on the rheological properties and injectability of a calcium phosphate bone substitute material.  


An injectable calcium phosphate bone substitute material has been prepared by mixing amorphous calcium phosphate (ACP) and dicalcium phosphate dihydrate (DCPD) for use in noninvasive surgery, and the influence of additives, such as disodium hydrogen phosphate, polyethylene glycol (PEG), glycerin, and citric acid, on the rheological properties and injectability of the ACP + DCPD cement system have been studied in this work. Novel approach of thixotropy measurement has been used to characterize the stability of the pastes. The results show that the injectability and the setting time can be augmented by the addition of disodium phosphate solution to the paste but reduced by the addition of PEG 200, glycerin, or citric acid to the paste. This study suggests that the injectability and the setting time of the ACP + DCPD bone substitute material can be balanced, and the injectable calcium phosphate bone substitute material with satisfied fluidity and injectability for clinical operation can be prepared by optimizing the additives and their concentrations, according to different clinical requirements. PMID:16362962

Wang, Xiupeng; Ye, Jiandong; Wang, Hai



The influence of proteins on calcium phosphate deposition over titanium implants studied by dynamic contact angle analysis and XPS  

Microsoft Academic Search

The spontaneous formation of a calcium phosphate (apatite-like) layer on the surface of titanium implants in contact with biological model fluids is well known, but the effect of the presence of proteins in real biological fluids is not yet well understood. In this work, the process of calcium phosphate deposition on titanimn surfaces immersed in Hank's balanced salt solution (HBSS)

Ana Paula Valagão Amadeu do Serro; Anabela Catarino Fernandes; Benilde de Jesus; Vieira Saramago



Antigen adsorbed calcium phosphate nanoparticles stimulate both innate and adaptive immune response in fish, Labeo rohita H.  


Calcium phosphate nanoparticles as an antigen/protein delivery was explored in a fish model Labeo rohita H. S-layer protein (of Aeromonas hydrophila) adsorbed on nano sized calcium phosphate particles elicited both innate and adaptive immune parameters which persisted up to 63 days of post immunization through parenteral immunization and gave cross protections. PMID:21889128

Behera, Truptimayee; Swain, Priyabrat



Control of renal calcium, phosphate, electrolyte, and water excretion by the calcium-sensing receptor.  


Through regulation of excretion, the kidney shares responsibility for the metabolic balance of calcium (Ca(2+)) with several other tissues including the GI tract and bone. The balances of Ca(2+) and phosphate (PO4), magnesium (Mg(2+)), sodium (Na(+)), potassium (K(+)), chloride (Cl(-)), and water (H2O) are linked via regulatory systems with overlapping effects and are also controlled by systems specific to each of them. Cloning of the calcium-sensing receptor (CaSR) along with the recognition that mutations in the CaSR gene are responsible for two familial syndromes characterized by abnormalities in the regulation of PTH secretion and Ca(2+) metabolism (Familial Hypocalciuric Hypercalcemia, FHH, and Autosomal Dominant Hypocalcemia, ADH) made it clear that extracellular Ca(2+) (Ca(2+)o) participates in its own regulation via a specific, receptor-mediated mechanism. Demonstration that the CaSR is expressed in the kidney as well as the parathyroid glands combined with more complete characterizations of FHH and ADH established that the effects of elevated Ca(2+) on the kidney (wasting of Na(+), K(+), Cl(-), Ca(2+), Mg(2+) and H2O) are attributable to activation of the CaSR. The advent of positive and negative allosteric modulators of the CaSR along with mouse models with global or tissue-selective deletion of the CaSR in the kidney have allowed a better understanding of the functions of the CaSR in various nephron segments. The biology of the CaSR is more complicated than originally thought and difficult to define precisely owing to the limitations of reagents such as anti-CaSR antibodies and the difficulties inherent in separating direct effects of Ca(2+) on the kidney mediated by the CaSR from associated CaSR-induced changes in PTH. Nevertheless, renal CaSRs have nephron-specific effects that contribute to regulating Ca(2+) in the circulation and urine in a manner that assures a narrow range of Ca(2+)o in the blood and avoids excessively high concentrations of Ca(2+) in the urine. PMID:23856264

Tyler Miller, R



Lack of relationship between activity of intestinal alkaline phosphatase and calcium or phosphate absorption.  


The effects of vitamin D3 and the aqueous extract of Solanum malacoxylon on intestinal alkaline phosphatase and tissue phosphate content were studied on rachitic chicks treated with large doses of ethane-1-hydroxy-1,1 diphosphonate (EHDP). The EHDP treatment blocks the increase of intestinal calcium or phosphate absorption induced by the vitamin D3, while it has no effects on the rise of intestinal alkaline phosphatase activity or the increment in tissue phosphate content. The lack of correlation between the increment of alkaline phosphatase and that of Ca or phosphate absorption in vitamin D3 plus EHDP treated chicks excludes a participation of the alkaline phosphatase in the mechanism of Ca or P intestinal absorption. The Ca or phosphorus absorption are elicited specifically by 1,25-(OH)2-D3, while alkaline phosphatase activity and phosphate tissue concentration respond to a broader spectrum of stimuli. PMID:6316731

Asteggiano, C; Tolosa, N; Pereira, R; Moreno, J; Cañas, F



Fabrication of calcium phosphate-calcium sulfate injectable bone substitute using hydroxy-propyl-methyl-cellulose and citric acid  

PubMed Central

In this study, an injectable bone substitute (IBS) consisting of citric acid, chitosan, and hydroxyl propyl methyl cellulose (HPMC) as the liquid phase and tetra calcium phosphate (TTCP), dicalcium phosphate dihydrate (DCPD) and calcium sulfate dehydrate (CSD, CaSO4·2H2O) powders as the solid phase, were fabricated. Two groups were classified based on the percent of citric acid in the liquid phase (20, 40 wt%). In each groups, the HPMC percentage was 0, 2, and 4 wt%. An increase in compressive strength due to changes in morphology was confirmed by scanning electron microscopy images. A good conversion rate of HAp at 20% citric acid was observed in the XRD profiles. In addition, HPMC was not obviously affected by apatite formation. However, both HPMC and citric acid increased the compressive strength of IBS. The maximum compressive strength for IBS was with 40% citric acid and 4% HPMC after 14 days of incubation in 100% humidity at 37°C.

Thai, Van Viet



RenaGel®, a nonabsorbed calcium- and aluminum-free phosphate binder, lowers serum phosphorus and parathyroid hormone  

Microsoft Academic Search

RenaGel®, a nonabsorbed calcium- and aluminum-free phosphate binder, lowers serum phosphorus and parathyroid hormone.Background.This multicenter, open-label, dose-titration study assessed the safety and efficacy of RenaGel®, a nonabsorbed calcium- and aluminum-free phosphate binder, in lowering serum phosphorus. Secondary outcomes were its effects on serum intact parathyroid hormone (iPTH) and serum lipids.Methods.Phosphate binders were discontinued during a two-week washout period. Patients whose




Effect of molecular weight and concentration of poly(acrylic acid) on the formation of a polymeric calcium phosphate cement  

Microsoft Academic Search

Previous investigations have noted that the tetracalcium phosphate (TTCP)\\/dicalcium phosphate anhydrous (DCPA) apatite forming calcium phosphate cement (CPC) possesses many favorable properties from a biomaterials standpoint. Despite these positive properties various shortcomings have limited clinical usage of these materials and fostered investigations into the effect of numerous additives. The present study concerns the effect of poly(acrylic acid) (PAA) addition and

A. O. Majekodunmi; S. Deb; J. W. Nicholson



Synthesis of Calcium Hydroxyapatite-Tricalcium Phosphate (HA-TCP) Composite Bioceramic Powders and Their Sintering Behavior  

Microsoft Academic Search

Composite (biphasic) mixtures of two of the most important inorganic phases of synthetic bone applications—namely, calcium hydroxyapatite (Ca10(PO4)6(OH)2 (HA)) and tri- calcium phosphate (Ca3(PO4)2 (TCP))—were prepared as submicrometer-sized, chemically homogeneous, and high- purity ceramic powders by using a novel, one-step chemical precipitation technique. Starting materials of calcium ni- trate tetrahydrate and diammonium hydrogen phosphate salts that were dissolved in appropriate

Nezahat Kivrak; A. Cuneyt Tas



Setting properties, mechanical strength and in vivo evaluation of calcium phosphate-based bone cements  

Microsoft Academic Search

Calcium phosphate cement (CPC) is a promising material for use in minimally invasive surgery for bone defect repair due to its similarity to the mineral phase of bone, biocompatibility, bioactivity, self-setting characteristics, low setting temperature, adequate stiffness and ease of shaping in complicated geometrics. In this study, we systematically investigate the influence of preparation variables on the final properties of

So Yeon Kim; Sung Hyun Jeon


Calcium phosphate grafts produced by rapid prototyping based on laser cladding  

Microsoft Academic Search

Rapid prototyping based on laser cladding by powder injection has been used to produce calcium phosphate three-dimensional grafts without using molds. Precursor material comprising of hydroxyapatite (HA) powder was irradiated by means of an infrared Nd:YAG laser. The processing parameters and the thermal history of the processed material have been assessed and the process has been optimized to obtain solid

R. Comesaña; F. Lusquiños; J. del Val; T. Malot; M. López-Álvarez; A. Riveiro; F. Quintero; M. Boutinguiza; P. Aubry; A. De Carlos; J. Pou



Influence of annealing temperature on RF magnetron sputtered calcium phosphate coatings  

Microsoft Academic Search

The effect of different annealing temperatures on the characteristics of thin calcium phosphate coatings fabricated by radiofrequency magnetron sputtering was studied. Annealing of the as-sputtered films was necessary to change the amorphous coating to a crystalline coating. The films were annealed for 2 and 4 h at 400, 600, 800,1000 and 1200 °C under dry argon or argon and water

K. van Dijk; H. G. Schaeken; J. G. C. Wolke; J. A. Jansen



Differentiation and activity of human preosteoclasts on chitosan enriched calcium phosphate cement  

Microsoft Academic Search

Chitosan associated to various scaffolds has been shown to promote growth and mineral rich matrix deposition by osteoblasts in vitro, whereas its influence on osteoclast differentiation, which plays also a central role in bone remodeling, has never been described. The purpose of this study was to investigate the differentiation and activity of human preosteoclastic cells on calcium phosphate cement containing

Nathalie Rochet; Thierry Balaguer; Florian Boukhechba; Jean-Pierre Laugier; Danielle Quincey; Stéphane Goncalves; Georges F. Carle



Calcium phosphate coating on titanium substrate by a modified electrocrystallization process  

Microsoft Academic Search

Modification of ethyl alcohol added aqueous electrolyte for depositing calcium phosphate on titanium substrates by a electrocrystallization method is described. Film coated in the electrolyte with ethyl alcohol addition is more homogeneous and the growth rate is higher. The optimum quantity of ethyl alcohol added is 50% of the electrolyte. Although the pH value of electrolyte varies as ethyl alcohol

Jim-Shone Chen; Horng-Yih Juang; Min-Hsiung Hon



Inflammatory cytokine response to titanium chemical composition and nanoscale calcium phosphate surface modification  

Microsoft Academic Search

Nanoscale surface modification of titanium dental implants with calcium phosphate (CaP) has been shown to achieve superior bone wound healing and osseointegration compared with smooth or microrough titanium surfaces alone. As bone healing has been shown to be influenced by the action of cytokines, this study examined whether changes in cytokine gene expression from RAW 264.7 cells cultured on commercially

Stephen Hamlet; Saso Ivanovski




Microsoft Academic Search

A rapid procedure for analysis of calcium and phosphate ions in ; fertilizer samples using the double-decomposition radio-release technique proved ; unsuccessful. The radiorelease system is based on a difference in solubility of ; two compounds. A solution containing the radio-inactive ion of interest is ; passed through a column of some material, perhaps an ion exchanger, containing a ;

H. G. Richter; A. S. Jr. Gillespie



Morphology controlled porous calcium phosphate nanoplates and nanorods with enhanced protein loading and release functionality.  


Calcium phosphate nanoplates and nanorods with controllable pores and enhanced protein loading and tuneable release characteristics are first synthesized without the use of any toxic surfactants by an energy efficient microwave assisted chemical process, hence demonstrating their viability as a tool for controllable drug delivery in biomaterial systems. PMID:23404951

Reardon, Philip James Thomas; Huang, Jie; Tang, Junwang



Biomimetic Nanocomposites of Calcium Phosphate and Self-Assembling Triblock and Pentablock Copolymers.  

National Technical Information Service (NTIS)

In an effort to mimic the growth of natural bone, self-assembling, micelle and gel-forming copolymers were used as a template for calcium phosphate precipitation. Because of the cationic characteristics imparted by PDEAEM end group additions to commercial...

D. L. Enlow



Macroporous biphasic calcium phosphate ceramics: influence of macropore diameter and macroporosity percentage on bone ingrowth  

Microsoft Academic Search

SynopsisA total of 60 cylindrical 6×6 mm samples of a macroporous biphasic calcium phosphate (MBCP) ceramic were impla nted into a distal femoral site in 30 rabbits. These samples represented six kinds of implants with two different macropore diamete rs and three different macroporosity percentages. Analysis of backscattered electron images of implant surfaces analysed by a factorial design method showed

Olivier Gauthier; Jean-Michel Bouler; Eric Aguado; Paul Pilet; Guy Daculsi



Plasma spraying induced changes of calcium phosphate ceramic characteristics and the effect on in vitro stability  

Microsoft Academic Search

Plasma spraying is a commonly used technique to apply thin calcium phosphate ceramic coatings. Special consideration is given to retaining the original structure of CPC particles. However, changes are possible. Thus this study focused on plasma spraying induced changes in material characteristics of commercial coatings and their influence onin vitro dissolution. All analysed coatings were found to undergo significant plasma

S. R. Radin; P. Ducheyne



A preliminary study on osteoinduction of two kinds of calcium phosphate ceramics  

Microsoft Academic Search

With respect to the effect of material factors on calcium phosphate biomaterial-induced osteogenesis, the osteoinductive property of two kinds of porous hydroxyapatite ceramics, which were made by different producers, was investigated in dorsal muscles of dogs. One hydroxyapatite ceramic (S-HA), macroporous implants with rough pore walls containing abundant micropores, was made by Sichuan Union University (Chengdu, China); the other hydroxyapatite

Huipin Yuan; Kenji Kurashina; Joost D de Bruijn; Yubao Li; K de Groot; Xingdong Zhang



Protein–calcium phosphate interactions in fouling of modified stainless-steel surfaces by simulated milk  

Microsoft Academic Search

The deposition behaviour of the main components of milk fouling (?-lactoglobulin and calcium phosphate) and its dependence on the surface energy properties of the fouling support were evaluated in this work. As deposition supports, several modified stainless-steel materials obtained by surface modification techniques were used. Four fouling systems were analysed: an aqueous solution that resembles the mineral composition of milk

Roxane Rosmaninho; Luis F. Melo



Synthesis and Formulation of Zinc-strengthened Calcium Phosphate Polycarboxylate Cements  

Microsoft Academic Search

A novel zinc-strengthened calcium phosphate polycarboxylate cement modified with amino acid has been developed. Synthesis of glass fillers and monomers as well as polymers and formulation of the cements are described. The effects of silanization, sintering, glass composition, grafting ratio of the methacrylate groups, molecular weight, tartaric acid and polymer content on compressive strength and curing time were investigated. The

Dong Xie; Guigui Wang; Il-Doo Chung



Microarchitecture of calcium phosphate granules and fibrin glue composites for bone tissue engineering  

Microsoft Academic Search

Calcium phosphate ceramics are currently used as bone graft substitutes in various types of clinical applications. Fibrin glue is also used in surgery due to its haemostatic, chemotactic and mitogenic properties. By combining these two biomaterials, new composite scaffolds were prepared. In this study, we attempt to analyse whether thrombin concentration in the fibrin glue could influence the properties of

Damien Le Nihouannen; Laurent Le Guehennec; Thierry Rouillon; Paul Pilet; Melitta Bilban; Pierre Layrolle; Guy Daculsi



Dietary and Pharmacological Control of Calcium and Phosphate Metabolism in Dialysis Patients  

Microsoft Academic Search

Chronic kidney disease-mineral and bone disorder is a new term defining a complex syndrome which underlines the need of a systemic approach to disturbances of calcium and phosphate metabolism in patients with renal failure. In recent years, the availability of new phosphorus binders and the appearance of new selective vitamin D receptor activators and calcimimetics have increased our current armamentarium

J. Bover; E. Andrés; M. J. Lloret; A. Aguilar; J. Ballarín



Effect of blood addition on the biocompatibility of calcium phosphate paste  

Microsoft Academic Search

The effect of blood addition on the biocompatibility and mechanical properties of calcium phosphate paste (CPP) has been examined. The addition of blood to the CPP increased the consistency and setting time in the malaxation operation; the specimen with blood addition possessed higher carbonate content and greater solubility into the acid but lower compressive strength, compared to the specimen without

Tomohiro Umeda; Kiyoshi Itatani; Hiroshi Endo; Hiroyasu Takeuchi; Kazuhiro Mizutani; Yoshiro Musha



In vitro: osteoclastic activity studies on surfaces of 3D printed calcium phosphate scaffolds.  


Various biomaterials have been developed for the use as bone substitutes for bone defects. To optimize their integration and functionality, they should be adapted to the individual defect. Rapid prototyping is a manufacturing method to tailor materials to the 3D geometry of the defect. Especially 3D printing allows the manufacture of implants, the shape of which can be designed to fit the bone defect using anatomical information obtained from the patient. 3D printing of calcium phosphates, which are well established as bone substitutes, involves a sintering step after gluing the granules together by a binder liquid. In this study, we analyzed if and how these 3D printed calcium phosphate surfaces can be resorbed by osteoclast-like cells. On 3D printed scaffold surfaces consisting of pure HA and ?-TCP as well as a biphasic mixture of HA and TCP the osteoclastic cell differentiation was studied. In this regard, cell proliferation, differentiation, and activation were analyzed with the monocytic cell line RAW 264.7. The results show that osteoclast-like cells were able to resorb calcium phosphate surfaces consisting of granules. Furthermore, biphasic calcium phosphate ceramics exhibit, because of their osteoclastic activation ability, the most promising surface properties to serve as 3D printed bone substitute scaffolds. PMID:20659962

Detsch, Rainer; Schaefer, Susannne; Deisinger, Ulrike; Ziegler, Guenter; Seitz, Hermann; Leukers, Barbara



[Preparation and properties of calcium silicate-phosphate composite bone cements].  


In this paper, alpha-tricalcium phosphate (alpha-TCP) and tetracalcium phosphate (TTCP) respectively were chosen as basic compositions of phosphate bone cements. Other auxiliary materials such as hydroxyapatite (HAP), dicalcium phosphate dihydrate (DCPD), calcium carbonate (CaCO3), calcium oxide (CaO) and amorphous calcium silicate (CaSiO3) were added in the cements. Six kinds of composite bone cements were decided with 1.50 as their Ca/P ratio. Then the primary properties of them were studied. Ringer's simulated body fluid (SBF) tests were carried out for the samples. The changes of pH value in SBF and the compressive strength of the samples with the immersion time were studied. The results showed: the mixing liquid 0.25 M K2HPO4/KH2PO4 and amorphous CaSiO3 were effective for accelerating the setting of the cements; the initial setting time (It) was about 4-5.5 min and the final setting time (Ft) was about 18-19. 5 min. Amorphous calcium silicate can increase the compressive strength of the bone cements remarkably; the compressive strength of the alpha-TCP bone cement with the addition of suitable amount amorphous CaSiO3 reached 45.3 MPa after immersion in SBF for 14 days. PMID:16532825

Wang, Zhiqiang; Hu, Jilin; Liu, Xiaolei; Chen, Xiaoxu; Lü, Bingling



Synthesis of nanocrystalline calcium phosphate in microemulsion--effect of nature of surfactants.  


Nanosized calcium phosphate (CP) powders have been synthesized by an inverse microemulsion system using kerosene as the oil phase, a cationic surfactant Aliquat 336, a non-ionic surfactant Tween 20 and their mixture and aqueous solutions of calcium nitrate tetrahydrate and biammonium hydrogen phosphate as the water phase. It has been found that the nature of surfactants played an important role to regulate the size and morphologies of the calcium phosphate nanoparticles. The cationic surfactant Aliquat 336 has been found to regulate the nucleation and crystal growth. The synthesized powders have been comprehensively characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), powder X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Our results show that the brushite (DCPD) is the major phase comprising the calcium phosphate nanoparticles. In mixed surfactants mediated system a morphological controlled highly crystalline particles have been synthesized. Further, the role of Aliquat 336 has been established and a plausible synthetic mechanism has been proposed. PMID:18083184

Singh, Sujata; Bhardwaj, Pallavi; Singh, V; Aggarwal, S; Mandal, U K



Transformation of Amorphous Calcium Phosphate to Crystalline Dahllite in the Radular Teeth of Chitons  

NASA Astrophysics Data System (ADS)

A comparison of infrared spectra from individual teeth along the radula of a chiton (Polyplacophora, Mollusca) shows that the first-formed calcium phosphate mineral is amorphous. Over a period of weeks the mineral transforms to dahllite. The c axes of the dahllite crystals are aligned approximately perpendicular to the tooth surface.

Lowenstam, H. A.; Weiner, S.



New chemolysis for urological calcium phosphate calculi – a study in vitro  

Microsoft Academic Search

BACKGROUND: Advances in techniques have left very few indications for open surgical extraction of urinary stones currently. These advances notwithstanding, the search continues for medical approaches to urinary stone management. In this study, we perform an in vitro study analyzing the efficiency and prospect of two new complex solutions in urological calcium phosphate calculi dissolution. METHODS: Eighteen stones composed mainly

Zhang Xiang-bo; Wang Zhi-ping; Duan Jian-min; Lu Jian-zhong; Ma Bao-liang



Corrosion control of galvanized steel using a phosphate\\/calcium ion inhibitor mixture  

Microsoft Academic Search

The corrosion inhibition of galvanized steel was studied in artificial acid rain solution using extracts of pigments normally used in organic coatings for corrosion control. It was established that a combination of zinc phosphate\\/molybdate and calcium ion exchange silica has a significant synergetic anticorrosion effect in the acid rain solution compared to the pigments used alone. Further, the charge transfer

I. M. Zin; S. B. Lyon; V. I. Pokhmurskii



Histological evaluation of the bone response to calcium phosphate cement implanted in cortical bone  

Microsoft Academic Search

The aim of this study was to investigate the physicochemical and biological properties of a newly developed calcium phosphate cement (CaP cement) implanted in cortical bone. CaP cement was injected as a paste into tibia cortical bone defects in goats. Polymethylmethacrylate (PMMA) bone cement was used as a control. The animals were killed after 3 days, 2, 8, 16 and

E. M Ooms; J. G. C Wolke; M. T van de Heuvel; B Jeschke; J. A Jansen



Phosphorus-31 NMR Studies of Cell Wall-Associated Calcium-Phosphates in Ulva lactuca.  


Phosphate concentrations in the range 0.1 to 2.0 millimolar induced the formation of extracellular amorphous calcium-phosphates in the cell wall of the marine macro algae Ulva lactuca when they were cultivated in light in seawater at 20 degrees C. A broad resonance representing these compounds as well as resonances for extracellular orthophosphate and polyphosphates could be followed by (31)P-nuclear magnetic resonance spectroscopy. The presence of the calcium-phosphate made the cells brittle and it inhibited the growth of the macro algae and caused mortality within 1 week. The formation of the calcium-phosphates was influenced by the external phosphate concentration, the extracellular pH and the nature and concentration of the external nitrogen source. Furthermore, no formation of these compounds was observed when Ulva lactuca was cultivated in the dark, at low temperatures (5 degrees C) or in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea. The complex could be removed through washes with ethylenediaminetetraacetate; this treatment did not alter the intracellular pH or the orthophosphate and polyphosphate pools and it restored growth. PMID:16666741

Weich, R G; Lundberg, P; Vogel, H J; Jensén, P



Intercalation of n-alkyltrimethylammonium ions into layered calcium octyl phosphates thermally treated in vacuo.  


Layered calcium octyl phosphate (CH3(CH2)7OPO3Ca.1.6H2O: CaOP), which is composed of a multilayer alternating bilayer of octyl phosphates and a dicalcium phosphate dihydrate (DCPD)-like phase, was thermally treated in vacuo and the intercalation of n-alkyltrimethylammonium ions into the materials was examined. The octyl groups in the layer were eliminated by outgassing above 250 degrees C to give the amorphous calcium phosphates. Further, the specific surface area was steeply increased and mesopores with a diameter of ca. 2.0 nm were formed. IR results indicated that the surface P-OH groups were generated by outgassing at 250 degrees C. When the CaOP outgassed at 250 degrees C was treated with n-alkyltrimethylammonium ion solutions (carbon number of alkyl group, n=14-18), three XRD peaks reappeared below 2theta=15 degrees and the d-spacing ratio of these peaks was 1:1/2:1/3. These facts indicate that the n-alkyltrimethylammonium ions were intercalated into the amorphous calcium phosphate phases. PMID:15082410

Tanaka, Hidekazu; Oomori, Koji; Hino, Ryozi



Gas phase laser synthesis and processing of calcium phosphate nanoparticles for biomedical applications  

NASA Astrophysics Data System (ADS)

Biochemical processes make pervasive use of calcium and phosphate ions. Calcium phosphate salts that are naturally nontoxic and bioactive have been used for several medical applications in form of coatings and micropowders. Nanoparticle-based calcium phosphates have been shown to be internalized by living cells and be effective in DNA transfection, drug delivery, and transport of fluorophores for imaging of intracellular processes. They are also expected to interact strongly with cell adhesive proteins and are therefore promising elements in approaches to mimic the complex environment of the extra cellular matrix of bone. Harnessing this biomedical potential requires the ability to control the numerous characteristics of nanophase calcium phosphates that affect biological response, including nanoparticle chemical composition, crystal phase, crystallinity, crystallographic orientation of exposed faces, size, shape, surface area, number concentration, and degree of aggregation. This dissertation focuses on the use of laser-induced gas-phase synthesis for creation of calcium phosphate nanoparticles, and corresponding nanoparticle-based substrates that could offer new opportunities for guiding biological responses through well-controlled biochemical and topological cues. Gas-phase synthesis of nanoparticles has several characteristics that could enhance control over particle morphology, crystallinity, and surface area, compared to liquid-phase techniques. Synthesis from gas-phase precursors can be carried out at high temperatures and in high-purity inert or reactive gas backgrounds, enabling good control of chemistry, crystal structure, and purity. Moreover, the particle mean free path and number concentration can be controlled independently. This allows regulation of interparticle collision rates, which can be adjusted to limit aggregation. High-temperature synthesis of well-separated particles is therefore possible. In this work high power lasers are employed to vaporize microcrystalline calcium phosphate materials to generate an aerosol of nanoparticles which is further processed and deposited using principles of aerosol mechanics. Particles and resulting particle-based systems are analyzed by transmission electron microscopy, atomic force microscopy, X-ray diffraction, and optical absorption. Obtained substrates are functionalized with cell adhesive peptides. Findings show that laser-induced gas-phase synthesis provides attractive new dimensions in the controlled fabrication of calcium phosphate nanoparticles, including manipulation not only of size and chemical composition, but also crystal phase make-up, fractal structure, and nanotopography of derived substrates.

Bapat, Parimal V.


Comparative Effectiveness of Calcium-Containing Phosphate Binders in Incident U.S. Dialysis Patients  

PubMed Central

Summary Background and objectives Few studies have assessed the association between phosphate binder use and hard outcomes in dialysis patients. Furthermore, the comparative effectiveness of calcium carbonate and acetate is untested. We studied the association between use versus nonuse of calcium-containing phosphate binders (CCPBs) and mortality from any cause. We also tested whether mortality differed among users of individual CCPBs. Design, setting, participants, & measurements A nationally representative prospective cohort of incident U.S. dialysis patients (1996 to 1997), assembled before the availability of sevelamer and lanthanum, was used. Use of each CCPB was ascertained from chart abstraction records. A large number of sociodemographic, clinical, and laboratory characteristics were available for confounding control in multivariate and propensity score-matched Cox regression models. Results Among 3603 incident dialysis patients, 77.5% used a CCPB, whereas 22.5% did not. Baseline use of CCPB was associated with an adjusted 19% lower mortality rate among CCPB users compared with nonusers. With successful matching of 800 exposed and nonexposed individuals on their exposure propensity score, however, CCPB users and nonusers had similar mortality. No mortality differences were observed between calcium acetate and calcium carbonate users in crude, adjusted, or propensity-matched analyses. Conclusions No association was found between CCPB use and 1-year mortality in incident dialysis patients; choice of calcium carbonate versus acetate was also not associated with this outcome. Randomized trials are necessary to understand whether the prevailing practice of phosphate-binding therapy actually reduces adverse clinical outcomes.

Liu, Jun; Kestenbaum, Bryan



The role of intracellular calcium phosphate in osteoblast-mediated bone apatite formation  

PubMed Central

Mineralization is a ubiquitous process in the animal kingdom and is fundamental to human development and health. Dysfunctional or aberrant mineralization leads to a variety of medical problems, and so an understanding of these processes is essential to their mitigation. Osteoblasts create the nano-composite structure of bone by secreting a collagenous extracellular matrix (ECM) on which apatite crystals subsequently form. However, despite their requisite function in building bone and decades of observations describing intracellular calcium phosphate, the precise role osteoblasts play in mediating bone apatite formation remains largely unknown. To better understand the relationship between intracellular and extracellular mineralization, we combined a sample-preparation method that simultaneously preserved mineral, ions, and ECM with nano-analytical electron microscopy techniques to examine osteoblasts in an in vitro model of bone formation. We identified calcium phosphate both within osteoblast mitochondrial granules and intracellular vesicles that transported material to the ECM. Moreover, we observed calcium-containing vesicles conjoining mitochondria, which also contained calcium, suggesting a storage and transport mechanism. Our observations further highlight the important relationship between intracellular calcium phosphate in osteoblasts and their role in mineralizing the ECM. These observations may have important implications in deciphering both how normal bone forms and in understanding pathological mineralization.

Boonrungsiman, Suwimon; Gentleman, Eileen; Carzaniga, Raffaella; Evans, Nicholas D.; McComb, David W.; Porter, Alexandra E.; Stevens, Molly M.



Electrochemical microelectrodes for improved spatial and temporal characterization of aqueous environments around calcium phosphate cements.  


Calcium phosphate compounds can potentially influence cellular fate through ionic substitutions. However, to be able to turn such solution-mediated processes into successful directors of cellular response, a perfect understanding of the material-induced chemical reactions in situ is required. We therefore report on the application of home-made electrochemical microelectrodes, tested as pH and chloride sensors, for precise spatial and temporal characterization of different aqueous environments around calcium phosphate-based biomaterials prepared from ?-tricalcium phosphate using clinically relevant liquid to powder ratios. The small size of the electrodes allowed for online measurements in traditionally inaccessible in vitro environments, such as the immediate material-liquid interface and the interior of curing bone cement. The kinetic data obtained has been compared to theoretical sorption models, confirming that the proposed setup can provide key information for improved understanding of the biochemical environment imposed by chemically reactive biomaterials. PMID:22019519

Gustavsson, J; Ginebra, M P; Planell, J; Engel, E



Effect of calcium carbonate on hardening, physicochemical properties, and in vitro degradation of injectable calcium phosphate cements.  


The main disadvantage of apatitic calcium phosphate cements (CPCs) is their slow degradation rate, which limits complete bone regeneration. Carbonate (CO?²?) is the common constituent of bone and it can be used to improve the degradability of the apatitic calcium phosphate ceramics. This study aimed to examine the effect of calcite (CaCO?) incorporation into CPCs. To this end, the CaCO? amount (0-4-8-12 wt %) and its particle size (12.0-?m-coarse or 2.5-?m-fine) were systematically investigated. In comparison to calcite-free CPC, the setting time of the bone substitute was delayed with increasing CaCO? incorporation. Reduction of the CaCO? particle size in the initial powder increased the injectability time of the paste. During hardening of the cements, the increase in calcium release was inversely proportional to the extent of CO?²? incorporation into apatites. The morphology of the carbonate-free product consisted of large needle-like crystals, whereas small plate-like crystals were observed for carbonated apatites. Compressive strength decreased with increasing CaCO? content. In vitro accelerated degradation tests demonstrated that calcium release and dissolution rate from the set cements increased with increasing the incorporation of CO?²?, whereas differences in CaCO? particle size did not affect the in vitro degradation rate under accelerated conditions. PMID:22213632

Sariibrahimoglu, Kemal; Leeuwenburgh, Sander C G; Wolke, Joop G C; Yubao, Li; Jansen, John A



Microbial phytase-induced calcium-phosphate precipitation--a potential soil stabilization method.  


Two hypotheses were tested: (1) microbial dephosphorylation of phytate in the presence of Ca²+ ions will result in the precipitation of hydroxyapatite-like crystals and (2) precipitation of calcium-phosphate crystals on and between sand-like particles can cause cementation. A growing culture of the dimorphic phytase-active yeast Arxula adeninivorans was introduced into a column filled with quartz particles and subsequently a liquid growth medium amended with calcium phytate was pumped through the column resulting in increased strength and stiffness of the quartz particle matrix. Environmental scanning electron microscope analysis combined with energy-dispersive X-ray measurement revealed cementation of the quartz particles by calcium-phosphate crystals. This microbial mineralization process could provide a novel approach to improving the mechanical properties like strength and stiffness of sandy soils. PMID:21253909

Roeselers, G; Van Loosdrecht, M C M



Zinc-releasing calcium phosphate for stimulating bone formation  

Microsoft Academic Search

Zinc-containing tricalcium phosphate (ZnTCP) is biocompatible and bioactive, and functions as an effective zinc carrier. ZnTCP contains a maximum of 12 mol% of zinc. ZnTCP ceramics and composite ceramics of ZnTCP and hydroxyapatite (ZnTCP\\/HAP) with a (Ca+Zn)\\/P molar ratio of 1.60 were prepared by sintering at 1100 °C. ZnTCP\\/HAP continued to release zinc for more than 50 days in 0.9

Atsuo Ito; Haruo Kawamura; Makoto Otsuka; Masako Ikeuchi; Hajime Ohgushi; Kunio Ishikawa; Kazuo Onuma; Noriko Kanzaki; Yu Sogo; Noboru Ichinose



[Effects of addition of calcium phosphates on the properties of gypsum].  


Calcium hydrogen phosphate (CHP), calcium hydrogen phosphate dihydrate (CHPD) and calcium sulfate dihydrate (gypsum) crystals were added to calcium sulfate hemihydrate as gypsum model materials for improvement of the mechanical properties. The compressive and the bending strength of the hardened mixture were improved by the addition of CHPD, while the addition of CHP and gypsum crystals had no effect. The setting time was markedly reduced by the addition of CHPD, but remarkably increased in the case of CHP crystals. On the other hand, the setting expansion was decreased by the addition of CHP and CHPD crystals. Based on the observation of the surface profile of the calcium sulfate hemihydrate set in contact with glass, and scanning electron microscopy (SEM) of the fractured surface of the hardened mixture, the surface roughness was markedly decreased by the addition of CHPD. When the crystals were added to the metastable solution of calcium sulfate supersaturated with respect to gypsum, the presence of gypsum crystals deposited on the CHPD surface was confirmed by atomic absorption analysis, fourier transform infrared spectroscopy. SEM and electron X-ray microanalysis. Therefore, epitaxial growth of gypsum occurred on the CHPD surface and the addition of CHPD improved the mechanical properties of the gypsum materials. PMID:2135504

Inomata, K



The effect of premixed schedule on the crystal formation of calcium phosphate cement-chitosan composite with added tetracycline  

Microsoft Academic Search

Summary  In this study, calcium phosphate cements (CPC) were prepared by mixing cement powders of tetracalcium phosphate (TTCP) with\\u000a a cement liquid of phosphate acid saline solution. Tetracycline (TTC)-CPC, chitosan-CPC and chitosan-TTC-CPC were investigated\\u000a with different premixed schedule. It was demonstrate that both TTC and chitosan worked on the phase transition and crystal\\u000a characteristics. TTCP mixed with phosphate acid saline solution

Jing Mao; Yan Liu; Bin Zhou; Liyun Yao



Formation of calcium-deficient hydroxyapatite from ?-tricalcium phosphate  

Microsoft Academic Search

This study investigated the factors influencing the kinetics of Ca9HPO4(PO4)5OH (calcium deficient hydroxyapatite or CDHAp) formation from ?-Ca3(PO4)2 (?-TCP). The kinetics of CDHAp formation were investigated by isothermal calorimetry at constant temperatures ranging between 30 and 75°C and by changes in pH at 37.4 and 70°C. The calorimetric curves were characterized by two reaction peaks. Activation energies were calculated for

Kevor S. TenHuisen; Paul W. Brown



Free-standing nanogold membranes as supports for the growth of calcium phosphate crystals.  


Current strategies for bone tissue regeneration focus on the development of implantable matrices that mimic biological tissues. Inorganic composites are of special interest for bone substitute applications. It is necessary to create an artificial three-dimensional scaffold-like porous material with certain geometrical structure to induce bone growth. We report here the growth of calcium phosphate crystals on free-standing carboxylic acid functionalized gold nanoparticle membranes. The gold nanoparticle membrane is synthesized by the spontaneous reduction of aqueous chloroaurate ions by a diamine molecule at a liquid-liquid interface. This membrane is robust and malleable, and most importantly, the gold nanoparticles in the membrane may be functionalized with suitable ligands. In this study, the amino acids aspartic acid and cysteine together with an aromatic bifunctional molecule, anthranilic acid, were used to modify the surface of the gold nanoparticles in the membrane. The free carboxylic acid groups on the gold nanoparticles further to functionalization with these molecules were then used to bind Ca(2+) ions and reacted with phosphate ions to yield calcium phosphate. The nature of the nanogold surface modifier directed the formation of either crystalline hydroxyapatite or amorphous calcium phosphate. The nanogold membrane thus suggests potential biomedical application as biocompatible implants and grafts. PMID:16321063

Rautaray, Debabrata; Sastry, Murali


Effect of heat treatment on pulsed laser deposited amorphous calcium phosphate coatings.  


Amorphous calcium phosphate coatings were produced by pulsed laser deposition from targets of nonstoichiometric hydroxyapatite (Ca/P = 1.70) at a low substrate temperature of 300 degrees C. They were heated in air at different temperatures: 300, 450, 525 and 650 degrees C. Chemical and structural analyses of these coatings were performed using X-ray diffraction (XRD), FTIR, and SEM, XRD analysis of the as-deposited and heated coatings revealed that their crystallinity improved as heat treatment temperature increased. The main phase was apatitic, with some beta-tricalcium phosphate in the coatings heated at 525 and 600 degrees C. In the apatitic phase there was some carbonate substitution for phosphate and hydroxyl ions at 450 degrees C and almost solely for phosphate at 525 and 600 degrees C as identified by FTIR. This was accompanied by a higher hydroxyl content at 525 and 600 degrees C. At 450 degrees C a texture on the coating surface was observable by SEM that was attributable to a calcium hydroxide and calcite formation by XRD. These phases almost disappeared at 600 degrees C, probably due to a transformation into calcium oxide. PMID:9509346

García, F; Arias, J L; Mayor, B; Pou, J; Rehman, I; Knowles, J; Best, S; León, B; Pérez-Amor, M; Bonfield, W



Complexation/encapsulation of green tea polyphenols in mixed calcium carbonate and phosphate micro-particles.  


We used a double-jet mixer to encapsulate water-soluble polyphenols, green tea extract (GTE), with calcium-based inorganic materials. The device mixed calcium chloride solutions with a solution of carbonate and phosphate in the presence of a GTE solution, and formed micro-particles which capture the GTE molecules. The micro-particles were analysed by liquid chromatography coupled to tandem mass spectroscopy to determine the encapsulation yield and loading of the different GTE components. We established correlations between (1) the efficiency of the GTE encapsulation and the composition of the mixed anion solutions and (2) the protonation degree of the ions and the molar ratio of calcium cations and carbonate/phosphate anions. An optimal and reproducible GTE loading of about 40% with an encapsulation yield of 65% was observed for a carbonate/phosphate molar composition of 4?:?1. In addition, our experimental results showed that the process is selective and favours the encapsulation of gallated species which form stronger complexes with calcium cations. PMID:20945969

Elabbadi, Amal; Jeckelmann, Nicolas; Haefliger, Olivier P; Ouali, Lahoussine



Synthesis of some calcium phosphate crystals using the useful biomass for immobilization of microorganisms  

NASA Astrophysics Data System (ADS)

Three sources of biomass generated by primary industry were used as the raw material for the synthesis of calcium phosphate crystals. Phosphoric acid was extracted from burned rice chaff using a 30% nitric acid solution, while scallop shells and gypsum of plasterboard were used as calcium sources. The calcium phosphate crystals were synthesized by a method involving homogeneous precipitation, and the relationship between the composition and shape of the crystals and the pH at the time of the precipitation was investigated. Monetite crystals in a petal form with a diameter ranging from 0.1 to 2 ?m were precipitated at pH 2.0, while granular apatite crystals with a mean diameter of 1 ?m were precipitated at pH 6.0. We also investigated the ability of the synthesized calcium phosphate crystals to immobilize lactic acid bacteria for practical use in industrial bioreactor. It was determined that monetite crystals with a diameter of 2 ?m had the highest ability to fix lactic acid bacteria. The population of lactic acid bacteria was estimated to exceed 1,300 bacteria per crystal surface of 50 ?m2 suggesting that these crystals may be of practical use in industrial fermenters.

Kohiruimaki, T.



Phase evaluation of an effervescent-added apatitic calcium phosphate bone cement.  


Development of macroporosity during setting would allow fast bone ingrowth and good osteointegration of the implant. The interconnected macropores could be created in calcium phosphate cements (CPCs) through the addition of an effervescent porogen mixture to the component of the cements. But this addition could also affect other characteristics of CPCs, such as setting time, mechanical strength, extent of conversion of reactant to apatite phase, crystallinity, and chemical composition of apatite lattice. In this study, these properties were investigated in an effervescent-added calcium phosphate bone cement. From 0 to 20 wt % of an effervescent mixture was added to calcium phosphate cement (CPC) components and phase evaluations were performed after 24 h incubation at 37 degrees C and 28% relative humidity and 1, 3, 7, and 14 days immersion in a specific simulated body fluid. XRD and FTIR techniques were used to characterize the cement composition, crystallinity, and chemical groups in final CPCs. The results showed that addition of effervescent porogen affects the extent of conversion of reactant to apatite phase and crystallinity. In other words, using the effervescent porogen in CPCs could accelerate the rate of conversion of TTCP/DCPA reactant to apatite phase with smaller crystallites, so that it was the predominant phase (about 67%) after only 3 days soaking in SBF solution. The content of carbonate groups substituted for phosphate groups in apatite lattice increased when the effervescent additive was further added. The compressive strength of the set calcium phosphate cement decreased significantly with the addition of the effervescent agent and reached from 8 MPa for additive-free CPC to 1.3 MPa for 20% effervescent-added CPC. The compressive strength was improved after 3 days immersing of CPC in the simulated body fluid solution. PMID:16924623

Hesaraki, Saeed; Moztarzadeh, Fatollah; Solati-Hashjin, Mehran



Factors modulating the pH at which calcium and magnesium phosphates precipitate from human urine.  


The factors controlling the rate at which crystalline bacterial biofilms develop on indwelling bladder catheters are poorly understood. It is known that normally the pH of voided urine (pHv) is lower than the pH at which calcium and magnesium phosphates come out of urine solution (pHn). In patients who develop infections with urease producing bacteria, however, the pHv rises above the pHn and precipitation of the phosphates occurs in the urine and the biofilm. The aim of this study was to examine ways of manipulating the pHn of urine so that more of its calcium and magnesium remain in solution under alkaline conditions. The experimental data show that pHn can be elevated by decreasing the calcium, magnesium and phosphate concentrations. Increasing the fluid intake of a human subject so that the urinary calcium fell from 120 mg/l to 25 mg/l, for example, resulted in the pHn increasing from 6.48 to 8.22. The addition of citrate to urine also produced a rise in the pHn. The daily consumption of 500 ml of fresh orange juice increased urinary citrate concentrations from 0.35 to around 1.21 mg/ml and the pHn rose from 7.24 to 8.2. The pHn of urine is thus a highly variable parameter. It can be manipulated by controlling the urinary concentrations of magnesium, calcium, phosphate and citrate ions. We suggest that increasing fluid intake with citrate containing drinks would reduce the extent of encrustation on catheters in patients infected with urease producing bacteria. PMID:15981006

Suller, M T E; Anthony, V J; Mathur, S; Feneley, R C L; Greenman, J; Stickler, D J



Characterization of calcium phosphate powders originating from Phyllacanthus imperialis and Trochidae Infundibulum concavus marine shells.  


The study reports the preparation and characterization of powders consisting of the different phases of calcium phosphates that were obtained from the naturally derived raw materials of sea-shell origins reacted with H3PO4. Species of sea origin, such as corals and nacres, attracted a special interest in bone tissue engineering area. Nacre shells are built up of calcium carbonate in aragonite form crystallized in an organic matrix. In this work two natural marine origin materials (shells of echinoderm Sputnik sea urchin - Phyllacanthus imperialis and Trochidae Infundibulum concavus mollusk) were involved in the developing powders of calcium phosphate based biomaterials (as raw materials for bone-scaffolds) by hotplate and ultrasound methods. Thermal analyses of the as-prepared materials were made for an assessment of the thermal behavior and heat treatment temperatures. Samples from both sea shells each of them prepared by the above mentioned methods were subjected to thermal treatments at 450 °C and 850 °C in order to evaluate the crystalline transformations of the calcium phosphate structures in the heating process. By X-ray diffraction analyses various calcium phosphate phases were identified. In Sputnik sea urchins originated samples were found predominantly brushite and calcite as a small secondary phase, while in Trochidae I. concavus samples mainly monetite and HA phases were identified. Thermal treatment at 850 °C resulted flat-plate whitlockite crystals - ?-MgTCP [(Ca, Mg)3 (PO4)2] for both samples regardless the preparation method (ultrasound or hotplate) or the targeted Ca/P molar ratio according with XRD patterns. Scanning electron microscopy and Fourier transformed infrared spectroscopy were involved more in the characterization of these materials and the good correlations of the results of these methods were made. PMID:23623070

T?m??an, M; Ozyegin, L S; Oktar, F N; Simon, V



The progress of early phase bone healing using porous granules produced from calcium phosphate cement  

PubMed Central

Objective Bone grafting is a vital component in many surgical procedures to facilitate the repair of bone defects or fusions. Autologous bone has been the gold standard to date in spite of associated donor-site morbidity and the limited amount of available donor bone. The aim of this study was to investigate the progress of bone regeneration and material degradation of calcium phosphate granules (CPG) produced from a calcium phosphate self-setting cement powder compared to the use of autologous bone grafting in the treatment of "critical size defects" on load-bearing long bones of minipigs. Methods A critical size defect in the tibial metaphysis of 16 mini-pigs was filled either with autologous cancellous graft or with micro- and macroporous carbonated, apatic calcium phosphate granules (CPG) produced from a calcium phosphate self-setting cement powder. After 6 weeks, the specimens were assessed by X-ray and histological evaluation. The amount of new bone formation was analysed histomorphometrically. Results The semi-quantitative analysis of the radiological results showed a complete osseous bridging of the defect in three cases for the autograft group. In the same group five animals showed a beginning, but still incomplete bridging of the defect, whereas in the CPG group just two animals developed this. All other animals of the CPG group showed only a still discontinuous new bone formation. Altogether, radiologically a better osseous bridging was observed in the autograft group compared to the CPG group. Histomorphometrical analysis after six weeks of healing revealed that the area of new bone was significantly greater in the autograft group concerning the central area of the defect zone (p < 0.001) as well as the cortical defect zone (p < 0.002). All defects showed new bone formation, but only in the autograft group defects regenerated entirely Conclusions Within the limits of the present study it could be demonstrated that autologous cancellous grafts lead to a significantly better bone regeneration compared to the application of calcium phosphate granules (CPG) produced from a calcium phosphate self-setting cement powder after 6 weeks. In the early phase of bone-healing, the sole application of CPG appears to be inferior to the autologous cancellous grafts in an in vivo critical size defect on load-bearing long bones of mini-pigs.



Physicochemical properties and cytotoxicities of Sr-containing biphasic calcium phosphate bone scaffolds  

Microsoft Academic Search

This study demonstrates a new biomaterial system composed of Sr-containing hydroxyapatite (Sr-HA) and Sr-containing tricalcium\\u000a phosphate (Sr-TCP), termed herein Sr-containing biphasic calcium phosphate (Sr-BCP). Furthermore, a series of new Sr-BCP porous\\u000a scaffolds with tunable structure and properties has also been developed. These Sr-BCP scaffolds were obtained by in situ sintering\\u000a of a series of composites formed by casting various Sr-containing

Guo Dagang; Xu Kewei; Liu Yaxiong



Synthesis and characterization of macroporous chitosan\\/calcium phosphate composite scaffolds for tissue engineering  

Microsoft Academic Search

Chitosan scaffolds reinforced by beta -tricalcium phosphate (beta -TCP)\\u000a and calcium phosphate invert glass were fabricated with a low-cost,\\u000a bioclean freeze-drying technique via thermally induced phase separation.\\u000a The microstructure, mechanical performance, biodegradation, and\\u000a bioactivity of the scaffolds were studied. The composite scaffolds were\\u000a macroporous, and the pore structures of the scaffolds with beta -TCP and\\u000a the glass appeared very different.

Y Zhang; Miqin Zhang



Calcium thorium phosphate (Whitlockite-type mineral). Synthesis and structure refinement  

SciTech Connect

The crystal structure of a new calcium thorium phosphate has been refined by the full-profile Rietveld method using X-ray powder diffraction data. The sample has been synthesized by the sol-gel technique. The phosphate has been identified by X-ray powder diffraction and IR spectroscopy. The refined composition is represented by the formula Ca{sub 10.26}Th{sub 0.12}(PO{sub 4}){sub 7}. The CaO{sub n} and PO{sub 4} polyhedra are distorted compared to the corresponding polyhedra in the basic compound {beta}-Ca{sub 3}(PO{sub 4}){sub 2}.

Orlova, A. I., E-mail: [Lobachevsky State University of Nizhni Novgorod (Russian Federation); Khainakov, S. A. [University of Oviedo (Spain); Loginova, E. E.; Oleneva, T. A. [Lobachevsky State University of Nizhni Novgorod (Russian Federation); Garcia Granda, S. [University of Oviedo (Spain); Kurazhkovskaya, V. S. [Moscow State University (Russian Federation)



Formation of carbonate-apatite crystals after implantation of calcium phosphate ceramics  

Microsoft Academic Search

Summary  The aims of this study were (1) to determine at the crystal level, the nonspecific biological fate of different types of calcium\\u000a phosphate (Ca?P) ceramics after implantation in various sites (osseous and nonosseous) in animals and (2) to investigate the\\u000a crystallographic association of newly formed apatitic crystals with the Ca?P ceramics.\\u000a \\u000a Noncommercial Ca?P ceramics identified by X-ray diffraction as calcium

G. Daculsi; R. Z. LeGeros; M. Heughebaert; I. Barbieux



Calcium Phosphate Nanocomposite Particles for In Vitro Imaging and Encapsulated Chemotherapeutic Drug Delivery to Cancer Cells  

PubMed Central

Paradigm-shifting modalities to more efficiently deliver drugs to cancerous lesions require the following attributes: nanoscale-size, targetability and stability under physiological conditions. Often, these nanoscale drug delivery vehicles are limited due to agglomeration, poor solubility or cytotoxicity. Thus, we have designed a methodology to encapsulate hydrophobic antineoplastic chemotherapeutics within a 20-30 nm diameter, pH-responsive, non-agglomerating, non-toxic calcium phosphate nanoparticle matrix. In the present study, we report on calcium phosphate nanocomposite particles (CPNP) that encapsulate both fluorophores and chemotherapeutics, are colloidally stable in physiological solution for extended time at 37°C and can efficaciously deliver hydrophobic antineoplastic agents, such as ceramide, in several cell model systems.

Kester, Mark; Heakal, Y.; Sharma, A.; Robertson, Gavin P.; Morgan, Thomas T.; I Altinoglu, Erhan; Tabakovic, Amra; Parette, Mylisa R.; Rouse, Sarah; Ruiz-Velasco, Victor; Adair, James H.



Anode glow discharge plasma treatment enhances calcium phosphate adsorption onto titanium plates.  


Glow discharge plasma (GDP) supplied to a cathode (GDP-) has been applied for cleaning, surface activating, and sterilizing biomaterials, because the kinetic energy in the case of the GDP- is larger than that supplied to the anode (GDP+). However, no comparison between GDP+ and GDP- has been reported. In this study, a titanium surface pre-treated with GDP+ and GDP- was characterized by x-ray photoelectron spectroscopy (XPS). In addition, the wettability of the titanium surface was measured with and without GDP. Furthermore, XPS characterized the adsorption of inorganic ions on titanium surfaces with and without GDP and immersed in an electrolyte solution. The findings suggested that GDP+ enhances calcium phosphate nucleation, due to the accumulation of electrons. In addition, calcium phosphate was not nucleated on the specimen with GDP-. We conclude that GDP+ is more suitable for biomineralization on titanium. PMID:12454099

Shibata, Y; Miyazaki, T



Mechanical strength and in vitro antibiotic release profile of antibiotic-loaded calcium phosphate bone cement.  


Some case reports described the usage of bone cement mixed with antibiotics. However, there are few studies that referred to experimental research of calcium phosphate cement with antibiotics. Thus, we mixed vancomycin and amikacin with bone cement in various concentrations and examined its characterization and antibacterial activity. As a result, 6.25 wt% over the concentration could not mix with cement. With an increase in the antibiotic content, the hardening time was prolonged and the compressive strength tended to decrease. In consistency, vancomycin mixed cement increased, whereas amikacin mixed cement decreased. The elution of antibiotics showed sustained release. In conclusion, the characteristics of the bone cement changed based on the amount of antibiotics added, and calcium phosphate cement is useful as a drug carrier. PMID:23851828

Sakamoto, Yoshiaki; Ochiai, Hiroko; Ohsugi, Ikuko; Inoue, Yoshikazu; Yoshimura, Yohko; Kishi, Kazuo



Vertebral body recollapse without trauma after kyphoplasty with calcium phosphate cement.  


Traditionally, immobilization and external bracing has been recommended for patients with type A traumatic and non-osteoporotic fractures that do not present neurological deficits or significant instability. Nevertheless, several authors have recently suggested the possibility to treat thoraco-lumbar and lumbar vertebral compression post-traumatic fractures using standalone balloon kyphoplasty with osteoconductive filler materials, such as calcium phosphate (CPC). Maestretti and Huang have demonstrated the advantages of this technique showing an almost immediate return to daily activities without the inconvenience of wearing a brace, pain reduction, minimal operative risks and maintenance of stability, therefore proposing this as a first-choice technique in young patient needing rapid spine stability. The authors present a case of vertebral body recollapse after kyphoplasty with calcium phosphate cement (CPC) in a 47-year-old man with an A1.2 post-traumatic L1 compression fracture. PMID:21468725

Piazzolla, Andrea; De Giorgi, Giuseppe; Solarino, Giuseppe



Preparation and Sustained-Release Property of Triblock Copolymer/Calcium Phosphate Nanocomposite as Nanocarrier for Hydrophobic Drug  

PubMed Central

The P123/ACP nanocomposite with sizes less than 100 nm consisting of triblock copolymer P123 and amorphous calcium phosphate (ACP) has been prepared by using an aqueous solution containing CaCl2, (NH4)3PO4, and P123 at room temperature. The P123/ACP nanocomposite is used as the nanocarrier for hydrophobic drug ibuprofen, based on the combined advantages of both amphiphilic block copolymer and calcium phosphate delivery system. The P123/ACP nanocomposite has a much higher ibuprofen loading capacity (148 mg/g) than the single-phase calcium phosphate nanostructures. The drug release percentage of the P123/ACP nanocomposite in simulated body fluid reaches about 100% in a period of 156 h, which is much slower than that of single-phase calcium phosphate nanostructures. It is expected that the P123/ACP nanocomposite is promising for the application in the controlled delivery of hydrophobic drugs.



Hybrid Laser/Aerosol Method for the Synthesis of Porous Nanostructured Calcium Phosphate Materials for Bone Tissue Engineering Applications.  

National Technical Information Service (NTIS)

We present a new synthesis method based on laser generation and processing of aerosol particles that can produce calcium phosphate coatings in a porous nanostructured configuration. The process uses laser ablation of crystalline hydroxyapatite targets to ...

H. Kim R. P. Camata S. Brown



Preparation and Sustained-Release Property of Triblock Copolymer/Calcium Phosphate Nanocomposite as Nanocarrier for Hydrophobic Drug  

NASA Astrophysics Data System (ADS)

The P123/ACP nanocomposite with sizes less than 100 nm consisting of triblock copolymer P123 and amorphous calcium phosphate (ACP) has been prepared by using an aqueous solution containing CaCl2, (NH4)3PO4, and P123 at room temperature. The P123/ACP nanocomposite is used as the nanocarrier for hydrophobic drug ibuprofen, based on the combined advantages of both amphiphilic block copolymer and calcium phosphate delivery system. The P123/ACP nanocomposite has a much higher ibuprofen loading capacity (148 mg/g) than the single-phase calcium phosphate nanostructures. The drug release percentage of the P123/ACP nanocomposite in simulated body fluid reaches about 100% in a period of 156 h, which is much slower than that of single-phase calcium phosphate nanostructures. It is expected that the P123/ACP nanocomposite is promising for the application in the controlled delivery of hydrophobic drugs.

Cao, Shao-Wen; Zhu, Ying-Jie; Wu, Jin; Wang, Ke-Wei; Tang, Qi-Li



The transformation of single-crystal calcium phosphate ribbon-like fibres to hydroxyapatite spheres assembled from nanorods  

NASA Astrophysics Data System (ADS)

Two precursors of ribbon-like anhydrous dicalcium phosphate (DCPA) and calcium phosphate fibres were successfully synthesized at 85?°C through a simple and mild pathway from Ca(NO3)2·4H2O and (NH4)2HPO4 upon the hydrolysis of urea. Different molar concentrations of urea resulted in different precursors, including precursor I (DCPA phase) and precursor II (calcium phosphate with DCPA, octacalcium phosphate (OCP) and hydroxyapatite (HAp) phase). By immersing the two precursors in ammonium hydroxide solution (pH = 12), the transformation from precursors to hydroxyapatite could be achieved. X-ray diffraction (XRD) results combined with transmission electron microscopy (TEM) indicated that DCPA fibres (precursor I) were transformed to HAp nanorods in transformation I. In transformation II, dandelion-like spheres assembled by HAp nanorods were obtained from calcium phosphate (precursor II). The mechanisms of transformations I and II are also proposed and discussed based on the XRD and TEM results.

Zhang, Yanjie; Lu, Jinjun



Calcium Gluconate in Phosphate Buffered Saline Increases Gene Delivery with Adenovirus Type 5  

PubMed Central

Background Adenoviruses are attractive vectors for gene therapy because of their stability in vivo and the possibility of production at high titers. Despite exciting preclinical data with various approaches, there are only a few examples of clear efficacy in clinical trials. Effective gene delivery to target cells remains the key variable determining efficacy and thus enhanced transduction methods are important. Methods/Results We found that heated serum could enhance adenovirus 5 mediated gene delivery up to twentyfold. A new protein-level interaction was found between fiber knob and serum transthyretin, but this was not responsible for the observed effect. Instead, we found that heating caused the calcium and phosphate present in the serum mix to precipitate, and this was responsible for enhanced gene delivery. This finding could have relevance for designing preclinical experiments with adenoviruses, since calcium and phosphate are present in many solutions. To translate this into an approach potentially testable in patients, we used calcium gluconate in phosphate buffered saline, both of which are clinically approved, to increase adenoviral gene transfer up to 300-fold in vitro. Gene transfer was increased with or without heating and in a manner independent from the coxsackie-adenovirus receptor. In vivo, in mouse studies, gene delivery was increased 2-, 110-, 12- and 13-fold to tumors, lungs, heart and liver and did not result in increased pro-inflammatory cytokine induction. Antitumor efficacy of a replication competent virus was also increased significantly. Conclusion In summary, adenoviral gene transfer and antitumor efficacy can be enhanced by calcium gluconate in phosphate buffered saline.

Ahonen, Marko T.; Diaconu, Iulia; Pesonen, Sari; Kanerva, Anna; Baumann, Marc; Parviainen, Suvi T.; Spiller, Brad



Incorporation of Casein Phosphopeptide-Amorphous Calcium Phosphate into a Glass-ionomer Cement  

Microsoft Academic Search

Casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) nanocomplexes have been shown to prevent demineralization and promote remineralization of enamel subsurface lesions in animal and in situ caries models. The aim of this study was to determine the effect of incorporating CPP-ACP into a self-cured glass-ionomer cement (GIC). Incorporation of 1.56% w\\/w CPP-ACP into the GIC significantly increased microtensile bond strength (33%) and

S. A. Mazzaoui; M. F. Burrow; M. J. Tyas; S. G. Dashper; D. Eakins; E. C. Reynolds



Treatment of post-orthodontic white spot lesions with casein phosphopeptide-stabilised amorphous calcium phosphate  

Microsoft Academic Search

This study aims to investigate the effect of topical applications of 10% casein phosphopeptide–amorphous calcium phosphate\\u000a (CPP–ACP) on white spot lesions (WSL) detected after treatment with fixed orthodontic appliances. Sixty healthy adolescents\\u000a with ?1 clinically visible WSL at debonding were recruited and randomly allocated to a randomised controlled trial with two\\u000a parallel groups. The intervention group was instructed to topically

Ann Bröchner; Carsten Christensen; Bjarne Kristensen; Sofia Tranæus; Lena Karlsson; Liselotte Sonnesen; Svante Twetman



Effect of microstructural evolution on wettability of laser coated calcium phosphate on titanium alloy  

Microsoft Academic Search

Surface engineering of synthetic implant materials provides an exciting opportunity to mimic natural biomaterials. Surface that are bioactive and textured at multi-scale have the potential for easier osseointegration. Ti alloy surfaces known for their biocompatibility are coated with bioactive calcium phosphate using a laser source at multiple processing speeds. The resulting surface has multi-scale morphology and multi-phase chemical nature. Faster

Anil K. Kurella; Michael Z. Hu; Narendra B. Dahotre



New Low-Temperature Technology of Producing Calcium Feed Phosphate with Microelements  

Microsoft Academic Search

The possibility of producing feed calcium phosphates in a way ensuring a low physical water content in the product was investigated in laboratory conditions. For this purpose the process use of a phosphoric acid solution with a higher (than in conventional methods) P2O5 content (53-63% by wt. P2O5) with CaO (molar fraction of 0.5-0.8) and CaCO3 in the phosphoric acid

Józef Hoffmann


Morphology and composition of nanograde calcium phosphate needle-like crystals formed by simple hydrothermal treatment  

Microsoft Academic Search

Nanograde calcium phosphate needle-like crystals are prepared from wet synthesized Ca-P precipitates by simple hydrothermal treatment at 140°C and 0.3 MPa for 2 h. The morphology of these crystals is observed by transmission electron microscopy (TEM). The phase composition is tested through X-ray diffractometer (XRD) and infrared spectroscopy (IR). It is found that the morphology of these crystals is related

Li Yubao; K. DE GROOT; J. Wijn; C. P. A. T. Klein; S. V. D. Meer



Laser pulse dependent micro textured calcium phosphate coatings for improved wettability and cell compatibility  

Microsoft Academic Search

Surface wettability of an implant material is an important criterion in biological response as it controls the adsorption\\u000a of proteins followed by attachment of cells to its surface. Hence, micro-textured calcium phosphate coatings with four length\\u000a scales were synthesized on Ti–6Al–4V substrates by a laser cladding technique and their effects on wettability and cell adhesion\\u000a were systematically evaluated. Microstructure and

Sameer R. Paital; Wei He; Narendra B. Dahotre



Calcium phosphate coating on magnesium alloy for modification of degradation behavior  

Microsoft Academic Search

Magnesium alloy has similar mechanical properties with natural bone, but its high susceptibility to corrosion has limited\\u000a its application in orthopedics. In this study, a calcium phosphate coating is formed on magnesium alloy (AZ31) to control\\u000a its degradation rate and enhance its bioactivity and bone inductivity. Samples of AZ31 plate were placed in the supersaturated\\u000a calcification solution prepared with Ca(NO3)2,

Fu-zhai Cui; Jing-xin Yang; Yan-peng Jiao; Qing-shui Yin; Yu Zhang; In-Seop Lee



Calcium phosphate formation on plasma immersion ion implanted low density polyethylene and polytetrafluorethylene surfaces  

Microsoft Academic Search

The flexible structure of polymers has enabled them to be useful in a wide variety of medical applications due to the possibility\\u000a to tailor their properties to suit desired applications. For a long time, there has been an increasing interest in utilizing\\u000a polymers as matrices for calcium phosphate-based composites with applications in hard tissue implants. On the other side,\\u000a polymers

Alexey Kondyurin; Emilia Pecheva; Lilyana Pramatarova



An improvement in sintering property of ?-tricalcium phosphate by addition of calcium pyrophosphate  

Microsoft Academic Search

The sintering behavior of calcium pyrophosphate (CPP, Ca2P2O7)-doped ?-tricalcium phosphate [TCP, Ca3(PO4)2], prepared by solid state reaction, was investigated in-situ, using dilatometry. Pure ?-TCP undergoes phase transition to ?-TCP at about 1200°C; hence pure ?-TCP ceramics should be sintered below 1200°C. Pure ?-TCP sintered body can achieve a relative density of only 86% when sintered at 1150°C. However, the addition

Hyun-Seung Ryu; Hyuk-Joon Youn; Kug Sun Hong; Bong-Sun Chang; Choon-Ki Lee; Sung-Soo Chung



Effect of human salivary proteins on the precipitation kinetics of calcium phosphate  

Microsoft Academic Search

Summary  Inhibition of calcium phosphate precipitation in saliva, and prevention of the formation of mineral accretions on tooth surfaces,\\u000a has been ascribed to the existence of inhibiting salivary macromolecules. Marked reductions in the crystal growth rate of\\u000a hydroxyapatite (HA) seeds were measured in supersaturated solutions containing either of two proline-rich proteins, PRP1 or\\u000a PRP3, or statherin; the three macromolecules were isolated

E. C. Moreno; K. Varughese; D. I. Hay



Effect of Microstructural Evolution on Wettability of Laser Coated Calcium Phosphate on Titanium Alloy  

SciTech Connect

Surface engineering of synthetic implant materials provides an exciting opportunity to mimic natural biomaterials. Surface that are bioactive and textured at multi scale have the potential for easier osseointegration. Ti alloy surfaces known for their biocompatibility are coated with bioactive Calcium Phosphate using a laser source at multiple processing speeds. The resulting surface has multiscale morphology and multi-phase chemical nature. Faster processing speeds showed improved wettability to water along with higher degree of crystallinity in the phases present.

Kurella, Anil K [ORNL; Hu, Michael Z. [ORNL; Dahotre, Narendra B [ORNL



Effect of surface morphology of calcium phosphate on osteoblast-like HOS cell responses  

Microsoft Academic Search

Calcium phosphate (CaP) films with different surface roughness are synthesized on a polystyrene surface as a possible candidate for improving the biocompatibility of solid surfaces. These CaP films are used to investigate the influences of the surface roughness and chemical composition on the HOS osteoblast-like cells adhesion, spreading, proliferation, and differentiation. A polystyrene culture plate is used as the control

Woo-Kul Lee; Sang-Mi Lee; Hyun-Man Kim



Preparation of Whole ?-casein by Treatment with Calcium Phosphate Gel1  

Microsoft Academic Search

Preparations of crude whole V-casein, containing approximately 32~ ,\\/-casein, were treated w~th calcium phosphate gel to develop a batch-type procedure for isolation of y-casein. The crude whole V- casein was dissolved to a final concen- tration of 2% in a .02 M potassium phos- phate buffer, pH 6.8, containing 4.5 M urea and .005 M potassium chloride. \\/?- casein contamination

W. N. Eigel; H. E. Randolph



Calcium phosphate stones produced by Madin-Darby canine kidney (MDCK) cells inoculated in nude mice  

Microsoft Academic Search

The canine renal distal tubular cell line Madin-Darby canine kidney (MDCK) forms calcium phosphate microliths during a long-term\\u000a culture in vitro. We identified osteopontin (OPN) and calprotectin (CPT) from a urinary stone matrix. We recently also detected\\u000a the expression of OPN and CPT in MDCK cells. The relationship between the mechanism of the stone formation and these stone\\u000a matrix proteins

Takeshi Sakakura; Keiji Fujita; Takahiro Yasui; Shoich Sasaki; Yoshio Mabuchi; Masanori Iguchi; Kenjiro Kohri



Enhancement of calcium phosphate-mediated transfection by inclusion of adenovirus in coprecipitates  

Microsoft Academic Search

Although coprecipitates of plasmid DNA and calcium phosphate (DNA:CaPi coprecipitates) were one of the first methods used for transfection of mammalian cells, they are inefficient for many cell types. Based on the recent finding that incorporating recombinant adenovirus in CaPi coprecipitates enhances expression of virus-encoded transgenes, we tested the hypothesis that including adenovirus in DNA:CaPi coprecipitates would increase the efficiency

J H Lee; M J Welsh



Mechanism by which calcium phosphate coprecipitation enhances adenovirus-mediated gene transfer  

Microsoft Academic Search

Delivery of a normal copy of CFTR cDNA to airway epithelia may provide a novel treatment for cystic fibrosis lung disease. Unfortunately, current vectors are inefficient because of limited binding to the apical surface of airway epithelia. We recently reported that incorporation of adenovirus in a calcium phosphate coprecipitate (Ad:CaPi) improves adenovirus-mediated gene transfer to airway epithelia in vitro and

R W Walters; M J Welsh



Dehydration of aliphatic alcohols on phosphoric acid catalyst with the addition of calcium phosphate  

Microsoft Academic Search

The kinetic regularities of dehydration of sec- and tert-butyl alcohols on a catalyst consisting of a mixture of calcium phosphate and HâPOâ, deposited on molten quartz were studied by pulsed gas chromatography. At an equal water vapor pressure in the system, the activity of a catalyst consisting of a pure HâPOâ is higher than that of a catalyst with the

P. A. Obraztsov; O. E. Batalin; V. S. Malinskii; L. F. Shubenok; M. I. Vinnik



Physical Properties of Calcium Phosphates Glasses with Various Cao\\/P2O5 Mole Ratios  

Microsoft Academic Search

The physical properties of calcium phosphate glasses with various CaO\\/P2O5 mole ratios, Vicker's surface hardness, weight loss percentage after dipping Ringer's solution were investigated in this study. The best surface hardness of crystallized glass has an average hardness of 670Kg\\/mm and the minmum weight loss percentage of crystallized glass were lower than 1%. The major crystalline phase that developed after

Chung-King Hsu; Jinn-Shing Lee; Jie-Ming Sheu; Chin-Wang Huang



Diphosphonates Inhibit Formation of Calcium Phosphate Crystals in vitro and Pathological Calcification in vivo  

Microsoft Academic Search

Two diphosphonates containing the P-C-P bond, CH3C(OH)(PO3HNa)2 and H2C(PO3HNa)2, inhibit the crystallization of calcium phosphate in vitro and prevent aortic calcification of rats given large amounts of vitamin D3. The diphosphonates therefore have effects similar to those described for compounds containing the P-O-P bond but are active when administered orally.

Marion D. Francis; R. Graham G. Russell; Herbert Fleisch



Effect of increasing the colloidal calcium phosphate of milk on the texture and microstructure of yogurt  

Microsoft Academic Search

The effect of increasing the colloidal calcium phosphate (CCP) content on the physical, rheological, and microstructural properties of yogurt was investigated. The CCP content of heated (85°C for 30min) milk was increased by increasing the pH by the addition of alkali (NaOH). Alkalized milk was dialyzed against pasteurized skim milk at approximately 4°C for 72h to attempt to restore the

T. Ozcan; D. Horne; J. A. Lucey



Controlled formation of calcium-phosphate-based hybrid mesocrystals by organic-inorganic co-assembly  

NASA Astrophysics Data System (ADS)

An understanding of controlled formation of biomimetic mesocrystals is of great importance in materials chemistry and engineering. Here we report that organic-inorganic hybrid plates and even mesocrystals can be conveniently synthesized using a one-pot reaction in a mixed system of protein (bovine serum albumin (BSA)), surfactant (sodium bis(2-ethylhexyl) sulfosuccinate (AOT)) and supersaturated calcium phosphate solution. The morphologies of calcium-phosphate-based products are analogous to the general inorganic crystals but they have abnormal and interesting substructures. The hybrids are constructed by the alternate stacking of organic layer (thickness of 1.31 nm) and well-crystallized inorganic mineral layer (thickness of 2.13 nm) at the nanoscale. Their morphologies (spindle, rhomboid and round) and sizes (200 nm-2 ?m) can be tuned gradually by changing BSA, AOT and calcium phosphate concentrations. This modulation effect can be explained by a competition between the anisotropic and isotropic assembly of the ultrathin plate-like units. The anisotropic assembly confers mesocrystal characteristics on the hybrids while the round ones are the results of isotropic assembly. However, the basic lamellar organic-inorganic substructure remains unchanged during the hybrid formation, which is a key factor to ensure the self-assembly from molecule to micrometre scale. A morphological ternary diagram of BSA-AOT-calcium phosphate is used to describe this controlled formation process, providing a feasible strategy to prepare the required materials. This study highlights the cooperative effect of macromolecule (frame structure), small biomolecule (binding sites) and mineral phase (main component) on the generation and regulation of biomimetic hybrid mesocrystals.

Zhai, Halei; Chu, Xiaobin; Li, Li; Xu, Xurong; Tang, Ruikang



Growth of calcium phosphate on poling treated ferroelectric BaTiO 3 ceramics  

Microsoft Academic Search

Barium titanate (BaTiO3; BTO) is ferroelectric and piezoelectric after poling treatment. In this study, the bioactivity of BTO was investigated after a poling treatment by examining the formation of crystal growth on specimen surfaces in vitro. Negatively charged BTO surfaces showed calcium phosphate (Ca-P) crystal growth, while deposition of sodium chloride was observed on the positively charged BTO surfaces. After

Yeong-Joon Park; Kyu-Seog Hwang; Jong-Eun Song; Joo L Ong; H Ralph Rawls



Calcium Phosphate Nanoparticles: Toxicology and Lymph Node Targeting for Cancer Metastasis Prevention  

Microsoft Academic Search

\\u000a Applications of nanoparticles in biology are rapidly developing areas in nanomedicine. In cancer therapy, nanoparticles are\\u000a being used for the detection, diagnosis, and imaging of tumors. Calcium phosphate has long been used as a bone substitute\\u000a biomaterial and is FDA approved. It is biocompatible, easy to synthesize and relatively cheap. Due to these favorable conditions,\\u000a it has been investigated for

Rajesh A. Pareta


Mechanical evaluation of implanted calcium phosphate cement incorporated with PLGA microparticles  

Microsoft Academic Search

In this study, the mechanical properties of an implanted calcium phosphate (CaP) cement incorporated with 20wt% poly (dl-lactic-co-glycolic acid) (PLGA) microparticles were investigated in a rat cranial defect. After 2, 4 and 8 weeks of implantation, implants were evaluated mechanically (push-out test) and morphologically (Scanning Electron Microscopy (SEM) and histology). The results of the push-out test showed that after 2

Dennis P. Link; Juliette van den Dolder; Wouter J. F. M. Jurgens; Joop G. C. Wolke; John A. Jansen



Mesenchymal stem cell proliferation and differentiation on an injectable calcium phosphate – Chitosan composite scaffold  

Microsoft Academic Search

Calcium phosphate cement (CPC) can be molded or injected to form a scaffold in situ, has excellent osteoconductivity, and can be resorbed and replaced by new bone. However, its low strength limits CPC to non-stress-bearing repairs. Chitosan could be used to reinforce CPC, but mesenchymal stem cell (MSC) interactions with CPC-chitosan scaffold have not been examined. The objective of this

Jennifer L. Moreau; Hockin H. K. Xu



Microbial phytase-induced calcium-phosphate precipitation — a potential soil stabilization method  

Microsoft Academic Search

Two hypotheses were tested: (1) microbial dephosphorylation of phytate in the presence of Ca2+ ions will result in the precipitation of hydroxyapatite-like crystals and (2) precipitation of calcium-phosphate crystals on and between sand-like particles can cause cementation. A growing culture\\u000a of the dimorphic phytase-active yeast Arxula adeninivorans was introduced into a column filled with quartz particles and subsequently a liquid

G. Roeselers; M. C. M. Van Loosdrecht



Microbial phytase-induced calcium-phosphate precipitation: a potential soil stabilization method  

Microsoft Academic Search

Two hypotheses were tested: (1) microbial dephosphorylation of phytate in the presence of Ca2+ ions will result in the precipitation of hydroxyapatite-like crystals and (2) precipitation of calcium-phosphate crystals on and between sand-like particles can cause cementation. A growing culture of the dimorphic phytase-active yeast Arxula adeninivorans was introduced into a column filled with quartz particles and subsequently a liquid

G. Roeselers; M. C. M. Van Loosdrecht



Synthesis, formulation and evaluation of novel zinc-calcium phosphate-based adhesive resin composite cement  

Microsoft Academic Search

Three novel adhesive oligomers having carboxylic acid and methacrylate groups were synthesized, characterized and used to formulate composite bone cements with newly synthesized zinc-calcium-silicate phosphate. The optimal formulation was determined based on types of oligomer, oligomer\\/diluent ratio, initiator concentration, and filler level using compressive strength (CS) and curing time (CT) as screening tools. Shrinkage, exotherm and aging of the formed

Dong Xie; IL-Doo Chung; Guigui Wang; Dingsong Feng; Jimmy Mays



Thermoanalytical and structural characterization of fluoridated calcium phosphates prepared in anhydrous alcohols  

Microsoft Academic Search

A thermoanalytical, morphological, and structural study of fluoridated calcium phosphates that were prepared by different\\u000a variants of a synthesis in anhydrous alcohols is reported. The obtained materials were neither fully amorphous nor single-phased\\u000a crystalline, and their nature considerably depended on the synthesis conditions. In all cases, the retention of significant\\u000a amounts of solvent in the solid product was observed. A

Ricardo G. Simões; Ana I. Aleixo; Ana L. C. Lagoa; Manuel E. Minas da Piedade; João P. Leal; Thorsten Peitsch; Matthias Epple



Bone regeneration with glass ceramic implants and calcium phosphate cements in a rabbit cranial defect model  

Microsoft Academic Search

Hydroxyapatite cement (BoneSource®) and brushite calcium phosphate cement (chronOS™ Inject) were tested for fixation of glass\\u000a ceramic implants (Bioverit®) in experimentally created cranial defects in 24 adult New Zealand White rabbits. Aim of the in\\u000a vivo study was to assess and compare the biocompatibility and osseointegration of the implanted materials. Macroscopic and\\u000a histological evaluations were performed 1 month, 3 months, and 6 months

Gerlind Schneider; Karin Blechschmidt; Dirk Linde; Peter Litschko; Thomas Körbs; Eggert Beleites



Volumetric analysis of osteoclastic bioresorption of calcium phosphate ceramics with different solubilities  

Microsoft Academic Search

Commonly, to determine osteoclastic resorption of biomaterials only the resorbed area is measured. The depth of the resorption pit, however, may also be important for the performance of a material. To generate such data we used two calcium phosphate ceramics (Ca10 and Ca2). The solubility of the materials was determined according to DIN EN ISO 10993-14. They were scanned three-dimensionally

T. Winkler; E. Hoenig; R. Gildenhaar; G. Berger; D. Fritsch; R. Janssen; M. M. Morlock; A. F. Schilling



Calcium phosphate cement delivering zoledronate decreases bone turnover rate and restores bone architecture in ovariectomized rats  

Microsoft Academic Search

Patients sustaining bony fractures frequently require the application of bone graft substitutes to fill the bone defects. In the meantime, anti-osteoporosis drugs may be added in bone fillers to treat osteoporosis, especially in postmenopausal women and the elderly. The effects of zoledronate-impregnated calcium phosphate cement (ZLN\\/CPC) on ovariectomized (OVX) rats were evaluated. OVX rats were implanted with ZLN\\/CPC, containing 0.025

Chang-Chin Wu; Chen-Chie Wang; Dai-Hua Lu; Li-Ho Hsu; Kai-Chiang Yang; Feng-Huei Lin



Treatment of periodontal defects in dogs using an injectable composite hydrogel\\/biphasic calcium phosphate  

Microsoft Academic Search

An injectable composite silanized hydroxypropyl methyl cellulose\\/biphasic calcium phosphate (Si-HPMC\\/BCP) has been investigated\\u000a in humans with promising results. The aim of this study was to evaluate his efficacy for treating periodontal defects (canine\\u000a fenestration and premolar furcation) in dog models. At 3 months, we observed that bone formation around BCP particles in furcation\\u000a model is more discernible but not statistically significant

Xavier StruillouHerveBoutignyZahi; Hervé Boutigny; Zahi Badran; Borhane H. Fellah; Olivier Gauthier; Sophie Sourice; Paul Pilet; Thierry Rouillon; Pierre Layrolle; Pierre Weiss; Assem Soueidan



Effects of 1,25-dihydroxycholecalciferol on fracture healing calcium, phosphate, and zinc in callus and serum  

Microsoft Academic Search

The incorporation of calcium, phosphate, and zinc into the callus of closed tibial fractures was studied in adult rats fed a standard diet. Low doses (60ng\\/kg per day) of 1,25(OH)2D3 5 days a week greatly increased early callus mineralization. This was not related to an increased serum calcium-phosphate molar product but rather to a decreased ratio. The incorporation of zinc

O. Andreen; S.-E. Larsson



Preparation and characterisation of calcium-phosphate porous microspheres with a uniform size for biomedical applications.  


In the present work, a novel route for the preparation of porous ceramic microspheres is described. Two ceramic powders, calcium-titanium-phosphate (CTP) and hydroxyapatite (HAp), were mixed with a sodium alginate solution that enabled the preparation of spherical particles, using the droplet extrusion method combined with ionotropic gelation in the presence of Ca(2+). The spherical particles were subsequently sintered, to burn-off the polymer and obtain calcium-phosphate microspheres with a uniform size and an interconnected porous network. CTP microspheres with diameters ranging from 513 +/- 24 microm to 792 +/- 35 microm and with pores of approximately 40 microm were obtained. HAp microspheres presented diameters of 429 +/- 46 microm and 632 +/- 40 microm and pores of ca. 2 microm. Depending on the formulations tested, the structure of both calcium phosphates may become altered during the sintering process, suggesting that the ratio between the ceramic phase and the polymer solution is a critical parameter. Porous microspheres prepared using the described methodology are promising candidates as bone defect fillers and scaffolds for bone tissue regeneration. PMID:16688586

Ribeiro, C C; Barrias, C C; Barbosa, M A



The effect of porosity on drug release kinetics from vancomycin microsphere/calcium phosphate cement composites.  


The influence of porosity on release profiles of antibiotics from calcium phosphate composites was investigated to optimize the duration of treatment. We hypothesized, that by the encapsulation of vancomycin-HCl into biodegradable microspheres prior admixing to calcium phosphate bone cement, the influence of porosity of the cement matrix on vancomycin release could be reduced. Encapsulation of vancomycin into a biodegradable poly(lactic co-glycolic acid) copolymer (PLGA) was performed by spray drying; drug-loaded microparticles were added to calcium phosphate cement (CPC) at different powder to liquid ratios (P/L), resulting in different porosities of the cement composites. The effect of differences in P/L ratio on drug release kinetics was compared for both the direct addition of vancomycin-HCl to the cement liquid and for cement composites modified with vancomycin-HCl-loaded microspheres. Scanning electron microscopy (SEM) was used to visualize surface and cross section morphology of the different composites. Brunauer, Emmett, and Teller-plots (BET) was used to determine the specific surface area and pore size distribution of these matrices. It could be clearly shown, that variations in P/L ratio influenced both the porosity of cement and vancomycin release profiles. Antibiotic activity during release study was successfully measured using an agar diffusion assay. However, vancomycin-HCl encapsulation into PLGA polymer microspheres decreased porosity influence of cement on drug release while maintaining antibiotic activity of the embedded substance. PMID:21948487

Schnieders, Julia; Gbureck, Uwe; Vorndran, Elke; Schossig, Michael; Kissel, Thomas



Effect of a calcium-phosphate based desensitizer on dentin surface characteristics.  


This study aimed to evaluate the ability of a newly developed calcium-phosphate desensitizer in dentin permeability reduction and its integration with dentin surface before and after immersion in artificial saliva (AS) under two different dentin surface characteristics; with or without the collagen exposure.Humandentin discs treated by EDTA to expose collagen fibrils or EDTA/NaOCl to expose plain dentin surface were subjected to a calcium-phosphate desensitizer (Teethmate Desensitizer; TMD), while non-desensitizer treatment served as control. TMD application showed the occlusion in dentinal tubules and reduction in dentin permeability up to 92%, regardless of dentin surface characteristics. After AS immersion, permeability reduction percent (PR%) significantly increased in EDTA/NaOCl pretreatment (p<0.05). Newly-formed crystallites were observed on desensitizer treated dentin and EDTA/NaOCl pretreatment control group, whereas the crystallites did not exist on EDTA pretreatment control group. Ultrasonication revealed the integration of the calcium-phosphate rich layer of desensitizer on dentin surface after AS immersion. PMID:23903644

Thanatvarakorn, Ornnicha; Nakashima, Syozi; Sadr, Alireza; Prasansuttiporn, Taweesak; Thitthaweerat, Suppason; Tagami, Junji



[Treatment of bony fibrous dysplasia with calcium-phosphate cement: a case report].  


We report successful use of calcium-phosphate cement for the treatment of benign polyostotic fibrous dysplasia in a patient who had undergone several unsuccessful surgical procedures. As no autologous bone was available for further grafting, we used a bone substitute to fill two defects, one in the upper part of the humerus and the other in the radial shaft. The curettage cavity was filled with calcium-phosphate hydroxyapatite cement. The type of bone substitute was chosen for its specific properties: mineral structure similar to bone, microporosity, resistance to compression between cancellous and cortical bone, composition favorable to exchange between the crystals and the interstitial medium. Outcome was favorable early for the shoulder and later for the forearm after surgery for recurrence. Due to progress in the development of diphosphonates, indications for surgery for fibrous dysplasia have been reduced. There remains a risk of recurrence and incomplete results but bone substitute filling can be a useful alternative to autografts and complementary fixation. Calcium-phosphate cement is an easy-to-use paste-like product with interesting physicochemical and biological properties making it a leading choice for bone substitution. PMID:14593290

Liverneaux, P



The use of thermal printing to control the properties of calcium phosphate deposits.  


The objective of this work was to characterize the deposits of calcium phosphate produced by thermal printing in terms of structure, topography and mechanical properties. Hydroxyapatite was molten and directed to (a) a titanium target in relative motion and (b) stationary titanium substrates preheated to 100 degrees C and 350 degrees C. Scanning electron microscopy showed round-like deposits, but high resolution profilometry measured the profile. Micro-Raman spectroscopy and X-ray diffraction characterized the surface for structure, while nanoindentation revealed the hardness and elastic modulus. A symmetrical hemispherical deposit was formed on a surface in slow relative motion, but an off-centre shape formed at a higher relative speed. Deposits on preheated surfaces (100 degrees C and 350 degrees C) were identified as amorphous calcium phosphate. Nanoindentation revealed no significant difference in hardness between the amorphous deposits (4.0-4.4+/-0.3 GPa), but the elastic modulus increased from 65+/-4 GPa (annealed calcium phosphate reference) to 88+/-3 GPa (100 degrees C surface) and then to 98+/-3 GPa (350 degrees C substrate). The large change in elastic modulus is thought to arise from the dehydroxylation during thermal printing. Production of functional materials through crystallization is discussed to extend the range of possible microstructures. The characterization and testing approach is useful for hemispherical deposits produced by printing, coatings (laser ablation, thermal spraying, simulated body fluid) and melt extrusion elements in scaffolds. PMID:20542557

Saber-Samandari, Saeed; Gross, K?rlis A



Europium-doped amorphous calcium phosphate porous nanospheres: preparation and application as luminescent drug carriers  

PubMed Central

Calcium phosphate is the most important inorganic constituent of biological tissues, and synthetic calcium phosphate has been widely used as biomaterials. In this study, a facile method has been developed for the fabrication of amorphous calcium phosphate (ACP)/polylactide-block-monomethoxy(polyethyleneglycol) hybrid nanoparticles and ACP porous nanospheres. Europium-doping is performed to enable photoluminescence (PL) function of ACP porous nanospheres. A high specific surface area of the europium-doped ACP (Eu3+:ACP) porous nanospheres is achieved (126.7 m2/g). PL properties of Eu3+:ACP porous nanospheres are investigated, and the most intense peak at 612 nm is observed at 5 mol% Eu3+ doping. In vitro cytotoxicity experiments indicate that the as-prepared Eu3+:ACP porous nanospheres are biocompatible. In vitro drug release experiments indicate that the ibuprofen-loaded Eu3+:ACP porous nanospheres show a slow and sustained drug release in simulated body fluid. We have found that the cumulative amount of released drug has a linear relationship with the natural logarithm of release time (ln(t)). The Eu3+:ACP porous nanospheres are bioactive, and can transform to hydroxyapatite during drug release. The PL properties of drug-loaded nanocarriers before and after drug release are also investigated.



Spontaneous growth of a laminin-apatite nano-composite in a metastable calcium phosphate solution.  


We have previously reported that a laminin-apatite composite layer is formed on an ethylene-vinyl alcohol copolymer (EVOH) in a laminin-containing calcium phosphate (LCP) solution. In this work, the stability of the LCP solution and growth process of the laminin-apatite composite layer have been investigated. Dynamic light scattering technique revealed that the LCP solution was stable for periods as long as 24 h; it did not induce homogeneous precipitation of laminin or calcium phosphates in the solution. Analysis of the EVOH surface and the LCP solution showed that the laminin-apatite composite layer was formed via coprecipitation of laminin and apatite on the EVOH plate, i.e., spontaneous growing of apatite and simultaneous immobilization of laminin molecules or laminin-calcium phosphate nano-complexes onto its surface. Transmission electron microscopy also revealed that the laminin molecules in the resulting composite layer were not localized or aggregated, but were dispersed on a nano-scale in the entire layer. Because of this nano-composite structure, a large number of laminin molecules were stably immobilized on the EVOH plate. This may be responsible for the excellent cell adhesion properties of this type of composite material. PMID:16024072

Oyane, Ayako; Uchida, Masaki; Onuma, Kazuo; Ito, Atsuo



Self-assembly of filamentous amelogenin requires calcium and phosphate: from dimers via nanoribbons to fibrils.  


Enamel matrix self-assembly has long been suggested as the driving force behind aligned nanofibrous hydroxyapatite formation. We tested if amelogenin, the main enamel matrix protein, can self-assemble into ribbon-like structures in physiologic solutions. Ribbons 17 nm wide were observed to grow several micrometers in length, requiring calcium, phosphate, and pH 4.0-6.0. The pH range suggests that the formation of ion bridges through protonated histidine residues is essential to self-assembly, supported by a statistical analysis of 212 phosphate-binding proteins predicting 12 phosphate-binding histidines. Thermophoretic analysis verified the importance of calcium and phosphate in self-assembly. X-ray scattering characterized amelogenin dimers with dimensions fitting the cross-section of the amelogenin ribbon, leading to the hypothesis that antiparallel dimers are the building blocks of the ribbons. Over 5-7 days, ribbons self-organized into bundles composed of aligned ribbons mimicking the structure of enamel crystallites in enamel rods. These observations confirm reports of filamentous organic components in developing enamel and provide a new model for matrix-templated enamel mineralization. PMID:22974364

Martinez-Avila, Olga; Wu, Shenping; Kim, Seung Joong; Cheng, Yifan; Khan, Feroz; Samudrala, Ram; Sali, Andrej; Horst, Jeremy A; Habelitz, Stefan



Effect of poly(aspartic acid) on calcium phosphate removal from stainless steel tubing under turbulent flow conditions  

NASA Astrophysics Data System (ADS)

Calcium phosphate deposition causes cleaning problems in a number of situations including water treatment, dairy processing, and dental applications. This problem is exacerbated by the limited choices of cleaning chemicals that meet environmental regulations. To promote the development of biodegradable, non-toxic alternatives, this research examines the removal of calcium phosphate deposits consisting of brushite (dicalcium phosphate dihydrate; DCPD) and a mixture of hydroxyapatite (HAP) and DCPD from stainless steel in the presence of poly(aspartic acid) and its sodium salt (PASP). The effects of solvent pH, PASP concentration, and flow rate on the calcium phosphate removal rates are measured from stainless steel tubing under turbulent flow conditions using a solid scintillation detection technique. A mechanistic evaluation of the cleaning data in the absence of PASP indicates that DCPD removal is dominated by shear while HAP/DCPD deposit removal is limited by a combination of mass transfer and interfacial processes. Although the removal mechanisms differ, the results conclusively show that PASP promotes calcium phosphate removal under conditions that favor calcium sequestration in both cases. An in-depth study of DCPD removal in the presence of PASP reveals that this additive is most effective under conditions where calcium sequestration and phosphate protonation occur simultaneously.

Littlejohn, Felicia


Kinetics of phosphate absorption in lactating dairy cows after enteral administration of sodium phosphate or calcium phosphate salts.  


Hypophosphataemia is frequently encountered in dairy cows during early lactation. Although supplementation of P is generally recommended, controversy exists over the suitability of oral P supplementation in animals with decreased or absent rumen motility. Since the effects of transruminal P absorption and the reticular groove reflex on the absorption kinetics of P are not well understood, it is unclear in how far treatment efficacy of oral P supplementation is affected by decreased rumen motility. Phosphate absorption was studied in six phosphate-depleted dairy cows fitted with rumen cannulas and treated with test solutions containing either NaH2PO4 or CaHPO4 with acetaminophen. Each animal was treated orally, intraruminally and intra-abomasally in randomised order. Absorption kinetics of P were studied and compared with the absorption kinetics of acetaminophen, a marker substance only absorbed from the small intestine. Intra-abomasal treatment with NaH2PO4 resulted in the most rapid and highest peaks in plasma inorganic P (Pi) concentration. Oral and intraruminal administration of NaH2PO4 resulted in similar increases in plasma Pi concentration from 4 to 7 h in both groups. Treatment with NaH2PO4 caused more pronounced peaks in plasma Pi concentration compared with CaHPO4. Neither transruminal P absorption nor the reticular groove reflex affected P absorption kinetics as determined by comparing plasma concentration–time curves of P and acetaminophen after administration of 1M-phosphate salt solutions. It is concluded that oral treatment with NaH2PO4 but not CaHPO4 is effective in supplementing P in hypophosphataemic cows with adequate rumen motility. Decreased rumen motility is likely to hamper the efficacy of oral phosphate treatment. PMID:23544958

Grünberg, Walter; Dobbelaar, Paul; Breves, Gerhard



Characterization of a novel calcium phosphate composite bone cement: flow, setting, and aging properties.  


The flow, setting, and aging characteristics of a newly developed calcium phosphate/calcium aluminate composite orthopaedic cement were studied. The effect of vibration on the flow of the cement paste was studied and found to greatly enhance placement. The setting times of this cement were dependent on temperature and decreased with increasing temperatures. At 37 degrees C, the working and setting times were 6.3 +/- 0.3 and 12.8 +/- 0.4 minutes, respectively. Hydration and conversion of the cement phases continued while specimens were stored under simulated, physiological conditions. A cumulative increase in mass of 8.23 +/- 0.65% was observed over a 14 month test period. During this time, the cement was found to expand slightly, 0.71 +/- 0.39%. X-ray diffraction was used to characterize the crystalline phases present during hydration and conversion. The calcium aluminate in the cement hydrated and formed calcium aluminate chloride hydrates, while no changes were observed in the beta-tricalcium phosphate during the testing period. PMID:17122927

Roemhildt, M L; Wagner, S D; McGee, T D



Calcium-strontium mixed phosphate as novel injectable and radio-opaque hydraulic cement.  


Sterile calcium hydrogenophosphate dihydrate (DCPD) (CaHPO(4).2H(2)O), calcium oxide and strontium carbonate powders were mixed in various liquid phases. Among these, ammonium phosphate buffer (0.75 M, pH 6.9) led to a novel strontium-containing calcium phosphate cement. At a 6/2.5/1.5 M ratio and for a liquid to powder ratio (L/P) of 0.5 mlg(-1), the initial paste was fluid and remained injectable for 12 min at 25 degrees C. It was easily obtained by mixing sterile powders and the liquid phase using the push-pull technique, avoiding complex mixing apparatus. The cement set after 15 min at 37 degrees C and was hard after 1h. The compressive strength was in the 20 MPa range, a value higher than that generally assigned to trabecular bone (5-15MPa). This strength appeared sufficient for repairing non-loading sites or reinforcing osteoporotic vertebrae (vertebroplasty). After setting, the initial mixture formed a strontium-calcium-deficient carbonate apatite. The radio-opacity of the resulting cement was three times greater than that of cortical bone because of the presence of strontium ions, a feature that complies with the requirements for vertebroplasty. Furthermore, the cement powder remained stable and retained its properties for at least 4 years. PMID:20144746

Romieu, Guilhem; Garric, Xavier; Munier, Sylvie; Vert, Michel; Boudeville, Philippe



Autophagy Induced by Calcium Phosphate Precipitates Involves Endoplasmic Reticulum Membranes in Autophagosome Biogenesis  

PubMed Central

Calcium can play an important role in the regulation of autophagy. We previously reported that exogenously introduced calcium in the form of calcium phosphate precipitates (CPP) induces autophagy. Here we showed that CPP-induced autophagy required the classical autophagic machinery, including the autophagosome initiating molecules FIP200 and Beclin 1, as well as molecules involved in the autophagosome membrane extension, Atg4, Atg5 and Atg3. On the other hand, Atg9 seemed to place a restriction on CPP-induced autophagy. Loss of Atg9 led to enhanced LC3 punctation and enhanced p62 degradation. CPP-induced autophagy was independent of mTOR and reactive oxygen species. It also did not affect MAP kinase activation and ER stress. DFCP1 is an ER-resident molecule that binds to phosphatidylinositol 3-phosphate. CPP activated DFCP1 punctation in a class III phosphatidylinositol-3-kinase and calcium dependent manner, and caused the association of DFCP1 puncta with the autophagosomes. Consistently, ER membranes, but not Golgi or mitochondrial membranes, colocalized with CPP-induced LC3 positive autophagosomes. These data suggest that CPP-induced autophagosome formation involves the interaction with the ER membrane.

Chen, Xi; Li, Min; Chen, Daohong; Gao, Wentao; Guan, Jun-Lin; Komatsu, Massaki; Yin, Xiao-Ming



Biomimetic fibronectin/mineral and osteogenic growth peptide/mineral composites synthesized on calcium phosphate thin films.  


Composites of fibronectin/mineral and osteogenic growth peptide/mineral were synthesized on calcium phosphate coated substrates immersed in Dulbecco's phosphate-buffered saline solution containing biomolecules. The kinetics of coprecipitation for two biomolecules was similar, and the biomolecules participated in the formation of the crystal latticework and influenced the mineral structure and composition. PMID:21901187

Chen, C; Qiu, Z Y; Zhang, S M; Lee, I-S



Association of serum phosphorus and calcium x phosphate product with mortality risk in chronic hemodialysis patients: A national study  

Microsoft Academic Search

Elevated serum phosphorus is a predictable accompaniment of end-stage renal disease (ESRD) in the absence of dietary phosphate restriction or supplemental phosphate binders. The consequences of hyperphosphatemia include the development and progression of secondary hyperparathyroidism and a predisposition to metastatic calcification when the product of serum calcium and phosphorus (Ca x PO4) is elevated. Both of these conditions may contribute

GA Block; TE Hulbert-Shearon; NW Levin; FK Port



Fabrication of calcium phosphate-calcium sulfate injectable bone substitute using hydroxy-propyl-methyl-cellulose and citric acid.  


In this study, an injectable bone substitute (IBS) consisting of citric acid, chitosan, and hydroxyl propyl methyl cellulose (HPMC) as the liquid phase and tetra calcium phosphate (TTCP), dicalcium phosphate dihydrate (DCPD) and calcium sulfate dehydrate (CSD, CaSO4 x 2H2O) powders as the solid phase, were fabricated. Two groups were classified based on the percent of citric acid in the liquid phase (20, 40 wt%). In each groups, the HPMC percentage was 0, 2, and 4 wt%. An increase in compressive strength due to changes in morphology was confirmed by scanning electron microscopy images. A good conversion rate of HAp at 20% citric acid was observed in the XRD profiles. In addition, HPMC was not obviously affected by apatite formation. However, both HPMC and citric acid increased the compressive strength of IBS. The maximum compressive strength for IBS was with 40% citric acid and 4% HPMC after 14 days of incubation in 100% humidity at 37 degrees C. PMID:20333539

Thai, Van Viet; Lee, Byong-Taek



Application of impedance spectroscopy to evaluate the effect of different setting accelerators on the developed microstructures of calcium phosphate cements  

Microsoft Academic Search

The main goal of the present study was to evaluate the effect of different setting accelerator agents on the developed microstructures\\u000a of calcium phosphate cements (CPCs) by employing the impedance spectroscopy (IS) technique. Six compositions of CPCs were\\u000a prepared from mixtures of commercial dicalcium phosphate anhydrous (DCPA) and synthesized tetracalcium phosphate (TTCP) as\\u000a the solid phases. Two TTCP\\/DCPA molar ratios

H. E. Romeo; P. R. Bueno; M. A. Fanovich



Development of a 3D polymer reinforced calcium phosphate cement scaffold for cranial bone tissue engineering  

NASA Astrophysics Data System (ADS)

The repair of critical-sized cranial bone defects represents an important clinical challenge. The limitations of autografts and alloplastic materials make a bone tissue engineering strategy desirable, but success depends on the development of an appropriate scaffold. Key scaffold properties include biocompatibility, osteoconductivity, sufficient strength to maintain its structure, and resorbability. Furthermore, amenability to rapid prototyping fabrication methods is desirable, as these approaches offer precise control over scaffold architecture and have the potential for customization. While calcium phosphate cements meet many of these criteria due to their composition and their injectability, which can be leveraged for scaffold fabrication via indirect casting, their mechanical properties are a major limitation. Thus, the overall goal of this work was to develop a 3D polymer reinforced calcium phosphate cement scaffold for use in cranial bone tissue engineering. Dicalcium phosphate dihydrate (DCPD) setting cements are of particular interest because of their excellent resorbability. We demonstrated for the first time that DCPD cement can be prepared from monocalcium phosphate monohydrate (MCPM)/hydroxyapatite (HA) mixtures. However, subsequent characterization revealed that MCPM/HA cements rapidly convert to HA during degradation, which is undesirable and led us to choose a more conventional formulation for scaffold fabrication. In addition, we developed a novel method for calcium phosphate cement reinforcement that is based on infiltrating a pre-set cement structure with a polymer, and then crosslinking the polymer in situ. Unlike prior methods of cement reinforcement, this method can be applied to the reinforcement of 3D scaffolds fabricated by indirect casting. Using our novel method, composites of poly(propylene fumarate) (PPF) reinforced DCPD were prepared and demonstrated as excellent candidate scaffold materials, as they had increased strength and ductility and were biocompatible in vitro. Furthermore, 3D PPF reinforced DCPD scaffolds had strengths comparable to trabecular bone. Based on these results, 3D PPF reinforced DCPD scaffolds were evaluated in vivo using a rabbit calvarial defect model. Although bone formation was not enhanced by the addition of mesenchymal stem cells, significant bone ingrowth from the surrounding tissue was observed. The results of this work provide a foundation for future research on 3D polymer reinforced calcium phosphate cement scaffolds.

Alge, Daniel L.


Fabrication and biological characteristics of ?-tricalcium phosphate porous ceramic scaffolds reinforced with calcium phosphate glass  

Microsoft Academic Search

The fabrication process, compressive strength and biocompatibility of porous ?-tricalcium phosphate (?-TCP) ceramic scaffolds\\u000a reinforced with 45P2O5–22CaO–25Na2O–8MgO bioglass (?-TCP\\/BG) were investigated for their suitability as bone engineering materials. Porous ?-TCP\\/BG scaffolds\\u000a with macropore sizes of 200–500 ?m were prepared by coating porous polyurethane template with ?-TCP\\/BG slurry. The ?-TCP\\/BG\\u000a scaffolds showed interconnected porous structures and exhibited enhanced mechanical properties to those

S. Cai; G. H. Xu; X. Z. Yu; W. J. Zhang; Z. Y. Xiao; K. D. Yao



Sphingosine kinase as a regulator of calcium entry through autocrine sphingosine 1-phosphate signaling in thyroid FRTL-5 cells.  


Calcium entry is one of the main regulators of intracellular signaling. Here, we have described the importance of sphingosine, sphingosine kinase 1 (SK1), and sphingosine 1-phosphate (S1P) in regulating calcium entry in thyroid FRTL-5 cells. In cells incubated with the phosphatase inhibitor calyculin A, which evokes calcium entry without mobilizing sequestered intracellular calcium, sphingosine inhibited calcium entry in a concentration-dependent manner. Furthermore, inhibiting SK1 or the ATP-binding cassette ABCC1 multidrug transporter attenuated calcium entry. The addition of exogenous S1P restored calcium entry. Neither sphingosine nor inhibition of SK1 attenuated thapsigargin-evoked calcium entry. Blocking S1P receptor 2 or phospholipase C attenuated calcium entry, whereas blocking S1P receptor 3 did not. Overexpression of wild-type SK1, but not SK2, enhanced calyculin-evoked calcium entry compared with mock-transfected cells, whereas calcium entry was decreased in cells transfected with the dominant-negative G82D SK1 mutant. Exogenous S1P restored calcium entry in G82D cells. Our results suggest that the calcium entry pathway is blocked by sphingosine and that activation of SK1 and the production of S1P, through an autocrine mechanism, facilitate calcium entry through activation of S1P receptor 2. This is a novel mechanism by which the sphingosine-S1P rheostat regulates cellular calcium homeostasis. PMID:19797403

Gratschev, Dan; Löf, Christoffer; Heikkilä, Jari; Björkbom, Anders; Sukumaran, Pramod; Hinkkanen, Ari; Slotte, J Peter; Törnquist, Kid



Molecular mechanism of crystallization impacting calcium phosphate cements  

SciTech Connect

In summary, SPM data has shown that (1) Mg inhibits growth on all steps but relatively high Mg/Ca ratios are needed. Extracting the mechanism of interaction requires more modeling of the kinetic data, but step morphology is consistent with incorporation. (2) Citrate has several effects depending on the citrate/Ca ratio. At the lowest concentrations, citrate increases the step free energy without altering the step kinetics; at higher concentrations, the polar step is slowed. (3) Oxalate also slows the polar step but additionally stabilizes a new facet, with a [100]{sub Cc} step. (4) Etidronate has the greatest kinetic impact of the molecules studied. At 7{micro}M concentrations, the polar step slows by 60% and a new polar step appears. However, at the same time the [10-1]{sub Cc} increases by 67%. It should be noted that all of these molecules complex calcium and can effect kinetics by altering the solution supersaturation or the Ca to HPO{sub 4}{sup 2-} ratio. For the SPM data shown, this effect was corrected for to distinguish the effect of the molecule at the crystal surface from the effect of the molecule on the solution speciation. The goal of this paper is to draw connections between fundamental studies of atomic step motion and potential strategies for materials processing. It is not our intent to promote the utility of SPM for investigating processes in cement dynamics. The conditions are spectacularly different in many ways. The data shown in this paper are fairly close to equilibrium (S=1.6) whereas the nucleation of cements is initiated at supersaturation ratios in the thousands to millions. Of course, after the initial nucleation phase, the growth will occur at more modest supersaturations and as the cement evolves towards equilibrium certainly some of the growth will occur in regimes such as shown here. In addition to the difference in supersaturation, cements tend to have lower additive to calcium ratios. As an example, the additive to Ca ratio is {approx}10{sup -3} to 10{sup -4} for a pyrophosphate based cement (Grover et al., 2006). Where the in situ SPM approach provides unique insights is in providing details of where and how molecules inhibit or accelerate kinetics. This has the potential to aid in designing molecules to target specific steps and to guide synergistic combinations of additives. For example, it is unlikely that bulk techniques could deduce the simultaneous acceleration and inhibition effects of etidronate; or that citrate reduced growth rate by altering step density rather than step speed. In addition, SPM data translates to tractable questions for modelers. The questions changes from 'How does etidronate inhibit brushite growth?' to 'Why does etidronate bind strongly to the [101]{sub Cc} step while it doesn't to the [10-1]{sub Cc} step?' This is still a challenging question but it is far better defined. Given that step chemistries are generally different, it seems reasonable to expect that the greatest inhibition will be achieved not with one, but with several synergistically chosen additives. For example, the most effective growth inhibitors for brushite would target the two fast steps, namely the non-polar, [10-1]{sub Cc} and the polar, [101]{sub Cc} steps. Several molecules have been shown to slow the polar step, with etidronate as the most dramatic example. By contrast, only Mg was observed to slow the [10-1]{sub Cc} step. Thus, a combination of high concentrations of Mg to target the [10-1]{sub Cc} step with low concentrations of etidronate to target the polar steps, should be a more effective combination than either alone. However Mg is not a particularly good inhibitor in the sense that high concentrations are needed, and it is not specific. More ideally, an inhibitor would be designed to interact specifically with the [10-1] step, which would allow the two steps to be independently modified. Again, this provides an opportunity for tighter coupling with theoretical modeling. The question changes from 'What types of molecules will inhibit brushite growth' to 'What type of molecule

Giocondi, J L; El-Dasher, B S; Nancollas, G H; Orme, C A



Optimization of the mineral content in polymeric gels: The effect of calcium to phosphate molar ratio  

NASA Astrophysics Data System (ADS)

The influence of calcium to phosphate (Ca/P) molar ratio on the extent of mineralization in a model (poly)acrylamide gel was investigated under simulated physiological conditions. We hypothesized that the optimal growth of hydroxyapatite crystals will take place at the stoichiometric Ca/P molar ratio of 1.67. Phosphate ions were incorporated during the polymerization of the gel and mineralization was initiated by submersion of the gel in calcium acetate solution. Ca/P molar ratios were varied in the range of 0.5 5.0. The mineralized gel was characterized by Raman spectroscopy, scanning electron microscopy (SEM) and mineral weight fraction analysis via ashing. Raman spectra captured across the bulk of the gels indicated the presence of mineral at the core section. The phosphate symmetric stretching peak was observed in the range of 955 960 cm-1 which is characteristic of hydroxyapatite. SEM images showed that crystals formed at Ca/P=2.0 were denser and larger in size than at other molar ratios. In agreement with SEM images, the dry weight fraction of mineral reached the maximum at the molar ratio of 2.0 and the extent of mineralization rapidly declined as the molar ratio diverged from 2.0. Also, the crystallinity of the mineral was optimum at the molar ratio of 2.0. Thus it appears that for effective mineralization, the molar ratio of the two ions needs to be in excess of the stoichiometric requirement, suggesting that ions are expended in processes other than the formation and growth of hydroxyapatite crystals. Therefore, the optimal level of mineralization in biomimetic-based growth of calcium phosphate crystals in sol gel environment requires consideration of a range of molar ratios as opposed to using the molar ratios corresponding to that of the crystal species intended to grow.

Das, Prasenjit; Akkus, Ozan; Azad, Abdul-Majeed



Umbilical Cord Stem Cell Seeding on Fast-Resorbable Calcium Phosphate Bone Cement  

PubMed Central

Tissue engineering offers immense promise for bone regeneration. Human umbilical cord mesenchymal stem cells (hUCMSCs) can be collected without invasive procedures required for bone marrow MSCs. The objective of this study was to investigate the physical properties and the differentiation capacity of hUCMSCs on calcium phosphate cement (CPC) scaffolds with improved dissolution/resorption rates. CPC consisted of tetracalcium phosphate and dicalcium phosphate anhydrous, with various tetracalcium phosphate/dicalcium phosphate anhydrous ratios. At 1/3 ratio, CPC had a dissolution rate 40% faster than CPC control at 1/1. The faster-resorbable CPC had strength and modulus similar to CPC control. Their strength and modulus exceeded the reported values for cancellous bone, and were much higher than those of hydrogels and injectable polymers for cell delivery. hUCMSCs attached to the nano-apatitic CPC and proliferated rapidly. hUCMSCs differentiated into the osteogenic lineage, with significant increases in alkaline phosphatase activity, osteocalcin, collagen I, and osterix gene expression. In conclusion, in this study we reported that hUCMSCs attaching to CPC with high dissolution/resorption rate showed excellent proliferation and osteogenic differentiation. hUCMSCs delivered via high-strength CPC have the potential to be an inexhaustible and low-cost alternative to the gold-standard human bone marrow mesenchymal stem cells. These results may broadly impact stem-cell-based tissue engineering.

Zhao, Liang; Detamore, Michael S.; Takagi, Shozo; Chow, Laurence C.



In vivo study of calcium phosphate cements: implantation of an ?-tricalcium phosphate\\/dicalcium phosphate dibasic\\/tetracalcium phosphate monoxide cement paste  

Microsoft Academic Search

?-Tricalcium phosphate (?-TCP)\\/dicalcium phosphate dibasic (DCPD)\\/tetracalcium phosphate monoxide (TeCP) cement was implanted in paste form into soft tissue (rate subcutaneous sockets) and bone tissue (defects in rabbit mandibles) to evaluate the setting behaviour of the cement and tissue responses to the cement. A histological study of the soft tissue implants revealed thin fibrous capsule formation, the appearance of multinucleated giant

K. Kurashina; H. Kurita; M. Hirano; A. Kotani; C. P. A. T. Klein; K. de Groot



Calcium and phosphate adsorption as initial steps of apatite nucleation on sol-gel-prepared titania surface.  


Titania powders have been prepared by the sol-gel route from Ti (IV) ethoxide under acidic conditions. Adsorption experiments of calcium and phosphate ions on gel-derived titania suspensions were performed to suggest a likely initial step of apatite growth on its surface. Experiments were performed as a function of time and pH at 37 degrees C with and without NaCl present in the suspensions. Also, zeta (zeta) potential experiments were performed to determine the kind of calcium adsorption. Results suggest that, apparently, calcium and phosphate adsorption can act as two different initial steps for apatite growth. PMID:12483705

Coreño, Juan; Martínez, Antonia; Coreño, Oscar; Bolarín, Ana; Sánchez, Félix



Investigation by infrared absorption spectroscopy into the chemical mechanisms of the wet process synthesis of some calcium phosphates  

NASA Astrophysics Data System (ADS)

The present work describes the reactions of wet process synthesis, of some calcium phosphates, such as tricalcium phosphate (Ca{3}(PO{4})2) and hydroxyapatite (Ca{10}(PO{4})6(OH){2}). These reactions of synthesis are acido-basic reactions between the phosphoric acid (H{3}PO{4}) and calcium carbonates (CaCO{3}).The evolution of these reactions (and the concerned chemical mechanisms) were followed by mid infrared spectroscopy absorption. Indeed, in the first stage of these three reactions in which the medium is strongly acidic, favours the formation of a stable intermediate compound, which is the brushite.During the reaction, the concentration of phosphoric acid decreases, the pH increases and the brushite becomes unstable, thus it evolves to a more stable calcium phosphate under these new pH conditions. This later product was either the tricalcium phosphate or hydroxyapatite, according to the pH solution.

Essaddek, A.; Elgadi, M.; Mejdoubi, E.; Elansari, L. L.; Moradi, K.; Karroua, M.



Effect of casein phosphopeptide-amorphous calcium phosphate and acidulated phosphate fluoride gel on erosive enamel wear  

PubMed Central

Background: Some studies have shown that casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) and acidulated phosphate fluoride (APF) gel can protect teeth against erosion. The aim of this study was to assess whether CPP-ACP and fluoride could reduce enamel wear rates under erosive conditions simulating abrasion and acidic diet regimen. Materials and Methods: Enamel specimens consisted of 3 experimental groups (receiving CPP-ACP, APF or both) and a control group. Specimens were subjected to 5,000 wear cycles at a load of 30 N and a pH of 3 in a tooth wear machine. The amount of wear was determined by stereomicroscope. Data were analyzed using one-way analysis of variance and Tukey post hoc tests (? = 0.05). Results: Mean wear rate (mean±SD) was 194.6±49.2 micrometers in CPP-ACP group, 197.6±39.5 in APF group, 134.6±44.7 in combination group and 266.2± 22.7 in the control group. Statistical analysis indicated significantly higher wear rate in the control group than the experimental groups and also in the CPP-ACP and APF group than the combination group (P<0.05). Conclusions: We concluded that although either CPP-ACP or APF can protect enamel against wear, their combination provides significant enamel wear reduction. These findings would lead to new strategies for the clinical management of tooth wear.

Tehrani, Maryam HajeNorouz Ali; Ghafournia, Maryam; Samimi, Pouran; Savabi, Omid; Parisay, Iman; Askari, Navid; Abtahi, Seyed-Hossein



Gamma-radiation-induced changes in structure and properties of tetracalcium phosphate and its derived calcium phosphate cement.  


The purpose of the present study was to investigate the gamma-radiation effect on the structure and properties of the single-phase tetracalcium phosphate (TTCP) powder and its derived calcium phosphate cement (CPC). Experimental results show that low-dosed (0-30 kGy) CPC has a setting time of 10-12 min, while high-dosed (40-120 kGy) CPC has a setting time of 8-10 min. The low dose gamma-radiation does not significantly change porosity volume fraction or compressive strength of the CPC. The pH values of all CPC samples fell in a relatively narrow band, with a band width of 8.5-9.1 (in terms of pH value). With a dose of 10 or 20 kGy gamma-radiation, the TTCP-apatite conversion ratio does not change much. With 30 kGy the conversion ratio significantly increases and reaches a maximum value. With further increases in dose, the conversion ratio quickly declines. With increasing gamma-ray dose, the CPC morphology becomes more porous/loose and apatite particles become larger in size. When exposed to a high dose (120 kGy) of gamma-radiation, TTCP structure is radiation-damaged, and gamma-ray-induced formation of apatite is confirmed by transmission electron microscopic/selected-area diffraction/lattice imaging analyses. PMID:16850475

Tsai, Chih-Hung; Lin, Jiin-Huey Chern; Ju, Chien-Ping



Plasma Calcium, Inorganic Phosphate and Magnesium During Hypocalcaemia Induced by a Standardized EDTA Infusion in Cows  

PubMed Central

The intravenous Na2EDTA infusion technique allows effective specific chelation of circulating Ca2+ leading to a progressive hypocalcaemia. Methods previously used were not described in detail and results obtained by monitoring total and free ionic calcium were not comparable due to differences in sampling and analysis. This paper describes a standardized EDTA infusion technique that allowed comparison of the response of calcium, phosphorus and magnesium between 2 groups of experimental cows. The concentration of the Na2EDTA solution was 0.134 mol/l and the flow rate was standardized at 1.2 ml/kg per hour. Involuntary recumbency occurred when ionised calcium dropped to 0.39 – 0.52 mmol/l due to chelation. An initial fast drop of ionized calcium was observed during the first 20 min of infusion followed by a fluctuation leading to a further drop until recumbency. Pre-infusion [Ca2+] between tests does not correlate with the amount of EDTA required to induce involuntary recumbence. Total calcium concentration measured by atomic absorption remained almost constant during the first 100 min of infusion but declined gradually when the infusion was prolonged. The concentration of inorganic phosphate declined gradually in a fluctuating manner until recumbency. Magnesium concentration remained constant during infusion. Such electrolyte responses during infusion were comparable to those in spontaneous milk fever. The standardized infusion technique might be useful in future experimental studies.

Mellau, LSB; J?rgensen, RJ; Enemark, JMD



Synthesis and characterization of carbonated hydroxyapatite and bioinspired polymer-calcium phosphate nanocomposites  

NASA Astrophysics Data System (ADS)

Taking the inspiration from natural bone, where collagen provides sites for the nucleation and growth of carbonated hydroxyapatite, we have developed self-assembling calcium phosphate-block copolymer nanocomposites by using a bottom-up approach. In this regard, self-assembling thermo-reversibly gelling block copolymers based on the nonionic, zwitterionic, anionic, block copolymers conjugated to hydroxyapatite-nucleating peptides, and polylysine-polyleucine diblock copoly-peptides were employed as templates for the precipitation of nano-sized calcium phosphates from aqueous solutions. Calcium phosphate nanocrystals were formed at the polymer-inorganic interface presumably nucleated by the ionic interactions. Solid-state NMR, XRD, TEM, TGA, FTIR and X-ray scattering techniques were used to characterize the nanocomposites. NMR and scattering measurements of polymer-inorganic gel composites proved nanocomposite formation and templating by the polymer micelles. The inorganic fraction of the nanocomposites was found to vary between 30-55 wt%. TEM studies showed that the morphology and the size of the hydroxyapatite crystals in the nanocomposites were similar to the apatite in the bone. The findings in our studies provide information for developing guidelines for design of novel HAp-polymer nanocomposites and for the understanding of the mechanism of biomineralization. Moreover, this study may also offer routes for bioinspired bottom-up approaches for the development of a number of nanostructured composites including injectable nanocomposite biomaterials for potential orthopedic applications. As a part of the present study, the carbonate incorporation into the hydroxyapatite lattice under various pH conditions was also investigated. Crystalline sodium and carbonate containing calcium hydroxyapatite (NaCO 3HAp) powders were prepared using an oxidative decomposition of calcium-EDTA chelates in the sodium phosphate solution with hydrogen peroxide. Depending on pH, spherical particles with approximately 3.5 mum in diameter or hexagonal prismatic particles measuring 3 to 9 mum long were obtained. The precipitated particles were a single-phase NaCO3HAp. The carbonate content and the lattice parameters of the hydroxyapatite were a function of solution pH. Maximum carbonate incorporated into the HAp lattice was at pH=10. Formation of HAp on PMMA polymer films was also studied by using the same chelate decomposition method. Evolution of HAp coating as a function of experimental variables including time was examined.

Yusufoglu, Yusuf


Protein kinase A, cytosolic calcium, and phosphate uptake in human proximal renal cells.  


Phosphate uptake by proximal renal cells derived from the human kidney occurs by a saturable process that is approximately 85% dependent on the presence of sodium. Kinetic analysis is consistent with two distinct transport events with Km of 0.08 and 0.63 mM and Vmax of 3.4 and 11.0 min-1, respectively. Parathyroid hormone (PTH), isoproterenol, and prostaglandin E2 (PGE2) increased cellular adenosine 3',5'-cyclic monophosphate (cAMP). PTH-stimulated cAMP prevented binding of the photolabel 8-azido[32P]cAMP with a half-maximal effective concentration (EC50) of 1 nM PTH, 30-fold lower than the EC50 for intracellular cAMP accumulation. These data are qualitatively similar to those observed in OK cells. PTH did not inhibit phosphate uptake in human cells, although it activated cAMP-dependent protein kinase and increased cytosolic calcium. Thus phosphate uptake in human proximal renal cells maintained in short-term culture is unresponsive to PTH in spite of increased cytosolic calcium and activation of the cAMP pathway. PMID:2478035

Middleton, J P; Dunham, C B; Onorato, J J; Sens, D A; Dennis, V W



The application of calcium phosphate precipitation chemistry to phosphorus recovery: the influence of organic ligands.  


This paper describes current knowledge of phosphate precipitation chemistry in the context of phosphorus recovery from wastewaters, and presents experimental results on the effect of organic species, as key potential inhibitors, to the precipitation of calcium phosphate. The supersaturation required for precipitation at 25 degrees C, pH 7, 0.1 M ionic strength and near-stoichiometric (for hydroxylapatite) calcium to phosphate molar ratio was determined under spontaneous precipitation conditions. The experiments were carried out in air. The phase precipitating at the critical concentration was allowed to grow under constant supersaturation. The influence of organic ligands on the precipitation was investigated using two small molecular weight organic ligands, acetate and citrate, present at a concentration of 10(-3) M. The precipitate was studied using X-ray diffraction and scanning electron microscopy. Good reproducibility of the experiments, which were carried out in triplicate, was observed. The study assessed the supersaturation necessary for spontaneous precipitation of hydroxylapatite to be 10.93, calculated using a solubility constant of log K= -57.74. The required supersaturation was not affected by the presence of acetate. However, citrate was found to increase the supersaturation required for precipitation to 11.73. It is likely that this increase is due to binding of citrate on the active growth sites of newly formed nuclei, thereby inhibiting precipitation. All experiments showed formation of a single phase: micro-crystalline hydroxylapatite. PMID:11804354

van der Houwen, J A; Vaisami-Jones, E



Synthesis and characterization of porous nanocrystalline biphasic calcium phosphate for bio applications  

NASA Astrophysics Data System (ADS)

The nano crystalline biphasic calcium phosphates of hydroxyapatite (HAp)/?-tricalcium phosphate (?-TCp) in the ratio 80:20 and 72:28 with interconnected porosity have successfully been prepared by co-precipitation method using mixed catanionic surfactants as template. The sample was calcinated at various temperatures for 8 h. The samples were characterized using X-ray diffraction, Fourier transform infrared spectroscopy, Field emission scanning electron microscopy (FESEM) and thermal analyser. The samples calcinated at 750°C and 850°C show 75% and 89% of crystallinity respectively. Usually to obtain the biphasic calcium phosphates, either the medium will be set as acidic by altering the pH or the Ca/P ratio can be set below the value of 1.5. However this experiment was neither conducted with low Ca/P ratio (<=1.5) nor at low pH (<=7) to obtain the mixed phase. The combination of surfactants and calcination temperature controls the HAp/?-TCp ratio.

Shanthi, P. Michael S. L.; Ashok, M.; Balasubramanian, T.



Solid-liquid adsorption of calcium phosphate on TiO{sub 2}  

SciTech Connect

Calcium phosphate (CP) in aqueous solution was exposed to thin-film TiO{sub 2} surfaces at predetermined times ranging from 10 min to 20 h using a liquid reaction apparatus (LRA). Surface analysis was then performed using X-ray photoelectron (XPS) and Auger electron (AES) spectroscopies and time-of-flight secondary ion mass spectromemtry (ToF-SIMS) with polyatomic primary ions. XPS revealed that CP nucleated and grew on the TiO{sub 2} surface, with phosphate groups growing on top of an initial 2-dimensional (2D) Ca-rich layer. AES depth profiling of a 4-h solution exposure complemented this finding and gave additional evidence for 3-dimensional (3D) phosphate islands forming on top of the calcium. ToF-SIMS analysis of CP adsorbed on the surface indicated that the predominant phase on the surface was brushite, CaHPO{sub 4}{sm{underscore}bullet}2H{sub 2}O. A model for Ca{sup 2+} cation bridging at the oxide interface is proposed.

Chusuei, C.C.; Goodman, D.W.; Stipdonk, M.J. van; Justes, D.R.; Loh, K.H.; Schweikert, E.A.



Some studies on calcium phosphate embedded in polyvinyl alcohol matrix before and after ?-irradiation  

NASA Astrophysics Data System (ADS)

The Ca-P ratio in polymer matrix was adjusted to 1.67 as in hydroxyapatite. The complexed polyvinyl alcohol (PVA) materials exhibit the characteristic absorption bands of phosphate at 601 and 962 cm-1 indicating the presence of (HPO4)-1 anions in the structure. The X-ray diffraction (XRD) revealed that the reaction between Ca and P ions in the PVA medium has a great effect on polymeric matrix crystallization. After irradiation, XRD results for sample c showed more sharp peaks indicating that irradiation can break the principal chemical bonds and favoring additional crystallization processes and therefore the crystallinity increases. An improvement in the thermal stability of PVA doped with calcium phosphate could be seen with the increase of calcium phosphate intercalated with PVA. The surfaces of films were analyzed by scanning electron microscope (SEM) before and after ?-irradiation. The formation of hydroxyapatite is confirmed by energy dispersive X-ray spectroscopy (EDX analysis). The electric conduction data were interpreted on the basis of an intrachain one-dimensional interpolaron hopping model of Kuivalainen.

Abdelrazek, E. M.; El Damrawi, G.; Al-Shahawy, A.



Porous hydroxyapatite and biphasic calcium phosphate ceramics promote ectopic osteoblast differentiation from mesenchymal stem cells  

NASA Astrophysics Data System (ADS)

Because calcium phosphate (Ca-P) ceramics have been used as bone substitutes, it is necessary to investigate what effects the ceramics have on osteoblast maturation. We prepared three types of Ca-P ceramics with different Ca-P ratios, i.e. hydroxyapatite (HA), beta-tricalcium phosphate (?-TCP), and biphasic calcium phosphate (BCP) ceramics with dense-smooth and porous structures. Comprehensive gene expression microarray analysis of mouse osteoblast-like cells cultured on these ceramics revealed that porous Ca-P ceramics considerably affected the gene expression profiles, having a higher potential for osteoblast maturation. In the in vivo study that followed, porous Ca-P ceramics were implanted into rat skeletal muscle. Sixteen weeks after the implantation, more alkaline-phosphatase-positive cells were observed in the pores of hydroxyapatite and BCP, and the expression of the osteocalcin gene (an osteoblast-specific marker) in tissue grown in pores was also higher in hydroxyapatite and BCP than in ?-TCP. In the pores of any Ca-P ceramics, 16 weeks after the implantation, we detected the expressions of marker genes of the early differentiation stage of chondrocytes and the complete differentiation stage of adipocytes, which originate from mesenchymal stem cells, as well as osteoblasts. These marker gene expressions were not observed in the muscle tissue surrounding the implanted Ca-P ceramics. These observations indicate that porous hydroxyapatite and BCP had a greater potential for promoting the differentiation of mesenchymal stem cells into osteoblasts than ?-TCP.

Zhang, Lingli; Hanagata, Nobutaka; Maeda, Megumi; Minowa, Takashi; Ikoma, Toshiyuki; Fan, Hongsong; Zhang, Xingdong



Biomineralization and Size Control of Stable Calcium Phosphate Core Protein Shell Nanoparticles: Potential for Vaccine Applications  

PubMed Central

Calcium phosphate (CaP) polymorphs are nontoxic, biocompatible and hold promise in applications ranging from hard tissue regeneration to drug delivery and vaccine design. Yet, simple and robust routes for the synthesis of protein-coated CaP nanoparticles in the sub-100 nm size range remain elusive. Here, we used cell surface display to identify disulfide-constrained CaP binding peptides that, when inserted within the active site loop of E. coli Thioredoxin 1 (TrxA), readily and reproducibly drive the production of nanoparticles that are 50–70 nm in hydrodynamic diameter and consist of an approximately 25 nm amorphous calcium phosphate (ACP) core stabilized by the protein shell. Like bone and enamel proteins implicated in biological apatite formation, peptides supporting nanoparticle production were acidic. They also required presentation in a loop for high affinity ACP binding since elimination of the disulfide bridge caused a nearly 3-fold increase in hydrodynamic diameters. When compared to a commercial aluminum phosphate adjuvant, the small core-shell assemblies led to a 3-fold increase in mice anti-TrxA titers three weeks post-injection, suggesting that they might be useful vehicles for adjuvanted antigen delivery to dendritic cells.

Chiu, David; Zhou, Weibin; Kitayaporn, Sathana; Schwartz, Daniel T.; Murali-Krishna, Kaja; Kavanagh, Terrance J.; Baneyx, Francois



The properties of biomimetically processed calcium phosphate on bioactive ceramics and their response on bone cells.  


This study looks for grounds to alter the chemical composition (phosphate, calcium, silica and carbonate), dissolution properties, structure and nanotopography of the biomimetically processed surfaces on bioactive ceramics to optimize their shown ability to influence bone cell behaviour and production of new bone. In the bone environment desirable characteristic of these materials is their ability to be remodeled by natural osteoclastic resorption. Different silica and carbonate containing calcium phosphate layers were prepared on bioactive glasses 9 (S53P4) and 1-98 (S53P2) and sol-gel processed pure silica SiO2 in C- and R-SBF (conventional and revised simulated body fluid) for varying periods of time. It was shown that in R-SBF the CaP layer formed faster compared to C-SBF. The CaP layer in the R-SBF contained more carbonate (CO3(2-)) compared to that formed with the same immersion time in C-SBF. The CaP so formed in R-SBF with faster precipitation is more amorphous than the bonelike HCA formed in C-SBF. The results indicate that the most suitable surface for both osteoblasts and osteoclasts was found to be an amorphous CaP having mesoporous nanotopography and proper dissolution rate of calcium and silica. PMID:17122926

Vaahtio, M; Peltola, T; Hentunen, T; Ylänen, H; Areva, S; Wolke, J; Salonen, J I



In vitro biological effects of titanium rough surface obtained by calcium phosphate grid blasting.  


Surface roughness modulates the osseointegration of orthopaedic and dental titanium implants. High surface roughness are currently obtained by blasting of titanium implants with silica or aluminium oxide abrasive particles. This process may cause the release of cytotoxic silicium or aluminium ions in the peri-implant tissue. To generate a biocompatible roughened titanium surface, we currently develop an innovative grid-blasting process using biphasic calcium phosphate (BCP) particles. Titanium alloy (Ti6Al4V) discs were either polished, BCP grid-blasted or left as-machined. BCP grid-blasting created an average surface roughness of 1.57 +/- 0.07 microm compared to the original machined surface of 0.58 +/- 0.05 microm. X-ray photoelectron spectroscopy indicated traces of calcium and phosphorus and relatively less aluminium on the BCP grid-blasted surface than on the initial titanium specimen. Scanning electronic microscopy observations and measurement of mitochondrial activity (MTS assay) showed that osteoblastic MC3T3-E1 cells were viable in contact with the BCP grid-blasted titanium surface. In addition, our results indicate that MC3T3-E1 cells expressed ALP activity and conserved their responsiveness to bone morphogenetic protein BMP-2. The overall results clearly indicate that this calcium phosphate grid-blasting technique increases the roughness of titanium implants and provides a non-cytotoxic surface with regard to mouse osteoblasts. PMID:15207462

Citeau, Anthony; Guicheux, Jerome; Vinatier, Claire; Layrolle, Pierre; Nguyen, Thien P; Pilet, Paul; Daculsi, Guy



Osteogenesis-inducing calcium phosphate nanoparticle precursors applied to titanium surfaces.  


This study investigated the effects of the morphology and physicochemical properties of calcium phosphate (CaP) nanoparticles on osteogenesis. Two types of CaP nanoparticles were compared, namely amorphous calcium phosphate (ACP) nano-spheres (diameter: 9-13 nm) and poorly crystalline apatite (PCA) nano-needles (30-50 nm × 2-4 nm) that closely resemble bone apatite. CaP particles were spin-coated onto titanium discs and implants; they were evaluated in cultured mouse calvarial osteoblasts, as well as after implantation in rabbit femurs. A significant dependence of CaP coatings was observed in osteoblast-related gene expression (Runx2, Col1a1 and Spp1). Specifically, the PCA group presented an up-regulation of the osteospecific genes, while the ACP group suppressed the Runx2 and Col1a1 expression when compared to blank titanium substrates. Both the ACP and PCA groups presented a more than three-fold increase of calcium deposition, as suggested by Alizarin red staining. The removal torque results implied a slight tendency in favour of the PCA group. Different forms of CaP nanostructures presented different biologic differences; the obtained information can be used to optimize surface coatings on biomaterials. PMID:23558249

He, Wenxiao; Andersson, Martin; de Souza, Pedro Paulo Chaves; de Souza Costa, Carlos Alberto; Muñoz, Eduardo Mariscal; Schwartz-Filho, Humberto Osvaldo; Hayashi, Mariko; Hemdal, Amanda; Fredel, Axel; Wennerberg, Ann; Jimbo, Ryo



In-Situ Cold Temperature XRD of Calcium Phosphate Produced From Organic Phosphoric Acid  

NASA Astrophysics Data System (ADS)

In this study, we synthesized calcium phosphate from an organic phosphoric acid, diethylhexyl phosphoric acid (DEHPA) and calcium hydroxide solution. The reaction involves a sol-gel process with a whitish gel formed. In-situ XRD analysis was then performed on the sample from room temperature to -140° C. At room the XRD diffractogram shows the sample as an amorphous material and as the temperature was further lowered sharp peaks begins to form indicating that the material had becomes crystalline. The peaks were identified to be that calcium hydrogen phosphate (Ca(H2PO4)2) and this indicates that there is no hydroxyl group removal during the cooling process. The relative crystallinity values obtained for the different cooling temperatures show a slow exponential increase on the initial cooling of 0 to -100° C and at further cooling temperatures resulted fast and linear process. Also unlike the in-situ XRD analysis performs at high temperature no phase transformation occurred at this low temperature.

Yusoff, M. S. Meor; Paulus, Wilfred; Muslimin, Masliana



Renal transport of bisphosphonates: accumulation by renal cortical slices enhanced by calcium phosphate ions  

SciTech Connect

Bisphosphonates have been recognized as useful therapeutic agents in metabolic bone disease. Earlier studies showed a net renal secretion of 1-hydroxy-ethylidene-1,1-bisphosphonate (HEBP). They suggested a renal cellular uptake of this compound. The authors further studied this concept by investigating the uptake in vitro of /sup 14/C-HEBP by rat renal cortex slices. HEBP was accumulated against a concentration gradient, a process that was dependent on time, temperature, and substrate concentration. Unlike that of /sup 3/H-p-aminohippurate, the uptake was not affected by change in medium Na+ or glucose and acetate concentration, or by anoxia and various metabolic inhibitors. It was, however, markedly increased by raising the medium calcium and inorganic phosphate concentration. Equilibrium dialysis with renal cortex homogenates suggests that HEBP binds to a cytosolic macromolecule through a process that exhibits saturability and calcium dependency. In conclusion, the results suggest that the bisphosphonate HEBP can penetrate kidney cells by a process that does not appear to be energy dependent, but is markedly influenced by the extracellular calcium-phosphate concentration.

Troehler, U.; Bonjour, J.P.; Fleisch, H.



Comparison between ATP-supported and GTP-supported phosphate turnover of the calcium-transporting sarcoplasmic reticulum membranes.  


The study deals with the interrelationship of the phosphate-transferring activities of the calcium-transporting sarcoplasmic reticulum membrane vesicles: the phosphate exchange between nucleoside triphosphate (NTP) and nucleoside diphosphate (NDP) (NTP-NDP exchange), the calcium-dependent NTase, and the phosphorylation of NDP by inorganic phosphate in the presence of NTP (NTP-Pi exchange). Different nucleotides were used as phosphate donors and acceptors. It is demonstrated for the phosphate transfer from ITP to GDP that the NTP-NDP exchange exhibits ping-pong kinetics with Mg-ITP and unliganded GDP as substrates. The apparent affinities of the enzyme for the nucleoside diphosphate and triphosphate species are deduced according to this mechanism. The enzyme's affinity for the nucleoside triphosphates and diphosphates depends on its functional state being considerably lower under conditions of NTP-NDP exchange than during NTP splitting or NTP synthesis. ATP and GTP are split with the same low rates when calcium-activated NTPase is inhibited by high internal calcium concentrations after calcium transport has reached steady state. The rates of the NTP-NDP exchange reactions, however, differ by a factor of about 10 being approximately equal to 3 mumol . mg-1 . min-1 for ATP-ADP and only approximately equal to 0.3 mumol . mg-1 . min-1 (22 degrees C) for GTP-GDP. When the sarcoplasmic reticulum vesicles are made calcium-permeable, the calcium transport ATPase is turned on and the rates of GTP and ATP splitting increase about tenfold. Yet, while the rate of ATP-ADP exchange is little reduced, the rate of GTP-GDP exchange drops by approximately 50%. The persisting exchange activity of calcium-permeable vesicles demonstrates that high internal calcium concentrations are not required for the transfer of the protein-bound phosphoryl group to NDP during NTP-NDP exchange. PMID:160316

Ronzani, N; Migala, A; Hasselbach, W



Microwave assisted synthesis & properties of nano HA-TCP biphasic calcium phosphate  

NASA Astrophysics Data System (ADS)

Biphasic calcium phosphate (BCP) nanopowders were synthesized by using microwave and non-microwave irradiation assisted processes. The synthesized powders were pressed under a pressure of 90 MPa, and then were sintered at 1000-1200°C for 1 h. The mechanical properties of the samples were investigated. The formed phases and microstructures were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that the synthesis time was shorter, along with a more homogeneous microstructure, when the microwave irradiation assisted method was applied. The compression strength and the Young's modulus of the samples synthesized with microwave irradiation were about 60 MPa and 3 GPa, but those of the samples synthesized without microwave irradiation were about 30 MPa and 2 GPa, respectively. XRD patterns of the microwave irradiation assisted and non-microwave irradiation assisted nanopowders showed the coexistence of hydroxyapatite (HA) and tricalcium phosphate (TCP) phases in the system.

Ghomash Pasand, E.; Nemati, A.; Solati-Hashjin, M.; Arzani, K.; Farzadi, A.



Characterization of Wet Powder-Sprayed Zirconia/Calcium Phosphate Coating for Dental Implants.  


PURPOSE: Yttria-stabilized zirconia (TZ) is used for dental applications because of its low toxicity and beneficial mechanical properties, but it does not stimulate bone regeneration around the implant due to its bioinertness. Therefore, hydroxyapatite (HA) coatings are often utilized to increase the surface bioactivity and to achieve a better osseointegration. These coatings, however, are chemically nonstable and provide a weak bonding to the substrate surface. MATERIALS AND METHODS: In this study, zirconia substrates were coated with a calcium phosphate/zirconia mixture to achieve ceramic coatings with a high bioactivity potential and a good mechanical stability. The coatings were obtained by wet powder spraying (WPS). Pure HA and TZ coatings were employed as reference materials. The coatings were characterized with regard to microstructure, surface roughness, and phase composition. Scratch tests were carried out to investigate the coating adhesion. The influence of the coating on the mechanical strength was evaluated with the ball on three balls test (B3B). In addition, zirconia dental implant screws were also coated and inserted in a biomechanical test block and bovine rip bone. RESULTS: After sintering, the mixed coating exhibited a porous morphology with a surface roughness of about 4??m and a total porosity of 17%. Phase analysis showed a transformation from TZ and HA to calcium zirconium oxide and tricalcium phosphate. Investigations of the bond strength confirmed a strong adhesion of the mixed coating to the substrate, while the biaxial fracture strength was only slightly affected. Insertion experiments confirmed the scratch test results and evidenced an intact mixed coating on the zirconia screw. CONCLUSIONS: The present study revealed a higher stability and firm adhesion of the mixed coating compared with a pure calcium phosphate coating. We also successfully demonstrate the particular versatility of the WPS technique for dental implants by coating a complex curved surface. PMID:23574454

Pardun, Karoline; Treccani, Laura; Volkmann, Eike; Li Destri, Giovanni; Marletta, Giovanni; Streckbein, Philipp; Heiss, Christian; Rezwan, Kurosch



The properties of sintered calcium phosphate with [ca]/[p] = 1.50.  


In order to obtain the properties of the sintered as-dried calcium phosphate with [Ca]/[P] = 1.50, the characteristics of sintered pellets have been investigated using X-ray diffraction (XRD), inductively coupled plasma-mass spectrometry (ICP-MS), Fourier-transform infrared (FT-IR) spectra, Vickers hardness indentation and scanning electron microscopy (SEM). When the pellet samples were sintered between 700 °C and 1200 °C for 4 h, the hydroxyapatite (Ca(10)(PO(4))(6)(OH)(2), HA) still maintained the major phase, accompanied with the rhenanite (NaCaPO(4)) as the secondary phase and ?-tricalcium phosphate (?-Ca(3)(PO(4))(2), ?-TCP) as the minor phases. In addition, the HA partially transformed to ?-tricalcium phosphate (?-Ca(3)(PO(4))(2), ?-TCP) and tetracalcium phosphate (Ca(4)(PO4)(2)O, TTCP), when the pellet samples were sintered at 1300 °C and 1400 °C, respectively, for 4 h. The maximum density and Vickers Hardness (HV) of sintered pellet samples were 2.85 g/cm3 (90.18% theoretical density (T.D.)) and 407, which appeared at 1200 °C and 900 °C, respectively. PMID:23202968

Hung, I-Ming; Shih, Wei-Jen; Hon, Min-Hsiung; Wang, Moo-Chin



The effect of calcium phosphate ceramic composition and structure on in vitro behavior. II. Precipitation.  


The formation of a biologically equivalent carbonate-containing apatite on the surface of synthetic calcium phosphate ceramics (CPC) may be an important step leading to bonding with bone. Reactions of several single phases CPCs upon immersion into a simulated physiologic solution (SPS) with an electrolyte composition of human plasma were determined. The CPCs covered a wide range of solution stabilities from low-soluble hydroxyapatites (HA) to metastable tricalcium phosphates (TCP) and tetracalcium phosphate (TTCP). Changes in chemical compositions of SPS and infrared spectral features after CPC immersion were analyzed. New phase formation was observed on all the CPCs. However, kinetics, compositions, and structures of the new phases were significantly different. The studied CPCs can be characterized by the time to new phase formation in vitro; the minimum time for measurable precipitate formation was found to increase in the order: not-well-crystallized HAs < well-crystallized HAs < alpha-TCP, TTCP < beta-TCP. Among the CPCs only not-well-crystallized HAs led to immediate new phase formation. The metastable CPCs, beta-TCP, alpha-TCP, and TTCP required an induction time during which dissolution occurred. beta-TCP showed the longest induction time and the lowest lattice ion uptake rate of all the CPCs tested. Only the not-well-crystallized HAs elicited immediate formation of carbonated HA. The well-crystallized HAs and beta-TCP did not elicit carbonated apatite formation within the time frame of the experiment. Instead, intermediate phases were formed. On alpha-TCP amorphous calcium phosphate (ACP) with a relatively low carbonate content was formed. TTCP was found to transform extensively to poorly crystallized carbonated apatite after 2 days of immersion. PMID:8380597

Radin, S R; Ducheyne, P



Fabrication of multilayer ZrO?-biphasic calcium phosphate-poly-caprolactone unidirectional channeled scaffold for bone tissue formation.  


We developed a continuously porous scaffold with laminated matrix and bone-like microstructure by a multi-pass extrusion process. In this scaffold, tetragonal ZrO?, biphasic calcium phosphate and poly-caprolactone layers were arranged in a co-axially laminated unit cell with a channel in the center. The entire matrix phase had a laminated microstructure of alternate lamina of tetragonal ZrO?, biphasic calcium phosphate and poly-caprolactone--biphasic calcium phosphate with optimized designed thickness and channeled porosity. Each of the continuous pores was coaxially encircled by the poly-caprolactone--biphasic calcium phosphate layer, biphasic calcium phosphate layer and finally tetragonal ZrO? layer, one after the other. Before extrusion, 5?vol% graphite powder was mixed with tetragonal ZrO? to ensure pores in the outer layer and connectivity among the lamellas. The design strategy is aimed to incorporate a lamellar microstructure like the natural bone in the macro-scaled ceramic body to investigate the strengthening phenomenon and pave the way for fabricating complex microstructure of natural bone could be applied for whole bone replacement. The final fabricated scaffold had a compressive strength of 12.7?MPa and porosity of 78?vol% with excellent cell viability, cell attachment and osteocalcin and collagen expression from cultured MG63 cells on scaffold. PMID:23064831

Mondal, Dibakar; So-Ra, Son; Sarkar, Swapan Kumar; Min, Young Ki; Yang, Hun Mo; Lee, Byong Taek



Purification and characterization of a rabbit salivary protein, a potent inhibitor of crystal growth of calcium phosphate salts.  


Human saliva is supersaturated with respect to basic calcium phosphate salts but is stabilized by specific macromolecules that inhibit calcium phosphate precipitation. One of the families of inhibitory proteins in human and monkey saliva is the acidic proline-rich proteins. The purpose of this study was to isolate and characterize inhibitors of calcium phosphate precipitation from rabbit parotid saliva. Saliva was fractionated by immunoaffinity chromatography and anion exchange chromatography. Individual fractions were assayed for their ability to inhibit calcium phosphate crystal growth and the fraction associated with the inhibition was purified by repeated anion exchange chromatography, preparative gel electrophoresis and electroelution. A major (APRP) and two minor proteins (AM1, AM2) that were inhibitory were purified. APRP is an acidic proline-rich phospho-glycoprotein and a very potent inhibitor of secondary crystal growth of calcium phosphate as it was active at a concentration of 2 x 10(-8) M in a standard assay. The N-terminal sequence of one APRP was EYENLDGSLAATQNDDD?Q and a clostripain fragment of APRP had the following N-terminal sequence PQHRPPRPGGH-????SPPP?GN???PPP. Although the N-terminal segment of APRP does not resemble that of proline-rich proteins, alignment of the clostripain fragment with the repeat region of such proteins from rat, mouse, monkey and man revealed a high degree of similarity, indicating a structural relationship with the proline-rich protein family. PMID:2012527

Spielman, A I; Bernstein, A; Hay, D I; Blum, M; Bennick, A



Macroporous calcium phosphate glass-ceramic prepared by two-step pressing technique and using sucrose as a pore former.  


Macroporous calcium phosphate glass-ceramic with an initial glass composition of 60CaO.30P2O5.3TiO2.7Na2O in mol% was successfully prepared by sintering the mixture compact consisting of calcium phosphate glass and sucrose powders, which was formed using a two-step pressing technique. After burning off the sucrose phase, a 3D interconnected macroporous structure was formed in the sintered body, in which the skeleton consisting of the calcium phosphate glass-ceramic (including beta-calcium pyrophosphate and beta-tricalcium phosphate as the crystalline phases) was transformed from the initial glass during the sintering. The macropores with several hundred microns in diameter and the large interconnection size (approximately 100 microm), which result from the controllably large-sized sucrose particles and the hot-pressing at a little higher temperature than the sucrose's melting point, are believed to meet the requirements for cell adhesion and bone tissue regeneration well. Moreover, in vitro dissolution behavior study indicates that the calcium phosphate glass-ceramic is soluble to an acetic acid solution of pH 5-7. These, together with the simplicity and feasibility of the innovative fabrication method itself, show that the formed porous glass-ceramic has a promising potential for application to a scaffold for bone tissue engineering. PMID:15965744

Wang, Cong; Kasuga, Toshihiro; Nogami, Masayuki



Hydrogels in calcium phosphate moldable and injectable bone substitutes: Sticky excipients or advanced 3-D carriers?  


The combination of hydrogels and calcium phosphate particles is emerging as a well-established trend for bone substitutes. Besides acting as binders for the inorganic phase, hydrogels within these hybrid materials can modulate cell colonization physically and biologically. The influence of hydrogels on the healing process can also be exploited through their capability to deliver drugs and cells for tissue engineering approaches. The aim of this review is to collect some recent progress in this field, with an emphasis on design aspects and possible future directions. PMID:23201020

D'Este, M; Eglin, D



The nature of calcium-phosphate crystal formations grown on dentine surface  

NASA Astrophysics Data System (ADS)

Laboratory experiments conducted in Saratov State University in the first half of 2012 revealed crystal formations on the surface of etched dentine after it had been exposed to 95% ethanol in solution for 30 days at room temperature. It was discovered that the structures observed were calcium-phosphate crystals. The nature of crystal formation on rough dentine surface was described based on substance diffusion in solution, which resulted in dentine becoming spatially inhomogeneous over time. The crystal formation was established to be determined by the limited ion redistribution in dentine material.

Bessudnova, Nadezda O.; Bilenko, David I.; Venig, Sergey B.; Atkin, Vsevolod S.; Galushka, Viktor V.; Zakharevich, Andrey M.



Influence of calcium chloride and aprotinin in the in vivo biological performance of a composite combining biphasic calcium phosphate granules and fibrin sealant  

Microsoft Academic Search

Highly bioactive biomaterials have been developed to replace bone grafts in orthopedic revision and maxillofacial surgery\\u000a for bone augmentation. A mouldable, self-hardening material can be obtained by combining TricOs® Biphasic Calcium Phosphate\\u000a Granules and Tissucol® Fibrin Sealant. Two components, calcium chloride and antifibrinolytic agents (aprotinin), are essential\\u000a for the stability of the fibrin clot. The ingrowth of cells in composites

Laurent Le Guehennec; Eric Goyenvalle; Eric Aguado; Paul Pilet; Reiner Spaethe; Guy Daculsi



Identification of proteins extracted from calcium oxalate and calcium phosphate crystals induced in the urine of healthy and stone forming subjects  

Microsoft Academic Search

The purpose of our study was to identify the proteins and investigate the differences, if any, between protein components\\u000a of the matrices of calcium oxalate (CaOx) and calcium phosphate (CaP) crystals induced in?vitro in whole human urine of healthy\\u000a individuals and kidney stone patients. In addition, preliminary studies were performed to understand the effect of centrifugation\\u000a and filtration of urine

Fouad Atmani; Patricia A. Glenton; Saeed R. Khan



Analytical and mechanical testing of high velocity oxy-fuel thermal sprayed and plasma sprayed calcium phosphate coatings.  


Plasma spraying (PS) is the most frequently used coating technique for implants; however, in other industries a cheaper, more efficient process, high-velocity oxy-fuel thermal spraying (HVOF), is in use. This process provides higher purity, denser, more adherent coatings than plasma spraying. The primary objective of this work was to determine if the use of HVOF could improve the mechanical properties of calcium phosphate coatings. Previous studies have shown that HVOF calcium phosphate coatings are more crystalline than plasma sprayed coatings. In addition, because the coatings are exposed to more complex loading profiles in vivo than standard ASTM tensile tests provide, a secondary objective of this study was to determine the applicability of four-point bend testing for these coatings. Coatings produced by HVOF and PS were analyzed by profilometry, diffuse reflectance Fourier transform infrared spectroscopy, X-ray diffraction, four-point bend, and ASTM C633 tensile testing. HVOF coatings were found to have lower amorphous calcium phosphate content, higher roughness values, and lower ASTM C633 bond strengths than PS coatings; however, both coatings had similar crystal unit cell sizes, phases present (including hydroxyapatite, beta-tricalcium phosphate, and tetracalcium phosphate), and four-point bend bond strengths. Thus, the chemical, structural, and mechanical results of this study, in general, indicate that the use of HVOF to produce calcium phosphate coatings is equivalent to those produced by plasma spraying. PMID:10556851

Haman, J D; Chittur, K K; Crawmer, D E; Lucas, L C



Wet or dry mechanochemical synthesis of calcium phosphates? Influence of the water content on DCPD-CaO reaction kinetics.  


Mechanosynthesis of calcium phosphates can be performed under wet or dry conditions. In most papers and patents, grinding under wet conditions was selected. So far, only a few papers were devoted to dry mechanosynthesis of calcium phosphates. To understand why wet mechanosynthesis was preferred, the influence of water addition on the kinetics of the mechanochemical reaction of dicalcium phosphate dihydrate with calcium oxide was investigated. The DCPD disappearance rate constant k and the final reaction time t(f) were determined in each case and correlated with the water content present in the slurry. Results showed that the addition water (i) slowed down the reaction rate and (ii) increased the powder contamination by mill material (hard porcelain) due to ball and vial erosion; and that (iii) wet milling did not generate the expected products, in contrast to dry grinding, because porcelain induced hydroxyapatite decomposition with the formation of beta-tricalcium phosphate and silicon-stabilized tricalcium phosphate. Consequently, dry mechanosynthesis appears preferable to wet milling in the preparation of calcium phosphates of biological interest. PMID:17827078

El Briak-Benabdeslam, H; Ginebra, M P; Vert, M; Boudeville, P



Preparation and properties of calcium phosphate cements incorporated gelatin microspheres and calcium sulfate dihydrate as controlled local drug delivery system.  


To develop high macroporous and degradable bone cements which can be used as the substitute of bone repairing and drug carriers, cross-linked gelatin microspheres (GMs) and calcium sulfate dihydrate (CSD) powder were incorporated into calcium phosphate bone cement (CPC) to induce macropores, adjust drug release and control setting time of ?-TCP-liquid mixtures after degradation of GMs and dissolution of CSD. In this study, CSD was introduced into CPC/10GMs composites to offset the prolonged setting time caused by the incorporation of GMs, and gentamicin sulphate (GS) was chosen as the model drug entrapped within the GMs. The effects of CSD amount on the cement properties, drug release ability and final macroporosity after GMs degradation were studied in comparison with CPC/GMs cements. The resulting cements presented reduced setting time and increased compressive strength as the content of CSD below 5 wt%. Sustained release of GS was obtained on at least 21 days, and release rates were found to be chiefly controlled by the GMs degradation rate. After 4 weeks of degradation study, the resulting composite cements appeared macroporous, degradable and suitable compressive strength, suggesting that they have potential as controlled local drug delivery system and for cancellous bone applications. PMID:21894539

Cai, Shu; Zhai, Yujia; Xu, Guohua; Lu, Shanshan; Zhou, Wei; Ye, Xiaojian



Influence of the calcium phosphate content of the target on the phase composition and deposition rate of sputtered films  

NASA Astrophysics Data System (ADS)

Calcium phosphate was coated from tetracalcium phosphate (TTCP), hydroxyapatite (HA), ?-tricalcium phosphate (TCP), ?-calcium pyrophosphate (CPP), and ?-calcium metaphosphate (CMP) powder targets using radio frequency magnetron sputtering. The composition of the crystal phase of the coated films was changed, depending on the target materials, and the Ca/P molar ratios of the films varied from 0.74 to 2.54, increasing with the Ca/P molar ratio of the target. The solubility of the target, determined using a microwave-induced plasma-mass spectrometer was: TTCP ? ?-CMP > ?-TCP > ?-CPP > HA, and the deposition rate from each target showed a similar order to the solubility: TTCP ? ?-CMP > ?-TCP > ?-CPP ? HA.

Ozeki, K.; Fukui, Y.; Aoki, H.



Morphological modifications of electrodeposited calcium phosphate coatings under amino acids effect  

NASA Astrophysics Data System (ADS)

Calcium phosphate coatings are synthesized on titanium alloy (Ti6Al4V) substrates by pulsed electrodeposition. This work aims to observe the morphological modifications of the coating when an amino acid is added to the electrolytic solution used in the process. The effects of two amino acids (glutamic acid and aspartic acid) are studied at a low and a high concentration. The coating morphology is observed at a nanometer scale by field emission gun-scanning electron microscopy (FEG-SEM). The structural characterization of the coating is performed by Fourier transformed infrared spectroscopy (FT-IR), Raman spectroscopy and X-ray diffraction (XRD). Moreover, corrosion measurements of the prosthetic surfaces are carried out by potentiodynamic polarization experiments in a physiological solution named Dulbecco's modified eagle medium (DMEM). The results show that the addition of an amino acid to the electrolytic solution leads to the decrease of the size of the crystallites which compose the prosthetic calcium phosphate coating that becomes denser and less porous than the coatings obtained without amino acid. Consequently, the corrosion behavior of the prosthetic material immersed in DMEM is improved.

Drevet, R.; Lemelle, A.; Untereiner, V.; Manfait, M.; Sockalingum, G. D.; Benhayoune, H.



Sol-gel synthesis and characterization of macroporous calcium phosphate bioceramics containing microporosity.  


Amorphous calcium phosphate powders were precipitated from calcium metal and phosphoric acid in ethanol. Depending on the quantity of reagent, the CaP powders had different chemical compositions and, after heating, formed beta-tricalcium phosphate (beta-TCP), hydroxyapatite (HA) or BCP mixtures. Dilatometric measurements indicated that shrinkage of compacted CaP powders occurred first at around 650 degrees C and continued up to 1200 degrees C. The amorphous CaP powders were mixed with urea beads, compacted under isostatic pressure at 140 MPa and sintered at 1100 degrees C for 5 h. Scanning electron microscopy indicated that macro-microporous ceramics were produced. The ceramics had spherical macropores of 700-1200 microm in diameter, with limited interconnections and a macroporosity of 42% as determined by microcomputed tomography. The micropores ranged from 0.1 to 1 microm in diameter. These ceramics made of HA, beta-TCP or BCP exhibiting both macroporosity and microporosity can be used as bone fillers. PMID:18851931

Fellah, Borhane H; Layrolle, Pierre



Study of implantable calcium phosphate systems for the slow release of methotrexate.  


The authors prepared and studied systems implantable in bone, for the slow release of an antineoplasic agent, methotrexate (MTX). The systems were made by compaction of a powdered mixture of an apatitic deficient calcium phosphate, dextran and various amounts of MTX. Used as a matrix, this calcium phosphate has outstanding adsorption and compaction properties. It is an osteoconductor and biodegradable. The in vitro study carried out on these systems showed that the release of MTX with time is slow and prolonged due to the phenomena of adsorption/desorption of MTX onto deficient apatite. The composition of the implants changed with time towards that of stoichiometric apatite. The in vivo pilot study was performed by implantation in the external femoral condyle of rabbits. A pharmacokinetic study revealed that the circulating concentration of MTX in the blood was always below toxic levels. Twenty percent of the initial MTX remained in the implants after 7 days. A study of the biocompatibility and bioreactivity showed no local necrosis at any time, while implants degraded and new bone formed simultaneously. These implantable systems seem appear suitable for use immediately. PMID:12099297

Lebugle, A; Rodrigues, A; Bonnevialle, P; Voigt, J J; Canal, P; Rodriguez, F



The use of calcium phosphate cement paste for the correction of the depressed nose deformity.  


The authors report the use of calcium phosphate cement paste as a material for correction of depression after nasal bone fracture, and evaluate its usefulness. Biopex R (Mitsubishi Material Corporation, Tokyo, Japan) was used in this study as calcium phosphate cement (CPC), which was developed in Japan. CPC injection was used in six patients (four women and two men) with depressed nose deformity after nasal bone fracture. The patients' ages ranged from 29 to 67 years (mean, 49 years), and the follow-up period ranged from 12 to 27 months. The amount of injected cement varied from 0.5 to 2.5 mL, approximately. There was no postoperative infection or allergic reaction in any patient. Clinical and X-ray photography findings showed that a reduction in volume of the injected cement occurred gradually as long as 7 to 8 months after surgery. After that period, the volume was mostly maintained. It seemed that the degree of reduction was approximately 10% to 15% of the original volume. Satisfactory results were obtained in all cases. The authors conclude that the use of CPC is an option for the correction of depressed nose deformity and that its application must be determined in each case, considering its advantages and disadvantages. PMID:15750435

Hatoko, Mitsuo; Tada, Hideyuki; Tanaka, Aya; Yurugi, Satoshi; Niitsuma, Katsunori; Iioka, Hiroshi



Association of calcium and phosphate ions with collagen in the mineralization of vertebrate tissues.  


Among the vertebrate species, collagen is the most abundant protein and is associated with mineralization of their skeleton and dentition in all tissues except enamel. In such tissues, bones, calcifying tendon, dentin, and cementum are comprised principally of type I collagen, which has been proposed as a template for apatite mineral formation. Recent considerations of the interaction between type I collagen and calcium and phosphate ions as the major constituents of apatite have suggested that collagen polypeptide stereochemistry underlies binding of these ions at sites within collagen hole and overlap regions and leads to nucleation of crystals. The concept is fundamental to understanding both normal and abnormal mineralization, and it is reviewed in this article. Given this background, avenues for additional research studies in vertebrate mineralization will also be described. The latter include, for instance, how mineralization events subsequent to nucleation, that is, crystal growth and development, occur and whether they, too, are directed by collagen stereochemical parameters; whether mineralization can be expected in all spaces between collagen molecules; whether the side chains of charged amino acid residues actually point toward and into the hole and overlap collagen spaces to provide putative binding sites for calcium and phosphate ions; and what phenomena may be responsible for mineralization beyond hole and overlap zones and into extracellular tissue regions between collagen structural units. These questions will be discussed to provide a broader understanding of collagen contributions to potential mechanisms of vertebrate mineralization. PMID:23543143

Landis, William J; Jacquet, Robin



Calcium phosphate/octadecyl-quatemized carboxymethyl chitosan nanoparticles: an efficient and promising carrier for gene transfection.  


Calcium phosphate (CaP) has been widely used as the vector for gene transfection in the past three decades. However, clinical application is still not popular due to the poor-controlling of DNA/CaP complexes preparation, cytotoxicity and its low transfection efficiency. In this study, a novel amphipathic octadecyl-quatemized carboxymethyl chitosan (OQCMC) derivative from chitosan was combined with calcium phosphate to synthesize CaP/OQCMC nanoparticles (CaP/OQCMC NPs). The nanoparticles were 122-177 nm in diameter exhibited neutral zeta potential (from -0.115 mV to 0.216 mV), and they were applied as DNA vectors for DNA loading and in vitro transfection. The results showed that CaP/OQCMC NPs displayed high DNA loading capacity and enhanced transfection efficiency with extremely low cytotoxicity. In addition, both CaP and OQCMC are biocompatible and biodegradable, thus the as-prepared CaP/OQCMC NPs are promising in gene delivery. PMID:23882752

Sun, Ying; Li, Xiaoyu; Liang, Xiaofei; Wan, Zhiyong; Duan, Yourong



Amorphous calcium phosphate/urethane methacrylate resin composites. I. Physicochemical characterization  

PubMed Central

Urethane dimethacrylate (UDMA), an oligomeric poly(ethylene glycol) extended UDMA (PEG-U) and a blend of UDMA/PEG-U were chosen as model systems for introducing both hydrophobic and hydrophilic segments and a range of compliances in their derived polymers. Experimental composites based on these three resins with amorphous calcium phosphate (ACP) as the filler phase were polymerized and evaluated for mechanical strength and ion release profiles in different aqueous media. Strength of all composites decreased upon immersion in saline (pH = 7.4). Both polymer matrix composition and the pH of the liquid environment strongly affected the ion release kinetics. In saline, the UDMA/PEG-U composite showed a sustained release for at least 350 h. The initially high ion release of the PEG-U composites decreased after 72 h, seemingly due to the mineral re-deposition at the composite surface. Internal conversion from ACP to poorly crystallized apatite could be observed by X-ray diffraction. In various lactic acid (LA) environments (initial pH = 5.1) ion release kinetics was much more complex. In LA medium without thymol and/or carboxymethylcellulose, as a result of unfavorable changes in the internal calcium/phosphate ion stoichiometry, the ion release rate greatly increased but without observable conversion of ACP to apatite.

Regnault, W.F.; Icenogle, T.B.; Antonucci, J.M.; Skrtic, D.



Properties of injectable ready-to-use calcium phosphate cement based on water-immiscible liquid.  


Calcium phosphate cements (CPCs) are highly valuable materials for filling bone defects and bone augmentation by minimal invasive application via percutaneous injection. In the present study some key features were significantly improved by developing a novel injectable ready-to-use calcium phosphate cement based on water-immiscible carrier liquids. A combination of two surfactants was identified to facilitate the targeted discontinuous exchange of the liquid for water after contact with aqueous solutions, enabling the setting reaction to take place at distinct ratios of cement components to water. This prolonged the shelf life of the pre-mixed paste and enhanced reproducibility during application and setting reactions. The developed paste technology is applicable for different CPC formulations. Evaluations were performed for the formulation of an ?-TCP-based CPC as a representative example for the preparation of injectable pastes with a powder-to-carrier liquid ratio of up to 85:15. We demonstrate that the resulting material retains the desirable properties of conventional CPC counterparts for fast setting, mechanical strength and biocompatibility, shows improved cohesion and will most probably show a similar degree of resorbability due to identical mineral structure of the set products. PMID:23261920

Heinemann, S; Rössler, S; Lemm, M; Ruhnow, M; Nies, B



New processing approaches in calcium phosphate cements and their applications in regenerative medicine.  


The key feature of calcium phosphate cements (CPCs) lies in the setting reaction triggered by mixing one or more solid calcium phosphate salts with an aqueous solution. Upon mixture, the reaction takes place through a dissolution-precipitation process which is macroscopically observed by a gradual hardening of the cement paste. The precipitation of hydroxyapatite nanocrystals at body or room temperature, and the fact that those materials can be used as self-setting pastes, have for many years been the most attractive features of CPCs. However, the need to develop materials able to sustain bone tissue ingrowth and be capable of delivering drugs and bioactive molecules, together with the continuous requirement from surgeons to develop more easily handling cements, has pushed the development of new processing routes that can accommodate all these requirements, taking advantage of the possibility of manipulating the self-setting CPC paste. It is the goal of this paper to provide a brief overview of the new processing developments in the area of CPCs and to identify the most significant achievements. PMID:20123046

Ginebra, M P; Espanol, M; Montufar, E B; Perez, R A; Mestres, G



Dehydration of aliphatic alcohols on phosphoric acid catalyst with the addition of calcium phosphate  

SciTech Connect

The kinetic regularities of dehydration of sec- and tert-butyl alcohols on a catalyst consisting of a mixture of calcium phosphate and H/sub 3/PO/sub 4/, deposited on molten quartz were studied by pulsed gas chromatography. At an equal water vapor pressure in the system, the activity of a catalyst consisting of a pure H/sub 3/PO/sub 4/ is higher than that of a catalyst with the addition of a salt. The experimentally observed dehydration rate constants and those determined with the retention volumes taken into account were measured. Activation energies, rate constants, and the heat of dissolution of tert-butyl alcohol on calcium phosphate catalyst were determined in the range of 80-110/sup 0/C. The dehydration of sec-butyl alcohol was studied at 140/sup 0/C. It was found that in a liquid phase, the reaction rate constant is not very dependent on the salt/acid ratio.

Obraztsov, P.A.; Batalin, O.E.; Malinskii, V.S.; Shubenok, L.F.; Vinnik, M.I.



Unusual effect of water vapor pressure on dehydration of dibasic calcium phosphate dihydrate.  


Dibasic calcium phosphate occurs as an anhydrate (DCPA; CaHPO4 ) and as a dihydrate (DCPD; CaHPO4 •2H2 O). Our objective was to investigate the unusual behavior of these phases. Dibasic calcium phosphate dihydrate was dehydrated in a (i) differential scanning calorimeter (DSC) in different pan configurations; (ii) variable-temperature X-ray diffractometer (XRD) at atmospheric and under reduced pressure, and in sealed capillaries; and (iii) water vapor sorption analyzer at varying temperature and humidity conditions. Dehydration was complete by 210°C in an open DSC pan and under atmospheric pressure in the XRD. Unlike "conventional" hydrates, the dehydration of DCPD was facilitated in the presence of water vapor. Variable-temperature XRD in a sealed capillary and DSC in a hermetic pan with pinhole caused complete dehydration by 100°C and 140°C, respectively. Under reduced pressure, conversion to the anhydrate was incomplete even at 300°C. The increase in dehydration rate with increase in water vapor pressure has been explained by the Smith-Topley effect. Under "dry" conditions, a coating of poorly crystalline product is believed to form on the surface of particles and act as a barrier to further dehydration. However, in the presence of water vapor, recrystallization occurs, creating cracks and channels and facilitating continued dehydration. © 2010 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 100:1456-1466, 2011. PMID:24081471

Kaushal, Aditya M; Vangala, Venu R; Suryanarayanan, Raj



Unusual effect of water vapor pressure on dehydration of dibasic calcium phosphate dihydrate.  


Dibasic calcium phosphate occurs as an anhydrate (DCPA; CaHPO(4)) and as a dihydrate (DCPD; CaHPO(4)•2H(2)O). Our objective was to investigate the unusual behavior of these phases. Dibasic calcium phosphate dihydrate was dehydrated in a (i) differential scanning calorimeter (DSC) in different pan configurations; (ii) variable-temperature X-ray diffractometer (XRD) at atmospheric and under reduced pressure, and in sealed capillaries; and (iii) water vapor sorption analyzer at varying temperature and humidity conditions. Dehydration was complete by 210°C in an open DSC pan and under atmospheric pressure in the XRD. Unlike "conventional" hydrates, the dehydration of DCPD was facilitated in the presence of water vapor. Variable-temperature XRD in a sealed capillary and DSC in a hermetic pan with pinhole caused complete dehydration by 100°C and 140°C, respectively. Under reduced pressure, conversion to the anhydrate was incomplete even at 300°C. The increase in dehydration rate with increase in water vapor pressure has been explained by the Smith-Topley effect. Under "dry" conditions, a coating of poorly crystalline product is believed to form on the surface of particles and act as a barrier to further dehydration. However, in the presence of water vapor, recrystallization occurs, creating cracks and channels and facilitating continued dehydration. © 2010 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci. PMID:21136556

Kaushal, Aditya M; Vangala, Venu R; Suryanarayanan, Raj



Surface potential and osteoblast attraction to calcium phosphate compounds is affected by selected alkaline hydrolysis processing.  


This study examines the link(s) between the suspension behavior of calcium deficient apatites (CDAs) and biphasic calcium phosphate (BCP), as measured by the zeta-potential, with respect to both whole bone and osteoblasts. CDA is fabricated by hydrolyzing an acidic CaP such as dicalcium diphosphate dihydrate (DCPD; CaHPO4.2H2O) and has a structure and composition close to bone apatite. Sintering CDA results in the formation of BCP ceramics consisting of mixtures of hydroxyapatite (HA) and beta-tricalcium phosphate (beta-TCP), with the HA/beta-TCP weight ratio proportional to the Ca/P ratio of CDA. The choice of the base for the DCPD hydrolysis allows various ionic partial substitution of the formed CDA. Na for Ca partial substitution is of interest because of the resulting improvement in mechanical properties of the resulting BCP ceramics and NH4OH was used as a negative control. The zeta-potential was measured for these materials and the stability of the ceramic to bone interaction calculated. zeta-potential values decrease for CDA(NH4OH) versus CDA(NaOH) and increase for BCP(NH4OH) versus BCP(NaOH). While results of these analyses indicate that NH4OH and NaOH processed CDA and BCP will likely yield osteoblast attachment in vivo, differences in the zeta-potentials may explain varying degrees of cell attachment. PMID:15477734

Smith, I O; Baumann, M J; Obadia, L; Bouler, J-M



Chapter 9: Model Systems for Formation and Dissolution of Calcium Phosphate Minerals  

SciTech Connect

Calcium phosphates are the mineral component of bones and teeth. As such there is great interest in understanding the physical mechanisms that underlie their growth, dissolution, and phase stability. Control is often achieved at the cellular level by the manipulation of solution states and the use of crystal growth modulators such as peptides or other organic molecules. This chapter begins with a discussion of solution speciation in body fluids and relates this to important crystal growth parameters such as the supersaturation, pH, ionic strength and the ratio of calcium to phosphate activities. We then discuss the use of scanning probe microscopy as a tool to measure surface kinetics of mineral surfaces evolving in simplified solutions. The two primary themes that we will touch on are the use of microenvironments that temporally evolve the solution state to control growth and dissolution; and the use of various growth modifiers that interact with the solution species or with mineral surfaces to shift growth away from the lowest energy facetted forms. The study of synthetic minerals in simplified solution lays the foundation for understand mineralization process in more complex environments found in the body.

Orme, C A; Giocondi, J L



Defective calcium increase and inositol phosphate production in anti-CD3-stimulated lymphocytes of alcoholics without progressive liver disease.  


Intracellular free calcium concentration, phosphoinositide turnover, and inositol phosphate production were analyzed in peripheral blood lymphocytes from seven well-nourished alcoholic patients without severe acute or chronic liver disease, before and after stimulation with anti-CD3 antibody. Seven comparable nondrinkers were studied as controls. A lower increase in intracellular free calcium concentration was detected in alcoholics, after anti-CD3 stimulation of lymphocytes, than in control subjects. Lymphocyte activation generated inositol phosphates in both controls and alcoholics, but inositol phosphate production was significantly lower in alcoholics. The agreement between these findings indicates that the reduction in inositol phosphates is one of the most important events in the early phases of lymphocyte activation in alcoholics. PMID:8727248

Stefanini, G F; Castelli, E; Foschi, F G; Terzi, A; Biagi, P L; Bordoni, A; Celadon, M; Hrelia, S



Precipitation of calcium phosphate and calcium carbonate induced over chitosan membranes: A quick method to evaluate the influence of polymeric matrices in heterogeneous calcification  

Microsoft Academic Search

Precipitation of calcium compounds (phosphate and carbonate) was performed on chitosan porous and dense membranes. In order to observe the influence of acetyl groups on the nature of formed precipitates, some chitosan membranes were acetylated in methanol solution before undergoing calcification. Calcification experiments were performed more quickly than using SBF. In this method, a faster precipitation is induced by soaking

Cassiano Gomes Aimoli; Marisa Masumi Beppu



Variation in crystallinity of hydroxyapatite and the related calcium phosphates by mechanical grinding and subsequent heat treatment  

Microsoft Academic Search

The crystallinity of hydroxyapatite (HAp) and the related calcium phosphates for regenerating hard tissues was controlled\\u000a by the mechanical grinding (MG) method and subsequent heat treatment. The HAp, carbonate-apatite (CO3Ap), fluorapatite (FAp), and ?- and ?-tricalcium phosphates (?-TCP and ?-TCP, respectively) and tetracalcium diphosphate monoxide (TTCP) were used as initial materials. Variations in crystallinity\\u000a and crystal structure were examined by

Takayoshi Nakano; Yukichi Umakoshi; Atsuyuki Tokumura



Development of a new calcium phosphate powder-binder system for the 3D printing of patient specific implants  

Microsoft Academic Search

A key requirement for three-dimensional printing (3-DP) of medical implants is the availability of printable and biocompatible\\u000a powder-binder systems. In this study we developed a powder mixture comprising tetracalcium phosphate (TTCP) as reactive component\\u000a and ?-tricalcium phosphate (?-TCP) or calcium sulfate as biodegradable fillers, which can be printed with an aqueous citric\\u000a acid solution. The potential of this material combination

Alaadien Khalyfa; Sebastian Vogt; Jürgen Weisser; Gabriele Grimm; Annett Rechtenbach; Wolfgang Meyer; Matthias Schnabelrauch



Bone tissue formation in sheep muscles induced by a biphasic calcium phosphate ceramic and fibrin glue composite  

Microsoft Academic Search

Some biomaterials are able to induce ectopic bone formation in muscles of large animals. The osteoinductive potential of macro-\\u000a micro-porous biphasic calcium phosphate (MBCP) ceramic granules with fibrin glue was evaluated by intramuscular implantation\\u000a for 6 months in six adult female sheep. The MBCP granules were 1–2 mm in size and were composed of hydroxyapatite (HA) and\\u000a beta-tricalcium phosphate (?-TCP) in a

Damien Le Nihouannen; Afchine Saffarzadeh; Olivier Gauthier; Françoise Moreau; Paul Pilet; Reiner Spaethe; Pierre Layrolle; Guy Daculsi



Bio-inspired Resorbable Calcium Phosphate-Polymer Nanocomposites for Bone Healing Devices with Controlled Drug Release  

Microsoft Academic Search

\\u000a In orthopedic research, increasing attention is being paid to bioresorbable composite materials as an attractive alternative\\u000a to permanent metal bone healing devices. Typical composites consist of a biodegradable polyester matrix loaded with bioactive\\u000a calcium phosphate ceramic particles (tricalcium phosphate, TCP or hydroxyapatite, HA) added to improve the biological response\\u000a and mechanical properties of the neat polymer. The mechanical behavior of

Irena Gotman; Sabine Fuchs


In vitro evaluation of dentinal hydraulic conductance and tubule sealing by a novel calcium-phosphate desensitizer.  


In the current trend of materials used for dentin hypersensitivity treatment, calcium-phosphate-containing desensitizers are expected to have advantages in oral environment. A newly formulated desensitizer containing tetracalcium phosphate and dicalcium phosphate anhydrous (CPD-100) was evaluated in comparison to oxalate containing desensitizer (SS) regarding permeability reduction (PR%) by measuring hydraulic conductance on the etched dentin discs in vitro. CPD-100 exhibited mean PR% of 91%, which significantly increased to 98% after immersion in artificial saliva (AS) for 4 weeks (p < 0.001), while SS showed a significant decrease from 99% to 93% (p < 0.01). SEM observation showed newly formed crystallites on CPD-100 treated dentin, which did not exist in SS treated dentin after AS immersion, suggesting that calcium oxalate inhibited formation of new calcium-phosphate minerals. Five-minute acid challenge did not significantly affect PR% of dentin treated by any of the desensitizers. The energy dispersive X-ray spectroscopy (EDS) analysis indicated that the formed layer of CPD-100 were minerals with similar Ca/P ratio to hydroxyapatite. In conclusion, the newly developed calcium-phosphate desensitizer has the potential to exhibit long-term stability in the oral environment, owing to its chemical properties that promote the crystal growth in salivary fluid. PMID:23166091

Thanatvarakorn, Ornnicha; Nakashima, Syozi; Sadr, Alireza; Prasansuttiporn, Taweesak; Ikeda, Masaomi; Tagami, Junji



Effects of hydroxypropyl methylcellulose and other gelling agents on the handling properties of calcium phosphate cement.  


The calcium phosphate cement (CPC) used in this study was formed by combining equimolar amounts of tetracalcium phosphate (TTCP) and dicalcium phosphate anhydrous (DCPA). This powder, when mixed with water, sets to a hard cement in about 30 min. However, the water-based CPC paste is not highly cohesive and is vulnerable to washout until hardening occurs. The objectives of this study were to investigate the effects on handling properties, washout resistance, cement hardening behavior, and mechanical properties of adding several gelling agents to CPC paste. Aqueous solutions that contained a mass fraction of 2-4% of hydroxypropyl methylcellulose (HPMC), carboxyl methylcellulose (CMC), chitosan acetate, and chitosan lactate were used as cement liquids. Hardening time was measured by the Gilmore needle test; resistance to washout was evaluated by the disintegration of the cement specimen in water with agitation; and mechanical strength was evaluated by the measurement of diametral tensile strength and compressive strength. Handling properties were greatly improved by the addition of HPMC, CMC, chitosan acetate, and chitosan lactate. Hardening time was retarded by the additions of HPMC and CMC, and mechanical strength was weakened by the addition of either the chitosan lactate or the chitosan acetate. PMID:9138061

Cherng, A; Takagi, S; Chow, L C



Role of phosphate groups in inhibition of calcium oxalate crystal growth by osteopontin.  


Osteopontin (OPN) inhibits the growth of calcium oxalate monohydrate (COM) and other crystal phases in a phosphorylation-dependent manner. In the present study, the role of OPN phosphate groups in adsorption to, incorporation into and inhibition of COM crystals was studied by comparing OPN isoforms differing in phosphorylation. OPN isoforms purified from rat bone (bOPN), which contains 10 phosphates, and cow milk (mOPN), which contains 25 phosphates, were compared with rat recombinant OPN (rOPN), which is not phosphorylated. Using fluorescence-labeled proteins and confocal microscopy, we show that mOPN and rOPN, like bOPN, adsorb preferentially to the edges between {100} and {121} faces of preformed COM crystals, and to a lesser extent to the {100} and {121} faces. Using scanning electron microscopy, we show that growth of COM in the presence of bOPN or mOPN results in a 'dumbbell' morphology, whereas crystals grown with rOPN are only slightly affected. COM crystals grown in the presence of low concentrations of fluorescence-labeled bOPN incorporate the protein into the crystal lattice. In crystals imaged in the {010} plane, incorporation of bOPN results in a cross-shaped pattern of fluorescence, consistent with preferential adsorption to {100}/{121} edges throughout the growth process. PMID:18703867

Hunter, Graeme K; Grohe, Bernd; Jeffrey, Sara; O'Young, Jason; Sørensen, Esben S; Goldberg, Harvey A



Calcium phosphates and glass composite coatings on zirconia for enhanced biocompatibility.  


Calcium phosphates (CaP) and phosphate-based glass (P-glass, xCaO-(0.55-x) Na(2)O-0.45P(2)O(5) composition) composite coatings were obtained on a strong ZrO(2) to improve biocompatibility, the mechanical strength and biological activity. Hydroxyapatite (HA) and P-glass mixed powder slurries were coated on the ZrO(2) substrate, and subsequently heat-treated to obtain CaP- and P-glass composite coatings. The effects of glass composition (x=0.3, 0.4, 0.5 mol), mixing ratio of glass to HA (30%, 40%, 50% wt/wt), and heat treatment temperature (800 degrees C, 900 degrees C, 1000 degrees C) on the coating properties were investigated. After heat treatment, additional calcium phosphates, i.e., dicalcium phosphate (DCP) and tricalcium phosphate (TCP), were crystallized, resulting in the formation of triphasic calcium phosphates (HA-TCP-DCP) surrounded by a glass phase. The relative amounts of the crystalline phases varied with coating variables. The higher heat treatment temperature and glass amount, and the lower CaO content in the glass composition rendered the composite coatings to retain the higher amounts of TCP and DCP while the initial HA decreased. These appearance of additional crystalline phases and reduction of HA amount were attributed to the combined effects, i.e., the melting-crystallization of P-glass and the reaction between glass liquid phase and HA powder during thermal treatment. As a result of the glass phase in the composite coatings, their microstructures became much denser when compared to the pure HA coating. In particular, a completely dense structure was obtained at coating conditions with large amount of glass addition (50 wt%) at the glass composition of lower CaO content (0.3 mol CaO), and the following heat treatment above 800 degrees C for 2h. As a result, the adhesion strengths of the composite coating layers were significantly improved when compared to the pure HA coating. The highest strength of the composite coating was approximately 40 MPa, an improvement of approximately 80% with respect to the pure HA coating. The composite coatings showed much higher dissolution rates than the pure HA coating due to the newly formed crystallines (TCP and DCP) and the remaining glass phase. The osteoblast-like cells grew and spread actively on the composite coating samples. The proliferation numbers and alkaline phosphate (ALP) activities of the cells on the composite coatings were improved by approximately 30-40% when compared to Thermanox control and ZrO(2) substrate, and were comparable to the pure HA coating. These findings suggested that the CaP and P-glass composites are potentially useful for hard tissue coating system, due to their morphological and mechanical integrity, enhanced bioactivity, and favorable responses to the osteoblast-like cells. PMID:15046910

Kim, Hae-Won; Georgiou, George; Knowles, Jonathan C; Koh, Young-Hag; Kim, Hyoun-Ee



Antimicrobial activity and tightness of a DCPD-CaO-based hydraulic calcium phosphate cement for root canal filling.  


Calcium hydroxide is currently used in dentistry for endodontic treatments where its main advantage is its antibacterial and anti-inflammatory activity. However, it also has some drawbacks such as pulp necrosis, slight solubility, slow and insufficient hardening, and retraction on drying. In consequence, it is used only as temporary material for root canal disinfection. By mixing calcium hydrogen phosphate dihydrate (CaHPO4 . 2H2O, also called dicalcium phosphate dihydrate, DCPD) and calcium oxide with a sodium phosphate buffer as liquid phase, we obtained a CPC with better mechanical properties than calcium hydroxide pastes. The setting reaction produced either hydroxyapatite (HA) or a mixture of HA and calcium hydroxide depending on the relative masses of DCPD and CaO in the cement powder. The presence of calcium hydroxide a priori confers antimicrobial properties to this cement which were investigated in agar plates (diffusion method) against Streptococcus mutans, Lactobacillus acidophilus, Candida albicans, Enterococcus faecalis, Staphylococcus hominis (clinical isolates), and a preparation of polymicrobial flora isolated from dental plaque. The cement samples tested were prepared at molar calcium-to-phosphate ratios (Ca/P) of 1.67 to 2.75. A pure calcium hydroxide paste was used as reference material. Clear and reproducible bacterial growth inhibition was observed for cement samples with Ca/P > or = 2 against all the microorganisms tested. With Ca/P = 2.5, this cement alkalinizes dentinal tubules and provides a fluid-tight sealing that well compares with sealing obtained using a zinc oxide-eugenol cement without gutta-percha point. DCPD-CaO-based cement is therefore a potential root canal filler. PMID:15981171

Michaïlesco, Pierre; Kouassi, Michel; El Briak, Hasna; Armynot, Anne; Boudeville, Philippe



[An in vitro study of dentin hypersensitivity using calcium phosphate cement].  


Calcium phosphate remineralizing slurry (CPRS), consisting of an equimolar mixture of tetracalcium phosphate (TTCP) and dicalcium phosphate dihydrate (DCPD), has previously been shown to form hydroxyapatite (HAp) spontaneously at physiological pH. Since considerable amounts of HAp may be formed in situ by CPRS, it may be effective for desensitizing hypersensitive dentin by obturating exposed dentinal tubule openings. In the present study, the effects of topically applied CPRS to etched dentin surfaces were investigated. The samples were randomly divided into 3 groups: (1) the control specimens were soaked in a saliva-like (SL) solution (2) the specimens received either 10-minute or 1-hour treatment with CPRS and (3) the specimens were treated with viscous CPRS, containing carboxymethyl cellulose (CMC) gel, for 8 hours. The SEM observations revealed that the control specimens were covered with a thin layer of plate-like crystals indicative of octacalcium phosphate (OCP). No significant penetration of the crystals into the dentinal tubules was detected. In CPRS group, the 10-minute treatment produced a 10 to 15 microns thick dense layer of precipitation consisting of needle-, rod-, and plate-like crystals. The 1-hour treatment produced a similar precipitation except that the crystals were mostly needle-like. A cross section view of the samples indicated remarkable penetration of the crystals into the tubules, thus providing significant obturation of tubule openings. Samples in the CMC-gel group were covered with an even more impervious layer of precipitation consisting of crystals of a variety of morphologies.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2557685

Sugawara, A; Chow, L C; Takagi, S; Nishiyama, M; Ohashi, M



Composition effects on the pH of a hydraulic calcium phosphate cement.  


The pH of a hydraulic calcium phosphate cement (HCPC) made of monocalcium phosphate monohydrate (Ca(H2PO4)2.H2O; MCPM), beta-tricalcium phosphate (beta-(Ca3(PO4)2; beta-TCP) and water was measured as a function of reaction time and composition at room temperature. During setting, the cement pH varies from very acidic pH values, i.e., 2.5, to almost neutral pH values, i.e., 6. The cement pH profile significantly depends on the initial cement composition. However, all profiles are characterized by a sharp initial decrease of the pH due to the dissolution of MCPM crystals and the precipitation of dicalcium phosphate dihydrate (CaHPO4. 2H2O; DCPD) crystals. With an excess of MCPM, the final pH stays low, and its value can be predicted from the initial composition of the cement and solubility data. With an excess of beta-TCP, the end pH is close to 5, which is much lower than 5.9, the value predicted by calculation. Results suggest that the difference may be due to the presence of impurities in the cement. Replacing MCPM by phosphoric acid renders the cement paste very acidic for the initial 30 s, but then the pH profile follows that obtained with MCPM. Adding pyrophosphate ions into the cement paste postpones the position of the pH minimum. The delay, which is proportional to the concentration of pyrophosphate ions, is thought to be due to the inhibiting action of pyrophosphate ions on the precipitation of DCPD crystals. PMID:15348818

Bohner, M; Van Landuyt, P; Merkle, H P; Lemaitre, J



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

NASA Astrophysics Data System (ADS)

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