bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interactions of fibrinolytic system proteins with lysine‐containing surfaces
Authors: McClung W.G. , Clapper D.L. , Anderson A.B. , Babcock D.E. , Brash J.L. 
Published: August 2003

AbstractStudies on the interactions of tissue plasminogen activator (tPA) and plasminogen with polyurethane surfaces containing ϵ‐lysine moieties (ϵ‐amino group free) are reported. These surfaces are considered to have the potential to dissolve nascent clots that may be formed on them. For adsorption from both single protein solutions and plasma, the surfaces were found to have a high capacity for tPA as well as plasminogen. A significant fraction of preadsorbed tPA was displaced from the ϵ‐lysine surfaces upon contact with plasma. These surfaces, when preadsorbed with tPA and then incubated with plasma, were able to dissolve incipient clots formed around them. However, the clot‐dissolving capacity diminished as the time of plasma incubation increased, presumably due to loss of tPA. It was also shown that in plasma, preadsorbed tPA is displaced from these surfaces largely by plasminogen, which thus appears to have a greater binding affinity than tPA for the ϵ‐lysine moieties. Finally, it was found that in plasma, the ϵ‐lysine surfaces interact with plasminogen in a dynamic manner, and that about 70% of the bound plasminogen is exchanging continuously with plasminogen in the plasma. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 795–801, 2003
A biodegradable electrical bioconductor made of polypyrrole nanoparticle/poly(D,L‐lactide) composite: A preliminary in vitro biostability study
Authors: Wang Zhaoxu , Roberge Christophe , Wan Ying , Dao Lê H. , Guidoin Robert , Zhang Ze 
Published: August 2003

AbstractThe electrical stability of a novel polypyrrole (PPy)/poly(D,L‐lactide) (PDLLA) composite was studied in vitro and compared with that of PPy‐coated polyester fabrics. Specimens were incubated in Ringer's solution at 37°C for up to 8 weeks with or without the circulation of DC current under a constant 100 mV voltage. In situ current variation with incubation time was recorded. The AC volume electrical conductivity of the specimens before and after incubation in phosphate‐buffered saline was recorded using a frequency analyzer. Water absorption and weight loss were monitored metrologically. Changes in the oxidation state of incubated PPy were analyzed with X‐ray photoelectron spectroscopy. The morphological changes were observed with scanning electron microscopy, and the glass transition temperature of the PDLLA was investigated using differential scanning calorimetry. The PPy/PDLLA composite in Ringer's solution sustained a relatively stable conductivity up to 8 weeks after an initial period of “conditioning.” The PPy‐coated fabrics experienced a rapid loss of conductivity when subjected to electrical circulation and regained part of it when disconnected. The volume conductivity of the nonincubated PPy/PDLLA membrane behaved as a typical conductor in the low‐frequency range. The mechanisms involved in the various electrical behaviours of the PPy/PDLLA composite and PPy‐coated fabrics are discussed. In conclusion, the PPy/PDLLA composite was able to deliver a biologically significant electrical current in a simulated biological solution for up to 8 weeks and therefore may be considered as a first‐generation synthetic biodegradable bioconductor. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 738–746, 2003
The role of titanium in the altered endotoxin‐induced nitric oxide synthase expression in alveolar macrophages from titanium‐alloy‐implanted rats
Authors: Yang Rong‐Sen , Chen Yi‐Hung , Lin‐Shiau Shoei‐Yn , Liu Tang‐Kue , Liu Shing‐Hwa 
Published: August 2003

AbstractWe have found that the concentration of titanium (Ti) in the blood of patients with loosened Ti‐alloy prostheses is elevated. An increase in the levels of elemental Ti in the blood and lung tissues of rats with an alloyed‐Ti implant also has been found. The cellular reaction to elevated elemental Ti in the circulation remains unclear. We further performed experiments to examine the changes of inducible nitric oxide synthase (iNOS) expression in alveolar macrophages from alloyed‐Ti‐implanted rats. The elevation of nitrite and iNOS expression induced by lipopolysaccharide (LPS) was suppressed. The in vitro effect of a soluble form of Ti was further investigated. Ti (0.01–0.06 mM) inhibited the LPS‐induced nitrite production and iNOS expression in alveolar macrophages from normal rats without any cytotoxic effects. LPS induced protein tyrosine phosphorylation, tyrosine‐phosphorylation of lyn (a CD14‐receptor‐associated‐tyrosine kinase), and degradation of IκB‐α protein (inhibitor of NF‐κB) in alveolar macrophages. These events were inhibited by co‐incubation with Ti. These results indicate that elemental Ti may impair iNOS expression in alveolar macrophages through the alteration of protein tyrosine phosphorylation and NF‐κB activation. The inhibitory action of Ti on cellular responses of alveolar macrophages may be anti‐inflammatory and thus may depress local defense mechanisms related to microbial killing. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 802–810, 2003
Suppression of subcritical crack growth in a leucite‐reinforced dental glass by ion exchange
Authors: Fischer Horst , Marx Rudolf 
Published: August 2003

AbstractGlass‐ceramic materials are frequently used in prosthetic dentistry because of their excellent esthetics. Problematic aspects of glass ceramics are their limited strength, the scatter in their strength data, and their time‐dependent strength decrease due to subcritical crack growth effects. The short‐term strength level can be significantly increased by an ion‐exchange process in a potassium salt. A dual ion‐exchange process in KNO3/NaNO3 can additionally improve the scatter‐in‐strength. The objective of the present study was to examine the effect of a single and a dual ion‐exchange process on the characteristic time‐dependent strength decrease of a leucite‐reinforced dental glass. The parameters of subcritical crack growth were evaluated by using the constant stress rate flexural strength test. Both ion‐exchange processes showed a pronounced effect on the subcritical crack growth of the glass‐ceramic material. The exponential crack parameter n was increased from 25 to 52 by the single‐exchange and to 107 by the dual‐exchange process, respectively. We conclude that the time‐dependent strength decrease of a dental glass‐ceramic material can be significantly limited by the ion‐exchange process. This could improve the clinical reliability of dental restorations made from this class of materials. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 885–889, 2003
Room‐temperature preparation and characterization of poly (ethylene glycol)‐coated silica nanoparticles for biomedical applications
Authors: Xu Hao , Yan Fei , Monson Eric E. , Kopelman Raoul 
Published: August 2003

AbstractMonodisperse, spherical, polyethylene glycol (PEG)–coated silica nanoparticles have been prepared at room temperature and characterized for the purpose of biomedical applications. The particles were synthesized by the hydrolysis of tetramethyl orthosilicate (TMOS) in alcohol media under catalysis by ammonia, and their size can range from about 50–350 nm in diameter. We studied the particle size and size distribution using a scanning electron microscope (SEM) and an asymmetric field‐flow fractionation (AFFF) multiangle static light‐scattering instrument. The chemical and/or physical binding of PEG to the silica nanoparticles was studied by infrared spectroscopy, and the weight percentage of PEG attached to the particles was quantified. The PEG‐coated silica nanoparticles showed enhanced colloidal stability when redispersed into aqueous solutions from the dried state as a result of the steric stabilization function of the PEG polymer grafted on the surface of particles. A nonspecific protein‐binding test was also carried out to show that the PEG coating can help reduce the protein adsorption onto the surface of the particles, relating to the biocompatibility of these PEG‐coated particles. Also, the inclusion of magnetic nanoparticles into the silica particles was shown as an example of the possible applications of PEG‐coated silica particles. These silica nanoparticles, as a matrix for encapsulation of certain reagents, have potential for applications to in vivo diagnosis, analysis, and measurements inside intact biologic systems. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 870–879, 2003
Microhardness of superficial and deep sound human dentin
Authors: Fuentes Victoria , Toledano Manuel , Osorio Raquel , Carvalho Ricardo M. 
Published: August 2003

AbstractOur purpose in this study was to determine the microhardness of superficial and deep dentin by means of two indentation methods (Knoop and Vickers) under two different applied loads. Twelve dentin discs approximately 2‐mm thick were obtained from both superficial and deep dentin by transversally sectioning the crowns of sound, extracted human third molars with a diamond blade under water irrigation. Dentin surfaces were sequentially polished, and indentations (n = 20 per surface) were performed with either Vickers indentor at loads of 300 and 500 g, respectively, or Knoop indentor at loads of 50 and 100 g, respectively. Average Vickers hardness number (VHN) and Knoop hardness number (KHN) were calculated and treated with two‐way analysis of variance (ANOVA) and Student's t test. Microhardness of dentin was not influenced by the different loads applied for both indentation methods. Knoop hardness was significantly higher for superficial than for deep dentin (p < 0.05). Conversely, Vickers hardness was not significantly different for both substrates (p > 0.05). Differences in dentin hardness as a function of depth exist, but they might not be relevant, and no alteration of the distribution of stresses along the adhesive interface is expected. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 850–853, 2003
Extracellular matrix degrading enzymes are active in porcine stentless aortic bioprosthetic heart valves
Authors: Simionescu Dan T. , Lovekamp Joshua J. , Vyavahare Narendra R. 
Published: August 2003

AbstractGlutaraldehyde‐fixed porcine aortic valve tissues are widely used for heart valve replacement surgery in the form of bioprosthetic heart valves (BHVs). The durability of BHVs in the clinical setting is limited by tissue degeneration, mechanical failure, and calcification. BHVs rely on the putative ability of glutaraldehyde to render biologic tissues metabolically inert and fully resistant to enzymatic attack. In the present study, we detected and partially characterized the activity of collagen and elastin‐degrading enzymes in unimplanted, glutaraldehyde‐fixed porcine aortic cusp and wall tissues and compared enzyme activities with those extracted from fresh tissues. Active enzymes capable of degrading extracellular matrix were found to be present in soluble form as well as immobilized on glutaraldehyde‐crosslinked tissue matrix. Total levels of collagenolytic activities were evaluated to approximately 0.25 μg of degraded collagen/mg of dry tissue/24 h for both glutaraldehyde‐fixed wall and cusp tissues. A major finding of this study was the ability of soluble tissue enzymes to partially degrade glutaraldehyde‐fixed collagen and particularly large amounts of glutaraldehyde‐fixed elastin. These calcium‐dependent gelatinases share many biochemical similarities with matrix metalloproteinases. These data strongly indicate that glutaraldehyde‐fixed porcine valvular tissues are not metabolically inert and are not entirely resistant to enzymatic attack, thereby rendering BHVs vulnerable to biologic degeneration and subsequent chronic failure. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 755–763, 2003
Biomimetic surface modification of poly (L‐lactic acid) with gelatin and its effects on articular chondrocytes in vitro
Authors: Cui Yuan Lu , Hou Xin , Qi Ai Di , Wang Xiang Hui , Wang Hong , Cai Kai Yong , Ji Yin Yu , De Yao Kang 
Published: August 2003

AbstractOur objective in this study was to investigate the efficiency of two treatments for poly (L‐lactic acid) (PLLA) surface modification with gelatin, via entrapment and coupling, using 1‐ethyl‐3‐(3‐dimethylaminopropyl)carbodiimide (EDC) and N‐hydroxysuccinimide (NHS). The properties of original PLLA, gelatin‐entrapped, and coupled PLLA films were investigated by water contact angle measurement and electron spectroscopy for chemical analysis (ESCA). The water contact angle indicated that the incorporation of gelatin resulted in a change in hydrophilicity, and the ESCA data suggested that the modified PLLA films became enriched with nitrogen atoms. The cytocompatibility of modified PLLA films might be improved. Therefore, we examined the attachment and proliferation of bovine articular chondrocyte seeded on modified PLLA films and virgin films. A whole‐cell enzyme‐linked immunosorbent assay (cell ELISA) that detects 5‐bromo‐2′‐deoxyuridine (BrdU) incorporation during DNA synthesis and collagen type II secretion was applied to evaluate the chondrocytes on different PLLA films and tissue culture plates (TCPS). Cell viability was estimated by the MTT [3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyl tetrazolium bromide] assay, and cell function was assessed by measuring glycosaminoglycan (GAG) secreted by chondrocytes. These results implied that gelatin used to modify the PLLA surface through entrapment and coupling could enhance chondrocyte adhesion, proliferation, and function. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 770–778, 2003
Adherent octacalciumphosphate coating on titanium alloy using modulated electrochemical deposition method
Authors: Lin Shujie , LeGeros Racquel Z. , LeGeros John P. 
Published: August 2003

AbstractOur aims in this study were (1) to develop an electrochemical method of depositing adherent octacalciumphosphate (OCP) and other calcium phosphate coatings on titanium alloy (Ti6Al4V) substrates of different shapes and surface preparations, (2) to determine the properties of the coating (composition, morphology, thickness, dissolution), and (3) to observe transformation of OCP to carbonatehydroxyapatite (CHA) in simulated body fluid (SBF). Titanium (Ti)‐alloy plates, tensile bars with four types of surfaces (grit‐blasted with apatitic abrasive, chemically textured, arc‐deposited, and CoCr‐beaded) and dissolution cylinders were electrochemically coated with the use of modulated pulse time electric fields programmed with a custom‐made dual microprocessor. Modulated electrochemical deposition (MECD) was carried out with pH and temperature conditions favorable for OCP formation. Coatings were characterized using X‐ray diffraction, FT‐IR, scanning electron microscopy, tensile strength tests, and solubility tests. XRD and FT‐IR analyses showed that pure, uniform OCP coatings were produced on Ti6Al4V surfaces with coating‐to‐substrate tensile strengths greater than 7000 psi. Coatings on Ti arc‐deposited surfaces, chemically textured surfaces, and CoCr‐beaded surfaces all gave tensile strengths ranging from 5000 to 7000 psi, with no coating shadows in the crevices. Dissolution of OCP coating in 100 mL of 0.1 M Tris buffer solution was determined from the amount of calcium (Ca) released onto the buffer, which was 7.7 ± 1.0 ppm Ca at pH 7.3 after 4 h, and 22 ∓ 1.4 ppm Ca at pH 3 after 2 h. We found that OCP crystal size can be controlled by the current density and relative pulse time modulation. Our study demonstrated the following: (1) Highly adherent calcium phosphate (e.g., OCP) coating of uniform compositions (e.g., OCP) on Ti‐alloy substrates can be obtained at low temperatures with the use of MECD by optimizing pulse time modulation of the electric field, reaction pH, temperature, and electrolyte composition; and (2) OCP readily transforms to CHA when exposed to SBF. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 819–828, 2003
Immunocytochemical identification of type I collagen in acid‐etched dentin
Authors: Breschi Lorenzo , Perdigão Jorge , Gobbi Pietro , Mazzotti Giovanni , Falconi Mirella , Lopes Manuela 
Published: August 2003

AbstractThe hypothesis tested in this study is that the application of phosphoric acid prevents collagen fibrils (CF) from maintaining their structural morphology, as assessed by their immunochemical antigenicity. Dentin was conditioned with EDTA and with 35% H3PO4 for 15, 30, and 60 s. For a control there was no treatment. A pre‐embedding immunohistochemical procedure was evaluated under high‐resolution SEM and a postembedding immunolocalization technique was performed on ultrathin sections at TEM level. Conditioning with EDTA resulted in a weaker labeling signal than for dentin conditioned with H3PO4. The most intense labeling was observed after dentin had been etched with H3PO4 for 15 s. The least intensive labeling was evident when the acid was applied for 30 s or for 60 s. A very weak signal was detected on the untreated dentin surface. These results provide evidence that a 15‐s application of 35% H3PO4 causes mineral dissolution of the crystals enveloping the superficial CF without damaging the ultrastructure of the CF while longer applications of 35% H3PO4 cause alterations in the CF that decrease their antigenicity. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 764–769, 2003
Effects of materials parameters on mineralization and degradation of sol‐gel bioactive glasses with 3D‐ordered macroporous structures
Authors: Zhang Kai , Yan Hongwei , Bell David C. , Stein Andreas , Francis Lorraine F. 
Published: August 2003

AbstractBioactive glasses (BGs) with three‐dimensionally ordered macroporous (3DOM) structures were prepared by combining a sol‐gel synthesis with colloidal crystal templating. 3DOM sol‐gel BGs with two compositions (20 mol % CaO–80% SiO2 and 20 mol % CaO–4% P2O5–76% SiO2) and three macropore sizes (average: 345, 440, and 790 nm) were prepared. Glasses were separated into two particle sizes (212 μm < small < 355 μm and 600 μm < large < 1000 μm). The glasses were soaked in simulated body fluid at 37°C for 2 or 4 days and the effects of composition, particle size, and macropore size on the formation of apatite and glass degradation were characterized. Within the parameter range of the experiments, several comparisons could be made. First, the formation of apatite and degradation of the glass were slightly enhanced for the phosphate containing composition. Second, large particles formed less apatite and degraded less completely compared with small particles. Lastly, an increase in macropore size slowed down the glass degradation and apatite formation processes, an effect related to the decreased internal surface area of the larger pore materials. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 860–869, 2003
Osteogenecity of octacalcium phosphate coatings applied on porous metal implants
Authors: Barrère Florence , van der Valk Chantal M. , Dalmeijer Remco A. J. , Meijer Gert , van Blitterswijk Clemens A. , de Groot Klaas , Layrolle Pierre 
Published: August 2003

AbstractThe biomimetic route allows the homogeneous deposition of calcium phosphate (Ca‐P) coatings on porous implants by immersion in simulated physiologic solution. In addition, various Ca‐P phases, such as octacalcium phosphate (OCP) or bone‐like carbonated apatite (BCA), which are stable only at low temperatures, can be deposited. In this pilot study, experiments were designed with a twofold‐purpose: (1) to investigate the osteoinduction of OCP‐coated and noncoated porous tantalum cylinders and of dense titanium alloy cylinders (5 mm in diameter and 10 mm in length) in the back muscle of goats at 12 and 24 weeks (n = 4); and (2) to compare the osteogenic potentials of BCA‐coated, OCP‐coated, and bare porous tantalum cylinders in a gap of 1 mm created in the femoral condyle of a goat at 12 weeks (n = 2). In the goat muscle, after 12 weeks the OCP‐coated porous cylinder had induced ectopic bone as well as bone within the cavity of the OCP‐coated dense titanium cylinder. In the femoral condyle, bone did not fill the gap in any of the porous implants. In contrast with the two other groups, OCP‐coated porous cylinders exhibited bone formation in the center of the implant. The nature of the Ca‐P coating, via its microstructure, its dissolution rate, and its specific interactions with body fluids, may influence the osteogenecity of the Ca‐P biomaterial. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 779–788, 2003
Corrosion resistance of stressed NiTi and stainless steel orthodontic wires in acid artificial saliva
Authors: Huang Her‐Hsiung 
Published: August 2003

AbstractThe purpose of this study was to investigate the corrosion resistance of stressed NiTi and stainless steel orthodontic wires using cyclic potentiodynamic and potentiostatic tests in acid artificial saliva at 37°C. An atomic force microscope was used to measure the 3‐D surface topography of as‐received wires. Scanning electron microscope observations were carried out before and after the cyclic potentiodynamic tests. The surface chemical analysis was characterized using X‐ray photoelectron spectroscopy and Auger electron spectroscopy after the potentiostatic tests. The cyclic potentiodynamic test results showed that the pH had a significant influence on the corrosion parameters of the stressed NiTi and stainless steel wires (p < 0.05). The pitting potential, protection potential, and passive range of stressed NiTi and stainless steel wires decreased on decreasing pH, whereas the passive current density increased on decreasing pH. The load had no significant influence on the above corrosion parameters (p > 0.05). For all pH and load conditions, stainless steel wire showed higher pitting potential and wider passive range than NiTi wire (p < 0.001), whereas NiTi wire had lower passive current density than stainless steel wire (p < 0.001). The corrosion resistance of the stressed NiTi and stainless steel wires was related to the surface characterizations, including surface defect and passive film. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 829–839, 2003