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PubMed2006

Nanofiber generation of hydroxyapatite and fluor-hydroxyapatite bioceramics.

In this study, we produced hydroxyapatite (HA) and fluor-hydroxyapatite (FHA) bioceramics as a novel geometrical form, the nanoscale fiber, for the biomedical applications. Based on the sol-gel precursors of the apatites, an electrospinning technique was introduced to generate nanoscale fibers. The diameter of the fibers was exploited in the range of a few micrometers to hundreds of nanometers (1.55 microm-240 nm) by means of adjusting the concentration of the sols. Through the fluoridation of apatite, the solubility of the fiber was tailored and the fluorine ions were well released from the FHA. The HA and FHA nanofibers produced in this study are considered to find potential applications in the biomaterials and tissue engineering fields.

Biocompatible Materials↗
PubMed2006

Void filling of tibia compression fracture zones using a novel resorbable nanocrystalline hydroxyapatite paste in combination with a hydroxyapatite ceramic core: first clinical results.

INTRODUCTION: It is a generally accepted standard surgical practice to fill-in the metaphyseal defect zones resulting from the reduction of tibia compression fractures. The development of various innovative bone substitutes is also currently on the increase. MATERIALS AND METHODS: In our prospective study, we used Ostim, a novel resorbable nanocrystalline hydroxyapatite paste, together with Cerabone, a solid hydroxyapatite ceramic, in combination with angularly stable osteosynthesis to treat 24 tibia compression fractures. Types B2 and B3, as well as types C2 and C3 fractures, according to the AO classification, were included in the study. RESULTS: The mean total range of joint motion in terms of flexion and extension was improved from the immediate postoperative value of 79 +/- 14 degrees to 97 +/- 13 degrees at 6 weeks after surgery, to 109 +/- 16 degrees at 3 months, and finally to 118 +/- 17 degrees at 1 year. In three patients, a delayed wound healing was observed as a local complication. CONCLUSION: The use of the Ostim and Cerabone combination is an effective method in treating tibia compression fractures with large defect zones left after reduction.

Absorbable Implants↗
PubMed2005

Effect of fluoridation of hydroxyapatite in hydroxyapatite-polycaprolactone composites on osteoblast activity.

Fluorine was administered to a system of hydroxyapatite (HA)/polycaprolactone (PCL) ceramic-polymer bioactive composites for applications as hard tissue regeneratives. The HA was fluoridated at different levels (5%, 25%, 50% and 75%) in order to produce the fluor-hydroxyapatite (FHA)/PCL composites. The osteoblastic cellular responses to the composites were examined in terms of the cell attachment, proliferation and differentiation as well as the expression of bone-associated genes. The amount of fluorine released from the composites was controlled by changing the degree of fluoridation, and the cellular responses were strongly influenced by the level of fluoridation. The MG63 cells on the FHA-PCL attached and proliferated at a similar level to those on HA-PCL. However, the fluoridation of HA increased significantly the alkaline phosphatase (ALP) activity and osteocalcin (OC) production by the cells on the composites, which was measured by an enzymatic assay. Moreover, the gene expression level of ALP and OC in the cells was up regulated on the FHA-PCL, which was confirmed semi-quantitatively by reverse transcriptase-polymerase chain reaction (RT-PCR) analysis. These findings on the fluorine-administered biological composites (FHA-PCL) suggested that fluorine plays a significant role in stimulating the bone derived cellular activity, and the FHA-PCL composites have high potential for use as hard tissue regeneratives.

Body Fluids↗
PubMed1996

Subchondral bone and cartilage repair with bioactive glasses, hydroxyapatite, and hydroxyapatite-glass composite.

The repair of an osteochondral defect in rabbit femur was studied with three kinds of bioactive glasses (BG), hydroxyapatite (HA), and hydroxyapatite-glass (HAG) composite. Seventy-two osteochondral defects were created in 18 rabbits. Sixty-four cylinders were implanted and eight defects were left empty as controls. Histomorphometry, scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDXA) were used for evaluation. Small osteochondral defects in rabbit femur found to heal themselves by regeneration. The three BGs, HA, and HAG led to direct lamellar bone repair of subchondral bone and restoration of articular surfaces mostly with hyalinelike cartilage in 12 weeks. However, the composition of the materials affects their behavior. Chondrogenesis took place earlier with the BGs than with HA. HAG degraded too much, glass 14 was too reactive and brittle, and the high alumina content in glass 11 disturbed its bone-bonding ability. Glass 7 and HA were the most balanced in the repair process. A special preparation method was used to retain soft tissues fairly unchanged and enable them to the observed together with hard tissues in SEM analysis.

Animals↗
PubMed1999

Effect of hydroxyapatite content on physical properties and connective tissue reactions to a chitosan-hydroxyapatite composite membrane.

The present study investigated the effect on certain physical properties of adding various amounts of hydroxyapatite (HAP) to chitosan sol. Also investigated were connective tissue reactions to a composite membrane that is being developed for possible use in guided tissue regeneration and for the limitation of HA particle migration at sites of implantation. The physical properties evaluated were shrinkage, tensile strength, hardness, calcium ion release, and morphology. Assessment of physical properties indicated that a ratio of HA to chitosan sol of 4/11 by weight is optimal in the preparation of the composite membrane. Subperiosteal implantation of the membranes over rat calvaria revealed that the membranes were well tolerated, with fibrous encapsulation and occasional areas of osteogenesis. Increasing the hydroxyapatite content seems to enhance membrane degradation.

Animals↗
PubMed1995

Comparison of the release of growth hormone from hydroxyapatite, heat-treated hydroxyapatite, and fluoroapatite coatings on titanium.

Hydroxyapatite (HA), heat-treated hydroxyapatite (HAH), and fluorapatite (FA) coatings on titanium were loaded with human growth hormone (GH), and the subsequent release was monitored in vitro. The amount of GH released was significantly increased from the HA coating that had received a post-plasma-spraying heat treatment prior to incorporation of the growth hormone. Scanning electron microscopy was used to assess the surfaces of the ceramic coatings prior and postincubation with GH. Surface changes were observed on the HA and HAH coatings but not on the FA coatings after incubation with GH. Osteoblast-like cells were grown on the coatings and maintained in culture. Scanning electron microscopy was used to study the morphology of the cells and the interaction of the cells with the ceramic coatings. We used thymidine uptake and DNA content to determine the relative rates of cell division on the different coatings; the optimum rate of cell proliferation was observed on the HAH coating loaded with 0.1 IU/mL GH.

Apatites↗
PubMed2004

Ultrastructural comparison of hydroxyapatite and silicon-substituted hydroxyapatite for biomedical applications.

Silicon-substituted hydroxyapatite (Si-HA) has been shown to lead to significantly increased rates of bone apposition when compared with phase-pure hydroxyapatite (HA) bioceramic implants (Patel N, et al. J Mater Sci Mater Med 2002;13:1199-1206). However, uncertainty remains about the mechanism by which Si increases the in vivo bioactivity. In this study, defect structures in Si-HA were observed and characterized for the first time using high-resolution transmission electron microscopy. Using tilting experiments and the g. b = 0 criterion for invisibility, the Burgers vectors of dislocations in phase-pure HA and 0.8 wt % Si-HA were characterized to be screw and mixed in character. Dislocations were observed in both pure HA and 0.8 wt % Si-HA with no significant difference in dislocation density between HA and Si-HA. However, our findings suggest that an increased number of triple junctions in Si-HA may have a significant role in increasing the solubility of the material and the subsequent rate at which bone apposes Si-HA ceramics.

Biocompatible Materials↗
PubMed2006

Human neutrophils reaction to the biodegraded nano-hydroxyapatite/collagen and nano-hydroxyapatite/collagen/poly(L-lactic acid) composites.

The impact of biodegraded nano-hydroxyapatite/collagen (nHAC) composite and nano-hydroxyapatite/collagen/poly(L-lactic acid) (nHAC/PLA) scaffold composite on neutrophils reaction was evaluated in vitro. Neutrophils were separated from human peripheral blood of healthy subjects. The nHAC and nHAC/PLA materials were immersed in the D-Hanks' Balanced Salt Solution (D-HBSS) for 1 day, 7 days and 2, 4, 8 weeks (37 degrees C) as testing solution, which mixed with the neutrophils for 1 h. Both of the nHAC and nHAC/PLA materials were shown the same cell survival rate as blank control, but the lactate dehydrogenase (LDH) and tumor necrosis factor alpha (TNF-alpha) released from the neutrophils were increased significantly after the 2 weeks in nHAC sample. The possible reason relied on the high concentration of calcium due to the quick biodegradation of the nHAC material. Before 2 weeks, the LDH value of nHAC/PLA is higher than that of nHAC sample that corresponded to the initial PLA degradation in vitro. This study provided the biocompatibility test of neutrophils other than common methods, such as osteoblastic cells for biomimetic materials. Moreover, it demonstrated the calcium concentration stimulating effect for cytokine release from neutrophils.

Biocompatible Materials↗
PubMed2004

Hydroxyapatite and fluor-hydroxyapatite layered film on titanium processed by a sol-gel route for hard-tissue implants.

A double-layered coating, consisting of a hydroxyapatite (HA) outer film and a fluor-hydroxyapatite (FHA) inner film, was produced on a Ti substrate by a sol-gel route to improve the biocompatibility and functionality of the system. Dissolution behavior of and in vitro cellular responses to the layered film were investigated. Calcium nitrate and triethyl phosphite were used for calcium and phosphate precursors, respectively, and ammonium fluoride was added as a fluorine-ion source for FHA. The FHA layer was deposited on Ti by spin coating and subsequent heat treatment at 550 degrees C for 30 min in air, and then the HA layer was laid down over the FHA-coated Ti under the same conditions. After heat treatment, characteristic apatite structures and phases were developed on both FHA and HA films. The cross-section view of the HA/FHA film clearly showed a double-layered structure on Ti with each layer approximately 0.6-0.8-microm thickness. The coating layer was highly uniform and dense, and adhered to Ti substrate strongly with an adhesion strength of about 40 MPa. The in vitro solubility of the HA/FHA layered film in a physiological solution was between that of HA and FHA pure film, and the dissolution profile was quite biphasic, that is, an initial rapid period and a slowdown with increasing time, reflecting the gradient solubility of the fast HA outer structure/slow FHA inner structure. The human osteoblast-like HOS TE85 cells cultured on the HA/FHA layered film attached, spread, and grew favorably. The proliferation rate of the cells on the layered film was significantly higher (considered at p < 0.05 for n = 6) than that on Ti substrate and was similar to that on pure HA film. The alkaline phosphatase (ALP) activity and osteocalcin (OC) produced by the cells on the layered film were significantly higher (considered at p < 0.05 for n = 6) than those on Ti substrate. Moreover, the ALP and OC levels of cells on the layered film showed the trends of HA outer/FHA inner structure with respect to culture period, that is, HA initially and FHA later. These observations suggest that the HA/FHA layered film on Ti obtained by a sol-gel route possesses gradient functionality in terms of solubility and cellular responses, and find that those parameters can be tailored for specific use in hard-tissue implants.

Biocompatible Materials↗
PubMed1997

The Crystallization of Fluorapatite in the Presence of Hydroxyapatite Seeds and of Hydroxyapatite in the Presence of Fluorapatite Seeds

The kinetics of growth of crystals induced by hydroxyapatite (HAP) seed crystals in supersaturated solutions of fluorapatite and of fluorapatite (FAP) seed crystals in supersaturated solutions of hydroxyapatite have been studied using the constant composition method. The reactions were investigated at relative supersaturations ranging from sigmaFAP = 0.99 to 12.0 at pH 6.5 and for HAP, sigmaHAP = 3.6 to 12.6 at pH 7.4. In FAP-supersaturated solutions, this phase was nucleated at the HAP surfaces and underwent growth at a rate more than three times greater than that on FAP seed crystals of equivalent surface area. Transmission electron microscopy (TEM) and electron diffraction imaging clearly demonstrated that the new needle-like HAP phase originated at the FAP surface with the 002 planes of HAP growing on FAP. In contrast, the mutual orientation of FAP crystallization on HAP seed crystals could not be established. Interfacial energies of FAP, HAP, and octacalcium phosphate (OCP) microcrystals against aqueous solutions were obtained by using a thin-layer wicking technique. The interfacial energy values measured in pure aqueous solutions were 18.5, 9.0, and 4.3 mJ m-2 for FAP, HAP, and OCP, respectively. The much smaller value for OCP as compared with the other phases may explain why this phase has been so frequently implicated as a possible precursor to the formation of apatite, especially in biological mineralization reactions.

Journal Article↗
PubMed2006

Ten-year results of ALIZE acetabular cup with hydroxyapatite coating and AURA hydroxyapatite-coated stem in total hip arthroplasty.

One hundred seven total hip arthroplasties were done between 1991 and 1992 with ALIZE acetabular cup with hydroxyapatite coating (Biomet France, Valence, France) and AURA hydroxyapatite-coated stem (Biomet France) in 107 patients. The articulation was ceramic on polyethylene for 102 patients and metal on polyethylene for the remaining 5 patients. The mean follow-up of the series was 8.4 +/- 2.5 years. The mean preoperative Merle d'Aubigné hip functional score was 10.6 +/- 3 vs 15.8 +/- 1.8 at the latest follow-up. Sixty-three patients were alive for the long-term follow-up at a mean of 9.67 +/- 0.25 years. Of the patients, 98.5% were satisfied or very satisfied at the latest follow-up. Five revisions were documented in these series: 1 for acetabular loosening, 2 for traumatic ceramic head fracture, 1 for polyethylene replacement, and 1 for stem replacement due to bone fracture. The mean wear rate was 0.076 +/- 0.043 mm/y (<0.1 mm/y considered as the normal wear rate). The overall survival rate at 10 years was 95.6% +/- 2.1% using revision of either component as the end point.

Acetabulum↗
PubMed2004

Laser surface modification of hydroxyapatite and glass-reinforced hydroxyapatite.

Surface treatment of materials with excimer laser radiation often results in the formation of a rough columnar or cone-shaped surface topography, which leads to a considerable increase in the surface area. As a result, the search for a non-porous bioactive material with adequate mechanical properties and a high surface to volume ratio, similar to porous materials, which could be used for drug delivery in the treatment of periodontitis, justified assessing excimer laser surface treatment to promote controlled roughning of hydroxyapatite (HA) and glass-reinforced hydroxyapatite (GR-HA). A KrF excimer laser with 248 nm radiation wavelength and 30 ns pulse duration was used for surface modification. The laser treatment was carried out in air, using wide ranges of radiation fluence and number of laser pulses. In order to identify the physico-chemical changes induced by the laser treatment and the column formation mechanisms in these materials, the treated surfaces were characterised by laser profilometry, scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier transform infra-red spectroscopy (FTIR). Laser processing induced the formation of a surface topography consisting of cone-shaped features. The constitution of the surface layer was also modified, as revealed by FTIR, XPS and XRD. This work has shown that laser surface modification increases the surface area of HA and GR-HA and is a promising technique to increase the reactivity and drug delivery capability of both materials.

Biocompatible Materials↗
PubMed1998

Binding properties of streptococcal glucosyltransferases for hydroxyapatite, saliva-coated hydroxyapatite, and bacterial surfaces.

The binding specificities of Streptococcus glucosyltransferase (Gtf) B, C and D for hydroxyapatite (HA), saliva-coated hydroxyapatite (SHA), and bacterial surfaces were examined. For HA beads the following values were obtained: (K = affinity; N = number of binding sites) GtfB, K = 46 x 10(5) ml/mumol, N = 0.65 x 10(-6) mumol/m2; GtfC, K = 86 x 10(5) ml/mumol, N = 4.42 x 10(-6) mumol/m2.; GtfD, K = 100 x 10(5) ml/mumol, N = 0.83 x 10(-6) mumol/m2. For SHA beads, the following values were obtained: GtfB, K = 14.7 x 10(5) ml/mumol, N = 1.03 x 10(-6) mumol/m2; GtfC, K = 21.3 x 10(5) ml/mumol, N = 3.66 x 10(-6) mumol/m2; GtfD, K = 1.73 x 10(5) ml/mumol, N = 8.88 x 10(-6) mumol/m2. The binding of GtfB to SHA beads was reduced in the presence of parotid saliva, but the binding of GtfC and D was unaffected. The binding of GtfB to SHA in the presence of parotid saliva supplemented with GtfC and D was reduced when compared with its binding to SHA in the presence of parotid saliva alone. In contrast, te binding of GtfC and SHA was unaffected when parotid saliva was supplemented with the other Gtf enzymes. GtfB bound to several bacterial strains (Strep, mutans GS-5, Actinomyces viscosus OMZ105E and Lactobacillus casei 4646) in an active form, while GtfC and D did not bind to bacterial surfaces. It is concluded that of the three Gtf enzymes, GtfC has the highest affinity for HA and SHA surfaces and can adsorb on the the SHA surface in the presence of the other two enzymes. GtfD also binds to SHA in the presence of the other enzymes but has a very low affinity for the surface. GtfB does not bind to SHA in the presence of the other Gtf enzymes but binds avidly to bacterial surfaces in an active form. Therefore, GtfC most probably binds to apatitic surfaces, while GtfB binds to bacterial surfaces.

Actinomyces viscosus↗
PubMed2003

Synthesis and characterization of hydroxyapatite, fluoride-substituted hydroxyapatite and fluorapatite.

Powders of hydroxyapatite (HA), partially fluoride-substituted hydroxyapatite (fHA), and fluorapatite (FA) were synthesized in house using optimum methods to achieve relatively pure powders. These powders were assessed by the commonly used bulk techniques of X-ray diffraction (XRD), Fourier transform infra-red (FTIR) and FT-Raman spectroscopies, inductively coupled plasma atomic emission spectroscopy (ICP-AES), and F-selective electrode. In addition, the current study has employed transmission electron microscopy (TEM), involving morphological observation, electron diffraction and energy-dispersive X-ray spectrometry (EDX), as an effective analytical technique to evaluate the powders at a microscopic level. The HA and fHA particles were elongated platelets about 20 x 60 nm in size, while FA particles were over twice this size. Calcination of the HA and fHA powders at 1000 degrees C for 1 h resulted in increased grain size and crystallinity. The calcined fHA material appeared to possess a crystal structure intermediate between HA and FA, as evidenced by the (3 0 0) peak shift in XRD, as well as by the position of the hydroxyl bands in the FTIR spectra. This result was consistent with electron diffraction of individual particles. Small levels of impurities in some of the powders were identified by EDX and electron diffraction, and the carbonate content was detected by FTIR. The use of TEM in conjunction with the bulk techniques has allowed a more thorough assessment of the apatites, and has enabled the constituents in these closely related apatite powders to be identified.

Journal Article↗
PubMed1993

Comparison of bone-implant interface shear strength of solid hydroxyapatite and hydroxyapatite-coated titanium implants.

The interface shear strength of uncoated Ti-6Al-4V, dense sintered hydroxyapatite (HA), and HA-coated Ti-6Al-4V were compared. Interface shear strength was determined using a transcortical push-out model in dogs 4 and 12 weeks after implantation. The interface shear strength of dense sintered HA and HA-coated Ti-6Al-4V was significantly higher than that of uncoated Ti-6Al-4V (P < .001). There was no significant difference between the interface shear strength of dense sintered HA and HA-coated Ti-6Al-4V. After the push-out test for HA-coated implants, the regions fractured at the bone-coating interface and at the coating-titanium interface coexisted at 4 weeks after implantation. At 12 weeks, the fracture site was, in all cases, the HA coating-titanium interface, and, in a few samples, fractures inside the coating layer also were visible.

Alloys↗
PubMed1987

Selective adsorption of porcine-amelogenins onto hydroxyapatite and their inhibitory activity on hydroxyapatite growth in supersaturated solutions.

The selective adsorption of amelogenins onto synthetic hydroxyapatite (HA) and their inhibitory activity on the seeded HA crystal growth were investigated using enamel proteins obtained from the outer layer of immature porcine-enamel (soft, cheeselike in consistency) of developing permanent incisors. Special interests were paid to the effect of a postsecretory degradation of the original amelogenin(s) on their adsorption and inhibitory activity. In the adsorption studies, it was apparent that the originally secreted amelogenin (25 K), proline, and histidine-rich protein (2a), as well as the higher molecular weight components (60-90 K), showed a strong adsorption affinity onto the HA. This adsorption of protein 2a was related to its inhibition of the crystal growth of seeded HA in a dilute supersaturated solution. On the other hand, the partially degraded product (20 K) of amelogenins, protein 2b, lost the high adsorption affinity onto the HA, and consequently showed no significant inhibitory activity. The observed selective adsorption of protein 2a onto HA was apparent at pH 6.0 and pH 7.4 even in the presence of dissociative solvents, such as 3 M urea or 2 and 4 M guanidine-HCl; however, this selective behavior was sensitive to changes in pH, and was not displayed at pH values of 7.8 or 10.8. The results suggest that the originally secreted amelogenin 2a may play an active role in amelogenesis, and that enamel mineralization could be regulated by the secretion of amelogenins and their inactivation through partial enzymic degradation, prior to their complete removal.

Adsorption↗
PubMed1985

The effect of osteocalcin on in vitro lipid-induced hydroxyapatite formation and seeded hydroxyapatite growth.

Osteocalcin, the bone gamma-carboxy glutamic acid containing protein, is one of the major noncollagenous proteins both synthesized and localized in bony tissue. Previously, investigators have suggested, based on the in vitro and in vivo properties of this protein, that it may be involved in controlling initiation of mineralization and/or hydroxyapatite (HA) growth. In this study, the in vitro effects of osteocalcin on lipid-induced HA formation, and HA seeded growth were compared. Although osteocalcin inhibited the growth of HA, as indicated by the osteocalcin concentration-dependent decreases in the first order rate constant, kCa, osteocalcin had no effect on lipid-induced calcification, kCa remaining constant at .033 h-1. Binding studies revealed that osteocalcin did not associate with the lipid macromolecules tested (phosphatidyl serine, phosphatidyl inositol, and the Ca-acidic phospholipid-phosphate (Ca-PL-PO4) complexes prepared from these phospholipids) although the protein bound to HA with high affinity. These data suggest that a) osteocalcin is quite distinct from the gamma carboxy glutamic acid containing clotting proteins which have a high affinity for both the acidic phospholipids and for HA, and b) that osteocalcin has little effect on the initial Ca-PL-PO4-dependent formation of HA.

Calcium-Binding Proteins↗
PubMed1986

Adhesion of carboxylate cements to hydroxyapatite. I. The effect of the structure of aliphatic carboxylates on their uptake by hydroxyapatite.

An investigation was made into the effect of the structure and functionality of aliphatic carboxylates on their sorption onto hydroxyapatite with a view to ascertaining factors affecting the adhesion of polyacrylate cements to tooth materials. In general, the amount of carboxylate sorbed was found to increase with the number of groups contained in the molecule. Thus, polyacrylate was found to be much more strongly sorbed than low molecular weight species. Sorption of the low molecular weight species appeared to be related to stereochemical factors rather than to the stability constants of their calcium chelates.

Adsorption↗