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1

Hollow hydroxyapatite microspheres as a device for controlled delivery of proteins  

PubMed Central

Hollow hydroxyapatite (HA) microspheres were prepared by reacting solid microspheres of Li2O–CaO–B2O3 glass (106–150 ?m) in K2HPO4 solution, and evaluated as a controlled delivery device for a model protein, bovine serum albumin (BSA). Reaction of the glass microspheres for 2 days in 0.02 M K2HPO4 solution (pH = 9) at 37°C resulted in the formation of biocompatible HA microspheres with a hollow core diameter equal to 0.6 the external diameter, high surface area (~100 m2/g), and a mesoporous shell wall (pore size ?13 nm). After loading with a solution of BSA in phosphate-buffered saline (PBS) (5 mg BSA/ml), the release kinetics of BSA from the HA microspheres into a PBS medium were measured using a micro bicinchoninic acid (BCA) protein assay. Release of BSA initially increased linearly with time, but almost ceased after 24–48 h. Modification of the BSA release kinetics was achieved by modifying the microstructure of the as-prepared HA microspheres using a controlled heat treatment (1–24 h at 600–900°C). Sustained release of BSA was achieved over 7–14 days from HA microspheres heated for 5 h at 600°C. The amount of BSA released at a given time was dependent on the concentration of BSA initially loaded into the HA microspheres. These hollow HA microspheres could provide a novel inorganic device for controlled local delivery of proteins and drugs. PMID:21290170

Fu, Hailuo; Day, Delbert E.; Brown, Roger F.

2011-01-01

2

Preparation of Hydroxyapatite Coating on the Surface of Hollow Glass Microspheres Using a Biomimetic Process  

NASA Astrophysics Data System (ADS)

Microcarrier culture technology has attached more attention, especially for scale-up cell culture in the filed of tissue engineering. The present work introduces a microcarrier with hydroxyapatite (HA) on hollow glass microsphere. Hollow glass microspheres with a main composition of SiO2 (55-65 wt.%), Al2O3 (26-35 wt.%), were pretreated by NaOH, on which hydroxyapatite coating was deposited by biomimetic process. The phase composition and morphology were characterized by X-ray diffractometer (XRD), Fourier transform infrared (FTIR) spectroscope, field emission scanning electron microscope (FE-SEM) and high resolution transmission electron microscope (HRTEM), respectively. The results showed that after immersion for 15 days in 1.5 SBF, the uniform and dense HA coating was formed and it has porous surface and low crystallinity.

Jiao, Yan; Yang, Hai-Ying; Zhang, Ying-Long; Duan, Rong-Shuai; Lu, Yu-Peng

2014-07-01

3

Hydroxyapatite-armored poly(?-caprolactone) microspheres and hydroxyapatite microcapsules fabricated via a Pickering emulsion route.  

PubMed

Hydroxyapatite (HAp) nanoparticle-armored poly(?-caprolactone) (PCL) microspheres were fabricated via a "Pickering-type" emulsion solvent evaporation method in the absence of any molecular surfactants. It was clarified that the interaction between carbonyl/carboxylic acid groups of PCL and the HAp nanoparticles at an oil-water interface played a crucial role in the preparation of the stable Pickering-type emulsions and the HAp nanoparticle-armored microspheres. The HAp nanoparticle-armored PCL microspheres were characterized in terms of size, size distribution, morphology, and chemical compositions using scanning electron microscopy, laser diffraction, energy dispersive X-ray microanalysis, and thermogravimetric analysis. The presence of HAp nanoparticles at the surface of the microspheres was confirmed by scanning electron microscopy and energy dispersive X-ray microanalysis. Pyrolysis of the PCL cores led to the formation of the corresponding HAp hollow microcapsules. PMID:22364710

Fujii, Syuji; Okada, Masahiro; Nishimura, Taiki; Maeda, Hayata; Sugimoto, Tatsuya; Hamasaki, Hiroyuki; Furuzono, Tsutomu; Nakamura, Yoshinobu

2012-05-15

4

Preparation of hollow hydroxyapatite microspheres by the conversion of borate glass at near room temperature  

SciTech Connect

Hollow hydroxyapatite microspheres, consisting of a hollow core and a porous shell, were prepared by converting Li{sub 2}O-CaO-B{sub 2}O{sub 3} glass microspheres in dilute phosphate solution at 37 {sup o}C. The results confirmed that Li{sub 2}O-CaO-B{sub 2}O{sub 3} glass was transformed to hydroxyapatite without changing the external shape and dimension of the original glass object. Scanning electron microscopy images showed the shell wall of the microsphere was built from hydroxyapatite particles, and these particles spontaneously align with one another to form a porous sphere with an interior cavity. Increase in phosphate concentration resulted in an increase in the reaction rate, which in turn had an effect on shell wall structure of the hollow hydroxyapatite microsphere. For the Li{sub 2}O-CaO-B{sub 2}O{sub 3} glass microspheres reacted in low-concentration K{sub 2}HPO{sub 4} solution, lower reaction rate and a multilayered microstructure were observed. On the other hand, the glass microspheres reacted in higher phosphate solution converted more rapidly and produced a single hydroxyapatite layer. Furthermore, the mechanism of forming hydroxyapatite hollow microsphere was described.

Yao, Aihua, E-mail: aihyao@126.com [Institute of Bioengineering and Information Technology Materials, School of Materials Science and Engineering, Tongji University, Shanghai 200092 (China)] [Institute of Bioengineering and Information Technology Materials, School of Materials Science and Engineering, Tongji University, Shanghai 200092 (China); Ai, Fanrong; Liu, Xin; Wang, Deping; Huang, Wenhai; Xu, Wei [Institute of Bioengineering and Information Technology Materials, School of Materials Science and Engineering, Tongji University, Shanghai 200092 (China)] [Institute of Bioengineering and Information Technology Materials, School of Materials Science and Engineering, Tongji University, Shanghai 200092 (China)

2010-01-15

5

Hollow hydroxyapatite microspheres: a novel bioactive and osteoconductive carrier for controlled release of bone morphogenetic protein-2 in bone regeneration  

PubMed Central

The regeneration of large bone defects is a common and significant clinical problem. Limitations associated with existing treatments such as autologous bone grafts and allografts have increased the need for synthetic bone graft substitutes. The objective of this study was to evaluate the capacity of novel hollow hydroxyapatite (HA) microspheres to serve as a carrier for controlled release of bone morphogenetic-2 (BMP2) in bone regeneration. Hollow HA microspheres (106–150 ?m) with a high surface area (>100 m2/g) and a mesoporous shell wall (pore size 10–20 nm) were created using a glass conversion technique. The release of BMP2 from the microspheres into a medium composed of diluted fetal bovine serum in vitro was slow, but it occurred continuously for over 2 weeks. When implanted in rat calvarial defects for 3 or 6 weeks, the microspheres loaded with BMP2 (1 ?g/defect) showed a significantly better capacity to regenerate bone than those without BMP2. The amount of new bone in the defects implanted with the BMP2-loaded microspheres was 40% and 43%, respectively, at 3 and 6 weeks, compared to 13% and 17%, respectively, for the microspheres without BMP2. Coating the BMP2-loaded microspheres with a biodegradable polymer, poly(lactic-co-glycolic acid), reduced the amount of BMP2 released in vitro and, above a certain coating thickness, significantly reduced bone regeneration in vivo. The results indicate that these hollow HA microspheres could provide a bioactive and osteoconductive carrier for growth factors in bone regeneration. PMID:23747325

Xiao, Wei; Fu, Hailuo; Rahaman, Mohamed N.; Liu, Yonxing; Bal, B. Sonny

2013-01-01

6

Evaluation of bone regeneration in implants composed of hollow HA microspheres loaded with TGF– 1 in a rat calvarial defect model  

PubMed Central

Implants that serve simultaneously as an osteoconductive matrix and as a device for local growth factor delivery may be required for optimal bone regeneration in some applications. In the present study, hollow hydroxyapatite (HA) microspheres (106–150 ?m) in the form of three-dimensional (3D) scaffolds or individual (loose) microspheres were created using a glass conversion process. The capacity of the implants, with or without transforming growth factor- 1 (TGF- 1), to regenerate bone in a rat calvarial defect model was compared. The 3D scaffolds supported the proliferation and alkaline phosphatase activity of osteogenic MLO-A5 cells in vitro, showing their cytocompatibility. Release of TGF- 1 from the 3D scaffolds into phosphate-buffered saline ceased after 2–3 days when 30% of the growth factor was released. Bone regeneration in the 3D scaffolds and the individual microspheres increased with time from 6 to 12 weeks, but it was significantly higher (23%) in the individual microspheres than in the 3D scaffolds (15%) after 12 weeks. Loading with TGF-?1 (5 ?g/defect) enhanced bone regeneration in the 3D scaffolds and individual microspheres after 6 weeks, but had little effect after 12 weeks. 3D scaffolds and individual microspheres with larger HA diameter (150–250 ?m) showed better ability to regenerate bone. Based on these results, implants composed of hollow HA microspheres show promising potential as an osteoconductive matrix for local growth factor delivery in bone regeneration. PMID:23168225

Fu, Hailuo; Rahaman, Mohamed N.; Brown, Roger F.; Day, Delbert E.

2012-01-01

7

BMP2-loaded hollow hydroxyapatite microspheres exhibit enhanced osteoinduction and osteogenicity in large bone defects  

PubMed Central

The regeneration of large bone defects is an osteoinductive, osteoconductive, and osteogenic process that often requires a bone graft for support. Limitations associated with naturally autogenic or allogenic bone grafts have demonstrated the need for synthetic substitutes. The present study investigates the feasibility of using novel hollow hydroxyapatite microspheres as an osteoconductive matrix and a carrier for controlled local delivery of bone morphogenetic protein 2 (BMP2), a potent osteogenic inducer of bone regeneration. Hollow hydroxyapatite microspheres (100±25 ?m) with a core (60±18 ?m) and a mesoporous shell (180±42 m2/g surface area) were prepared by a glass conversion technique and loaded with recombinant human BMP2 (1 ?g/mg). There was a gentle burst release of BMP2 from microspheres into the surrounding phosphate-buffered saline in vitro within the initial 48 hours, and continued at a low rate for over 40 days. In comparison with hollow hydroxyapatite microspheres without BMP2 or soluble BMP2 without a carrier, BMP2-loaded hollow hydroxyapatite microspheres had a significantly enhanced capacity to reconstitute radial bone defects in rabbit, as shown by increased serum alkaline phosphatase; quick and complete new bone formation within 12 weeks; and great biomechanical flexural strength. These results indicate that BMP2-loaded hollow hydroxyapatite microspheres could be a potential new option for bone graft substitutes in bone regeneration. PMID:25609957

Xiong, Long; Zeng, Jianhua; Yao, Aihua; Tu, Qiquan; Li, Jingtang; Yan, Liang; Tang, Zhiming

2015-01-01

8

An in vitro investigation of plasma sprayed hydroxyapatite (HA) coatings produced with flame-spheroidized feedstock  

Microsoft Academic Search

The in vitro behaviour and characteristics of plasma sprayed hydroxyapatite (HA) coatings using flame-spheroidized HA feedstock powder on titanium alloy (Ti-6Al-4V) substrates were investigated in a simulated physiological environment as an attempt to reflect the actual incubational condition of an implant in a human body system. As-sprayed and heat-treated HA coatings were immersed in a simulated body fluid with ionic

S. W. K Kweh; K. A Khor; P Cheang

2002-01-01

9

5-Fluorouracil encapsulated HA/PLGA composite microspheres for cancer therapy.  

PubMed

5-Fluorouracil (5FU) was successfully entrapped within poly(lactide-co-glycolide) (PLGA) and hydroyapatite (HA) composite microspheres using the emulsification/solvent extraction technique. The effects of HA to PLGA ratio, solvent ratio as well as polymer inherent viscosity (IV) on encapsulation efficiency were investigated. The degradation and drug release rates of the microspheres were studied for 5 weeks in vitro in phosphate buffered solution of pH 7.4 at 37 °C. The drug release profile followed a biphasic pattern with a small initial burst followed by a zero-order release for up to 35 days. The initial burst release decreased with increasing HA content. The potential of HA in limiting the initial burst release makes the incorporation of HA into PLGA microspheres advantageous since it reduces the risk of drug overdose from high initial bursts. The linear sustained drug release profile over the course of 5 weeks makes these 5-FU-loaded HA/PLGA composite microparticles a promising delivery system for the controlled release of chemotherapy drugs in the treatment of cancer. PMID:22843166

Lin, Yuting; Li, Yan; Ooi, Chui Ping

2012-10-01

10

The Evaluation of Hydroxyapatite (HA) Coated and Uncoated Porous Tantalum for Biomedical Material Applications  

NASA Astrophysics Data System (ADS)

Porous tantalum has been used as an orthopedic implant for bone defects as it has a good corrosion resistance and fatigue behaviour properties. However, there are some reports on the rejection of porous Ta after the implantation. Those clinical cases refer to the less bioactivity of metallic-based materials. This study aims to evaluate hydroxyapatite coated and uncoated porous Tantalum in order to improve the biocompatibility of porous tantalum implant and osseointegration. Porous tantalum was used as metallic-base substrate and hydroxyapatite coating has been done using plasma-spraying technique. Scanning Electron Microscopy (SEM) and Field Emission Scanning Electron Microscopy (FESEM) techniques were utilizes to investigate the coating characteristics while Confocal Raman Microscopy to investigate the interface and image. The effect of coating to the corrosion behaviour was assessed by employing potentiodynamic polarization tests in simulated body fluid at 37±1 °C. Based on SEM and FESEM results, the morphologies as well the weight element consists in the uncoated and hydroxyapatite coated porous tantalum were revealed. The results indicated that the decrease in corrosion current density for HA coated porous Ta compared to the uncoated porous Ta. This study concluded that by coating porous tantalum with HA supports to decrease the corrosion rate of pure porous.

Safuan, Nadia; Sukmana, Irza; Kadir, Mohammed Rafiq Abdul; Noviana, Deni

2014-04-01

11

A new way of incorporating silicon in hydroxyapatite (Si-HA) as thin films.  

PubMed

Bioactive silicon-containing hydroxyapatite (Si-HA) thin films that can be used as coatings for bone tissue replacement have been developed. A magnetron co-sputtering technique was used to deposit Si-HA films up to 700 nm thick on titanium substrates, with a silicon level up to 1.2 wt%. X-ray diffraction demonstrated that annealing transformed the as-deposited Si-HA films which were amorphous, into a crystalline HA structure. A human osteoblast-like (HOB) cell model was used to determine the biocompatibility of these films. HOB cells were seen to attach and grow well on the Si-HA films, and the metabolic activity of HOB cells on these films was observed to increase with culture time. Furthermore, mineralisation of the cell layers was observed after 8 weeks of culture. Based on the present findings, Si-HA of different film compositions demonstrate bioactive properties in-vitro, and indicate the potential as biocoatings for a wide variety of medical implants including load-bearing applications such as the femoral stem of hip replacement implants. PMID:15875250

Thian, E S; Huang, J; Best, S M; Barber, Z H; Bonfield, W

2005-05-01

12

Hollow hydroxyapatite microspheres/chitosan composite as a sustained delivery vehicle for rhBMP-2 in the treatment of bone defects.  

PubMed

Composite scaffold comprised of hollow hydroxyapatite (HA) and chitosan (designated hHA/CS) was prepared as a delivery vehicle for recombinating human bone morphogenetic protein-2 (rhBMP-2). The in vitro and in vivo biological activities of rhBMP2 released from the composite scaffold were then investigated. The rhBMP-2 was firstly loaded into the hollow HA microspheres, and then the rhBMP2-loaded HA microspheres were further incorporated into the chitosan matrix. The chitosan not only served to bind the HA microspheres together and kept them at the implant site, but also effectively modified the release behavior of rhBMP-2. The in vitro release and bioactivity analysis confirmed that the rhBMP2 could be loaded and released from the composite scaffolds in bioactive form. In addition, the composite scaffolds significantly reduced the initial burst release of rhBMP2, and thus providing prolonged period of time (as long as 60 days) compared with CS scaffolds. In vivo bone regenerative potential of the rhBMP2-loaded composite scaffolds was evaluated in a rabbit radius defect model. The results revealed that the rate of new bone formation in the rhBMP2-loaded hHA/CS group was higher than that in both negative control and rhBMP2-loaded CS group. These observations suggest that the hHA/CS composite scaffold would be effective and feasible as a delivery vehicle for growth factors in bone regeneration and repair. PMID:25578692

Yao, Ai-Hua; Li, Xu-Dong; Xiong, Long; Zeng, Jian-Hua; Xu, Jun; Wang, De-Ping

2015-01-01

13

Sr-containing hydroxyapatite: morphologies of HA crystals and bioactivity on osteoblast cells.  

PubMed

A series of Sr-substituted hydroxyapatites (HA), of general formula Ca(10-x)Srx(PO4)6(OH)2, where x=2 and 4, were synthesized by solid state methods and characterized extensively. The reactivity of these materials in cell culture medium was evaluated, and the behavior towards MG-63 osteoblast cells (in terms of cytotoxicity and proliferation assays) was studied. Future in vivo studies will give further insights into the behavior of the materials. A paper by Lagergren et al. (1975), concerning Sr-substituted HA prepared by a solid state method, reports that the presence of Sr in the apatite composition strongly influences the apatite diffraction patterns. Zeglinsky et al. (2012) investigated Sr-substituted HA by ab initio methods and Rietveld analyses and reported changes in the HA unit cell volume and shape due to the Sr addition. To further clarify the role played by the addition of Sr on the physico-chemical properties of these materials we prepared Sr-substituted HA compositions by a solid state method, using different reagents, thermal treatments and a multi-technique approach. Our results indicated that the introduction of Sr at the levels considered here does influence the structure of HA. There is also evidence of a decrease in the crystallinity degree of the materials upon Sr addition. The introduction of increasing amounts of Sr into the HA composition causes a decrease in the specific surface area and an enrichment of Sr-apatite phase at the surface of the samples. Bioactivity tests show that the presence of Sr causes changes in particle size and/or morphology during soaking in MEM solution; on the contrary the morphology of pure HA does not change after 14 days of reaction. The presence of Sr, as Sr-substituted HA and SrCl2, in cultures of human MG-63 osteoblasts did not produce any cytotoxic effect. In fact, Sr-substituted HA increased the proliferation of osteoblast cells and enhanced cell differentiation: Sr in HA has a positive effect on MG-63 cells. In contrast, Sr ions alone, at the concentrations released by Sr-HA (1.21-3.24 ppm), influenced neither cell proliferation nor differentiation. Thus the positive effects of Sr in Sr-HA materials are probably due to the co-action of other ions such as Ca and P. PMID:23827552

Aina, Valentina; Bergandi, Loredana; Lusvardi, Gigliola; Malavasi, Gianluca; Imrie, Flora E; Gibson, Iain R; Cerrato, Giuseppina; Ghigo, Dario

2013-04-01

14

Preparation and evaluation of a new radiopharmaceutical for radiosynovectomy, 111Ag-labelled hydroxyapatite (HA) particles.  

PubMed

Many radionuclides, namely, 166Ho, 90Y, 165Dy, 32P, 198Au, 186Re, etc. have been used for radio-synovectomy. Silver-111 (T 1/2 7.45 d) can be produced in a nuclear reactor and is a potential therapeutic radionuclide decaying by beta(-) emission (92% E beta max=1.037MeV and 8% by beta(-) decay associated with emission of gamma-rays (E gamma=245.4keV, I gamma=1.33%; E gamma=342.1keV, I gamma=6.7%)). Because of the production feasibility and favourable nuclear properties, 111Ag may find use as a suitable radionuclide for radio-synovectomy. Hydroxyapatite (HA), Ca10(PO4)6(OH)2 is one of the preferred particulates for this application. In this work, [111Ag]Ag-HA particulates were successfully prepared with high-labelling yield ( approximately 97%) at various pH values. The radiochemical purity of the [111Ag]Ag-HA particles was 99.9%. Stability studies for 7 days showed that the [111Ag]Ag-HA particles retained their stability. gamma camera images at 15 min, 24h and 5 d after injection of the particles into rabbits revealed the retention of the activity in the synovial joints of the knee, thereby indicating excellent in vivo stability of [111Ag]Ag-HA particles. Therefore, [111Ag]Ag-HA particles would be a potential therapeutic agent in the management of arthritis. PMID:17951062

Chattopadhyay, Sankha; Vimalnath, K V; Saha, Sujata; Korde, Aruna; Sarma, H D; Pal, Sujit; Das, Malay K

2008-03-01

15

Effect of hydroxyapatite-containing microspheres embedded into three-dimensional magnesium phosphate scaffolds on the controlled release of lysozyme and in vitro biodegradation  

PubMed Central

The functionality of porous three-dimensional (3D) magnesium phosphate (MgP) scaffold was investigated for the development of a novel protein delivery system and biomimetic bone tissue engineering scaffold. This enhancement can be achieved by incorporation of hydroxyapatite (HA)-containing polymeric microspheres (MSs) into a bulk MgP matrix, and a paste-extruding deposition (PED) system. In this work, the amount of MS and HA was precisely controlled when manufacturing MS-embedded MgP (MS/MgP) composite scaffolds. The main influence was researched in terms of in vitro lysozyme-release, in vitro biodegradation, mechanical properties, and in vitro calcification. The controlled release of lysozyme was indicated, while showing graded release patterns according to HA content. The composite scaffolds degraded gradually with MS content and degradation time. Due to the effect of HA inclusion, the higher HA-containing MS/MgP scaffolds could, not only delay the biodegradation process but also, compensate for the possible loss of mechanical properties. In this regard, it is reasonable to confirm the inverse relationship between biodegradation and corresponding compressive properties. In order to encourage bioactivity and osteoconductivity, the MS/MgP composite scaffolds were subjected to simulated body fluid treatment. Calcium deposition was, in turn, improved with increasing MS and HA content over time. This quantitative result was also proved using morphological and elemental analysis. In summary, a significant transformation of a monolithic MgP scaffold was directed toward a multifunctional bone tissue engineering scaffold equipped with controlled protein delivery, biodegradability, and bioactivity. PMID:25214782

Lee, Jongman; Yun, Hui-suk

2014-01-01

16

Preparation and bioevaluation of 166Ho labelled hydroxyapatite (HA) particles for radiosynovectomy.  

PubMed

The preparation of 166Ho labeled hydroxy apatite (HA) particles for radiosynovectomy applications is described in this paper. 166Ho was prepared by the irradiation of Ho2O3 at a flux of 1.8 x 10(13) neutrons/cm2/s for about 7 days. The irradiation resulted in the production of approximately 17 GBq of 166Ho activity at the end of six hours post end of bombardment and the corresponding specific activity was approximately 3-4 GBq/mg of Ho. The irradiated target was dissolved in 0.1 N HCl solution. Radionuclidic purity was ascertained by high resolution gamma ray spectrometry. HA particles were synthesized and characterized by X-ray diffractometry. Labeling studies were carried out with and without citric acid as a transchelating agent. Radiochemical yield and purity of the 166Ho-HA particles were ascertained by paper chromatography and by paper electrophoresis techniques. Labeling yield of >98% could be achieved at pH 7, with 40 mg of HA particles and 8.6 microg of Ho. 166Ho-HA particles prepared were stable for 72 h. Bio-evaluation of the 166Ho -HA particles were carried out by injecting approximately 74 MBq dose in 200 microL (approximately 8 mg of 166Ho-HA particles) directly into the arthritis induced knee joints as well as into the healthy knee joints of white New Zealand rabbits. Images of the injected joints of the animals recorded using a gamma camera at regular intervals showed good retention. Blood samples were collected from the animals and activity assayed in a scintillation detector. Experiments were also carried out under identical conditions in normal rabbits. In both the cases, it was observed that there was no significant extra articular leakage of the injected activity over the study period of 96 h post injection. PMID:11823125

Unni, P R; Chaudhari, P R; Venkatesh, Meera; Ramamoorthy, N; Pillai, M R A

2002-02-01

17

Novel silicon-doped hydroxyapatite (Si-HA) for biomedical coatings: an in vitro study using acellular simulated body fluid.  

PubMed

Magnetron co-sputtering was used to produce silicon-doped hydroxyapatite (Si-HA) as coatings intended for potential applications such as orthopedic and dental implants. It was found that the crystallinity of the as-sputtered coatings increased after annealing, resulting in a nanocrystalline apatite structure. Subsequently, the bioactivity of the coatings was evaluated in an acellular simulated body fluid (SBF). Physicochemical evaluation demonstrated that a carbonate-containing apatite layer, which is essential for bonding at the bone/implant interface, was formed on the coating surfaces after immersion in SBF between 4 and 7 days. The annealed coatings exhibited enhanced bioactivity and chemical stability under physiological conditions, as compared with the as-sputtered coatings. It is proposed that the rate at which the carbonate-containing apatite layer forms is dependent on the scale factor of the structure. A nanocrystalline structure can provide a higher number of nucleation sites for the formation of apatite crystallites, leading to a more rapid precipitation of carbonate-containing apatite layer. This work shows that Si-HA coatings offer considerable potential for applications in hard tissue replacement, owing to their ability to form a carbonate-containing apatite layer rapidly. PMID:16080174

Thian, E S; Huang, J; Best, S M; Barber, Z H; Bonfield, W

2006-02-01

18

Hydroxyapatite (HA) coating appears to be of benefit for implant durability of tibial components in primary total knee arthroplasty  

PubMed Central

Background It is unclear whether there is a clinical benefit to adding hydroxyapatite (HA) coatings to total knee implants, especially with the tibial component, where failure of the implant more often occurs. A systematic review of the literature was undertaken to identify all prospective randomized trials for determining whether the overall clinical results (as a function of durability, function, and adverse events) favored HA-coated tibial components. Methods A comprehensive literature search was performed for the years 1990 to September 16, 2010. We restricted our search to randomized controlled trials involving participants receiving either an HA-coated tibia or other forms of tibial fixation. The primary outcome measures evaluated were durability, function, and acute adverse events. Results Data from 926 evaluable primary total knee implants in 14 studies were analyzed. Using an RSA definition for durability, HA-coated tibial components (porous or press-fit) without screw fixation were less likely to be unstable at 2 years than porous and cemented metal-backed tibial components (RR = 0.58, 95% CI: 0.34–0.98; p = 0.04, I2 = 39%, M-H random effects model). There was no significant difference in durability, as measured from revision and evaluated at 2 and 8–10 years, between groups. Also, functional status using different validated measures showed no significant difference at 2 and 5 years, no matter what measure was used. Lastly, there was no significant difference in adverse events. Limitations included small numbers of evaluable patients (? 50) in 7 of the 14 trials identified, and a lack of “hard” evidence of durability with need for replacement (i.e. frank failure, pain, or loss of functionality). Interpretation In patients > 65 years of age, an HA-coated tibial implant may provide better durability than other forms of tibial fixation. Larger trials should be undertaken comparing the long-term durability, function, and adverse events of HA-coated implants with those of other porous-coated tibial implants in younger, more active OA patients. PMID:21657975

2011-01-01

19

Bioresorbable devices made of forged composites of hydroxyapatite (HA) particles and poly-L-lactide (PLLA): Part I. Basic characteristics.  

PubMed

Compounds that had neither calcined nor sintered hydroxyapatite (u-HA) particles (particulate size 0.2-20 microns, averaging 3.0 microns, Ca/P = 1.69, and containing CO3(2-) uniformly distributed in a poly-L-lactide (PLLA, Mv: 400 KDa) matrix with a content of 20-50 wt% (with 10% increment) were reinforced into composites by a forging process, which was a unique compression molding, and were then machined on a lathe in order to produce practical radiopaque internal bone fixation devices having high mechanical strength which was maintained during bony union, total resorbability and bioactivity such as bone bonding capability and osteoconductivity. From the results of measurement of various mechanical properties, it was confirmed that the composites generally showed the highest mechanical strength among this type of reinforced bioceramic fibers or particles/bioresorbable polymer composite known to date. The bending strength (Sb) of about 270 MPa was far higher value than that for cortical bone, and the modulus (Eb) of 12 GPa was almost equivalent to that for cortical bone. In particular, the impact strength (Si) was extremely high at about two times the value (166 KJ/m2) of polycarbonate. The in vitro change in Sb, Mv (viscosity average molecular weight), Mw/Mn (molecular weight distribution) and crystallinity, and their relationship with each other was also examined by immersing samples in a phosphate buffer solution (PBS). An immediate decrease in the initial Mv could be found in composites with high u-HA contents (30-50 wt%), although a time-lag stage for degradation where the initial Mv hardly changes was apparent in cases of PLLA-only or in a composite with a low u-HA content (20 wt%). The Sb changed with corresponding decremental curves for the Mv and retained over 200 MPa for up to 24 weeks, the period of time necessary for full bony union, so that the composite satisfied initial mechanical strengths while maintaining them for as long as necessary for internal bone fixation devices. These results supported the idea that there is a difference in the degradation process such that PLLA alone required a period of time to achieve the possibility of hydrolysis into the inner side, whereas composites with high u-HA contents (30-50 wt%) immediately filled with water through to the inner side and were hydrolyzed homogeneously. Many hydroxyapatite crystals deposited and grew on the surface after 3-6 d and generously covered the surface with a fairly thick layer after 7 d of post-immersion in simulated body fluid (SBF) as evaluated by means of energy dispersive X-ray (EDX). This suggested the ability of the radiopaque composites to bond to bone. Since the composites were dense and had ultra-high strength, and the processability was so excellent, many kinds of fine and accurate screws, pins, plates, and other internal bone fixation devices for orthopedic, oral and maxillofacial, craniofacial, and plastic and reconstructive surgeries could be produced by machining treatment. These devices have potential applications for clinical use following the assessment of adaptation during in vivo studies. PMID:10226712

Shikinami, Y; Okuno, M

1999-05-01

20

Microspheres  

NASA Technical Reports Server (NTRS)

Vital information on a person's physical condition can be obtained by identifying and counting the population of T-cells and B-cells, lymphocytes of the same shape and size that help the immune system protect the body from the invasion of disease. The late Dr. Alan Rembaum developed a method for identifying the cells. The method involved tagging the T-cells and B-cells with microspheres of different fluorescent color. Microspheres, which have fluorescent dye embedded in them, are chemically treated so that they can link with antibodies. With the help of a complex antibody/antigen reaction, the microspheres bind themselves to specific 'targets,' in this case the T-cells or B-cells. Each group of cells can then be analyzed by a photoelectronic instrument at different wavelengths emitted by the fluorescent dyes. Same concept was applied to the separation of cancer cells from normal cells. Microspheres were also used to conduct many other research projects. Under a patent license Magsphere, Inc. is producing a wide spectrum of microspheres on a large scale and selling them worldwide for various applications.

1990-01-01

21

Analyzing the behavior of a porous nano-hydroxyapatite/polyamide 66 (n-HA/PA66) composite for healing of bone defects  

PubMed Central

The aim of this study was to analyze the behavior of the porous nano-hydroxyapatite/polyamide 66 (n-HA/PA66) composite grafted for bone defect repair through a series of biological safety experiments, animal experiments, and a more than 5-year long clinical follow-up. The biological safety experiments, carried out in accordance with the Chinese Guo Biao and Tolerancing (GB/T)16886 and GB/T16175, revealed that porous n-HA/PA66 composite had no cytotoxicity, no sensitization effect, no pyrogenic reaction, and that its hemolysis rate was 0.59% (less than 5%). Rabbit models of tibia defects with grafted porous n-HA/PA66 composite were established. After 2 weeks, the experiment showed that osteogenesis was detected in the porous n-HA/PA66 composite; the density of new bone formation was similar to the surrounding host bone at 12 weeks. After 26 weeks, the artificial bone rebuilt to lamellar bone completely. In the clinical study, a retrospective review was carried out for 21 patients who underwent serial radiographic assessment after treatment with porous n-HA/PA66 composite grafts following bone tumor resection. All wounds healed to grade A. No postoperative infections, delayed deep infection, nonspecific inflammation, rejection, or fractures were encountered. At a mean follow-up of 5.3 years, the mean Musculoskeletal Tumor Society’s (MSTS) 93 score was 29.3 points (range: 28–30 points) and mean radiopaque density ratio was 0.77±0.10. The radiologic analysis showed that porous n-HA/PA66 composite had been completely incorporated with the host bone about 1.5 years later. In conclusion, this study indicated that the porous n-HA/PA66 composite had biological safety, and good biocompatibility, osteoinduction, and osseointegration. Thus, the porous n-HA/PA66 composite is an ideal artificial bone substitute and worthy of promotion in the field. PMID:24531621

Xiong, Yan; Ren, Cheng; Zhang, Bin; Yang, Hongsheng; Lang, Yun; Min, Li; Zhang, Wenli; Pei, Fuxing; Yan, Yonggang; Li, Hong; Mo, Anchun; Tu, Chongqi; Duan, Hong

2014-01-01

22

Tricalcium phosphate/hydroxyapatite (TCP-HA) bone scaffold as potential candidate for the formation of tissue engineered bone  

PubMed Central

Background & objectives: Various materials have been used as scaffolds to suit different demands in tissue engineering. One of the most important criteria is that the scaffold must be biocompatible. This study was carried out to investigate the potential of HA or TCP/HA scaffold seeded with osteogenic induced sheep marrow cells (SMCs) for bone tissue engineering. Methods: HA-SMC and TCP/HA-SMC constructs were induced in the osteogenic medium for three weeks prior to implantation in nude mice. The HA-SMC and TCP/HA-SMC constructs were implanted subcutaneously on the dorsum of nude mice on each side of the midline. These constructs were harvested after 8 wk of implantation. Constructs before and after implantation were analyzed through histological staining, scanning electron microscope (SEM) and gene expression analysis. Results: The HA-SMC constructs demonstrated minimal bone formation. TCP/HA-SMC construct showed bone formation eight weeks after implantation. The bone formation started on the surface of the ceramic and proceeded to the centre of the pores. H&E and Alizarin Red staining demonstrated new bone tissue. Gene expression of collagen type 1 increased significantly for both constructs, but more superior for TCP/HA-SMC. SEM results showed the formation of thick collagen fibers encapsulating TCP/HA-SMC more than HA-SMC. Cells attached to both constructs surface proliferated and secreted collagen fibers. Interpretation & conclusions: The findings suggest that TCP/HA-SMC constructs with better osteogenic potential compared to HA-SMC constructs can be a potential candidate for the formation of tissue engineered bone. PMID:23852290

Sulaiman, Shamsul Bin; Keong, Tan Kok; Cheng, Chen Hui; Saim, Aminuddin Bin; Idrus, Ruszymah Bt. Hj

2013-01-01

23

Poly-L-lactic acid — hydroxyapatite (PLLA-HA) bioabsorbable interference screws for tibial graft fixation in anterior cruciate ligament (ACL) reconstruction surgery: MR evaluation of osteointegration and degradation features  

Microsoft Academic Search

Purpose  We evaluated with magnetic resonance imaging (MRI) the degradation and osteointegration features of a new type of bioabsorbable\\u000a interference (BioRCI) screw composed of poly-L-lactic acid and hydroxyapatite (PLLA-HA) used for tibial graft fixation in\\u000a anterior cruciate ligament (ACL) reconstruction.\\u000a \\u000a \\u000a \\u000a Materials and methods  Thirty-one patients underwent arthroscopic surgery for ACL reconstruction using doubled gracilis and semitendinosus tendons\\u000a fixed to the tibial tunnel

L. Macarini; P. Milillo; A. Mocci; R. Vinci; G. C. Ettorre

2008-01-01

24

Long-term conversion of 45S5 bioactive glass-ceramic microspheres in aqueous phosphate solution.  

PubMed

The conversion of 45S5 glass and glass-ceramics to a hydroxyapatite (HA)-like material in vitro has been studied extensively, but only for short reaction times (typically <3 months). In this paper, we report for the first time on the long-term conversion of 45S5 glass-ceramic microspheres (designated 45S5c) in an aqueous phosphate solution. Microspheres of 45S5c (75-150 ?m) were immersed for 10 years at room temperature (~25 °C) in K(2)HPO(4) solution with a concentration of 0.01 M or 1.0 M, and with a starting pH of 7.0 or 9.5. The reacted 45S5c microspheres and solutions were analyzed using structural and analytical techniques. Only 25-45 vol% of the 45S5c microspheres were converted to an HA-like material after the 10 year reaction. In solutions with a starting pH of 9.5, an increase in the K(2)HPO(4) concentration from 0.01 to 1.0 M resulted in a doubling of the volume of the microspheres converted to an HA-like material but had little effect on the composition of the HA-like product. In comparison, reaction of the 45S5c microspheres in the solution with a starting pH of 7.0 resulted in an HA-like product in the 0.01 M K(2)HPO(4) solution but a calcium pyrophosphate product, Ca(10)K(4)(P(2)O(7))(6).9H(2)O, in the 1.0 M solution. The consequences of these results for the long-term use of 45S5 glass-ceramics in biomedical applications are discussed. PMID:22415362

Fu, Hailuo; Rahaman, Mohamed N; Day, Delbert E; Huang, Wenhai

2012-05-01

25

Robotic deposition of model hydroxyapatite scaffolds with multiple architectures and multiscale porosity for bone tissue engineering.  

PubMed

Model hydroxyapatite (HA) scaffolds with porosities spanning multiple length scales were fabricated by robocasting, a solid freeform fabrication technique based on the robotic deposition of colloidal pastes. Scaffolds of various architectures including periodic, radial, and superlattice structures were constructed. Macropores (100-600 microm) were designed by controlling the arrangement and spacing between rods of HA. Micropores (1-30 microm) and submicron pores (less than 1 microm) were produced within the rods by including polymer microsphere porogens in the HA pastes and by controlling the sintering of the scaffolds. These model scaffolds may be used to systematically study the effects of scaffold porosity on bone ingrowth processes both in vitro and in vivo. PMID:17295231

Dellinger, Jennifer G; Cesarano, Joseph; Jamison, Russell D

2007-08-01

26

Multi-functional P(3HB) microsphere/45S5 Bioglass-based composite scaffolds for bone tissue engineering.  

PubMed

Novel multi-functional P(3HB) microsphere/45S5 Bioglass-based composite scaffolds exhibiting potential for drug delivery were developed for bone tissue engineering. 45S5 Bioglass-based glass-ceramic scaffolds of high interconnected porosity produced using the foam-replication technique were coated with biodegradable microspheres (size<2 microm) made from poly(3-hydroxybutyrate), P(3HB), produced using Bacillus cereus SPV. A solid-in-oil-in-water emulsion solvent extraction/evaporation technique was used to produce these P(3HB) microspheres. A simple slurry-dipping method, using a 1 wt.% suspension of P(3HB) microspheres in water, dispersed by an ultrasonic bath, was used to coat the scaffold, producing a uniform microsphere coating throughout the three-dimensional scaffold structure. Compressive strength tests confirmed that the microsphere coating slightly enhanced the scaffold mechanical strength. It was also confirmed that the microsphere coating did not inhibit the bioactivity of the scaffold when immersed in simulated body fluid (SBF) for up to 4 weeks. The hydroxyapatite (HA) growth rate on P(3HB) microsphere-coated 45S5 Bioglass composite scaffolds was very similar to that on the uncoated control sample, qualitatively indicating similar bioactivity. However, the surface topography of the HA surface layer was affected as shown by results obtained from white light interferometry. The roughness of the surface was much higher for the P(3HB) microsphere-coated scaffolds than for the uncoated samples, after 7 days in SBF. This feature would facilitate cell attachment and proliferation. Finally, gentamycin was successfully encapsulated into the P(3HB) microspheres to demonstrate the drug delivery capability of the scaffolds. Gentamycin release kinetics was determined using liquid chromatography-mass spectrometry. The release of the drug from the coated composite scaffolds was slow and controlled when compared to the observed fast and relatively uncontrolled drug release from the bone scaffold (without microsphere coating). Thus, this unique multifunctional bioactive composite scaffold has the potential to enhance cell attachment and to provide controlled delivery of relevant drugs for bone tissue engineering. PMID:20056174

Francis, Lydia; Meng, Decheng; Knowles, Jonathan C; Roy, Ipsita; Boccaccini, Aldo R

2010-07-01

27

Hydroxyapatite degradation and biocompatibility  

NASA Astrophysics Data System (ADS)

Hydroxyapatite (HA) is widely used as a bioactive ceramics since it forms a chemical bonding to bone. The disadvantage of this material is its poor mechanical properties. HA can be degraded in body, which is the reason for its bioactivity, but too fast degradation rate could cause negative effects, such as macrophage present, particle generation, and even implant clinical failure. HA degradation rate will be greatly changed under many conditions: purity, HA form (i.e. bulk form, porous form, coating, or HA/polymer composites), microstructure, implant site, body conditions, etc. Although much work has been done in HA properties and application areas, the HA degradation behavior and mechanism under these different conditions are still not clear. In this research, three aspects of HA degradation have been studied: (1) Two very common impurities---Tri-Calcium Phosphate (TCP) and Calcium Oxide and their influences on HA degradation in vitro and in vivo, (2) influence of HA/polymer composite form on HA degradation, (3) HA material particle generation and related mechanism. From the in vitro and in vivo tests on bulk HA disks with various Ca/P ratios, HA degradation can clearly be found. The degradation level is different in different Ca/P ratio samples as well as in different test environments. In same test environment, non-stoichiometric HA samples have higher degradation rate than stoichiometric HA. HA/PMMA composite design successfully intensifies HA degradation both in vitro and in vivo. Grain boundary damage can be found on in vivo test samples, which has not been clearly seen on bulk HA degraded surface. HA particle generation is found in in vitro and in vivo HA/PMMA composite surface and in vivo bulk HA surface. Sintering temperature and time does affect HA grain size, and this affect HA degradation rate. Intergranular fracture is found in a several micron zone close to the Ca/P ratio 1.62 and 1.67 sample degraded surfaces. At Ca/P ratio greater than 1.667, after HA degradation in water, solution pH increases because of CaO presence.

Wang, Haibo

28

Molten Salt Synthesis of Calcium Hydroxyapatite Whiskers A. Cuneyt Tas*,  

E-print Network

Molten Salt Synthesis of Calcium Hydroxyapatite Whiskers A. Cu¨neyt Tas¸*, Department hydroxyapatite (HA) whiskers and crystals were produced by the route of molten salt synthesis. The effects. A tentative X-ray diffraction pattern was proposed for the HA whiskers. Molten salt synthesis with a K2SO4

Tas, A. Cuneyt

29

Injection moulded hydroxyapatite ceramics.  

PubMed

The injection moulding of hydroxyapatite (HA) and properties (relative density, shrinkage, microstructure, thermal strength and phase composition) of HA ceramics sintered at temperatures of 1373-1773 K were studied. Particles of oval shape and size of 0.5 microns were most suitable for injection moulding. Polymer/HA mixture contained 63 vol% of the HA powder. Maximum relative density (98.7%) and shrinkage (16%) of HA ceramics were obtained at a sintering temperature of 1523 K. Maximum flexural strength (60 MPa) of HA ceramics occurred at a sintering temperature of 1473 K. The strength of these ceramics decreased at sintering temperatures higher than 1473 K. Loss in strength was owing to the grain growth and decomposition of HA ceramics. The relationship between grain size and strength is described by the equation: sigma = 53.3d1/2. The calculated activation energy of grain growth obtained was 215kJ mol-1 K-1. The decomposition of HA to alpha-tricalcium phosphate was important at temperatures greater than 1573 K. PMID:8889072

Cihlár, J; Trunec, M

1996-10-01

30

Polyacrolein microspheres  

NASA Technical Reports Server (NTRS)

Microspheres of acrolein homopolymers and copolymer with hydrophillic comonomers such as methacrylic acid and/or hydroxyethylmethacrylate are prepared by cobalt gamma irradiation of dilute aqueous solutions of the monomers in presence of suspending agents, especially alkyl sulfates such as sodium dodecyl sulfate. Amine or hydroxyl modification is achieved by forming adducts with diamines or alkanol amines. Carboxyl modification is effected by oxidation with peroxides. Pharmaceuticals or other aldehyde reactive materials can be coupled to the microspheres. The microspheres directly form antibody adducts without agglomeration.

Rembaum, Alan (Inventor)

1987-01-01

31

Polyacrolein microspheres  

NASA Technical Reports Server (NTRS)

Microspheres of acrolein homopolymers and copolymer with hydrophillic comonomers such as methacrylic acid and/or hydroxyethylmethacrylate are prepared by cobalt gamma irradiation of dilute aqueous solutions of the monomers in presence of suspending agents, especially alkyl sulfates such as sodium dodecyl sulfate. Amine or hydroxyl modification is achieved by forming adducts with diamines or alkanol amines. Carboxyl modification is effected by oxidation with peroxides. Pharmaceuticals or other aldehyde reactive materials can be coupled to the microspheres. The microspheres directly form antibody adducts without agglomeration.

Rembaum, Alan (Inventor)

1986-01-01

32

Polyacrolein microspheres  

NASA Technical Reports Server (NTRS)

Microspheres of acrolein homopolymers and co-polymer with hydrophillic comonomers such as methacrylic acid and/or hydroxyethylmethacrylate are prepared by cobalt gamma irradiation of dilute aqueous solutions of the monomers in presence of suspending agents, especially alkyl sulfates such as sodium dodecyl sulfate. Amine or hydroxyl modification is achieved by forming adducts with diamines or alkanol amines. Carboxyl modification is effected by oxidation with peroxides. Pharmaceuticals or other aldehyde reactive materials can be coupled to the microspheres. The microspheres directly form antibody adducts without agglomeration.

Rembaum, Alan (Inventor)

1983-01-01

33

Nutrient-substituted hydroxyapatites: synthesis and characterization  

NASA Technical Reports Server (NTRS)

Incorporation of Mg, S, and plant-essential micronutrients into the structure of synthetic hydroxyapatite (HA) may be advantageous for closed-loop systems, such as will be required on Lunar and Martian outposts, because these apatites can be used as slow-release fertilizers. Our objective was to synthesize HA with Ca, P, Mg, S, Fe, Cu, Mn, Zn, Mo, B, and Cl incorporated into the structure, i.e., nutrient-substituted apatites. Hydroxyapatite, carbonate hydroxyapatite (CHA), nutrient-substituted hydroxyapatite (NHA), and nutrient-substituted carbonate hydroxyapatite (NCHA) were synthesized by precipitating from solution. Chemical and mineralogical analysis of precipitated samples indicated a considerable fraction of the added cations were incorporated into HA, without mineral impurities. Particle size of the HA was in the 1 to 40 nm range, and decreased with increased substitution of nutrient elements. The particle shape of HA was elongated in the c-direction in unsubstituted HA and NHA but more spherical in CHA and NCHA. The substitution of cations and anions in the HA structure was confirmed by the decrease of the d[002] spacing of HA with substitution of ions with an ionic radius less than that of Ca or P. The DTPA-extractable Cu ranged from 8 to 8429 mg kg-1, Zn ranged from 57 to 1279 mg kg-1, Fe from 211 to 2573 mg kg-1, and Mn from 190 to 1719 mg kg-1, depending on the substitution level of each element in HA. Nutrient-substituted HA has the potential to be used as a slow-release fertilizer to supply micronutrients, S, and Mg in addition to Ca and P.

Golden, D. C.; Ming, D. W.

1999-01-01

34

Wrapping hydroxyapatite implants.  

PubMed

Hydroxyapatite (HA) implants currently are most commonly wrapped in fresh unprocessed human donor sclera before implantation to facilitate entry into the orbital space and allow extraocular muscle attachment. Autologous temporalis fascia or autologous fascia lata are alternatives, but prolong surgery time and require a second operative site. Recently, a number of other wraps, such as processed human pericardium, processed human fascia lata, processed human sclera, bovine pericardium and expanded polytetrafluoroethylene [e-PTFE], have being marketed. Although they also facilitate implant placement, they can be costly. Polygalactin (Vicryl, Ethicon, Somerville, NJ) mesh is another readily available wrap that is easy to use and cost effective. To obtain a high success rate with this wrap, the polygalactin mesh wrapped HA implant must be moistened and seated into the orbit properly. If it is not, exposure may occur, which may explain why some surgeons shy away from its use. The proper technique is reviewed in this paper. PMID:10334031

Jordan, D R; Klapper, S R

1999-05-01

35

Dip Coating of Calcium Hydroxyapatite on Ti-6Al-4V Substrates and A. Cuneyt Tas*,  

E-print Network

Dip Coating of Calcium Hydroxyapatite on Ti-6Al-4V Substrates Bora Mavis and A. Cu¨neyt Tas. The main inorganic phase of human bone is calcium hydroxyapatite (Ca10(PO4)6- (OH)2, HA). To achieve better been used for sample characterization. I. Background CHEMICALLY precipitated calcium hydroxyapatite (Ca

Tas, A. Cuneyt

36

Polishing and whitening properties of toothpaste containing hydroxyapatite  

Microsoft Academic Search

Toothpastes containing hydroxyapatite (HA-toothpaste) have demonstrated efficacy in preventing caries, treating hypersensitivity and curing periodontal diseases, however, their effects on whitening teeth have not been investigated. In this study, the polishing and whitening properties of hydroxyapatite contained toothpastes were evaluated in a combined experimental and clinical study. The polishing properties were evaluated in artificial teeth by polishing with different toothpastes,

Motoo Niwa; Tsutomu Sato; Wei Li; Hideo Aoki; Hideki Aoki; Takehiku Daisaku

2001-01-01

37

Osteopenic bone cell response to strontium-substituted hydroxyapatite  

Microsoft Academic Search

Ionic substitution is a powerful tool to improve the biological performance of calcium phosphate based materials. In this\\u000a work, we investigated the response of primary cultures of rat osteoblasts derived from osteopenic (O-OB) bone to strontium\\u000a substituted hydroxyapatite (SrHA), and to hydroxyapatite (HA) as reference material, compared to normal (N-OB) bone cells.\\u000a Strontium (Sr) and calcium (Ca) cumulative releases in

E. Boanini; P. Torricelli; M. Fini; A. Bigi

38

STEM and EDXS characterisation of physico-chemical reactions at the periphery of sol-gel derived Zn-substituted hydroxyapatites  

E-print Network

properties of biocompatibility and bioactivity hydroxyapatite (HA) is highly used as bone substitutes Zn-substituted hydroxyapatites during interactions with biological fluids E. JALLOT1* , J.M. NEDELEC2+ doped hydroxyapatite. Zn2+ ions substitute for Ca2+ cations in the HA structure and four Zn

Boyer, Edmond

39

Fluorescent microspheres  

NASA Technical Reports Server (NTRS)

Latex particles with attached antibodies have potential biochemical and environmental applications. Human red blood cells and lymphocytes have been labeled with fluorescent microspheres by either direct or indirect immunological technique. Immunolatex spheres can also be used for detecting and localizing specific cell surface receptors. Hormones and toxins may also be bondable.

Rembaum, A.

1978-01-01

40

Hydroxyapatite\\/poly( ?-caprolactone) composite coatings on hydroxyapatite porous bone scaffold for drug delivery  

Microsoft Academic Search

Hydroxyapatite (HA) porous scaffold was coated with HA and polycaprolactone (PCL) composites, and antibiotic drug tetracycline hydrochloride was entrapped within the coating layer. The HA scaffold obtained by a polymeric reticulate method, possessed high porosity (?87%) and controlled pore size (150–200?m). Such a well-developed porous structure facilitated usage in a drug delivery system due to its high surface area and

Hae-Won Kim; Jonathan C. Knowles; Hyoun-Ee Kim

2004-01-01

41

Electrical characterization of hydroxyapatite-based bioceramics  

Microsoft Academic Search

This paper studies the AC conductivity and permittivity of hydroxyapatite (HA)-based ceramics from 0.1Hz–1MHz at temperatures from room temperature to 1000°C. HA-based ceramics were prepared either as dense ceramics or in porous form with interconnected porosity and were sintered in either air or water vapour. Samples were thermally cycled to examine the influence of water desorption on AC conductivity and

J. P. Gittings; C. R. Bowen; A. C. E. Dent; I. G. Turner; F. R. Baxter; J. B. Chaudhuri

2009-01-01

42

Glass microspheres  

SciTech Connect

This patent describes a glass microsphere having a diameter of about 54 micrometers or less and adapted for radiation therapy of a mammal. The glass consists of essentially an yttrium oxide-aluminosilicate glass composition lying substantially within a quadrilateral region of the ternary composition diagram of the yttria-alumina-silica system, the quadrilateral region being defined by its four corners having the following combination of weight proportions of the components: 20% silica, 10% alumina, 70% yttria; 70% silica, 10% alumina, 20% yttria; 70% silica, 20% alumina, 10% yttria; and 20% silica, 45% alumina, 35% yttria, the glass having a chemical durability such that subsequent to irradiation and administration of the microsphere to the mammal, the mircosphere will not release a significant amount of yttrium-90 into the mammal's system.

Day, D.E.; Ehrhardt, G.J.

1988-12-06

43

Osteogenesis and Trophic Factor Secretion are Influenced by the Composition of Hydroxyapatite/Poly(Lactide-Co-Glycolide) Composite Scaffolds  

PubMed Central

The use of composite biomaterials for bone repair capitalizes on the beneficial aspects of individual materials while tailoring the mechanical properties of the composite. We hypothesized that substrate composition would modulate the osteogenic response and secretion of potent trophic factors by human mesenchymal stem cells (hMSCs). Composite scaffolds were prepared by combining nanosized hydroxyapatite (HA) and microspheres formed of poly(lactic-co-glycolic acid) (PLG) at varying ratios between 0:1 and 5:1. Scaffolds were seeded with hMSCs for culture in osteogenic conditions or subcutaneous implantation into nude rats. Compressive moduli increased with HA content in a near-linear fashion. The osteogenic differentiation of hMSCs increased in a dose-dependent manner as determined by alkaline phosphatase activity and osteopontin secretion after 4 weeks of culture. Further, endogenous secretion of vascular endothelial growth factor was sustained at significantly higher levels over 28 days for hMSCs seeded in 2.5:1 and 5:1 HA:PLG scaffolds. Eight weeks after implantation, scaffolds with higher HA:PLG ratios exhibited greater vascularization and more mineralized tissue. These data demonstrate that the mechanical properties, osteogenic differentiation, as well as the timing and duration of trophic factor secretion by hMSCs can be tailored through controlling the composition of the polymer–bioceramic composite. PMID:19642853

He, Jiawei; Genetos, Damian C.

2010-01-01

44

Microradiographic microsphere manipulator  

DOEpatents

A method and apparatus for radiographic characterization of small hollow spherical members (microspheres), constructed of either optically transparent or opaque materials. The apparatus involves a microsphere manipulator which holds a batch of microspheres between two parallel thin plastic films for contact microradiographic characterization or projection microradiography thereof. One plastic film is translated to relative to and parallel to the other to roll the microspheres through any desired angle to allow different views of the microspheres.

Singleton, Russell M. (Livermore, CA)

1980-01-01

45

Hybrid microspheres  

NASA Technical Reports Server (NTRS)

Substrates, particularly inert synthetic organic resin beads (10) or sheet (12) such as polystyrene are coated with a covalently bound layer (24) of polyacrolein by irradiation a solution (14) of acrolein or other aldehyde with high intensity radiation. Individual microspheres (22) are formed which attach to the surface to form the aldehyde containing layer (24). The aldehyde groups can be converted to other functional groups by reaction with materials such as hydroxylamine. Adducts of proteins such as antibodies or enzymes can be formed by direct reaction with the surface aldehyde groups.

Rembaum, Alan (Inventor); Yen, Richard C. K. (Inventor)

1985-01-01

46

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

Microsoft Academic Search

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

Hae-Won Kim; Jonathan C. Knowles; Vehid Salih; Hyoun-Ee Kim

2004-01-01

47

Development of biomimetic nano-hydroxyapatite\\/poly(hexamethylene adipamide) composites  

Microsoft Academic Search

In this study, acicular nano-hydroxyapatite (n-HA) was used to make a new biomimetic composite with polyamide (poly hexamethylene adipamide) by a unique technique. The physical and chemical characteristics of the composites were tested. It was found that these synthesized n-HA crystals were similar to bone apatite in size, phase composition and crystal structure. The biomimetic n-HA crystals were uniformly distributed

Xuejiang Wang; Yubao Li; Jie Wei; Klass de Groot

2002-01-01

48

Synthesis of Calcium HydroxyapatiteTricalcium Phosphate (HATCP) Composite Bioceramic Powders and Their Sintering Behavior  

E-print Network

Synthesis of Calcium Hydroxyapatite­Tricalcium Phosphate (HA­TCP) Composite Bioceramic Powders 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

Tas, A. Cuneyt

49

A prospective randomized study comparing electrochemically deposited hydroxyapatite and plasma-sprayed hydroxyapatite on titanium stems  

PubMed Central

Background and purpose Plasma-sprayed hydroxyapatite (HA) is a successful coating for fixation of uncemented femoral stems. There may be alternative coatings with advantages in bone remodeling and transport of bone-active substances. We investigated whether an electrochemically deposited hydroxyapatite, Bonemaster (BM), might be a safe alternative in total hip arthroplasty. Our hypothesis was that the new coating would not be inferior to the conventional one. Patients and methods 50 patients (55 hips) were included. The stem was tapered and porous-coated proximally. On top of the porous coating was either HA or BM. Patients were evaluated postoperatively and after 3, 6, 12, and 24 months to measure fixation by radiostereometric analysis (RSA), bone mineral density by dual-energy X-ray absorptiometry (DXA), and conventional radiography. Clinical evaluation was performed with Harris hip score and Oxford hip score, both preoperatively and after 2 years. Results After 2 years, the stems had subsided 0.25 (HA) and 0.28 (BM) mm and there were no statistically significant differences between the groups in any direction, regarding both migration and rotation. The BM group retained significantly more bone than the HA group in Gruen zone 1 during the first 2 years. The Harris and Oxford hip scores were similar in both groups. Interpretation Electrochemically deposited hydroxyapatite on an uncemented stem does not appear to be inferior to plasma-sprayed HA regarding clinical and radiological results, bone remodeling, and micromotion after 2 years follow-up. PMID:21189109

2011-01-01

50

Effects of adding resorbable chitosan microspheres to calcium phosphate cements for bone regeneration.  

PubMed

Calcium phosphate cements (CPCs) have been widely used as bone graft substitutes. However, the undesirable osteoinductivity and slow degradability of CPCs greatly hamper their clinical application. The aim of this study was to synthesize a type of injectable, bioactive cement. This was accomplished by incorporating chitosan microspheres into CPC. CPC containing chitosan microspheres was analyzed by X-ray diffraction (XRD) and scanning electron microscope (SEM). XRD showed that the hardened chitosan microsphere/CPC with different proportions of microspheres contained diffraction peaks of hydroxyapatite and chitosan. Compressive strength and dissolution in simulated body fluid were measured. The chitosan microsphere/CPC containing 10% (w/w) chitosan microspheres had a compressive strength of 14.78 ± 0.67 MPa. Cavity defects were created in both femoral condylar regions of New Zealand White rabbits. Chitosan microsphere/CPC (composite group) and ?-TCP/CPC (control group) were implanted separately into the bone defects of both femurs. X-ray analysis was performed to observe the filling of these bone defects 3 days after surgery. The extent of bone substitute degradation and new bone formation were evaluated by SEM and histological examination at 8, 16, and 24 weeks after implantation. These results showed far more new bone formation and degradation of the chitosan microsphere/CPC composite in the bone defects. These data indicate that a chitosan microsphere/CPC composite might be considered as a promising injectable material for the generation of new bone tissue. PMID:25492197

Meng, Dan; Dong, Limin; Wen, Ying; Xie, Qiufei

2015-02-01

51

Development of model hydroxyapatite bone scaffolds with multiscale porosity for potential load bearing applications  

NASA Astrophysics Data System (ADS)

Model hydroxyapatite (HA) bone scaffolds consisting of a latticed pattern of rods were fabricated by a solid freeform fabrication (SFF) technique based on the robotic deposition of colloidal pastes. An optimal HA paste formulation for this method was developed. Local porosity, i.e. microporosity (1--30 mum) and sintering porosity (less than 1 mum), were produced by including polymer microsphere porogens in the HA pastes and by controlling the sintering of the scaffolds. Scaffolds with and without local porosity were evaluated with and without in vitro accelerated degradation. Percent weight loss of the scaffolds and calcium and phosphorus concentrations in solution increased with degradation time. After degradation, compressive strength and modulus decreased significantly for scaffolds with local porosity, but did not change significantly for scaffolds without local porosity. The compressive strength and modulus of scaffolds without local porosity were comparable to human cortical bone and were significantly greater than the scaffolds with local porosity. Micropores in HA disks caused surface pits that increased the surface roughness as compared to non-microporous HA disks. Mouse mesenchymal stem cells extended their cell processes into these microporous pits on HA disks in vitro. ALP expression was prolonged, cell attachment strength increased, and ECM production appeared greater on microporous HA disks compared to non-microporous HA disks and tissue culture treated polystyrene controls. Scaffolds with and without microporosity were implanted in goats bones. Microporous scaffolds with rhBMP-2 increased the percent of the scaffold filled with bone tissue compared to microporous scaffolds without rhBMP-2. Lamellar bone inside scaffolds was aligned near the rods junctions whereas lamellar bone was aligned in a more random configuration away from the rod junctions. Microporous scaffolds stained darkly with toluidine blue beneath areas of contact with new bone. This staining might indicate either extracellular matrix (ECM) in the rods or dye bound to the degrading scaffold. Although the presence of microporous topography alone did not influence bone healing in vivo, micropores were shown to provide tailorability of scaffold mechanical properties, provide a location for the storage and controlled release of a growth factor, and provide a location for bone integration inside the scaffold rods.

Dellinger, Jennifer Gwynne

2005-11-01

52

microsphere assemblies  

NASA Astrophysics Data System (ADS)

The effect of Fe ion concentration on the morphological, structural, and optical properties of TiO2 films supported on silica (SiO2) opals has been studied. TiO2:Fe2O3 films were prepared by the sol-gel method in combination with a vertical dip coating procedure; precursor solutions of Ti and Fe were deposited on a monolayer of SiO2 opals previously deposited on a glass substrate by the same procedure. After the dip coating process has been carried out, the samples were thermally treated to obtain the TiO2:Fe2O3/SiO2 composites at the Fe ion concentrations of 1, 3, and 5 wt%. Scanning electron microscopy (SEM) micrographs show the formation of colloidal silica microspheres of about 50 nm diameter autoensembled in a hexagonal close-packed fashion. Although the X-ray diffractograms show no significant effect of Fe ion concentration on the crystal structure of TiO2, the ?-Raman and reflectance spectra do show that the intensity of a phonon vibration mode and the energy bandgap of TiO2 decrease as the Fe+3 ion concentration increases.

Peña-Flores, Jesús I.; Palomec-Garfias, Abraham F.; Márquez-Beltrán, César; Sánchez-Mora, Enrique; Gómez-Barojas, Estela; Pérez-Rodríguez, Felipe

2014-09-01

53

Nanocrystalline Hydroxyapatite/Si Coating by Mechanical Alloying Technique  

PubMed Central

A novel approach for depositing hydroxyapatite (HA) films on titanium substrates by using mechanical alloying (MA) technique has been developed. However, it was shown that one-hour heat treatment at 800°C of such mechanically coated HA layer leads to partial transformation of desired HA phase to beta-tri-calcium phosphate (?-TCP) phase. It appears that the grain boundary and interface defects formed during MA promote this transformation. It was discovered that doping HA by silicon results in hindering this phase transformation process. The Si-doped HA does not show phase transition to ?-TCP or decomposition after heat treatment even at 900°C. PMID:22312324

Hannora, Ahmed E.; Mukasyan, Alexander S.; Mansurov, Zulkhair A.

2012-01-01

54

In situ deposition of hydroxyapatite on graphene nanosheets  

SciTech Connect

Graphical abstract: A facile chemical precipitation method is reported for effective in situ deposition of hydroxyapatite on graphene nanosheets. Prior to grafting of hydroxyapatite, chemically modified graphene nanosheets were obtained by the reduction of graphene oxide in presence of ethylenediamine. Display Omitted Highlights: ? It is a facile and effective method for deposition of HA on GR nanosheets. ? It avoids the use of harmful reducing agents like hydrazine, NaBH{sub 4} etc. ? GR nanosheets were produced using bio-compatible, ethylenediamine. ? The graphitic structure of synthesized GR nanosheets was high ordered. ? The ratio of Ca to P in HA was 1.64, which is close to ratio in natural bone. -- Abstract: Graphene nanosheets were effectively functionalized by in situ deposition of hydroxyapatite through a facile chemical precipitation method. Prior to grafting of hydroxyapatite, chemically modified graphene nanosheets were obtained by the reduction of graphene oxide in presence of ethylenediamine. The resulting hydroxyapatite functionalized graphene nanosheets were characterized by attenuated total reflection IR spectroscopy, X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, X-ray energy dispersive spectroscopy, Raman spectroscopy and thermogravimetric analysis. These characterization techniques revealed the successful grafting of hydroxyapatite over well exfoliated graphene nanosheets without destroying their structure.

Neelgund, Gururaj M. [Department of Chemistry, Prairie View A and M University, Prairie View, TX 77446 (United States)] [Department of Chemistry, Prairie View A and M University, Prairie View, TX 77446 (United States); Oki, Aderemi, E-mail: aroki@pvamu.edu [Department of Chemistry, Prairie View A and M University, Prairie View, TX 77446 (United States)] [Department of Chemistry, Prairie View A and M University, Prairie View, TX 77446 (United States); Luo, Zhiping [Microscopy and Imaging Center and Materials Science and Engineering Program, Texas A and M University, College Station, TX 77843 (United States)] [Microscopy and Imaging Center and Materials Science and Engineering Program, Texas A and M University, College Station, TX 77843 (United States)

2013-02-15

55

Survival of hydroxyapatite-coated implants: A meta-analytic review  

Microsoft Academic Search

Purpose: Some reports show a benefit of coating dental implants with hydroxyapatite (HA), and others assert that resorption of the HA coating compromises long-term implant survival. This study examined this controversy by systematically reviewing all the current literature that reports the outcomes of HA-coated implants in human clinical trials. Materials and Methods: A systematic Medline computer search of the English

Jessica J Lee; Leyla Rouhfar; O. Ross Beirne

2000-01-01

56

Preparation of hydroxyapatite-granule- implanted titanium alloy composites with a cylindrical shape  

Microsoft Academic Search

For uniformly implanting hydroxyapatite (HA) granules into curved surfaces of titanium alloy implants such as dental roots, a new superplastic forming system was developed. By fixing PVA films with HA granules on a die's curved inner surface, HA granules are uniformly scattered and hold on the surface. The pressing system has a couple of wedges that enable press load to

A. Watazu; A. Kamiya; J. Zhu; W. Shi; K. Naganuma; T. Sonoda; K. Ushiki; T. Nonami

2002-01-01

57

Hydroxyapatite porous scaffold engineered with biological polymer hybrid coating for antibiotic Vancomycin release  

Microsoft Academic Search

The purpose of this study is to improve hydroxyapatite (HA) porous scaffolds via coating with biological polymer-HA hybrids for use as wound healing and tissue regeneration. Highly porous HA scaffolds, fabricated by a polyurethane foam reticulate method, were coated with hybrid coating solution, consisting of poly(e-caprolactone) (PCL), HA powders, and the antibiotic Vancomycin. The PCL to HA ratio was fixed

Hae-Won Kim; Jonathan C. Knowles; Hyoun-Ee Kim

2005-01-01

58

Cement from magnesium substituted hydroxyapatite.  

PubMed

Brushite cement may be used as a bone graft material and is more soluble than apatite in physiological conditions. Consequently it is considerably more resorbable in vivo than apatite forming cements. Brushite cement formation has previously been reported by our group following the mixture of nanocrystalline hydroxyapatite and phosphoric acid. In this study, brushite cement was formed from the reaction of nanocrystalline magnesium-substituted hydroxyapatite with phosphoric acid in an attempt to produce a magnesium substituted brushite cement. The presence of magnesium was shown to have a strong effect on cement composition and strength. Additionally the presence of magnesium in brushite cement was found to reduce the extent of brushite hydrolysis resulting in the formation of HA. By incorporating magnesium ions in the apatite reactant structure the concentration of magnesium ions in the liquid phase of the cement was controlled by the dissolution rate of the apatite. This approach may be used to supply other ions to cement systems during setting as a means to manipulate the clinical performance and characteristics of brushite cements. PMID:15875256

Lilley, K J; Gbureck, U; Knowles, J C; Farrar, D F; Barralet, J E

2005-05-01

59

Removal of Uranium in Drinking Water: Brimac Environmental Services, Inc. Brimac HA 216 Adsorptive Media  

EPA Science Inventory

The Brimac HA 216 Adsorptive Media was tested for uranium (U) removal from a drinking water source (well water) at Grappone Toyota located in Bow, New Hampshire. The HA 216 media is a hydroxyapatite-based material. A pilot unit, consisting of a TIGG Corporation Cansorb® C-5 ste...

60

Porous hydroxyapatite-gelatin composites with functions of bone substitutes and drug releasing agents: A preliminary study  

NASA Astrophysics Data System (ADS)

Biomedical composites made of porous hydroxyapatite (HA) bonded with a biodegradable polymeric matrix gelatin have been prepared. This device is expected to be useful as an excellent bone graft with bioactive hydroxyapatite which will facilitate new bone formation and at the same time it could functions as drug delivery with a controlled release rate. In this preliminary report, we wish to present preparation and physical characterization of the biomedical composite and the non-biodegradable porous hydroxyapatite composing the matrix of the composite. Porous hydroxyapatite was prepared via polymeric sponge method using hydroxyapatite nanopowders which were prepared via sol-gel procedure. Suspensions of the sol-gel derived hydroxyapatite powder was prepared with an adjusted loading of hydroxyapatite, using a dispersant. After soaking cellulosic sponges into the suspension, the sponges were dried and then subjected to heat-treatment at 600°C, followed by sintering at 1250°C for 1h. Three types of porous hydroxyapatite samples have been prepared in various composition of hydroxyapatite suspension. Porous hydroxyapatite bodies produced from slurry with less hydroxyapatite powder content and more dispersant amount yielded higher porosity and thus causing weaker compressive strength. Compressive strengths varied between 0.67 and 1.94 MPa depending on the porosity of the sample. Porosity plays important role in gelatin loading; the amount of gelatin coated on the porous hydroxyapatite bodies depend on porosity and the gelatin concentration in water solution. The higher porosity the more gelatin can be absorbed by the porous body.

Sopyan, I.; Sulaiman, N. S.; Gustiono, D.; Herdianto, N.

2006-01-01

61

Biodegradable magnesium-hydroxyapatite metal matrix composites.  

PubMed

Recent studies indicate that there is a high demand to design magnesium alloys with adjustable corrosion rates and suitable mechanical properties. An approach to this challenge might be the application of metal matrix composite (MMC) based on magnesium alloys. In this study, a MMC made of magnesium alloy AZ91D as a matrix and hydroxyapatite (HA) particles as reinforcements have been investigated in vitro for mechanical, corrosive and cytocompatible properties. The mechanical properties of the MMC-HA were adjustable by the choice of HA particle size and distribution. Corrosion tests revealed that HA particles stabilised the corrosion rate and exhibited more uniform corrosion attack in artificial sea water and cell solutions. The phase identification showed that all samples contained hcp-Mg, Mg(17)Al(12), and HA before and after immersion. After immersion in artificial sea water CaCO3 was found on MMC-HA surfaces, while no formation of CaCO3 was found after immersion in cell solutions with and without proteins. Co-cultivation of MMC-HA with human bone derived cells (HBDC), cells of an osteoblasts lineage (MG-63) and cells of a macrophage lineage (RAW264.7) revealed that RAW264.7, MG-63 and HBDC adhere, proliferate and survive on the corroding surfaces of MMC-HA. In summary, biodegradable MMC-HA are cytocompatible biomaterials with adjustable mechanical and corrosive properties. PMID:17276507

Witte, Frank; Feyerabend, Frank; Maier, Petra; Fischer, Jens; Störmer, Michael; Blawert, Carsten; Dietzel, Wolfgang; Hort, Norbert

2007-04-01

62

Hydroxyapatite nanoparticles: electrospinning and calcination of hydroxyapatite/polyvinyl butyral nanofibers and growth kinetics.  

PubMed

Electrospinning of hydroxyapatite (HA)/polyvinyl butyral solution resulted in the formation of fibers with average diameter of 937-1440 nm. These fibers were converted into HA nanoparticles with size <100 nm after undergoing calcination treatment at 600°C. The diameter of the fiber was found to be influenced by applied voltage and spinning distance. The injection flowrate did not affect the diameter significantly. The electrospinning method successfully reduced the commercial HA particle size in the range of 400-1100 nm into <100 nm. The dispersion of the finally calcined HA nanoparticles was improved significantly after anionic sodium dodecyl sulfate surfactant was introduced. The experimental data of HA growth kinetics were subjected to the integral method of analysis, and the rate law of the reaction was found to follow the first order reaction. PMID:23225849

Zakaria, Siti Maisurah; Sharif Zein, Sharif Hussein; Othman, Mohd Roslee; Jansen, John A

2013-07-01

63

Hydroxyapatite-anatase-carbon nanotube nanocomposite coatings fabricated by electrophoretic codeposition for biomedical applications  

Microsoft Academic Search

In order to eliminate micro-cracks in the monolithic hydroxyapatite (HA) and composite hydroxyapatite\\/carbon nanotube (HA\\/CNT)\\u000a coatings, novel HA\\/TiO2\\/CNT nanocomposite coatings on Ti6Al4V were attempted to fabricate by a single-step electrophoretic codeposition process for\\u000a biomedical applications. The electrophoretically deposited layers with difference contents of HA, TiO2 (anatase) and CNT nanoparticles were sintered at 800°C for densification with thickness of about 7–10 ?m.

Bokai Zhang; Chi Tat Kwok

64

Failure of dual radius hydroxyapatite-coated acetabular cups  

Microsoft Academic Search

INTRODUCTION: Many kind of hydroxyapatite-coated cups were used, with favorable results in short term studies; it was supposed that its use could improve osteointegration of the cup, enhancing thus stability and survivorship. The purpose of this study is to analyze the long term behavior of the hemispheric HA coated, Dual Radius Osteonics cup and to discuss the way of failure

Fabio D'Angelo; Mauro Molina; Giacomo Riva; Giovanni Zatti; Paolo Cherubino

2008-01-01

65

In situ TEM examinations of octacalcium phosphate to hydroxyapatite transformation  

NASA Astrophysics Data System (ADS)

The transformation of octacalcium phosphate (OCP) to hydroxyapatite (HA) was induced by electron beam irradiation in transmission electron microscopy (TEM). The transformation process and crystal structure changes were examined via bright-field images, electron diffraction, high-resolution transmission electron microscopy (HRTEM) and the fast Fourier transformation pattern of HRTEM images. The results indicate a mechanism of solid-state transformation occurring in the OCP crystals. The TEM examinations and crystal structure analysis also indicate the crystallographic orientation of OCP (0 1 0)//HA (0 1¯ 0) and OCP (0 0 1)//HA (0 0 1¯), which differs from the previously proposed orientation of HA growth on an OCP apatite layer.

Xin, Renlong; Leng, Yang; Wang, Ning

2006-03-01

66

Micro- and nano-hydroxyapatite as active reinforcement for soft biocomposites.  

PubMed

Pectin-based biocomposite hydrogels were produced by internal gelation, using different hydroxyapatite (HA) powders from commercial source or synthesized by the wet chemical method. HA possesses the double functionality of cross-linking agent and inorganic reinforcement. The mineralogical composition, grain size, specific surface area and microstructure of the hydroxyapatite powders are shown to strongly influence the properties of the biocomposites. Specifically, the grain size and specific surface area of the HA powders are strictly correlated to the gelling time and rheological properties of the hydrogels at room temperature. Pectin pH is also significant for the formation of ionic cross-links and therefore for the hydrogels stability at higher temperatures. The obtained results point out that micrometric-size hydroxyapatite can be proposed for applications which require rapid gelling kinetics and improved mechanical properties; conversely the nanometric hydroxyapatite synthesized in the present work seems the best choice to obtain homogeneous hydrogels with more easily controlled gelling kinetics. PMID:25109458

Munarin, F; Petrini, P; Gentilini, R; Pillai, R S; Dirè, S; Tanzi, M C; Sglavo, V M

2015-01-01

67

Growth of one-dimensional single-crystalline hydroxyapatite nanorods  

NASA Astrophysics Data System (ADS)

A facile, effective and template/surfactant-free hydrothermal route in the presence of sodium bicarbonate was developed to synthesize highly uniform single-crystalline hydroxyapatite (HA) nanorods with the lengths of several hundred nanometers and aspect ratio up to ˜20. One dimensional (1-D) growth and aspect ratio could be controlled by hydrothermal reaction time and temperature. The longitudinal axis, also the growth direction of the nanorods, is parallel to the [001] direction of HA hexagonal crystal structure.

Ren, Fuzeng; Ding, Yonghui; Ge, Xiang; Lu, Xiong; Wang, Kefeng; Leng, Yang

2012-06-01

68

In-situ dispersed photopolymerization of cyclic acetals/hydroxyapatite composites: Effects of the content of hydroxyapatite.  

PubMed

In this work, hydroxyapatite (HA) was first dispersed into cyclic acetal unit based monomers (EHD), and then EHD/HA composites were obtained by in-situ photopolymerization. FTIR and XRD analyses were used to successfully confirm the chemical composition of this composite. Real-time FTIR revealed that there was no significant effect on the photopolymerization process until the HA content was up to 30%. Several samples of such a composite with different loading amounts of HA were prepared to study effects of HA concentrations on the EHD/HA composite in particular in terms of SEM, TG, DMA, water contact angel and in-vitro biocompatibility. The results appeared that the loading of HA could significantly improve the thermal stability, mechanical properties and in vitro biocompatibility of the EHD/HA composite compared with EHD networks. PMID:25491983

Yin, Ruixue; Wu, Wentao; Wang, Kemin; Zhang, Wen Jun

2015-01-01

69

The thermal spray processing of HA powders and coatings  

NASA Astrophysics Data System (ADS)

In recent years, coated implants have been actively researched and put to use in many biomedical engineering applications. The coating used on the implants is hydroxyapatite (HA), a calcium-phosphate compound with attractive bioactive and biocompatible properties that can enhance the fixation process of biomedical implants. Thermal spraying provides a potent means for depositing the HA coatings on implants. Among the populat thermal-spray techniques are combustion-flame spray, plasma spray, and high-velocity oxy-fuel spray. This article investigates the versatility of thermal-spray techniques to perform spheroidization of HA powders, the preparation of HA-based biocomposite powders and coatings, and the deposition of HA coatings.

Khor, K. A.; Cheang, P.; Wang, Y.

1997-02-01

70

Suspension thermal spraying of hydroxyapatite: microstructure and in vitro behaviour.  

PubMed

In cementless fixation of metallic prostheses, bony ingrowth onto the implant surface is often promoted by osteoconductive plasma-sprayed hydroxyapatite coatings. The present work explores the use of the innovative High Velocity Suspension Flame Spraying (HVSFS) process to coat Ti substrates with thin homogeneous hydroxyapatite coatings. The HVSFS hydroxyapatite coatings studied were dense, 27-37?m thick, with some transverse microcracks. Lamellae were sintered together and nearly unidentifiable, unlike conventional plasma-sprayed hydroxyapatite. Crystallinities of 10%-70% were obtained, depending on the deposition parameters and the use of a TiO2 bond coat. The average hardness of layers with low (<24%) and high (70%) crystallinity was ?3.5GPa and ?4.5GPa respectively. The distributions of hardness values, all characterised by Weibull modulus in the 5-7 range, were narrower than that of conventional plasma-sprayed hydroxyapatite, with a Weibull modulus of ?3.3. During soaking in simulated body fluid, glassy coatings were progressively resorbed and replaced by a new, precipitated hydroxyapatite layer, whereas coatings with 70% crystallinity were stable up to 14days of immersion. The interpretation of the precipitation behaviour was also assisted by surface charge assessments, performed through Z-potential measurements. During in vitro tests, HA coatings showed no cytotoxicity towards the SAOS-2 osteoblast cell line, and surface cell proliferation was comparable with proliferation on reference polystyrene culture plates. PMID:24268261

Bolelli, Giovanni; Bellucci, Devis; Cannillo, Valeria; Lusvarghi, Luca; Sola, Antonella; Stiegler, Nico; Müller, Philipp; Killinger, Andreas; Gadow, Rainer; Altomare, Lina; De Nardo, Luigi

2014-01-01

71

Development of hydroxyapatite bone scaffold for controlled drug release via poly(?-caprolactone) and hydroxyapatite hybrid coatings  

Microsoft Academic Search

A scaffold-coating design, the hydroxyapatite (HA) porous bone scaffold coated with poly(-)caprolactone (PCL) and HA powder hybrids, was developed for use as tissue- regeneration and controlled-release system. An antibiotic drug, tetracycline hydrochloride (TCH), was encapsulated within the hybrid coating layer through a dip-coating and solvent- casting method. Coating cycle and drug loading amount differed to control the level of drug-release

Hae-Won Kim; Jonathan C. Knowles; Hyoun-Ee Kim

2004-01-01

72

Controlled, sustained release of proteins via an injectable, mineral-coated microsphere delivery vehicle  

NASA Astrophysics Data System (ADS)

Hydroxyapatite interfaces have demonstrated strong protein binding and protein selection from a passing solution and can serve as a biocompatible carrier for controlled protein delivery. Hydroxyapatite is a major component of long bones and tooth enamel and is the most stable of all calcium phosphate isoforms in aqueous solutions at physiologic pH, providing a sensitive chromatographic mechanism for separating proteins. Here we describe an approach to create a synthetic hydroxyapatite coating through a biomimetic, heterogeneous nucleation from a modified simulated body fluid--supersaturated with calcium and phosphate ions on the surface of injectable polymer microspheres. We are able to bind and release bioactive growth factors into a variety of in vitro and in vivo conditions, demonstrating the functionality and advantage of the biomaterial. Creating a hydroxyapatite layer on the Poly(D,L-lactide-co-glycolide) (PLG) microsphere surface, avails the microsphere interior for another application that will not compete with protein binding and release. Encapsulating an imaging agent within the aqueous phase of the emulsion provides a visual reference for the injectable therapy upon microsphere fabrication. Another advantage of this system is that the mineral coating and subsequent protein binding is not compromised by the encapsulated imaging agent. This dual function delivery vehicle is not only advantageous for spatial tracking therapeutic applications, but also determining the longevity of the delivery vehicle once injected. In the broader sense, providing a mechanism to image and track our temporally controlled, sustained delivery system gives more evidence to support the effects of released protein on in vivo responses (bioactivity) and locate microspheres within different biological systems.

Franklin-Ford, Travelle

73

Making Polymeric Microspheres  

NASA Technical Reports Server (NTRS)

Combination of advanced techniques yields uniform particles for biomedical applications. Process combines ink-jet and irradiation/freeze-polymerization techniques to make polymeric microspheres of uniform size in diameters from 100 to 400 micrometer. Microspheres used in chromatography, cell sorting, cell labeling, and manufacture of pharmaceutical materials.

Rhim, Won-Kyu; Hyson, Michael T.; Chung, Sang-Kun; Colvin, Michael S.; Chang, Manchium

1989-01-01

74

Production of hollow aerogel microspheres  

DOEpatents

A method is described for making hollow aerogel microspheres of 800-1200 .mu. diameter and 100-300 .mu. wall thickness by forming hollow alcogel microspheres during the sol/gel process in a catalytic atmosphere and capturing them on a foam surface containing catalyst. Supercritical drying of the formed hollow alcogel microspheres yields hollow aerogel microspheres which are suitable for ICF targets.

Upadhye, Ravindra S. (Pleasanton, CA); Henning, Sten A. (Dalby, SE)

1993-01-01

75

Using HaXe  

Microsoft Academic Search

haXe is a high-level programming language for web development. It can be compiled into .js files for JavaScript developers\\u000a or into .swf files for Flash, and it also supports the Neko virtual machine. Before going into the details of haXe, I’ll explain\\u000a how it came to be and how it is related to the evolution of Flash, ActionScript, and some

Nicolas Cannasse

76

Metabolism of proteinoid microspheres  

NASA Technical Reports Server (NTRS)

The literature of metabolism in proteinoids and proteinoid microspheres is reviewed and criticized from a biochemical and experimental point of view. Closely related literature is also reviewed in order to understand the function of proteinoids and proteinoid microspheres. Proteinoids or proteinoid microspheres have many activities. Esterolysis, decarboxylation, amination, deamination, and oxidoreduction are catabolic enzyme activities. The formation of ATP, peptides or oligonucleotides is synthetic enzyme activities. Additional activities are hormonal and inhibitory. Selective formation of peptides is an activity of nucleoproteinoid microspheres; these are a model for ribosomes. Mechanisms of peptide and oligonucleotide syntheses from amino acids and nucleotide triphosphate by proteinoid microspheres are tentatively proposed as an integrative consequence of reviewing the literature.

Nakashima, T.; Fox, S. W. (Principal Investigator)

1987-01-01

77

Metabolism of proteinoid microspheres  

NASA Technical Reports Server (NTRS)

The literature of metabolism in proteinoids and proteinoid microspheres is reviewed and criticized from a biochemical and experimental point of view. Closely related literature is also reviewed in order to understand the function of proteinoids and proteinoid microspheres. Proteinoids or proteinoid microspheres have many activities. Esterolyis, decarboxylation, amination, deamination, and oxidoreduction are catabolic enzyme activities. The formation of ATP, peptides or oligonucleotides is synthetic enzyme activities. Additional activities are hormonal and inhibitory. Selective formation of peptides is an activity of nucleoproteinoid microspheres; these are a model for ribosomes. Mechanisms of peptide and oligonucleotide syntheses from amino acids and nucleotide triphosphate by proteinoid microspheres are tentatively proposed as an integrative consequence of reviewing the literature.

Nakashima, T.; Fox, S. W. (Principal Investigator)

1987-01-01

78

The Effect of Zirconia in Hydroxyapatite on Staphylococcus epidermidis Growth  

PubMed Central

Synthetic hydroxyapatite (HA) has been widely used and developed as the material for bone substitute in medical applications. The addition of zirconia is needed to improve the strength of hydroxyapatite as the bone substitute. One of the drawbacks in the use of biomedical materials is the occurrence of biomaterial-centred infections. The recent method of limiting the presence of microorganism on biomaterials is by providing biomaterial-bound metal-containing compositions. In this case, S. epidermidis is the most common infectious organism in biomedical-centred infection. Objective. This study was designed to evaluate the effect of zirconia concentrations in hydroxyapatite on the growth of S. epidermidis. Methods and Materials. The subjects of this study were twenty hydroxyapatite discs, divided into four groups in which one was the control and the other three were the treatment groups. Zirconia powder with the concentrations of 20%, 30%, and 40% was added into the three different treatment groups. Scanning electron microscope analysis was performed according to the hydroxyapatite and hydroxyapatite-zirconia specimens. All discs were immersed into S. epidermidis culture for 24 hours and later on they were soaked into a medium of PBS. The cultured medium was spread on mannitol salt agar. After incubation for 24 hours at 37°C , the number of colonies was measured with colony counter. Data obtained were analyzed using the ANOVA followed by the pairwise comparison. Result. The statistical analysis showed that different concentrations of zirconia powder significantly influenced the number of S. epidermidis colony (P < 0.05) . Conclusion. The addition of zirconia into hydroxyapatite affected the growth of S. epidermidis. Hydroxyapatite with 20% zirconia proved to be an effective concentration to inhibit the growth of S. epidermidis colony. PMID:22919390

Siswomihardjo, Widowati; Sunarintyas, Siti; Tontowi, Alva Edy

2012-01-01

79

Formation of a bone apatite-like layer on the surface of porous hydroxyapatite ceramics.  

PubMed

Phosphoric acid solution was used to react with commercial hydroxyapatite (HA) powders to demonstrate the possibility of converting HA to non-stoichiometric apatite and thus to treat porous HA ceramics, to form a thin bone-apatite like layer on the HA ceramic surface. Such a carbonate-containing non-stoichiometric apatite "bioceramic" would be more efficient in bone bonding or bone formation, due to its analogy to natural bone apatite. PMID:7986949

Yubao, L; Klein, C P; Zhang, X; de Groot, K

1994-08-01

80

Hydroxyapatite particles as drug carriers for proteins.  

PubMed

Recently, much attention has been paid to hydroxyapatite (HA) particles as protein drug carriers. HA is biological substance like tooth and bone, and HA has biodegradable and biocompatible property. Also HA has high affinity for versatile substances, such as proteins. The aim of this study was to prepare HA particles and to evaluate the effects of various experimental conditions on particles properties (i.e. shape and amount of protein adsorption to HA). HA particles were prepared by three methods including solvent diffusion methods, the method using sintering porous HA microgranules, and homogeneous precipitation method. Complicated spiky crystals were prepared by solvent diffusion method, whereas spherical amorphous agglomerates were prepared by sintering of porous HA granules. Spherical particles were obtained by homogeneous precipitation method and were well dispersed. The spherical particles were composed of minute spiky crystals. The temperature and time duration of the producing process and the amount of additives, such as urea and EDTANa(2), strongly affected the particle shape and size. When the production process is kept under low temperature, tiny crystals were not mutually sintered and also their aggregation was not deposited. Also, inhomogeneous crystal growth occurred when the reaction time was long. Addition of enough amount of EDTANa(2) to reaction solution made the small and spherical HA particles. Bovine serum albumin (BSA) or lysozyme hydrochloride (LSZ)-adsorbed HA particles were prepared. The affinity of HA particles and release profile of proteins from the particles were evaluated. X-ray powder diffraction measurements suggested that the surface area ratio of a plane against total surface area of HA crystal became smaller by decreasing EDTANa(2) concentration. The surface of plane a is positively charged but that of plane c is negatively charged. HA particle size decreased as EDTANa(2) concentration increased. The amounts of BSA and LSZ adsorbing onto HA particle surface were different, since BSA was negatively charged and LSZ was positively charged in the solution. Therefore BSA seems to adsorb onto plane c, whereas LSZ adsorb onto plane a. The differences of the ratio of surface a plane against the total surface area of HA particles and particles size influenced the amount of protein adsorption. The sustained release of BSA and LSZ from HA particles were observed for two weeks. PMID:19939646

Tomoda, Keishiro; Ariizumi, Hidehiko; Nakaji, Takatomo; Makino, Kimiko

2010-03-01

81

Hydroxyapatite synthesis using EDTA  

PubMed Central

Bone comprises structure of body and is consisted of inorganic substances. It exists in an organic structure in the body. Even though it is firm and has self healing mechanism, it can be damaged by trauma, cancer, or bone diseases. Allograft can be an alternative solution for autologous bone graft. Hydroxyapatite(Ca10(PO4)6(OH)2), an excellent candidate for allograft, can be applied to bone defect area. There are several methods to produce hydroxyapatite, however economical cost and time consuming make the production difficult. In this study we synthesized the hydroxyapatite with Ethyenediamine tetraacetic acid. Freeze Dried Bone Allograft(Hans Biomed) was used to be a control group. Synthesized hydroxyapatite was a rod shape, white powdery type substance with 2 ~ 5 ?m length and 0.5 ~ 1 ?m width. X-ray diffraction showed the highest sharp peak at 32° and high peaks at 25.8°, 39.8°, 46.8°, 49.5°, and 64.0° indicating a similar substance to the freeze Dried Bone Allograft. 3 days after the cell growth of synthesized hydroxyapatite showed 1.5 fold more than the Bone Allograft. Cellular and media alkaline phosphate activity increased similar to the bone alloagraft. In this study we came up with a new method to produce the hydroxyapatite. It is a convenient method that can be held in room temperature and low pressure. Also the the product can be manufactured in large quantity. It can be also transformed into scaffold structure which will perform a stronger configuration. The manufacturing method will help the bony defect patients and make future medical products. PMID:23714942

Kang, Nak Heon; Kim, Soon Je; Song, Seung Han; Choi, Sang mun; Choi, Sik Young; Kim, Youn Jung

2013-01-01

82

Microsphere Insulation Panels  

NASA Technical Reports Server (NTRS)

Microsphere insulation panels (MIPs) have been developed as lightweight, longlasting replacements for the foam and vacuum-jacketed systems heretofore used for thermally insulating cryogenic vessels and transfer ducts. The microsphere core material of a typical MIP consists of hollow glass bubbles, which have a combination of advantageous mechanical, chemical, and thermal-insulation properties heretofore available only separately in different materials. In particular, a core filling of glass microspheres has high crush strength and low density, is noncombustible, and performs well in soft vacuum.

Mohling, R.; Allen, M.; Baumgartner, R.

2006-01-01

83

Biocompatibility of Laser-deposited Hydroxyapatite Coatings on Titanium and Polymer Implant Materials  

Microsoft Academic Search

We have investigated the biocompatibility of calcium phosphate coatings deposited by pulsed laser ablation from hydroxyapatite (HA) targets onto polyethylene and Teflon substrates. It was found that the cell density, attachment, and morphology of primary rat calvaria osteoblasts were influenced by both the original polymer and by the nature of the apatite coatings. HA coatings on Teflon were found to

Evgueni N. Antonov; Victor N. Bagratashvili; Vladimir K. Popov; Emil N. Sobol; Steven Howdle; Christine Joiner; Kate G. Parker; Terry L. Parker; Alexander A. Doktorov; Valeri B. Likhanov; Alexander I. Volozhin; Sergey S. Alimpiev; Sergey M. Nikiforov

1998-01-01

84

Influence of temperature, ripening time and calcination on the morphology and crystallinity of hydroxyapatite nanoparticles  

Microsoft Academic Search

Nano-sized hydroxyapatite (HA) particles were prepared by chemical precipitation through aqueous solutions of calcium chloride and ammonium hydrogenphosphate. The influence of temperature, ripening time and calcination on the crystallinity and morphology of the HA nanoparticles were investigated. It was found that the crystallinity and crystallite size increased with the increase of synthetic temperature and ripening time. XRD and TEM results

Y. X. Pang; X. Bao

2003-01-01

85

Collagen hydrolysate based collagen/hydroxyapatite composite materials  

NASA Astrophysics Data System (ADS)

The aim of this study was to study the influence of collagen hydrolysate (HAS) on the formation of ternary collagen-hydrolysate/hydroxyapatite composite materials (COLL-HAS/HA). During the precipitation process of HA, a large amount of brushite is resulted at pH = 7 but, practically pure HA is obtained at pH ? 8. The FTIR data reveal the duplication of the most important collagen absorption bands due to the presence of the collagen hydrolysate. The presence of collagen hydrolysate is beneficial for the management of bone and joint disorders such as osteoarthritis and osteoporosis.

Ficai, Anton; Albu, Madalina Georgiana; Birsan, Mihaela; Sonmez, Maria; Ficai, Denisa; Trandafir, Viorica; Andronescu, Ecaterina

2013-04-01

86

Hydroxyapatite-binding peptides for bone growth and inhibition  

DOEpatents

Hydroxyapatite (HA)-binding peptides are selected using combinatorial phage library display. Pseudo-repetitive consensus amino acid sequences possessing periodic hydroxyl side chains in every two or three amino acid sequences are obtained. These sequences resemble the (Gly-Pro-Hyp).sub.x repeat of human type I collagen, a major component of extracellular matrices of natural bone. A consistent presence of basic amino acid residues is also observed. The peptides are synthesized by the solid-phase synthetic method and then used for template-driven HA-mineralization. Microscopy reveal that the peptides template the growth of polycrystalline HA crystals .about.40 nm in size.

Bertozzi, Carolyn R. (Berkeley, CA); Song, Jie (Shrewsbury, MA); Lee, Seung-Wuk (Walnut Creek, CA)

2011-09-20

87

Effect of Thickness of HA-Coating on Microporous Silk Scaffolds Using Alternate Soaking Technology  

PubMed Central

Hydroxyapatite (HA) can be coated on various materials surface and has the function of osteogenicity. Microporous silk scaffold has excellent biocompatibility. In this study, alternate soaking technology was used to coat HA on microporous silk scaffolds. However, the cell proliferation was found to decrease with the increasing thickness (cycles of soaking) of HA-coating. This study aims to determine the best thickness (cycles of soaking) of HA-coating on microporous silk scaffolds. The SEM observation showed that group with one cycle of alternate soaking (1C-HA) has the most optimal porosity like non-HA-modified microporous silk scaffolds. The proliferation of osteoblasts has no significant difference between noncoated HA (N-HA) and 1C-HA groups, which are both significantly higher than those in two cycles of soaking (2C-HA) and three cycles of soaking (3C-HA) groups. The transcription levels of specific genes (runx2 and osteonectin) in osteoblasts of 1C-HA group were significantly higher than those of N-HA group. Moreover, the levels showed no significant difference among 1C-HA, 2C-HA, and 3C-HA groups. In conclusion, microporous silk scaffold with 1 cycle of HA-coating can combine the biocompatibility of silk and osteogenicity of HA. PMID:25093176

Zhu, Rui; Xue, Yingsen; Hao, Zhangying; Xie, Zhenghong; Fan, Xiangli; Fan, Hongbin

2014-01-01

88

Organic aerogel microspheres  

DOEpatents

Organic aerogel microspheres which can be used in capacitors, batteries, thermal insulation, adsorption/filtration media, and chromatographic packings, having diameters ranging from about 1 micron to about 3 mm. The microspheres can be pyrolyzed to form carbon aerogel microspheres. This method involves stirring the aqueous organic phase in mineral oil at elevated temperature until the dispersed organic phase polymerizes and forms nonsticky gel spheres. The size of the microspheres depends on the collision rate of the liquid droplets and the reaction rate of the monomers from which the aqueous solution is formed. The collision rate is governed by the volume ratio of the aqueous solution to the mineral oil and the shear rate, while the reaction rate is governed by the chemical formulation and the curing temperature.

Mayer, Steven T. (San Leandro, CA); Kong, Fung-Ming (Pleasanton, CA); Pekala, Richard W. (Pleasant Hill, CA); Kaschmitter, James L. (Pleasanton, CA)

1999-01-01

89

Organic aerogel microspheres  

DOEpatents

Organic aerogel microspheres are disclosed which can be used in capacitors, batteries, thermal insulation, adsorption/filtration media, and chromatographic packings, having diameters ranging from about 1 micron to about 3 mm. The microspheres can be pyrolyzed to form carbon aerogel microspheres. This method involves stirring the aqueous organic phase in mineral oil at elevated temperature until the dispersed organic phase polymerizes and forms nonstick gel spheres. The size of the microspheres depends on the collision rate of the liquid droplets and the reaction rate of the monomers from which the aqueous solution is formed. The collision rate is governed by the volume ratio of the aqueous solution to the mineral oil and the shear rate, while the reaction rate is governed by the chemical formulation and the curing temperature.

Mayer, S.T.; Kong, F.M.; Pekala, R.W.; Kaschmitter, J.L.

1999-06-01

90

Softening of hydroxyapatite by vacancies: a first principles investigation.  

PubMed

First-principles plane-wave calculations were performed to investigate the influences of intrinsic vacancy on the stability and elastic properties of hydroxyapatite (HA). Five types of vacancies, i.e. H, O, OH, Ca, and Ca(2+) vacancy, were considered. Formation energies were evaluated and compared with experimental measurements. It was shown that HA with a Ca(2+) vacancy is the most stable one among the considered systems. Elastic constants were estimated via curves of total energy against strain. Bulk, shear and Young's moduli, and Poisson's ratio are also evaluated to compare with the experimental value. The elastic properties of HA are significantly affected by the vacancy. Vacancy can soften HA via reducing its elastic moduli. The HA with Ca(2+) vacancy is the softest one among the considered systems. Electronic structures of HA with vacancy are also analyzed to explain the softening mechanisms. PMID:23827549

Sun, J P; Song, Y; Wen, G W; Wang, Y; Yang, R

2013-04-01

91

Compartmentalization in proteinoid microspheres  

NASA Technical Reports Server (NTRS)

Proteinoid microspheres with stable internal compartments and internal structure are made from acidic proteinoid and basic proteinoid with calcium. The populations of microspheres are characterized by a wide diversity of structure. A model of primitive intracellular communication is suggested by the observed movement of internal particles between compartments of a multicompartmentalized unit. Differential response to pH change and to temperature change has been demonstrated within one population and suggests one mode of adaptive selection among primordial cell populations.

Brooke, S.; Fox, S. W.

1977-01-01

92

HYDROXYAPATITE PULSED LASER DEPOSITED THIN FILMS BEHAVIOUR WHEN SUBMITTED TO BIOLOGICAL SIMULATED TESTS  

Microsoft Academic Search

Structures of hydroxyapatite (HA) as thin films, with and without buffer layers, were deposited on Commercially Pure Titanium Grade 4 (c.p. Ti gr4) substrates by Pulsed Laser Deposition. They were afterwards heat treated in water vapours. In this study, processes taking place at the hydroxyapatite\\/Hank's Solution interface are investigated. The experiment consists of immersing the films in Hank's Solution for

S. GRIGORESCU; C. RISTOSCU; G. SOCOL; E. AXENTE; F. FEUGEAS; I. N. MIHAILESCU

93

Fluor-hydroxyapatite sol–gel coating on titanium substrate for hard tissue implants  

Microsoft Academic Search

Hydroxyapatite (HA) and fluor-hydroxyapatite (FHA) films were deposited on a titanium substrate using a sol–gel technique. Different concentrations of F? were incorporated into the apatite structure during the sol preparation. Typical apatite structures were obtained for all coatings after dipping and subsequent heat treatment at 500°C. The films obtained were uniform and dense, with a thickness of ?5?m. The dissolution

Hae-Won Kim; Hyoun-Ee Kim; Jonathan C. Knowles

2004-01-01

94

Preparation and characterization of PHBV microsphere/45S5 bioactive glass composite scaffolds with vancomycin releasing function.  

PubMed

PHBV microsphere/45S5 bioactive glass (BG) composite scaffolds with drug release function were developed for bone tissue engineering. BG-based glass-ceramic scaffolds with high porosity (94%) and interconnected pore structure prepared by foam replication method were coated with PHBV microspheres (nominal diameter=3.5 ?m) produced by water-in-oil-in-water double emulsion solvent evaporation method. A homogeneous microsphere coating throughout the porous structure of scaffolds was obtained by a simple dip coating method, using the slurry of PHBV microspheres in hexane. Compressive strength tests showed that the microsphere coating slightly improved the mechanical properties of the scaffolds. It was confirmed that the microsphere coating did not inhibit the bioactivity of the scaffolds in SBF. Hydroxyapatite crystals homogeneously grew not only on the struts of the scaffolds but also on the surface of microspheres within 7 days of immersion in SBF. Vancomycin was successfully encapsulated into the PHBV microspheres. The encapsulated vancomycin was released with a dual release profile involving a relatively low initial burst release (21%) and a sustained release (1 month), which is favorable compared to the high initial burst release (77%) and short release period (4 days) measured on uncoated scaffolds. The developed bioactive composite scaffold with drug delivery function has thus the potential to be used advantageously in bone tissue engineering. PMID:24907766

Li, Wei; Ding, Yaping; Rai, Ranjana; Roether, Judith A; Schubert, Dirk W; Boccaccini, Aldo R

2014-08-01

95

Silicate-doped hydroxyapatite and its promotive effect on bone mineralization  

NASA Astrophysics Data System (ADS)

Bone defect is one of the most common diseases in clinic. Existing therapeutic approaches have encountered many problems, such as lack of autogenous allogeneic bone and immunological rejection to allogeneic implant. Synthetic hydroxyapatite (HA) provided solutions for bone repair, since the HA is the main inorganic component of animals' bone. However, HA has good biocompatibility, but does not possess osteogenic capability, which is of significance for modern bone repair materials. Si is an essential trace element in bone tissue, and it has been demonstrated to be able to promote bone formation. Therefore, silicate-doped hydroxyapatite (Si-HA) may serve as a promising material for bone repair, and promote bone regeneration in the repair. The current review discusses development of Si-HA, focusing on its preparation and characterization, in vitro and in vivo evaluations of the material, positive effect of Si-HA on promoting bone formation in clinical applications, and molecular mechanism investigation of such promotive effect.

Qiu, Zhi-Ye; Noh, In-Sup; Zhang, Sheng-Min

2013-03-01

96

Comparing Microspheres with Different Internal Phase of Polyelectrolyte as Local Drug Delivery System for Bone Tuberculosis Therapy  

PubMed Central

We use hydrophobic poly(lactic-co-glycolic) acid (PLGA) to encapsulate hydrophilic ofloxacin to form drug loading microspheres. Hyaluronic acid (HA) and polylysine (Pls) were used as internal phase additives to see their influences on the drug loading and releasing. Double emulsion (water-in-oil-in-water) solvent extraction/evaporation method was used for the purpose. Particle size analysis display that the polyelectrolytes have low impact on the microsphere average size and distribution. Scanning electron microscope (SEM) pictures show the wrinkled surface resulted by the internal microcavity of the microspheres. Microspheres with HA inside have higher drug loading amounts than microspheres with Pls inside. The loading drug amounts of the microspheres increase with the HA amounts inside, while decreasing with the Pls amounts inside. All the polyelectrolytes adding groups have burst release observed in experiments. The microspheres with Pls internal phase have faster release rate than the HA groups. Among the same polyelectrolyte internal phase groups, the release rate increases with the amounts increasing when Pls is inside, while it decreases with the amounts increasing when HA is inside. PMID:24707480

Chen, Long; Li, Hong; Deng, Chun-Ling; Chen, Xiao-Feng

2014-01-01

97

Comparing microspheres with different internal phase of polyelectrolyte as local drug delivery system for bone tuberculosis therapy.  

PubMed

We use hydrophobic poly(lactic-co-glycolic) acid (PLGA) to encapsulate hydrophilic ofloxacin to form drug loading microspheres. Hyaluronic acid (HA) and polylysine (Pls) were used as internal phase additives to see their influences on the drug loading and releasing. Double emulsion (water-in-oil-in-water) solvent extraction/evaporation method was used for the purpose. Particle size analysis display that the polyelectrolytes have low impact on the microsphere average size and distribution. Scanning electron microscope (SEM) pictures show the wrinkled surface resulted by the internal microcavity of the microspheres. Microspheres with HA inside have higher drug loading amounts than microspheres with Pls inside. The loading drug amounts of the microspheres increase with the HA amounts inside, while decreasing with the Pls amounts inside. All the polyelectrolytes adding groups have burst release observed in experiments. The microspheres with Pls internal phase have faster release rate than the HA groups. Among the same polyelectrolyte internal phase groups, the release rate increases with the amounts increasing when Pls is inside, while it decreases with the amounts increasing when HA is inside. PMID:24707480

Wu, Gang; Chen, Long; Li, Hong; Deng, Chun-Ling; Chen, Xiao-Feng

2014-01-01

98

HDPE-HA composites synthetized by in situ polymerization with different filler content  

NASA Astrophysics Data System (ADS)

In Situ ethylene polymerization was used to synthesize high density polyethylene - hydroxyapatite (HDPE-HA) composites, employing Cp2ZrCl2/MAO as catalytic system. A good dispersion of HA into the HDPE matrix was obtained when the following synthesis conditions were combined: high stirring velocities (2000 rpm), low quantities of solvent (100 mL), and 10 °C. Under these conditions different filler content was used to synthetized HDPE-HA composites. An interaction between HA and HDPE was obtained by FTIR. On the other hand, thermal analysis indicated that no significant differences were observed between HDPE and the composites.

Hermán, V.; Karam, A.; Albano, C.; Romero, K.; González, G.

2012-07-01

99

Hydroxyapatite coating on titanium substrate with titania buffer layer processed by sol–gel method  

Microsoft Academic Search

Hydroxyapatite (HA) was coated onto a titanium (Ti) substrate with the insertion of a titania (TiO2) buffer layer by the sol–gel method. The HA layer was employed to enhance the bioactivity and osteoconductivity of the Ti substrate, and the TiO2 buffer layer was inserted to improve the bonding strength between the HA layer and Ti substrate, as well as to

Hae-Won Kim; Young-Hag Koh; Long-Hao Li; Sook Lee; Hyoun-Ee Kim

2004-01-01

100

A Randomized Trial of Hydroxyapatite-Coated Femoral Stems in Total Hip Arthroplasty  

Microsoft Academic Search

A prospective randomized trial comparing hydroxyapatite (HA)-coated and non–HA-coated femoral total hip arthroplasty components was conducted. Sixty-one consecutive patients undergoing primary hip arthroplasty were randomized to receive an identical femoral component with or without HA. Forty-eight hips were available for review at an average of 13 years and 5 months after surgery. The only femoral stem revised was secondary to

Dan Camazzola; Terry Hammond; Rajiv Gandhi; J. Roderick Davey

2009-01-01

101

Preparation and in vitro bioactivity of poly( d,l-lactide) composite containing hydroxyapatite nanocrystals  

Microsoft Academic Search

The nano-sized hydroxyapatite (n-HA) was incorporated into poly(d,l-Lactide) (PDLLA) to form a bioactive and biodegradable composite for application in hard tissue replacement and regeneration. Thin film of PDLLA composite containing 20 mass% of n-HA fillers was successfully developed through integration of solvent co-blending and hot pressing techniques. firstly, n-HA and PDLLA were chemically synthesized, respectively, then mixed together and homogeneously dispersed

C. Deng; J. Weng; X. Lu; S. B. Zhou; J. X. Wan; S. X. Qu; B. Feng; X. H. Li

2008-01-01

102

Demineralized bone matrix and hydroxyapatite\\/tri-calcium phosphate mixture for bone healing in rats  

Microsoft Academic Search

Purpose: Hydroxyapatite\\/tri-calcium phosphate (HA\\/TCP) mixture is an osteoconductive material used as a bone graft substitute, and demineralised bone matrix (DBM) is an osteoinductive material. A combination of DBM and HA\\/TCP mixture would probably create a composite with both osteoconductive and osteoinductive properties. The purpose of this study was to determine the effect of the combination of DBM and HA\\/TCP mixture

Ali Öztürk; H. Yetkin; L. Memis; E. Cila; S. Bolukbasi; C. Gemalmaz

2006-01-01

103

Iron(III) and manganese(II) substituted hydroxyapatite nanoparticles: Characterization and cytotoxicity analysis  

NASA Astrophysics Data System (ADS)

Calcium hydroxyapatite (HA) is the main inorganic component of natural bones and can bond to bone directly in vivo. Thus HA is widely used as coating material on bone implants due to its good osteoconductivity and osteoinductivity. Metal ions doped HA have been used as catalyst or absorbents since the ion exchange method has introduced new properties in HA which are inherent to the metal ions. For example, Mn2+ ions have the potential to increase cell adhesion while Fe3+ ions have magnetic properties. Here, Fe(III) substituted hydroxyapatite (Fe-HA) and Mn(II) substituted hydroxyapatite (Mn-HA) were produced by wet chemical method coupled with ion exchange mechanism. Compared with pure HA, the colour of both Fe-HA and Mn-HA nanoparticles changed from white to brown and pink respectively. The intensity of the colours increased with increasing substitution concentrations. XRD patterns showed that all samples were single phased HA while the FTIR spectra revealed all samples possessed the characteristic phosphate and hydroxyl adsorption bands of HA. However, undesired adsorption bands of carbonate substitution (B-type carbonated HA) and H2O were also detected, which was reasonable since the wet chemical method was used in the synthesis of these nanoparticles. FESEM images showed all samples were elongated spheroids with small size distribution and of around 70 nm, regardless of metal ion substitution concentrations. EDX spectra showed the presence of Fe and Mn and ICP-AES results revealed all metal ion substituted HA were non-stoichiometric (Ca/P atomic ratio deviates from 1.67). Fe-HA nanoparticles were paramagnetic and the magnetic susceptibility increased with the increase of Fe content. Based on the extraction assay for cytotoxicity test, both Fe-HA and Mn-HA displayed non-cytotoxicity to osteoblast.

Li, Yan; Teck Nam, Chai; Ooi, Chui Ping

2009-09-01

104

Effects of sol–gel processing parameters on the phases and microstructures of HA films  

Microsoft Academic Search

Bioactive hydroxyapatite (HA) films were fabricated by a sol–gel method and triethylphosphate and calcium nitrate were used as the phosphorus and calcium precursors, respectively. The effects of the heat treatment temperature, pH level and substrate materials on the phases and microstructures of HA films were studied by X-ray diffraction (XRD), scanning electronic microscopy (SEM) and electronic probe microanalysis (EPMA) and

Diangang Wang; Chuanzhong Chen; Xiuna Liu; Tingquan Lei

2007-01-01

105

Hydroxyapatite grafted carbon nanotubes and graphene nanosheets: Promising bone implant materials  

NASA Astrophysics Data System (ADS)

In the present study, hydroxyapatite (HA) was successfully grafted to carboxylated carbon nanotubes (CNTs) and graphene nanosheets. The HA grafted CNTs and HA-graphene nanosheets were characterized using FT-IR, TGA, SEM and X-ray diffraction. The HA grafted CNTs and graphene nanosheets (CNTs-HA and Gr-HA) were further used to examine the proliferation and differentiation rate of temperature-sensitive human fetal osteoblastic cell line (hFOB 1.19). Total protein assays and western blot analysis of osteocalcin expression were used as indicators of cell proliferation and differentiation. Results indicated that hFOB 1.19 cells proliferate and differentiate well in treatment media containing CNTs-HA and graphene-HA. Both CNTs-HA and graphene-HA could be promising nanomaterials for use as scaffolds in bone tissue engineering.

Oyefusi, Adebola; Olanipekun, Opeyemi; Neelgund, Gururaj M.; Peterson, Deforest; Stone, Julia M.; Williams, Ebonee; Carson, Laura; Regisford, Gloria; Oki, Aderemi

2014-11-01

106

Hydroxyapatite coated with heaptocyte growth factor (HGF) stimulates human osteoblasts in vitro.  

PubMed

We have studied in vitro the effect of a hydroxyapatite (HA) tricalcium phosphate material coated with hepatocyte growth factor (HA-HGF) on cell growth, collagen synthesis and secretion of metalloproteinases (MMPs) by human osteoblasts. Cell proliferation was stimulated when osteoblasts were incubated with untreated HA and was further increased after exposure to HA-HGF. The uptake of [3H]-proline was increased after treatment with HA. When osteoblasts were exposed to HA-HGF, collagen synthesis was increased with respect to HA. The secretion of MMPs in control cells was undetectable, but in HA and HA-HGF cells MMP 2 and MMP 9 were clearly synthesised. Our results suggest that HA can promote osteoblast activity and that HGF can further increase its bioactivity. PMID:10813189

Zambonin, G; Camerino, C; Greco, G; Patella, V; Moretti, B; Grano, M

2000-04-01

107

Synthesis of sodium caseinate-calcium carbonate microspheres and their mineralization to bone-like apatite  

NASA Astrophysics Data System (ADS)

Phosphoproteins can induce and stabilize calcium carbonate (CaCO3) vaterite, which has desirable features for high reactivity. The purpose of this study was to synthesize bioactive CaCO3 microspheres for bone regeneration. Sodium caseinate (NaCas)-containing CaCO3 microspheres, with the crystal phase of vaterite, were synthesized by fast precipitation in an aqueous solution of CaCl2, Na2CO3, and 2 mg/mL of NaCas. The uniform microspheres exhibited rougher surfaces and lower negative charges than CaCO3 particles without NaCas addition. Fourier-transform infrared spectroscopy (FT-IR) of the microspheres showed characteristic peaks or bands corresponding to phosphate and hydroxyl groups. Thermogravimetric analysis (TGA) curves exhibited approximately 5% weight loss below 600 °C due to the decomposition of NaCas. Scanning electron microscope (SEM) images showed lath-like hydroxyapatite (HAp) on the surface after soaking in simulated body fluid (SBF) at 37 °C for 5 and 10 days. Energy dispersive X-ray spectrometry (EDS) revealed that the agglomerates were composed of Ca, C, O, P, Na, and Mg elements, and the Ca/P ratios ranged from 1.53 to 1.56. X-ray diffraction (XRD) patterns exhibited peaks characteristic of hydroxyapatite. The results of this study demonstrated that the addition of NaCas induced the formation of vaterite microspheres which possesses an enhanced apatite formation after soaking in SBF at 37 °C for 5 and 10 days. These NaCas-CaCO3 microspheres may be a potential biomaterial for bone regeneration.

Xu, Zhewu; Liang, Guobin; Jin, Lin; Wang, Zhenling; Xing, Chao; Jiange, Qing; Zhang, Zhiguang

2014-06-01

108

Doppler cooling a microsphere  

E-print Network

Doppler cooling the center-of-mass motion of an optically levitated microsphere via the velocity dependent scattering force from narrow whispering gallery mode (WGM) resonances is described. Light that is red detuned from the WGM resonance can be used to damp the center-of-mass motion in a process analogous to the Doppler cooling of atoms. Leakage of photons out of the microsphere when the incident field is near resonant with the narrow WGM resonance acts to damp the motion of the sphere. The scattering force is not limited by saturation, but can be controlled by the incident power. Cooling times on the order of seconds are calculated for a 20 micron diameter silica microsphere trapped within optical tweezers, with a Doppler temperature limit in the microKelvin regime.

P. F. Barker

2010-04-08

109

Doppler cooling a microsphere  

E-print Network

Doppler cooling the center-of-mass motion of an optically levitated microsphere via the velocity dependent scattering force from narrow whispering gallery mode (WGM) resonances is described. Light that is red detuned from the WGM resonance can be used to damp the center-of-mass motion in a process analogous to the Doppler cooling of atoms. Leakage of photons out of the microsphere when the incident field is near resonant with the narrow WGM resonance acts to damp the motion of the sphere. The scattering force is not limited by saturation, but can be controlled by the incident power. Cooling times on the order of seconds are calculated for a 20 micron diameter silica microsphere trapped within optical tweezers, with a Doppler temperature limit in the microKelvin regime.

Barker, P F

2010-01-01

110

Effect of Hydroxyapatite on Bone Integration in a Rabbit Tibial Defect Model  

PubMed Central

Background The aim of the present study was to prepare hydroxyapatite (HA) and then characterize its effect on bone integration in a rabbit tibial defect model. The bone formation with different designs of HA was compared and the bony integration of several graft materials was investigated qualitatively by radiologic and histologic study. Methods Ten rabbits were included in this study; two holes were drilled bilaterally across the near cortex and the four holes in each rabbit were divided into four treatment groups (HAP, hydroxyapatite powder; HAC, hydroxyapatite cylinder; HA/TCP, hydroxyapatite/tri-calcium phosphate cylinder, and titanium cylinder). The volume of bone ingrowth and the change of bone mineral density were statistically calculated by computed tomography five times for each treatment group at 0, 2, 4, 6, and 8 weeks after grafting. Histologic analysis was performed at 8 weeks after grafting. Results The HAP group showed the most pronounced effect on the bone ingrowth surface area, which seen at 4, 6, and 8 weeks after graft (p < 0.05). On comparing the change of bone mineral density the bone ingrowth surface area among the 4 groups, there were no statistically significant differences among the groups found for any period (p > 0.05). On histological examination, the HAP group revealed well-recovered cortical bone, but the bone was irregularly thickened and haphazardly admixed with powder. The HAC group showed similar histological features to those of the HA/TCP group; the cortical surface of the newly developed bone was smooth and the bone matrix on the surface of the cylinder was regularly arranged. Conclusions We concluded that both the hydroxyapatite powder and cylinder models investigated in our study may be suitable as a bone substitute in the rabbit tibial defect model, but their characteristic properties are quite different. In contrast to hydroxyapatite powder, which showed better results for the bone ingrowth surface, the hydroxyapatite cylinder showed better results for the sustained morphology. PMID:20514266

Sohn, Sung-Keun; Kim, Kyung-Taek; Kim, Chul-Hong; Ahn, Hee-Bae; Rho, Mee-Sook; Jeong, Min-Ho; Sun, Sang-Kyu

2010-01-01

111

Doppler cooling a microsphere.  

PubMed

Doppler cooling the center-of-mass motion of an optically levitated microsphere via the velocity-dependent scattering force from narrow whispering gallery mode resonances is described. Light that is red detuned from the whispering gallery mode resonance can be used to damp the center-of-mass motion in a process analogous to the Doppler cooling of atoms. The scattering force is not limited by saturation but can be controlled by the incident power. Cooling times on the order of seconds are calculated for a 20 ?m diameter silica microsphere trapped within optical tweezers. PMID:20868038

Barker, P F

2010-08-13

112

Dual functional selenium-substituted hydroxyapatite  

PubMed Central

Hydroxyapatite (HA) doped with trace elements has attracted much attention recently owing to its excellent biological functions. Herein, we use a facile co-precipitation method to incorporate selenium into HA by adding sodium selenite during synthesis. The obtained selenium-substituted HA products are needle-like nanoparticles which have  size and crystallinity that are similar to those of the pure HA nanoparticles (HANs) when the selenium content is low. HANs are found to have the ability to induce the apoptosis of osteosarcoma cells, and the anti-tumour effects are enhanced after incorporation of selenium. Meanwhile, the nanoparticles can also support the growth of bone marrow stem cells. Furthermore, the flow cytometric results indicate that the apoptosis induction of osteosarcoma cells is caused by the increased reactive oxygen species and decreased mitochondrial membrane potential. These results show that the selenium-substituted HANs are potentially promising bone graft materials in osteosarcoma treatment due to their dual functions of supporting normal cell growth and inducing tumour cell apoptosis. PMID:23741613

Wang, Yanhua; Ma, Jun; Zhou, Lei; Chen, Jin; Liu, Yonghui; Qiu, Zhiye; Zhang, Shengmin

2012-01-01

113

Dual functional selenium-substituted hydroxyapatite.  

PubMed

Hydroxyapatite (HA) doped with trace elements has attracted much attention recently owing to its excellent biological functions. Herein, we use a facile co-precipitation method to incorporate selenium into HA by adding sodium selenite during synthesis. The obtained selenium-substituted HA products are needle-like nanoparticles which have  size and crystallinity that are similar to those of the pure HA nanoparticles (HANs) when the selenium content is low. HANs are found to have the ability to induce the apoptosis of osteosarcoma cells, and the anti-tumour effects are enhanced after incorporation of selenium. Meanwhile, the nanoparticles can also support the growth of bone marrow stem cells. Furthermore, the flow cytometric results indicate that the apoptosis induction of osteosarcoma cells is caused by the increased reactive oxygen species and decreased mitochondrial membrane potential. These results show that the selenium-substituted HANs are potentially promising bone graft materials in osteosarcoma treatment due to their dual functions of supporting normal cell growth and inducing tumour cell apoptosis. PMID:23741613

Wang, Yanhua; Ma, Jun; Zhou, Lei; Chen, Jin; Liu, Yonghui; Qiu, Zhiye; Zhang, Shengmin

2012-06-01

114

Endothelial cell migration and morphogenesis on silk fibroin scaffolds containing hydroxyapatite electret.  

PubMed

The purpose of this study was to evaluate the effects of composite wound dressing films made of silk fibroin (SF) containing hydroxyapatite (HA) or polarized HA (pHA) powders on endothelial cell (EC) behaviors that have important roles in the wound-healing process. XRD revealed the SF films to be semicrystalline, with a broad peak centered at about 20.7° which is characteristic of ?-sheets embedded within an amorphous matrix. The SF composite films with 0.6 (w/v)% in concentration of HA powder (HA/SF) or pHA powder (pHA/SF) contained HA crystals of amorphous and silk II crystalline structures. SEM observation showed that there were differences in SF morphology between HA/SF and pHA/SF. The pHA/SF exhibited a furry texture around the pHA crystals, most likely due to the stored charged and zeta potentials. The HA/SF and pHA/SF films enhanced EC migration compared with that on the SF film. The number of migrated cells on the HA/SF and pHA/SF was ~1.5 times larger than that on the SF. The quantitative analysis of the endothelial morphogenesis indicated that the pHA/SF film enhanced the formation of capillary-like structures compared with SF and HA/SF. Thus, pHA/SF may potentially stimulate and contribute to the enhancement of angiogenesis in the wound-healing process. PMID:22275235

Nakamura, Miho; Soya, Tomoko; Hiratai, Rumi; Nagai, Akiko; Hashimoto, Kazuaki; Morita, Ikuo; Yamashita, Kimihiro

2012-04-01

115

In vivo study of chitosan-natural nano hydroxyapatite scaffolds for bone tissue regeneration.  

PubMed

Significant development has been achieved with bioceramics and biopolymer scaffolds in the construction of artificial bone. In the present study, we have developed and compared chitosan-micro hydroxyapatite (chitosan-mHA) and chitosan-nano hydroxyapatite (chitosan-nHA) scaffolds as bone graft substitutes. The biocompatibility and cell proliferation of the prepared scaffolds were checked with preosteoblast (MC3T3-E1) cells. Total Volume (TV), bone volume (BV), bone surface (BS), trabecular thickness (Tb.Th), trabecular number (Tb.N) and trabecular separation (Tb.Sp) were found to be higher in chitosan-nHA than chitosan-mHA scaffold. Hence, we suggest that chitosan-nHA scaffold could be a promising biomaterial for bone tissue engineering. PMID:24705167

Lee, Jong Seo; Baek, Sang Dae; Venkatesan, Jayachandran; Bhatnagar, Ira; Chang, Hee Kyung; Kim, Hui Taek; Kim, Se-Kwon

2014-06-01

116

Doped zinc oxide microspheres  

DOEpatents

A new composition and method of making same for a doped zinc oxide microsphere and articles made therefrom for use in an electrical surge arrestor which has increased solid content, uniform grain size and is in the form of a gel.

Arnold, Jr., Wesley D. (Oak Ridge, TN); Bond, Walter D. (Knoxville, TN); Lauf, Robert J. (Oak Ridge, TN)

1993-01-01

117

Doped zinc oxide microspheres  

DOEpatents

A new composition and method of making same for a doped zinc oxide microsphere and articles made therefrom for use in an electrical surge arrestor which has increased solid content, uniform grain size and is in the form of a gel. 4 figures.

Arnold, W.D. Jr.; Bond, W.D.; Lauf, R.J.

1993-12-14

118

Microsphere insulation systems  

NASA Technical Reports Server (NTRS)

A new insulation system is provided that contains microspheres. This insulation system can be used to provide insulated panels and clamshells, and to insulate annular spaces around objects used to transfer, store, or transport cryogens and other temperature-sensitive materials. This insulation system provides better performance with reduced maintenance than current insulation systems.

Allen, Mark S. (Inventor); Willen, Gary S. (Inventor); Mohling, Robert A. (Inventor)

2005-01-01

119

Polyvinyl pyridine microspheres  

NASA Technical Reports Server (NTRS)

Microspheres are produced by cobalt gamma radiation initiated polymerization of a dilute aqueous vinyl pyridine solution. Addition of cross-linking agent provides higher surface area beads. Addition of monomers such as hydroxyethylmethacrylate acrylamide or methacrylamide increases hydrophilic properties and surface area of the beads. High surface area catalytic supports are formed in the presence of controlled pore glass substrate.

Rembaum, Alan (Inventor); Gupta, Amitava (Inventor); Volksen, Willi (Inventor)

1980-01-01

120

Post-translational modification of osteopontin: Effects on in vitro hydroxyapatite formation and growth  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer Thrombin-cleaved fragments of milk-osteopontin effect hydroxyapatite formation differently. Black-Right-Pointing-Pointer N- and C-terminal fragments promoted hydroxyapatite formation and growth. Black-Right-Pointing-Pointer A central fragment inhibited hydroxyapatite formation and growth. Black-Right-Pointing-Pointer Binding to collagen or hydroxyapatite seed crystals modified these effects. -- Abstract: The manuscript tests the hypothesis that posttranslational modification of the SIBLING family of proteins in general and osteopontin in particular modify the abilities of these proteins to regulate in vitro hydroxyapatite (HA) formation. Osteopontin has diverse effects on hydroxyapatite (HA) mineral crystallite formation and growth depending on the extent of phosphorylation. We hypothesized that different regions of full-length OPN would also have distinct effects on the mineralization process. Thrombin fragmentation of milk OPN (mOPN) was used to test this hypothesis. Three fragments were tested in a de novo HA formation assay; an N-terminal fragment (aa 1-147), a central fragment (aa 148-204) denoted SKK-fragment and a C-terminal fragment (aa 205-262). Compared to intact mOPN the C- and N-terminal fragments behaved comparably, promoting HA formation and growth, but the central SKK-fragment acted as a mineralization inhibitor. In a seeded growth experiment all fragments inhibited mineral proliferation, but the SKK-fragment was the most effective inhibitor. These effects, seen in HA-formation and seeded growth assays in a gelatin gel system and in a pH-stat experiment were lost when the protein or fragments were dephosphorylated. Effects of the fully phosphorylated protein and fragments were also altered in the presence of fibrillar collagen. The diverse effects can be explained in terms of the intrinsically disordered nature of OPN and its fragments which enable them to interact with their multiple partners.

Boskey, Adele L., E-mail: boskeya@hss.edu [Musculoskeletal Integrity Program, Hospital for Special Surgery, New York, NY (United States); Christensen, Brian, E-mail: bc@mb.au.dk [Department of Molecular Biology and Genetics, Aarhus University (Denmark)] [Department of Molecular Biology and Genetics, Aarhus University (Denmark); Taleb, Hayat, E-mail: Talebh@hss.edu [Musculoskeletal Integrity Program, Hospital for Special Surgery, New York, NY (United States)] [Musculoskeletal Integrity Program, Hospital for Special Surgery, New York, NY (United States); Sorensen, Esben S., E-mail: ess@mb.au.dk [Department of Molecular Biology and Genetics, Aarhus University (Denmark)

2012-03-09

121

Effect of hydroxyapatite-based biomaterials on human osteoblast phenotype.  

PubMed

The present study evaluated human primary osteoblasts and two different osteoblast-like cell lines behaviour when cultured in presence of different hydroxyapatite-based (HA) biomaterials (SINTlife-FIN-CERAMICA S.p.a., Faenza, Italy; Bio-Oss, Geistlich Biomaterials, Woulhusen, Switzerland; Biostite-GABA Vebas, San Giuliano Milanese, MI, Italy), focusing attention on the effect of HA/Biostite in terms of modulation of osteoblastic differentiation. Analysis were about adhesion, proliferation and mineralization activity. Runt-related transcription factor 2 (Runx2), Estrogen Receptor alpha (ERalfa) expression and alkaline phosphatase activity (ALP) were measured as osteoblastic differentiation markers. Determination of viable cells was done with MTT colorimetric assay. Scanning electron microscopy (SEM) analysis was performed on biomaterial-treated cells. All hydroxyapatite-based biomaterials didn't affect cells morphology and viability, whereas only presence of HA/Biostite improved cells adhesion, growth and differentiation. Adhesion and spreading of the primary cells on HA/Biostite were the same showed by two different osteoblast-like cell lines. These results have important implications for both tissue-engineered bone grafts and enhancement of HA implants performance, to develop new teeth's supporting structure therapies and replacement. PMID:20357737

Trombelli, L; Penolazzi, L; Torreggiani, E; Farina, R; Lambertini, E; Vecchiatini, R; Piva, R

2010-03-01

122

Hydroxyapatite coated with insulin-like growth factor 1 (IGF1) stimulates human osteoblast activity in vitro.  

PubMed

We studied the effects of a hydroxyapatite-tricalcium phosphate material coated with Insulin-like Growth Factor 1 (IGF1) on cell growth, collagen synthesis and alkaline phosphatase activity (ALP) of human osteoblasts in vitro. Cell proliferation was stimulated when osteoblasts were incubated with untreated hydroxyapatite (HA) and it was further increased by exposure to IGF1-coated HA. 3H-Proline uptake was significantly increased by treatment with either HA or IGF1-coated HA but no significant differences were found between these two groups. ALP activity was enhanced by exposure to HA, with respect to the control, and further increased by treatment with IGF1-coated HA. Our findings suggest that HA is useful for promoting osteoblast activity and IGF1 may help to improve its biological characteristics. PMID:10366928

Zambonin, G; Grano, M; Greco, G; Oreffo, R O; Triffit, J T

1999-04-01

123

Hydroxyapatite and gelatin composite foams processed via novel freeze-drying and crosslinking for use as temporary hard tissue scaffolds  

Microsoft Academic Search

Hydroxyapatite (HA) and gelatin composites were fabricated in a foam type via a novel freeze-drying and crosslinking technique. The morphological and mechanical properties of and in vitro cellular responses to the foams were investigated. The HA powder was added at up to 30 wt % into the gelatin solution, and the mixtures were freeze- dried and further crosslinked. The pure

Hae-Won Kim; Jonathan C. Knowles; Hyoun-Ee Kim

2005-01-01

124

Osteogenic Properties of PBLG-g-HA/PLLA Nanocomposites  

PubMed Central

New development of biomaterial scaffolds remains a prominent issue for the regeneration of lost or fractured bone. Of these scaffolds, a number of bioactive polymers have been synthesized and fabricated for diverse biological roles. Although recent evidence has demonstrated that composite scaffolds such as HA/PLLA have improved properties when compared to either HA or PLLA alone, recent investigations have demonstrated that the phase compatibility between HA and PLLA layers is weak preventing optimal enhancement of the mechanical properties and making the composites prone to breakdown. In the present study, poly (?-benzyl-L-glutamate) modified hydroxyapatite/(poly (L-lactic acid)) (PBLG-g-HA/PLLA) composite scaffolds were fabricated with improved phase compatibility and tested for their osteogenic properties in 18 Wistar female rats by analyzing new bone formation in 3 mm bilateral femur defects in vivo. At time points, 2, 4 and 8 weeks post surgery, bone formation was evaluated by µ-CT and histological analysis by comparing 4 treatment groups; 1) blank defect, 2) PLLA, 3) HA/PLLA and 4) PBLG-g-HA/PLLA scaffolds. The in vivo analysis demonstrated that new bone formation was much more prominent in HA/PLLA and PBLG-g-HA/PLLA groups as depicted by µ-CT, H&E staining and immunohistochemistry for collagen I. TRAP staining was also utilized to determine the influence of osteoclast cell number and staining intensity to the various scaffolds. No significant differences in either staining intensity or osteoclast numbers between all treatment modalities was observed, however blank defects did contain a higher number of osteoclast-like cells. The results from the present study illustrate the potential of PBLG-g-HA/PLLA scaffolds for bone tissue engineering applications by demonstrating favorable osteogenic properties. PMID:25184285

Liao, Lan; Yang, Shuang; Miron, Richard J.; Wei, Junchao; Zhang, Yufeng; Zhang, Meng

2014-01-01

125

Biological reactivity of zirconia-hydroxyapatite composites.  

PubMed

Materials and devices intended for end-use applications as implants and medical devices must be evaluated to determine their biocompatibility potential in contact with physiological systems. The use of standard practices of biological testing provides a reasonable level of confidence concerning the response of a living organism to a given material or device, as well as guidance in selecting the proper procedures to be carried out for the screening of new or modified materials. This article presents results from cytotoxicity assays of cell culture, skin irritation, and acute toxicity by systemic and intracutaneous injections for powders, ceramic bodies, and extract liquids of hydroxyapatite (HA), calcia partially stabilized zirconia (ZO), and two types of zirconia-hydroxyapatite composites (Z4H6 and Z6H4) with potential for future use as orthopedic and dental implants. They indicate that these materials present potential for this type of application because they meet the requirements of the standard practices recommended for evaluating the biological reactivity of ATCC cell cultures (CCL1 NCTC clone 929 of mouse connective tissue and CCL 81 of monkey connective tissue) and animals (rabbit and mouse) with direct or indirect patient contact, or by the injection of specific extracts prepared from the material under test. In addition, studies involving short-term intramuscular and long-term implantation assays to estimate the reaction of living tissue to the composites studied, and investigations on long-term effects that these materials can cause on the cellular metabolism, are already in progress. PMID:12209904

Silva, Viviane V; Lameiras, Fernando S; Lobato, Zélia I P

2002-01-01

126

Effect of n-HA with different surface-modified on the properties of n-HA/PLGA composite  

NASA Astrophysics Data System (ADS)

Three different surface modification methods for nano-hydroxyapatite (n-HA) of stearic acid, grafted with L-lactide, combining stearic acid and surface-grafting L-lactic were adopted, respectively. The surface modification reaction and the effect of different methods were evaluated by Fourier transformation infrared (FTIR), X-ray photoelectron spectra (XPS), thermal gravimetric analysis (TGA), transmission electron microscopy (TEM). The results showed that n-HA surfaces were all successful modified, and the modification method of combining stearic acid and surface-grafting L-lactic had the greatest grafting amount and the best dispersion among the three modification methods. Then, the n-HA with three different surface modification and unmodified n-HA were introduced into PLGA, respectively, and a serials of n-HA/PLGA composites with 3% n-HA amount in weight were prepared by solution mixing, and the properties of n-HA/PLGA composites were also investigated by electromechanical universal tester and scanning electron microscope(SEM), comparing with PLGA. The results showed that the n-HA/PLGA composite with the n-HA surface modified by combining stearic acid and surface-grafting L-lactic had the highest bending strength and the best dispersion and interfacial adhesion among the three different modification methods, suggesting the surface modification of combining stearic acid and surface-grafting L-lactic was the most ideal method in this study, which has a great deal of enhancement of bending strength than PLGA, and it would be potential to be used in the field of bone fracture internal fixation in future.

Liuyun, Jiang; Chengdong, Xiong; Dongliang, Chen; Lixin, Jiang; xiubing, Pang

2012-10-01

127

Strontium-substituted hydroxyapatite coatings deposited via a co-deposition sputter technique.  

PubMed

The bioactivity of hydroxyapatite (HA) coatings can be modified by the addition of different ions, such as silicon (Si), lithium (Li), magnesium (Mg), zinc (Zn) or strontium (Sr) into the HA lattice. Of the ions listed here, strontium substituted hydroxyapatite (SrHA) coatings have received a lot of interest recently as Sr has been shown to promote osteoblast proliferation and differentiation, and reduce osteoclast activity. In this study, SrHA coatings were deposited onto titanium substrates using radio frequency (RF) magnetron co-sputtering (and compared to those surfaces deposited from HA alone). FTIR, XPS, XRD, and SEM techniques were used to analyse the different coatings produced, whereby different combinations of pure HA and 13% Sr-substituted HA targets were investigated. The results highlight that Sr could be successfully incorporated into the HA lattice to form SrHA coatings. It was observed that as the number of SrHA sputtering targets in the study were increased (increasing Sr content), the deposition rate decreased. It was also shown that as the Sr content of the coatings increased, so did the degree of preferred 002 orientation of the coating (along with obvious changes in the surface morphology). This study has shown that RF magnetron sputtering (specifically co-sputtering), offers an appropriate methodology to control the surface properties of Sr-substituted HA, such as the crystallinity, stoichiometry, phase purity and surface morphology. PMID:25491990

Boyd, A R; Rutledge, L; Randolph, L D; Meenan, B J

2015-01-01

128

Porous microsphere and its applications  

PubMed Central

Porous microspheres have drawn great attention in the last two decades for their potential applications in many fields, such as carriers for drugs, absorption and desorption of substances, pulmonary drug delivery, and tissue regeneration. The application of porous microspheres has become a feasible way to address existing problems. In this essay, we give a brief introduction of the porous microsphere, its characteristics, preparation methods, applications, and a brief summary of existing problems and research tendencies. PMID:23515359

Cai, Yunpeng; Chen, Yinghui; Hong, Xiaoyun; Liu, Zhenguo; Yuan, Weien

2013-01-01

129

Mechanical performance and osteoblast-like cell responses of fluorine-substituted hydroxyapatite and zirconia dense composite  

Microsoft Academic Search

A fluorine-substituted hydroxyapatite (FHA) and zirconia (ZrO2) dense composite (50:50 by volume) was fabricated, and its feasibility for hard tissue applications was investigated in terms of its mechanical properties and osteo- blast-like cell (MG63) responses in vitro. The incorporation of fluorine into the hydroxyapatite (HA) structure was highly effective in producing a completely dense apatite-ZrO2 composite through a pressureless sintering

Hae-Won Kim; Jonathan C. Knowles; Long-Hao Li; Hyoun-Ee Kim

2005-01-01

130

Collagen-hydroxyapatite composites for hard tissue repair.  

PubMed

Bone is the most implanted tissue after blood. The major solid components of human bone are collagen (a natural polymer, also found in skin and tendons) and a substituted hydroxyapatite (a natural ceramic, also found in teeth). Although these two components when used separately provide a relatively successful mean of augmenting bone growth, the composite of the two natural materials exceeds this success. This paper provides a review of the most common routes to the fabrication of collagen (Col) and hydroxyapatite (HA) composites for bone analogues. The regeneration of diseased or fractured bones is the challenge faced by current technologies in tissue engineering. Hydroxyapatite and collagen composites (Col-HA) have the potential in mimicking and replacing skeletal bones. Both in vivo and in vitro studies show the importance of collagen type, mineralisation conditions, porosity, manufacturing conditions and crosslinking. The results outlined on mechanical properties, cell culturing and de-novo bone growth of these devices relate to the efficiency of these to be used as future bone implants. Solid free form fabrication where a mould can be built up layer by layer, providing shape and internal vascularisation may provide an improved method of creating composite structures. PMID:16568401

Wahl, D A; Czernuszka, J T

2006-01-01

131

Single-walled carbon nanotubes/hydroxyapatite coatings on titanium obtained by electrochemical deposition  

NASA Astrophysics Data System (ADS)

Single-walled carbon nanotubes/hydroxyapatite (SWNTs/HA) composite coatings were successfully fabricated by electrochemical deposition technique. Different concentrations of SWNTs were incorporated into the apatite coating by adding functionalized SWNTs into the electrolyte. Homogeneous and crack-free SWNTs/HA composite coatings were achieved and the coatings had higher crystallinity compared to pure HA coating. In addition, the highest bonding strength of the SWNTs/HA coating reached 25.7 MPa, which was nearly 70% higher than that of pure HA coating. The in-vitro cellular biocompatibility tests revealed that SWNTs/HA composite coatings exhibited higher in-vitro bioactivity than that of pure HA coating and pure titanium (Ti). It suggests that SWNTs/HA composite coating may have enormous potential applications in the field of biomaterials, especially for the metal implants.

Pei, Xibo; Zeng, Yongxiang; He, Rui; Li, Zhongjie; Tian, Lingyang; Wang, Jian; Wan, Qianbing; Li, Xiaoyu; Bao, Hong

2014-03-01

132

Auger electron spectroscopy and its use for the characterization of titanium and hydroxyapatite surfaces  

Microsoft Academic Search

This review paper provides the basic background and underlying theory behind Auger electron spectroscopy (AES). Among the many surface analytical tools, AES has been shown to be very effective for surface composition analysis. These analyses are critically needed to better understand the interactions between the host and implant. The use of AES for titanium (Ti) and hydroxyapatite (HA) biomaterials characterization

J. L. Ong; L. C. Lucas

1998-01-01

133

Deposition of hydroxyapatite thin films by Nd:YAG laser ablation: a microstructural study  

SciTech Connect

Hydroxyapatite (HA) thin films has been successfully deposited by Nd:YAG laser ablation at {lambda} = 532 nm. The morphology and microstructure of the deposited layers was studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high resolution electron microscopy (HREM). Polycrystalline HA films were directly obtained with the substrate at 300 deg. C and without introducing water vapors in the deposition chamber. Electron paramagnetic resonance (EPR) measurements show that the oxygen stoichiometry in the HA films is also maintained. Depositions performed at {lambda} = 335 nm laser wavelength and 300 deg. C substrate temperature resulted in polycrystalline layers of mixed composition of HA and tricalciumphosphate (TCP)

Nistor, L.C. [National Institute of Materials Physics, P.O. Box MG-7, Magurele, RO-76900, Bucharest (Romania); Ghica, C. [National Institute of Materials Physics, P.O. Box MG-7, Magurele, RO-76900, Bucharest (Romania); Teodorescu, V.S. [National Institute of Materials Physics, P.O. Box MG-7, Magurele, RO-76900, Bucharest (Romania); Nistor, S.V. [National Institute of Materials Physics, P.O. Box MG-7, Magurele, RO-76900, Bucharest (Romania)]. E-mail: snistor@alpha1.infim.ro; Dinescu, M. [National Institute of Lasers, Plasma and Radiation Physics, P.O. Box MG-26, Magurele, RO-76900, Bucharest (Romania); Matei, D. [National Institute of Lasers, Plasma and Radiation Physics, P.O. Box MG-26, Magurele, RO-76900, Bucharest (Romania); Frangis, N. [Aristotle University of Thessaloniki, Department of Physics, GR-54124 Thessaloniki (Greece); Vouroutzis, N. [Aristotle University of Thessaloniki, Department of Physics, GR-54124 Thessaloniki (Greece); Liutas, C. [Aristotle University of Thessaloniki, Department of Physics, GR-54124 Thessaloniki (Greece)

2004-11-02

134

Preparation and histological evaluation of biomimetic three-dimensional hydroxyapatite\\/chitosan-gelatin network composite scaffolds  

Microsoft Academic Search

A novel biodegradable hydroxyapatite\\/chitosan-gelatin network (HA\\/CS-Gel) composite of similar composition to that of normal human bone was prepared as a three-dimensional biomimetic scaffold by phase separation method for bone tissue engineering. Changing the solid content and the compositional variables of the original mixtures allowed control of the porosities and densities of the scaffolds. The HA granules were dispersed uniformly in

Feng Zhao; Yuji Yin; William W. Lu; J. Chiyan Leong; Wenyi Zhang; Jingyu Zhang; Mingfang Zhang; Kangde Yao

2002-01-01

135

Hard-tissue-engineered zirconia porous scaffolds with hydroxyapatite sol-gel and slurry coatings  

Microsoft Academic Search

A zirconia (ZrO2) porous scaffold was coated with a gradient apatite layer to induce osteoconductivity with the use of a combination of sol- gel and powder slurry methods. The ZrO2 was used to impart mechanical strength and the apatite layer was coated for functional biocompatibility. The coating layer, from the outside in, was composed of sol- gel hydroxyapatite (HA)\\/slurry HA\\/slurry

Hae-Won Kim; Hyoun-Ee Kim; Jonathan C. Knowles

2004-01-01

136

Magnetron co-sputtered silicon-containing hydroxyapatite thin films—an in vitro study  

Microsoft Academic Search

The use of silicon-substituted hydroxyapatite (Si-HA) as a biomaterial has been reported recently. In vivo testing has shown that Si-HA promotes early bonding of the bone\\/implant interface. In order to extend its usage to major load-bearing applications such as artificial hip replacement implants, it has been proposed that the material could be used in the form of a coating on

E. S. Thian; J. Huang; S. M. Best; Z. H. Barber; W. Bonfield

2005-01-01

137

Dextran-based microspheres as controlled delivery systems for proteins.  

E-print Network

??Dextran-based microspheres as controlled delivery systems for proteins Dextran based microspheres are investigated as controlled delivery system for proteins. Microspheres were prepared by polymerization of… (more)

Vlugt-Wensink, K.D.F.

2007-01-01

138

Effects of bioactive glass, hydroxyapatite and bioactive glass – Hydroxyapatite composite graft particles in the treatment of infrabony defects  

PubMed Central

Background: Several synthetic alloplastic materials have been used in the past as an implant in infrabony defects with a goal to reconstruct the lost part of attachment apparatus via new osseous tissue formation. The present study was undertaken to evaluate and compare clinico-radiographically, the effect of bioactive glass (BG), hydroxyapatite (HA), and BG-HA composite bone graft particles in the treatment of human infra-bony periodontal defects. Materials and Methods: Indigenous synthetic HA, BG, and BG-HA composite bone graft materials were developed in the laboratory. Twenty eight infrabony periodontal defects were equally distributed (i.e., seven defects) into four groups. The defects were treated separately with three types of graft materials and non-grafted manner (open flap debridement alone, control) to evaluate both the soft and hard tissue responses after six months of surgery. Evaluation was done by studying different parameters such as plaque index, gingival index, relative attachment level, probing pocket depth, and radiographic bone fill in Intra Oral Peri-Apical radiograph. Results: The healing of defects was uneventful and free of any biological complications. The gain in relative attachment level, reduction of probing pocket depth, and bone fill was statistically significant in all four groups. BG and BG-HA synthetic bone graft implanted sites showed significant bone fill (P<0.05) than hydroxyapatite and unimplanted control sites. Conclusion: The performance of BG and its composite was better compared to HA and open flap debridement alone for the reconstruction of infrabony defects. The BG-HA composite particles may effectively be used as an alternative bone graft material for infrabony defects. PMID:23055592

Mistry, Surajit; Kundu, Debabrata; Datta, Someswar; Basu, Debabrata

2012-01-01

139

Hydroxyapatite fiber reinforced poly(alpha-hydroxy ester) foams for bone regeneration  

NASA Technical Reports Server (NTRS)

A process has been developed to manufacture biodegradable composite foams of poly(DL-lactic-co-glycolic acid) (PLGA) and hydroxyapatite short fibers for use in bone regeneration. The processing technique allows the manufacture of three-dimensional foam scaffolds and involves the formation of a composite material consisting of a porogen material (either gelatin microspheres or salt particles) and hydroxyapatite short fibers embedded in a PLGA matrix. After the porogen is leached out, an open-cell composite foam remains which has a pore size and morphology defined by the porogen. By changing the weight fraction of the leachable component it was possible to produce composite foams with controlled porosities ranging from 0.47 +/- 0.02 to 0.85 +/- 0.01 (n = 3). Up to a polymer:fiber ratio of 7:6, short hydroxyapatite fibers served to reinforce low-porosity PLGA foams manufactured using gelatin microspheres as a porogen. Foams with a compressive yield strength up to 2.82 +/- 0.63 MPa (n = 3) and a porosity of 0.47 +/- 0.02 (n = 3) were manufactured using a polymer:fiber weight ratio of 7:6. In contrast, high-porosity composite foams (up to 0.81 +/- 0.02, n = 3) suitable for cell seeding were not reinforced by the introduction of increasing quantities of hydroxyapatite short fibers. We were therefore able to manufacture high-porosity foams which may be seeded with cells but which have minimal compressive yield strength, or low porosity foams with enhanced osteoconductivity and compressive yield strength.

Thomson, R. C.; Yaszemski, M. J.; Powers, J. M.; Mikos, A. G.; McIntire, L. V. (Principal Investigator)

1998-01-01

140

Metal containing polymeric functional microspheres  

NASA Technical Reports Server (NTRS)

Polymeric functional microspheres containing metal or metal compounds are formed by addition polymerization of a covalently bondable olefinic monomer such as hydroxyethylmethacrylate in the presence of finely divided metal or metal oxide particles, such as iron, gold, platinum or magnetite, which are embedded in the resulting microspheres. The microspheres can be covalently bonded to chemotherapeutic agents, antibodies, or other proteins providing a means for labeling or separating labeled cells. Labeled cells or microspheres can be concentrated at a specific body location such as in the vicinity of a malignant tumor by applying a magnetic field to the location and then introducing the magnetically attractable microspheres or cells into the circulatory system of the subject. Labeled cells can be separated from a cell mixture by applying a predetermined magnetic field to a tube in which the mixture is flowing. After collection of the labeled cells, the magnetic field is discontinued and the labeled sub-cell population recovered.

Yen, Shiao-Ping S. (Inventor); Rembaum, Alan (Inventor); Molday, Robert S. (Inventor)

1979-01-01

141

Immunofluorescence detection methods using microspheres  

NASA Astrophysics Data System (ADS)

Microsphere-based immunoassays were devised for compounds of agricultural and biomedical interest (e.g., digoxin, theophylline, and zearalenone). Commercially available microspheres with surface functional groups for chemical derivatization were used as solid carriers. After immobilizing the target substances, the surface of the haptenized microspheres was blocked by a protein to reduce aspecific binding. Competitive immunoassays were performed using the functionalized microspheres and antibodies labeled with horseradish peroxidase. Immunofluorescence signal amplification was achieved by enzyme-catalyzed reporter deposition (CARD). An epifluorescence microscope, a CCD camera interfaced with a computer, and microscopy image analysis software were employed for quantitative detection of fluorescent light emitted from individual microspheres. Integration of several such immunoassays and application of an optical encoding method enabled multianalyte determination. These immunoassays can also be utilized in an immunosensor array format. This immunoarray format could facilitate miniaturization and automation of multianalyte immunoassays.

Szurdoki, Ferenc; Michael, Karri L.; Agrawal, Divya; Taylor, Laura C.; Schultz, Sandra L.; Walt, David R.

1999-01-01

142

Syntheses of near-net-shaped monolithic hydroxyapatite and hydroxyapatite-ASTM F75 composites by the oxidation of solid metal-bearing precursors  

Microsoft Academic Search

A novel powder-metallurgical route was used to fabricate near net-shaped hydroxyapatite, Ca10(PO4)6(OH)2 (HA) and HA+Co-C-Mo composite bodies. Ca and beta-Ca2P 2O7 with Ca\\/P ˜ 1.67 was intimately mixed by high-energy mechanical alloying, formed into desired shapes by pressing and machining, and then converted into HA with a series of heat treatments: a 600°C annealing in dry O2 completely oxidized calcium

Eaden Saw

1999-01-01

143

Soil and Water Lab, DNA Microsphere Procedure Page 1 Protocol for Making DNA Microspheres Large Batch  

E-print Network

Soil and Water Lab, DNA Microsphere Procedure Page 1 Protocol for Making DNA Microspheres ­ Large Batch Last Updated 24 June 2014 Goal: Incorporate DNA into PLA microspheres. DNA serves as identification of specific tracer

Walter, M.Todd

144

Nano hydroxyapatite-coated implants improve bone nanomechanical properties.  

PubMed

Nanostructure modification of dental implants has long been sought as a means to improve osseointegration through enhanced biomimicry of host structures. Several methods have been proposed and demonstrated for creating nanotopographic features; here we describe a nanoscale hydroxyapatite (HA)-coated implant surface and hypothesize that it will hasten osseointegration and improve its quality relative to that of non-coated implants. Twenty threaded titanium alloy implants, half prepared with a stable HA nanoparticle surface and half grit-blasted, acid-etched, and heat-treated (HT), were inserted into rabbit femurs. Pre-operatively, the implants were morphologically and topographically characterized. After 3 weeks of healing, the samples were retrieved for histomorphometry. The nanomechanical properties of the surrounding bone were evaluated by nanoindentation. While both implants revealed similar bone-to-implant contact, the nanoindentation demonstrated that the tissue quality was significantly enhanced around the HA-coated implants, validating the postulated hypothesis. PMID:23045363

Jimbo, R; Coelho, P G; Bryington, M; Baldassarri, M; Tovar, N; Currie, F; Hayashi, M; Janal, M N; Andersson, M; Ono, D; Vandeweghe, S; Wennerberg, A

2012-12-01

145

Hydroxyapatite-nanotube composites and coatings for orthopedic applications  

NASA Astrophysics Data System (ADS)

Hydroxyapatite (HA) has received wide attention in orthopedics, due to its biocompatibility and osseointegration ability. Despite these advantages, the brittle nature and low fracture toughness of HA often results in rapid wear and premature fracture of implant. Hence, there is a need to improve the fracture toughness and wear resistance of HA without compromising its biocompatibility. The aim of the current research is to explore the potential of nanotubes as reinforcement to HA for orthopedic implants. HA- 4 wt.% carbon nanotube (CNT) composites and coatings are synthesized by spark plasma sintering and plasma spraying respectively, and investigated for their mechanical, tribological and biological behavior. CNT reinforcement improves the fracture toughness (>90%) and wear resistance (>66%) of HA for coating and free standing composites. CNTs have demonstrated a positive influence on the proliferation, differentiation and matrix mineralization activities of osteoblasts, during in-vitro biocompatibility studies. In-vivo exposure of HA-CNT coated titanium implant in animal model (rat) shows excellent histocompatibility and neobone integration on the implant surface. The improved osseointegration due to presence of CNTs in HA is quantified by the adhesion strength measurement of single osteoblast using nano-scratch technique. Considering the ongoing debate about cytotoxicity of CNTs in the literature, the present study also suggests boron nitride nanotube (BNNT) as an alternative reinforcement. BNNT with the similar elastic modulus and strength as CNT, were added to HA. The resulting composite having 4 wt.% BNNTs improved the fracture toughness (˜85%) and wear resistance (˜75%) of HA in the similar range as HA-CNT composites. BNNTs were found to be non-cytotoxic for osteoblasts and macrophages. In-vitro evaluation shows positive role of BNNT in osteoblast proliferation and viability. Apatite formability of BNNT surface in ˜4 days establishes its osseointegration ability.

Lahiri, Debrupa

146

Ultrasound-assisted fabrication of a biocompatible magnetic hydroxyapatite.  

PubMed

This work describes the fabrication and characterization of a biocompatible magnetic hydroxyapatite (HA) using an ultrasound-assisted co-precipitation method. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and transmission electron microscopy (TEM) were used to characterize the structure and chemical composition of the produced samples. The M-H loops of synthesized materials were traced using a vibrating sample magnetometer (VSM) and the biocompatibility was evaluated by cell culture and MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. Furthermore, in vivo histopathological examinations were used to evaluate the potential toxicological effects of Fe?O?-HA composites on kidney of SD rats injected intraperitoneally with Fe?O?-HA particles. The results showed that magnetic iron oxide particles first replace OH ions of HA, which are parallel to the c axis, and then enter the HA crystal lattice which produces changes in the crystal surface of HA. Chemical bond interaction was observed between PO?³? groups of HA and iron ions of Fe?O?. The saturation magnetization (MS ) of Fe?O?-HA composites was 46.36 emu/g obtained from VSM data. Cell culture and MTT assays indicated that HA could affect the growth and proliferation of HEK-293 cells. This Fe?O?-HA composite produced no negative effects on cell morphology, viability, and proliferation and exhibited remarkable biocompatibility. Moreover, no inflammatory cell infiltration was observed in kidney histopathology slices. Therefore, this study succeeds to develop a Fe?O?-HA composite as a prospective biomagnetic material for future applications. PMID:24339231

Zhou, Gang; Song, Wei; Hou, Yongzhao; Li, Qing; Deng, Xuliang; Fan, Yubo

2014-10-01

147

Effects of hepatic arterial yttrium 90 glass microspheres in dogs.  

PubMed

A 22-micron glass microsphere called TheraSphere (Theragenics Corp., Atlanta, GA) has been developed in which yttrium 89 oxide is incorporated into the glass matrix and is activated by neutron bombardment to form the beta-emitting isotope yttrium 90 (Y 90) before using the spheres as radiotherapeutic vehicles. The injection of up to 12 times (on a liver weight basis) the anticipated human dose of nonradioactive TheraSphere into the hepatic arteries of dogs was well tolerated and produced clinically silent alterations within centrolobular areas. The hepatic arterial (HA) injection of radioactive TheraSphere also produced portal changes similar to those observed in humans after external beam therapy. While the extent of damage increased with the delivered dose, radiation exposures in excess of 30,000 cGy did not cause total hepatic necrosis and were compatible with survival. No microspheres distributed to the bone marrow and absolutely no myelosuppression was encountered in any animal. Proposed hepatic exposures to humans of 5000 to 10,000 cGy by means of these microspheres, therefore, would appear to be feasible and tolerable. Radiotherapeutic microsphere administration preceded by regional infusion of a radiosensitizing agent and/or immediately following the redistribution of blood flow toward intrahepatic tumor by vasoactive agents can potentially yield a synergistic, highly selective attack on tumors confined to the liver. PMID:3345490

Wollner, I; Knutsen, C; Smith, P; Prieskorn, D; Chrisp, C; Andrews, J; Juni, J; Warber, S; Klevering, J; Crudup, J

1988-04-01

148

Fabrication and characterization of sol–gel derived hydroxyapatite\\/zirconia composite nanopowders with various yttria contents  

Microsoft Academic Search

Homogeneous composite nanopowders of hydroxyapatite\\/30wt% yttria-stabilized zirconia (HA–YSZ) containing 0, 3, 5, and 8mol% Y2O3 (namely; HA–0YSZ, HA–3YSZ, HA–5YSZ, and HA–8YSZ) were successfully synthesized using the sol–gel method. Simultaneous thermal analysis (STA), X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), Fourier transformed infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques were utilized to characterize the prepared

S. Salehi; M. H. Fathi

2010-01-01

149

Effects of hydroxyapatite and Biostite on osteogenic induction of hMSC.  

PubMed

When isolated from the iliac crest human mesenchymal stem cells (hMSC) differentiate into osteoblast-like cells with appropriate stimulation in culture. This in vitro study tested the hypothesis that Biostite and hydroxyapatite (HA) affect proliferation and differentiation of hMSC into osteoblastic cells. Cell proliferation was determined by measuring 3H-thymidine incorporation into DNA and typical markers of osteoblastic phenotype were determined by RT-PCR assay. No differences emerged in cell proliferation cultures with Biostite or hydroxyapatite (HA), but gene expression analysis revealed higher expression of collagen,alkaline phosphatase (ALP), osteopontin and bone sialoprotein (BSP) in the presence of Biostite. TGFb2 production, as assessed by an Elisa kit, and Runx2 expression by RT-PCR, were greater in Biostite cultures, suggesting Biostite provides a better environment for hMSC differentiation into osteoblasts and is, potentially, a more promising bone-filling material than HA. PMID:20077014

Marinucci, Lorella; Balloni, Stefania; Becchetti, Ennio; Bistoni, Giovanni; Calvi, Edoardo Maria; Lumare, Eleonora; Ederli, Filippo; Locci, Paola

2010-03-01

150

Hydroxyapatite thin films synthesized by Pulsed Laser Deposition onto titanium mesh implants for cranioplasty applications  

NASA Astrophysics Data System (ADS)

We report on the synthesis of advanced nanostructured hydroxyapatite thin films onto 3D titanium (Ti) mesh substrates by Pulsed Laser Deposition method. Morphological and structural investigations as well as pull-out tests proved the stoichiometric transfer of crystalline hydroxyapatite (HA) films along with their good adherence. In vivo tests were performed on 12 patients (six with simple Ti mesh, six with Ti mesh biofunctionalized with HA). The tomodensitometry analysis of the cranial control scans evidenced the process of osseogenesis. For four patients with implanted HA/Ti mesh structures, the modification of the value obtained on Hounsfield scale was observed at the level of implant, proving the progress of osseointegration. We conclude that the structures exhibit excellent bonding strength and functionality, and are suitable for neurosurgical applications.

Duta, L.; Stan, G. E.; Popescu, A. C.; Socol, G.; Miroiu, F. M.; Mihailescu, I. N.; Ianculescu, A.; Poeata, I.; Chiriac, A.

2013-06-01

151

Influence of hydroxyapatite on the corrosion resistance of the Ti-13Nb-13Zr alloy.  

PubMed

Electrochemical analyses on the biocompatible alloy Ti-13Nb-13Zr wt% in an electrolyte simulating physiological medium (PBS solution) are reported. Hydroxyapatite (HA) films were obtained on the alloy by electrodeposition at constant cathodic current. Samples of the alloy covered with an anodic-oxide film or an anodic-oxide/HA film were analyzed by open circuit potential and electrochemical impedance spectroscopy measurements during 180 days in the PBS electrolyte. Analyses of the open-circuit potential (E (oc)) values indicated that the oxide/HA film presents better protection characteristics than the oxide only. This behavior was corroborated by the higher film resistances obtained from impedance data, indicating that, besides improving the alloy osteointegration, the hydroxyapatite film may also increase the corrosion protection of the biomaterial. PMID:19083081

Duarte, Laís T; Biaggio, Sonia R; Rocha-Filho, Romeu C; Bocchi, Nerilso

2009-05-01

152

Hydroxyapatite-magnetite-MWCNT nanocomposite as a biocompatible multifunctional drug delivery system for bone tissue engineering  

NASA Astrophysics Data System (ADS)

New magnetic hydroxyapatite-based nanomaterials as bone-specific systems for controlled drug delivery have been synthesized. The synthesized hydroxyapatite, HA, decorated with magnetite nanoparticles by a deposition method (HA/Fe3O4) and the nanocomposite system obtained using magnetic multi-walled carbon nanotubes (HA/MWCNT/Fe3O4) as a filler for HA have been characterized by chemical and morphological analyses, and their biological behavior was investigated. The systems have also been doped with clodronate in order to combine the effect of bone biomineralization induced by hydroxyapatite-based composites with the decrease of osteoclast formation induced by the drug. An analysis of the preosteoclastic RAW264.7 cell proliferation by MTT assay confirmed the high biocompatibility of the three systems. TRAP staining of RAW 264.7 conditioned with sRAKL to induce osteoclastogenesis, cultured in the presence of the systems doped and undoped with clodronate, showed the inhibitory effect of clodronate after we counted the MNC TRAP+cells but only in the osteoclast formation; in particular, the system HA/Fe3O4-Clo exerted a high inhibitory effect compared to the drug alone. These results demonstrate that the synthesized nanocomposites are a biocompatible magnetic drug delivery system and can represent a useful multimodal platform for applications in bone tissue engineering.

Pistone, Alessandro; Iannazzo, Daniela; Panseri, Silvia; Montesi, Monica; Tampieri, Anna; Galvagno, Signorino

2014-10-01

153

Towards Monodispersed Polymer Microspheres  

NASA Astrophysics Data System (ADS)

Uniform polymer microspheres prepared by Spinning Disk Atomization Our spinning disk atomization (SDA) can, relative to other existing techniques, produce micron-sized particles of very narrow size distribution. Around the edge of the disk, small teeth channel the flow into identical droplets that are flung off over the disk rim. These solidify during flight to form spherical particles. Applications for spheres produced by SDA can be found in areas such as adhesives, powder coatings, food, biomedical use, drug delivery systems, etc. We have atomized polyethyleneglycol into very narrowly dispersed microspheres ranging from 50 to 500 =B5m. The aim of this work is to model the droplet formation occurring at the rim of the spinning disk in order to better understand the experimental results. The viscosity contribution in the fluid breakup is qualitatively analyzed and is adapted to the theoretical model to show how it affects the droplet size. We have used the pendant drop model (Ramesh Babu, S. Journal of Colloid and Interface Science 116, 350-372 (1987).) for spinning disk atomization to describe the drop-shape evolution during growth.

Senuma, Yoshinori; Hilborn, Jons

1998-03-01

154

Effect of different sintering methods on bioactivity and release of proteins from PLGA microspheres  

PubMed Central

Macromolecule release from poly(d,l-lactide-co-glycolide) (PLGA) microspheres has been well-characterized, and is a popular approach for delivering bioactive signals from tissue-engineered scaffolds. However, the effect of some processing solvents, sterilization, and mineral incorporation (when used in concert) on long-term release and bioactivity has seldom been addressed. Understanding these effects is of significant importance for microsphere-based scaffolds, given that these scaffolds are becoming increasingly more popular, yet growth factor activity following sintering and/or sterilization is heretofore unknown. The current study evaluated the 6-week release of transforming growth factor (TGF)-?3 and bone morphogenetic protein (BMP)-2 from PLGA and PLGA/hydroxyapatite (HAp) microspheres following exposure to ethanol (EtOH), dense phase carbon dioxide (CO2), or ethylene oxide (EtO). EtO was chosen based on its common use in scaffold sterilization, whereas EtOH and CO2 were chosen given their importance in sintering microspheres together to create scaffolds. Release supernatants were then used in an accelerated cell stimulation study with human bone marrow stromal cells (hBMSCs) with monitoring of gene expression for major chondrogenic and osteogenic markers. Results indicated that in microspheres without HAp, EtOH exposure led to the greatest amount of delivery, whilst those treated with CO2 delivered the least growth factor. In contrast, formulations with HAp released almost half as much protein, regardless of EtOH or CO2 exposure. Notably, EtO exposure was not found to significantly affect the amount of protein released. Cell stimulation studies demonstrated that eluted protein samples performed similarly to positive controls in PLGA-only formulations, and ambiguously in PLGA/HAp composites. In conclusion, the use of EtOH, subcritical CO2, and EtO in microsphere-based scaffolds may have only slight adverse effects, and possibly even desirable effects in some cases, on protein availability and bioactivity. PMID:23910352

Dormer, Nathan H.; Gupta, Vineet; Scurto, Aaron M.; Berkland, Cory J.; Detamore, Michael S.

2013-01-01

155

Surface characteristics of a novel hydroxyapatite-coated dental implant  

PubMed Central

Purpose This study evaluated the surface characteristics and bond strength produced using a novel technique for coating hydroxyapatite (HA) onto titanium implants. Methods HA was coated on the titanium implant surface using a super-high-speed (SHS) blasting method with highly purified HA. The coating was performed at a low temperature, unlike conventional HA coating methods. Coating thickness was measured. The novel HA-coated disc was fabricated. X-ray diffraction analysis was performed directly on the disc to evaluate crystallinity. Four novel HA-coated discs and four resorbable blast medium (RBM) discs were prepared. Their surface roughnesses and areas were measured. Five puretitanium, RBM-treated, and novel HA-coated discs were prepared. Contact angle was measured. Two-way analysis of variance and the post-hoc Scheffe's test were used to analyze differences between the groups, with those with a probability of P<0.05 considered to be statistically significant. To evaluate exfoliation of the coating layer, 7 sites on the mandibles from 7 mongrel dogs were used. Other sites were used for another research project. In total, seven novel HA-coated implants were placed 2 months after extraction of premolars according to the manufacturer's instructions. The dogs were sacrificed 8 weeks after implant surgery. Implants were removed using a ratchet driver. The surface of the retrieved implants was evaluated microscopically. Results A uniform HA coating layer was formed on the titanium implants with no deformation of the RBM titanium surface microtexture when an SHS blasting method was used. Conclusions These HA-coated implants exhibited increased roughness, crystallinity, and wettability when compared with RBM implants. PMID:22586524

Jung, Ui-Won; Hwang, Ji-Wan; Choi, Da-Yae; Hu, Kyung-Seok; Kwon, Mi-Kyung; Choi, Seong-Ho

2012-01-01

156

Augmentation of engineered cartilage to bone integration using hydroxyapatite.  

PubMed

Articular cartilage injuries occur frequently in the knee joint. Photopolymerizable cartilage tissue engineering approaches appear promising; however, fundamentally, forming a stable interface between the subchondral bone and tissue engineered cartilage components remains a major challenge. We investigated the utility of hydroxyapatite (HA) nanoparticles to promote controlled bone-growth across the bone-cartilage interface in an in vitro engineered tissue model system using bone marrow derived stem cells. Samples incorporated with HA demonstrated significantly higher interfacial shear strength (at the junction between engineered cartilage and engineered bone) compared with the constructs without HA (p < 0.05), after 28 days of culture. Interestingly, this increased interfacial shear strength due to the presence of HA was observed as early as 7 days and appeared to have sustained itself for an additional three weeks without interacting with strength increases attributable to subsequent secretion of engineered tissue matrix. Histological evidence showed that there was ?7.5% bone in-growth into the cartilage region from the bone side. The mechanism of enhanced engineered cartilage to bone integration with HA incorporation appeared to be facilitated by the deposition of calcium phosphate in the transition zone. These findings indicate that controlled bone in-growth using HA incorporation permits more stable anchorage of the injectable hydrogel-based engineered cartilage construct via augmented integration between bone and cartilage. PMID:24259264

Dua, Rupak; Centeno, Jerry; Ramaswamy, Sharan

2014-07-01

157

Development of electrochemical folic acid sensor based on hydroxyapatite nanoparticles  

NASA Astrophysics Data System (ADS)

We report the synthesis of hydroxyapatite (HA) nanoparticles (NPs) by a simple microwave irradiation method and its application as sensing element for the precise determination of folic acid (FA) by electrochemical method. The structure and composition of the HA NPs characterized using XRD, FTIR, Raman and XPS. SEM and EDX studies confirmed the formation of elongated spherical shaped HA NPs with an average particle size of about 34 nm. The HA NPs thin film on glassy carbon electrode (GCE) were deposited by drop casting method. Electrocatalytic behavior of FA in the physiological pH 7.0 was investigated by cyclic voltammetry (CV), linear sweep voltammetry (LSV) and chronoamperometry. The fabricated HA/GCE exhibited a linear calibration plot over a wide FA concentration ranging from 1.0 × 10-7 to 3.5 × 10-4 M with the detection limit of 75 nM. In addition, the HA NPs modified GCE showed good selectivity toward the determination of FA even in the presence of a 100-fold excess of ascorbic acid (AA) and 1000-fold excess of other common interferents. The fabricated biosensor exhibits good sensitivity and stability, and was successfully applied for the determination of FA in pharmaceutical samples.

Kanchana, P.; Sekar, C.

2015-02-01

158

Weibull modulus and fracture strength of highly porous hydroxyapatite.  

PubMed

Porous hydroxyapatite (HA) is used in a variety of applications including biomedical materials such as engineered bone materials and microbe filters. Despite the utility of the Weibull modulus, m, as a gauge of the mechanical reliability of brittle solids, there have been very few studies of m for porous HA. A recent study of porous HA that included the current authors (Fan, X., Case, E.D., Ren, F., Shu, Y., Baumann, M.J., 2012a. Journal of the Mechanical Behavior of Biomedical Materials. 8, 21-36) showed increases in m for porosity, P, approaching PG, the porosity of the green (unfired) specimen. In this paper, 18 groups of highly porous HA specimens (12 groups fabricated in this study and 6 groups from Fan et al., 2012a) were analyzed with P values from 0.59 to 0.62, where PG=0.62. The partially sintered HA specimens were fractured in biaxial flexure using a ring-on-ring test fixture. The fracture strength decreased monotonically with decreasing sintering temperature, Tsinter, from 4.8MPa for specimens sintered at 1025°C-0.66MPa for specimens sintered at 350°C. However, the Weibull modulus remained surprisingly high, ranging from 6.6 to 15.5. In comparison, for HA specimens with intermediate values of P, from about 0.1-0.55, the Weibull modulus tended to be lower (ranging from about 4 to 11) than the highly porous specimens included in this study. PMID:23478051

Fan, X; Case, E D; Gheorghita, I; Baumann, M J

2013-04-01

159

Valency-dependent affinity of bioactive hydroxyapatite-binding dendrons.  

PubMed

Hydroxyapatite (HA)-coated surfaces are used widely as stationary phase for protein and enzyme purification, coatings for dental and orthopedic implants, and composite materials for tissue engineering substrates. More advanced applications are envisioned, but progress has been slowed by the limited ability to controllably functionalize the surface of HA with biomolecules in a translationally relevant manner. Herein we report the synthesis and characterization of a series of multivalent, HA-binding peptide bioconjugates with variable valency and tether length which afford the ability to precisely tune the desired binding behavior. The respective binding affinities of the multivalent constructs to HA surface were characterized by quartz crystal microbalance with dissipation monitoring (QCM-D) techniques, and the relationship between dendron structure and binding affinity was revealed. Tetravalent constructs of HA-binding peptides show a 100-fold enhancement in binding affinity compared to HA-binding peptide sequences reported previously. Both biotin and bone morphogenic protein-2 (BMP-2) derivative peptide were successfully linked to the focal point as initial demonstrations. PMID:23931528

Tang, Wen; Ma, Yanrui; Xie, Sibai; Guo, Kai; Katzenmeyer, Bryan; Wesdemiotis, Chrys; Becker, Matthew L

2013-09-01

160

Parameters of protein delivery using hydroxyapatite in simulated body fluid.  

PubMed

Various studies have been conducted using hydroxyapatite (HA) to deliver therapeutic drugs over a long period of time. However, the rate of drug release from ceramics varies tremendously. Thus a study was designed to observe the effect of particle size, pressure, drug ratio, and the addition of a zinc stearate binder on the release of BSA from ceramics. Samples were collected every two hours for a 12 hour period. Three particle sizes were used in the study (< 38, 45-63, and 63-75 microns). Variations in particle size did not influence the release of BSA. Ceramics compressed at a pressure of 150 Mpa delivered more protein than pressures of 300 MPa, 450 MPa, and 900 MPa. Drug to ceramic ratio had the most significant effect. A ratio of 1:25 BSA to HA delivered the protein quickly whereas the 1:100 BSA to HA delivered BSA to HA delivered BSA slowly and in zero order kinetics. The addition of the zinc binder improved the quality of the composite and decreased the release rate of protein delivery when present in 5% or less of the total ceramic weight. HA ceramics can be used to deliver proteins at different rates by varying compression pressure and drug to HA ratio. PMID:9603015

Tscholl, B; Billotte, W G; Reed, D; Smith, S; Kreinbrink, K; Bajpai, P K

1997-01-01

161

Development of electrochemical folic acid sensor based on hydroxyapatite nanoparticles.  

PubMed

We report the synthesis of hydroxyapatite (HA) nanoparticles (NPs) by a simple microwave irradiation method and its application as sensing element for the precise determination of folic acid (FA) by electrochemical method. The structure and composition of the HA NPs characterized using XRD, FTIR, Raman and XPS. SEM and EDX studies confirmed the formation of elongated spherical shaped HA NPs with an average particle size of about 34nm. The HA NPs thin film on glassy carbon electrode (GCE) were deposited by drop casting method. Electrocatalytic behavior of FA in the physiological pH 7.0 was investigated by cyclic voltammetry (CV), linear sweep voltammetry (LSV) and chronoamperometry. The fabricated HA/GCE exhibited a linear calibration plot over a wide FA concentration ranging from 1.0×10(-7) to 3.5×10(-4)M with the detection limit of 75nM. In addition, the HA NPs modified GCE showed good selectivity toward the determination of FA even in the presence of a 100-fold excess of ascorbic acid (AA) and 1000-fold excess of other common interferents. The fabricated biosensor exhibits good sensitivity and stability, and was successfully applied for the determination of FA in pharmaceutical samples. PMID:25194322

Kanchana, P; Sekar, C

2015-02-25

162

Electrophoretic deposition of composite hydroxyapatite-silica-chitosan coatings  

SciTech Connect

Electrophoretic deposition (EPD) method has been developed for the fabrication of nanocomposite silica-chitosan coatings. Cathodic deposits were obtained on various conductive substrates using suspensions of silica nanoparticles in a mixed ethanol-water solvent, containing dissolved chitosan. Co-deposition of silica and hydroxyapatite (HA) nanoparticles resulted in the fabrication of HA-silica-chitosan coatings. The deposition yield has been studied at a constant voltage mode at various deposition durations. The method enabled the formation of coatings of different thickness in the range of up to 100 {mu}m. Deposit composition, microstructure and porosity can be varied by variation of HA and silica concentration in the suspensions. It was demonstrated that EPD can be used for the fabrication of HA-silica-chitosan coatings of graded composition and laminates. The method enabled the deposition of coatings containing layers of silica-chitosan and HA-chitosan nanocomposites using suspensions with different HA and silica content. Obtained coatings were studied by X-ray diffraction, thermogravimetric and differential thermal analysis, scanning electron microscopy and energy dispersive spectroscopy. The mechanism of deposition is discussed.

Grandfield, K. [Department of Materials Science and Engineering, McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4L7 (Canada); Zhitomirsky, I. [Department of Materials Science and Engineering, McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4L7 (Canada)], E-mail: zhitom@mcmaster.ca

2008-01-15

163

CCMR: Characterization of Microsphere Lasers  

NSDL National Science Digital Library

Silica microspheres use total internal reflection to stimulate emission and so there is very little loss and an ultrahigh Q. Because of their size (5-10 ?m in radius, their mode volume is incredibly small, and can thus achieve great optical circulating powers. This combination of high Q and small mode volume is condcive to creating microlasers with ultralow threshold power. Unfortunately, these same characteristics make coupling light incredibly difficult. The modes are quite thin, and with a standard laser’s optical frequency at 1015 and a 109 precision, stabilizing the laser’s frequency to be within the microsphere’s mode is tricky. Furthermore, the microspheres are susceptible to noise and thermal fluctuations Our goal is to build an electronic circuit to stabilize the pump laser’s frequency within such a small range.

Tsai, Tracy

2005-08-17

164

Hydrothermal fabrication of hydroxyapatite on the PEG-grafted surface of wood from Chinese Glossy Privet  

NASA Astrophysics Data System (ADS)

Wood-hydroxyapatite composite material was developed by depositing hydrated calcium hydrogen phosphate (HCHP) on the surface of wood from Chinese Glossy Privet (CGP) with polyethylene glycol (PEG, HO(CH2CH2O)nH) as the grafting agent and subsequent hydrothermal vapor treatment. The results illustrated that HCHP could adhere quickly and strongly on the PEG-grafted wood surface. Moreover, this HCHP could be efficiently transformed to hydroxyapatite (HA, Ca10(PO4)6(OH)2) by hydrothermal vapor treatment. IR, XRD analysis and SEM observation indicated that the fabricated hydroxyapatite was pure and its morphology was uniform and microporous. This work provides a new fabricating approach of biocompatible material which may have some potential applications as bone-repairing material.

Wang, Ning; Cai, Chuanjie; Cai, Dongqing; Cheng, Junjie; Li, Shengli; Wu, Zhengyan

2012-10-01

165

Characterization of Hydroxyapatite-Glass Composites Using Terahertz Time-Domain Spectroscopy  

NASA Astrophysics Data System (ADS)

Terahertz time-domain spectroscopy (THz-TDS) is presented as a tool for characterization of the hydroxyapatite (HA)-glass composites. The materials under investigation are composites of HA and a calcium zinc silicate glass. Our results show that the refractive index and dielectric constant in THz frequencies provide a reliable determination of glass content of these composites. In addition, the THz-TDS is used to morphological changes in HA during simulated body fluid (SBF) incubation. Our results demonstrate that the THz-TDS can be a promising non-destructive tool.

Yatongchai, C.; Wren, A. W.; Sundaram, S. K.

2015-01-01

166

Characterization of Hydroxyapatite-Glass Composites Using Terahertz Time-Domain Spectroscopy  

NASA Astrophysics Data System (ADS)

Terahertz time-domain spectroscopy (THz-TDS) is presented as a tool for characterization of the hydroxyapatite (HA)-glass composites. The materials under investigation are composites of HA and a calcium zinc silicate glass. Our results show that the refractive index and dielectric constant in THz frequencies provide a reliable determination of glass content of these composites. In addition, the THz-TDS is used to morphological changes in HA during simulated body fluid (SBF) incubation. Our results demonstrate that the THz-TDS can be a promising non-destructive tool.

Yatongchai, C.; Wren, A. W.; Sundaram, S. K.

2014-08-01

167

Modulating protein adsorption onto hydroxyapatite particles using different amino acid treatments.  

PubMed

Hydroxyapatite (HA) is a material of choice for bone grafts owing to its chemical and structural similarities to the mineral phase of hard tissues. The combination of osteogenic proteins with HA materials that carry and deliver the proteins to the bone-defective areas will accelerate bone regeneration. The study investigated the treatment of HA particles with different amino acids such as serine (Ser), asparagine (Asn), aspartic acid (Asp) and arginine (Arg) to enhance the adsorption ability of HA carrier for delivering therapeutic proteins to the body. The crystallinity of HA reduced when amino acids were added during HA preparation. Depending on the types of amino acid, the specific surface area of the amino acid-functionalized HA particles varied from 105 to 149 m(2) g(-1). Bovine serum albumin (BSA) and lysozyme were used as model proteins for adsorption study. The protein adsorption onto the surface of amino acid-functionalized HA depended on the polarities of HA particles, whereby, compared with lysozyme, BSA demonstrated higher affinity towards positively charged Arg-HA. Alternatively, the binding affinity of lysozyme onto the negatively charged Asp-HA was higher when compared with BSA. The BSA and lysozyme adsorptions onto the amino acid-functionalized HA fitted better into the Freundlich than Langmuir model. The amino acid-functionalized HA particles that had higher protein adsorption demonstrated a lower protein-release rate. PMID:21957116

Lee, Wing-Hin; Loo, Ching-Yee; Van, Kim Linh; Zavgorodniy, Alexander V; Rohanizadeh, Ramin

2012-05-01

168

Glass microsphere lubrication  

NASA Technical Reports Server (NTRS)

The harsh lunar environment eliminated the consideration of most lubricants used on earth. Considering that the majority of the surface of the moon consists of sand, the elements that make up this mixture were analyzed. According to previous space missions, a large portion of the moon's surface is made up of fine grained crystalline rock, about 0.02 to 0.05 mm in size. These fine grained particles can be divided into four groups: lunar rock fragments, glasses, agglutinates (rock particles, crystals, or glasses), and fragments of meteorite material (rare). Analysis of the soil obtained from the missions has given chemical compositions of its materials. It is about 53 to 63 percent oxygen, 16 to 22 percent silicon, 10 to 16 percent sulfur, 5 to 9 percent aluminum, and has lesser amounts of magnesium, carbon, and sodium. To be self-supporting, the lubricant must utilize one or more of the above elements. Considering that the element must be easy to extract and readily manipulated, silicon or glass was the most logical choice. Being a ceramic, glass has a high strength and excellent resistance to temperature. The glass would also not contaminate the environment as it comes directly from it. If sand entered a bearing lubricated with grease, the lubricant would eventually fail and the shaft would bind, causing damage to the system. In a bearing lubricated with a solid glass lubricant, sand would be ground up and have little effect on the system. The next issue was what shape to form the glass in. Solid glass spheres was the only logical choice. The strength of the glass and its endurance would be optimal in this form. To behave as an effective lubricant, the diameter of the spheres would have to be very small, on the order of hundreds of microns or less. This would allow smaller clearances between the bearing and the shaft, and less material would be needed. The production of glass microspheres was divided into two parts, production and sorting. Production includes the manufacturing of the microspheres, while sorting entails deciphering the good microspheres from the bad ones. Each process is discussed in detail.

Geiger, Michelle; Goode, Henry; Ohanlon, Sean; Pieloch, Stuart; Sorrells, Cindy; Willette, Chris

1991-01-01

169

Support for the initial attachment, growth and differentiation of MG-63 cells: a comparison between nano-size hydroxyapatite and micro-size hydroxyapatite in composites  

PubMed Central

Hydroxyapatite (HA) is considered to be a bioactive material that favorably influences the adhesion, growth, and osteogenic differentiation of osteoblasts. To optimize the cell response on the hydroxyapatite composite, it is desirable to assess the optimum concentration and also the optimum particle size. The aim of our study was to prepare composite materials made of polydimethylsiloxane, polyamide, and nano-sized (N) or micro-sized (M) HA, with an HA content of 0%, 2%, 5%, 10%, 15%, 20%, 25% (v/v) (referred to as N0–N25 or M0–M25), and to evaluate them in vitro in cultures with human osteoblast-like MG-63 cells. For clinical applications, fast osseointegration of the implant into the bone is essential. We observed the greatest initial cell adhesion on composites M10 and N5. Nano-sized HA supported cell growth, especially during the first 3 days of culture. On composites with micro-size HA (2%–15%), MG-63 cells reached the highest densities on day 7. Samples M20 and M25, however, were toxic for MG-63 cells, although these composites supported the production of osteocalcin in these cells. On N2, a higher concentration of osteopontin was found in MG-63 cells. For biomedical applications, the concentration range of 5%–15% (v/v) nano-size or micro-size HA seems to be optimum. PMID:25125978

Filová, Elena; Suchý, Tomáš; Sucharda, Zbyn?k; Šupová, Monika; Žaloudková, Margit; Balík, Karel; Lisá, V?ra; Šlouf, Miroslav; Ba?áková, Lucie

2014-01-01

170

Support for the initial attachment, growth and differentiation of MG-63 cells: a comparison between nano-size hydroxyapatite and micro-size hydroxyapatite in composites.  

PubMed

Hydroxyapatite (HA) is considered to be a bioactive material that favorably influences the adhesion, growth, and osteogenic differentiation of osteoblasts. To optimize the cell response on the hydroxyapatite composite, it is desirable to assess the optimum concentration and also the optimum particle size. The aim of our study was to prepare composite materials made of polydimethylsiloxane, polyamide, and nano-sized (N) or micro-sized (M) HA, with an HA content of 0%, 2%, 5%, 10%, 15%, 20%, 25% (v/v) (referred to as N0-N25 or M0-M25), and to evaluate them in vitro in cultures with human osteoblast-like MG-63 cells. For clinical applications, fast osseointegration of the implant into the bone is essential. We observed the greatest initial cell adhesion on composites M10 and N5. Nano-sized HA supported cell growth, especially during the first 3 days of culture. On composites with micro-size HA (2%-15%), MG-63 cells reached the highest densities on day 7. Samples M20 and M25, however, were toxic for MG-63 cells, although these composites supported the production of osteocalcin in these cells. On N2, a higher concentration of osteopontin was found in MG-63 cells. For biomedical applications, the concentration range of 5%-15% (v/v) nano-size or micro-size HA seems to be optimum. PMID:25125978

Filová, Elena; Suchý, Tomáš; Sucharda, Zbyn?k; Supová, Monika; Zaloudková, Margit; Balík, Karel; Lisá, V?ra; Slouf, Miroslav; Ba?áková, Lucie

2014-01-01

171

Hydroxyapatite coating of cellulose sponges attracts bone-marrow-derived stem cells in rat subcutaneous tissue  

PubMed Central

The presence of bone-marrow-derived stem cells was investigated in a wound-healing model where subcutaneously implanted cellulose sponges were used to induce granulation tissue formation. When cellulose was coated with hydroxyapatite (HA), the sponges attracted circulating haemopoietic and mesenchymal progenitor cells more efficiently than uncoated cellulose. We hypothesized that the giant cells/macrophages of HA-coated sponges recognize HA as foreign material, phagocyte or hydrolyse it and release calcium ions, which are recognized by the calcium-sensing receptors (CaRs) expressed on many cells including haemopoietic progenitors. Our results showed, indeed, that the HA-coated sponges contained more CaR-positive cells than untreated sponges. The stem cells are, most probably, responsible for the richly vascularized granulation tissue formed in HA-coated sponges. This cell-guiding property of HA-coated cellulose might be useful in clinical situations involving impaired wound repair. PMID:19324666

Tommila, Miretta; Jokilammi, Anne; Terho, Perttu; Wilson, Timothy; Penttinen, Risto; Ekholm, Erika

2009-01-01

172

Synthesis of silver-incorporated hydroxyapatite nanocomposites for antimicrobial implant coatings  

NASA Astrophysics Data System (ADS)

Because of excellent osteoconductivity and resorbability, hydroxyapatite (HA) is commonly used as a bone substitute material or implant coating. Both ionic and metallic silver are considered to have a broad spectrum of antimicrobial properties especially associated with biomaterial-related infections. The present work proposes a facile chemical reduction method to synthesize an Ag incorporated HA nanocomposite. Ammoniacal silver solution was firstly prepared and then added into the HA solution, followed by hydrazine hydrate (N2H4·H2O) being used to reduce the silver ions to metallic silver. The formed Ag nanoparticles had diameters of 20-30 nm and were firmly attached on the HA particle surfaces. This approach can also keep the integrity of the HA chemical structure and the morphology. The strain Escherichia coli was used to evaluate the antibacterial effect of the nanocomposite. An In vitro bacterial adhesion study indicated a significant enhancement in the antibacterial property of silver containing HA.

Liu, Xiangmei; Mou, Yanan; Wu, Shuilin; Man, H. C.

2013-05-01

173

Effect of filler surface morphology on the impact behaviour of hydroxyapatite reinforced high density polyethylene composites.  

PubMed

Instrumented falling weight impact tests have been carried out to characterize the impact behaviour of hydroxyapatite reinforced high-density polyethylene composite (HA-HDPE) in order to use this biomaterial in skull implants. The effects of HA filler surface morphology and volume fraction on the fracture toughness were studied, and fracture mechanism investigated. Impact resistance was found to be markedly improved by using a sintered grade HA filler with smooth particle surface instead of spray dried grade HA with rough surface. SEM examination of impacted fracture surfaces revealed that the improvement of impact resistance was due to the stronger interfacial bonding between smooth HA particles and HDPE polymer matrix compared with that between rough HA and HDPE, which results in more energy absorption during impact and hence better fracture resistance. PMID:17619972

Zhang, Y; Tanner, K E

2008-02-01

174

Materials processing and in-vivo animal studies of nitrided hydroxyapatite bioceramics  

NASA Astrophysics Data System (ADS)

Calcium phosphate bioceramics are currently being used in medicine and dentistry, for reconstruction or repair of diseased or injured bone, but with limited success. Incorporating nitrogen into phosphate glasses has resulted in improved properties, and it is proposed that similar benefits may be gained from nitriding calcium phosphate bioceramics for bone implants as well. This work focuses on processing of hydroxyapatite and tricalcium phosphate bioceramics nitrided by using solid, liquid, gas and ion sources. These materials were characterized by chemical, structural, mechanical, and biological methods to determine both the material structure and their suitability as implant materials. Calcium nitride and NaPON glass were unsatisfactory sources of nitrogen for hydroxyapatite (HA) and/or tricalcium phosphate (TCP) ceramics. Calcium nitride, Ca3N2, is reacts with water vapor in the air, releasing ammonia, and leaving behind crystals of calcium oxide, CaO. The calcium oxide byproduct decreases the chemical stability of hydroxyapatite and HA/TCP composites in simulated body fluid. Sodium phosphorus oxynitride (NaPON) glass, in the form of a liquid sintering aid for HA, produces an inhomogeneous, composite as well. Hydroxyapatite heated at 800C in an ammonia atmosphere produces a homogeneous material with up to 2 wt% N. Infrared spectroscopy indicates cyanamide ions, CN22-, are formed by the incorporated nitrogen and impurity carbon. The use of 15N-doped ammonia results in an 15N NMR peak at 83.2 ppm, indicating P--N bonding. Raman spectroscopy may also indicate P--N bonding, but it is inconclusive. In a limited study, nitrogen may decrease the hardness and fracture toughness of the phosphate ceramic, hydroxyapatite, contrary to results expected for nitrogen in phosphate glasses. Nitrogen ions are incorporated in hydroxyapatite by ion implantation, with lower energies producing higher nitrogen contents. The highest concentration achieved was 3.55 wt% N, as determined by electron microprobe analysis. Both ammonia-nitrided samples and ion-implanted samples were used as substrates for bone morphogenetic proteins (BMPs) in biological studies. Nitrided hydroxyapatite samples with BMPs showed an increase in bone formation when surgically implanted in rats. Furthermore, the bone formation increased with increasing nitrogen. On the other hand, bone formation decreased with increasing nitrogen for nitrided HA samples without BMPs.

Rashid, Nancy Elizabeth

2000-10-01

175

Synthesis and characterization of hydroxyapatite nanofiber by chemical precipitation method using surfactants  

SciTech Connect

Highlights: ? We succeeded in synthesizing hydroxyapatite nano fibers by a chemical method. ? The reaction temperature is only 90 °C. ? The synthetic hydroxyapatite nano fiber is single crystal. - Abstract: We report a novel chemical precipitation route for the synthesis of hydroxyapatite (Ca{sub 10}(PO{sub 4}){sub 6}(OH){sub 2}, HA) fibers using surfactants as templates. Fourier transform infrared spectroscopy (FTIR) and powder X-ray diffraction (PXRD) reveal the characteristic peaks of HA. Transmission electron microscope (TEM) and high-resolution TEM revealed the nano structure, crystallinity and morphology of the HA fibers. The morphology of the HA fibers after calcinations were characterized by scanning electron microscope (SEM). Br{sup ?} ions were quickly replaced by the excess PO{sub 4}{sup 3?} ions in the solution after the addition of cetyltrime-thylammonium bromide (CTAB). Meanwhile, CTAB formed a rod-like micelles. Precursors reacted with PO{sub 4}{sup 3?} at the surface of CTAB micelles and finally formed the nanofiber structure.

Gao, Shan, E-mail: coralgao@hotmail.com [Key Laboratory for Liquid-Solid Structure Evolution and Processing of Materials (Ministry of Education), Shandong University, Jinan 250061 (China); Engineering Ceramics Key Laboratory of Shandong Province, Shandong University, Jinan 250061 (China); Sun, Kangning, E-mail: sunkangning@sdu.edu.cn [Key Laboratory for Liquid-Solid Structure Evolution and Processing of Materials (Ministry of Education), Shandong University, Jinan 250061 (China); Engineering Ceramics Key Laboratory of Shandong Province, Shandong University, Jinan 250061 (China); Li, Aimin; Wang, Hongyou [Key Laboratory for Liquid-Solid Structure Evolution and Processing of Materials (Ministry of Education), Shandong University, Jinan 250061 (China); Engineering Ceramics Key Laboratory of Shandong Province, Shandong University, Jinan 250061 (China)

2013-03-15

176

Keratin-hydroxyapatite composites: biocompatibility, osseointegration, and physical properties in an ovine model.  

PubMed

Reconstituted keratin has shown promise as an orthopaedic biomaterial. This in vivo study investigates the biological response of composite materials prepared from reconstituted keratin containing a high content of hydroxyapatite (HA) (40 wt % HA), implanted for up to 18 weeks in the long bones of sheep. Keratin-HA composites were compared with a commercially available polylactic acid (PLA) HA composite (BIO RCI HA®, Smith and Nephew). Porous keratin-HA materials displayed excellent biocompatibility and osseointegration, with full integration into bone by 12 weeks. Dense keratin-HA materials also showed excellent biocompatibility, with a more limited osseointegration, involving the penetration of new bone into the periphery of the implant after eight weeks. In contrast, the PLA-HA implant did not integrate with surrounding tissue. Microindentation showed that porous keratin-HA implants were initially soft, but became stiffer as new bone penetrated the implant from four weeks onwards. In contrast, although the initial rigidity of dense keratin-HA composites was maintained for at least two weeks, the implant material weakened after four weeks. The PLA-HA implant maintained its physical properties throughout the course of the trial. This study demonstrates the increased osseointegration/osteoconduction capacity of keratin-HA composites and provides further evidence supporting the suitability of keratin-based materials, such as bone graft substitutes and soft tissue fixation devices. PMID:20878901

Dias, George J; Mahoney, Patricia; Swain, Michael; Kelly, Robert J; Smith, Robert A; Ali, Mohammad A

2010-12-15

177

Fabrication of glass microspheres with conducting surfaces  

DOEpatents

A method for making hollow glass microspheres with conducting surfaces by adding a conducting vapor to a region of the glass fabrication furnace. As droplets or particles of glass forming material pass through multiple zones of different temperature in a glass fabrication furnace, and are transformed into hollow glass microspheres, the microspheres pass through a region of conducting vapor, forming a conducting coating on the surface of the microspheres.

Elsholz, William E. (Acampo, CA)

1984-01-01

178

Fabrication of glass microspheres with conducting surfaces  

DOEpatents

A method for making hollow glass microspheres with conducting surfaces by adding a conducting vapor to a region of the glass fabrication furnace. As droplets or particles of glass forming material pass through multiple zones of different temperature in a glass fabrication furnace, and are transformed into hollow glass microspheres, the microspheres pass through a region of conducting vapor, forming a conducting coating on the surface of the microspheres.

Elsholz, W.E.

1982-09-30

179

Accurate characterization of pure silicon-substituted hydroxyapatite powders1 synthesized by a new precipitation route2  

E-print Network

material in the field of bioactive bone substitutes and bone tissue engineering. It is now well-51 in bone repair. The SiHA58 structure corresponds to the substitution of phosphate ions (PO4 31 Accurate characterization of pure silicon-substituted hydroxyapatite powders1 synthesized

180

A new hydroxyapatite-based biocomposite for bone replacement.  

PubMed

Since the 1970s, various types of ceramic, glass and glass-ceramic materials have been proposed and used to replace damaged bone in many clinical applications. Among them, hydroxyapatite (HA) has been successfully employed thanks to its excellent biocompatibility. On the other hand, the bioactivity of HA and its reactivity with bone can be improved through the addition of proper amounts of bioactive glasses, thus obtaining HA-based composites. Unfortunately, high temperature treatments (1200°C÷1300°C) are usually required in order to sinter these systems, causing the bioactive glass to crystallize into a glass-ceramic and hence inhibiting the bioactivity of the resulting composite. In the present study novel HA-based composites are realized and discussed. The samples can be sintered at a relatively low temperature (800 °C), thanks to the employment of a new glass (BG_Ca) with a reduced tendency to crystallize compared to the widely used 45S5 Bioglass®. The rich glassy phase, which can be preserved during the thermal treatment, has excellent effects in terms of in vitro bioactivity; moreover, compared to composites based on 45S5 Bioglass® having the same HA/glass proportions, the samples based on BG_Ca displayed an earlier response in terms of cell proliferation. PMID:23827547

Bellucci, Devis; Sola, Antonella; Gazzarri, Matteo; Chiellini, Federica; Cannillo, Valeria

2013-04-01

181

RESEARCH/RESEARCHERS Microspheres Function as  

E-print Network

RESEARCH/RESEARCHERS Microspheres Function as Microlenses for Projection Photolithography Arrays transparent polystyrene microspheres as microlenses. George M. Whitesides and Ming-Hsien Wu, both of Harvard starting from a pattern on a transparency with millimeter-size features. Polystyrene microspheres (with

182

Mechanisms of uranium interactions with hydroxyapatite: Implications for groundwater remediation  

USGS Publications Warehouse

The speciation of U(VI) sorbed to synthetic hydroxyapatite was investigated using a combination of U LIII-edge XAS, synchrotron XRD, batch uptake measurements, and SEM-EDS. The mechanisms of U(VI) removal by apatite were determined in order to evaluate the feasibility of apatitebased in-situ permeable reactive barriers (PRBs). In batch U(VI) uptake experiments with synthetic hydroxyapatite (HA), near complete removal of dissolved uranium (>99.5%) to <0.05 ??M was observed over a range of total U(VI) concentrations up to equimolar of the total P in the suspension. XRD and XAS analyses of U(VI)-reacted HA at sorbed concentrations ???4700 ppm U(VI) suggested that uranium(VI) phosphate, hydroxide, and carbonate solids were not present at these concentrations. Fits to EXAFS spectra indicate the presence of Ca neighbors at 3.81 A??. U-Ca separation, suggesting that U(VI) adsorbs to the HA surfaces as an inner-sphere complex. Uranium(VI) phosphate solid phases were not detected in HA with 4700 ppm sorbed U(VI) by backscatter SEM or EDS, in agreement with the surface complexation process. In contrast, U(VI) speciation in samples that exceeded 7000 ppm sorbed U(VI) included a crystalline uranium(VI) phosphate solid phase, identified as chernikovite by XRD. At these higher concentrations, a secondary, uranium(VI) phosphate solid was detected by SEM-EDS, consistent with chernikovite precipitation. Autunite formation occurred at total U:P molar ratios ???0.2. Our findings provide a basis for evaluating U(VI) sorption mechanisms by commercially available natural apatites for use in development of PRBs for groundwater U(VI) remediation.

Fuller, C.C.; Bargar, J.R.; Davis, J.A.; Piana, M.J.

2002-01-01

183

Development of wear resistant NFSS-HA novel biocomposites and study of their tribological properties for orthopaedic applications.  

PubMed

Implants made of nickel free austenitic stainless steel can reduce the toxic effect of released nickel ion and compounds from the conventional stainless steels. On the other hand, hydroxyapatite is a ceramic which has been used in orthopaedic applications due to its good osteoconductivity, biocompatibility and bioactivity. However, there is no evidence in the literature up to now on producing composites based on nickel free stainless steel and hydroxyapatite and study of their tribology. The aim of this work was to produce novel biocomposites made up of nickel free stainless steel with hydroxyapatite (prepared by heat treating bone ash) and studying their tribology under various loads in air and in Ringer's physiological solution. Different amounts of hydroxyapatite powder (10, 20, 30 and 40% Vol.) were added to this nickel free stainless steel powder to get the biocomposites. Variation of their density, hardness, wear resistance and friction with the ceramic (hydroxyapatite) content and wear load were investigated in air and in Ringer's solution. The density of the composites was decreased by increasing the volume percentage of the hydroxyapatite, while wear resistance of the composites was increased. The wear mechanism of these composites was changed by increasing the wear load and consequently the volume loss was enhanced dramatically. Furthermore, by increasing the sliding distance, the rate of volume loss was decreased slightly. The friction coefficient of the composites was also decreased by increasing the weight percentage of hydroxyapatite. Effect of the physiological Ringer's solution on wear resistance and friction coefficient of the composites was nearly negligible. The wear mechanisms of the samples were identified by studying the SEM images of the worn surfaces of the tested samples in different wear loads and HA contents. PMID:20129417

Younesi, M; Bahrololoom, M E; Fooladfar, H

2010-02-01

184

Effects of Water Location in Starting Materials on Bonding Behavior of Hydroxyapatite and Titanium via Hydrothermal Hot-pressing  

Microsoft Academic Search

Solidification of hydroxyapatite (HA:Ca10(PO4)6(OH)2) and its bonding with titanium (Ti) was achieved simultaneously by using the hydrothermal hot-pressing method at temperatures as low as 150° C with no special surface treatment of Ti. A mixture of calcium hydrogen phosphate dihydrate and calcium hydroxide was used as the starting powder material for solidifying HA. Three point bending tests were conducted to

Takamasa Onoki; Kazuyuki Hosoi; Toshiyuki Hashida

2006-01-01

185

Biological and physical properties of pulsed-Laser-deposited zirconia\\/hydroxyapatite on titanium: In vitro study  

Microsoft Academic Search

Coating dental implants with hydroxyapatite (HA) may give certain advantages such as active encouragement of new bone growth,\\u000a a lower rejection rate, and an improved long-term prosthesis fixation. This study examined the mechanical and biological properties\\u000a of titanium alloy implant cores with an interlayer of zirconia and a coating of HA created using pulsed Laser deposition (PLD).\\u000a The thickness of

Z. Teuberova; M. Seydlova; T. Dostalova; B. Dvorankova; K. Smetana Jr.; M. Jelinek; P. Masinova; T. Kocourek; K. Kolarova; J. Wilson

2007-01-01

186

Affinity of the Interface between Hydroxyapatite (0001) and Titanium (0001) Surfaces: A First-Principles Investigation.  

PubMed

A basic understanding of the affinity between the hydroxyapatite (HA) and ?-Ti surfaces is obtained through electronic structure calculations by first-principles method. The surface energies of HA(0001), HA (011?0), HA (101?1), and Ti(0001) surfaces have been calculated. The HA(0001) presents the most thermodynamically stable of HA. The HA/Ti interfaces were constructed by two kinds of interface models, the single interface (denoted as SI) and the double-interface (denoted as DI). Two methods, the full relaxation and the UBER, were applied to determine the interfacial separation and the atomic arrangement in the interfacial zone. The works of adhesion of interfaces with various stoichiometric HA surfaces were evaluated. For the HA(0001)/Ti(0001) interfaces, the work of adhesion is strongly dependent on the chemical environment of the HA surface. The values are -2.33, -1.52, and -0.80 J/m(2) for the none-, single-, and double-Ca terminated HA/Ti interfaces, respectively. The influence of atomic relaxation on the work of adhesion and interface separation is discussed. Full relaxation results include -1.99 J/m(2) work of adhesion and 0.220 nm separation between HA and Ti for the DI of 1-Ca-HA/Ti interface, while they are -1.14 J/m(2) and 0.235 nm by partial relaxation. Analysis of electronic structure reveals that charge transfer between HA and Ti slabs occurs during the formation of the HA/Ti interface. The transfer generates the Ti-O or Ti-Ca bonds across the interface and drives the HA/Ti interface system to metallic characteristic. The energetically favorable interfaces are formed when the outmost layer of HA comprises more O atoms at the interface. PMID:25390283

Sun, Jin P; Dai, Jianhong; Song, Yan; Wang, You; Yang, Rui

2014-12-10

187

Modeling the Formation of Polyimide Microspheres  

NASA Technical Reports Server (NTRS)

High temperature polyimide microspheres have been developed from polyimide solid residuum by a simple inflation process. Microspheres have been fabricated from several polyimide precursors through the use of a circulating air oven. Microsphere formation and final physical property characterization have been limited to simple mechanical and thermal testing. The present paper focuses on developing an understanding of microsphere formation through simple geometric rules for an incompressible polymeric material and microscopic observations of precursor residuum inflation. Inflation kinematics of the hollow polyimide microspheres as a function of time and temperature is discussed.

Pipes, R. B.; Weiser, E. S.; Gonsoulin, B.; Hubert, P.

2002-01-01

188

Characterization of Multiwalled Carbon Nanotube-Reinforced Hydroxyapatite Composites Consolidated by Spark Plasma Sintering  

PubMed Central

Pure HA and 1, 3, 5, and 10?vol% multiwalled carbon nanotube- (MWNT-) reinforced hydroxyapatite (HA) were consolidated using a spark plasma sintering (SPS) technique. The relative density of pure HA increased with increasing sintering temperature, but that of the MWNT/HA composite reached almost full density at 900°C, and then decreased with further increases in sintering temperature. The relative density of the MWNT/HA composites increased with increasing MWNT content due to the excellent thermal conductivity of MWNTs. The grain size of MWNT/HA composites decreased with increasing MWNT content and increased with increasing sintering temperature. Pull-out toughening of the MWNTs of the MWNT/HA composites was observed in the fractured surface, which can be used to predict the improvement of the mechanical properties. On the other hand, the existence of undispersed or agglomerate MWNTs in the MWNT/HA composites accompanied large pores. The formation of large pores increased with increasing sintering temperature and MWNT content. The addition of MWNT in HA increased the hardness and fracture toughness by approximately 3~4 times, despite the presence of large pores produced by un-dispersed MWNTs. This provides strong evidence as to why the MWNTs are good candidates as reinforcements for strengthening the ceramic matrix. The MWNT/HA composites did not decompose during SPS sintering. The MWNT-reinforced HA composites were non-toxic and showed a good cell affinity and morphology in vitro for 1 day. PMID:24724100

Kim, Duk-Yeon; Han, Young-Hwan; Lee, Jun Hee; Kang, Inn-Kyu; Jang, Byung-Koog; Kim, Sukyoung

2014-01-01

189

Characterization of multiwalled carbon nanotube-reinforced hydroxyapatite composites consolidated by spark plasma sintering.  

PubMed

Pure HA and 1, 3, 5, and 10?vol% multiwalled carbon nanotube- (MWNT-) reinforced hydroxyapatite (HA) were consolidated using a spark plasma sintering (SPS) technique. The relative density of pure HA increased with increasing sintering temperature, but that of the MWNT/HA composite reached almost full density at 900°C, and then decreased with further increases in sintering temperature. The relative density of the MWNT/HA composites increased with increasing MWNT content due to the excellent thermal conductivity of MWNTs. The grain size of MWNT/HA composites decreased with increasing MWNT content and increased with increasing sintering temperature. Pull-out toughening of the MWNTs of the MWNT/HA composites was observed in the fractured surface, which can be used to predict the improvement of the mechanical properties. On the other hand, the existence of undispersed or agglomerate MWNTs in the MWNT/HA composites accompanied large pores. The formation of large pores increased with increasing sintering temperature and MWNT content. The addition of MWNT in HA increased the hardness and fracture toughness by approximately 3~4 times, despite the presence of large pores produced by un-dispersed MWNTs. This provides strong evidence as to why the MWNTs are good candidates as reinforcements for strengthening the ceramic matrix. The MWNT/HA composites did not decompose during SPS sintering. The MWNT-reinforced HA composites were non-toxic and showed a good cell affinity and morphology in vitro for 1 day. PMID:24724100

Kim, Duk-Yeon; Han, Young-Hwan; Lee, Jun Hee; Kang, Inn-Kyu; Jang, Byung-Koog; Kim, Sukyoung

2014-01-01

190

Size controlled hydroxyapatite and calcium carbonate particles: synthesis and their application as templates for SERS platform.  

PubMed

An elegant route for hydroxyapatite (HA) particle synthesis via ionic exchange reaction is reported. Calcium carbonate particles (CaCO3) were recrystallized into HA beads in water solution with phosphate ions. The size of initial CaCO3 particles was controlled upon the synthesis by varying the amount of ethylene glycol (EG) in aqueous solution. The average size of HA beads ranged from 0.6±0.1 to 4.3±1.1?m. Silver nanoparticles were deposited on the surface of HA and CaCO3 particles via silver mirror reaction. Surface enhanced Raman scattering of silver functionalized beads was demonstrated by detecting Rhodamine B. CaCO3 and HA particles have a great potential for design of carrier which can provide diagnostic and therapeutic functions. PMID:24802965

Parakhonskiy, B V; Svenskaya, Yu I; Yashchenok, A ?; Fattah, H A; Inozemtseva, O A; Tessarolo, F; Antolini, R; Gorin, D A

2014-06-01

191

Electrospun polyvinyl alcohol-collagen-hydroxyapatite nanofibers: a biomimetic extracellular matrix for osteoblastic cells  

NASA Astrophysics Data System (ADS)

The failure of prosthesis after total joint replacement is due to the lack of early implant osseointegration. In this study polyvinyl alcohol-collagen-hydroxyapatite (PVA-Col-HA) electrospun nanofibrous meshes were fabricated as a biomimetic bone-like extracellular matrix for the modification of orthopedic prosthetic surfaces. In order to reinforce the PVA nanofibers, HA nanorods and Type I collagen were incorporated into the nanofibers. We investigated the morphology, biodegradability, mechanical properties and biocompatibility of the prepared nanofibers. Our results showed these inorganic-organic blended nanofibers to be degradable in vitro. The encapsulated nano-HA and collagen interacted with the PVA content, reinforcing the hydrolytic resistance and mechanical properties of nanofibers that provided longer lasting stability. The encapsulated nano-HA and collagen also enhanced the adhesion and proliferation of murine bone cells (MC3T3) in vitro. We propose the PVA-Col-HA nanofibers might be promising modifying materials on implant surfaces for orthopedic applications.

Song, Wei; Markel, David C.; Wang, Sunxi; Shi, Tong; Mao, Guangzhao; Ren, Weiping

2012-03-01

192

Fabrication of 3D chitosan–hydroxyapatite scaffolds using a robotic dispensing system  

Microsoft Academic Search

A new robotic desktop rapid prototyping (RP) system was designed to fabricate scaffolds for tissue engineering applications. The experimental setup consists of a computer-guided desktop robot and a one-component pneumatic dispenser. The dispensing material (chitosan and chitosan–hydroxyapatite (HA) dissolved in acetic acid) was stored in a 30-ml barrel and forced out through a small Teflon-lined nozzle into a dispensing medium

T. H Ang; F. S. A Sultana; D. W Hutmacher; Y. S Wong; J. Y. H Fuh; X. M Mo; H. T Loh; E Burdet; S. H Teoh

2002-01-01

193

Effect of strontium-containing hydroxyapatite bone cement on bone remodeling following hip replacement  

Microsoft Academic Search

It is uncertain whether the use of bioactive bone cement has any beneficial effect on local bone adaptation following hip\\u000a replacement. In this study, twelve goats underwent cemented hip hemiarthroplasty unilaterally, with either PMMA bone cement\\u000a or strontium-containing hydroxyapatite (Sr-HA) bioactive bone cement. Nine months later, the femoral cortical bones at different\\u000a levels were analyzed by microhardness testing and micro-CT

Guo X. Ni; Jian H. Lin; Peter K. Y. Chiu; Zhao Y. Li; William W. Lu

2010-01-01

194

Hydroxyapatite-glass composite as a bone substitute in large metaphyseal cavities in rabbits  

Microsoft Academic Search

This study evaluated hydroxyapatite-glass (HA-G) composite as a filler material when implanted into a proximal metaphyseal tibial cavity consisting of medullary tissue and cancellous bone in rabbits. The repair process was compared with that of autogenous bone grafts and untreated controls. Scanning electron microscopy, energy dispersive x-ray studies, radiography, histology with tetracycline fluorescence and morphometric bone measurements were used for

E. A. Suominen; A. J. Aho; J. Juhanoja; A. Yli-Urpo

1995-01-01

195

The deposition of strontium-substituted hydroxyapatite coatings.  

PubMed

Strontium substituted hydroxyapatite (SrHA) coatings have received a lot of interest recently as strontium (Sr) has been shown to have the dual benefit of promoting bone formation and reducing bone resorption, in vivo. In this work, SrHA coatings were deposited onto polycrystalline titanium surfaces using radio frequency (RF) magnetron co-sputtering and compared to those deposited from HA alone. In particular, the influence of different levels of Sr-substitution of the sputtering targets (5 and 13 % Sr-substituted HA targets) on the properties of the deposited coatings produced at a low discharge power level (150 W) were investigated using FTIR, XPS, XRD, ToFSIMS and AFM techniques (both before and after annealing at 500 °C). The results show that Sr could be successfully incorporated into the HA lattice to form SrHA coatings and that they contained no other impurities. However, the coating produced from the 13 % Sr-substituted target had a higher Ca + Sr/P ratio (1.95 ± 0.14) and Sr content when compared to the coating produced from the 5 % Sr-substituted target (1.58 ± 0.20). The deposition rate also decreased with increasing Sr content of the sputtering targets. Furthermore, as the Sr content of the coatings increased, so did the preferred 002 orientation of the coating along with increased surface roughness and heterogeneity of the surface features. Therefore, this study has shown that RF magnetron sputtering offers a means to control attendant properties of Sr-substituted HA, such as the crystallinity, stoichiometry, phase purity and surface topography. PMID:25631262

Boyd, Adrian R; Rutledge, L; Randolph, L D; Mutreja, I; Meenan, B J

2015-02-01

196

The Enamel Protein Amelotin is a Promoter of Hydroxyapatite Mineralization.  

PubMed

Amelotin (AMTN) is a recently discovered protein that is specifically expressed during the maturation stage of dental enamel formation. It is localized at the interface between the enamel surface and the apical surface of ameloblasts. AMTN knock-out mice have hypomineralized enamel whereas transgenic mice overexpressing AMTN have a compact but disorganized enamel hydroxyapatite (HA) microstructure indicating a possible involvement of AMTN in regulating HA mineralization directly. In this study we demonstrated that recombinant human (rh) AMTN dissolved in a metastable buffer system, based on light scattering measurements, promotes HA precipitation. The mineral precipitates were characterized by scanning and transmission electron microscopy and electron diffraction. Colloidal gold immunolabeling of AMTN in the mineral deposits showed that protein molecules were associated with HA crystals. The binding affinity of rh-AMTN to HA was found to be comparable to that of amelogenin, the major protein of the forming enamel matrix. Overexpression of AMTN in mouse calvaria cells also increased the formation of calcium deposits in the culture medium. Overexpression of AMTN during the secretory stage of enamel formation in vivo resulted in rapid and uncontrolled enamel mineralization. Site-specific mutagenesis of the potential serine phosphorylation motif SSEEL reduced the in vitro mineral precipitation to less than 25%, revealing that this motif is important for the HA mineralizing function of the protein. A synthetic short peptide containing the SSEEL motif was only able to facilitate mineralization in its phosphorylated form ((P) S(P) SEEL), indicating that this motif is necessary, but not sufficient for the mineralizing properties of AMTN. These findings demonstrate that AMTN has a direct influence on biomineralization by promoting HA mineralization and suggest a critical role for AMTN in the formation of the compact aprismatic enamel surface layer during the maturation stage of amelogenesis. This article is protected by copyright. All rights reserved. PMID:25407797

Abbarin, Nastaran; Miguel, Symone San; Holcroft, James; Iwasaki, Kengo; Ganss, Bernhard

2014-11-18

197

Electrochemical synthesis of nanosized hydroxyapatite by pulsed direct current method  

SciTech Connect

Synthesis of nanosized of hydroxyapatite (HA) by electrochemical pulsed direct current (PDC) method has been studied. The aim of this work is to study the influence of various PDC parameters (pH initial, electrode distance, duty cycle, frequency, and amplitude) on particle surface area of HA powders. The electrochemical synthesis was prepared in solution Ca{sup 2+}/EDTA{sup 4?}/PO{sub 4}{sup 3+} at concentration 0.25/0.25/0.15 M for 24 h. The electrochemical cell was consisted of two carbon rectangular electrodes connected to a function generator to produce PDC. There were two treatments for particles after electrosynthesized, namely without aging and aged for 2 days at 40 °C. For both cases, the particles were filtered and washed by demineralized water to eliminate the impurities and unreacted reactants. Then, the particles were dried at 100 °C for 2 days. The dried particles were characterized by X-ray diffraction, surface area analyzer, scanning electron microscopy (SEM), Fourier transform infrared spectra and thermogravimetric and differential thermal analysis. HA particles can be produced when the initial pH > 6. The aging process has significant effect on the produced HA particles. SEM images of HA particles showed that the powders consisted of agglomerates composed of fine crystallites and have morphology plate-like and sphere. The surface area of HA particles is in the range of 25 – 91 m{sup 2}/g. The largest particle surface area of HA was produced at 4 cm electrode distance, 80% cycle duty, frequency 0.1 Hz, amplitude 9 V and with aging process.

Nur, Adrian; Rahmawati, Alifah; Ilmi, Noor Izzati; Affandi, Samsudin; Widjaja, Arief [Departement of Chemical Engineering, Faculty of Industrial Technology, Sepuluh Nopember Institute of Technology, Kampus ITS Sukolilo, Surabaya 60111 (Indonesia)

2014-02-24

198

A Comparative Study on In Vitro Osteogenic Priming Potential of Electron Spun Scaffold PLLA/HA/Col, PLLA/HA, and PLLA/Col for Tissue Engineering Application  

PubMed Central

A comparative study on the in vitro osteogenic potential of electrospun poly-L-lactide/hydroxyapatite/collagen (PLLA/HA/Col, PLLA/HA, and PLLA/Col) scaffolds was conducted. The morphology, chemical composition, and surface roughness of the fibrous scaffolds were examined. Furthermore, cell attachment, distribution, morphology, mineralization, extracellular matrix protein localization, and gene expression of human mesenchymal stromal cells (hMSCs) differentiated on the fibrous scaffolds PLLA/Col/HA, PLLA/Col, and PLLA/HA were also analyzed. The electrospun scaffolds with a diameter of 200–950 nm demonstrated well-formed interconnected fibrous network structure, which supported the growth of hMSCs. When compared with PLLA/H%A and PLLA/Col scaffolds, PLLA/Col/HA scaffolds presented a higher density of viable cells and significant upregulation of genes associated with osteogenic lineage, which were achieved without the use of specific medium or growth factors. These results were supported by the elevated levels of calcium, osteocalcin, and mineralization (P<0.05) observed at different time points (0, 7, 14, and 21 days). Furthermore, electron microscopic observations and fibronectin localization revealed that PLLA/Col/HA scaffolds exhibited superior osteoinductivity, when compared with PLLA/Col or PLLA/HA scaffolds. These findings indicated that the fibrous structure and synergistic action of Col and nano-HA with high-molecular-weight PLLA played a vital role in inducing osteogenic differentiation of hMSCs. The data obtained in this study demonstrated that the developed fibrous PLLA/Col/HA biocomposite scaffold may be supportive for stem cell based therapies for bone repair, when compared with the other two scaffolds. PMID:25140798

Balaji Raghavendran, Hanumantha Rao; Puvaneswary, Subramaniam; Talebian, Sepehr; Raman Murali, Malliga; Vasudevaraj Naveen, Sangeetha; Krishnamurithy, G.; McKean, Robert; Kamarul, Tunku

2014-01-01

199

Nanostructure of biocompatible titania/hydroxyapatite coatings  

NASA Astrophysics Data System (ADS)

The article describes prospective composite biocompatible titania coatings modified with hydroxyapatite nanoparticles and obtained on intraosseous implants fabricated from commercially pure titanium VT1-00. Consistency changes of morphological characteristics, crystalline structure, physical and mechanical properties and biocompatibility of experimental titanium implant coatings obtained by the combination of oxidation and surface modification with hydroxyapatite during induction heat treatment are defined.

Fomin, Aleksandr A.; Rodionov, Igor V.; Steinhauer, Aleksey B.; Fomina, Marina A.; Petrova, Natalia V.; Zakharevich, Andrey M.; Skaptsov, Aleksandr A.; Gribov, Andrey N.; Atkin, Vsevolod S.

2014-01-01

200

Microstructure and properties of plasma-sprayed bio-coatings on a low-modulus titanium alloy from milled HA\\/Ti powders  

Microsoft Academic Search

New composite hydroxyapatite\\/titanium (HA\\/Ti) coatings were fabricated by plasma spraying on Ti–24Nb–4Zr–7.9Sn alloy from milled precursor powders. The microstructures, mechanical properties and apatite-induction abilities of the coatings were investigated, and the influences of the initial HA\\/Ti ratios on microstructure and properties were highlighted. XRD, SEM and TEM were used to analyze the microstructures of the coatings. The micro-hardness and elastic

G. Zhao; L. Xia; G. Wen; L. Song; X. Wang; K. Wu

201

A functional agarose-hydroxyapatite scaffold for osteochondral interface regeneration  

PubMed Central

Regeneration of the osteochondral interface is critical for integrative and functional cartilage repair. This study focuses on the design and optimization of a hydrogel-ceramic composite scaffold of agarose and hydroxyapatite (HA) for calcified cartilage formation. The first study objective was to compare the effects of HA on non-hypertrophic and hypertrophic chondrocytes cultured in the composite scaffold. Specifically, cell growth, biosynthesis, hypertrophy, and scaffold mechanical properties were evaluated. Next, the ceramic phase of the scaffold was optimized in terms of particle size (200 nm vs. 25 µm) and dose (0–6 w/v%). It was observed that while deep zone chondrocyte (DZC) biosynthesis and hypertrophy remained unaffected, hypertrophic chondrocytes measured higher matrix deposition and mineralization potential with the addition of HA. Most importantly, higher matrix content translated into significant increases in both compressive and shear mechanical properties. While cell hypertrophy was independent of ceramic size, matrix deposition was higher only with the addition of micron-sized ceramic particles. In addition, the highest matrix content, mechanical properties and mineralization potential were found in scaffolds with 3% micro-HA, which approximates both the mineral aggregate size and content of the native interface. These results demonstrate that the biomimetic hydrogel-ceramic composite is optimal for calcified cartilage formation and is a promising design strategy for osteochondral interface regeneration. PMID:22531222

Khanarian, Nora T.; Haney, Nora M.; Burga, Rachel A.; Lu, Helen H.

2013-01-01

202

A chondromimetic microsphere for in situ spatially controlled chondrogenic differentiation of human mesenchymal stem cells.  

PubMed

Human mesenchymal stem cells (hMSCs) have been identified as a viable cell source for cartilage tissue engineering. However, to undergo chondrogenic differentiation hMSCs require growth factors, in particular members of the transforming growth factor beta (TGF-?) family. While in vitro differentiation is feasible through continuous supplementation of TGF-?3, mechanisms to control and drive hMSCs down the chondrogenic lineage in their native microenvironment remain a significant challenge. The release of TGF-?3 from an injectable microsphere composed of the cartilage-associated extracellular matrix molecule hyaluronan represents a readily translatable approach for in situ differentiation of hMSCs for cartilage repair. In this study, chondromimetic hyaluronan microspheres were used as a growth factor delivery source for hMSC chondrogenesis. Cellular compatibility of the microspheres (1.2 and 14.1 ?m) with hMSCs was shown and release of TGF-?3 from the most promising 14.1 ?m microspheres to control differentiation of hMSCs was evaluated. Enhanced accumulation of cartilage-associated glycosaminoglycans by hMSCs incubated with TGF-?3-loaded microspheres was seen and positive staining for collagen type II and proteoglycan confirmed successful in vitro chondrogenesis. Gene expression analysis showed significantly increased expression of the chondrocyte-associated genes, collagen type II and aggrecan. This delivery platform resulted in significantly less collagen type X expression, suggesting the generation of a more stable cartilage phenotype. When evaluated in an ex vivo osteoarthritic cartilage model, implanted hMSCs with TGF-?3-loaded HA microspheres were detected within cartilage fibrillations and increased proteoglycan staining was seen in the tissue. In summary, data presented here demonstrate that TGF-?3-bound hyaluronan microspheres provide a suitable delivery system for induction of hMSC chondrogenesis and their use may represent a clinically feasible tissue engineering approach for the treatment of articular cartilage defects. PMID:24491910

Ansboro, Sharon; Hayes, Jessica S; Barron, Valerie; Browne, Shane; Howard, Linda; Greiser, Udo; Lalor, Pierce; Shannon, Fintan; Barry, Frank P; Pandit, Abhay; Murphy, J Mary

2014-04-10

203

An amphiphilic degradable polymer/hydroxyapatite composite with enhanced handling characteristics promotes osteogenic gene expression in bone marrow stromal cells  

PubMed Central

Electrospun polymer/hydroxyapatite (HA) composites combining biodegradability with osteoconductivity are attractive for skeletal tissue engineering applications. However, most biodegradable polymers such as PLA are hydrophobic and do not blend with adequate interfacial adhesion with HA, compromising the structural homogeneity, mechanical integrity, and biological performance of the composite. To overcome this challenge, we incorporated a hydrophilic polyethylene glycol (PEG) block to poly(D,L-lactic acid) to improve the adhesion of the degradable polymer with HA. The amphiphilic triblock copolymer PLA-PEG-PLA (PELA) improved the stability of HA-PELA suspension at 25 wt% HA content, which was readily electrospun into HA-PELA composite scaffolds with uniform fiber dimensions. HA-PELA was highly extensible (failure strain >200% vs. <40% for HA-PLA), superhydrophilic (~0° water contact angle vs. >100° for HA-PLA), and exhibited an 8-fold storage modulus increase (unlike deterioration for HA-PLA) upon hydration, owing to the favorable interaction between HA and PEG. HA-PELA also better promoted osteochondral lineage commitment of bone marrow stromal cells in unstimulated culture and supported far more potent osteogenesis upon induction than HA-PLA. We demonstrate that the chemical incorporation of PEG is an effective strategy to improve the performance of degradable polymer/HA composites for bone tissue engineering applications. PMID:23791675

Kutikov, Artem B.; Song, Jie

2013-01-01

204

Development of Risperidone PLGA Microspheres  

PubMed Central

The aim of this study was to design and evaluate biodegradable PLGA microspheres for sustained delivery of Risperidone, with an eventual goal of avoiding combination therapy for the treatment of schizophrenia. Two PLGA copolymers (50?:?50 and 75?:?25) were used to prepare four microsphere formulations of Risperidone. The microspheres were characterized by several in vitro techniques. In vivo studies in male Sprague-Dawley rats at 20 and 40?mg/kg doses revealed that all formulations exhibited an initial burst followed by sustained release of the active moiety. Additionally, formulations prepared with 50?:?50 PLGA had a shorter duration of action and lower cumulative AUC levels than the 75?:?25 PLGA microspheres. A simulation of multiple dosing at weekly or 15-day regimen revealed pulsatile behavior for all formulations with steady state being achieved by the second dose. Overall, the clinical use of Formulations A, B, C, or D will eliminate the need for combination oral therapy and reduce time to achieve steady state, with a smaller washout period upon cessation of therapy. Results of this study prove the suitability of using PLGA copolymers of varying composition and molecular weight to develop sustained release formulations that can tailor in vivo behavior and enhance pharmacological effectiveness of the drug. PMID:24616812

D'Souza, Susan; Faraj, Jabar A.; Giovagnoli, Stefano; DeLuca, Patrick P.

2014-01-01

205

Microspheres and nanoparticles from ultrasound  

NASA Astrophysics Data System (ADS)

Improved preparations of various examples of monodispersed, porous, hollow, and core-shell metal and semiconductor nanoparticles or nanowires have been developed. Now titania microspheres and nanoparticles and silica microspheres can be synthesized using an inexpensive high frequency (1.7 MHz) ultrasonic generator (household humidifier; ultrasonic spray pyrolysis; USP). Morphology and pore size of titania microspheres were controlled by the silica to Ti(IV) ratio and silica particle size. Fine tuning the precursor ratio affords sub-50 nm titania nanoparticles as well. In terms of silica microspheres, morphology was controlled by the silica to organic monomer ratio. In liquids irradiated with high intensity ultrasound (20 kHz; HIUS), acoustic cavitation produces high energy chemistry through intense local heating inside the gas phase of collapsing bubbles in the liquid. HIUS and USP confine the chemical reactions to isolated sub-micron reaction zones, but sonochemistry does so in a heated gas phase within a liquid, while USP uses a hot liquid droplet carried by a gas flow. Thus, USP can be viewed as a method of phase-separated synthesis using submicron-sized droplets as isolated chemical reactors for nanomaterial synthesis. While USP has been used to create both titania and silica spheres separately, there are no prior reports of titania-silica composites. Such nanocomposites of metal oxides have been produced, and by further manipulation, various porous structures with fascinating morphologies were generated. Briefly, a precursor solution was nebulized using a commercially available household ultrasonic humidifier (1.7 MHz ultrasound generator), and the resulting mist was carried in a gas stream of air through a quartz glass tube in a hot furnace. After exiting the hot zone, these microspheres are porous or hollow and in certain cases magnetically responsive. In the case of titania microspheres, they are rapidly taken up into the cytoplasm of mammalian cells and nearly noncytoxic. Small molecules like Rhodamine and DHED (dehydroevodiamine HCl; Alzheimer's disease therapeutic) can be delivered along with them. Furthermore, synthesis of carbon nanoparticles and titanate nanotube species are possible utilizing these microspheres. Characterizations were done by SEM, (S)TEM, optical/confocal microscopy, XRD, XPS, EDS, SAED, zeta potential, and BET.

Suh, Won Hyuk

206

21 CFR 522.1451 - Moxidectin microspheres for injection.  

Code of Federal Regulations, 2014 CFR

...2014-04-01 false Moxidectin microspheres for injection. 522.1451 Section...ANIMAL DRUGS § 522.1451 Moxidectin microspheres for injection. (a) Specifications...One contains 10 percent moxidectin microspheres, and the other contains a...

2014-04-01

207

Composite Tectocapsules Containing Porous Polymer Microspheres as Release Gates  

E-print Network

Composite Tectocapsules Containing Porous Polymer Microspheres as Release Gates Lisa M. Croll: Porous and amphiphilic polymer microspheres were incorporated into polyurea capsules in order to control) microspheres were simply encapsulated along with the xylene core solvent, the amphiphilic poly

Hitchcock, Adam P.

208

Delineation of the hydroxyapatite-nucleating domains of bone sialoprotein.  

PubMed

Bone sialoprotein (BSP) is a highly modified, anionic phosphoprotein that is expressed almost exclusively in mineralizing connective tissues and has been shown to be a potent nucleator of hydroxyapatite (HA). Two polyglutamic acid (poly[E]) regions, predicted to be in an alpha-helical conformation and located in the amino-terminal half of the molecule, are believed to be responsible for this activity. Using a prokaryotic expression system, full-length rat BSP was expressed and tested for HA nucleating activity in a steady-state agarose gel system. The unmodified protein is less potent than native bone BSP, indicating a role for the post-translational modifications in HA nucleation. Site-directed mutagenesis of the poly[E] regions in full-length BSP was performed, replacing the poly[E] with either polyaspartic acid (poly[D]) or polyalanine (poly[A]) to examine role of charge and conformation, respectively, in HA nucleation. Replacement of single domains with either poly[A] or poly[D] did not alter nucleating activity nor did replacement of both domains with poly[D]. Replacement of both domains with poly[A], however, significantly decreased nucleating activity. In addition, two recombinant peptides, each encompassing one of the two poly[E] domains, were expressed and tested for nucleating activity. Whereas the peptide encompassing the second poly[E] domain was capable of nucleating HA, the first domain peptide showed no activity. The conformation of the wild-type and mutated proteins and peptides were studied by circular dichroism and small angle x-ray scattering, and no secondary structure was evident. These results demonstrate that a sequence of at least eight contiguous glutamic acid residues is required for the nucleation of HA by BSP and that this nucleating "site" is not alpha-helical in conformation. PMID:12493752

Tye, Coralee E; Rattray, Kevin R; Warner, Kevin J; Gordon, Jonathan A R; Sodek, Jaro; Hunter, Graeme K; Goldberg, Harvey A

2003-03-01

209

Bone tissue engineering with a collagen-hydroxyapatite scaffold and culture expanded bone marrow stromal cells.  

PubMed

Osteoprogenitor cells combined with supportive biomaterials represent a promising approach to advance the standard of care for bone grafting procedures. However, this approach faces challenges, including inconsistent bone formation, cell survival in the implant, and appropriate biomaterial degradation. We have developed a collagen-hydroxyapatite (HA) scaffold that supports consistent osteogenesis by donor-derived osteoprogenitors, and is more easily degraded than a pure ceramic scaffold. Herein, the material properties are characterized as well as cell attachment, viability, and progenitor distribution in vitro. Furthermore, we examined the biological performance in vivo in a critical-size mouse calvarial defect. To aid in the evaluation of the in-house collagen-HA scaffold, the in vivo performance was compared with a commercial collagen-HA scaffold (Healos(®) , Depuy). The in-house collagen-HA scaffold supported consistent bone formation by predominantly donor-derived osteoblasts, nearly completely filling a 3.5 mm calvarial defect with bone in all samples (n?=?5) after 3 weeks of implantation. In terms of bone formation and donor cell retention at 3 weeks postimplantation, no statistical difference was found between the in-house and commercial scaffold following quantitative histomorphometry. The collagen-HA scaffold presented here is an open and well-defined platform that supports robust bone formation and should facilitate the further development of collagen-hydroxyapatite biomaterials for bone tissue engineering. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 103B: 243-253, 2015. PMID:24909953

Villa, Max M; Wang, Liping; Huang, Jianping; Rowe, David W; Wei, Mei

2015-02-01

210

Quantitative distribution assessment of HoAcAc microspheres and HoPLLA microspheres after direct injection.  

E-print Network

??This experimental study on interstitial brachytherapy describes the distribution of HoAcAc microspheres and HoPLLA microspheres after direct injection in tissue. The microspheres were injected in… (more)

Steenbeek, I.D.

2014-01-01

211

Hierarchically nanostructured hydroxyapatite: hydrothermal synthesis, morphology control, growth mechanism, and biological activity  

PubMed Central

Hierarchically nanosized hydroxyapatite (HA) with flower-like structure assembled from nanosheets consisting of nanorod building blocks was successfully synthesized by using CaCl2, NaH2PO4, and potassium sodium tartrate via a hydrothermal method at 200°C for 24 hours. The effects of heating time and heating temperature on the products were investigated. As a chelating ligand and template molecule, the potassium sodium tartrate plays a key role in the formation of hierarchically nanostructured HA. On the basis of experimental results, a possible mechanism based on soft-template and self-assembly was proposed for the formation and growth of the hierarchically nanostructured HA. Cytotoxicity experiments indicated that the hierarchically nanostructured HA had good biocompatibility. It was shown by in-vitro experiments that mesenchymal stem cells could attach to the hierarchically nanostructured HA after being cultured for 48 hours. Objective The purpose of this study was to develop facile and effective methods for the synthesis of novel hydroxyapatite (HA) with hierarchical nanostructures assembled from independent and discrete nanobuilding blocks. Methods A simple hydrothermal approach was applied to synthesize HA by using CaCl2, NaH2PO4, and potassium sodium tartrate at 200°C for 24 hours. The cell cytotoxicity of the hierarchically nanostructured HA was tested by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. Results HA displayed the flower-like structure assembled from nanosheets consisting of nanorod building blocks. The potassium sodium tartrate was used as a chelating ligand, inducing the formation and self-assembly of HA nanorods. The heating time and heating temperature influenced the aggregation and morphology of HA. The cell viability did not decrease with the increasing concentration of hierarchically nanostructured HA added. Conclusion A novel, simple and reliable hydrothermal route had been developed for the synthesis of hierarchically nanosized HA with flower-like structure assembled from nanosheets consisting of nanorod building blocks. The HA with the hierarchical nanostructure was formed via a soft-template assisted self-assembly mechanism. The hierarchically nanostructured HA has a good biocompatibility and essentially no in-vitro cytotoxicity. PMID:22619527

Ma, Ming-Guo

2012-01-01

212

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

2009-04-01

213

Microsphere coated substrate containing reactive aldehyde groups  

NASA Technical Reports Server (NTRS)

A synthetic organic resin is coated with a continuous layer of contiguous, tangential, individual microspheres having a uniform diameter preferably between 100 Angstroms and 2000 Angstroms. The microspheres are an addition polymerized polymer of an unsaturated aldehyde containing 4 to 20 carbon atoms and are covalently bonded to the substrate by means of high energy radiation grafting. The microspheres contain reactive aldehyde groups and can form conjugates with proteins such as enzymes or other aldehyde reactive materials.

Rembaum, Alan (Inventor); Yen, Richard C. K. (Inventor)

1984-01-01

214

Filling Porous Microspheres With Magnetic Material  

NASA Technical Reports Server (NTRS)

New process produces magnetic microspheres with controllable sizes, compositions, and properties for use in medical diagnostic tests, biological research, and chemical processes. Paramagnetic microspheres also made with process. Porous plastic microspheres prepared by polymerization of monomer in diluent by cross-linking agent. When diluent removed, it leaves tiny pores throughout polymerized spheres. Size and distribution of pores determined by amount and type of diluent and cross-linking agent.

Chang, Manchium; Colvin, Michael S.

1990-01-01

215

Hydroxyapatite bioactivated bacterial cellulose promotes osteoblast growth and the formation of bone nodules.  

PubMed

The goal of this study was to investigate the feasibility of bacterial cellulose (BC) scaffold to support osteoblast growth and bone formation. BC was produced by culturing Acetobacter xylinum supplemented with hydroxyapatite (HA) to form BC membranes (without HA) and BC/HA membranes. Membranes were subjected to X-ray photoelectron spectroscopy (XPS) analysis to determine surface element composition. The membranes were further used to evaluate osteoblast growth, alkaline phosphatase activity and bone nodule formation. BC was free of calcium and phosphate. However, XPS analysis revealed the presence of both calcium (10%) and phosphate (10%) at the surface of the BC/HA membrane. Osteoblast culture showed that BC alone was non-toxic and could sustain osteoblast adhesion. Furthermore, osteoblast adhesion and growth were significantly (p ?0.05) increased on BC/HA membranes as compared to BC alone. Both BC and BC/HA membranes improved osteoconductivity, as confirmed by the level of alkaline phosphatase (ALP) activity that increased from 2.5 mM with BC alone to 5.3 mM with BC/HA. BC/HA membranes also showed greater nodule formation and mineralization than the BC membrane alone. This was confirmed by Alizarin red staining (ARS) and energy dispersive X-ray spectroscopy (EDX). This work demonstrates that both BC and BC/HA may be useful in bone tissue engineering. PMID:23174338

Tazi, Neftaha; Zhang, Ze; Messaddeq, Younès; Almeida-Lopes, Luciana; Zanardi, Lisinéia M; Levinson, Dennis; Rouabhia, Mahmoud

2012-01-01

216

Dexamethasone-loaded hydroxyapatite enhances bone regeneration in rat calvarial defects.  

PubMed

A combination of bioceramics and osteogenic factors is potentially useful for bone regeneration applications. In the present study, hydroxyapatite particles (HA) were loaded with dexamethasone (Dex) and then characterized using SEM and drug release study. The bone regeneration ability of Dex-loaded HA (Dex/HA) was investigated in a rat critical size bone defect using digital mammography, multislice spiral-computed tomography (MSCT) imaging, and histological analysis. The HA and Dex/HA showed nano and micro-scale morphology with a nearly homogenous distribution of diameter. In addition, about 90 % of the drug was released from Dex/HA over a period of three days. After 8 weeks of implantation in rat calvarial defects, no sign of inflammation or complication was observed at the site of surgery. According to digital mammography and MSCT, Dex/HA showed the highest bone regeneration in rat bone defects compared to those received drug-free HA. Histological studies confirmed these data and showed osteointegration to the surrounding tissue. Taking all together, it was demonstrated that Dex/HA can be used as an appropriate synthetic graft for bone tissue engineering applications. These newly developed bioceramics can be used as new bone graft substitutes in orthopaedic surgery and is capable of enhancing bone regeneration. PMID:24281949

Tavakoli-darestani, Reza; Manafi-rasi, Alireza; Kamrani-rad, Amin

2014-01-01

217

Silver oxide-containing hydroxyapatite coating has in vivo antibacterial activity in the rat tibia.  

PubMed

Bacterial infection is a serious postoperative complication of joint replacement. To prevent infections related to implantation, we have developed a novel antibacterial coating with Ag-containing hydroxyapatite (Ag-HA). In the present study, we examined the antibacterial activity of Ag-HA implant coatings in the medullary cavity of rat tibiae. Forty 10-week-old rats received implantation of Ag-HA- or HA-coated titanium rods, then were inoculated with ?1.0?×?10(2) colony-forming units of methicillin-resistant Staphylococcus aureus. Bacterial counts were calculated for rats euthanized at 24, 48, and 72?h postoperatively. Serum levels of Ag (in the Ag-HA group only) were calculated for rats euthanized at 24, 48, 72?h and 4 weeks. Radiographic evaluations of bone infection were also performed at 4 weeks. Tibiae from both groups showing infection were evaluated histologically. Significant differences in bacterial counts were seen at 24, 48, and 72?h. Mean concentrations of Ag in serum peaked about 48?h after implantation, then gradually decreased. Mean radiographic scores for infection were significantly lower with Ag-HA implants than with HA implants. Histological examination showed better results for abscesses, bone resorption, and destruction of cortical bone around Ag-HA-coated implants. These results indicate that Ag-HA coatings may help prevent surgical-site infections associated with joint replacement. PMID:23589130

Akiyama, Takayuki; Miyamoto, Hiroshi; Yonekura, Yutaka; Tsukamoto, Masatsugu; Ando, Yoshiki; Noda, Iwao; Sonohata, Motoki; Mawatari, Masaaki

2013-08-01

218

Strength and fatigue properties of three-step sintered dense nanocrystal hydroxyapatite bioceramics  

NASA Astrophysics Data System (ADS)

Dense hydroxyapatite (HA) ceramic is a promising material for hard tissue repair due to its unique physical properties and biologic properties. However, the brittleness and low compressive strength of traditional HA ceramics limited their applications, because previous sintering methods produced HA ceramics with crystal sizes greater than nanometer range. In this study, nano-sized HA powder was employed to fabricate dense nanocrystal HA ceramic by high pressure molding, and followed by a three-step sintering process. The phase composition, microstructure, crystal dimension and crystal shape of the sintered ceramic were examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Mechanical properties of the HA ceramic were tested, and cytocompatibility was evaluated. The phase of the sintered ceramic was pure HA, and the crystal size was about 200 nm. The compressive strength and elastic modulus of the HA ceramic were comparable to human cortical bone, especially the good fatigue strength overcame brittleness of traditional sintered HA ceramics. Cell attachment experiment also demonstrated that the ceramics had a good cytocompatibility.

Guo, Wen-Guang; Qiu, Zhi-Ye; Cui, Han; Wang, Chang-Ming; Zhang, Xiao-Jun; Lee, In-Seop; Dong, Yu-Qi; Cui, Fu-Zhai

2013-06-01

219

Hydroxyapatite bioactivated bacterial cellulose promotes osteoblast growth and the formation of bone nodules  

PubMed Central

The goal of this study was to investigate the feasibility of bacterial cellulose (BC) scaffold to support osteoblast growth and bone formation. BC was produced by culturing Acetobacter xylinum supplemented with hydroxyapatite (HA) to form BC membranes (without HA) and BC/HA membranes. Membranes were subjected to X-ray photoelectron spectroscopy (XPS) analysis to determine surface element composition. The membranes were further used to evaluate osteoblast growth, alkaline phosphatase activity and bone nodule formation. BC was free of calcium and phosphate. However, XPS analysis revealed the presence of both calcium (10%) and phosphate (10%) at the surface of the BC/HA membrane. Osteoblast culture showed that BC alone was non-toxic and could sustain osteoblast adhesion. Furthermore, osteoblast adhesion and growth were significantly (p ?0.05) increased on BC/HA membranes as compared to BC alone. Both BC and BC/HA membranes improved osteoconductivity, as confirmed by the level of alkaline phosphatase (ALP) activity that increased from 2.5 mM with BC alone to 5.3 mM with BC/HA. BC/HA membranes also showed greater nodule formation and mineralization than the BC membrane alone. This was confirmed by Alizarin red staining (ARS) and energy dispersive X-ray spectroscopy (EDX). This work demonstrates that both BC and BC/HA may be useful in bone tissue engineering. PMID:23174338

2012-01-01

220

Sol-Gel-Derived Hydroxyapatite-Carbon Nanotube/Titania Coatings on Titanium Substrates  

PubMed Central

In this paper, hydroxyapatite-carbon nanotube/titania (HA-CNT/TiO2) double layer coatings were successfully developed on titanium (Ti) substrates intended for biomedical applications. A TiO2 coating was firstly developed by anodization to improve bonding between HA and Ti, and then the layer of HA and CNTs was coated on the surface by the sol-gel process to improve the biocompatibility and mechanical properties of Ti. The surfaces of double layer coatings were uniform and crack-free with a thickness of about 7 ?m. The bonding strength of the HA-CNT/TiO2 coating was higher than that of the pure HA and HA-CNT coatings. Additionally, in vitro cell experiments showed that CNTs promoted the adhesion of preosteoblasts on the HA-CNT/TiO2 double layer coatings. These unique surfaces combined with the osteoconductive properties of HA exhibited the excellent mechanical properties of CNTs. Therefore, the developed HA-CNT/TiO2 coatings on Ti substrates might be a promising material for bone replacement. PMID:22606041

Ji, Xiaoli; Lou, Weiwei; Wang, Qi; Ma, Jianfeng; Xu, Haihong; Bai, Qing; Liu, Chuantong; Liu, Jinsong

2012-01-01

221

The influence of silanisation on the mechanical and degradation behaviour of PLGA/HA composites.  

PubMed

This study investigates the influence of silanisation on the mechanical and degradation behaviour of PLGA/HA composites. Three different silanes (mercaptopropyl trimethoxy silane (MPTMS), aminopropyl trimethoxy silane (APTMS) and aminopropyltriethoxy silane (APTES)) were applied to HA substrates in order to study the effect of head group (which binds to the polymer) and tail group (which binds to the surface hydroxyl groups in HA). A composite of hydroxyapatite (HA) and poly(d,l lactide-co-glycolide (50:50)) (PLGA) was investigated. The influence of concentration, the reaction time, drying temperature and substrate surface on silanisation was examined. TGA was used to detect the degree of silanisation. HA with MPTMS (1wt.% MPTMS with reaction time of 1h) was used as filler in PLGA-30wt.% HA composites for an in-vitro degradation study carried out in PBS. In addition, the mechanical properties of the composites were studied. Silanisation affects the properties of the composite by improving the bonding at the interface and hence it was found to influence the plastic mechanical properties rather than the elastic mechanical properties or the degradation profile of the composite. PMID:25579967

Naik, Ashutosh; Best, Serena M; Cameron, Ruth E

2015-03-01

222

Glass microspheres for medical applications  

NASA Astrophysics Data System (ADS)

Radioactive dysprosium lithium borate glass microspheres have been developed as biodegradable radiation delivery vehicles for the radiation synovectomy treatment of rheumatoid arthritis. Once injected into a diseased joint, the microspheres deliver a potent dose of radiation to the diseased tissue, while a non-uniform chemical reaction converts the glass into an amorphous, porous, hydrated dysprosium phosphate reaction product. The non-radioactive, lithium-borate component is dissolved from the glass (up to 94% weight loss), while the radioactive 165Dy reacts with phosphate anions in the body fluids, and becomes "chemically" trapped in a solid, dysprosium phosphate reaction product that has the same size as the un-reacted glass microsphere. Ethylene diamine tetraacetate (EDTA) chelation therapy can be used to dissolve the dysprosium phosphate reaction product after the radiation delivery has subsided. The dysprosium phosphate reaction product, which formed in vivo in the joint of a Sprague-Dawley rat, was dissolved by EDTA chelation therapy in <1 week, without causing any detectable joint damage. The combination of dysprosium lithium borate glass microspheres and EDTA chelation therapy provides an unique "tool" for the medical community, which can deliver a large dose (>100 Gy) of localized beta radiation to a treatment site within the body, followed by complete biodegradability. The non-uniform reaction process is a desirable characteristic for a biodegradable radiation delivery vehicle, but it is also a novel material synthesis technique that can convert a glass to a highly porous materials with widely varying chemical composition by simple, low-temperature, glass/solution reaction. The reaction product formed by nonuniform reaction occupies the same volume as the un-reacted glass, and after drying for 1 h at 300°C, has a specific surface area of ?200 m2/g, a pore size of ?30 nm, and a nominal crushing strength of ?10 MPa. Finally, rhenium glass microspheres, composed of micron-sized, metallic rhenium particles dispersed within a magnesium alumino borate glass matrix were produced by sintering ReO2 powder and glass frit at 1050°C. A 50 mg injection of radioactive rhenium glass microspheres containing 3.7 GBq of 186Re and 8.5 GBq of 188Re could be used to deliver a 100 Gy dose to a cancerous tumor, while limiting the total body dose caused by rhenium dissolution to approximately 1 mGy.

Conzone, Samuel David

223

Substituted Hydroxyapatites with Antibacterial Properties  

PubMed Central

Reconstructive surgery is presently struggling with the problem of infections located within implantation biomaterials. Of course, the best antibacterial protection is antibiotic therapy. However, oral antibiotic therapy is sometimes ineffective, while administering an antibiotic at the location of infection is often associated with an unfavourable ratio of dosage efficiency and toxic effect. Thus, the present study aims to find a new factor which may improve antibacterial activity while also presenting low toxicity to the human cells. Such factors are usually implemented along with the implant itself and may be an integral part of it. Many recent studies have focused on inorganic factors, such as metal nanoparticles, salts, and metal oxides. The advantages of inorganic factors include the ease with which they can be combined with ceramic and polymeric biomaterials. The following review focuses on hydroxyapatites substituted with ions with antibacterial properties. It considers materials that have already been applied in regenerative medicine (e.g., hydroxyapatites with silver ions) and those that are only at the preliminary stage of research and which could potentially be used in implantology or dentistry. We present methods for the synthesis of modified apatites and the antibacterial mechanisms of various ions as well as their antibacterial efficiency. PMID:24949423

Kolmas, Joanna; Groszyk, Ewa; Kwiatkowska-Ró?ycka, Dagmara

2014-01-01

224

Coupling system to a microsphere cavity  

NASA Technical Reports Server (NTRS)

A system of coupling optical energy in a waveguide mode, into a resonator that operates in a whispering gallery mode. A first part of the operation uses a fiber in its waveguide mode to couple information into a resonator e.g. a microsphere. The fiber is cleaved at an angle .PHI. which causes total internal reflection within the fiber. The energy in the fiber then forms an evanescent field and a microsphere is placed in the area of the evanescent field. If the microsphere resonance is resonant with energy in the fiber, then the information in the fiber is effectively transferred to the microsphere.

Iltchenko, Vladimir (Inventor); Maleki, Lute (Inventor); Yao, Steve (Inventor); Wu, Chi (Inventor)

2002-01-01

225

21 CFR 870.1360 - Trace microsphere.  

Code of Federal Regulations, 2013 CFR

...FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Diagnostic Devices § 870.1360 Trace microsphere. (a) Identification. A trace...

2013-04-01

226

21 CFR 870.1360 - Trace microsphere.  

Code of Federal Regulations, 2011 CFR

...FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Diagnostic Devices § 870.1360 Trace microsphere. (a) Identification. A trace...

2011-04-01

227

Hydroxyapatite-coated sillicone rubber enhanced cell adhesion and it may be through the interaction of EF1? and ?-actin.  

PubMed

Silicone rubber (SR) is a common soft tissue filler material used in plastic surgery. However, it presents a poor surface for cellular adhesion and suffers from poor biocompatibility. In contrast, hydroxyapatite (HA), a prominent component of animal bone and teeth, can promote improved cell compatibility, but HA is an unsuitable filler material because of the brittleness in mechanism. In this study, using a simple and economical method, two sizes of HA was applied to coat on SR to counteract the poor biocompatibility of SR. Surface and mechanical properties of SR and HA/SRs confirmed that coating with HA changes the surface topology and material properties. Analysis of cell proliferation and adhesion as well as measurement of the expression levels of adhesion related molecules indicated that HA-coated SR significantly increased cell compatibility. Furthermore, mass spectrometry proved that the biocompatibility improvement may be related to elongation factor 1-beta (EF1?)/?-actin adjusted cytoskeletal rearrangement. PMID:25386892

Shi, Xiao-hua; Wang, Shao-liang; Zhang, Yi-ming; Wang, Yi-cheng; Yang, Zhi; Zhou, Xin; Lei, Ze-yuan; Fan, Dong-li

2014-01-01

228

Evaluation of Bone Healing on Sandblasted and Acid Etched Implants Coated with Nanocrystalline Hydroxyapatite: An In Vivo Study in Rabbit Femur  

PubMed Central

This study aimed at investigating if a coating of hydroxyapatite nanocrystals would enhance bone healing over time in trabecular bone. Sandblasted and acid etched titanium implants with and without a submicron thick coat of hydroxyapatite nanocrystals (nano-HA) were implanted in rabbit femur with healing times of 2, 4, and 9 weeks. Removal torque analyses and histological evaluations were performed. The torque analysis did not show any significant differences between the implants at any healing time. The control implant showed a tendency of more newly formed bone after 4 weeks of healing and significantly higher bone area values after 9 weeks of healing. According to the results from this present study, both control and nano-HA surfaces were biocompatible and osteoconductive. A submicron thick coating of hydroxyapatite nanocrystals deposited onto blasted and acid etched screw shaped titanium implants did not enhance bone healing, as compared to blasted and etched control implants when placed in trabecular bone. PMID:24723952

Melin Svanborg, Lory; Meirelles, Luiz; Franke Stenport, Victoria; Currie, Fredrik; Andersson, Martin

2014-01-01

229

Evaluation of bone healing on sandblasted and Acid etched implants coated with nanocrystalline hydroxyapatite: an in vivo study in rabbit femur.  

PubMed

This study aimed at investigating if a coating of hydroxyapatite nanocrystals would enhance bone healing over time in trabecular bone. Sandblasted and acid etched titanium implants with and without a submicron thick coat of hydroxyapatite nanocrystals (nano-HA) were implanted in rabbit femur with healing times of 2, 4, and 9 weeks. Removal torque analyses and histological evaluations were performed. The torque analysis did not show any significant differences between the implants at any healing time. The control implant showed a tendency of more newly formed bone after 4 weeks of healing and significantly higher bone area values after 9 weeks of healing. According to the results from this present study, both control and nano-HA surfaces were biocompatible and osteoconductive. A submicron thick coating of hydroxyapatite nanocrystals deposited onto blasted and acid etched screw shaped titanium implants did not enhance bone healing, as compared to blasted and etched control implants when placed in trabecular bone. PMID:24723952

Melin Svanborg, Lory; Meirelles, Luiz; Franke Stenport, Victoria; Kjellin, Per; Currie, Fredrik; Andersson, Martin; Wennerberg, Ann

2014-01-01

230

Fretting wear behaviour of hydroxyapatite-titanium composites in simulated body fluid, supplemented with 5 g l-1 bovine serum albumin  

NASA Astrophysics Data System (ADS)

Damaged articulating joints can be repaired or replaced with synthetic biomaterials, which can release wear debris due to articulation, leading to the osteolysis. In a recent work, it has been shown that it is possible to achieve a better combination of flexural strength/fracture toughness as well as in vitro bioactivity and cytocompatibility properties in spark plasma sintered hydroxyapatite-titanium (HA-Ti) composites. Although hydroxyapatite and titanium are well documented for their good biocompatibility, nanosized hydroxyapatite (HA) and titanium (Ti) particles can cause severe toxicity to cells. In order to address this issue, fretting wear study of HA-Ti composites under dry and wet (1× SBF, supplemented with 5 g l-1 bovine serum albumin (BSA)) condition was performed to assess the wear resistance as well as wear debris formation, in vitro. The experimental results reveal one order of magnitude lower wear rate for HA-10 wt% Ti (7.5 × 10-5 mm3 N-1 m-1) composite than monolithic HA (3.9 × 10-4 mm3 N-1 m-1) in simulated body fluid. The difference in the tribological properties has been analyzed in the light of phase assemblages and mechanical properties. Overall, the results suggest the potential use of HA-Ti composites over existing HA-based biocomposites in orthopedic as well as dental applications.

Kumar, Alok; Biswas, Krishanu; Basu, Bikramjit

2013-10-01

231

Interconnected porous hydroxyapatite ceramics for bone tissue engineering  

PubMed Central

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

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

2008-01-01

232

Compression molding of aerogel microspheres  

DOEpatents

An aerogel composite material produced by compression molding of aerogel microspheres (powders) mixed together with a small percentage of polymer binder to form monolithic shapes in a cost-effective manner is disclosed. The aerogel composites are formed by mixing aerogel microspheres with a polymer binder, placing the mixture in a mold and heating under pressure, which results in a composite with a density of 50--800 kg/m{sup 3} (0.05--0.80 g/cc). The thermal conductivity of the thus formed aerogel composite is below that of air, but higher than the thermal conductivity of monolithic aerogels. The resulting aerogel composites are attractive for applications such as thermal insulation since fabrication thereof does not require large and expensive processing equipment. In addition to thermal insulation, the aerogel composites may be utilized for filtration, ICF target, double layer capacitors, and capacitive deionization. 4 figs.

Pekala, R.W.; Hrubesh, L.W.

1998-03-24

233

Compression molding of aerogel microspheres  

DOEpatents

An aerogel composite material produced by compression molding of aerogel microspheres (powders) mixed together with a small percentage of polymer binder to form monolithic shapes in a cost-effective manner. The aerogel composites are formed by mixing aerogel microspheres with a polymer binder, placing the mixture in a mold and heating under pressure, which results in a composite with a density of 50-800 kg/m.sup.3 (0.05-0.80 g/cc). The thermal conductivity of the thus formed aerogel composite is below that of air, but higher than the thermal conductivity of monolithic aerogels. The resulting aerogel composites are attractive for applications such as thermal insulation since fabrication thereof does not require large and expensive processing equipment. In addition to thermal insulation, the aerogel composites may be utilized for filtration, ICF target, double layer capacitors, and capacitive deionization.

Pekala, Richard W. (Pleasant Hill, CA); Hrubesh, Lawrence W. (Pleasanton, CA)

1998-03-24

234

Robocasting nanocomposite scaffolds of poly(caprolactone)/hydroxyapatite incorporating modified carbon nanotubes for hard tissue reconstruction.  

PubMed

Nanocomposite scaffolds with tailored 3D pore configuration are promising candidates for the reconstruction of bone. Here we fabricated novel nanocomposite bone scaffolds through robocasting. Poly(caprolactone) (PCL)-hydroxyapatite (HA) slurry containing ionically modified carbon nanotubes (imCNTs) was robotic-dispensed and structured layer-by-layer into macrochanneled 3D scaffolds under adjusted processing conditions. Homogeneous dispersion of imCNTs (0.2 wt % relative to PCL-HA) was achieved in acetone, aiding in the preparation of PCL-HA-imCNTs slurry with good mixing property. Incorporation of imCNTs into PCL-HA composition significantly improved the compressive strength and elastic modulus of the robotic-dispensed scaffolds (~1.5-fold in strength and ~2.5-fold in elastic modulus). When incubated in simulated body fluid (SBF), PCL-HA-imCNT nanocomposite scaffold induced substantial mineralization of apatite in a similar manner to the PCL-HA scaffold, which was contrasted in pure PCL scaffold. MC3T3-E1 cell culture on the scaffolds demonstrated that cell proliferation levels were significantly higher in both PCL-HA-imCNT and PCL-HA than in pure PCL, and no significant difference was found between the nanocomposite scaffolds. When the PCL-HA-imCNT scaffold was implanted into a rat subcutaneous tissue for 4 weeks, soft fibrous tissues with neo-blood vessels formed well in the pore channels of the scaffolds without any significant inflammatory signs. Tissue reactions in PCL-HA-imCNT scaffold were similar to those in PCL-HA scaffold, suggesting incorporated imCNT did not negate the beneficial biological roles of HA. While more long-term in vivo research in bone defect models is needed to confirm clinical availability, our results suggest robotic-dispensed PCL-HA-imCNT nanocomposite scaffolds can be considered promising new candidate matrices for bone regeneration. PMID:23184729

Dorj, Biligzaya; Won, Jong-Eun; Kim, Joong-Hyun; Choi, Seong-Jun; Shin, Ueon Sang; Kim, Hae-Won

2013-06-01

235

Bone integration capability of nanopolymorphic crystalline hydroxyapatite coated on titanium implants.  

PubMed

The mechanism by which hydroxyapatite (HA)-coated titanium promotes bone-implant integration is largely unknown. Furthermore, refining the fabrication of nano-structured HA to the level applicable to the mass production process for titanium implants is challenging. This study reports successful creation of nanopolymorphic crystalline HA on microroughened titanium surfaces using a combination of flame spray and low-temperature calcination and tests its biological capability to enhance bone-implant integration. Sandblasted microroughened titanium implants and sandblasted + HA-coated titanium implants were subjected to biomechanical and histomorphometric analyses in a rat model. The HA was 55% crystallized and consisted of nanoscale needle-like architectures developed in various diameters, lengths, and orientations, which resulted in a 70% increase in surface area compared to noncoated microroughened surfaces. The HA was free from impurity contaminants, with a calcium/phosphorus ratio of 1.66 being equivalent to that of stoichiometric HA. As compared to microroughened implants, HA-coated implants increased the strength of bone-implant integration consistently at both early and late stages of healing. HA-coated implants showed an increased percentage of bone-implant contact and bone volume within 50 ?m proximity of the implant surface, as well as a remarkably reduced percentage of soft tissue intervention between bone and the implant surface. In contrast, bone volume outside the 50 ?m border was lower around HA-coated implants. Thus, this study demonstrated that the addition of pure nanopolymorphic crystalline HA to microroughened titanium not only accelerates but also enhances the level of bone-implant integration and identified the specific tissue morphogenesis parameters modulated by HA coating. In particular, the nanocrystalline HA was proven to be drastic in increasing osteoconductivity and inhibiting soft tissue infiltration, but the effect was limited to the immediate microenvironment surrounding the implant. PMID:22359461

Yamada, Masahiro; Ueno, Takeshi; Tsukimura, Naoki; Ikeda, Takayuki; Nakagawa, Kaori; Hori, Norio; Suzuki, Takeo; Ogawa, Takahiro

2012-01-01

236

Microspheres in Plasma Display Panels  

NASA Technical Reports Server (NTRS)

Filling small bubbles of molten glass with gases is just as difficult as it sounds, but the technical staff at NASA is not known to shy away from a difficult task. When Microsphere Systems, Inc. (MSI), of Ypsilanti, Michigan, and Imaging Systems Technology, Inc. (IST), of Toledo, Ohio, were trying to push the limits of plasma displays but were having difficulty with the designs, NASA s Glenn Garrett Morgan Commercialization Initiative (GMCI) assembled key personnel at Glenn Research Center and Ohio State University for a brainstorming session to come up with a solution for the companies. They needed a system that could produce hollow, glass micro-sized spheres (microspheres) that could be filled with a variety of gasses. But the extremely high temperature required to force the micro-sized glass bubbles to form at the tip of a metal nozzle resulted in severe discoloration of the microspheres. After countless experiments on various glass-metal combinations, they had turned to the GMCI for help. NASA experts in advanced metals, ceramics, and glass concluded that a new design approach was necessary. The team determined that what was needed was a phosphate glass composition that would remain transparent, and they went to work on a solution. Six weeks later, using the design tips from the NASA team, Tim Henderson, president of MSI, had designed a new system in which all surfaces in contact with the molten glass would be ceramic instead of metal. Meanwhile, IST was able to complete a Phase I Small Business Innovation Research (SBIR) grant supported by the National Science Foundation (NSF) and supply a potential customer with samples of the microspheres for evaluation as filler materials for high-performance insulations.

2006-01-01

237

Nonaggregating Microspheres Containing Aldehyde Groups  

NASA Technical Reports Server (NTRS)

Cobalt gamma irradiation of hydrophilic monomers in presence of acrolein yields exceptionally-stable, nonaggregating microspheres. Mixtures of 2-hydroxyethyl methacrylate (HEMA) and acrolein form homogeneous solutions in distilled water containing 0.4 percent polyethylene oxide (PEO). After deaeration with nitrogen, mixtures irradiated at room temperature with gamma rays from cobalt source; total exposure time 4 hours, at rate of 0.2 milliroentgen per hour. Reaction product centrifuged three times for purification and kept in distilled water.

Rembaum, Alan

1989-01-01

238

Making Latex Microspheres in Space  

NASA Technical Reports Server (NTRS)

Equipment yields larger, more uniform particles. Two NASA reports describe first commercial product to be manufactured in space. Product monodisperse latex, suspension of spherical particles of essentially same diameter. Carried aboard Space Shuttle on its orbital missions, monodisperse latex reactor (MLR) produces spheres of much larger size than possible on Earth. Mircospheres 30 micrometers in diameter produced, whereas 5 micrometers is limit for Earthbound reactors. Microspheres as large as 100 micrometers scheduled for production in MLR.

Kornfeld, D. M.; Vanderhoff, J. W.; El-Aasser, M. S.; Micale, F. J.; Sudol, E. D.; Tseng, C. M.; Silwanowicz, A.

1986-01-01

239

Improve the Strength of PLA/HA Composite Through the Use of Surface Initiated Polymerization and Phosphonic Acid Coupling Agent  

PubMed Central

Bioresorbable composite made from degradable polymers, e.g., polylactide (PLA), and bioactive calcium phosphates, e.g., hydroxyapatite (HA), are clinically desirable for bone fixation, repair and tissue engineering because they do not need to be removed by surgery after the bone heals. However, preparation of PLA/HA composite from non-modified HA usually results in mechanical strength reductions due to a weak interface between PLA and HA. In this study, a calcium-phosphate/phosphonate hybrid shell was developed to introduce a greater amount of reactive hydroxyl groups onto the HA particles. Then, PLA was successfully grafted on HA by surface-initiated polymerization through the non-ionic surface hydroxyl groups. Thermogravimetric analysis indiated that the amount of grafted PLA on HA can be up to 7 %, which is about 50 % greater than that from the literature. PLA grafted HA shows significantly different pH dependent ?-potential and particle size profiles from those of uncoated HA. By combining the phosphonic acid coupling agent and surface initiated polymerization, PLA could directly link to HA through covalent bond so that the interfacial interaction in the PLA/HA composite can be significantly improved. The diametral tensile strength of PLA/HA composite prepared from PLA-grafted HA was found to be over twice that of the composite prepared from the non-modified HA. Moreover, the tensile strength of the improved composite was 23 % higher than that of PLA alone. By varying additional variables, this approach has the potential to produce bioresorbable composites with improved mechanical properties that are in the range of natural bones, and can have wide applications for bone fixation and repair in load-bearing areas. PMID:22399838

Wang, Tongxin; Chow, Laurence C.; Frukhtbeyn, Stanislav A.; Ting, Andy Hai; Dong, Quanxiao; Yang, Mingshu; Mitchell, James W.

2012-01-01

240

Physicochemical properties of the novel biphasic hydroxyapatite-magnesium phosphate biomaterial.  

PubMed

Besides high-temperature calcium phosphates (CaPs), low-temperature calcium phosphate bone cements (CPCs), due to excellent biological properties: bioactivity, biocompability and osteoconductivity, are successfully used as bone substitutes. However, some disadvantages, related mainly to their low resorption rate and poor mechanical properties result in limited range of applications of these implant materials to non-loaded places in the skeletal system. To overcome this problem, magnesium phosphate cements (MPCs) with high strength have been considered as biomaterials. The main disadvantage of MPCs is that the acid-base setting reaction is an exothermic process that must be strictly controlled to avoid tissue necrosis. In this work, a new composite bone substitute (Hydroxyapatite Magnesium Phosphate Material - HMPM) based on hydroxyapatite (HA) and magnesium phosphate cement (MPC) with sodium pyrophosphate applied as a retardant of setting reaction was obtained. Its setting time was adequate for clinical applications. Combining properties of HA and MPC has made it possible to obtain microporous (showing bimodal pore size distribution in the range of 0.005-1.700 micrometers) potential implant material showing good surgical handiness and sufficient mechanical strength. Effectiveness of sodium pyrophosphate as a retardant of exothermic setting reaction of the new cement formulation was confirmed. After setting and hardening, the material consisted of hydroxyapatite and struvite as crystalline phases. Unreacted magnesium oxide was not detected. PMID:24215450

Pijocha, Dawid; Zima, Aneta; Paszkiewicz, Zofia; ?lósarczyk, Anna

2013-01-01

241

Diffusion Flame Synthesis of Hydroxyapatite Nanoparticles using Urea Assisted Precursor Solution  

NASA Astrophysics Data System (ADS)

Hydroxyapatite (HA) or (Ca10(PO4)6(OH)2 has been widely used in orthopedics and dental applications for human bone implant and teeth filler due to their biocompatibility and osteoconductive properties. Fine to nanoparticles of HA with appropriate stoichiometry and purity are preferred because they enhance densification and bioactive properties. Here, we reported the synthesis of hydroxyapatite particles in a diffusion flame reactor. LPG mainly consisting of butane and propane was used as fuel and compressed air was used as oxidizer and carrier gas. The effects of urea adding into precursor on morphology and crystallinity of the generated particles were investigated. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to observe particles morphology and crystallinity, respectively. Purity of the generated particles was analyzed quantitatively from XRD pattern using Rietveld method. Spherical shape of particles morphology was obtained for particles synthesized without urea added into precursor. Increasing fuel flow rate and urea concentration led to further disintegration of the generated particles. Nano sized particles were generated using fuel flow rate of 1 L/min and 30 w% concentration of urea added into precursor. However, increasing urea concentration led to the increase of tricalcium phosphate as a further reaction of hydroxyapatite for flame generated by using LPG as fuel of 1 L/min.

Widiyastuti; Setiawan, Adhi; Setyawan, Heru; Kusdianto; Nurtono, Tantular; Nia, Suci Madha; Winardi, Sugeng

2011-12-01

242

Synthesis of chitosan/hydroxyapatite membranes coated with hydroxycarbonate apatite for guided tissue regeneration purposes  

NASA Astrophysics Data System (ADS)

Chitosan, which is a non-toxic, biodegradable and biocompatible biopolymer, has been widely researched for several applications in the field of biomaterials. Calcium phosphate ceramics stand out among the so-called bioceramics for their absence of local or systemic toxicity, their non-response to foreign bodies or inflammations, and their apparent ability to bond to the host tissue. Hydroxyapatite (HA) is one of the most important bioceramics because it is the main component of the mineral phase of bone. The aim of this work was to produce chitosan membranes coated with hydroxyapatite using the modified biomimetic method. Membranes were synthesized from a solution containing 2% of chitosan in acetic acid (weight/volume) via the solvent evaporation method. Specimens were immersed in a sodium silicate solution and then in a 1.5 SBF (simulated body fluid) solution. The crystallinity of the HA formed over the membranes was correlated to the use of the nucleation agent (the sodium silicate solution itself). Coated membranes were characterized by means of scanning electron microscopy - SEM, X-ray diffraction - XRD, and Fourier transform infrared spectroscopy - FTIR. The results indicate a homogeneous coating covering the entire surface of the membrane and the production of a semi-crystalline hydroxyapatite layer similar to the mineral phase of human bone.

Fraga, Alexandre Félix; Filho, Edson de Almeida; Rigo, Eliana Cristina da Silva; Boschi, Anselmo Ortega

2011-02-01

243

PCL/chitosan/Zn-doped nHA electrospun nanocomposite scaffold promotes adipose derived stem cells adhesion and proliferation.  

PubMed

Chitosan (Ch), and poly(?-caprolactone) (PCL), widely used as biomaterials with desirable properties for tissue engineering applications, were both blended with zinc-doped hydroxyapatite nanoparticles(nZnHA) and electrospun into nanofibrous scaffolds using formic acid/acetic acid. The rationale behind this study was to demonstrate that presence of small quantities of Zn(2+) ions doped in HA nanoparticles can improve biocompatibility of PCL/Ch blends. SEM observation revealed that average fiber diameter was increased from about 136nm for a PCL/Ch blend, to around 210nm for PCL/Ch/nZnHA nanocomposite. PCL/Ch/nZnHA scaffolds offered higher elastic modulus (about 3-fold) and tensile strength (nearly 1.5-fold) than the corresponding PCL/Ch scaffolds. In-vitro biocompatibility studies using human adipose derived stem cells (hAD-MSCs), demonstrated that the presence of only 5wt% nZnHA in PCL/Ch/nZnHA nanocomposites enhanced hAD-MSCs' attachment compared to PCL/Ch and PCL/Ch/nHA. Finally, hAD-MSCs proliferation occurred at significantly higher rates of 1.5, 1.3 and 1.2 times on PCL/Ch/nZnHA scaffold compared to PCL, PCL/Ch and PCL/Ch/nHA, respectively. PMID:25542118

Ghorbani, Fereshteh Mohammad; Kaffashi, Babak; Shokrollahi, Parvin; Seyedjafari, Ehsan; Ardeshirylajimi, Abdolreza

2015-03-15

244

Electrospun polyurethane/hydroxyapatite bioactive Scaffolds for bone tissue engineering: the role of solvent and hydroxyapatite particles.  

PubMed

Polyurethane (PU) is a promising polymer to support bone-matrix producing cells due to its durability and mechanical resistance. In this study two types of medical grade poly-ether urethanes Z3A1 and Z9A1 and PU-Hydroxyapatite (PU-HA) composites were investigated for their ability to act as a scaffold for tissue engineered bone. PU dissolved in varying concentrations of dimethylformamide (DMF) and tetrahydrofuran (THF) solvents were electrospun to attain scaffolds with randomly orientated non-woven fibres. Bioactive polymeric composite scaffolds were created using 15 wt% Z3A1 in a 70/30 DMF/THF PU solution and incorporating micro- or nano-sized HA particles in a ratio of 3:1 respectively, whilst a 25 wt% Z9A1 PU solution was doped in ratio of 5:1. Chemical properties of the resulting composites were evaluated by FTIR and physical properties by SEM. Tensile mechanical testing was carried out on all electrospun scaffolds. MLO-A5 osteoblastic mouse cells and human embryonic mesenchymal progenitor cells, hES-MPs were seeded on the scaffolds to test their biocompatibility and ability to support mineralised matrix production over a 28 day culture period. Cell viability was assayed by MTT and calcium and collagen deposition by Sirius red and alizarin red respectively. SEM images of both electrospun PU scaffolds and PU-HA composite scaffolds showed differences in fibre morphology with changes in solvent combinations and size of HA particles. Inclusion of THF eliminated the presence of beads in fibres that were present in scaffolds fabricated with 100% DMF solvent, and resulted in fibres with a more uniform morphology and thicker diameters. Mechanical testing demonstrated that the Young?s Modulus and yield strength was lower at higher THF concentrations. Inclusion of both sizes of HA particles in PU-HA solutions reinforced the scaffolds leading to higher mechanical properties, whilst FTIR characterisation confirmed the presence of HA in all composite scaffolds. Although all scaffolds supported proliferation of both cell types and deposition of calcified matrix, PU-HA composite fibres containing nano-HA enabled the highest cell viability and collagen deposition. These scaffolds have the potential to support bone matrix formation for bone tissue engineering. PMID:25117379

Tetteh, G; Khan, A S; Delaine-Smith, R M; Reilly, G C; Rehman, I U

2014-11-01

245

Nanostructured Si, Mg, CO3 2- Substituted Hydroxyapatite Coatings Deposited by Liquid Precursor Plasma Spraying: Synthesis and Characterization  

NASA Astrophysics Data System (ADS)

In this study, a novel liquid precursor plasma spraying (LPPS) process was used to deposit Si, Mg, CO3 2- substituted hydroxyapatite (HA) coatings (alone and cosubstituted) onto Ti-6Al-4V substrates. Salts of silicon, magnesium, and carbonate elements were directly added into the HA liquid precursor for subsequent plasma spraying. The phase composition, structure, and morphology of all HA coatings were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Fourier transform infrared (FTIR) spectroscopy. The results indicated that the trace elements were successfully incorporated into the HA structure and nanostructured coatings were obtained for all doped HA formulations. The incorporation of trace elements into the HA structure reduced its crystallinity, especially when silicon, magnesium and carbonate ions entered simultaneously into the HA structure. FTIR spectra showed that the Si-HA and Mg-HA coatings had decreased intensities in both the O-H and P-O bands and that the CO3 2--HA coating was mainly a B-type carbonate-substituted HA. The results showed that the LPPS process is an effective and simple method to synthesize trace element substituted biomimetic HA coatings with nanostructure.

Huang, Tao; Xiao, Yanfeng; Wang, Shanling; Huang, Yi; Liu, Xiaoguang; Wu, Fang; Gu, Zhongwei

2011-06-01

246

Preparation of hydroxyapatite-gelatin nanocomposite  

Microsoft Academic Search

A nanocomposite of gelatin[GEL]-hydroxyapatite[HAp] was prepared using the biomimetic process. The hydroxyapatite nanocrystals were precipitated in aqueous solution of gelatin at pH 8 and 38°C. The chemical bonding between calcium ions of HAp and carboxyl ions of GEL molecules induced a red-shift of the 1339cm?1 band of GEL in FT-IR analysis. TEM images and electron diffraction patterns for the nanocomposite

Myung Chul Chang; Ching-Chang Ko; William H. Douglas

2003-01-01

247

On the anisotropic elastic properties of hydroxyapatite.  

NASA Technical Reports Server (NTRS)

Experimental measurements of the isotropic elastic moduli on polycrystalline specimens of hydroxyapatite and fluorapatite are compared with elastic constants measured directly from single crystals of fluorapatite in order to derive a set of pseudo single crystal elastic constants for hydroxyapatite. The stiffness coefficients thus derived are given. The anisotropic and isotropic elastic properties are then computed and compared with similar properties derived from experimental observations of the anisotropic behavior of bone.

Katz, J. L.; Ukraincik, K.

1971-01-01

248

Osteopontin, osteocalcin and OB-cadherin expression in Synthetic nanohydroxyapatite vs bovine hydroxyapatite cultured Osteoblastic-like cells.  

PubMed

Calcium phosphate ceramics have been applied in bone replacement for several decades due to their excellent biocompatibility, bioactivity, osteo-conductivity and mechanical strength. Several studies have demonstrated that porous hydroxyapatite (HA) is an excellent scaffold for osteogenic proliferation and differentiation of the osteoprogenitor cells. However, different methods of synthesis and production of HA ceramic-based materials may have considerable effect on the physical and biological properties. In the present work, two hydroxyapatite-based materials, a natural hydroxyapatite ceramic of bovine origin and a synthetic nano-cristalline hydroxyapatite were tested in vitro with MG63 cell line. The results displayed that both the materials demonstrated a good biocompatibility. The immunocytochemical stain revealed a different positivity of the osteogenic markers between the cultures with the biomaterials, and the control culture. Western blot data confirmed the immunocytochemical stain. Both the materials tested in the present study demonstrated a good biocompatibility with the osteoblastic cells allowing, at the same time, the osteogenic differentiation, and they may be useful in clinical use. PMID:25316140

Santarelli, A; Mascitti, M; Orsini, G; Memè, L; Rocchetti, R; Tiriduzzi, P; Sampalmieri, F; Putignano, A; Procaccini, M; Lo Muzio, L; Bambini, F

2014-01-01

249

Cemented cup stability during lever-out testing after acetabular bone impaction grafting with bone graft substitutes mixes containing morselized cancellous bone and tricalcium phosphate--hydroxyapatite granules  

Microsoft Academic Search

Bone defects after failed total hip arthroplasty can be reconstructed with impacted morselized bone grafts and a cemented cup. In the near future the amount of bone grafts available for surgical purposes will be insufficient. Ceramic calcium phosphates [tricalcium phosphate (TCP) and hydroxyapatite (HA)] have been widely considered as potential bone graft substitutes or bone graft extenders. In the past,

J. J. C. Arts; B. W. Schreurs; P. Buma; N. J. J. Verdonschot

2005-01-01

250

Mechanical properties of morcellised bone graft with the addition of hydroxyapatite.  

PubMed

Mixtures of morcellised bone graft (MBG) and hydroxyapatite (HA) are frequently used in revision arthroplasty surgery. However, the changes in the mechanical properties from adding HA to MBG are unknown. This study used a uniaxial compression test to replicate impaction bone grafting and subsequent early postoperative weightbearing to investigate the effect of adding different proportion of HA to MBG. To achieve this aim, human MBG was subjected to increasing impaction forces and the apparent stiffness and creep for each stress level determined. Subsequently, increasing proportions porous and non porous HA were added to the MBG. The major findings were that the apparent stiffness for MBG increased and the associated creep decreased both with the application of increasing stress and with the addition of increasing proportions of HA. In conclusion, greater proportions of HA in the graft mixture improved the mechanical response compared with MBG impacted under the same force. This improvement replicated the properties of pure MBG under high axial stress. This study indicates that graft mixtures of MBG and HA can be tailormade for patients. The need for less impaction force in MBG:HA mixtures to obtain the same properties as pure MBG may decrease the risk of intraoperative fracture. PMID:24390340

McNamara, I; Howard, J; Rayment, A; Schalk, R; Brooks, R; Best, S; Rushton, N

2014-02-01

251

Effect of hydroxyapatite nanocrystals functionalized with lactoferrin in osteogenic differentiation of mesenchymal stem cells.  

PubMed

Lactoferrin (LF) is a bioactive glycoprotein that became recently interesting in the field of bone regeneration for its modulatory effect on bone cells. On the basis of this evidence this work aims to functionalize biomimetic hydroxyapatite (HA) nanocrystals with LF to study their effect on osteogenic differentiation of mesenchymal stem cells (MSCs). The orientation of LF on the HA surface was analyzed by spectroscopic and thermal techniques. Three samples with different amounts of LF attached to HA nanocrystals were tested in vitro. The combined effect of HA and LF on MSC proliferation and morphology, alkaline phosphatase (ALP) activity, and gene expression were evaluated at different time points. The sample with the lowest LF amount showed the best bioactivity probably due to the formation of a single layer of protein with a better molecular orientation. Coupling of HA-LF did not affect cell proliferation and morphology, while analysis of HA-LF on ALP activity and messenger RNA expression of the selected genes, demonstrated the role of HA-LF in the induction of osteogenic markers. HA-LF represents a promising system to be used to manufacture bioactive functional materials in tissue engineering (as scaffolds, injectable cements, or coatings for metallic implants) with enhanced anabolic activity to treat bone diseases. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 103A: 224-234, 2015. PMID:24639083

Montesi, Monica; Panseri, Silvia; Iafisco, Michele; Adamiano, Alessio; Tampieri, Anna

2015-01-01

252

First-principles study of the adsorption of lysine on hydroxyapatite (1 0 0) surface  

NASA Astrophysics Data System (ADS)

The adsorption of lysine (Lys) on hydroxyapatite (HA) (1 0 0) surface was studied using density functional theory calculations within the generalized gradient approximation framework. The optimal adsorption pattern was identified from a number of interactive Lys-HA structures. The carbonyl-O, amine-H and C?-H atoms are active sites in Lys that interact directly with the Ca ion and phosphate-O atoms on the HA (1 0 0) surface, respectively. Multiple interactions were noted between Lys and HA surface. The adsorption is mainly stabilized by the Casbnd O ionic bonding, followed by hydrogen bond and/or van der Waals interaction between phosphate-O and Lys-HA. Both the Lys and HA surface structures are subjected to some changes upon adsorption. The zwitterionic form of Lys was found more stable on the HA (1 0 0) surface than its neutral form. Our calculations reveal the structural characteristics and their variations for the Lys-HA systems, which are essential for understanding the interaction mechanism of biomolecules with inorganic biomaterials.

Lou, Zhaoyang; Zeng, Qun; Chu, Xiang; Yang, Fang; He, Duanwei; Yang, Mingli; Xiang, Mingli; Zhang, Xingdong; Fan, Hongsong

2012-03-01

253

Hydroxyapatite crystallinity does not affect the repair of critical size bone defects  

PubMed Central

Objective The physicochemical properties of hydroxyapatite (HA) granules were observed to affect the biological behavior of graft materials. The aim of this work was to analyze the tissue response of two HA granules with different crystallinity and Ca/P ratio in vivo. Material and Methods The HA granules were produced in the Biomaterials Laboratory (COPPE/UFRJ). The testing materials were HA granules presenting a Ca/P molar ratio of 1.60 and 28% crystallinity (HA-1), and a Ca/P molar ratio of 1.67 and 70% crystallinity (HA-2). Both HAs were implanted into a critical-size calvaria rat defects. Results To note, in the control group, the bone defects were filled with blood clot only. Descriptive and histomorphometric analyses after 1, 3, and 6 months postoperatively showed mild inflammatory infiltrate, mainly comprising macrophage-like and multinucleated giant cells, and an increase in the volume density of the fibrous tissues (p<0.05), which was in contrast to the similar volume density of the newly formed bone and biomaterials in relation to the control group. Conclusion Thus, we concluded that HA-1 and HA-2 are biocompatible and non-degradable, and that crystallinity does not affect bone repair of critical size defects. PMID:21655775

CONZ, Marcio Baltazar; GRANJEIRO, José Mauro; SOARES, Gloria de Almeida

2011-01-01

254

Quantification of the binding affinity of a specific hydroxyapatite binding peptide.  

PubMed

The genesis of bone and teeth involves highly coordinated processes, which involve multiple cell types and proteins that direct the nucleation and crystallization of inorganic hydroxyapatite (HA). Recent studies have shown that peptides mediate the nucleation process, control HA microstructure or even inhibit HA mineralization. Using phage display technology, a short peptide was identified that binds to crystalline HA and to HA-containing domains of human teeth with chemical and morphological specificity. However, the binding affinity and specific amino acids that significantly contribute to this interaction require further investigation. In this study, we employ a microfluidic chip based surface plasmon resonance imaging (SPRi) technique to quantitatively measure peptide affinity by fabricating a novel 4 layer HA SPR sensor. We find the peptide (SVSVGMKPSPRPGGGK) binds with relatively high affinity (K(D) = 14.1 microM +/- 3.8 microM) to HA. The independently measured amino acid fragment SVSV seems to impart a significant contribution to this interaction while the MKPSP fragment may provide a conformational dependent component that enhances the peptides affinity but by itself shows little specificity in the current context. These data show that together, the two moieties promote a stronger synergistic binding interaction to HA than the simple combination of the individual components. PMID:20106520

Weiger, Michael C; Park, Jung Jin; Roy, Marc D; Stafford, Christopher M; Karim, Alamgir; Becker, Matthew L

2010-04-01

255

POROUS WALL, HOLLOW GLASS MICROSPHERES  

SciTech Connect

Hollow Glass Microspheres (HGM) is not a new technology. All one has to do is go to the internet and Google{trademark} HGM. Anyone can buy HGM and they have a wide variety of uses. HGM are usually between 1 to 100 microns in diameter, although their size can range from 100 nanometers to 5 millimeters in diameter. HGM are used as lightweight filler in composite materials such as syntactic foam and lightweight concrete. In 1968 a patent was issued to W. Beck of the 3M{trademark} Company for 'Glass Bubbles Prepared by Reheating Solid Glass Particles'. In 1983 P. Howell was issued a patent for 'Glass Bubbles of Increased Collapse Strength' and in 1988 H. Marshall was issued a patent for 'Glass Microbubbles'. Now Google{trademark}, Porous Wall, Hollow Glass Microspheres (PW-HGMs), the key words here are Porous Wall. Almost every article has its beginning with the research done at the Savannah River National Laboratory (SRNL). The Savannah River Site (SRS) where SRNL is located has a long and successful history of working with hydrogen and its isotopes for national security, energy, waste management and environmental remediation applications. This includes more than 30 years of experience developing, processing, and implementing special ceramics, including glasses for a variety of Department of Energy (DOE) missions. In the case of glasses, SRS and SRNL have been involved in both the science and engineering of vitreous or glass based systems. As a part of this glass experience and expertise, SRNL has developed a number of niches in the glass arena, one of which is the development of porous glass systems for a variety of applications. These porous glass systems include sol gel glasses, which include both xerogels and aerogels, as well as phase separated glass compositions, that can be subsequently treated to produce another unique type of porosity within the glass forms. The porous glasses can increase the surface area compared to 'normal glasses of a 1 to 2 order of magnitude, which can result in unique properties in areas such as hydrogen storage, gas transport, gas separations and purifications, sensors, global warming applications, new drug delivery systems and so on. One of the most interesting porous glass products that SRNL has developed and patented is Porous Wall, Hollow Glass Microspheres (PW-HGMs) that are being studied for many different applications. The European Patent Office (EPO) just recently notified SRS that the continuation-in-part patent application for the PW-HGMs has been accepted. The original patent, which was granted by the EPO on June 2, 2010, was validated in France, Germany and the United Kingdom. The microspheres produced are generally in the range of 2 to 100 microns, with a 1 to 2 micron wall. What makes the SRNL microspheres unique from all others is that the team in Figure 1 has found a way to induce and control porosity through the thin walls on a scale of 100 to 3000 {angstrom}. This is what makes the SRNL HW-HGMs one-of-a-kind, and is responsible for many of their unique properties and potential for various applications, including those in tritium storage, gas separations, H-storage for vehicles, and even a variety of new medical applications in the areas of drug delivery and MRI contrast agents. SRNL Hollow Glass Microspheres, and subsequent, Porous Wall, Hollow Glass Microspheres are fabricated using a flame former apparatus. Figure 2 is a schematic of the apparatus.

Sexton, W.

2012-06-30

256

Preparation of magnetite dextran microspheres by ultrasonication  

NASA Astrophysics Data System (ADS)

An improved method of preparing magnetite-dextran microspheres by ultrasonication is proposed. Several parameters were evaluated and the characteristics of the microspheres investigated by scanning electron microscope (SEM), atomic force microscope (AFM), particle size analyzer and magnetometer. The results show that the initial Fe/dextran ratio is the most effective parameter for both the size and the magnetic properties.

Xia, Zefeng; Wang, Guobin; Tao, Kaixiong; Li, Jianxing

2005-05-01

257

Polarization conversion in a silica microsphere  

E-print Network

We experimentally demonstrate controlled polarization-selective phenomena in a whispering gallery mode resonator. We observed efficient (approx. 75%) polarization conversion of light in a silica microsphere coupled to a tapered optical fiber, optimizing the polarization of the light propagating along the fiber. We present a simple model treating the microsphere as a ring resonator to explain the observed behavior.

Bianucci, P; Robertson, J W; Shvets, G; Shih, C K

2007-01-01

258

Microsphere estimates of blood flow: Methodological considerations  

SciTech Connect

The microsphere technique is a standard method for measuring blood flow in experimental animals. Sporadic reports have appeared outlining the limitations of this method. In this study the authors have systematically assessed the effect of blood withdrawals for reference sampling, microsphere numbers, and anesthesia on blood flow estimates using radioactive microspheres in dogs. Experiments were performed on 18 conscious and 12 anesthetized dogs. Four blood flow estimates were performed over 120 min using 1 {times} 10{sup 6} microspheres each time. The effects of excessive numbers of microspheres pentobarbital sodium anesthesia, and replacement of volume loss for reference samples with dextran 70 were assessed. In both conscious and anesthetized dogs a progressive decrease in gastric mucosal blood flow and cardiac output was observed over 120 min. This was also observed in the pancreas in conscious dogs. The major factor responsible for these changes was the volume loss due to the reference sample withdrawals. Replacement of the withdrawn blood with dextran 70 led to stable blood flows to all organs. The injection of excessive numbers of microspheres did not modify hemodynamics to a greater extent than did the injection of 4 million microspheres. Anesthesia exerted no influence on blood flow other than raising coronary flow. The authors conclude that although blood flow to the gastric mucosa and the pancreas is sensitive to the minor hemodynamic changes associated with the microsphere technique, replacement of volume loss for reference samples ensures stable blood flow to all organs over a 120-min period.

von Ritter, C.; Hinder, R.A.; Womack, W.; Bauerfeind, P.; Fimmel, C.J.; Kvietys, P.R.; Granger, D.N.; Blum, A.L. (Univ. of the Witwatersrand, Johannesburg (South Africa) Louisianna State Univ. Medical Center, Shreveport (USA) Universitaire Vaudois (Switzerland))

1988-02-01

259

The Effect of Partial Coating with Hydroxyapatite on Bone Remodeling in Relation to Porous-coated Titanium-alloy Dental Implants in the Dog  

Microsoft Academic Search

For inhibition of crestal bone resorption due to stress shielding and disuse atrophy, an hydroxyapatite (HA) plasma coating was added to the coronal portion of partially porous-coated endosseous dental implants. These implants, as well as control non-HA-coated implants were placed in healed mandibular premolar extraction sites in dogs for a 72-week period of function. Histological examination showed that both implant

R. M. Pilliar; D. A. Deporter; P. A. Watson; M. Pharoah; M. Chipman; N. Valiquette; S. Carter; K. De Groot

1991-01-01

260

On the structural, mechanical, and biodegradation properties of HA/?-TCP robocast scaffolds.  

PubMed

Hydroxyapatite/?-tricalcium phosphate (HA/?-TCP) composite scaffolds have shown great potential for bone-tissue engineering applications. In this work, ceramic scaffold with different HA/?-TCP compositions (pure HA, 60HA/40?-TCP, and 20HA/80?-TCP) were fabricated by a robotic-assisted deposition (robocasting) technique using water-based hydrogel inks. A systematic study was conducted to investigate the porosity, mechanical property, and degradation of the scaffolds. Our results indicate that, at a similar volume porosity, the mechanical strength of the sintered scaffolds increased with the decreasing rod diameter. The compressive strength of the fabricated scaffolds (porosity ? 25-80 vol %) varied between ?3 and ?50 MPa, a value equal or higher than that of human cancellous bone (2-12 MPa). Although there was a slight increase of Ca and P ions in water after 5 month, no noticeable degradation of the scaffolds in SBF or water was observed. Our findings from this work indicate that composite calcium phosphate scaffolds with customer-designed chemistry and architecture may be fabricated by a robotic-assisted deposition method. PMID:23650043

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

2013-10-01

261

Improving mechanical and biological properties of macroporous HA scaffolds through composite coatings.  

PubMed

Interconnected porous hydroxyapatite (HA) scaffolds are widely used for bone repair and replacement, owing to their ability to support the adhesion, transfer, proliferation and differentiation of cells. In the present study, the polymer impregnation approach was adopted to produce porous HA scaffolds with three-dimensional (3D) porous structures. These scaffolds have an advantage of highly interconnected porosity (approximately 85%) but a drawback of poor mechanical strength. Therefore, the as-prepared HA scaffolds were lined with composite polymer coatings in order to improve the mechanical properties and retain its good bioactivity and biocompatibility at the same time. The composite coatings were based on poly(D,L-lactide) (PDLLA) polymer solutions, and contained single component or combination of HA, calcium sulfate (CS) and chondroitin sulfate (ChS) powders. The effects of composite coatings on scaffold porosity, microstructure, mechanical property, in vitro mineralizing behavior, and cell attachment of the resultant scaffolds were investigated. The results showed that the scaffolds with composite coatings resulted in significant improvement in both mechanical and biological properties while retaining the 3D interconnected porous structure. The in vitro mineralizing behaviors were mainly related to the compositions of CS and ChS powders in the composite coatings. Excellent cell attachments were observed on the pure HA scaffold as well as the three types of composite scaffolds. These composite scaffolds with improved mechanical properties and bioactivities are promising bone substitutes in tissue engineering fields. PMID:19679453

Zhao, J; Lu, X; Duan, K; Guo, L Y; Zhou, S B; Weng, J

2009-11-01

262

Induction Plasma Sprayed Nano Hydroxyapatite Coatings on Titanium for Orthopaedic and Dental Implants  

PubMed Central

This paper reports preparation of a highly crystalline nano hydroxyapatite (HA) coating on commercially pure titanium (Cp-Ti) using inductively coupled radio frequency (RF) plasma spray and their in vitro and in vivo biological response. HA coatings were prepared on Ti using normal and supersonic plasma nozzles at different plate powers and working distances. X-ray diffraction (XRD) and Fourier transformed infrared spectroscopic (FTIR) analysis show that the normal plasma nozzle lead to increased phase decomposition, high amorphous calcium phosphate (ACP) phase formation, and severe dehydroxylation of HA. In contrast, coatings prepared using supersonic nozzle retained the crystallinity and phase purity of HA due to relatively short exposure time of HA particles in the plasma. In addition, these coatings exhibited a microstructure that varied from porous and glassy structure at the coating-substrate interface to dense HA at the top surface. The microstructural analysis showed that the coating was made of multigrain HA particles of ~200 nm in size, which consisted of recrystallized HA grains in the size range of 15– 20 nm. Apart from the type of nozzle, working distance was also found to have a strong influence on the HA phase decomposition, while plate power had little influence. Depending on the plasma processing conditions, a coating thickness between 300 and 400 ?m was achieved where the adhesive bond strengths were found to be between 4.8 MPa to 24 MPa. The cytotoxicity of HA coatings was examined by culturing human fetal osteoblast cells (hFOB) on coated surfaces. In vivo studies, using the cortical defect model in rat femur, evaluated the histological response of the HA coatings prepared with supersonic nozzle. After 2 weeks of implantation, osteoid formation was evident on the HA coated implant surface, which could indicate early implant- tissue integration in vivo. PMID:21552358

Roy, Mangal; Bandyopadhyay, Amit; Bose, Susmita

2011-01-01

263

Titania-hydroxyapatite nanocomposite coatings support human mesenchymal stem cells osteogenic differentiation.  

PubMed

In addition to mechanical and chemical stability, the third design goal of the ideal bone-implant coating is the ability to support osteogenic differentiation of mesenchymal stem cells (MSCs). Plasma-sprayed TiO(2)-based bone-implant coatings exhibit excellent long-term mechanical properties, but their applications in bone implants are limited by their bioinertness. We have successfully produced a TiO(2) nanostructured (grain size <50 nm) based coating charged with 10% wt hydroxyapatite (TiO(2)-HA) sprayed by high-velocity oxy-fuel. On Ti64 substrates, the novel TiO(2)-HA coating bond 153× stronger and has a cohesive strength 4× higher than HA coatings. The HA micro- and nano-sized particles covering the TiO(2)-HA coating surface are chemically bound to the TiO(2) coating matrix, producing chemically stable coatings under high mechanical solicitations. In this study, we elucidated the TiO(2)-HA nanocomposite coating surface chemistry, and in vitro osteoinductive potential by culturing human MSCs (hMSCs) in basal and in osteogenic medium (hMSC-ob). We assessed the following hMSCs and hMSC-ob parameters over a 3-week period: (i) proliferation; (ii) cytoskeleton organization and cell-substrate adhesion; (iii) coating-cellular interaction morphology and growth; and (iv) cellular mineralization. The TiO(2) -HA nanocomposite coatings demonstrated 3× higher hydrophilicity than HA coatings, a TiO(2)-nanostructured surface in addition to the chemically bound HA micron- and nano-sized rod to the surface. hMSCs and hMSC-ob demonstrated increased proliferation and osteoblastic differentiation on the nanostructured TiO(2)-HA coatings, suggesting the TiO(2)-HA coatings nanostructure surface properties induce osteogenic differentiation of hMSC and support hMSC-ob osteogenic potential better than our current golden standard HA coating. PMID:21702080

Dimitrievska, Sashka; Bureau, Martin N; Antoniou, John; Mwale, Fackson; Petit, Alain; Lima, Rogerio S; Marple, Basil R

2011-09-15

264

The importance of amino acid interactions in the crystallization of hydroxyapatite  

PubMed Central

Non-collagenous proteins (NCPs) inhibit hydroxyapatite (HA; Ca5(PO4)3OH) formation in living organisms by binding to nascent nuclei of HA and preventing their further growth. Polar and charged amino acids (AAs) are highly expressed in NCPs, and the negatively charged ones, such as glutamic acid (Glu) and phosphoserine (P-Ser) seem to be mainly responsible for the inhibitory effect of NCPs. Despite the recognized importance of these AAs on the behaviour of NCPs, their specific effect on HA crystallization is still unclear, and controversial results have been reported concerning the efficacy of HA inhibition of positively versus negatively charged AAs. We focused on a positively charged (arginine, Arg) and a negatively charged (Glu) AA, and their combination in the same solution. We studied their inhibitory effect on HA nucleation and growth at physiological temperature and pH and we determined the mechanism by which they can affect HA crystallization. Our results showed a strong inhibitory effect of Arg on HA nucleation; however, Glu was more effective in inhibiting HA crystal growth during the growth stage. The combination of Glu and Arg was less effective in controlling HA nucleation, but it inhibited HA crystal growth. We attributed these differences to the stability of complexes formed between AAs and calcium and phosphate ions at the nucleation stage, and in bonding strength of AAs to HA crystal faces during the growth stage. The AAs also influenced the morphology of synthesized HA. Presence of either Arg or Glu resulted in the formation of spherulites consisting of preferentially oriented nanoplatelets orientation. This was attributed to kinetic factors favoring growth front nucleation (GFN) mechanism. PMID:23269851

Jahromi, M. Tavafoghi; Yao, G.; Cerruti, M.

2013-01-01

265

Trap state spectroscopy studies and wettability modification of hydroxyapatite nanobioceramics  

NASA Astrophysics Data System (ADS)

Sintered hydroxyapatite coatings on titanium-based implants demonstrate beneficial biocompatibility and osteoconductivity. It has been shown that charged surface states and bulk traps located in the vicinity of the surface of the hydroxyapatite coatings strongly influence wettability properties of the hydroxyapatite and may modify biocompatibility of these nanostructured bioceramics. Combination of high-resolution electron state spectroscopy methods, thermostimulated exoelectron emission, and thermoluminescence methods, applied in this work, have allowed studying electron trap energy spectrum of the hydroxyapatite bioceramics.

Aronov, Daniel; Rosenman, Gil

2007-02-01

266

PLGA/nHA hybrid nanofiber scaffold as a nanocargo carrier of insulin for accelerating bone tissue regeneration  

NASA Astrophysics Data System (ADS)

The development of tissue engineering in the field of orthopedic surgery is booming. Two fields of research in particular have emerged: approaches for tailoring the surface properties of implantable materials with osteoinductive factors as well as evaluation of the response of osteogenic cells to these fabricated implanted materials (hybrid material). In the present study, we chemically grafted insulin onto the surface of hydroxyapatite nanorods (nHA). The insulin-grafted nHAs (nHA-I) were dispersed into poly(lactide-co-glycolide) (PLGA) polymer solution, which was electrospun to prepare PLGA/nHA-I composite nanofiber scaffolds. The morphology of the electrospun nanofiber scaffolds was assessed by field emission scanning electron microscopy (FESEM). After extensive characterization of the PLGA/nHA-I and PLGA/nHA composite nanofiber scaffolds by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction spectroscopy (XRD), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectrometry (EDS), and transmission electron microscopy (TEM), the PLGA/nHA-I and PLGA/nHA (used as control) composite nanofiber scaffolds were subjected to cell studies. The results obtained from cell adhesion, alizarin red staining, and Von Kossa assay suggested that the PLGA/nHA-I composite nanofiber scaffold has enhanced osteoblastic cell growth, as more cells were proliferated and differentiated. The fact that insulin enhanced osteoblastic cell proliferation will open new possibilities for the development of artificial scaffolds for bone tissue regeneration.

Haider, Adnan; Gupta, Kailash Chandra; Kang, Inn-Kyu

2014-06-01

267

PLGA/nHA hybrid nanofiber scaffold as a nanocargo carrier of insulin for accelerating bone tissue regeneration  

PubMed Central

The development of tissue engineering in the field of orthopedic surgery is booming. Two fields of research in particular have emerged: approaches for tailoring the surface properties of implantable materials with osteoinductive factors as well as evaluation of the response of osteogenic cells to these fabricated implanted materials (hybrid material). In the present study, we chemically grafted insulin onto the surface of hydroxyapatite nanorods (nHA). The insulin-grafted nHAs (nHA-I) were dispersed into poly(lactide-co-glycolide) (PLGA) polymer solution, which was electrospun to prepare PLGA/nHA-I composite nanofiber scaffolds. The morphology of the electrospun nanofiber scaffolds was assessed by field emission scanning electron microscopy (FESEM). After extensive characterization of the PLGA/nHA-I and PLGA/nHA composite nanofiber scaffolds by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction spectroscopy (XRD), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectrometry (EDS), and transmission electron microscopy (TEM), the PLGA/nHA-I and PLGA/nHA (used as control) composite nanofiber scaffolds were subjected to cell studies. The results obtained from cell adhesion, alizarin red staining, and Von Kossa assay suggested that the PLGA/nHA-I composite nanofiber scaffold has enhanced osteoblastic cell growth, as more cells were proliferated and differentiated. The fact that insulin enhanced osteoblastic cell proliferation will open new possibilities for the development of artificial scaffolds for bone tissue regeneration. PMID:25024679

2014-01-01

268

In vitro anti-bacterial and biological properties of magnetron co-sputtered silver-containing hydroxyapatite coating  

Microsoft Academic Search

Bacterial infection after implant placement is a significant rising complication. In order to reduce the incidence of implant-associated infections, several biomaterial surface treatments have been proposed. In this study, the effect of in vitro antibacterial activity and in vitro cytotoxicity of co-sputtered silver (Ag)-containing hydroxyapatite (HA) coating was evaluated. Deposition was achieved by a concurrent supply of 10W to the

W. Chen; Y. Liu; H. S Courtney; M. Bettenga; C. M. Agrawal; J. D. Bumgardner; J. L. Ong

2006-01-01

269

The facile and low temperature synthesis of nanophase hydroxyapatite crystals using wet chemistry.  

PubMed

A simple and facile wet chemistry route was used to synthesize nanophase hydroxyapatite (HaP) crystals at low temperature. The synthesis was carried out at a pH of 11.0 and at a temperature of 37°C. The resulting samples were washed several times and subjected to further analysis. XRD studies revealed that the HaP crystals were polycrystalline in nature with a crystallite size of ~15-60 ± 5 nm. SEM-EDXA images confirmed the presence of calcium (Ca), phosphorous (P), and oxygen (O) peaks. Likewise, FTIR confirmed the presence of characteristic phosphate and hydroxyl peaks in samples. Lastly, HRTEM images clearly showed distinctive lattice fringes positioned in the 100 and 002 planes. TGA analysis shows that HaP crystals can withstand higher calcination temperatures and are thermally stable. PMID:24433898

Dhand, Vivek; Rhee, K Y; Park, Soo-Jin

2014-03-01

270

A novel jet-based nano-hydroxyapatite patterning technique for osteoblast guidance  

PubMed Central

Surface topography is well known to play a crucial role in influencing cellular responses to an implant material and is therefore important in bone tissue regeneration. A novel jet-based patterning technique, template-assisted electrohydrodynamic atomization spraying, was recently devised to control precisely the surface structure as well as its dimensions. In the present study, a detailed investigation of this patterning process was carried out. A range of nano-hydroxyapatite (nHA) line-shaped patterns <20 µm in width were successfully deposited on a commercially pure Ti surface by controlling the flow of an nHA suspension in an electric field. In vitro studies showed that the nHA patterns generated are capable of regulating the human osteoblast cell attachment and orientation. PMID:19493897

Li, Xiang; Koller, Garrit; Huang, Jie; Di Silvio, Lucy; Renton, Tara; Esat, Minoo; Bonfield, William; Edirisinghe, Mohan

2010-01-01

271

The composite of hydroxyapatite and calcium sulphate: a review of preclinical evaluation and clinical applications.  

PubMed

Recent publications have shown that the combination of ?-calcium sulfate hemihydrate, the densest form of hydrates and hydroxyapatite (HA) particles gives good clinical outcome in various applications. It has large potential as bone substitute since the material transforms to bone throughout the entire volume and not only by creeping substitution, from the surface toward the inside. Release of important proteins for osteogenesis has been observed around implanted material and is speculated to be due to fast dissolution of the calcium sulfate phase in combination with the osteoconductive and bioactive nature of HA. In diabetic foot infection, the osteoconductive HA/calcium sulfate material has been successfully used loaded with antibiotics and since it is injectable, the application is minimally invasive, easy and precise. It is a bone substitute for the future. PMID:24053255

Nilsson, Malin; Zheng, Ming H; Tägil, Magnus

2013-09-01

272

Behavior of Plasma-Sprayed Hydroxyapatite Coatings onto Carbon/carbon Composites in Simulated Body Fluid  

NASA Astrophysics Data System (ADS)

Two types of hydroxyapatite (HA) coatings onto carbon/carbon composite (C/C composites) substrates, deposited by plasma spraying technique, were immersed in a simulated body fluid (SBF) in order to determine their behavior in conditions similar to the human blood plasma. Calcium ion concentration, pH value, microstructure, and phase compositions were analyzed. Results demonstrated that both the crystal Ca-P phases or the amorphous HA do dissolve slightly, and the dissolution of CaO phases in SBF was evident after 1 day of soaking. The calcium-ion concentration was decreased and the pH value of SBF was increased with the increasing of the immersing time. The precipitation was mainly composed of HA, which was verified by X-ray diffraction (XRD) and electron-probe microanalyzer.

Sui, Jin-Ling; Bo, Wu; Hai, Zhou; Cao, Ning; Li, Mu-Sen

273

Electrophoretic deposition and electrochemical behavior of novel graphene oxide-hyaluronic acid-hydroxyapatite nanocomposite coatings  

NASA Astrophysics Data System (ADS)

Novel ternary graphene oxide-hyaluronic acid-hydroxyapatite (GO-HY-HA) nanocomposite coatings were prepared on Ti substrate using anodic electrophoretic deposition (EPD). Hyaluronic acid was employed as charging additive and dispersion agent during EPD. The kinetics and mechanism of the deposition, and the microstructure of the coated samples were investigated using scanning electron microscopy, X-ray diffraction, Raman spectrum, thermo-gravimetric analysis, and microscopic Fourier transform infrared analysis. The results showed that the addition of GO sheets into the HY-HA suspensions could increase the deposition rate and inhibit cracks creation and propagation in the coatings. The corrosion resistant of the resulting samples were evaluated using potentiodynamic polarization method in simulated body fluid, and the GO-HY-HA coatings could effectively improve the anti-corrosion property of the Ti substrate.

Li, Ming; Liu, Qian; Jia, Zhaojun; Xu, Xuchen; Shi, Yuying; Cheng, Yan; Zheng, Yufeng; Xi, Tingfei; Wei, Shicheng

2013-11-01

274

The effect of hydroxyapatite nanocrystals on osseointegration of titanium implants: an in vivo rabbit study.  

PubMed

Osseointegration is dependent on implant surface characteristics, including surface chemistry and topography. The presence of nanosized calcium phosphates on the implant surface is interesting to investigate since they affect both the nanotopography and surface chemistry, forming a bone mineral resembling surface. In this work, the osseointegration of titanium implants with and without the presence of hydroxyapatite (HA) nanocrystals has been evaluated in vivo. The integration was examined using removal torque measurements and real-time polymerase chain reaction (RT-PCR) analysis. The study was performed using two healing time points, 3 and 12 weeks. The results showed that the torque needed to remove the implants was insignificant between the non- and HA-coated implants, both at weeks 3 and 12. The RT-PCR, however, showed significant differences for osteoblast, osteoclast, and proinflammation markers when HA nanocrystals were present. PMID:24563651

Breding, Karin; Jimbo, Ryo; Hayashi, Mariko; Xue, Ying; Mustafa, Kamal; Andersson, Martin

2014-01-01

275

Controlled RGD Peptide Adsorption on Aggregation-Free, Size-Selected Hydroxyapatite Nanoparticle Substrates  

NASA Astrophysics Data System (ADS)

Numerous studies of cell attachment, differentiation, and proliferation have been carried out on nanostructured hydroxyapatite (HA) surfaces with cell adhesive peptides containing the RGD (Arg-Gly-Asp) motif. Although these studies have yielded useful insights into the role of RGD peptides in cell-HA biomaterial interactions, the heterogeneity of typical nanophase HA materials makes it difficult to decouple the effects of nanotopography and biochemical cues. In this work we have used aggregation-free, size-controlled HA nanoparticles with mean size in the 20-70 nm range, synthesized by gas-phase laser ablation and deposited on atomically flat bioinert substrates that may help overcome this challenge. Nanoparticle deposits with adjustable number concentration were characterized by transmission electron microscopy, atomic force microscopy, and X-ray diffraction. RGD peptides modified by the addition of a polyglutamate sequence and a fluorescent conjugate, were coated onto the HA nanoparticle substrates. Intensity histograms of fluorescent microscopy images show that peptide adsorption on the substrates scales with the concentration of HA nanoparticles. High HA nanoparticle concentrations also lead to peptide clustering tunable in the 100-1200 cm-2.

Bapat, Parimal; Culpepper, Bonnie; Bellis, Susan; Camata, Renato

2012-10-01

276

Synthesis and characterization of hydroxyapatite with different crystallinity: effects on protein adsorption and release.  

PubMed

Increasing demand exists for the development of a tissue-engineered alternative in the repair of nonunion and critical-sized bone defects. The delivery of osteoinductive proteins, such as bone morphogenetic proteins (BMPs), to replicate physiological bone-healing process appears a logical and promising option, but is currently limited in its clinical application due to lack of a suitable drug carrier. The study aimed to investigate the effects of the crystallinity of hydroxyapatite (HA) drug carrier on adsorption of proteins onto and their release from the carrier. HA samples with different crystallinities were synthesized under controlled conditions, that is, pH, temperature, and maturation time, and characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and surface area analyzer. Results demonstrated that both bovine serum albumin (BSA) and cytochrome C had a greater tendency to bind onto amorphous calcium phosphate (ACP) than crystalline HA, and the adsorption rate was correlated oppositely with the HA crystallinity. For both BSA and cytochrome C, the release kinetics of protein from HA depended on the crystallinity of HA, in which ACP had the highest release rate at 74%, whereas only 15% of proteins were released from the highly crystalline HA over a 14-day period. Burst release within 12 h of incubation was observed for all groups. PMID:22419559

Lee, Wing-Hin; Zavgorodniy, Alexander V; Loo, Ching-Yee; Rohanizadeh, Ramin

2012-06-01

277

Porous alumina-hydroxyapatite composites through protein foaming-consolidation method.  

PubMed

This report presents physical characterization and cell culture test of porous alumina-hydroxyapatite (HA) composites fabricated through protein foaming-consolidation technique. Alumina and HA powders were mixed with yolk and starch at an adjusted ratio to make slurry. The resulting slip was poured into cylindrical shaped molds and followed by foaming and consolidation via 180 °C drying for 1 h. The obtained green bodies were burned at 600 °C for 1 h, followed by sintering at temperatures of 1200-1550 °C for 2 h. Porous alumina-HA bodies with 26-77 vol.% shrinkage, 46%-52% porosity and 0.1-6.4 MPa compressive strength were obtained. The compressive strength of bodies increased with the increasing sintering temperatures. The addition of commercial HA in the body was found to increase the compressive strength, whereas the case is reverse for sol-gel derived HA. Biocompatibility study of porous alumina-HA was performed in a stirred tank bioreactor using culture of Vero cells. A good compatibility of the cells to the porous microcarriers was observed as the cells attached and grew at the surface of microcarriers at 8-120 cultured hours. The cell growth on porous alumina microcarrier was 0.015 h(-1) and increased to 0.019 h(-1) for 0.3 w/w HA-to-alumina mass ratio and decreased again to 0.017 h(-1) for 1.0 w/w ratio. PMID:22402156

Sopyan, I; Fadli, A; Mel, M

2012-04-01

278

Comparison of Nano-Hydroxyapatite and Sodium Fluoride Mouthrinse for Remineralization of Incipient Carious Lesions  

PubMed Central

Objective: Dental caries is an infectious disease that can be prevented in several ways. The aim of this study was to compare the efficacy of sodium fluoride mouthrinse and nano- hydroxyapatite (nano-HA) for the remineralization of incipient caries. Materials and Methods: After obtaining different concentrations of nano-HA (0-2-5-10%), 60 sound premolars fixed in acrylic blocks were coated with nail polish except for one surface. Ten teeth (control group) were stored in distilled water and the remaining 50 samples were demineralized by immersion in 13 ml of 0.1 M lactic acid and 0.2% poly acrylic acid for 48 hours. Their microhardness was then measured and compared to that of the control group. Next, the 50 test teeth were randomly divided into 5 groups of group1 (negative), group 2 (2% nano-HA), group 3 (5% nano-HA), group 4(10% nano-HA) and group 5 (0.2 NAF mouthrinse). The microhardness of the teeth was measured after 12 hours of immersion in the above-mentioned solutions. Data were analyzed using repeated measures analysis of variance (ANOVA). Results: Microhardness of all samples decreased significantly after immersion in the demineralization solution and increased following immersion in nano-HA and NAF mouthrinses; however, this increase was not statistically significant (P=0.711). Conclusion: Nano-HA and NAF mouthrinses can greatly enhance remineralization and increase tooth microhardness.

Haghgoo, Roza; Rezvani, Mohammad Bagher; Salehi Zeinabadi, Mehdi

2014-01-01

279

Carbon Nanotubes in Nanocomposites and Hybrids with Hydroxyapatite for Bone Replacements  

PubMed Central

Hydroxyapatite (HA), as a bone mineral component, has been an attractive bioceramic for the reconstruction of hard tissues. However, its poor mechanical properties, including low fracture toughness and tensile strength, have been a significant challenge to the application of HA for the replacement of load-bearing and/or large bone defects. Among materials studied to reinforce HA, carbon nanotubes (CNTs: single-walled or multiwalled) have recently gained significant attention because of their unprecedented mechanical properties (high strength and toughness) and physicochemical properties (high surface area, electrical and thermal conductivity, and low weight). Here, we review recent studies of the organization of HA-CNTs at the nanoscale, with a particular emphasis on the functionalization of CNTs and their dispersion within an HA matrix and induction of HA mineralization. The organization of CNTs and HA implemented at the nanoscale can further be developed in the form of coatings, nanocomposites, and hybrid powders to enable potential applications in hard tissue reconstruction. PMID:21776341

Shin, Ueon Sang; Yoon, Il-Kyu; Lee, Gil-Su; Jang, Won-Cheoul; Knowles, Jonathan C.; Kim, Hae-Won

2011-01-01

280

Hydrothermal fabrication of hydroxyapatite/chitosan/carbon porous scaffolds for bone tissue engineering.  

PubMed

Porous carbon fiber felts (PCFFs) have great applications in orthopedic surgery because of the strong mechanical strength, low density, high stability, and porous structure, but they are biologically inert. To improve their biological properties, we developed, for the first time, the hydroxyapatite (HA)/chitosan/carbon porous scaffolds (HCCPs). HA/chitosan nanohybrid coatings have been fabricated on PCFFs according to the following stages: (i) deposition of chitosan/calcium phosphate precursors on PCFFs; and (ii) hydrothermal transformation of the calcium phosphate precursors in chitosan matrix into HA nanocrystals. The scanning electron microscopy images indicate that PCFFs are uniformly covered with elongated HA nanoplates and chitosan, and the macropores in PCFFs still remain. Interestingly, the calcium-deficient HA crystals exist as plate-like shapes with thickness of 10-18 nm, width of 30-40 nm, and length of 80-120 nm, which are similar to the biological apatite. The HA in HCCPs is similar to the mineral of natural bone in chemical composition, crystallinity, and morphology. As compared with PCFFs, HCCPs exhibit higher in vitro bioactivity and biocompatibility because of the presence of the HA/chitosan nanohybrid coatings. HCCPs not only promote the formation of bone-like apatite in simulated body fluid, but also improve the adhesion, spreading, and proliferation of human bone marrow stromal cells. Hence, HCCPs have great potentials as scaffold materials for bone tissue engineering and implantation. PMID:24687547

Long, Teng; Liu, Yu-Tai; Tang, Sha; Sun, Jin-Liang; Guo, Ya-Ping; Zhu, Zhen-An

2014-11-01

281

Effect of nano-hydroxyapatite on the axonal guidance growth of rat cortical neurons  

NASA Astrophysics Data System (ADS)

Nanomaterials such as carbon nanotubes (CNT) can improve axonal connecting in a target direction during regeneration, however, it is limited by the neurotoxicity of CNT. Here we investigate the possible protective effect of nano-hydroxyapatite (n-HA) against nerve injury, as well as CNT in cultured rat cortical neurons. In this study the nanomaterials were characterized by X-Ray diffractometry (XRD) and atomic force microscopy (AFM) analysis. Our results showed that axonal migration and extension were increased significantly after n-HA treatment by immunocytochemistry assay. The patch clamp assay results showed that n-HA acts protectively after nerve injury, which inhibited the average amplitude and frequency of excitatory postsynaptic currents (EPSCs). n-HA is not neurotoxic for the electrophysiology activity of cells. To find the effect of n-HA on axonal guidance growth in the cultured cortical neurons, Netrin 1, one of the axonal guidance cues, was determined by RT-PCR and western blot assay. Compared to the control group, n-HA down-regulated the mRNA level of netrin 1, and moreover, the expression of netrin 1 decreased significantly in the cells. n-HA caused the axonal guidance growth to be mediated by netrin 1 during nerve regeneration. Therefore, the data from the present study provided a new approach for the therapy or prevention of nerve injury.

Liu, Meili; Zhou, Gang; Song, Wei; Li, Ping; Liu, Haifeng; Niu, Xufeng; Fan, Yubo

2012-05-01

282

Hydroxyapatite thin films deposited onto uncoated and (Ti,Al, V)N-coated Ti alloys.  

PubMed

Plasma-sputtered hydroxyapatite (HA) thin coatings ( approximately 1 microm) were deposited onto uncoated and (TiAlV)N-coated Ti-6Al-4V-alloy substrates at low temperatures. The (TiAlV)N coating interlayer was deposited by reactive sputtering. Depositions were achieved by utilizing unbalanced and balanced magnetrons in a capacitively coupled RF plasma. Characterization of the thermostability, bioerosion resistance, and chemical composition of the coating layer was examined by scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), and Fourier transform infrared spectroscopy (FTIR). The results show that for deposition temperatures as low as 67 degrees C, the crystalline phase of the HA coating still is clearly detectable and that the underlying (TiAlV)N coating can increase the crystallinity and thermostability of the HA coating before and after heat treatment. The thin ( approximately 1 microm) sputtered HA coating shows strong HA characteristic peaks in the FTIR spectra even after a 30-day dissolution test. The experimental results show that a multilayer structure comprised of a bioinert (TiAlV)N and bioactive HA coating has the potential to improve the biocompatibility of implant materials. The bioinert (TiAlV)N coating also may provide a long-term stable interface between bone tissue and an alloy implant after the bioactive HA coating is remodeled by the surrounding tissue. PMID:10397999

Lo, W J; Grant, D M

1999-09-01

283

Osteoblast proliferation on hydroxyapatite coated substrates prepared by right angle magnetron sputtering.  

PubMed

The preparation of hydroxyapatite (HA) coatings via a versatile right-angle magnetron sputtering (RAMS) approach for use as a biomaterial has recently been reported. RAMS coatings show some advantages over conventionally sputtered films in that room temperature deposition yields nanocrystalline and nearly stoichiometric HA coatings under appropriate conditions, thereby avoiding the troublesome post deposition annealing treatment. In this article, we present an exploratory study of the biocompatibility of RAMS HA coatings deposited on metallic substrates. RAMS HA coatings with a thickness around 500nm were prepared on various substrates. X-ray diffraction (XRD) analysis showed that the as-deposited HA coatings were polycrystalline with some strongly preferred orientations. Atomic force microscopy (AFM) results showed that the coatings were rather smooth with surface roughness on the order of 10 nm. X-ray photoelectron spectroscopy (XPS) confirmed that the surface chemistry was nearly stoichiometric. To study the biocompatibility of these coatings, murine pre-osteoblastic MC3T3-E1 cells were seeded onto various substrates. Cell density counts using fluorescence microscopy showed that the best osteoblast proliferation is achieved on an HA RAMS-coated titanium substrate. Additionally, in preliminary studies the influence of Zn, Mg, and Al incorporation in the HA crystal lattice on the in vitro behavior was also evaluated. These experiments demonstrate that RAMS is a promising coating technique for biomedical applications. PMID:19705463

Hong, Zhendong; Mello, Alexandre; Yoshida, Tomohiko; Luan, Lan; Stern, Paula H; Rossi, Alexandre; Ellis, Don E; Ketterson, John B

2010-06-01

284

Preparation and in vitro evaluation of mesoporous hydroxyapatite coated ?-TCP porous scaffolds.  

PubMed

A mesoporous hydroxyapatite (HA) coating was prepared on a ?-tricalcium phosphate (?-TCP) porous scaffold by a sol-gel dip-coating method using the block copolymer Pluronic F127 (EO106PO70EO106) as the template. For application as a bone graft, in vitro cell response and bone-related protein expression of mesoporous HA coated ?-TCP scaffold were investigated, using the non-mesoporous HA coated scaffold as the control group, to evaluate the influence of the mesoporous structure on the biological properties of HA coating. It was found that the increased surface area of the mesoporous HA coating greatly affected the response of MC3T3-E1 osteoblasts and the expression of proteins. An enzyme-linked immunosorbent assay recorded a significantly higher expression of alkaline phosphatase (ALP) and bone sialoprotein (BSP) in the mesoporous group than those in the control group (*p<0.05) after different incubation periods. The introduction of mesopores enhanced the expression of ALP and BSP in the cells grown on the mesoporous HA coatings, on the premise of maintaining the protein expression in a sequence to ensure the correct temporo-spatial expression in osteogenesis. These results indicated that the mesoporous HA coating would provide a good environment for cell growth, suggesting that it could be used as the coating material for the surface modification of the tissue engineering scaffolds. PMID:24094217

Ye, Xinyu; Cai, Shu; Xu, Guohua; Dou, Ying; Hu, Hongtao; Ye, Xiaojian

2013-12-01

285

Electrophoretic deposition of hydroxyapatite-CaSiO3-chitosan composite coatings.  

PubMed

Electrophoretic deposition (EPD) method has been developed for the fabrication of hydroxyapatite (HA)-CaSiO(3) (CS)-chitosan composite coatings for biomedical applications. The use of chitosan enabled the co-deposition of HA and CS particles and offered the advantage of room temperature processing of composite materials. The coating composition was varied by the variation of HA and CS concentrations in the chitosan solutions. Cathodic deposits were obtained as HA-CS-chitosan monolayers, HA-chitosan/chitosan multilayers or functionally graded materials (FGM) containing HA-chitosan and CS-chitosan layers of different composition. The thickness of the individual layers was varied in the range of 0.1-20 microm. The deposition yield was studied at different experimental conditions and compared with the results of modeling. It was shown that the moving boundary model for the two component system can explain the non-linear increase in the deposition yield with increasing HA concentration in chitosan solutions. The obtained coatings were studied by thermogravimetric analysis (TGA), differential thermal analysis (DTA) and scanning electron microscopy (SEM). Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) studies showed that these coatings provided corrosion protection of stainless steel substrates in Ringer's physiological solution. The deposition mechanism and kinetics of deposition have been discussed. PMID:19012892

Pang, Xin; Casagrande, Travis; Zhitomirsky, Igor

2009-02-15

286

Microsphere radioembolization of liver malignancies: current developments.  

PubMed

The worldwide incidence of hepatic malignancies, both primary and secondary, exceeds 1 000 000 new cases each year. The poor prognosis of patients suffering from hepatic malignancies has lead to the development of a liver directed therapy which consists of intra-arterial administration of radioactive particles through a catheter. Yttrium-90 ((90)Y) microspheres are increasingly applied for this purpose, and up to now nearly all clinical experience with radioembolization has been obtained with these microspheres. The response rate is very promising in both patients with primary and metastatic liver malignancies. Currently, two commercially available (90)Y microsphere devices are in use clinically, both as a first-line treatment and in a salvage setting. Unfortunately, the use of a pure beta-emitter like (90)Y hampers acquisition of high quality nuclear images for pre-treatment work-up and follow-up. This issue was addressed by the development of holmium-166 ((166)Ho) and rhenium-188 ((188)Re) microspheres, which emit both beta-particles for therapeutic purposes and gamma-photons for nuclear imaging. Moreover, since holmium is paramagnetic it allows for magnetic resonance imaging. (166)Ho loaded poly(L-lactic acid) microspheres have been thoroughly investigated in a preclinical setting, and recently the first clinical results for (188)Re microspheres were reported. This review provides an overview of the current status and (pre-)clinical developments of radioactive microspheres for treatment of liver malignancies. PMID:19521312

Bult, W; Vente, M A D; Zonnenberg, B A; Van Het Schip, A D; Nijsen, J F M

2009-06-01

287

Development of hydroxyapatite derived from Indian coral.  

PubMed

A simple method of converting the calcium carbonate skeleton of the corals available in the Indian coast into hydroxyapatite granules has been developed. By heating the coral to 900 degrees C, the organic materials were eliminated. Powder X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) were employed to characterize the coral and to optimize the processing parameters as well as to confirm the hydroxyapatite formation. The coral used exhibits the presence of both aragonite and calcite phases (dimorphism). At a temperature of 900 degrees C the coral was found to decompose all the carbonate phases. The pre-heated coral is converted into hydroxyapatite by a chemical exchange reaction with di-ammonium phosphate under hydrothermal conditions. The hydroxyapatite obtained was in powder form and does not contain any impurities. The in vitro solubility test of the apatite granules performed in Gomoris, Michalelis, Sorensens, Ringer's and phosphate buffer of pH 7.2 and de-ionized water indicated the stability of the coralline hydroxyapatite. PMID:8866033

Sivakumar, M; Kumar, T S; Shantha, K L; Rao, K P

1996-09-01

288

Aceclofenac microspheres: quality by design approach.  

PubMed

The purpose of this study was to prepare polymeric microspheres containing aceclofenac by single emulsion [oil-in-water (o/w)] solvent evaporation method. Two biocompatible polymers, ethylcellulose, and Eudragit® RS100 were used in combination. Seven processing factors were investigated by Plackett-Burman design (PBD) in order to enhance the encapsulation efficiency of the microspheres. A Plackett-Burman design was employed by using the Design-Expert® software (Version-8.0.7.1). The resultant microspheres were characterized for their size, morphology, encapsulation efficiency, and drug release. Imaging of particles was performed by field emission scanning electron microscopy. Interaction between the drug and polymers were investigated by Fourier transform infrared (FTIR) spectroscopy, and X-ray powder diffractometry (XRPD). Graphical and mathematical analyses of the design showed that Eudragit® RS100, and polyvinyl alcohol (PVA) were significant negative effect on the encapsulation efficiency and identified as the significant factor determining the encapsulation efficiency of the microspheres. The low magnitudes of error and the significant values of R(2) in the present investigation prove the high prognostic ability of the design. The microspheres showed high encapsulation efficiency (70.15% to 83.82%). The microspheres were found to be discrete, oval with smooth surface. The FTIR analysis confirmed the compatibility of aceclofenac with the polymers. The XRPD revealed the dispersion of drug within microspheres formulation. Perfect prolonged drug release profile over 12h was achieved by a combination of ethylcellulose, and Eudragit® RS100 polymers. In conclusion, polymeric microspheres containing aceclofenac can be successfully prepared using the technique of experimental design, and these results helped in finding the optimum formulation variables for encapsulation efficiency of microspheres. PMID:24433918

Deshmukh, Rameshwar K; Naik, Jitendra B

2014-03-01

289

Plasma Sprayed Hydroxyapatite Coatings: Influence of Spraying Power on Microstructure  

SciTech Connect

The plasma sprayed hydroxyapatite (HA) coatings are used on metallic implants to enhance the bonding between the implant and bone in human body. The coating process was implemented at different spraying power for each spraying condition. The coatings formed from a rapid solidification of molten and partly molten particles that impact on the surface of substrate at high velocity and high temperature. The study was concentrated on different spraying power that is between 23 to 31 kW. The effect of different power on the coatings microstructure was investigated using scanning electron microscope (SEM) and phase composition was evaluated using X-ray diffraction (XRD) analysis. The coatings surface morphology showed distribution of molten, partially melted particles and some micro-cracks. The produced coatings were found to be porous as observed from the cross-sectional morphology. The coatings XRD results indicated the presence of crystalline phase of HA and each of the patterns was similar to the initial powder. Regardless of different spraying power, all the coatings were having similar XRD patterns.

Mohd, S. M.; Abd, M. Z.; Abd, A. N. [Advanced Material Centre (AMREC), SIRIM Bhd, Lot 34, Jalan Hi-Tech 2/4, Kulim Hi-Tech Park, 09000 Kulim (Malaysia)

2010-03-11

290

Preparation and characterization of NiW-nHA composite catalyst for hydrocracking.  

PubMed

The synthesis, characterization and catalytic capability of the NiW-nano-hydroxyapatite (NiW-nHA) composite were investigated in this paper. The NiW-nHA catalyst was prepared by a co-precipitation method. Then Fourier transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD) and energy dispersive spectroscopy (EDX) were used to analyze this material. In addition, the catalytic capacity of the NiW-nHA composite was also examined by FT-IR and gas chromatography (GC). The results of FT-IR analysis indicated that Ni, W and nHA combined closely. TEM observation revealed that this catalyst was needle shaped and the crystal retained a nanometer size. XRD data also suggested that a new phase of CaWO(4) appeared and the lattice parameters of nHA changed in this system. nHA was the carrier of metals. The rates of Ni/W-loading were 73.24% and 65.99% according to the EDX data, respectively. Furthermore, the conversion of 91.88% Jatropha oil was achieved at 360 °C and 3 MPa h(-1) over NiW-nHA catalyst. The straight chain alkanes ranging from C(15) to C(18) were the main components in the production. The yield of C(15)-C(18) alkanes was up to 83.56 wt%. The reaction pathway involved hydrocracking of the C?C bonds of these triglycerides from Jatropha oil. This paper developed a novel non-sulfided catalyst to obtain a "green biofuel" from vegetable oil. PMID:23128670

Zhou, Gang; Hou, Yongzhao; Liu, Lei; Liu, Hongru; Liu, Can; Liu, Jing; Qiao, Huiting; Liu, Wenyong; Fan, Yubo; Shen, Shituan; Rong, Long

2012-12-21

291

Preparation and characterization of NiW-nHA composite catalyst for hydrocracking  

NASA Astrophysics Data System (ADS)

The synthesis, characterization and catalytic capability of the NiW-nano-hydroxyapatite (NiW-nHA) composite were investigated in this paper. The NiW-nHA catalyst was prepared by a co-precipitation method. Then Fourier transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD) and energy dispersive spectroscopy (EDX) were used to analyze this material. In addition, the catalytic capacity of the NiW-nHA composite was also examined by FT-IR and gas chromatography (GC). The results of FT-IR analysis indicated that Ni, W and nHA combined closely. TEM observation revealed that this catalyst was needle shaped and the crystal retained a nanometer size. XRD data also suggested that a new phase of CaWO4 appeared and the lattice parameters of nHA changed in this system. nHA was the carrier of metals. The rates of Ni/W-loading were 73.24% and 65.99% according to the EDX data, respectively. Furthermore, the conversion of 91.88% Jatropha oil was achieved at 360 °C and 3 MPa h-1 over NiW-nHA catalyst. The straight chain alkanes ranging from C15 to C18 were the main components in the production. The yield of C15-C18 alkanes was up to 83.56 wt%. The reaction pathway involved hydrocracking of the C&z.dbd;C bonds of these triglycerides from Jatropha oil. This paper developed a novel non-sulfided catalyst to obtain a ``green biofuel'' from vegetable oil.

Zhou, Gang; Hou, Yongzhao; Liu, Lei; Liu, Hongru; Liu, Can; Liu, Jing; Qiao, Huiting; Liu, Wenyong; Fan, Yubo; Shen, Shituan; Rong, Long

2012-11-01

292

Processing of UHMWPE and HA/UHMWPE nanocomposite for biomedical applications  

NASA Astrophysics Data System (ADS)

Ultrahigh molecular weight polyethylene (UHMWPE) is an implant material for orthopedic implants because of its excellent mechanical properties. However, its applications were limited by the poor processability, particularly its use as matrix materials for bone-analogue. The objective of this work is to process UHMWPE and hydroxyapatite/UHMWPE (HA/UHMWPE) nanocomposites for biomedical applications. UHMWPE was processed by extrusion in a temperature window, in which a metastable polyethylene phase transformation was induced by the elongational flow. Compared with conventional methods, the flow resistance was reduced by the mobile mesophase and the fusion of powder became faster by the improved inter-particle chain diffusion. Pin-on-disc wear tests showed that the as-extruded UHMWPE exhibited less wear loss, smaller wear debris and smoother worn surface, suggesting it has higher wear resistance than conventional sample. HA/UHMWPE nanocomposite was processed by twin-screw extrusion of HA and UHMWPE powder mixture and swelling UHMWPE in a solvent to control the shear viscosity. Microstructure showed that aggregated HA powder was broken down to nano-sized primary particles and dispersed homogeneously by the intensive shear mixing in the extruder. The HA particles and UHMWPE fibrils were intimately contacted because swelling improved the chain mobility of UHMWPE. The composite stiffness was significantly enhanced attributed to the reinforcement effect of HA nano particles to UHMWPE fibrils, Since the toughness of UHMWPE was maintained in the composite, the composite was hot drawn to further increase the strength to that of cortical bone by aligning UHMWPE fibrils along the drawing direction. Biological evaluation indicated that the composite was biocompatible and very bioactive in simulated body fluid immersion. It was shown that the composite with 30% of HA by volume had optimal mechanical and biological properties.

Fang, Liming

293

Syntheses of near-net-shaped monolithic hydroxyapatite and hydroxyapatite-ASTM F75 composites by the oxidation of solid metal-bearing precursors  

NASA Astrophysics Data System (ADS)

A novel powder-metallurgical route was used to fabricate near net-shaped hydroxyapatite, Ca10(PO4)6(OH)2 (HA) and HA+Co-C-Mo composite bodies. Ca and beta-Ca2P 2O7 with Ca/P ˜ 1.67 was intimately mixed by high-energy mechanical alloying, formed into desired shapes by pressing and machining, and then converted into HA with a series of heat treatments: a 600°C annealing in dry O2 completely oxidized calcium within 3 h, and a subsequent annealing at ?1150°C in moist O2 yielded phase-pure HA. The reduction in solid volume associated with the oxidation of calcium (Vm[CaO] < Vm[Ca]) was offset by the increase in solid volume associated with the conversion of CaO and Ca2P2O7 into HA. Thus, the overall dimensional changes upon transformation of Ca+beta-Ca2P 2O7 precursors into HA can be relatively small. A mixture of Co-Cr-Mo powder with the precursor prepared from Ca and beta-Ca 2P2O7, targeted to yield a 75 to 25 volume ratio of Co-Cr-Mo to stoichiometric HA were prepared with the same method but different annealing cycles: annealing at 1150°C in de-oxygenized, flowing Ar resulted in partial densification of the composite bodies, and subsequent annealing at 850°C in a moist O2 atmosphere yielded a composite of Co-Cr-Mo alloy with phase-pure HA. The overall dimensional changes upon transformation of Ca+beta-Ca2P2O7+CO-Cr-Mo precursors into HA/Co-Cr-Mo composite were relatively small. In this thesis, the phase and microstructural evolution at various stages of transformation to monolithic HA and to HA/Co-Cr-Mo alloy composites are discussed. Planar reaction couples and powder compacts of CaO-TCP were prepared to study the kinetics for HA formation from CaO+TCP. Pt strips were used in the planar reaction couples as inert markers. These reaction couples were heated at 1150°C for various times in moist O2. The results of powder compact analyses fits Carter's model, which indicated that the rate of HA conversion from CaO and TCP is limited by solid state diffusion of Ca 2+ and/or OH- through the HA layer.

Saw, Eaden

294

SRNL POROUS WALL GLASS MICROSPHERES  

SciTech Connect

The Savannah River National Laboratory (SRNL) has developed a new medium for storage of hydrogen and other gases. This involves fabrication of thin, Porous Walled, Hollow Glass Microspheres (PW-HGMs), with diameters generally in the range of 1 to several hundred microns. What is unique about the glass microballons is that porosity has been induced and controlled within the thin, one micron thick walls, on the scale of 10 to several thousand Angstroms. This porosity results in interesting properties including the ability to use these channels to fill the microballons with special absorbents and other materials, thus providing a contained environment even for reactive species. Gases can now enter the microspheres and be retained on the absorbents, resulting in solid-state and contained storage of even reactive species. Also, the porosity can be altered and controlled in various ways, and even used to filter mixed gas streams within a system. SRNL is involved in about a half dozen different programs involving these PW-HGMs and an overview of some of these activities and results emerging are presented.

Wicks, G; Leung Heung, L; Ray Schumacher, R

2008-04-15

295

Fixation of the fully hydroxyapatite-coated Corail stem implanted due to femoral neck fracture  

PubMed Central

Background Today, dislocated femoral neck fractures are commonly treated with a cemented hip arthroplasty. However, cementing of the femoral component may lead to adverse effects and even death. Uncemented stems may lower these risks and hydroxyapatite (HA) coating may enhance integration, but prosthetic stability and clinical outcome in patients with osteoporotic bone have not been fully explored. We therefore studied fixation and clinical outcome in patients who had had a femoral neck fracture and who had received a fully HA-coated stem prosthesis. Patients and methods 50 patients with a dislocated femoral neck fracture were operated with the fully HA-coated Corail total or hemiarthroplasty. 38 patients, mean age 81 (70–96) years, were followed for 24 months with conventional radiographs, RSA, DEXA, and for clinical outcome. Results 31 of the 38 implants moved statistically significantly up to 3 months, mainly distally, mean 2.7 mm (max. 20 mm (SD 4.3)), and rotated into retroversion mean 3.3º (–1.8 to 17) (SD 4.3) and then appeared to stabilize. Distal stem migration was more pronounced if the stem was deemed to be too small. There was no correlation between BMD and stem migration. The migration did not result in any clinically adverse effects. Interpretation The fully hydroxyapatite-coated Corail stem migrates during the first 3 months, but clinical outcome appears to be good, without any adverse events. PMID:22112154

2012-01-01

296

Development of high strength hydroxyapatite for bone tissue regeneration using nanobioactive glass composites  

SciTech Connect

With an increasing demand of biocompatible bone substitutes for the treatment of bone diseases and bone tissue regeneration, bioactive glass composites are being tested to improvise the osteoconductive as well as osteoinductive properties. Nanobioactive glass (nBG) composites, having composition of SiO{sub 2} 70 mol%, CaO 26 mol % and P{sub 2}O{sub 5} 4 mol% were prepared by Freeze drying method using PEG-PPG-PEG co-polymer. Polymer addition improves the mechanical strength and porosity of the scaffold of nBG. Nano Bioactive glass composites upon implantation undergo specific reactions leading to the formation of crystalline hydroxyapatite (HA). This is tested in vitro using Simulated Body Fluid (SBF). This high strength hydroxyapatite (HA) layer acts as osteoconductive in cellular environment, by acting as mineral base of bones, onto which new bone cells proliferate leading to new bone formation. Strength of the nBG composites as well as HA is in the range of cortical and cancellous bone, thus proving significant for bone tissue regeneration substitutes.

Shrivastava, Pragya; Dalai, Sridhar; Vijayalakshmi, S. [Centre for Research in Nanotechnology and Science, IIT Bombay (India); Sudera, Prerna; Sivam, Santosh Param [Amity Institute of Nanotechnology, Amity University, Noida, Uttar Pradesh-201303 (India); Sharma, Pratibha [Dept of Energy Science and Engineering, IIT Bombay (India)

2013-02-05

297

Acute and Subacute Toxicity In Vivo of Thermal-Sprayed Silver Containing Hydroxyapatite Coating in Rat Tibia  

PubMed Central

To reduce the incidence of implant-associated infection, we previously developed a novel coating technology using hydroxyapatite (HA) containing silver (Ag). This study examined in vivo acute and subacute toxicity associated with the Ag-HA coating in rat tibiae. Ten-week-old rats received implantation of HA-, 2% Ag-HA-, or 50% Ag-HA-coated titanium rods. Concentrations of silver in serum, brain, liver, kidneys, and spleen were measured in the acute phase (2–4 days after treatment) and subacute phase (4–12 weeks after treatment). Biochemical and histological examinations of those organs were also performed. Mean serum silver concentration peaked in the acute phase and then gradually decreased. Mean silver concentrations in all examined organs from the 2% Ag-HA coating groups showed no significant differences compared with the HA coating group. No significant differences in mean levels of glutamic-oxaloacetic transaminase, glutamic-pyruvic transaminase, lactate dehydrogenase, creatinine, or blood urea nitrogen were seen between the three groups and controls. Histological examinations of all organs revealed no abnormal pathologic findings. No acute or subacute toxicity was seen in vivo for 2% Ag-HA coating or HA coating. Ag-HA coatings on implants may represent biologically safe antibacterial biomaterials and may be of value for reducing surgical-site infections related to implantation. PMID:24779019

Tsukamoto, Masatsugu; Miyamoto, Hiroshi; Ando, Yoshiki; Eto, Shuichi; Akiyama, Takayuki; Yonekura, Yutaka; Mawatari, Masaaki

2014-01-01

298

Characterization of a Polyamine Microsphere and Its Adsorption for Protein  

PubMed Central

A novel polyamine microsphere, prepared from the water-in-oil emulsion of polyethylenimine, was characterized. The investigation of scanning electron microscopy showed that the polyamine microsphere is a regular ball with a smooth surface. The diameter distribution of the microsphere is 0.37–4.29 ?m. The isoelectric point of the microsphere is 10.6. The microsphere can adsorb proteins through the co-effect of electrostatic and hydrophobic interactions. Among the proteins tested, the highest value of adsorption of microsphere, 127.8 mg·g?1 microsphere, was obtained with lipase. In comparison with other proteins, the hydrophobic force is more important in promoting the adsorption of lipase. The microsphere can preferentially adsorb lipase from an even mixture of proteins. The optimum temperature and pH for the selective adsorption of lipase by the microsphere was 35 °C and pH 7.0. PMID:23344018

Wang, Feng; Liu, Pei; Nie, Tingting; Wei, Huixian; Cui, Zhenggang

2013-01-01

299

Preparation and characterization of porous PDLLA/HA composite foams by supercritical carbon dioxide technology.  

PubMed

A composite poly(D,L)lactic acid (PDLLA)/hydroxyapatite (HA) biomaterial was prepared by in situ polymerization of D,L-lactide monomer and HA. Supercritical CO2 (SC CO2) technology was developed to prepare the biodegradable composite foams for use in tissue regeneration. In this technology, NaCl particles were used as porogen to produce an open-pore structure. Organic solvents were not used and high temperature was not necessary. The problem with pore interconnectivity was resolved. High-porosity composite foams (up to 90% +/- 2% porosity) were obtained with pore sizes ranging from 100 to 300 microm suitable for cell seeding. The microstructure and morphology of the composite foams could be controlled by saturation pressure, saturation time, and temperature as well as amount of NaCl particles. The compressive strength and water absorbability of the composite foams were also determined. With an increase in HA amount, the molecular weight of PDLLA/HA composite foams decreased, but the mechanical strength and hydrophilicity increased slightly. PMID:16924605

Teng, Xinrong; Ren, Jie; Gu, Shuying

2007-04-01

300

A homogenous CS/NaCMC/n-HA polyelectrolyte complex membrane prepared by gradual electrostatic assembling.  

PubMed

A homogenous membrane composed of chitosan (CS), sodium carboxymethyl cellulose (NaCMC) and nano hydroxyapatite (n-HA) was prepared by a gradual electrostatic assembling (GEA) method. The physical and chemical properties of the membranes with different n-HA contents and CS/NaCMC ratios were characterized by Scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction and mechanical test. The schematic formation mechanism of the membrane was discussed. The results show that GEA is an effective method to prepare the polyelectrolyte complex (PEC) membrane, in which oppositely charged CS-NaCMC polysaccharides can assemble mildly and gradually through electrostatic interaction to form the membrane framework, while the filled n-HA crystals can regulate the structure stability of the composite membrane. The optimum preparation condition for the PEC membrane can be fixed to a content of 60 wt% n-HA, an equivalent amount of CS to NaCMC and a drying temperature of 60°C. The PEC membrane may have good prospect for guided bone regeneration. PMID:21140198

Jiang, Hong; Zuo, Yi; Cheng, Lin; Wang, Hongli; Gu, Aiqun; Li, Yubao

2011-02-01

301

The Fabrication of Near Net-Shaped Hydroxyapatite Ceramics by the Oxidation of Solid, Metal-Bearing Precursors  

Microsoft Academic Search

Near net-shaped bodies of hydroxyapatite (HA), Ca10(PO4)6(OH)2, have been fabricated by a novel process: the oxidation of solid, metal-bearing precursors. High-energy mechanical alloying was used to produce an intimate powder mixture of metallic calcium and calcium pyrophosphate, ?-Ca2P2O7, that possessed an overall stoichiometry consistent with HA (molar Ca:Ca2P2O7 ratio = 4:3). The milled Ca-Ca2P2O7 mixtures were sufficiently malleable as to

Eaden Saw; Kenneth H. Sandhage; Patrick K. Gallagher; Alan S. Litsky

2000-01-01

302

Rapid microwave-assisted synthesis and characterization of cellulose-hydroxyapatite nanocomposites in N,N-dimethylacetamide solvent.  

PubMed

Preparation of nanocomposites was carried out using microcrystalline cellulose, CaCl(2), and NaH(2)PO(4) in N,N-dimethylacetamide (DMAc) solvent by a microwave-assisted method at 150 degrees C. XRD results showed that the nanocomposites consisted of cellulose and hydroxyapatite (HA). The cellulose existed as a matrix in the nanocomposites. SEM and TEM analysis showed that HA nanorods were homogeneously dispersed in the cellulose matrix. The effects of the microwave heating time on the products were investigated. This method has advantages of being simple, rapid, low-cost, and environmentally friendly. PMID:20381016

Ma, Ming-Guo; Zhu, Jie-Fang; Jia, Ning; Li, Shu-Ming; Sun, Run-Cang; Cao, Shao-Wen; Chen, Feng

2010-05-27

303

Carbonate hydroxyapatite gel monolith formation and drying.  

PubMed

The effect of carbonate in reducing the crystal size of precipitated hydroxyapatite by approximately an order of magnitude has not been used previously in the preparation of gel monoliths for the fabrication of carbonate hydroxyapatite ceramics. The aim of this study was to devise a method whereby gel monoliths of carbonate hydroxyapatite could be repeatably produced without cracking. A precipitation reaction was used for the preparation of carbonate hydroxyapatities with carbonate contents of 5.8 and 7.8 wt%. Biaxial vacuum filtration was used to form disc shaped monoliths. The rate of filtration of a 7.8 wt% carbonate hydroxyapatite sol was measured throughout the gelation process. Gel monoliths were dried slowly in air and the mass and dimensions of the gel were recorded once approximately every 24 hours. Using this data, the permeability, water volume fraction with time, rate of water loss, gelation point and gel density were determined. The pore size distribution was measured using mercury porosimetry for a carbonate apatite gel and a pressed powder pellet of a commercial hydroxyapatite. In tact monoliths were formed with masses up to 9.9 g. It was found that gelation behaviour was independent of monolith size and carbonate content and the final green density of all monoliths was 37%. Gelation was found to occur at 50-55 vol% water. Gel monoliths were found to have a monomodal pore size distribution with a mean pore size of 9.1 nm, whereas a pressed pellet of hydroxyapatite had a bimodal pore size distribution. PMID:8761520

Barralet, J E; Best, S M; Bonfield, W

1996-01-01

304

STEM and EDXS characterisation of physico-chemical reactions at the periphery of sol-gel derived Zn-substituted hydroxyapatites during interactions with biological fluids  

PubMed Central

With its good properties of biocompatibility and bioactivity hydroxyapatite (HA) is highly used as bone substitutes and as coatings on metallic prostheses. In order to improve bioactive properties of HA we have elaborated Zn2+ doped hydroxyapatite. Zn2+ ions substitute for Ca2+ cations in the HA structure and four Zn concentrations (Zn/Zn+Ca) were prepared 0.5, 1, 2, 5 % at. To study physico-chemical reactions at the materials periphery, we immersed the bioceramics into biological fluids for delays from 1 day to 20 days. The surface changes were studied at the nanometer scale by scanning transmission electron microscopy associated to energy dispersive X-ray spectroscopy. After 20 days of immersion we observed the formation of a calcium-phosphate layer at the periphery of the HA doped with 5% of zinc. This layer contains magnesium and its thickness was around 200 nm. Formation of this Ca-P-Mg layer represents bioactivity properties of the 5% Zn-substituted hydroxyapatite. This biologically active layer improves properties of HA and will permit a chemical bond between the ceramic and bone. PMID:15893220

Jallot, Edouard; Nedelec, Jean-Marie; Grimault, Anne S.; Chassot, Emmanuelle; Grandjean-Laquerriere, Alexia; Laquerriere, Patrice; Laurent-Maquin, Dominique

2005-01-01

305

Long-term biodistribution in vivo and toxicity of radioactive/magnetic hydroxyapatite nanorods.  

PubMed

Although nanoscale hydroxyapatite [Ca10(PO4)6(OH)2; HA] has been widely investigated as a carrier in the delivery of drugs, genes, or siRNA, the in vivo toxicity of nanoscale HA is not clear and the long-term dynamic distribution in vivo has not hitherto been visualized. In this work, gadolinium-doped HA nanorods (HA:Gd) with an r1 value of 5.49 s(-1) (mm)(-1) have been prepared by a hydrothermal method. Samarium-153 ((153)Sm) was then effectively post-labeled onto the HA:Gd ((153)Sm-HA:Gd) with a labeling rate of ?100% and a radio-labeling stability in vitro of ?100% over 48 h. The product could serve as a new dual-modality probe for SPECT and MR imaging in vivo. By means of SPECT and MRI, the HA:Gd nanorods were found to be quickly taken up by the mononuclear phagocyte system, especially the liver and spleen. The nanorods in the liver and lung tended to be eliminated within 24 h, but nanorods in the spleen behaved differently and proved difficult to excrete. In vitro studies by cell transmission electron microscopy (TEM) and methyl thiazolyl tetrazolium (MTT) assay showed good biocompatibility of the HA:Gd nanorods with HeLa cells, even at a high concentration. The indicators of body weight, histology, and serology demonstrated that the HA:Gd nanorods exhibited excellent biocompatibility in vivo for at least 61 days. Therefore, (153)Sm-HA:Gd nanorods with excellent relaxivity, ?-emission, and biosafety offer clear advantages and potential for bioapplications. PMID:24439404

Liu, Ying; Sun, Yun; Cao, Cong; Yang, Yang; Wu, Yongquan; Ju, Dianwen; Li, Fuyou

2014-03-01

306

Hydroxyapatite-Based Biomaterials vs. Autologous Bone Graft in Spinal Fusion: An in Vivo Animal Study.  

PubMed

Study Design. An in vivo study was designed to compare the efficacy of biomimetic Magnesium-Hydroxyapatite (MgHA) and of human demineralised bone matrix (HDBM), both dispersed in a mixture of biomimetic Mg-HA nanoparticles, with that of an autologous bone graft.Objective. The objective of this study was to evaluate two new bone substitutes as alternatives to a bone autograft for spinal fusion, determining their osteoinductive and osteoconductive properties, and their capacity of remodeling, using a large animal model.Summary of Background Data. Spinal fusion is a common surgical procedure and it is performed for different conditions. A successful fusion requires potentially osteogenic, osteoinductive and osteoconductive biomaterials.Methods. A posterolateral spinal fusion model involved 18 sheep, bilaterally implanting test materials between the vertebral transverse processes. The animals were divided into two groups: one fusion level was treated with MgHA (Group 1) or with HDBM-MgHA (Group 2). The other fusion level received bone autografts in both groups.Results. Radiographic, histological and microtomographic results indicated good osteointegration between the spinous process and the vertebral foramen for both materials. Histomorphometry revealed no significant differences between MgHA and autologous bone for all the parameters examined while significantly lower values of bone volume were observed between HDBM-MgHA and autologous bone. Moreover, the normalisation of the histomorphometrical data with autologous bone revealed that MgHA showed a significantly higher value of bone volume and a lower value of trabecular number, more similar to autologous bone, in comparison to HDBM-MgHA.Conclusion. The study showed that the use of MgHA in an ovine model of spinal fusion led to the deposition of new bone tissue without qualitative and quantitative differences with respect to new bone formed with autologous bone while the HDBM-MgHA led to a reduced deposition of newly-formed bone tissue. PMID:24718060

Bròdano, Giovanni Barbanti; Giavaresi, Gianluca; Lolli, Francesco; Salamanna, Francesca; Parrilli, Annapaola; Martini, Lucia; Griffoni, Cristiana; Greggi, Tiziana; Arcangeli, Elena; Pressato, Daniele; Boriani, Stefano; Fini, Milena

2014-04-01

307

Effect of carbonate and biological macromolecules on formation and properties of hydroxyapatite.  

PubMed

Amorphous calcium phosphate (ACP) was transformed at 25 degrees to hydroxyapatite (HA) in horse and bovine serum; solutions of serum-protein fractions in tris-HC1 buffer (pH 7.4), and pH 7.4 buffers containing from 0.1 to 10 times physiological CO3(2-) concentration. The ACP-to-HA transformation was slower in whole serum and serum fractions than in control buffer solution. The observed adsorption of serum proteins on ACP and HA probably inhibits both the dissolution of the ACP particles and the growth of HA crystals. After 72 h all transformations were complete as determined by X-ray diffraction. The HA crystal dimensions decreased with increasing C03(2-) but the shape, as shown by X-ray linewidths, was relatively constant up to about 4% CO3(2-). At 15% CO3(2-) the crystals were more equiaxial and less needle-like in habit. The radial distribution function (RDF) of HA with 3.7% CO3(2-) is less well resolved than the RDF of HA with ambient CO3(2-) (1.1%). The peaks are less sharp and their amplitude falls more rapidly with increasing atomic separation than for low CO3(2-)-HA. These effects show that CO3(2-) decreases the regularity of the atomic arrangement when incorporated in HA. The rapid decrease, with increasing CO3(2-) content, of the IR splitting of the P-O bending mode of CO3(2-)-HA is attributed to reduced crystal size and possibly to a perturbation of the crystal field due to CO3(2-)-induced lattice distortion. Finally, for bone mineral, it is probable that the poor resolution of the X-ray and IR patterns is due, in large part, to small crystal size and internal disorder caused by CO3(2-). PMID:1148899

Blumenthal, N C; Betts, F; Posner, A S

1975-07-25

308

Chitosan microspheres prepared by spray drying.  

PubMed

Non-crosslinked and crosslinked chitosan microspheres were prepared by a spray drying method. The microspheres so prepared had a good sphericity and a smooth but distorted surface morphology. They were positively charged. The particle size ranged from 2 to 10 micron. The size and seta potential of the particles were influenced by the crosslinking level. With decreasing amount of crosslinking agent (either glutaraldehyde or formaldehyde), both particle size and zeta potential were increased. Preparation conditions also had some influence on the particle size. DSC studies revealed that the H2 antagonist drug cimetidine, as well as famotidine was molecularly dispersed inside the microspheres, in the form of a solid solution. The release of model drugs (cimetidine, famotidine and nizatidine) from these microspheres was fast, and accompanied by a burst effect. PMID:10502613

He, P; Davis, S S; Illum, L

1999-09-30

309

Organic aerogel microspheres and fabrication method therefor  

DOEpatents

Organic aerogel microspheres which can be used in capacitors, batteries, thermal insulation, adsorption/filtration media, and chromatographic packings, having diameters ranging from about 1 micron to about 3 mm. The microspheres can be pyrolyzed to form carbon aerogel microspheres. This method involves stirring the aqueous organic phase in mineral oil at elevated temperature until the dispersed organic phase polymerizes and forms nonsticky gel spheres. The size of the microspheres depends on the collision rate of the liquid droplets and the reaction rate of the monomers from which the aqueous solution is formed. The collision rate is governed by the volume ratio of the aqueous solution to the mineral oil and the shear rate, while the reaction rate is governed by the chemical formulation and the curing temperature.

Mayer, Steven T. (San Leandro, CA); Kong, Fung-Ming (Pleasanton, CA); Pekala, Richard W. (Pleasant Hill, CA); Kaschmitter, James L. (Pleasanton, CA)

1996-01-01

310

Organic aerogel microspheres and fabrication method therefor  

DOEpatents

Organic aerogel microspheres which can be used in capacitors, batteries, thermal insulation, adsorption/filtration media, and chromatographic packings, having diameters ranging from about 1 micron to about 3 mm. The microspheres can be pyrolyzed to form carbon aerogel microspheres. This method involves stirring the aqueous organic phase in mineral oil at elevated temperature until the dispersed organic phase polymerizes and forms nonsticky gel spheres. The size of the microspheres depends on the collision rate of the liquid droplets and the reaction rate of the monomers from which the aqueous solution is formed. The collision rate is governed by the volume ratio of the aqueous solution to the mineral oil and the shear rate, while the reaction rate is governed by the chemical formulation and the curing temperature.

Mayer, S.T.; Kong, F.M.; Pekala, R.W.; Kaschmitter, J.L.

1996-04-16

311

Stability of proteins within biodegradable microspheres  

E-print Network

In the past decade, biodegradable polymers have become the materials of choice for a variety of biomaterials applications. In particular, poly(lactic-co-glycolic acid) (PLGA) microspheres have been extensively studied for ...

Fu, Karen, 1967-

2000-01-01

312

21 CFR 870.1360 - Trace microsphere.  

Code of Federal Regulations, 2014 CFR

...Identification. A trace microsphere is a radioactively tagged nonbiodegradable particle that is intended to be injected into an artery or vein and trapped in the capillary bed for the purpose of studying blood flow within or to an organ. (b)...

2014-04-01

313

Effects of vascular endothelial cell growth factor on fibrovascular ingrowth into rabbits hydroxyapatite orbital implant.  

PubMed

The effects of different concentrations of vascular endothelial cell growth factor (VEGF) on the fibrovascular ingrowth into rabbits hydroxyapatite orbital implant were investigated. Twelve New Zealand white rabbits were divided into 3 groups and received hydroxyapatite orbital implant surgery in their right eyes. Before and after the operation, the implants were treated with 10 ng/ml VEGF, 100 ng/ml VEGF, or normal saline as control group. The animals received technetium bones scan at 2, 4, and 6 weeks postoperatively. The mean radioactivity counts within region of interest (ROI) of the surgery eye (R) and the non-surgery eye (L) in the same animal were tested, and the R/L ratios were calculated. The implants were harvested at 6th weeks and examined histopathologically. The results showed that at second week, there was no significant difference in mean R/L ratios between VEGF group and control group (F=2.83, P=0.111); At 4th week (F=7.728, P=0.011) and 6th week (F=7.831, P=0.011) postoperatively, the mean ratios in VEGF groups were significantly higher than that in control group. At 6th week postoperatively, the fibrovascularization rates in VEGF groups were higher than in control group significantly (F=8.711, P=0.008). It was suggested that VEGF could promote the fibrovascular ingrowth into hydroxyapatite orbital implant, thus might shorten the time required for complete vascularization of the HA orbital implant. PMID:15315351

Zhang, Hong; Li, Guigang; Ji, Caini; He, Hua; Wang, Junming; Hu, Weikun; Wu, Hua; Chen, Jing

2004-01-01

314

Electrospinning of calcium carbonate fibers and their conversion to nanocrystalline hydroxyapatite.  

PubMed

Calcium carbonate (CaCO3) fibers were prepared by electrospinning followed by annealing. Solutions consisting of calcium nitrate tetrahydrate (Ca(NO3)2·4H2O) and polyvinylpyrrolidone (PVP) dissolved in ethanol or 2-methoxyethanol were used for the fiber preparation. By varying the precursor concentrations in the electrospinning solutions CaCO3 fibers with average diameters from 140 to 290nm were obtained. After calcination the fibers were identified as calcite by X-ray diffraction (XRD). The calcination process was studied in detail with high temperature X-ray diffraction (HTXRD) and thermogravimetric analysis (TGA). The initially weak fiber-to-substrate adhesion was improved by adding a strengthening CaCO3 layer by spin or dip coating Ca(NO3)2/PVP precursor solution on the CaCO3 fibers followed by annealing of the gel formed inside the fiber layer. The CaCO3 fibers were converted to nanocrystalline hydroxyapatite (HA) fibers by treatment in a dilute phosphate solution. The resulting hydroxyapatite had a plate-like crystal structure with resemblance to bone mineral. The calcium carbonate and hydroxyapatite fibers are interesting materials for bone scaffolds and bioactive coatings. PMID:25491852

Holopainen, Jani; Santala, Eero; Heikkilä, Mikko; Ritala, Mikko

2014-12-01

315

The effects of hydroxyapatite/calcium phosphate glass scaffold and its surface modification with bovine serum albumin on 1-wall intrabony defects of beagle dogs: a preliminary study.  

PubMed

The purpose of this study was to evaluate the effects of biphasic hydroxyapatite/calcium phosphate glass (HA/CPG) scaffold and its surface modification with bovine serum albumin (BSA) on periodontal regeneration. 1-wall intrabony defects were surgically created on five beagle dogs. HA/CPG scaffolds, with a hydroxyapatite (HA)/calcium phosphate glass (CPG) ratio of 95:5 by weight (%) and surface modification done by 2% bovine serum albumin, were used. The control group received surgical flap operation, and the experimental groups were filled with HA/CPG scaffolds and HA/CPG(BSA) scaffolds. The animals were sacrificed eight weeks after surgery. Histological findings revealed better space maintenance in the experimental groups than the control group, and showed new bone formation intermittently in between the residual material particles. The newly formed bone was mostly woven bone and the residual particles were undergoing resorption. Cementum regeneration was observed with limited root resorption in all the groups. Histometric analysis also revealed greater mean values in new bone formation, cementum regeneration and bone area than the control group in both experimental groups. However, similar findings were presented between HA/CPG and HA/CPG(BSA). The result of the present study revealed the newly fabricated HA/CPG scaffold to have a potential use as a bone substitute material. PMID:19029611

Um, Yoo-Jung; Jung, Ui-Won; Chae, Gyung-Joon; Kim, Chang-Sung; Lee, Yong-Keun; Cho, Kyoo-Sung; Kim, Chong-Kwan; Choi, Seong-Ho

2008-12-01

316

Method for introduction of gases into microspheres  

DOEpatents

A method for producing small hollow glass spheres filled with a gas by introduction of the gas during formation of the hollow glass spheres. Hollow glass microspheres having a diameter up to about 500.mu. with both thin walls (0.5 to 4.mu.) and thick walls (5 to 20.mu.) that contain various fill gases, such as Ar, Kr, Xe, Br, DT, H.sub.2, D.sub.2, He, N.sub.2, Ne, CO.sub.2, etc. in the interior thereof, can be produced by the diffusion of the fill gas or gases into the microsphere during the formation thereof from a liquid droplet of glass-forming solution. This is accomplished by filling at least a portion of the multiple-zone drop-furnace used in producing hollow microspheres with the gas or gases of interest, and then taking advantage of the high rate of gaseous diffusion of the fill gas through the wall of the gel membrane before it transforms into a glass microsphere as it is processed in the multiple-zone furnace. Almost any gas can be introduced into the inner cavity of a glass microsphere by this method during the formation of the microsphere provided that the gas is diffused into the gel membrane or microsphere prior to its transformation into glass. The process of this invention provides a significant savings of time and related expense of filling glass microspheres with various gases. For example, the time for filling a glass microballoon with 1 atmosphere of DT is reduced from about two hours to a few seconds.

Hendricks, Charles D. (Livermore, CA); Koo, Jackson C. (San Ramon, CA); Rosencwaig, Allan (Danville, CA)

1981-01-01

317

Better early osteogenesis of electroconductive hydroxyapatite-calcium titanate composites in a rabbit animal model.  

PubMed

In view of the fact that bone healing can be enhanced due to external electric field application, it is important to assess the influence of the implant conductivity on the bone regeneration in vivo. To address this issue, this study reports the in vivo biocompatibility property of multistage spark plasma sintered hydroxyapatite (HA)-80 wt % calcium titanate (CaTiO3 ) composites and monolithic HA, which have widely different conductivity property (14 orders of magnitude difference). The ability of bone regeneration was assessed by implantation in cylindrical femoral bone defects of rabbit animal model for varying time period of 1, 4, and 12 weeks. The overall assessment of the histology results suggests that the progressive healing of bone defects around HA-80 wt % CaTiO3 is associated with a better efficacy with respect to (w.r.t) early stage neobone formation, which is histomorphometrically around 140% higher than monolithic HA. Overall, this study demonstrates that the in vivo biocompatibility property of HA-80 wt % CaTiO3 with respect to local effects after 12 weeks of implantation is not compromised both qualitatively and quantitatively, and a comparison with control implant (HA) points toward the critical role of electrical conductivity on better early stage bone regeneration. PMID:23589392

Mallik, Prafulla Kumar; Basu, Bikramjit

2014-03-01

318

Polylactide nanofibers with hydroxyapatite as growth substrates for osteoblast-like cells.  

PubMed

Various types of nanofibers are increasingly used in tissue engineering, mainly for their ability to mimic the architecture of tissue at the nanoscale. We evaluated the adhesion, growth, viability, and differentiation of human osteoblast-like MG 63 cells on polylactide (PLA) nanofibers prepared by needle-less electrospinning and loaded with 5 or 15 wt % of hydroxyapatite (HA) nanoparticles. On day 7 after seeding, the cell number was the highest on samples with 15 wt % of HA. This result was confirmed by the XTT test, especially after dynamic cultivation, when the number of metabolically active cells on these samples was even higher than on control polystyrene. Staining with a live/dead kit showed that the viability of cells on all nanofibrous scaffolds was very high and comparable to that on control polystyrene dishes. An enzyme-linked immunosorbent assay revealed that the concentration of osteocalcin was also higher in cells on samples with 15 wt % of HA. There was no immune activation of cells (measured by production of TNF-alpha), associated with the incorporation of HA. Moreover, the addition of HA suppressed the creep behavior of the scaffolds in their dry state. Thus, nanofibrous PLA scaffolds have potential for bone tissue engineering, particularly those with 15 wt % of HA. PMID:24375970

Novotna, Katarina; Zajdlova, Martina; Suchy, Tomas; Hadraba, Daniel; Lopot, Frantisek; Zaloudkova, Margit; Douglas, Timothy E L; Munzarova, Marcela; Juklickova, Martina; Stranska, Denisa; Kubies, Dana; Schaubroeck, David; Wille, Sebastian; Balcaen, Lieve; Jarosova, Marketa; Kozak, Halyna; Kromka, Alexander; Svindrych, Zdenek; Lisa, Vera; Balik, Karel; Bacakova, Lucie

2014-11-01

319

Nano-Ag-loaded hydroxyapatite coatings on titanium surfaces by electrochemical deposition  

PubMed Central

Hydroxyapatite (HA) coatings on titanium (Ti) substrates have attracted much attention owing to the combination of good mechanical properties of Ti and superior biocompatibility of HA. Incorporating silver (Ag) into HA coatings is an effective method to impart the coatings with antibacterial properties. However, the uniform distribution of Ag is still a challenge and Ag particles in the coatings are easy to agglomerate, which in turn affects the applications of the coatings. In this study, we employed pulsed electrochemical deposition to co-deposit HA and Ag simultaneously, which realized the uniform distribution of Ag particles in the coatings. This method was based on the use of a well-designed electrolyte containing Ag ions, calcium ions and l-cysteine, in which cysteine acted as the coordination agent to stabilize Ag ions. The antibacterial and cell culture tests were used to evaluate the antibacterial properties and biocompatibility of HA/Ag composite coatings, respectively. The results indicated the as-prepared coatings had good antibacterial properties and biocompatibility. However, an appropriate silver content should be chosen to balance the biocompatibility and antibacterial properties. Heat treatments promoted the adhesive strength and enhanced the biocompatibility without sacrificing the antibacterial properties of the HA/Ag coatings. In summary, this study provided an alternative method to prepare bioactive surfaces with bactericidal ability for biomedical devices. PMID:20880853

Lu, Xiong; Zhang, Bailin; Wang, Yingbo; Zhou, Xianli; Weng, Jie; Qu, Shuxin; Feng, Bo; Watari, Fumio; Ding, Yonghui; Leng, Yang

2011-01-01

320

Micromechanical modeling of hydroxyapatite whisker reinforced polymer composites and cortical bone tissue  

NASA Astrophysics Data System (ADS)

A new micromechanical model was developed to predict the elastic moduli of hydroxyapatite (HA) whisker reinforced polymer biocomposites based upon the elastic properties of each phase and the reinforcement volume fraction, morphology and preferred orientation. The effects of the HA whisker volume fraction, morphology and orientation distribution were investigated by comparing two and three-dimensional model predictions with experimentally measured elastic moduli or stiffness coefficients, respectively, for HA whisker reinforced high density polyethylene (HDPE) composites. Predictions using experimental measurements of the HA whisker aspect ratio distribution and orientation distribution were also compared to common idealized assumptions. The best model predictions were obtained using the experimentally measured HA whisker aspect ratio distribution and orientation distribution. The same micromechanical model developed and validated for HA whisker reinforced composites was also applied to the elastic properties of human cortical bone tissue. The orientation distribution of apatite crystals in bone was measured and statistically correlated to the elastic anisotropy of bone tissue. The relationship was further investigated using the micromechanical model. The orientation distribution of apatite crystals was shown to be a significant factor contributing to the elastic anisotropy of cortical bone tissue.

Yue, Weimin

2006-04-01

321

Preparation of foam-like carbon nanotubes/hydroxyapatite composite scaffolds with superparamagnetic properties  

NASA Astrophysics Data System (ADS)

In this paper, the foam-like composite scaffolds composed of hydroxyapatite (HA) and carbon nanotubes (CNTs) were prepared by a new method, where a polymer impregnating method was used for porous HA-based scaffold and a chemical vapor deposition (CVD) method was used for the growth of CNTs from the HA-based scaffold. The process produces the CNTs/HA scaffolds that have a foam-like structure with better mechanical property, better microstructure and a high degree of interconnection. A favorable pore size with big pores of 1-2 mm and small pores of 20-300 ?m for osteoconduction and bone ingrowth is presented in these scaffolds. About 2 wt% multi-walled CNTs with the diameter of 60-100 nm are observed to be in situ grown from deficient nano-HA crystallites. Magnetic measurement exhibits these scaffolds are superparamagnetic with a saturation magnetization of 1.14 emu g-1 at a room temperature, benefiting the scaffolds to take up growth factors in vivo, stem cell or other bioactive molecules easily. This new type of CNTs/HA scaffolds is expected to have a promising applications in bone tissue engineering, targeted drug delivery system and other biomedical fields.

Lu, X. Y.; Qiu, T.; Wang, X. F.; Zhang, M.; Gao, X. L.; Li, R. X.; Lu, X.; Weng, J.

2012-12-01

322

Physicochemical and biological properties of nano-hydroxyapatite-reinforced aliphatic polyurethanes membranes.  

PubMed

Polymer nano-composite membranes, based on aliphatic biodegradable polyurethane (PU) elastomers and nano-hydroxyapatite (n-HA), were prepared by solvent casting and freeze-drying. The PU matrix was synthesized from 4,4'-dicyclohexylmethane diisocyanate (H(12) MDI), poly(ethylene glycol) (PEG), castor oil (CO) and 1,4-butandiol (BDO). The n-HA/PU membranes were characterized by SEM, XRD, IR, TG, mechanical test and in vitro biocompatibility. The results revealed that incorporation of 30 wt% n-HA into the PU matrix increased the tensile strength nearly by 186% and the elongation-at-break by 107% compared to pure PU. The addition of n-HA had the slight positive effect on the thermal stability of PU. Cell culture and MTT assays showed that the incorporation of n-HA into the PU matrix provided a favourable environment for initial cell adhesion, maintained cell viability and cell proliferation. These results suggested that the n-HA/PU composite membrane might be a prospective biodegradable guided bone regeneration (GBR) membrane for future applications. PMID:20537245

Liu, Haohuai; Zhang, Li; Li, Jidong; Zou, Qin; Zuo, Yi; Tian, Weidong; Li, Yubao

2010-01-01

323

Preparation and application of cellulose triacetate microspheres.  

PubMed

Cellulose triacetate was prepared via reacting of a mixture of acetic anhydride and acetic acid containing sulfuric acid as catalyst with ramie fiber obtained from a biomass of ramie. The cellulose triacetate with a degree of substitution (DS) 2.93 of the ramie fiber was obtained. The honeycomb-like cellulose triacetate microspheres with an average diameter of 14 microm were made from the cellulose triacetate solution. The optimum conditions for preparing the microspheres were determined as cellulose triacetate/dichloromethane ratio 1:7 (w/w), and 0.75% sodium dodecylsulfonate. The cellulose triacetate microspheres were characterized using FT-IR, NMR, XRD, and SEM. Application of the microspheres as an adsorbent for removing disperse dyes in water was investigated under the temperatures from 15 to 50 degrees C, pHs from 4 to 9, and the weight of cellulose triacetate microspheres from 0.03 to 0.09 g. The cellulose triacetate microspheres exhibited a 16.5mg/g capability to remove DR dye from water at 50 degrees C and pH 7. PMID:20060644

Fan, Xiushan; Liu, Zhao-Tie; Liu, Zhong-Wen

2010-05-15

324

Metronidazole loaded pectin microspheres for colon targeting.  

PubMed

A multiparticulate system having pH-sensitive property and specific enzyme biodegradability for colon-targeted delivery of metronidazole was developed. Pectin microspheres were prepared using emulsion-dehydration technique. These microspheres were coated with Eudragit(R) S-100 using oil-in-oil solvent evaporation method. The SEM was used to characterize the surface of these microspheres and a distinct coating over microspheres could be seen. The in vitro drug release studies exhibited no drug release at gastric pH, however continuous release of drug was observed from the formulation at colonic pH. Further, the release of drug from formulation was found to be higher in the presence of rat caecal contents, indicating the effect of colonic enzymes on the pectin microspheres. The in vivo studies were also performed by assessing the drug concentration in various parts of the GIT at different time intervals which exhibited the potentiality of formulation for colon targeting. Hence, it can be concluded that Eudragit coated pectin microspheres can be used for the colon specific delivery of drug. PMID:19492406

Vaidya, Ankur; Jain, Aviral; Khare, Piush; Agrawal, Ram K; Jain, Sanjay K

2009-11-01

325

Nonlinear elasticity of microsphere heaps  

NASA Astrophysics Data System (ADS)

Thermal fluctuations, geometric exclusion, and external driving all govern the mechanical response of dense particulate suspensions. Here, we measure the stress-strain response of quasi-two-dimensional flow-stabilized microsphere heaps in a regime in which all three effects are present using a microfluidic device. We observe that the elastic modulus and the mean interparticle separation of the heaps are tunable via the confining stress provided by the fluid flow. Furthermore, the measured stress-strain curves exhibit a universal nonlinear shape, which can be predicted from a thermal van der Waals equation of state with excluded volume. This analysis indicates that many-body interactions contribute a significant fraction of the stress supported by the heap.

Ortiz, Carlos P.; Daniels, Karen E.; Riehn, Robert

2014-08-01

326

Effect of calcination on sintering of hydroxyapatite  

Microsoft Academic Search

Four different temperatures (700–1000 °C) were chosen for calcination treatment of as-received hydroxyapatite powder before press forming and sintering to study the effect of calcination on the sintering behaviours. The results show that calcination treatment increases the average particle size and distribution, which changes from trimodal to monomodal. The sintering behaviours were investigated by dilatometry and density measurement. Fluidity of

Horng Yih Juang; Min Hsiung Hon

1996-01-01

327

An innovative technique to simply fabricate ZrO?-HA-TiO? nanostructured layers.  

PubMed

For the first time, ZrO?-HA-TiO? layers were synthesized through EPD-Enhanced MAO (EEMAO) technique in only one step where no supplementary treatment was required. SEM, XRD, EDX, and XPS techniques were employed to propose a correlation between the growth parameters and the physical and chemical properties of the layers. The layers revealed a porous structure where applying higher voltages and/or utilizing higher concentrated electrolytes resulted in formation of wider pores and increasing the zirconium concentration in the layers; meanwhile, prolonging the growth time had the same effects. The layers mainly consisted of anatase, hydroxyapatite, monoclinic ZrO?, and tetragonal ZrO? phases. Increasing the voltage, electrolyte concentration, and time, hydroxyapatite as well as tetragonal ZrO? was decomposed to ?-TCP, monoclinic ZrO?, and ZrO. The nanosized zirconia particles (d = 20-60 nm) were further accumulated on the vicinity of the layers when thicker electrolytes were utilized or higher voltages were applied. Emphasizing on the chemical and electrochemical foundations, a probable formation mechanism was finally put forward. PMID:21514799

Samanipour, F; Bayati, M R; Golestani-Fard, F; Zargar, H R; Troczynski, T; Mirhabibi, A R

2011-08-01

328

Selective laser sintering fabrication of nano-hydroxyapatite/poly-?-caprolactone scaffolds for bone tissue engineering applications  

PubMed Central

The regeneration of functional tissue in osseous defects is a formidable challenge in orthopedic surgery. In the present study, a novel biomimetic composite scaffold, here called nano-hydroxyapatite (HA)/poly-?-caprolactone (PCL) was fabricated using a selective laser sintering technique. The macrostructure, morphology, and mechanical strength of the scaffolds were characterized. Scanning electronic microscopy (SEM) showed that the nano-HA/PCL scaffolds exhibited predesigned, well-ordered macropores and interconnected micropores. The scaffolds have a range of porosity from 78.54% to 70.31%, and a corresponding compressive strength of 1.38 MPa to 3.17 MPa. Human bone marrow stromal cells were seeded onto the nano-HA/PCL or PCL scaffolds and cultured for 28 days in vitro. As indicated by the level of cell attachment and proliferation, the nano-HA/PCL showed excellent biocompatibility, comparable to that of PCL scaffolds. The hydrophilicity, mineralization, alkaline phosphatase activity, and Alizarin Red S staining indicated that the nano-HA/PCL scaffolds are more bioactive than the PCL scaffolds in vitro. Measurements of recombinant human bone morphogenetic protein-2 (rhBMP-2) release kinetics showed that after nano-HA was added, the material increased the rate of rhBMP-2 release. To investigate the in vivo biocompatibility and osteogenesis of the composite scaffolds, both nano-HA/PCL scaffolds and PCL scaffolds were implanted in rabbit femur defects for 3, 6, and 9 weeks. The wounds were studied radiographically and histologically. The in vivo results showed that both nano-HA/PCL composite scaffolds and PCL scaffolds exhibited good biocompatibility. However, the nano-HA/PCL scaffolds enhanced the efficiency of new bone formation more than PCL scaffolds and fulfilled all the basic requirements of bone tissue engineering scaffolds. Thus, they show large potential for use in orthopedic and reconstructive surgery. PMID:24204147

Xia, Yan; Zhou, Panyu; Cheng, Xiaosong; Xie, Yang; Liang, Chong; Li, Chao; Xu, Shuogui

2013-01-01

329

Systematic investigation and in vitro biocompatibility studies on mesoporous europium doped hydroxyapatite  

E-print Network

Systematic investigation and in vitro biocompatibility studies on mesoporous europium doped on europium doped hydroxyapatite (Eu:HAp). In this work, a set of complementary techniques Fourier Transform: nanoparticles, hydroxyapatite, europium, in vitro studies 1. Introduction Hydroxyapatite (HAp) is one

Paris-Sud XI, Université de

330

Coupled Electrorotation of Polymer Microspheres for Microfluidic Sensing and Mixing  

E-print Network

Coupled Electrorotation of Polymer Microspheres for Microfluidic Sensing and Mixing Clyde F. Wilson that is free to rotate. The latter occurs when a microsphere is adjacent to a glass or polymer microstructure

Zare, Richard N.

331

Fabrication and mechanical properties of PLLA/PCL/HA composites via a biomimetic, dip coating, and hot compression procedure.  

PubMed

Currently, the bone-repair biomaterials market is dominated by high modulus metals and their alloys. The problem of stress-shielding, which results from elastic modulus mismatch between these metallic materials and natural bone, has stimulated increasing research into the development of polymer-ceramic composite materials that can more closely match the modulus of bone. In this study, we prepared poly(L: -lactic acid)/hydroxyapatite/poly(epsilon-caprolactone) (PLLA/HA/PCL) composites via a four-step process, which includes surface etching of the fiber, the deposition of the HA coating onto the PLLA fibers through immersion in simulated body fluid (SBF), PCL coating through a dip-coating process, and hot compression molding. The initial HA-coated PLLA fiber had a homogeneous and continuous coating with a gradient structure. The effects of HA: PCL ratio and molding temperature on flexural mechanical properties were studied and both were shown to be important to mechanical properties. Mechanical results showed that at low molding temperatures and up to an HA: PCL volume ratio of 1, the flexural strain decreased while the flexural modulus and strength increased. At higher mold temperatures with a lower viscosity of the PCL a HA: PCL ratio of 1.6 gave similar properties. The process successfully produced composites with flexural moduli near the lower range of bone. Such composites may have clinical use for load bearing bone fixation. PMID:20238147

Charles, L F; Shaw, M T; Olson, J R; Wei, M

2010-06-01

332

Albumin-heparin microspheres as carriers for cytostatic agents  

Microsoft Academic Search

Much work has been done on adriamycin-loaded albumin microspheres (Alb-MS) for chemoembolization [1–4], the rationale being that site-specific drug delivery may increase the therapeutic efficacy of the drug. Alb-Ms are being investigated because of their biocompatibility and because the degradation products of these microspheres are non-toxic. However, these microspheres have some disadvantages (i.e. drug loading during the microsphere preparation, low

H. F. M. Cremers; J. Feijen; G. Kwon; Y. H. Bae; S. W. Kim; H. P. J. M. Noteborn; J. G. McVie

1990-01-01

333

Chitosan microspheres as immobilized dye affinity support for catalase adsorption  

Microsoft Academic Search

Chitosan microsphere (CS) was prepared by phase-inversion method as the support matrices. Cibacron Blue F3GA (CB) was covalently attached to the chitosan microspheres, and thus the novel dye-affinity adsorbent was obtained. These Cibacron Blue F3GA-attached chitosan microspheres (CB-CS) were used in the catalase (CAT) adsorption studies. The maximum CAT adsorption capacity of Cibacron Blue F3GA-attached chitosan microspheres was 28.4mg\\/g at

Jingling Shentu; Jianmin Wu; Weihua Song; Zhishen Jia

2005-01-01

334

Morphological Effects of HA on the Cell Compatibility of Electrospun HA/PLGA Composite Nanofiber Scaffolds  

PubMed Central

Tissue engineering is faced with an uphill challenge to design a platform with appropriate topography and suitable surface chemistry, which could encourage desired cellular activities and guide bone tissue regeneration. To develop such scaffolds, composite nanofiber scaffolds of nHA and sHA with PLGA were fabricated using electrospinning technique. nHA was synthesized using precipitation method, whereas sHA was purchased. The nHA and sHA were suspended in PLGA solution separately and electrospun at optimized electrospinning parameters. The composite nanofiber scaffolds were characterized by FE-SEM, EDX analysis, TEM, XRD analysis, FTIR, and X-ray photoelectron. The potential of the HA/PLGA composite nanofiber as bone scaffolds in terms of their bioactivity and biocompatibility was assessed by culturing the osteoblastic cells onto the composite nanofiber scaffolds. The results from in vitro studies revealed that the nHA/PLGA composite nanofiber scaffolds showed higher cellular adhesion, proliferation, and enhanced osteogenesis performance, along with increased Ca+2 ions release compared to the sHA/PLGA composite nanofiber scaffolds and pristine PLGA nanofiber scaffold. The results show that the structural dependent property of HA might affect its potential as bone scaffold and implantable materials in regenerative medicine and clinical tissue engineering. PMID:24719853

Haider, Adnan; Gupta, Kailash Chandra; Kang, Inn-Kyu

2014-01-01

335

Recent Developments in Suspension Plasma Sprayed Titanium Oxide and Hydroxyapatite Coatings  

NASA Astrophysics Data System (ADS)

The paper aims at reviewing of the recent studies related to the development of suspension plasma sprayed TiO2 and Ca5(PO4)3OH (hydroxyapatite, HA) coatings as well as their multilayer composites obtained onto stainless steel, titanium and aluminum substrates. The total thickness of the coatings was in the range 10 to 150 ?m. The suspensions on the base of distilled water, ethanol and their mixtures were formulated with the use of fine commercial TiO2 pigment crystallized as rutile and HA milled from commercial spray-dried powder or synthesized from calcium nitrate and ammonium phosphate in an optimized reaction. The powder was crystallized as hydroxyapatite. Pneumatic and peristaltic pump liquid feeders were applied. The injection of suspension to the plasma jet was studied carefully with the use of an atomizer injector or a continuous stream one. The injectors were placed outside or inside of the anode-nozzle of the SG-100 plasma torch. The stream of liquid was tested under angle right or slightly backwards with regard to the torch axis. The sprayed deposits were submitted to the phase analysis by the use of x-ray diffraction. The content of anatase and rutile was calculated in the titanium oxide deposits as well as the content of the decomposition phases in the hydroxyapatite ones. The micro-Raman spectroscopy was used to visualize the area of appearance of some phases. Scratch test enabled to characterize the adhesion of the deposits, their microhardness and friction coefficient. The electric properties including electron emission, impedance spectroscopy, and dielectric properties of some coatings were equally tested.

Jaworski, R.; Pawlowski, L.; Pierlot, C.; Roudet, F.; Kozerski, S.; Petit, F.

2010-01-01

336

Subfemtomole detection of small molecules with microsphere sensors  

E-print Network

Subfemtomole detection of small molecules with microsphere sensors Ian M. White, Niranjan M microsphere sensor for detection of small molecules. Using the silica molecules (60 Da) at the sphere quantities at the surface of an optical microsphere sensor. © 2005 Optical Society of America OCIS codes: 230

Fan, Xudong "Sherman"

337

Design of fiber coupled Er3: chalcogenide microsphere amplifier  

E-print Network

Design of fiber coupled Er3: chalcogenide microsphere amplifier via particle swarm optimization Francesco Prudenzano Design of fiber coupled Er3: chalcogenide microsphere amplifier via particle swarm/03/2014 Terms of Use: http://spiedl.org/terms #12;Design of fiber coupled Er3 :chalcogenide microsphere

Boyer, Edmond

338

Fiber laser using a microsphere resonator as a feedback element  

E-print Network

Fiber laser using a microsphere resonator as a feedback element Khanh Kieu and Masud Mansuripur January 12, 2007 We show that a glass microsphere resonator can be used as a wavelength-selective mirror in fiber lasers. Due to their high quality factor Q 108 , microsphere resonators possess a narrow

Kieu, Khanh

339

Silicon-waveguide-coupled high-Q chalcogenide microspheres  

E-print Network

Silicon-waveguide-coupled high-Q chalcogenide microspheres Daniel H. Broaddus,1,* Mark A. Foster,1 glass microspheres through a three-step resistive heating process. We demonstrate quality factors-engineered unclad silicon nanowires. We find that at powers above 1 mW the microspheres exhibit high thermal

Lipson, Michal

340

Fundamental thermal fluctuations in microspheres Michael L. Gorodetsky  

E-print Network

Fundamental thermal fluctuations in microspheres Michael L. Gorodetsky Faculty of Physics, Moscow Microspheres9 are a relatively novel type of optical resonator that uniquely combine small size (from tens localized WGM in the microsphere of radius R 50 m, we obtain the value of the standard deviation

341

Functionalized PCL/HA nanocomposites as microporous membranes for bone regeneration.  

PubMed

In the present work, microporous membranes based on poly(?-caprolactone) (PCL) and PCL functionalized with amine (PCL-DMAEA) or anhydride groups (PCL-MAGMA) were realized by solvent-non solvent phase inversion and proposed for use in Guided Tissue Regeneration (GTR). Nanowhiskers of hydroxyapatite (HA) were also incorporated in the polymer matrix to realize nanocomposite membranes. Scanning Electron Microscopy (SEM) showed improved interfacial adhesion with HA for functionalized polymers, and highlighted substantial differences in the porosity. A relationship between the developed porous structure of the membrane and the chemical nature of grafted groups was proposed. Compared to virgin PCL, hydrophilicity increases for functionalized PCL, while the addition of HA influences significantly the hydrophilic characteristics only in the case of virgin polymer. A significant increase of in vitro degradation rate was found for PCL-MAGMA based membranes, and at lower extent of PCL-DMAEA membranes. The novel materials were investigated regarding their potential as support for cell growth in bone repair using multipotent mesenchymal stromal cells (MSC) as a model. MSC plated onto the various membranes were analyzed in terms of adhesion, proliferation and osteogenic capacity that resulted to be related to chemical as well as porous structure. In particular, PCL-DMAEA and the relative nanocomposite membranes are the most promising in terms of cell-biomaterial interactions. PMID:25579947

Basile, Maria Assunta; d'Ayala, Giovanna Gomez; Malinconico, Mario; Laurienzo, Paola; Coudane, Jean; Nottelet, Benjamin; Ragione, Fulvio Della; Oliva, Adriana

2015-03-01

342

X-ray photo-emission and energy dispersive spectroscopy of HA coated titanium  

SciTech Connect

The purpose of this study was to determine the chemical composition changes of hydroxyapatite (HA) coated titanium using surface analysis (x-ray photo-emission) and bulk analysis (energy dispersive spectroscopy). The specimens examined were controls, 30 minutes and 3 hours aged specimens in distilled water or 0.2M sodium phosphate buffer (pH 7.2) at room temperature. Each x-ray photo-emission cycle consisted of 3 scans followed by argon sputtering for 10 minutes for a total of usually 20 cycles, corresponding to a sampling depth of {approximately} 1500 {angstrom}. The energy dispersive spectroscopy analysis was on a 110 by 90 {mu}m area for 500 sec. Scanning electron microscopy examination showed crystal formation (3P{sub 2}O{sub 5}*2CAO*?H{sub 2}O by energy dispersive spectroscopy analysis) on the HA coating for the specimens aged in sodium phosphate buffer. The x-ray photo-emission results indicated the oxidation effect of water on the titanium (as TiO{sub 2}) and the effect of the buffer to increase the surface concentration of phosphorous. No differences in the chemical composition were observed by energy dispersive spectroscopy analysis. The crystal growth was only observed for the sodium phosphate buffer specimens and only on the HA surface.

Drummond, J.L.; Steinberg, A.D. [Univ. of Illinois, Chicago, IL (United States); Krauss, A.R. [Argonne National Lab., IL (United States)] [and others

1997-08-01

343

Subcutaneous-induced membranes have no osteoinductive effect on macroporous HA-TCP in vivo.  

PubMed

Induced Membranes Technique was first described to enhance bone reconstruction of large osseous defects. Previous in vitro studies established their osteoinductive potential, due to the presence of opteoblasts precursors and to high amounts of growth factors contained within. The purpose of this study was to test in vivo the osteoinductive properties of induced membranes on a macroporous HA-TCP in a nonosseous subcutaneous site. Subcutaneous-induced membranes were obtained in 21 rabbits; 1 month later, the membranes were filled with a biphasic calcium phosphate material composed of 75% hydroxyapatite (HA) and 25% beta-tricalcium phosphate associated or not with autograft. Histological and immunohistochemical studies were performed on membrane biopsies. Undecalcified and decalcified sections were qualitatively and quantitatively analyzed. (45)Ca uptake was observed and quantified on the sections using microimager analysis. Dense vascularity was found in the induced membranes. New bone formation was detected in the HA-TCP + autograft samples and increased significantly from 3 to 6 months (p < 0.05). No bone was detected in the biomaterial graft alone in the induced membranes at any time. This study showed that induced membranes placed in a nonosseous site have no osteoinductive properties on a macroporous biphasic calcium phosphate biomaterial. PMID:18683892

Catros, Sylvain; Zwetyenga, Narcisse; Bareille, Reine; Brouillaud, Brigitte; Renard, Martine; Amédée, Joelle; Fricain, Jean-Christophe

2009-02-01

344

Fracture modes under uniaxial compression in hydroxyapatite scaffolds fabricated by robocasting.  

PubMed

The fracture modes of hydroxyapatite (HA) scaffolds fabricated by direct-write assembly (robocasting) are analyzed in this work. Concentrated HA inks with suitable viscoelastic properties were developed to enable the fabrication of prototype structures consisting of a 3-D square mesh of interpenetrating rods. The fracture behavior of these model scaffolds under compressive stresses is determined from in situ uniaxial tests performed in two different directions: perpendicular to the rods and along one of the rod directions. The results are analyzed in terms of the stress field calculated by finite element modeling (FEM). This analysis provides valuable insight into the mechanical behavior of scaffolds for bone tissue engineering applications fabricated by robocasting. PMID:17508415

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

2007-12-01

345

The use of Vicryl mesh (polyglactin 910) for implantation of hydroxyapatite orbital implants.  

PubMed

Hydroxyapatite (HA) implants currently are most commonly wrapped in donor sclera before implantation to facilitate placement within the orbit and allow attachment of the extraocular muscles. Although the risk of acquiring a transmittable disease through donor sclera is extremely low, some individuals remain concerned about receiving nonautologous material. As an alternative to sclera, autologous temporalis fascia, or autologous fascia lata, we have been wrapping HA in "Vicryl mesh" before insertion into the orbit. The Vicryl mesh-wrapped implant goes into the socket readily, allows one to easily attach the extraocular muscles, and has no risk of transmittable disease. In addition, the Vicryl mesh is readily available at most hospitals and is dissolvable. PMID:7654624

Jordan, D R; Allen, L H; Ells, A; Gilberg, S; Brownstein, S; Munro, S; Grahovac, S; Raymond, F

1995-06-01

346

Adding MgO nanoparticles to hydroxyapatite-PLLA nanocomposites for improved bone tissue engineering applications.  

PubMed

Magnesium plays an important role in the body, mediating cell-extracellular matrix interactions and bone apatite structure and density. This study investigated, for the first time, the effects of adding magnesium oxide (MgO) nanoparticles to poly (l-lactic acid) (PLLA) and to hydroxyapatite (HA) nanoparticle-PLLA composites for orthopedic tissue engineering applications. Results showed that MgO nanoparticles significantly enhanced osteoblast adhesion and proliferation on HA-PLLA nanocomposites while maintaining mechanical properties (Young's modulus ?1000MPa) suitable for cancellous bone applications. Additionally, osteoblasts (or bone-forming cells) cultured in the supernatant of degrading nanocomposites showed improved proliferation in the presence of magnesium, indicating that the increased alkalinity of solutions containing MgO nanocomposites had no toxic effects towards cells. These results together indicated the promise of further studying MgO nanoparticles as additive materials to polymers to enhance the integration of implanted biomaterials with bone. PMID:25523875

Hickey, Daniel J; Ercan, Batur; Sun, Linlin; Webster, Thomas J

2015-03-01

347

Comparison of hydroxyapatite- and porous-coated stems in total hip replacement.  

PubMed

24 patients underwent bilateral hip replacement, using the SROM modular system (Depuy Johnson & Johnson, MA, USA) with the porous-coated sleeve in one hip and an HA-coated sleeve in the other. 20 patients were followed for at least 4 years with clinical and radiographic evaluations. We found no difference between the two sides as regards the time of disappearance of thigh pain and hip scores. Radiographs showed a buttress sign in 18 HA-coated and 15 porous coated stems. There were no differences in the serial bone-remodeling pattern around the proximal sleeve and measurement of wear volume between the two groups. In the short- to medium-term, our findings support the view that the hydroxyapatite-coated femoral stem has no advantages over those with porous coating. PMID:12899544

Park, Youn-Soo; Lee, Jong-Yoon; Yun, Sang-Hak; Jung, Min-Wook; Oh, Irvin

2003-06-01

348

Ferroelectric Polarization in Nanocrystalline Hydroxyapatite Thin Films on Silicon  

PubMed Central

Hydroxyapatite nanocrystals in natural form are a major component of bone- a known piezoelectric material. Synthetic hydroxyapatite is widely used in bone grafts and prosthetic pyroelectric coatings as it binds strongly with natural bone. Nanocrystalline synthetic hydroxyapatite films have recently been found to exhibit strong piezoelectricity and pyroelectricity. While a spontaneous polarization in hydroxyapatite has been predicted since 2005, the reversibility of this polarization (i.e. ferroelectricity) requires experimental evidence. Here we use piezoresponse force microscopy to demonstrate that nanocrystalline hydroxyapatite indeed exhibits ferroelectricity: a reversal of polarization under an electrical field. This finding will strengthen investigations on the role of electrical polarization in biomineralization and bone-density related diseases. As hydroxyapatite is one of the most common biocompatible materials, our findings will also stimulate systematic exploration of lead and rare-metal free ferroelectric devices for potential applications in areas as diverse as in vivo and ex vivo energy harvesting, biosensing and electronics. PMID:23884324

Lang, S. B.; Tofail, S. A. M.; Kholkin, A. L.; Wojta?, M.; Gregor, M.; Gandhi, A. A.; Wang, Y.; Bauer, S.; Krause, M.; Plecenik, A.

2013-01-01

349

Formulation and Evaluation of 5FU Loaded Eudragit Microspheres: Effect of Various Eudragit on Micromeretic Properties of Microspheres  

Microsoft Academic Search

The aim of the present study was to prepare and evaluate microspheres of Eudragit (RS, RL and RSPO) containing an anticancer drug 5-FU. Microspheres were prepared by O\\/O solvent evaporation method using a acetone\\/liquid paraffin system. Magnesium stearate was used as the droplet stabilizer and n-hexane was added to harden the microspheres. The prepared microspheres were characterized for their micromeretic

Subhash Vaghani; S. Vasanti; Kiran Chaturvedi; C. S. Satish; S. J. Shankar

2008-01-01

350

Investigation of the antimicrobial activity and biocompatibility of magnesium alloy coated with HA and antimicrobial peptide.  

PubMed

Implant-associated infection is one of the biggest problems in orthopedic surgery. Antimicrobial peptides (AMPs) are well-known components of the innate immunity and less susceptible to the development of pathogen resistance compared to conventional antibiotics. Magnesium alloys as potential biodegradable bone implants have been received much attention in biomaterials field. This study investigated the deposition of calcium phosphate (CaP) coatings and loading of AMPs on the magnesium alloy surface by a biomimetic method. Scanning electron microscope (SEM) results presented that a microporous and plate-like CaP coating was processed on the magnesium alloy surface. X-ray diffractometry (XRD) and Fourier transform infrared spectroscopy (FTIR) analysis showed the main component of coating was hydroxyapatite (HA). Degradation assay in vitro showed that the HA coating deposited onto the magnesium alloy was corroded more slowly than the bare one. The amount of AMP loaded in the HA coating was 11.16 ± 1.99 ?g/cm(2). The AMP loaded onto HA coatings had slow release for 7 days. The AMP-loaded coating showed antimicrobial activity against Staphylococcus aureus. Its bacterial inhibition rate exceeded 50 % after 4 days and the antibacterial effect was sustained for 7 days. The coated magnesium alloys loaded with AMP could improve rat bone marrow mesenchymal stem cells (rBMMSCs) proliferation. Furthermore, it could also promote alkaline phosphatase (ALP) activity of rBMMSCs. Both radiographic evaluation and histopathology analysis demonstrated that implantation of the coated magnesium alloy into the rabbit femoral condyle had promoted bone repair and showed anti-inflammatory effect. The results showed that the AMP loaded onto HA coatings on the magnesium alloy surface could be considered an ideal orthopedic implant against S. aureus infection. PMID:25631264

Tian, Jinhuan; Shen, Si; Zhou, Changren; Dang, Xiangli; Jiao, Yanpeng; Li, Lihua; Ding, Shan; Li, Hong

2015-02-01

351

The pathway to intelligent implants: osteoblast response to nano silicon-doped hydroxyapatite patterning  

PubMed Central

Bioactive hydroxyapatite (HA) with addition of silicon (Si) in the crystal structure (silicon-doped hydroxyapatite (SiHA)) has become a highly attractive alternative to conventional HA in bone replacement owing to the significant improvement in the in vivo bioactivity and osteoconductivity. Nanometre-scaled SiHA (nanoSiHA), which closely resembles the size of bone mineral, has been synthesized in this study. Thus, the silicon addition provides an extra chemical cue to stimulate and enhance bone formation for new generation coatings, and the next stage in metallic implantation design is to further improve cellular adhesion and proliferation by control of cell alignment. Topography has been found to provide a powerful set of signals for cells and form contact guidance. Using the recently developed novel technique of template-assisted electrohydrodynamic atomization (TAEA), patterns of pillars and tracks of various dimensions of nanoSiHA were achieved. Modifying the parameters of TAEA, the resolution of pattern structures was controlled, enabling the topography of a substrate to be modified accordingly. Spray time, flow rate and distance between the needle and substrate were varied to improve the pattern formation of pillars and tracks. The 15 min deposition time provided the most consistent patterned topography with a distance of 50 mm and flow rate of 4 µl min?1. A titanium substrate was patterned with pillars and tracks of varying widths, line lengths and distances under the optimized TAEA processing condition. A fast bone-like apatite formation rate was found on nanoSiHA after immersion in simulated body fluid, thus demonstrating its high in vitro bioactivity. Primary human osteoblast (HOB) cells responded to SiHA patterns by stretching of the filopodia between track and pillar, attaching to the apex of the pillar pattern and stretching between two. HOB cells responded to the track pattern by elongating along and between the track, and the length of HOB cells was proportional to the gaps between track patterns, but this relationship was not observed on the pillar patterns. The study has therefore provided an insight for future design of next generation implant surfaces to control and guide cellular responses, while TAEA patterning provides a controllable technique to provide topography to medical implants. PMID:21208969

Munir, G.; Koller, G.; Di Silvio, L.; Edirisinghe, M. J.; Bonfield, W.; Huang, J.

2011-01-01

352

The survival of hydroxyapatite-coated implants is questioned  

Microsoft Academic Search

Question: Do hydroxyapatite implants last as long as titanium implants?Objective Identify and critically review human clinical trials that examined the survival of hydroxyapatite-coated implants.Data sources Medline (1990–1999) was searched using the keywords ‘hydroxyapatite’ or ‘hydroxylapatite’.Study selection Papers were included that were written in English and met the criteria that they: included at least 10 patients; at least a 6-month follow-up;

Nico Creugers

2002-01-01

353

Wettability patterning of hydroxyapatite nanobioceramics induced by surface potential modification  

NASA Astrophysics Data System (ADS)

Hydroxyapatite is known as a substrate for effective adhesion of various biological cells and bacteria as well implantable biomimetic material replacing defective bone tissues. It is found that low energy electron irradiation induces its strong surface potential variation and gives rise to pronounced wettability modification. The found electron-modulation method of the hydroxyapatite wettability enables both wettability switching and its microscopic patterning, which may be used for fabrication of spatially arrayed hydroxyapatite for biological cells immobilization, gene transfer, etc.

Aronov, D.; Rosenman, G.; Karlov, A.; Shashkin, A.

2006-04-01

354

Hydroxyapatite cranioplasty in fibrous dysplasia of the skull.  

PubMed

We describe the case of a woman who had complained of worsening headache during the previous year. Analysis of computed tomography imaging and biopsy led to a diagnosis of fibrous dysplasia of the skull. A symptomatic frontal bone lesion was removed, and the resulting defect was repaired with hydroxyapatite cement. Hydroxyapatite cement has several advantages over hydroxyapatite ceramic blocks and granules, and it is particularly well suited for calvarial reconstruction. PMID:11209516

Vories, A; Mansfield, E

2001-01-01

355

Nanocrystalline hydroxyapatite for bone repair: an animal study  

Microsoft Academic Search

Hydroxyapatite has become the most common material to replace bone or to guide its regeneration. Nanocrystalline hydroxyapatite\\u000a suspension had been introduced in the clinical use recently under the assumption that small dimension of crystals could improve\\u000a resorption. We studied the resorption and osteointegration of the nanocrystalline hydroxyapatite Ostim® in a rabbit model. The material was implanted either alone or in

J. BrandtS; S. Henning; G. Michler; W. Hein; A. Bernstein; M. Schulz

2010-01-01

356

Use of “custom made” porous hydroxyapatite implants for cranioplasty: postoperative analysis of complications in 1549 patients  

PubMed Central

Background: Cranioplasty is a surgical intervention aimed at reestablishing the integrity of skull defects, and should be considered the conclusion of a surgical act that began with bone flap removal. Autologous bone is still considered the treatment of choice for cranioplasty. An alternative choice is bioceramic porous hydroxyapatite (HA) as it is one of the materials that meets and comes closest to the biomimetic characteristics of bone. Methods: The authors analyzed the clinical charts, compiled by the neurosurgeon, of all patients treated with custom-made porous HA devices (Custom Bone Service Fin-Ceramica, Faenza) from which epidemiological and pathological data as well as material-related complications were extrapolated. Results: From November 1997 to December 2010, 1549 patients underwent cranioplasty with the implantation of 1608 custom-made porous HA devices. HA was used in 53.8% of patients for decompressive craniectomy after trauma or intracranial hemorrhage, while the remaining cases were for treated for comminuted fracture, cutaneous or osseous resection, cranial malformation, autologous bone reabsorption or infection or rejection of previously implanted material. The incidence of adverse events in patients treated for cranioplasty, as first line treatment was 4.78% (56 events/1171 patients), and 5.02%, (19 events/378 patients) at second line. Conclusion: This study demonstrates that HA is a safe and effective material, is well tolerated in both adult and pediatric patients, and meets the requirements necessary to repair craniolacunia. PMID:23493459

Stefini, Roberto; Esposito, Giacomo; Zanotti, Bruno; Iaccarino, Corrado; Fontanella, Marco Maria; Servadei, Franco

2013-01-01

357

Mechanical, In Vitro Antimicrobial and Biological Properties of Plasma Sprayed Silver-Doped Hydroxyapatite Coating  

PubMed Central

Implant related infection is one of the key concerns in total joint hip arthroplasties. In order to reduce bacterial adhesion, silver (Ag) / silver oxide (Ag2O) doping was used in plasma sprayed hydroxyapatite (HA) coating on titanium substrate. HA powder was doped with 2.0, 4.0 and 6.0 wt% Ag, heat treated at 800 °C and used for plasma spray coating using a 30 kW plasma spray system, equipped with supersonic nozzle. Application of supersonic plasma nozzle significantly reduced phase decomposition and amorphous phase formation in the HA coatings as evident by X-ray diffraction (XRD) study and Fourier transformed infrared spectroscopic (FTIR) analysis. Adhesive bond strength of more than 15 MPa ensured the mechanical integrity of the coatings. Resistance against bacterial adhesion of the coatings was determined by challenging them against Pseudomonas Aeruginosa (PAO1). Live/Dead staining of the adherent bacteria on the coating surfaces indicated a significant reduction in bacterial adhesion due to the presence of Ag. In vitro cell-material interactions and alkaline phosphatase (ALP) protein expressions were evaluated by culturing human fetal osteoblast cells (hFOB). Present results suggest that the plasma sprayed HA coatings doped with an optimum amount of Ag can have excellent antimicrobial property without altering mechanical property of the Ag doped HA coatings. PMID:22313742

Roy, Mangal; Fielding, Gary A.; Beyenal, Haluk; Bandyopadhyay, Amit; Bose, Susmita

2012-01-01

358

Biological evaluation of porous aliphatic polyurethane/hydroxyapatite composite scaffolds for bone tissue engineering.  

PubMed

Biomaterial scaffolds meant to function as supporting structures to osteogenic cells play a pivotal role in bone tissue engineering. Recently, we synthesized an aliphatic polyurethane (PU) scaffold via a foaming method using non-toxic components. Through this procedure a uniform interconnected porous structure was created. Furthermore, hydroxyapatite (HA) particles were introduced into this process to increase the bioactivity of the PU matrix. To evaluate the biological performances of these PU-based scaffolds, their influence on in vitro cellular behavior and in vivo bone forming capacity of the engineered cell-scaffold constructs was investigated in this study. A simulated body fluid test demonstrated that the incorporation of 40 wt % HA particles significantly promoted the biomineralization ability of the PU scaffolds. Enhanced in vitro proliferation and osteogenic differentiation of the seeded mesenchymal stem cells were also observed on the PU/HA composite. Next, the cell-scaffold constructs were implanted subcutaneously in a nude mice model. After 8 weeks, a considerable amount of vascularized bone tissue with initial marrow stroma development was generated in both PU and PU/HA40 scaffold. In conclusion, the PU/HA composite is a potential scaffold for bone regeneration applications. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2014. PMID:25370308

Yang, Wanxun; Both, Sanne K; Zuo, Yi; Birgani, Zeinab Tahmasebi; Habibovic, Pamela; Li, Yubao; Jansen, John A; Yang, Fang

2014-11-01

359

Hydroxyapatite nanoparticle-containing scaffolds for the study of breast cancer bone metastasis  

PubMed Central

Breast cancer frequently metastasizes to bone, where it leads to secondary tumor growth, osteolytic bone degradation, and poor clinical prognosis. Hydroxyapatite Ca10(PO4)6(OH)2 (HA), a mineral closely related to the inorganic component of bone, may be implicated in these processes. However, it is currently unclear how the nanoscale materials properties of bone mineral, such as particle size and crystallinity, which change as a result of osteolytic bone remodeling, affect metastatic breast cancer. We have developed a two-step hydrothermal synthesis method to obtain HA nanoparticles with narrow size distributions and varying crystallinity. These nanoparticles were incorporated into gas-foamed/particulate leached poly(lactide-co-glycolide) scaffolds, which were seeded with metastatic breast cancer cells to create mineral-containing scaffolds for the study of breast cancer bone metastasis. Our results suggest that smaller, poorly-crystalline HA nanoparticles promote greater adsorption of adhesive serum proteins and enhance breast tumor cell adhesion and growth relative to larger, more crystalline nanoparticles. Conversely, the larger, more crystalline HA nanoparticles stimulate enhanced expression of the osteolytic factor interleukin-8 (IL-8). Our data suggest an important role for nanoscale HA properties in the vicious cycle of bone metastasis and indicate that mineral-containing tumor models may be excellent tools to study cancer biology and to define design parameters for non-tumorigenic mineral-containing or mineralized matrices for bone regeneration. PMID:21507478

Pathi, Siddharth P.; Lin, Debra D.W.; Dorvee, Jason R.; Estroff, Lara A.; Fischbach, Claudia

2012-01-01

360

The development of fibronectin-functionalised hydroxyapatite coatings to improve dermal fibroblast attachment in vitro.  

PubMed

The success of long-term transcutaneous implants depends on dermal attachment to prevent downgrowth of the epithelium and infection. Hydroxyapatite (HA) coatings and fibronectin (Fn) have independently been shown to regulate fibroblast activity and improve attachment. In an attempt to enhance this phenomenon we adsorbed Fn onto HA-coated substrates. Our study was designed to test the hypothesis that adsorption of Fn onto HA produces a surface that will increase the attachment of dermal fibroblasts better than HA alone or titanium alloy controls. Iodinated Fn was used to investigate the durability of the protein coating and a bioassay using human dermal fibroblasts was performed to assess the effects of the coating on cell attachment. Cell attachment data were compared with those for HA alone and titanium alloy controls at one, four and 24 hours. Protein attachment peaked within one hour of incubation and the maximum binding efficiency was achieved with an initial droplet of 1000 ng. We showed that after 24 hours one-fifth of the initial Fn coating remained on the substrates, and this resulted in a significant, three-, four-, and sevenfold increase in dermal fibroblast attachment strength compared to uncoated controls at one, four and 24 hours, respectively. PMID:22434476

Pendegrass, C J; El-Husseiny, M; Blunn, G W

2012-04-01

361

A complete structural performance analysis and modelling of hydroxyapatite scaffolds with variable porosity.  

PubMed

The use of hydroxyapatite (HA) scaffolds for bone regeneration is an alternative procedure to treat bone defects due to cancer, other diseases or traumas. Although the use of HA has been widely studied in the literature, there are still some disparities regarding its mechanical performance. This paper presents a complete analysis of the structural performance of porous HA scaffolds based on experimental tests, numerical simulations and theoretical studies. HA scaffolds with variable porosity were considered and fabricated by the water-soluble polymer method, using poly vinyl alcohol as pore former. These scaffolds were then characterised by scanning electron microscopy, stereo microscopy, X-ray diffraction, porosity analysis and mechanical tests. Different scaffold models were proposed and analysed by the finite element method to obtain numerical predictions of the mechanical properties. Also theoretical predictions based on the (Gibson LJ, Ashby MF. 1988. Cellular solids: structure and properties. Oxford: Pergamon Press) model were obtained. Finally the experimental, numerical and theoretical results were compared. From this comparison, it was observed that the proposed numerical and theoretical models can be used to predict, with adequate accuracy, the mechanical performance of HA scaffolds for different porosity values. PMID:24579777

Gallegos-Nieto, Enrique; Medellín-Castillo, Hugo I; de Lange, Dirk F

2015-08-01

362

Mechanical, in vitro antimicrobial, and biological properties of plasma-sprayed silver-doped hydroxyapatite coating.  

PubMed

Implant-related infection is one of the key concerns in total joint hip arthroplasties. To reduce bacterial adhesion, we used silver (Ag)/silver oxide (Ag(2)O) doping in plasma sprayed hydroxyapatite (HA) coating on titanium substrate. HA powder was doped with 2.0, 4.0, and 6.0 wt % Ag, heat-treated at 800 °C and used for plasma spray coating using a 30 kW plasma spray system, equipped with supersonic nozzle. Application of supersonic plasma nozzle significantly reduced phase decomposition and amorphous phase formation in the HA coatings as evident by X-ray diffraction (XRD) study and Fourier transformed infrared spectroscopic (FTIR) analysis. Adhesive bond strength of more than 15 MPa ensured the mechanical integrity of the coatings. Resistance against bacterial adhesion of the coatings was determined by challenging them against Pseudomonas aeruginosa (PAO1). Live/dead staining of the adherent bacteria on the coating surfaces indicated a significant reduction in bacterial adhesion due to the presence of Ag. In vitro cell-material interactions and alkaline phosphatase (ALP) protein expressions were evaluated by culturing human fetal osteoblast cells (hFOB). Our results suggest that the plasma-sprayed HA coatings doped with an optimum amount of Ag can have excellent antimicrobial property without altering mechanical property of the Ag-doped HA coatings. PMID:22313742

Roy, Mangal; Fielding, Gary A; Beyenal, Haluk; Bandyopadhyay, Amit; Bose, Susmita

2012-03-01

363

Preparation, characterization, and in vitro osteoblast functions of a nano-hydroxyapatite/polyetheretherketone biocomposite as orthopedic implant material  

PubMed Central

A bioactive composite was prepared by incorporating 40 wt% nano-hydroxyapatite (nHA) into polyetheretherketone (PEEK) through a process of compounding, injection, and molding. The mechanical and surface properties of the nHA/PEEK composite were characterized, and the in vitro osteoblast functions in the composite were investigated. The mechanical properties (elastic modulus and compressive strength) of the nHA/PEEK composite increased significantly, while the tensile strength decreased slightly as compared with PEEK. Further, the addition of nHA into PEEK increased the surface roughness and hydrophilicity of the nHA/PEEK composite. In cell tests, compared with PEEK and ultra-high-molecular-weight polyethylene, it was found that the nHA/PEEK composite could promote the functions of MC3T3-E1 cells, including cell attachment, spreading, proliferation, alkaline phosphatase activity, calcium nodule formation, and expression of osteogenic differentiation-related genes. Incorporation of nHA into PEEK greatly improved the bioperformance of PEEK. The nHA/PEEK composite might be a promising orthopedic implant material. PMID:25170265

Ma, Rui; Tang, Songchao; Tan, Honglue; Lin, Wentao; Wang, Yugang; Wei, Jie; Zhao, Liming; Tang, Tingting

2014-01-01

364

Nanostructured hydroxyapatite/poly(lactic-co-glycolic acid) composite coating for controlling magnesium degradation in simulated body fluid.  

PubMed

Biodegradable magnesium (Mg) and its alloys have many attractive properties (e.g. comparable mechanical properties to cortical bone) for orthopedic implant applications, but they degrade too rapidly in the human body to meet clinical requirements. Nanostructured hydroxyapatite (nHA)/poly(lactic-co-glycolic acid) (PLGA) composite coatings provide synergistic properties for controlling degradation of Mg-based substrates and improving bone-implant integration. In this study, nHA/PLGA composites were spin coated onto Mg-based substrates and the results showed that the nHA/PLGA coatings retained nano-scale features with nHA dispersed in PLGA matrix. In comparison with non-coated Mg, the nHA/PLGA composite coated Mg increased the corrosion potential and decreased the corrosion current in revised simulated body fluid (rSBF). After 24 h of immersion in rSBF, increased calcium phosphate (CaP) deposition and formation of Mg-substituted CaP rosettes were observed on the surface of the nHA/PLGA coated Mg, indicating greater bioactivity. In contrast, no significant CaP was deposited on the PLGA coated Mg. Since both PLGA coating and nHA/PLGA coating showed some degree of delamination from Mg-based substrates during extended immersion in rSBF, the coating processing and properties should be further optimized in order to take full advantage of biodegradable Mg and nHA/PLGA nanocomposites for orthopedic applications. PMID:23975041

Johnson, Ian; Akari, Khalid; Liu, Huinan

2013-09-20

365

Bone Regeneration of Hydroxyapatite/Alumina Bilayered Scaffold with 3?mm Passage-Like Medullary Canal in Canine Tibia Model  

PubMed Central

The aim of this study was to evaluate the bone regeneration of hydroxyapatite (HA)/alumina bilayered scaffold with a 3?mm passage-like medullary canal in a beagle tibia model. A porous HA/alumina scaffold was fabricated using a polymeric template-coating technique. HA/alumina scaffold dimensions were 10?mm in outer diameter, 20?mm in length, and with either a 3?mm passage or no passage. A 20?mm segmental defect was induced using an oscillating saw through the diaphysis of the beagle tibia. The defects of six beagles were filled with HA/alumina bilayered scaffolds with a 3?mm passage or without. The segmental defect was fixated using one bone plate and six screws. Bone regeneration within the HA/alumina scaffolds was observed at eight weeks after implantation. The evaluation of bone regeneration within the scaffolds after implantation in a beagle tibia was performed using radiography, computerized tomography (CT), micro-CT, and fluorescence microscopy. New bone successfully formed in the tibia defects treated with 3?mm passage HA/alumina scaffolds compared to without-passage HA/alumina scaffolds. It was concluded that the HA/alumina bilayered scaffold with 3?mm passage-like medullary canal was instrumental in inducing host-scaffold engraftment of the defect as well as distributing the newly formed bone throughout the scaffold at 8 weeks after implantation.

Kim, Jong Min; Son, Jun Sik; Kim, Gonhyung; Choi, Seok Hwa

2015-01-01

366

Accelerated bone growth in vitro by the conjugation of BMP2 peptide with hydroxyapatite on titanium alloy.  

PubMed

Titanium alloys have been widely used in orthopedic practice due to their inherent bioactivity, however it is still insufficient to truly and reliably incorporate into living bone. In this work, polydopamine film was employed to induce the growth of hydroxyapatite (HA) on titanium alloy to enhance its osteoconductivity. Bone morphogenetic protein-2 (BMP2) peptide was absorbed into the HA particles for osteoinductivity. The precipitation of HA and the existence of BMP2 peptide were examined by X-ray diffraction, X-ray photoelectron spectroscopy and fluorescence microscopy. The dissolution of HA and the release of BMP2 peptide were monitored by measuring the concentrations of calcium ions and BMP2 peptide in phosphate buffered saline solution, respectively. The effect of BMP2 peptide incorporated into HA coating on bone growth was evaluated in vitro by cell culture tests, including cell attachment, alkaline phosphatase (ALP) activity, and gene expression. The results show that the HA particles grown on the substrate are mediated by the polydopamine film. The BMP2 peptide is distributed uniformly on HA-coated substrate and released in a sustained manner. Moreover, the conjunction of HA and BMP2 peptide increases cell adhesion, ALP activity and gene expression of osteogenic markers, which are potentially useful in the development of enhanced orthopedic medical devices. PMID:24304498

Cai, Yanli; Wang, Xiaoyan; Poh, Chye Khoon; Tan, Hark Chuan; Soe, Min Tun; Zhang, Sam; Wang, Wilson

2014-04-01

367

A biodegradable gentamicin-hydroxyapatite-coating for infection prophylaxis in cementless hip prostheses.  

PubMed

A degradable, poly (lactic-co-glycolic acid) (PLGA), gentamicin-loaded prophylactic coating for hydroxyapatite (HA)-coated cementless hip prostheses is developed with similar antibacterial efficacy as offered by gentamicin-loaded cements for fixing traditional, cemented prostheses in bone. We describe the development pathway, from in vitro investigation of antibiotic release and antibacterial properties of this PLGA-gentamicin-HA-coating in different in vitro models to an evaluation of its efficacy in preventing implant-related infection in rabbits. Bone in-growth in the absence and presence of the coating was investigated in a canine model. The PLGA-gentamicin-HA-coating showed high-burst release, with antibacterial efficacy in agar-assays completely disappearing after 4 days, minimising risk of inducing antibiotic resistance. Gentamicin-sensitive and gentamicin-resistant staphylococci were killed by the antibiotic-loaded coating, in a simulated prosthesis-related interfacial gap. PLGA-gentamicin-HA-coatings prevented growth of bioluminescent staphylococci around a miniature-stem mounted in bacterially contaminated agar, as observed using bio-optical imaging. PLGA-gentamicin-HA-coated pins inserted in bacterially contaminated medullary canals in rabbits caused a statistically significant reduction in infection rates compared to HA-coated pins without gentamicin. Bone ingrowth to PLGA-gentamicin-HA-coated pins, in condylar defects of Beagle dogs was not impaired by the presence of the degradable, gentamicin-loaded coating. In conclusion, the PLGA-gentamicin-HA-coating constitutes an effective strategy for infection prophylaxis in cementless prostheses. PMID:25552428

Neut, D; Dijkstra, R J; Thompson, J I; Kavanagh, C; van der Mei, H C; Busscher, H J

2015-01-01

368

Electrospun fibrous scaffolds combined with nanoscale hydroxyapatite induce osteogenic differentiation of human periodontal ligament cells.  

PubMed

Periodontal repair is a complex process in which regeneration of alveolar bone is a vital component. The aim of this study was to develop a biodegradable scaffold with good biocompatibility and osteoinductive ability. Two types of composite fibrous scaffolds were produced by electrospinning, ie, type I collagen/poly(?-caprolactone) (COL/PCL) and type I collagen/poly(?-caprolactone)/nanoscale hydroxyapatite (COL/PCL/nHA) with an average fiber diameter of about 377 nm. After a simulated body fluid (SBF) immersion test, the COL/PCL/nHA-SBF scaffold developed a rough surface because of the calcium phosphate deposited on the fibers, suggesting that the presence of nHA promoted the mineralization potential of the scaffold. Energy dispersive X-ray spectroscopy clearly showed the calcium and phosphorus content in the COL/PCL/nHA and COL/PCL/nHA-SBF scaffolds, confirming the findings of nHA and calcium phosphate precipitation on scanning electron micrographs. Water contact analysis revealed that nHA could improve the hydrophilic nature of the COL/PCL/nHA-SBF scaffold. The morphology of periodontal ligament cells cultured on COL/PCL-SBF and COL/PCL/nHA-SBF was evaluated by scanning electron microscopy. The results showed that cells adhered to either type of scaffold and were slightly spindle-shaped in the beginning, then extended gradually with stretched filopodia, indicating an ability to fill the fiber pores. A Cell Counting Kit-8 assay showed that both scaffolds supported cell proliferation. However, real-time quantitative polymerase chain reaction analysis showed that expression of the bone-related markers, alkaline phosphatase and osteocalcin, was upregulated only on the COL/PCL/nHA-SBF scaffold, indicating that this scaffold had the ability to induce osteogenic differentiation of periodontal ligament cells. In this study, COL/PCL/nHA-SBF produced by electrospinning followed by biomimetic mineralization had combined electrospun fibers with nHA in it. This scaffold has good biocompatibility and osteoinductive ability as a result of the characteristics of nHA, so could be innovatively applied to periodontal tissue engineering as a potential scaffold. PMID:25206304

Wu, Xiaonan; Miao, Leiying; Yao, Yingfang; Wu, Wenlei; Liu, Yu; Chen, Xiaofeng; Sun, Weibin

2014-01-01

369

Electrospun fibrous scaffolds combined with nanoscale hydroxyapatite induce osteogenic differentiation of human periodontal ligament cells  

PubMed Central

Periodontal repair is a complex process in which regeneration of alveolar bone is a vital component. The aim of this study was to develop a biodegradable scaffold with good biocompatibility and osteoinductive ability. Two types of composite fibrous scaffolds were produced by electrospinning, ie, type I collagen/poly(?-caprolactone) (COL/PCL) and type I collagen/poly(?-caprolactone)/nanoscale hydroxyapatite (COL/PCL/nHA) with an average fiber diameter of about 377 nm. After a simulated body fluid (SBF) immersion test, the COL/PCL/nHA-SBF scaffold developed a rough surface because of the calcium phosphate deposited on the fibers, suggesting that the presence of nHA promoted the mineralization potential of the scaffold. Energy dispersive X-ray spectroscopy clearly showed the calcium and phosphorus content in the COL/PCL/nHA and COL/PCL/nHA-SBF scaffolds, confirming the findings of nHA and calcium phosphate precipitation on scanning electron micrographs. Water contact analysis revealed that nHA could improve the hydrophilic nature of the COL/PCL/nHA-SBF scaffold. The morphology of periodontal ligament cells cultured on COL/PCL-SBF and COL/PCL/nHA-SBF was evaluated by scanning electron microscopy. The results showed that cells adhered to either type of scaffold and were slightly spindle-shaped in the beginning, then extended gradually with stretched filopodia, indicating an ability to fill the fiber pores. A Cell Counting Kit-8 assay showed that both scaffolds supported cell proliferation. However, real-time quantitative polymerase chain reaction analysis showed that expression of the bone-related markers, alkaline phosphatase and osteocalcin, was upregulated only on the COL/PCL/nHA-SBF scaffold, indicating that this scaffold had the ability to induce osteogenic differentiation of periodontal ligament cells. In this study, COL/PCL/nHA-SBF produced by electrospinning followed by biomimetic mineralization had combined electrospun fibers with nHA in it. This scaffold has good biocompatibility and osteoinductive ability as a result of the characteristics of nHA, so could be innovatively applied to periodontal tissue engineering as a potential scaffold. PMID:25206304

Wu, Xiaonan; Miao, Leiying; Yao, Yingfang; Wu, Wenlei; Liu, Yu; Chen, Xiaofeng; Sun, Weibin

2014-01-01

370

Characterization and corrosion behavior of hydroxyapatite coatings on Ti6Al4V fabricated by electrophoretic deposition  

NASA Astrophysics Data System (ADS)

In order to increase the bone bioactivity of the metallic implants, hydroxyapatite (HA) is often coated on their surface so that a real bond with the surrounding bone tissue can be formed. Plasma spraying of HA coatings is currently the only commercial process in use but long-term stability of plasma sprayed coatings could be a problem because of their high degree of porosities, poor bond strength, presence of a small amount of amorphous phase with non-stoichiometric composition, and non-uniformity. In the present study, cathodic electrophoretic deposition (EPD) has been attempted for depositing HA coatings on Ti6Al4V followed by vacuum sintering at 800 °C. Submicron HA powders with different morphologies including spherical, needle-shaped and flake-shaped were used in the EDP process to produce dense coatings. Moreover, carbon nanotubes (CNTs) were also used to reinforce the HA coating for enhancing its hardness. The surface morphology, compositions and microstructure of the HA coated Ti6Al4V were investigated by electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffractometry, respectively. Electrochemical corrosion behavior of the HA coatings in Hanks' solution at 37 °C was investigated by means of open-circuit potential measurement and cyclic potentiodynamic polarization tests. Surface hardness, adhesion strength and bone bioactivity of the coatings were also studied. All HA coated specimens had a thickness of about 10 ?m and free of cracks, with corrosion resistance higher than that of the substrate and adhesion strength higher than that of plasma sprayed coating. The enhanced properties could be attributed to the use of submicron-sized HA particles in the low-temperature EDP process. Among the three types of HA powder, spherical powder yielded the densest coating whereas the flake-shaped powder yielded the most porous coatings. Compared with monolithic HA coating, the CNT-reinforced HA coating markedly increased the coating hardness without compromising the corrosion resistance or adhesion strength.

Kwok, C. T.; Wong, P. K.; Cheng, F. T.; Man, H. C.

2009-04-01

371

In vitro anti-bacterial and biological properties of magnetron co-sputtered silver-containing hydroxyapatite coating.  

PubMed

Bacterial infection after implant placement is a significant rising complication. In order to reduce the incidence of implant-associated infections, several biomaterial surface treatments have been proposed. In this study, the effect of in vitro antibacterial activity and in vitro cytotoxicity of co-sputtered silver (Ag)-containing hydroxyapatite (HA) coating was evaluated. Deposition was achieved by a concurrent supply of 10 W to the Ag target and 300 W to the HA target. Heat treatment at 400 degrees C for 4 h was performed after 3 h deposition. X-ray diffraction, contact angles measurements, and surface roughness were used to characterize the coating surfaces. The RP12 strain of Staphylococcus epidermidis (ATCC 35984) and the Cowan I strain of Staphylococcus aureus were used to evaluate the antibacterial activity of the Ag-HA coatings, whereas human embryonic palatal mesenchyme cells, an osteoblast precursor cell line, were used to evaluate the in vitro cytotoxicity of the coatings. X-ray diffraction analysis performed in this study indicated peaks corresponding to Ag and HA on the co-sputtered Ag-HA surfaces. The contact angles for HA and Ag-HA surfaces were observed to be significantly lower when compared to Ti surfaces, whereas no significant difference in surface roughness was observed for all groups. In vitro bacterial adhesion study indicated a significantly reduced number of S. epidermidis and S. aureus on Ag-HA surface when compared to titanium (Ti) and HA surfaces. In addition, no significant difference in the in vitro cytotoxicty was observed between HA and Ag-HA surfaces. Overall, it was concluded that the creation of a multifunctional surface can be achieved by co-sputtering the osteoconductive HA with antibacterial Ag. PMID:16872671

Chen, W; Liu, Y; Courtney, H S; Bettenga, M; Agrawal, C M; Bumgardner, J D; Ong, J L

2006-11-01

372

Modified Open-door Laminoplasty Using Hydroxyapatite Spacers and Miniplates  

PubMed Central

Objective Cervical laminoplasty has been widely accepted as one of the major treatments for cervical myelopathy and various modifications and supplementary procedures have been devised to achieve both proper decompression and stability of the cervical spine. We present the retrospectively analyzed results of a modified unilateral open-door laminoplasty using hydroxyapatite (HA) spacers and malleable titanium miniplates. Methods From June 2008 to May 2012, among patients diagnosed with cervical spondylotic myelopathy and ossification of posterior longitudinal ligament, the patients who received laminoplasty were reviewed. Clinical outcome was assessed using Frankel grade and Japanese Orthopaedic Association score. The radiologic parameters were obtained from plain films, 3-dimensional computed tomography and magnetic resonance images. Results A total of 125 cervical laminae were operated in 38 patients. 11 patients received 4-level laminoplasty and 27 patients received 3-level laminoplasty. Postoperatively, the mean Frankel grade and JOA score were significantly improved from 3.97 to 4.55 and from 12.76 to 14.63, respectively (p<0.001). Radiologically, cervical curvature was worsened from 19.09 to 15.60 (p=0.025). The percentage of range of motion preservation was 73.32±22.39%. The axial dimension of the operated spinal canal was increased from 1.75 to 2.70 cm2 (p<0.001). Conclusion In the presenting study, unilateral open-door laminoplasty using HA spacers and miniplates appears to be a safe, rapid and easy procedure to obtain an immediate and rigid stabilization of the posterior elements of the cervical spine. This modified laminoplasty method showed effective expansion of the spinal canal and favorable clinical outcomes. PMID:25346767

Jin, Sung-Won; Kim, Bum-Joon; Choi, Jong-Il; Ha, Sung-Kon; Kim, Sang-Dae; Lim, Dong-Jun

2014-01-01

373

Morphology effect of bioglass-reinforced hydroxyapatite (Bonelike(®) ) on osteoregeneration.  

PubMed

In the last decades, the well-known disadvantages of autografts and allografts have driven to the development of synthetic bone grafts for bone regeneration. Bonelike(®) , a glass-reinforced hydroxyapatite (HA) composite was developed and registered for bone grafting. This biomaterial is composed by a modified HA matrix, with ?- and ?-tricalcium phosphate secondary phases. Aiming to improve the biological characteristics of Bonelike(®) , new spherical pelleted granules, of different shape and size, were developed with controlled micro and macrostructure. In the present study, it was compared the physicochemical properties and in vivo performance of different Bonelike(®) granule presentations-Bonelike(®) polygonal (500-1000 µm size) and Bonelike spherical (250-500 µm; 500-1000 µm size). For the in vivo study, Bonelike(®) was implanted on sheep femurs, with various implantation times (30 days, 60 days, 120 days, and 180 days). X-ray diffraction analysis revealed that the phase composition of different granules presentations was similar. Bonelike(®) spherical 500-1000 µm was the most porous material (global porosity and intraporosity) and Bonelike(®) polygonal 500-1000 µm the less porous. Considering the in vivo study, both polygonal and spherical granules presented osteoconductive proprieties. The spherical granules showed several advantages, including easier medical application through syringe and improved osteointegration, osteoconduction, and degradation, by the presence of larger pores, controlled micro- and macrosctructure and suitable particle format that adapts to bone growth. Bonelike(®) spherical 500-1000 µm showed improved new bone invasion throughout the material's structure and Bonelike(®) spherical 250-500 µm appeared to induce faster bone regeneration, presenting less unfilled areas and less lacunae in the histological analysis. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 103B: 292-304, 2015. PMID:24819340

Atayde, L M; Cortez, P P; Afonso, A; Santos, M; Maurício, A C; Santos, J D

2015-02-01

374

art Phones ha versity of Wa  

E-print Network

ormation art Phone art Phones ha versity of Wa ness emails, smart phone lability of insti ou use a Univ ce of the Chie ngs to help pr Access - phone. Do Automat (for exam entered in Tamper W code or P pass code the event password phone int SIM card smart pho list represen protect the in ngs may appl additional info

Queitsch, Christine

375

Rolling friction of adhesive microspheres  

NASA Astrophysics Data System (ADS)

The rolling friction of adhesive microspheres is an important quantity as it determines the strength and stability of larger aggregates. Current models predict rolling forces that are 1 to 2 orders of magnitude smaller than observed experimentally. Starting from the well-known Johnson-Kendall-Roberts (JKR) contact description, we derive an analytical theory for the rolling friction based on the concept of adhesion hysteresis, e.g. a difference in apparent surface energies for opening/closing cracks. We show how adhesion hysteresis causes the pressure distribution within the contact to become asymmetrical, leading to an opposing torque. Analytical expressions are derived relating the size of the hysteresis, the rolling torque, and the rolling displacement, ?. We confirm the existence of a critical rolling displacement for the onset of rolling, the size of which is set by the amount of adhesion hysteresis and the size of the contact area. We demonstrate how the developed theory is able to explain the large rolling forces and particle-size dependence observed experimentally. Good agreement with experimental results is achieved for adhesion hysteresis values of (??/?) ? 3 for polystyrene, and (??/?) ? 0.5 for silicates, at crack propagation rates of 0.1 µm s-1 and 1-10 µm s-1, respectively.

Krijt, S.; Dominik, C.; Tielens, A. G. G. M.

2014-04-01

376

Improving photoprotection: 4-methylbenzylidene camphor microspheres.  

PubMed

Abstract We propose a new approach for photoprotection. 4-Methylbenzylidene camphor (4-MBC), one of the most widely used UV filters, was encapsulated in microspheres, with a view to overcoming problems (percutaneous absorption, photodegradation and lack of lasting effect) arising with organic sunscreens, and to achieve safe photoprotection. We focused on this filter in the light of the Cosmetics Europe opinion concerning its possible effects on the thyroid gland. Microspheres were prepared by emulsification-solvent evaporation, using different amounts of 4-MBC and characterized for morphology, encapsulation efficiency and particle size. The particles were then mixed in O/W emulsions. The in vitro sun protection factors, in vitro release and photostability were investigated and compared with emulsions containing the free sunscreen. The new microspheres offer good morphology and loading (up to 40%), and the same photoprotection as the free filter while at the same time protecting it from photodegradation. The systems also give a slower release from the emulsions. PMID:24854342

Centini, Marisanna; Miraglia, Giovanna; Quaranta, Valeria; Buonocore, Anna; Anselmi, Cecilia

2014-05-22

377

Nanocrystalline spherical hydroxyapatite granules for bone repair: in vitro evaluation with osteoblast-like cells and osteoclasts.  

PubMed

Conventionally sintered hydroxyapatite-based materials for bone repair show poor resorbability due to the loss of nanocrystallinity. The present study describes a method to establish nanocrystalline hydroxyapatite granules. The material was prepared by ionotropic gelation of an alginate sol containing hydroxyapatite (HA) powder. Subsequent thermal elimination of alginate at 650 °C yielded non-sintered, but unexpectedly stable hydroxyapatite granules. By adding stearic acid as an organic filler to the alginate/HA suspension, the granules exhibited macropores after thermal treatment. A third type of material was achieved by additional coating of the granules with silica particles. Microstructure and specific surface area of the different materials were characterized in comparison to the already established granular calcium phosphate material Cerasorb M(®). Cytocompatibility and potential for bone regeneration of the materials was evaluated by in vitro examinations with osteosarcoma cells and osteoclasts. Osteoblast-like SaOS-2 cells proliferated on all examined materials and showed the typical increase of alkaline phosphatase (ALP) activity during cultivation. Expression of bone-related genes coding for ALP, osteonectin, osteopontin, osteocalcin and bone sialoprotein II on the materials was proven by RT-PCR. Human monocytes were seeded onto the different granules and osteoclastogenesis was examined by activity measurement of tartrate-specific acid phosphatase (TRAP). Gene expression analysis after 23 days of cultivation revealed an increased expression of osteoclast-related genes TRAP, vitronectin receptor and cathepsin K, which was on the same level for all examined materials. These results indicate, that the nanocrystalline granular materials are of clinical interest, especially for bone regeneration. PMID:23625348

Bernhardt, A; Dittrich, R; Lode, A; Despang, F; Gelinsky, M

2013-07-01

378

Preparation of hydroxyapatite via microemulsion route.  

PubMed

Hydroxyapatite (HAp) was prepared using a microemulsion route in combination with the pH-shock wave method. The samples as received consisted of amorphous aggregated particles, which had remarkable mesoporosity with a narrow pore size distribution. After being heated at 650 degrees C, the A-type carbonate hydroxyapatite was crystallized at 635 degrees C in particles of similar size (40--120 nm) with no internal porosity. At a higher temperature (900 degrees C) a sintering process took place, resulting in network of a larger particles, consisting of HAp and beta-tricalcium phosphate (beta-TCP). The crystallization of HAp occurs at 635 degrees C with an activation energy of 62.7--72.2 kcalmol(-1). PMID:16256504

Koumoulidis, George C; Katsoulidis, Alexandros P; Ladavos, Athanasios K; Pomonis, Phillippos J; Trapalis, Christos C; Sdoukos, Antonios T; Vaimakis, Tiberius C

2003-03-15

379

Reactive hydroxyapatite fillers for pectin biocomposites.  

PubMed

In this work, a novel injectable biocomposite hydrogel is produced by internal gelation, using pectin as organic matrix and hydroxyapatite either as crosslinking agent and inorganic reinforcement. Tunable gelling kinetics and rheological properties are obtained varying the hydrogels' composition, with the final aim of developing systems for cell immobilization. The reversibility by dissolution of pectin-hydroxyapatite hydrogels is achieved with saline solutions, to possibly accelerate the release of the cells or active agents immobilized. Texture analysis confirms the possibility of extruding the biocomposites from needles with diameters from 20G to 30G, indicating that they can be implanted with minimally-invasive approaches, minimizing the pain during injection and the side effects of the open surgery. L929 fibroblasts entrapped in the hydrogels survive to the immobilization procedure and exhibit high cell viability. On the overall, these systems result to be suitable supports for the immobilization of cells for tissue regeneration applications. PMID:25491814

Munarin, Fabiola; Petrini, Paola; Barcellona, Giulia; Roversi, Tommaso; Piazza, Laura; Visai, Livia; Tanzi, Maria Cristina

2014-12-01

380

Thermoluminescent characteristics of synthetic hydroxyapatite (SHAp).  

PubMed

This paper presents the experimental results of the thermoluminescent (TL) characteristics of synthetic hydroxyapatite (SHAp) obtained by the sol-gel method. For preparation of the SHAp powders, phosphorus pentoxide (P2O5) and calcium nitrate tetrahydrated (Ca(NO3)2-4H2O) were used. The powders obtained were submitted at different temperatures. The structural and morphological characterization were carried out using X-ray diffraction (XRD) and scanning electron microscopy techniques. TL glow curve exhibited two peaks centered at around 200 °C and 300 °C. TL response of SHAp as a function of gamma absorbed dose was linear over a wide dose range. Fading of the storage information in the samples irradiated was also studied. The experimental results show that the synthetic hydroxyapatite obtained by the sol-gel method may have used in gamma radiation dosimetry applications. PMID:23707740

Alvarez, R; Rivera, T; Guzman, J; Piña-Barba, M C; Azorin, J

2014-01-01

381

Microstrain in hydroxyapatite carbon nanotube composites.  

PubMed

Synchrotron radiation diffraction data were collected from hydroxyapatite-carbon nanotube bioceramic composites to determine the crystallite size and to measure changes in non-uniform strain. Estimates of crystallite size and strain were determined by line-profile fitting of discrete peaks and these were compared with a Rietveld whole-pattern analysis. Overall the two analysis methods produced very similar numbers. In the commercial hydroxyapatite material, one reflection in particular, (0 2 3), has higher crystallite size and lower strain values in comparison with laboratory-synthesized material. This could indicate preferential crystal growth in the [0 2 3] direction in the commercial material. From the measured strains in the pure material and the composite, there was a degree of bonding between the matrix and strengthening fibres. However, increasing the amount of carbon nanotubes in the composite has increased the strain in the material, which is undesirable for biomedical implant applications. PMID:18097082

Kealley, Catherine; Elcombe, Margaret; van Riessen, Arie

2008-01-01

382

Polymeric Microspheres as Protein Transduction Reagents*  

PubMed Central

Discovering the function of an unknown protein, particularly one with neither structural nor functional correlates, is a daunting task. Interaction analyses determine binding partners, whereas DNA transfection, either transient or stable, leads to intracellular expression, though not necessarily at physiologically relevant levels. In theory, direct intracellular protein delivery (protein transduction) provides a conceptually simpler alternative, but in practice the approach is problematic. Domains such as HIV TAT protein are valuable, but their effectiveness is protein specific. Similarly, the delivery of intact proteins via endocytic pathways (e.g. using liposomes) is problematic for functional analysis because of the potential for protein degradation in the endosomes/lysosomes. Consequently, recent reports that microspheres can deliver bio-cargoes into cells via a non-endocytic, energy-independent pathway offer an exciting and promising alternative for in vitro delivery of functional protein. In order for such promise to be fully exploited, microspheres are required that (i) are stably linked to proteins, (ii) can deliver those proteins with good efficiency, (iii) release functional protein once inside the cells, and (iv) permit concomitant tracking. Herein, we report the application of microspheres to successfully address all of these criteria simultaneously, for the first time. After cellular uptake, protein release was autocatalyzed by the reducing cytoplasmic environment. Outside of cells, the covalent microsphere–protein linkage was stable for ?90 h at 37 °C. Using conservative methods of estimation, 74.3% ± 5.6% of cells were shown to take up these microspheres after 24 h of incubation, with the whole process of delivery and intracellular protein release occurring within 36 h. Intended for in vitro functional protein research, this approach will enable study of the consequences of protein delivery at physiologically relevant levels, without recourse to nucleic acids, and offers a useful alternative to commercial protein transfection reagents such as Chariot™. We also provide clear immunostaining evidence to resolve residual controversy surrounding FACS-based assessment of microsphere uptake. PMID:24692642

Nagel, David; Behrendt, Jonathan M.; Chimonides, Gwen F.; Torr, Elizabeth E.; Devitt, Andrew; Sutherland, Andrew J.; Hine, Anna V.

2014-01-01

383

Effect of different hydroxyapatite incorporation methods on the structural and biological properties of porous collagen scaffolds for bone repair.  

PubMed

Scaffolds which aim to provide an optimised environment to regenerate bone tissue require a balance between mechanical properties and architecture known to be conducive to enable tissue regeneration, such as a high porosity and a suitable pore size. Using freeze-dried collagen-based scaffolds as an analogue of native ECM, we sought to improve the mechanical properties by incorporating hydroxyapatite (HA) in different ways while maintaining a pore architecture sufficient to allow cell infiltration, vascularisation and effective bone regeneration. Specifically we sought to elucidate the effect of different hydroxyapatite incorporation methods on the mechanical, morphological, and cellular response of the resultant collagen-HA scaffolds. The results demonstrated that incorporating either micron-sized (CHA scaffolds) or nano-sized HA particles (CnHA scaffolds) prior to freeze-drying resulted in moderate increases in stiffness (2.2-fold and 6.2-fold, respectively, vs. collagen-glycosaminoglycan scaffolds, P < 0.05, a scaffold known to support osteogenesis), while enabling good cell attachment, and moderate mesenchymal stem cell (MSC)-mediated calcium production after 28 days' culture (2.1-fold, P < 0.05, and 1.3-fold, respectively, vs. CG scaffolds). However, coating of collagen scaffolds with a hydroxyapatite precipitate after freeze-drying (CpHA scaffolds) has been shown to be a highly effective method to increase the compressive modulus (26-fold vs. CG controls, P < 0.001) of scaffolds while maintaining a high porosity (~ 98%). The coating of the ligand-dense collagen structure results in a lower cell attachment level (P < 0.05), although it supported greater cell-mediated calcium production (P < 0.0001) compared with other scaffold variants after 28 days' culture. The comparatively good mechanical properties of these high porosity scaffolds is obtained partially through highly crosslinking the scaffolds with both a physical (DHT) and chemical (EDAC) crosslinking treatment. Control of scaffold microstructure was examined via alterations in freezing temperature. It was found that the addition of HA prior to freeze-drying generally reduced the pore size and so the CpHA scaffold fabrication method offered increased control over the resulting scaffolds microstructure. These findings will help guide future design considerations for composite biomaterials and demonstrate that the method of HA incorporation can have profound effects on the resulting scaffold structural and biological response. PMID:25409684

Ryan, Alan J; Gleeson, John P; Matsiko, Amos; Thompson, Emmet M; O'Brien, Fergal J

2014-11-20

384

[Intravitreal drug delivery by microspheres of biodegradable polymers].  

PubMed

We evaluated the efficacy of microspheres of biodegradable polymers as a slow releasing drug delivery system in the vitreous body. Microspheres containing 5-FU were prepared with polymers of poly-(lactic acid) or copolymers of glycolic acid and lactic acid. The release of the drug was studied in vitro. Poly-(lactic acid) microspheres released 5-FU for 7 days. The intravitreal kinetics of the microspheres was studied in rabbits in vivo. The microspheres disappeared from the vitreous cavity of normal eyes by 48 +/- 5 days after injection. Disappearance was accelerated from the vitreous cavity of vitrectomized rabbits (14 +/- 2 days, p less than 10(-6)). No abnormality was found on electroretinographic or histological examinations after microspheres injection. These results suggested that microspheres of biodegradable polymers could be useful as a potential drug delivery system for sustained drug release in the vitreous body. PMID:2220493

Moritera, T; Ogura, Y; Honda, Y; Wada, R; Hyon, S H; Ikada, Y

1990-05-01

385

Formulation and evaluation of nasal mucoadhesive microspheres of sumatriptan succinate.  

PubMed

The purpose of present research work was to develop mucoadhesive microspheres for nasal delivery with the aim to avoid hepatic first-pass metabolism, improve therapeutic efficacy and enhance residence time. For the treatment of migraine, hydroxypropyl methylcellulose (HPMC) K4M and K15M based microspheres containing sumatriptan succinate (SS) were prepared by spray-drying technique. The microspheres were evaluated with respect to the yield, particle size, incorporation efficiency, swelling property, in vitro mucoadhesion, in vitro drug release, histological study and stability. Microspheres were characterized by differential scanning calorimetry, scanning electron microscopy and X-ray diffraction study. It was found that the particle size, swelling ability and incorporation efficiency of microspheres increases with increasing drug-to-polymer ratio. HPMC-based microspheres show adequate mucoadhesion and do not have any destructive effect on nasal mucosa. On the basis of these results, SS microspheres based on HPMC may be considered as a promising nasal delivery system. PMID:19888880

Jain, Snehal A; Chauk, Dheeraj S; Mahajan, Hitendra S; Tekade, Avinash R; Gattani, Surendra G

2009-12-01

386

Expandable microspheres for the handling of liquids.  

PubMed

Two novel concepts for controlled handling of liquids in microfluidic systems are presented: a one-shot micropump and a normally open one-shot valve based on thermo-expanding Expancel microspheres. Expancel microspheres are small spherical plastic particles that, when heated, increase their volume considerably. We show that liquid volumes in the nanoliter range can be actuated against a counter pressure of at least 100 kPa and fluid flow can be inhibited in a microchannel against pressures of at least 100 kPa. PMID:15100844

Griss, Patrick; Andersson, Helene; Stemme, Göran

2002-05-01

387

Cell specific, variable density, polymer microspheres  

NASA Technical Reports Server (NTRS)

Biocompatible polymeric microspheres having an average diameter below about 3 microns and having density at least 15% greater or lesser than organic cells and having covalent binding sites are provided in accordance with this invention. The microspheres are obtained by copolymerizing a hydroxy or amine substituted acrylic monomer such as hydroxyethylmethacrylate with a light or dense comonomer such as a fluoromonomer. A lectin or antibody is bound to the hydroxy or amine site of the bead to provide cell specificity. When added to a cell suspension the marked bead will specifically label the cell membrane by binding to specific receptor sites thereon. The labelled membrane can then be separated by density gradient centrifugation.

Yen, Shiao-Ping S. (Inventor); Rembaum, Alan (Inventor); Molday, Robert S. (Inventor)

1977-01-01

388

Electrophoretic cell separation by means of microspheres  

NASA Technical Reports Server (NTRS)

The electrophoretic mobility of fixed human erythrocytes immunologically labeled with poly(vinylpyridine) or poly(glutaraldehyde) microspheres was reduced by approximately 40%. This observation was utilized in preparative scale electrophoretic separations of fixed human and turkey erythrocytes, the mobilities of which under normal physiological conditions do not differ sufficiently to allow their separation by continuous flow electrophoresis. We suggest that resolution in the electrophoretic separation of cell subpopulations, currently limited by finite and often overlapping mobility distributions, may be significantly enhanced by immunospecific labeling of target populations using microspheres.

Smolka, A. J. K.; Nerren, B. H.; Margel, S.; Rembaum, A.

1979-01-01

389

Quantum Magnetomechanics with Levitating Superconducting Microspheres  

E-print Network

We show that by magnetically trapping a superconducting microsphere close to a quantum circuit, it is experimentally feasible to perform ground-state cooling and to prepare quantum superpositions of the center-of-mass motion of the microsphere. Due to the absence of clamping losses and time dependent electromagnetic fields, the mechanical motion of micrometer-sized metallic spheres in the Meissner state is predicted to be very well isolated from the environment. Hence, we propose to combine the technology of magnetic microtraps and superconducting qubits to bring relatively large objects to the quantum regime.

O. Romero-Isart; L. Clemente; C. Navau; A. Sanchez; J. I. Cirac

2011-12-23

390

Quantum Magnetomechanics with Levitating Superconducting Microspheres  

E-print Network

We show that by magnetically trapping a superconducting microsphere close to a quantum circuit, it is experimentally feasible to perform ground state cooling and to prepare quantum superpositions of the center-of-mass motion of the microsphere. Due to the absence of clamping losses and time dependent electromagnetic fields, the mechanical motion of micrometer-sized metallic spheres in the Meissner state is predicted to be extremely well isolated from the environment. Hence, we propose to combine the technology of magnetic mictrotraps and superconducting qubits to bring relatively large objects to the quantum regime.

Romero-Isart, O; Navau, C; Sanchez, A; Cirac, J I

2011-01-01

391

Microstructure and mechanical properties of an Mg-3Zn- o.5Zr-5HA nanocomposite processed by ECAE  

NASA Astrophysics Data System (ADS)

Mg matrix composites reinforced by natural bone constituent hydroxyapatite (HA) particles have shown promising in-vitro corrosion resistance but are inconsistent in both electrochemical and mechanical performances because of severe particle segregations. The present work was carried out to investigate the feasibility of a novel technology that combines high shear solidification and equal channel angular extrusion (ECAE) for fabricating Mg-HA nanocomposites. Experiments showed that the high shear solidification resulted in a fine and uniform grain structure with a globally uniform HA nanoparticles in fine clusters and the ECAE processing of the as-cast composites resulted in further grain refinement and more importantly the breakdown of nanoparticle aggregates, leading to the formation of a dispersion of true nanoparticles in the Mg alloy matrix with improved mechanical properties. This paper describes mainly the microstructural features and mechanical performance of Mg-3Zn-0.5Zr-xHA (x = 1, 3, 5, 10) nanocomposites, in which the HA was in spherical shape with an average diameter of ~20nm

Li, J.; Huang, Y.

2014-08-01

392

Functional analysis of bone sialoprotein: identification of the hydroxyapatite-nucleating and cell-binding domains by recombinant peptide expression and site-directed mutagenesis  

Microsoft Academic Search

Mammalian bone sialoprotein (BSP) is a mineralized tissue-specific protein containing an RGD (arginine-glycine-aspartic acid) cell-attachment sequence and two distinct glutamic acid (glu)-rich regions, with each containing one contiguous glu sequence. These regions have been proposed to contribute to the attachment of bone cells to the extracellular matrix and to the nucleation of hydroxyapatite (HA), respectively. To further delineate the domains

N. L Harris; K. R Rattray; C. E Tye; T. M Underhill; M. J Somerman; J. A D’Errico; A. F Chambers; G. K Hunter; H. A Goldberg

2000-01-01

393

Mechanical properties of TiO2-hydroxyapatite nanostructured coatings on Ti-6Al-4V substrates by APS method  

NASA Astrophysics Data System (ADS)

TiO2-hydroxyapatite (HA) nanostructured coatings were produced by atmospheric plasma spray method. The effects of starting powder composition and grain size on their mechanical properties were investigated. The microstructure and morphology were characterized by X-ray diffraction and scanning electron microscopy (SEM). It is found that the coating with 10% HA has the best mechanical properties. Based on Rietveld refinement method, the mean grain size of the as-received powder (212 nm) extensively decreases to 66.4 nm after 20 h of high-energy ball milling. In spite of grain growth, the deposited coatings maintain their nanostructures with the mean grain size of 112 nm. SEM images show that there is a lower porosity in the coating with a higher HA content. Optical microscopy images show that uniform thickness is obtained for all the coatings.

Zakeri, Mohammad; Hasani, Elmira; Tamizifar, Morteza

2013-04-01

394

Induction of osteoconductivity by BMP-2 gene modification of mesenchymal stem cells combined with plasma-sprayed hydroxyapatite coating  

NASA Astrophysics Data System (ADS)

Success in bone implant depends greatly on the composition and surface features of the implant. The surface-modification measures not only favor the implant's osteoconductivity, but also promote both bone anchoring and biomechanical stability. This paper reports an approach to combine a hydroxyapatite (HA) coated substrate with a cellular vehicle for the delivery of bone morphogenetic protein-2 (BMP-2) synergistically enhancing the osteoconductivity of implant surfaces. We examined the attachment, growth and osteoinductive activity of transfected BMP-producing bone marrow mesenchymal stem cells (BMSCs) on a plasma-sprayed HA coated substrate. It was found that the HA coated substrate could allow the attachment and growth of BMP-2 gene modified BMSCs, and this combined application synergistically enhanced osteconductivity of the substrate surface. This synergistic method may be of osseointegration value in orthopedic and dental implant surgery.

Wu, Jiang; Guo, Ying-qiang; Yin, Guang-fu; Chen, Huai-qing; Kang, Yunqing

2008-11-01

395

The effect of nanobioceramic reinforcement on mechanical and biological properties of Co-base alloy/hydroxyapatite nanocomposite.  

PubMed

The goal of the present research was to fabricate, characterize, and evaluate mechanical and biological properties of Co-base alloy composites with different amounts of hydroxyapatite (HA) nanopowder reinforcement. The powder of Co-Cr-Mo alloy was mixed with different amounts of HA by ball milling and it was then cold pressed and sintered. X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques were used. Microhardness measurement and compressive tests were also carried out. Bioactivity behavior was evaluated in simulated body fluid (SBF). A significant decrease in modulus elasticity and an increase in microhardness of the sintered composites were observed. Apatite formation on the surface of the composites showed that it could successfully convert bioinert Co-Cr-Mo alloy to bioactive type by adding 10, 15, and 20wt.% HA which have lower modulus elasticity and higher microhardness. PMID:25579959

Bahrami, M; Fathi, M H; Ahmadian, M

2015-03-01

396

Mechanical, rheological, and bioactivity properties of ultra high-molecular-weight polyethylene bioactive composites containing polyethylene glycol and hydroxyapatite.  

PubMed

Ultrahigh-molecular-weight polyethylene/high-density polyethylene (UHMWPE/HDPE) blends prepared using polyethylene glycol PEG as the processing aid and hydroxyapatite (HA) as the reinforcing filler were found to be highly processable using conventional melt blending technique. It was demonstrated that PEG reduced the melt viscosity of UHMWPE/HDPE blend significantly, thus improving the extrudability. The mechanical and bioactive properties were improved with incorporation of HA. Inclusion of HA from 10 to 50?phr resulted in a progressive increase in flexural strength and modulus of the composites. The strength increment is due to the improvement on surface contact between the irregular shape of HA and polymer matrix by formation of mechanical interlock. The HA particles were homogenously distributed even at higher percentage showed improvement in wetting ability between the polymer matrix and HA. The inclusion of HA enhanced the bioactivity properties of the composite by the formation of calcium phosphate (Ca-P) precipitates on the composite surface as proven from SEM and XRD analysis. PMID:22666129

Ahmad, Mazatusziha; Uzir Wahit, Mat; Abdul Kadir, Mohammed Rafiq; Mohd Dahlan, Khairul Zaman

2012-01-01

397

Photocatalytic hydroxyapatite/titanium dioxide multilayer thin film deposited onto glass using an rf magnetron sputtering technique  

NASA Astrophysics Data System (ADS)

Hydroxyapatite (HA)/titanium dioxide (TiO 2) thin film was deposited on glass using a radio frequency magnetron sputtering. X-ray diffraction (XRD), Fourier-transform infrared spectrometry, ultraviolet-visible spectroscopy and measurement of its photocatalytic activity by the decomposition of formaldehyde gas and the bacterial survival test of Escherichia coli ( E. coli) cells were applied to characterize the film. After heat treatment (at 500 °C), XRD analysis of the HA/TiO 2 film showed a crystalline TiO 2 crystal structure with anatase phase. The transmittance of the HA/TiO 2 film decreased after the heat treatment, however, the average transmittance remained at 87% in the visible light range. In the decomposition of formaldehyde gas, the HA/TiO 2 film showed a higher decomposition rate than either the TiO 2 or the HA film alone. However, in the bacterial survival test, survival of cells on the HA/TiO 2 film was higher than that on the TiO 2 film, which indicates the HA/TiO 2 film has a lower bactericidal effect than the TiO 2 film alone.

Ozeki, K.; Janurudin, Juliana M.; Aoki, H.; Fukui, Y.

2007-01-01

398

Mechanical, Rheological, and Bioactivity Properties of Ultra High-Molecular-Weight Polyethylene Bioactive Composites Containing Polyethylene Glycol and Hydroxyapatite  

PubMed Central

Ultrahigh-molecular-weight polyethylene/high-density polyethylene (UHMWPE/HDPE) blends prepared using polyethylene glycol PEG as the processing aid and hydroxyapatite (HA) as the reinforcing filler were found to be highly processable using conventional melt blending technique. It was demonstrated that PEG reduced the melt viscosity of UHMWPE/HDPE blend significantly, thus improving the extrudability. The mechanical and bioactive properties were improved with incorporation of HA. Inclusion of HA from 10 to 50?phr resulted in a progressive increase in flexural strength and modulus of the composites. The strength increment is due to the improvement on surface contact between the irregular shape of HA and polymer matrix by formation of mechanical interlock. The HA particles were homogenously distributed even at higher percentage showed improvement in wetting ability between the polymer matrix and HA. The inclusion of HA enhanced the bioactivity properties of the composite by the formation of calcium phosphate (Ca-P) precipitates on the composite surface as proven from SEM and XRD analysis. PMID:22666129

Ahmad, Mazatusziha; Wahit, Mat Uzir; Abdul Kadir, Mohammed Rafiq; Mohd Dahlan, Khairul Zaman

2012-01-01

399

Preparation and characterization of nano-hydroxyapatite/chitosan cross-linking composite membrane intended for tissue engineering.  

PubMed

In this paper, a series of nano-hydroxyapatite(n-HA)/chitosan cross-linking composite membranes (n-HA; 0, 5, 10, 15, 20 and 30 wt%) were successfully developed by a simple casting/solvent evaporation method. n-HA with size about 20 nm in vertical diameter and about 100 nm in horizontal diameter was successfully synthesized by a hydro-thermal precipitation method, and then dispersed into chitosan/genipin solution with the aid of continuous ultrasound to develop n-HA/chitosan cross-linking composite membranes. The detailed characterizations including Fourier transform infrared spectroscopy (FTIR), X-ray diffractometer (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), water adsorption and tensile test were performed. With the analysis of FTIR spectra and TGA spectra, it suggested that there was existence of possible interactions between polymer and n-HA. Meanwhile, the n-HA content was greatly effected on the morphology as well as the tensile property of composite membrane. In vitro cytotoxicity test suggested that the developed n-HA/chitosan cross-linking composite membrane was non-cytotoxicity against L929 cells after 24h's incubation might be suitable for further in vivo application. PMID:21983025

Li, XingYi; Nan, KaiHui; Shi, Shuai; Chen, Hao

2012-01-01

400

Hydroxyapatite cement as a filler for cavitary mandibular defects  

Microsoft Academic Search

Hydroxyapatite cement, which has several advantages when compared with other biomaterials, was used to reconstruct a cavity in the mandible resulting from extraction of two impacted teeth. The patient was followed up for 2 years and plain radiographs revealed no loss or resorption of the implant material. With the positive results of this clinical experience, hydroxyapatite cement now seems to

Reha Yavuzer; Ian T. Jackson

2001-01-01

401

Electrophoretic deposition of composite hydroxyapatite-chitosan coatings  

SciTech Connect

Cathodic electrophoretic deposition has been utilized for the fabrication of composite hydroxyapatite-chitosan coatings on 316L stainless steel substrates. The addition of chitosan to the hydroxyapatite suspensions promoted the electrophoretic deposition of the hydroxyapatite nanoparticles and resulted in the formation of composite coatings. The obtained coatings were investigated by X-ray diffraction, thermogravimetric and differential thermal analysis, scanning and transmission electron microscopy, potentiodynamic polarization measurements, and electrochemical impedance spectroscopy. It was shown that the deposit composition can be changed by a variation of the chitosan or hydroxyapatite concentration in the solutions. Experimental conditions were developed for the fabrication of hydroxyapatite-chitosan nanocomposites containing 40.9-89.8 wt.% hydroxyapatite. The method enabled the formation of adherent and uniform coatings of thicknesses up to 60 {mu}m. X-ray studies revealed that the preferred orientation of the hydroxyapatite nanoparticles in the chitosan matrix increases with decreasing hydroxyapatite content in the composite coatings. The obtained coatings provided the corrosion protection for the 316L stainless steel substrates00.

Pang Xin [Department of Materials Science and Engineering, McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4L7 (Canada); Zhitomirsky, Igor [Department of Materials Science and Engineering, McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4L7 (Canada)]. E-mail: zhitom@mcmaster.ca

2007-04-15

402

Lanthanum-containing hydroxyapatite coating on ultrafine-grained titanium by micro-arc oxidation: a promising strategy to enhance overall performance of titanium.  

PubMed

Titanium is widely used in biomedical materials, particularly in dental implants, because of its excellent biocompatibility and mechanical characteristics. However, titanium implant failures still remain in some cases, varying with implantation sites and patients. Improving its overall performance is a major focus of dental implant research. Equal-channel angular pressing (ECAP) can result in ultrafine-grained titanium with superior mechanical properties and better biocompatibility, which significantly benefits dental implants, and without any harmful alloying elements. Lanthanum (La) can inhibit the acidogenicity of dental plaque and La-containing hydroxyapatite (La-HA) possesses a series of attractive properties, in contrast to La-free HA. Micro-arc oxidation (MAO) is a promising technology that can produce porous and firmly adherent hydroxyapatite (HA) coatings on titanium substrates. Therefore, we hypothesize that porous La-containing hydroxyapatite coatings with different La content (0.89%, 1.3% and 1.79%) can be prepared on ultrafine-grained (~200-400 nm) titanium by ECAP and MAO in electrolytic solution containing 0.2 mol/L calcium acetate, 0.02 mol/L beta-glycerol phosphate disodium salt pentahydrate (beta-GP), and lanthanum nitrate with different concentrations to further improve the overall performance of titanium, which are expected to h