Formation Of Carbonate Apatite Research Articles

Biophysical studies on bone cement composites based on polyester fumarate

AbstractPolypropylene fumarate (PPF) as unsaturated linear polyester crosslinked with three different monomers namely N‐vinyl pyrrolidone (NVP), methyl methacrylate (MMA), and a mixture of NVP/MMA (1 : 1 weight ratio) were prepared. The chemical structure of the PPF was characterized by means of 1H‐NMR, FTIR, as well as GPC. The mixture of PPF resin with the crosslinking monomers filled with (60, 65, and 70 wt %) of gypsum were also prepared as bone cement composites. The dielectric measurements carried out on these prepared samples at frequency range from 100 Hz–100 kHz indicate that the permittivity ε′ and dielectric loss ε″ follow the order NVP > NVP/MMA > MMA. Both parameters were found to decrease by increasing the percentage of gypsum. According to Fröhlich and Havriliak Nagami functions, the relaxation times obtained could be attributed, respectively, to Maxwell‐Wagner effect and to the relaxation process related to carboxyl, hydroxyl, and ester functions associated with main chain. The latter relaxation time was found to increase by increasing gypsum content, whereas the electrical conductivity was found to decrease. The mechanical data of the investigated samples containing 60 wt % gypsum is characterized by the best properties and the behavior of the composites follows the order found in the case of dielectric properties (NVP > NVP/MMA > MMA). Formation of carbonate apatite of composite samples loaded with 60 wt % gypsum after immersing the samples for 4 weeks in simulated body fluid (SBF) was confirmed by the dielectric measurements and FTIR spectroscopy. In addition, the weight loss and the mechanical properties for such systems were also studied. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Amorphous carbonated apatite formation on diamond-like carbon containing titanium oxide

Thin films of diamond-like carbon (DLC) containing titanium oxide (DLC-TiO x , x ≤ 2) were synthesized using a pulsed DC metal–organic plasma activated chemical vapor deposition (MOCVD) technique. X-ray photoelectron spectroscopy (XPS) results confirmed the presence of TiO 2 on the surface of the films. The compressive stress, elastic modulus and hardness of the films decreased with increasing Ti content. The water contact angle reduced from 62° for DLC to 45° for DLC-TiO x films containing 13.3 at.% of Ti. The biomimetic growth of amorphous carbonated apatite on the DLC-TiO x in simulated body fluid (SBF) was found and dependent on the Ti content of the film. UV light exposure prior to immersion in SBF increased the growth rate of apatite formation significantly as a result of increased hydrophilicity of the surface.

Osteoconductive HAp and TiO2Coatings on Titanium using Hydro-process

AbstractHydroxyapatite (Ca10(PO4)6(OH)2, HAp) and titanium dioxide (TiO2, titania) are of interest for bone-interfacing implant applications, because of their demonstrated osteoconductive properties. They were coated on the titanium implants using hydro-processes and investigated thein vivoperformance. HAp coatings were formed on cp-titanium plates or rods by the thermal substrate method in an aqueous solution included 0.3 mM Ca(H2PO4)2and 0.7 mM CaCl2. In the formation of carbonate apatite coating, CaHCO3was added to the solution, and in HAp/gelatin and HAp/collagen composite coatings, acid-soluble collagen (Type I) was added. The coating experiments were conducted at 313-433 K and pH = 8 for 15 or 30 min. Titania films were formed on the titanium implants by anodizing at < 100 V in 0.1 M H2SO4, H3PO4, and NaOH aqueous solutions at 298 K. The properties for the coated samples were studied using XRD, EDX, FT-IR, and SEM. And the surface roughness of titania coatings was measured. In in vivo evaluations, the coated rod specimens were implanted in rats femoral for 2 weeks, the osteoconduction on them was evaluated. Two weeks postimplantation, new bone formed on the coated and non-coated titanium rods in the cancellous bone and cortical bone, respectively. Bone-implant contact ratio, RB-I, which was used for the evaluation of new bone formation, was significantly depended on the compound formed on titanium implants, and also the coating processes.

Development of New Titanium Coating Material (CaTiO3-aC) with Modified Thermal Decomposition Method

We developed a novel method for titanium coating material using modified thermal decomposition technique, specifically focusing on presence of CaTiO3 and carbon C. Two layers of thin film coating composed of CaTiO3-amorphous carbon compound (CaTiO3-aC) and hydroxyapatite (HA) were generated on titanium surface. In this method, ratios of Ca/P as well as Ca/Ti, sintering temperature and sintering velocity were carefully planned. Within crystal structure of CaTiO3 granules, 4 atomic % of carbon in amorphous state was included. By our method, inclusion of carbon in HA suggested formation of carbonate apatite. Regarding with attachment-detachment experiment at titanium surface, adhesion strength was 2.5 times stronger in CaTiO3- aC/HA coating substrate as compared to HA only coating material. Results of the novel developed modified thermal decomposition method suggested that the 2 layers biomaterial composed of CaTiO3-aC (0.6 µm) and carbonate apatite-included HA (2.4 µm) can be used as a coating material on titanium surface.

Extracellular matrix proteins of dentine.

Bone and dentine extracellular matrix proteins are similar, consisting primarily of type I collagen, acidic proteins and proteoglycans. Although collagen forms the lattice for deposition of calcium and phosphate for formation of carbonate apatite, the non-collagenous proteins are believed to control initiation and growth of the crystals. Despite this similarity, dentine contains three unique proteins apparently absent from bone and other tissue: dentine phosphophoryn (DPP), dentine matrix protein 1 (DMP1) and dentine sialoprotein (DSP). DPP and DMP1 are acidic phosphoproteins probably involved in the control of mineralization processes. DPP may localize in gap regions of collagen and initiate apatite crystal formation by binding large quantities of calcium in a conformation that promotes this process. Extensive studies have been conducted in our laboratory on the nature, biosynthesis, localization and gene structure of DSP. Immunolocalization studies showed that rat DSP, a 53 kDa sialic acid-rich glycoprotein, was synthesized by young and mature odontoblasts, and by dental pulp cells and pre-ameloblasts, but not by ameloblasts, osteoblasts, chondrocytes or other cell types. The cDNA sequence indicated that DSP was a 366-residue protein with several potential N-glycosylation sites, as well as phosphorylation sites, but that the amino acid sequence was dissimilar to that of other known proteins. Northern blot analysis detected several mRNA species near 4.6 and 1.5 kb, indicative of alternative splicing events. Evidence for two DSP genes was obtained, further complicating this picture. Recent in situ hybridization studies utilizing rat and mouse molars and incisors indicated that DSP mRNA was expressed by young odontoblasts and odontoblasts in animals of all ages. Transcripts were also observed in pre-ameloblasts. The expression of DSP mRNA ceased when these cells matured to become secretory ameloblasts. DSP transcripts were not detected in osteoblasts or other cell types. The transient expression in pre-ameloblasts suggests a role of epithelial-mesenchymal interactions in the formation of the tooth.

In Vitro Formation of Nanocrystalline Carbonate Apatite – A Structural and Morphological Analogue of Atherosclerotic Plaques

AbstractThe in vitro formation of carbonate apatite in solutions with ion concentrations comparable to those in human serum was studied. The composition and morphology of the resulting apatite precipitate displayed a hierarchical assembly of elongated plate‐shaped nanocrystals of carbonate apatite analogous to previously characterized bioapatites formed in vivo. The main conclusion is that so‐called bioapatites may form in vitro and that precipitation inhibitors most likely are essential for the prevention of spontaneous calcification at normal human serum ion concentrations. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Influência dos íons K+ e Mg2+ na obtenção de apatitas biomiméticas

O crescimento da hidroxiapatita - HA, tanto no meio biológico quanto em soluções aquosas como a Synthetic Body Fluid - SBF, ocorre em meio contendo, além dos elementos Ca e P, elementos-traços essenciais tais como: Mg2+, HCO3-, K+ e Na+. Alguns destes elementos são conhecidos como inibidores do crescimento da HA, como Mg2+ e HCO3-. Neste trabalho, estudou-se a influência dos íons K+ e Mg2+ na formação de apatitas sobre substratos metálicos de Ti c.p. previamente tratados com NaOH 5M. Os efeitos destes íons no recobrimento obtidos, antes e após o tratamento térmico a 800ºC, foram analisados por microscopia eletrônica de varredura - MEV, espectroscopia de energia dispersiva de raios-X - EDX, difratometria de raios-X - DRX e espectroscopia no infravermelho - IV e mostraram que o efeito inibitório do Mg2+ na formação da HA se manifesta após o tratamento térmico. Diferentemente, o crescimento cristalino da HA não foi afetado pela presença do íon K+. Além disso, a formação de apatita carbonatada se deu também em soluções que não continham o íon CO3(2-) em sua composição.

In vivo dissolution behavior of various RF magnetron-sputtered Ca-P coatings on roughened titanium implants

RF magnetron sputter deposition was used to produce 0.1, 1.0 and 4.0 μm thick Ca-P coatings on TiO 2-blasted titanium discs. Half of the as-sputtered coated specimens were subjected to an additional infrared heat treatment for 30 s at 425–475°C. X-ray diffraction demonstrated that infrared radiation changed the amorphous 4 μm sputtered coatings into an amorphous–crystalline structure, while the amorphous 0.1 and 1 μm changed in a crystalline apatite structure with the presents of tetracalciumphosphate as a second phase. Scanning electron microscopically examination of the sputtered coatings revealed that annealing of the 4 μm thick coatings resulted in the appearance of small cracks. Subsequently, the discs were implanted subcutaneous into the back of rabbits. After 1, 4, 8 and 12 weeks of implantation, the implants were retrieved and prepared for histological and physicochemical evaluation. Histological evaluation revealed that the tissue response to all coated implants was very uniform. A very thin connective tissue capsule surrounded all implants. The capsule was usually free of inflammatory cells. At the interface, there was a close contact between the capsule and implant surface and no inflammatory cells were seen. Physicochemical evaluation showed that the 0.1 and 1 μm thick amorphous coatings had disappeared within 1 week of implantation. On the other hand, the 4 μm thick amorphous phase disappeared during the implantation periods, which was followed by the precipitation of a crystalline carbonate apatite. Further, at all implantation periods the heat-treated 1 and 4 μm thick coatings could be detected. Occasionally, a granular precipitate was deposited on the heat-treated 4 μm thick coating. Fourier transform infrared spectroscopy showed the formation of carbonate apatite (CO 3-AP) on the 4 μm thick amorphous coating and on the heat-treated specimens. On basis of our findings, we conclude that 1 μm thick heat-treated Ca-P sputter coating on roughened titanium implants appear to be of sufficient thickness to show bioactive properties, under in vivo conditions.

Hydroxy Carbonate Apatite Formation on Particulate Bioglass In Vitro as a Function of Time

The mechanism of bonding of bioactive glasses with living tissues has been reported to be associated with the development of a layer consisting of carbonate-containing hydroxyapatite similar to that of bone on the surface of the materials. This layer is also formed in vitro, in solutions with ion concentrations similar to those of human blood plasma, like SBF (Simulated Body Fluid). The development of HCAp (Hydroxy carbonate apatite) layer on the surface of a commercially available Bioglass® Synthetic Bone Graft Particulate (Perioglas®) after immersion in SBF solution using Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM) with associated Energy Dispersive Spectroscopy (EDS). PerioGlas® powder with particle size 20-63μm, pressed in a vacuum press in order to produce pellets. The pellets were soaked in SBF for 12, 18, 24 and 48 hours at 37°C. Results revealed the formation of an amorphous CaO-P2O5- rich layer on the surface of the specimens after 12 hours in the solution and a well crystalline HCAp layer after 24 hours immersion time.

Causes of phosphate stone formation and the importance of metaphylaxis by urinary acidification: a review.

The most important phosphates involved in urinary stone disease are carbonate apatite, brushite, and struvite. Overall, phosphate stones account for 12-20% of all stones, with a downward trend for struvite and an increase in carbonate apatite being observed in the last decade. The physicochemical basis for the formation of phosphate calculi is supersaturation. Once the solubility product has been exceeded, a metastable process of supersaturation begins, with slow crystalline growth. If a critical limit of supersaturation is exceeded, large-scale spontaneous precipitation of crystals occurs in a second stage. No urinary tract infection is involved in brushite stone formation. Although infection is not a prerequisite for the formation of carbonate apatite stones, infective conditions favor carbonate apatite formation. Struvite is the characteristic infection calculus, formed as a result of urinary tract infection with urease-producing bacteria. During the first episode of urinary stone disease a definitive diagnosis of the type of stone involved is very difficult without analysis of the latter by infrared spectroscopy or X-ray diffraction. In recurrent disease, appropriate treatment can be initiated on the basis of the previous stone analysis in the majority of cases. The best means of preventing recurrent disease involving any type of phosphate stone is definitive calculus removal by shock-wave lithotripsy, percutaneous stone removal, or open surgery (especially in children). Chemolysis via acidification of the urine with Suby G solution or hemicidrin supported by oral acidification, achieved by the metabolism of L-methionine, and antibiotic therapy (especially for infectious stones) are important adjuvant modalities of therapy. After therapy of phosphate stones, metaphylaxis involving controlled urinary acidification with L-methionine supports the treatment of infection and, at a pH value of less than 6.2 and urine dilution to 2.5 l/24 h, prevents the crystallization of struvite, brushite, and carbonate apatite.

Bone Bonding Studies and Implant Application of HA-G-Ti Functionally Gradient Composites

Bioactive composites (rod and stem) comprising hydroxyapatite containing glass coated titanium or titanium alloy, so-called HA-G-Ti functionally graded materials providing both the bioactivity potential due to the HA, biochemical stability of the glass and the mechanical strength of titanium or alloy (Ti-6Al-4V), were implanted into dog femur for a short / long period of time (1-12 / 27-76 months). The bonding behavior and the interface reaction between the composite implants and bone, as well as the biological reaction within the compositionally gradient HA-G coating layer, have been investigated. The implants were well integrated and fixed firmly with the surrounding bone without inflammatory reaction and bone resorption, and it was also found to be capable of maintaining strong bonding between the implant and bone even for a prolonged period of time (more than 27 months). The bonding of bone to the implant is resulted from not only the direct bonding, well-known as the bonding between bone and HA, but also bone ingrowth into the HA-G layer. It is noticeable in the case of a long period of implantation that the formation of carbonate apatite, closely associated with the dissolution and precipitation phenomena of the exposed and dispersed HA particles of the HA-G layer, and bone ingrowing into the interior of the HA-G layer appear to be deeply involved with in vivo bonding of the composite. We concluded that the HA-G-Ti composites are an excellent biomaterial, applicable to cementless prostheses and endosseous dental implants being able to survive sufficiently the lifetime of the implant.

In vivo dissolution behavior of various RF magnetron sputtered Ca‐P coatings

Radiofrequency magnetron sputter deposition was used to deposit Ca-P sputter coatings on titanium discs, and these coatings were implanted subcutaneously into the backs of rabbits. Half of the as-sputtered coatings were subjected to additional heat treatment for 2 h at 500°C. X-ray diffraction (XRD) demonstrated that annealing at 500°C changed the amorphous sputtered coating into an amorphous-crystalline apatite structure. Scanning electron microscopic (SEM) examination of the sputtered coatings showed excellent coverage of the substrate surface. Annealing of the 4-μm-thick coatings resulted in the appearence of small cracks. SEM demonstrated that until 4 weeks of implantation, all heat-treated coatings were present and all amorphous coatings were completely or mostly dissolved. Fourier transform infrared spectroscopy showed the formation of carbonate apatite (CO3-AP) on these specimens. Furthermore, XRD analysis showed that these CO3-AP precipitated coatings disappeared after 8 weeks of implantation. On the other hand, SEM inspection of these specimens revealed that the 4-μm heat-treated coating was still partially maintained and that small Ca-P crystals were present on the titanium substrate. On the basis of these results, we conclude that apparently 0.1 μm heat-treated Ca-P sputter coating is of sufficient thicknesses to stimulate carbonate apatite deposition under in vivo conditions. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 524–530, 1998.

In vivo dissolution behavior of various RF magnetron sputtered Ca-P coatings.

Radiofrequency magnetron sputter deposition was used to deposit Ca-P sputter coatings on titanium discs, and these coatings were implanted subcutaneously into the backs of rabbits. Half of the as-sputtered coatings were subjected to additional heat treatment for 2 h at 500 degrees C. X-ray diffraction (XRD) demonstrated that annealing at 500 degrees C changed the amorphous sputtered coating into an amorphous-crystalline apatite structure. Scanning electron microscopic (SEM) examination of the sputtered coatings showed excellent coverage of the substrate surface. Annealing of the 4-microm-thick coatings resulted in the appearance of small cracks. SEM demonstrated that until 4 weeks of implantation, all heat-treated coatings were present and all amorphous coatings were completely or mostly dissolved. Fourier transform infrared spectroscopy showed the formation of carbonate apatite (CO3-AP) on these specimens. Furthermore, XRD analysis showed that these CO3-AP precipitated coatings disappeared after 8 weeks of implantation. On the other hand, SEM inspection of these specimens revealed that the 4-microm heat-treated coating was still partially maintained and that small Ca-P crystals were present on the titanium substrate. On the basis of these results, we conclude that apparently 0.1 microm heat-treated Ca-P sputter coating is of sufficient thicknesses to stimulate carbonate apatite deposition under in vivo conditions.

Formation of carbonate apatite on calcium phosphate coatings containing silver ions.

The prerequisite for bioactive materials to bond to living bone is the formation of biologically equivalent carbonate apatite on their surfaces in the body. Calcium phosphate ceramic surfaces can be transformed to a biological apatite through a series of surface reactions including dissolution-precipitation and ion exchange. In the present work, apatite coatings with different crystallinity, compositions and crystal sizes, including a well-crystallized hydroxyapatite coating, were synthesized electrochemically and doped with silver ions in silver nitrate solution at room temperature. The formation of a new carbonate apatite on the surface of these coatings was investigated in an acellular simulated body fluid with ion concentrations comparable with those of human blood plasma, using scanning electron microscopy and Fourier transform-infrared spectroscopy. The results show that small quantities of silver ions incorporated into apatite coatings may have a strong stimulatory effect on the formation of carbonate apatite without adversely affecting the chemical stability of these coatings.

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.

Interactions between acidic matrix macromolecules and calcium phosphate ester crystals: relevance to carbonate apatite formation in biomineralization.

Control over crystal growth by acidic matrix macromolecules is an important process in the formation of many mineralized tissues. Earlier studies on the interactions between acidic macromolecules and carboxylate- and carbonate-containing crystals showed that the proteins recognize a specific stereochemical motif on the interacting plane. Here we show that a similar stereochemical motif is recognized by acidic mollusc shell macromolecules interacting with four different organic calcium phosphate-containing crystals. In addition, an acidic protein from vertebrate tooth dentin was also observed to recognize a similar structural motif in one of the crystals. The characteristic motif recognized is composed of rows of calcium ions and phosphates arranged in a plane defined by two free oxygens and a phosphorus atom emerging perpendicular to the affected face. These observations may have a direct bearing on the manner in which control over crystal growth is exerted on carbonate apatite crystals commonly found in vertebrate tissues.

Urolithiasis in children: current medical management.

The mechanism of stone formation in the urinary tract is reviewed. Diet, urinary tract infection and metabolic disorders account for the different epidemiological patterns of stone formation. The diagnosis and management of renal tract calculi are discussed. Calcium stones are associated with hypercalciuria, urine acidification defects, the use of furosemide in premature babies, hypercalcaemia, hyperoxaluria, hyperuricosuria, an alkaline urine and hypocitraturia. Uric acid stones occur in acid urine, from increased purine synthesis with lympho- or myeloproliferative disorders or from several inborn errors of purine metabolism which can also cause xanthine or dihydroxyadenine stones. Cystinuria, inherited as an autosomal recessive disorder is best treated with a low sodium diet, a fluid intake exceeding 40 ml/kg per day maintaining urine pH between 7.5 and 8 and, if necessary, with oral penicillamine. Oxalate stones occur in relation to diet, bowel disease and primary inherited defects in oxalate metabolism. Urinary tract infection causing struvite and carbonate apatite formation is the commonest cause of stones in Europe.