bluuebunny/crossref_metadata_2025_split huggingface dataset:
Demand assessment and price‐elasticity estimation of quality‐improved primary health care in palestine: a contribution from the contingent valuation method
Authors: Mataria Awad , Luchini Stéphane , Daoud Yousef , Moatti Jean‐Paul 
Published: February 2007

AbstractThis paper proposes a new methodology to assess demand and price‐elasticity for health care, based on patients' stated willingness to pay (WTP) values for certain aspects of health care quality improvements. A conceptual analysis of how respondents consider contingent valuation (CV) questions allowed us to specify a probability density function of stated WTP values, and consequently, to model a demand function for quality‐improved health care, using a parametric survival approach. The model was empirically estimated using a CV study intended to assess patients' values for improving the quality of primary health care (PHC) services in Palestine. A random sample of 499 individuals was interviewed following medical consultation in four PHC centers. Quality was assessed using a multi‐attribute approach; and respondents valued seven specific quality improvements using a decomposed valuation scenario and a payment card elicitation technique. Our results suggest an inelastic demand at low user fees levels, and when the price‐increase is accompanied with substantial quality‐improvements. Nevertheless, demand becomes more and more elastic if user fees continue to rise. On the other hand, patients' reactions to price‐increase turn out to depend on their level of income. Our results can be used to design successful health care financing strategies that include a consideration of patients' preferences and financial capacities. Copyright © 2007 John Wiley & Sons, Ltd.
Biomembrane mimetic polymer poly (2‐methacryloyloxyethyl phosphorylcholine‐co‐n‐butyl methacrylate) at the interface of polyurethane surfaces
Authors: Lee I. , Kobayashi K. , Sun H.Y. , Takatani S. , Zhong L.G. 
Published: February 2007

AbstractPolyurethane (PU) is widely used to make artificial heart and blood vessel wells; however, its thrombogenicity in vivo is still in question. The biomembrane‐mimetic and water‐soluble polymers, poly (2‐methacryloyloxyethyl phosphorylcholine‐co‐n‐butyl methacrylate) (PMB), were used to modify polyurethane (PU) surfaces for improving their hemocompatibility. The morphologies of the PMB modified PU surfaces were examined by using atomic force microscopy and the parameters of the PMB absorption kinetics were extracted from dynamic water contact angle measurements. Two‐phase domains, the hard and soft segment phases, were observed on the PU surfaces under the aqueous conditions. The absorbed PMB molecules formed the isolated layers first on the hydrophobic hard segments, and subsequently networked as the PMB concentration increased. The increments of PMB concentration led to the decrement of the effective molar activation (wetting) free energy ΔG. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2007
Fabrication and characterization of porous hyaluronic acid–collagen composite scaffolds
Authors: Tang Shunqing , Vickers Scott M. , Hsu Hu‐Ping , Spector Myron 
Published: February 2007

AbstractHyaluronic acid (HA) plays a vital role in many tissues, influencing water content and mechanical function, and has been shown to have positive biological effects on cell behavior in vitro. To begin to determine whether these benefits can be accessed if HA is incorporated into collagen‐based scaffolds for tissue engineering, HA‐collagen composite matrices were prepared and selected properties evaluated. HA‐collagen scaffolds were cross‐linked with carbodiimide and loss rates of HA in culture medium assessed. Scaffold pore structures were evaluated by light and electron microscopy. Adult canine chondrocytes were grown in selected HA‐collagen scaffolds to assess the effects of HA on cell behavior. Homogenous HA‐collagen slurries were achieved when polyionic complexes were suppressed. HA was uniformly distributed through the scaffolds, which demonstrated honeycomb‐like pores with interconnectivity among pores increasing as HA content increased. Virtually all of the HA added to the collagen slurry was incorporated into the composite scaffolds that underwent a 7‐day cross‐linking protocol. After 5 days in culture medium, the HA content in the scaffolds was 5–7% regardless of initial HA loading. After only 2 weeks in culture cartilaginous tissue was found in the chondrocyte‐seeded HA‐collagen scaffolds. This study contributes to the understanding of the effects of HA content, pH, and cross‐link treatment on pore characteristics and degradation behavior essential for the design of HA‐collagen scaffolds. The demonstration that these scaffolds can be populated by chondrocytes and support in vitro formation of cartilaginous tissue warrants further investigation of this material system for tissue engineering. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2007
Development of superporous hydroxyapatites and their examination with a culture of primary rat osteoblasts
Authors: Sakamoto Michiko , Nakasu Masanori , Matsumoto Toshio , Okihana Hiroyuki 
Published: February 2007

AbstractWhen the usage of hydroxyapatite (HAp) was first approved at clinics by the Kouseishou (Japanese FDA) as a bone substitute (APACERAM), the upper limit of pore content was set at 60%. Cells play an important role in bone repair, especially in regeneration therapy, but on using these HAps, the cells cannot penetrate deeply into them because their inside pores rarely connect. To promote cell penetration into the inside of the HAps, we have developed superporous HAps (HAp‐Ss). First, phosphoric acid was added to a calcium hydroxide solution, and the mixture was dried by the spray‐dry method to produce fine primary particles. Then, two kinds of surfactants were used to form a large amount of pores. These two HAp‐Ss have 85% porosity and interconnected pores in the inside. They were tested with a culture of primary rat osteoblasts, which showed good penetration therein. The penetrated osteoblasts maintained high alkaline phosphatase activity during the culture period. This indicates that the developed HAp‐Ss are very good bone substitutes and also useful scaffolds in bone regeneration therapy. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2007
Cationized pullulan 3D matrices as new materials for gene transfer
Authors: San Juan Aurélie , Hlawaty Hanna , Chaubet Frédéric , Letourneur Didier , Feldman Laurent J. 
Published: February 2007

AbstractThis study deals with the development of a novel biocompatible cationized pullulan three‐dimensional matrix for gene delivery. A water‐soluble cationic polysaccharide, diethylaminoethyl‐pullulan (DEAE‐pullulan), was first synthesized and characterized. Fluorescence quenching and gel retardation assays evidenced the complexation in solution of DNA with DEAE‐pullulan, but not with neutral pullulan. On cultured smooth muscle cells (SMCs) incubated with DEAE‐pullulan and a plasmid vector expressing a secreted form of alkaline phosphatase (pSEAP), SEAP activity was 150‐fold higher than with pSEAP alone or pSEAP with neutral pullulan. DEAE‐pullulan was then chemically crosslinked using phosphorus oxychloride. The resulting matrices were obtained in less than a minute and molded as discs of 12 mm diameter and 2 mm thickness. Such DEAE‐pullulan 3D matrices were loaded with up to 50 μg of plasmid DNA, with a homogeneous plasmid loading observed with YOYO‐1 fluorescence staining. Moreover, the DEAE‐pullulan matrix was shown to protect pSEAP from DNase I degradation. Incubation of cultured SMCs with pSEAP‐loaded DEAE‐pullulan matrices resulted in significant gene transfer without cell toxicity. This study suggests that these cationized pullulan 3D matrices could be useful biomaterials for local gene transfer. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2007
The role of the surface chemistry of CoCr alloy particles in the phagocytosis and DNA damage of fibroblast cells
Authors: Lewis A. C. , Ladon D. , Heard P. J. , Peto L. , Learmonth I. 
Published: February 2007

AbstractSurface chemistry of CoCr particles is demonstrated to be fundamental to the process of phagocytosis by fibroblast cells in vitro. Particles preincubated in serum for 5 days and washed in water before addition to cell cultures were phagocytosed less readily than were particles preincubated in minimal essential medium (MEM) for 1 h and washed in water. This was explained by the coating of calcium phosphate and protein on the serum‐immersed particles investigated by time‐of‐flight secondary ion mass spectroscopy. The cells incubated with the serum‐immersed particles had a reduced mitotic index when compared with the MEM‐immersed particles, indicating that the phagocytosed particles were causing cell cycle arrest. The release of soluble ions measured by electrothermal atomic absorption spectroscopy within the first hour of particle immersion in MEM was identified as the most likely cause for the DNA damage measured by single cell gel electrophoresis (“Comet” assay). Cryofocused ion beam SEM with a spatial resolution of 8 nm was used to cross section cells, to investigate the location of the phagocytosed particles, some of which were found within the nuclear membrane. This paper demonstrated that consideration of the surface chemistry is essential to understand the processes of the effects of orthopedic wear debris. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2007
Coating nanothickness degradable films on nanocrystalline hydroxyapatite particles to improve the bonding strength between nanohydroxyapatite and degradable polymer matrix
Authors: Nichols Heather L. , Zhang Ning , Zhang Jing , Shi Donglu , Bhaduri Sarit , Wen Xuejun 
Published: February 2007

AbstractHydroxyapatite (HA) nanoparticles are similar to bone apatite in size, phase composition, and crystal structure. When compared with micron‐size HA particles, nano‐HA possesses improved mechanical properties and superior bioactivity for promoting bone growth and regeneration. However, scaffolds fabricated from nano‐HA alone cannot meet the mechanical requirements for direct‐loading applications. A number of studies suggest that nanostructured composites may offer surface and/or chemical properties of native bone, and therefore represent ideal substrates to support bone regeneration. However, a common problem with nanohydroxyapatite (nano‐HA)–polymer composites is the weak binding strength between the nano‐HA filler and the polymer matrix since they are two different categories of materials and cannot form covalent bonds between them during the mixing process. Often, the mechanical strength of the composite is compromised due to the phase separation of the HA filler from the polymer matrix during the tissue repair process. To overcome this problem, an ultrathin degradable polymer film was grafted onto the surface of nano‐HA using a radio‐frequency plasma polymerization technology from acrylic acid monomers. The treated nano‐HA powders are expected to bind to the polymer matrix via covalent bonds, thus enhancing the mechanical properties of the resultant composites. High‐resolution transmission electron microscopy (HRTEM) experiments showed that an extremely thin polymer film (2 nm) was uniformly deposited on the surfaces of the nanoparticles. The HRTEM results were confirmed by X‐ray photoelectron spectroscopy (XPS) and time‐of‐flight secondary ion mass spectroscopy (TOFSIMS). Tensile tests performed on the specimens revealed that the degradable coating had improved elastic and strength properties when compared with the nondegradable and uncoated controls. XPS and TOSIMS data revealed that more functional carboxyl groups were formed on degradable coatings than cross‐linked nondegradable coatings. Cytocompatibility assay demonstrated that both the degradable and nondegradable coatings are cytocompatible. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2007
Peptide surface modification of methacrylamide chitosan for neural tissue engineering applications
Authors: Yu Laura M. Y. , Kazazian Karineh , Shoichet Molly S. 
Published: February 2007

AbstractNerve fibres are guided to their targets by the combined actions of chemotactic and haptotactic stimuli; however, translating these stimuli to a scaffold that will promote nerve regeneration is nontrivial. In pursuit of this goal, we synthesized and characterized cell‐adhesive, biodegradable chitosan scaffolds. Chitosan amine groups were reacted with methacrylic anhydride resulting in a water soluble methacrylamide chitosan (MC) that was then crosslinked by radical polymerization resulting in a scaffold. Biodegradability by lysozyme and penetrability of the scaffold by rat superior cervical ganglion (SCG) neurons were studied. Maleimide‐terminated cell adhesive peptides, mi‐GDPGYIGSR and mi‐GQASSIKVAV, were coupled to a thiolated form of MC to promote cell adhesion. The MC scaffold was found to be porous, biodegradable, and to allow neurite penetration. Interestingly, all of these properties were found to depend upon the amount of initiator used in crosslinking. Covalent modification of the MC scaffold with cell adhesive peptides significantly improved neuronal adhesion and neurite outgrowth. The MC can be crosslinked to form a novel scaffold, where our results demonstrate its suitability in neural tissue engineering and its potential for other engineered tissues, such as cartilage repair, where chitosan has already demonstrated some utility. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2007
Characterization of biomimetic calcium phosphate on phosphorylated chitosan films
Authors: Chesnutt B. M. , Yuan Y. , Brahmandam N. , Yang Y. , Ong J. L. , Haggard W. O. , Bumgardner J. D. 
Published: February 2007

AbstractThis study examined the effect of chitosan degree of deacetylation (DDA), concentration of simulated body fluid (SBF), and mineralization time on the composition, structure, and crystallinity of calcium phosphate (CaP) biomimetically deposited on chitosan and on osteoblast cell growth. Phosphorylated chitosan films of 92.3%, 87.4%, and 80.6% DDA were soaked in SBF (1.0× or 1.5×) for 7, 14, or 21 days. Scanning electron microscopy revealed that CaP precipitated from 1.5× SBF had a porous, granular morphology; while the coatings precipitated in 1.0× SBF were smoother and more uniform. X‐ray diffraction showed that films mineralized in 1.0× SBF were amorphous, while films mineralized in 1.5× SBF for 21 days exhibited crystalline peaks similar to hydroxyapatite, with the most crystalline peaks seen on 92.3% DDA chitosan. When mineralized films were placed in cell media for 14 days, more calcium phosphate precipitated onto all films, and the most calcium phosphate was found on 92.3% DDA films mineralized in 1.5× SBF. After seven days of osteoblast culture, there were approximately three times as many cells (based on DNA measurements, p < 0.05) on 92.3% DDA films soaked in 1.0× SBF for seven or 21 days than on 80.6% DDA films soaked in 1.0× SBF for any length of time or any films soaked in 1.5× SBF. The DDA of chitosan, concentration of SBF and mineralization time affect the structure of and biological response to chitosan/biomimetic CaP films, and these factors must be considered when designing new materials to be used in orthopaedic and dental/craniofacial implant applications. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2007
Robotic deposition of model hydroxyapatite scaffolds with multiple architectures and multiscale porosity for bone tissue engineering
Authors: Dellinger Jennifer G. , Cesarano Joseph , Jamison Russell D. 
Published: February 2007

AbstractModel 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 μm) were designed by controlling the arrangement and spacing between rods of HA. Micropores (1–30 μm) and submicron pores (less than 1 μm) 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. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2007
In vitro growth and differentiated activities of human periodontal ligament fibroblasts cultured on salmon collagen gel
Authors: Nagai Nobuhiro , Mori Kazuo , Satoh Yasuharu , Takahashi Noritaka , Yunoki Shunji , Tajima Kenji , Munekata Masanobu 
Published: February 2007

AbstractMarine‐derived collagen is expected to be a much safer alternative to calf collagen, which in medical applications carries the risk of bovine spongiform encephalopathy. In this study, acid‐soluble collagen was extracted from salmon skin and crosslinked with 1‐ethyl‐3‐(3‐dimethylaminopropyl)‐carbodiimide during fibril formation to produce a crosslinked salmon collagen (SC) gel. The growth rates and the differentiated functions of human periodontal ligament fibroblasts (HPdLFs) cultured on the SC gel were investigated. Growth was faster on the SC gel than on porcine collagen (PC) gel. In addition, the HPdLFs cultured on the SC gel exhibited higher alkaline phosphatase (ALP) activity than those cultured on the PC gel. Quantitative RT‐PCR revealed higher mRNA expression of type I collagen, ALP, and osteocalcin in the HPdLFs cultured on the SC gel. HPdLFs had a flat shape on the SC gel and a spindle shape on the PC gel, as revealed by observation with scanning electron microscopy and immunostaining with cytoskeletal protein and vinculin. The results showed that HPdLFs could grow and show highly differentiated activity on the SC gel as well as on the PC gel. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2007
Novel tubular composite matrix for bone repair
Authors: Kofron M.D. , Cooper J.A. , Kumbar S.G. , Laurencin C.T. 
Published: February 2007

AbstractTissue engineering develops organ replacements to overcome the limitations associated with autografts and allografts. The work presented here details the development of biodegradable, porous, three‐dimensional polymer–ceramic‐sintered microsphere matrices to support bone regeneration. Poly(lactide‐co‐glycolide)/hydroxyapatite microspheres were formed using solvent evaporation technique. Individual microspheres were placed in a cylindrical mold and sintered at various temperatures. Scaffolds were characterized using scanning electron microscopy, mercury porosimetry, and mechanical testing in compression. After varying the temperature of sintering, a single temperature was selected and the time of sintering was varied. Mechanical testing indicated that as the sintering temperature or time was increased, the elastic modulus, compressive strength, maximum compressive load, and energy at failure significantly increased. Furthermore, increasing the sintering temperature or time resulted in a decreased porosity and the spherical morphology of the microspheres was lost as the microspheres blended together. To more closely mimic the bone marrow cavity observed in native bone tissue, tubular composite‐sintered microsphere matrices were formed. These scaffolds demonstrated no statistically significant difference in compressive mechanical properties when compared with cylindrical composite‐sintered microsphere matrices of the same dimension. One potential application for these scaffolds is bone regeneration. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2007
Surface mechanical properties, corrosion resistance, and cytocompatibility of nitrogen plasma‐implanted nickel–titanium alloys: A comparative study with commonly used medical grade materials
Authors: Yeung K.W.K. , Poon R.W.Y. , Chu P.K. , Chung C.Y. , Liu X.Y. , Lu W.W. , Chan D. , Chan S.C.W. , Luk K.D.K. , Cheung K.M.C. 
Published: February 2007

AbstractStainless steel and titanium alloys are the most common metallic orthopedic materials. Recently, nickel–titanium (NiTi) shape memory alloys have attracted much attention due to their shape memory effect and super‐elasticity. However, this alloy consists of equal amounts of nickel and titanium, and nickel is a well known sensitizer to cause allergy or other deleterious effects in living tissues. Nickel ion leaching is correspondingly worse if the surface corrosion resistance deteriorates. We have therefore modified the NiTi surface by nitrogen plasma immersion ion implantation (PIII). The surface chemistry and corrosion resistance of the implanted samples were studied and compared with those of the untreated NiTi alloys, stainless steel, and Ti‐6Al‐4V alloy serving as controls. Immersion tests were carried out to investigate the extent of nickel leaching under simulated human body conditions and cytocompatibility tests were conducted using enhanced green fluorescent protein mice osteoblasts. The X‐ray photoelectron spectroscopy results reveal that a thin titanium nitride (TiN) layer with higher hardness is formed on the surface after nitrogen PIII. The corrosion resistance of the implanted sample is also superior to that of the untreated NiTi and stainless steel and comparable to that of titanium alloy. The release of nickel ions is significantly reduced compared with the untreated NiTi. The sample with surface TiN exhibits the highest amount of cell proliferation whereas stainless steel fares the worst. Compared with coatings, the plasma‐implanted structure does not delaminate as easily and nitrogen PIII is a viable way to improve the properties of NiTi orthopedic implants. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2007
Macroporous condensed poly(tetra fluoro‐ethylene). II. In vivo effect on adhesion formation and tissue integration
Authors: Voskerician Gabriela , Rodriguez Analiz , Gingras Peter H. 
Published: February 2007

AbstractThis study investigated the in vivo correlation between construct parameters (surface area, pore size) and polymer chemistry in modulating mesh‐intestinal adhesions and mesh‐abdominal wall integration of condensed poly(tetra fluoro‐ethylene) (cPTFE) in hernia repair. A defect created by excising a 2 cm circular section of the abdominal wall from a rat was repaired with cPTFE or either one of the following synthetic meshes: expanded PTFE (ePTFE), ePTFE + polypropylene (PP), PP or PP + oxidized regenerated cellulose (ORC). The intestinal adhesion and abdominal wall integration were studied quantitatively by measuring the pull‐out force required to separate each mesh from the respective tissue at 1 and 3 months postimplantation. The hydrophobic, large pore meshes, such as cPTFE and ePTFE + PP led to reduced adhesions. Further, the presence of ORC contributed to reduction in adhesions of the more hydrophilic PP + ORC mesh. The large pore size, thinner meshes such as cPTFE and PP + ORC led to better tissue integration compared to the other meshes tested. Through hydrophobic chemistry, low profile, and increased pore size, cPTFE balances the rapid resolution of the inflammatory and wound healing response that resists adhesion formation, with efficient integration within the surrounding abdominal tissue. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2007