bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polymer design for corneal epithelial tissue adhesion: Pore density
Authors: Evans M. D. M. , Taylor S. , Dalton B. A. , Lohmann D. 
Published: January 2003

AbstractA porous polymer is required to sustain corneal epithelial tissue on the anterior surface of an implantable contact lens (corneal onlay). Porosity creates topography on the polymer surface and, if defined, this can be manipulated to elicit a particular tissue response. Previous work identified pores of 100‐nm diameter to be the critical size of a discontinuity in a polymer surface to facilitate the migration, stratification, and sustained adhesion of corneal epithelial tissue. Now we address the issue of pore density. Corneal epithelial tissue was grown for 21 days on nonporous polycarbonate and polycarbonate track‐etched with pores 100‐nm diameter with pore densities ranging from 0.27 and 14.4% of the total polymer surface area. Histology was used to score epithelial structure, and electron microscopy was used to quantitate the formation of adhesive structures (basal lamina and hemidesmosomes) at the tissue‐polymer interface. Data showed that epithelial tissue stratified and epithelial adhesive structures formed on polycarbonate surfaces with pore densities between 0.52 and 14.4% inclusive. This means that epithelial tissue can be maintained on a polymer where up to 14.4% of the surface is dedicated to small discontinuities in the form of pores 100‐nm diameter. These figures can be used to specify the design of a polymer for applications requiring epithelial cover. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 64A: 357–364, 2003
Effect of subtoxic concentrations of metal ions on NFκB activation in THP‐1 human monocytes
Authors: Lewis Jill B. , Randol Tabitha M. , Lockwood Petra E. , Wataha John C. 
Published: January 2003

AbstractTHP‐1 human monocytes and human peripheral blood monocytes have altered inflammatory cytokine secretion profiles after exposure to a variety of metal ions known to be released from biomaterials. Transcriptional regulation of these cytokines often involves activation of the transcription factor NFκB. The present study was designed to determine whether metal ion treatment of monocytes results in changes in levels of activated NFκB. THP‐1 cells were grown in suspension in the presence of sublethal concentrations of ions of Ag+, Co2+, Cu2+, Hg2+, Ni2+, and Pd2+. After 24 h of exposure to metal ions, the cells were harvested, counted, and the nuclear proteins extracted. Electrophoretic mobility shift assays were performed using a 32P‐ATP end‐labeled oligonucleotide consensus sequence for the NFκB transcription factor. DNA/protein complexes were quantified by phosphorimage analysis and compared by ANOVA (Tukey, α = 0.05). Exposure of THP‐1 cells to 100 μM of Pd2+ caused a significant increase in activated NFκB (p < 0.05) whereas treatment with 5 μM of Ag+ resulted in significantly decreased levels of nuclear NFκB (p < 0.05). No other metal ions tested caused a significant change in basal levels of nuclear NFκB (Co2+, Hg2+, Ni2+, and Cu2+). However, exposure to 50 μM of Cu2+ resulted in a reproducible, though not significant, increase in nuclear NFκB levels. These results indicate that inflammatory responses to some metal ions may be influenced by NFκB‐mediated transcriptional regulation. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 64A: 217–224, 2003
Sugar‐mediated chitosan/poly(ethylene glycol)‐β‐dicalcium pyrophosphate composite: Mechanical and microstructural properties
Authors: Wang Jian‐Wen , Hon Min‐Hsiung 
Published: January 2003

AbstractThe microstructural and mechanical properties of sugar‐mediated chitosan/poly(ethylene glycol)‐based scaffolds and composites, which are composed of β‐dicalcium pyrophosphate (β‐DCP) and sugar‐mediated scaffolds, were investigated. All of the scaffolds were prepared by various freeze‐drying protocols. The differences in the freeze‐drying process of the sugar‐mediated chitosan/poly(ethylene glycol) scaffold for three types of sugar (sucrose, glucose, and D‐fructose) were determined by scanning electron microscopic observation, water retention, density, and porosity analyses. The sugar‐mediated scaffolds prepared by scheme I of the freeze‐drying process show large pores, poorly connective interlayers, and disintegrated inner structures, different from the small pores and well‐connective channel structures as shown in the scheme II freeze‐drying process. The key factors for controlling pore structure and size in the scheme I freeze‐drying process were formulation and composition, but for the scheme II freeze‐drying process, the key factor was freeze protocol. The composite scaffolds were macroporous, and the microstructure changed considerably with added β‐DCP content. The incorporation of β‐DCP granules caused a significant enhancement of compressive modulus and yield strength. The increased mechanical strength may be attributable not only to the physical complexation between the sugar‐mediated scaffold and β‐DCP, but also the chemical reaction to apatite formed on the cell wall. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 64A: 262–272, 2003
Biological performance of biomimetic calcium phosphate coating of titanium implants in the dog mandible
Authors: Schliephake H. , Scharnweber D. , Dard M. , Röβler S. , Sewing A. , Hüttmann C. 
Published: January 2003

AbstractThe aim of the present study was to analyze the in vivo effect of biomimetic calcium phosphate coating of titanium implants on periimplant bone formation and bone‐/implant contact. Five types of implants were used: 1) Ti6Al4V implants with a polished surface; 2) Ti6Al4V implants with collagen coating; 3) Ti6Al4V implants with a mineralized collagen layer; 4) Ti6Al4V implants with sequential coating of hydroxyapatite (HA) and collagen; and 5) Ti6Al4V implants with HA coating only. All implants had square cross sections with an oblique diameter of 4.6 mm and were inserted press fit into trephine burr holes of 4.6 mm in the mandibles of ten beagle dogs. The implants of five animals each were evaluated after a healing period of 1 month and 3 months, respectively, during which time sequential fluorochrome labeling of bone formation had been performed. Bone formation was evaluated by morphometric measurement of the newly formed bone around the implants and the percentage of implant bone contact. After 1 month, there was a significantly higher percentage of mean bone/implant contact in the HA‐coated implants compared to those with polished surface and those with the collagen‐coated surface. After 3 months, these differences were not present anymore. Bone apposition was significantly higher next to implants with sequential HA/collagen coating compared to polished surfaces and mineralized collagen layer. It is concluded that biomimetic coating of titanium implants with HA has shown the clearest trend to increase bone–implant contact in the early ingrowth period. The addition of collagen to an HA coating layer may hold some promise when used as sequential HA/collagen coating with mineralized collagen as the surface layer. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 64A: 225–234, 2003
Flow perfusion culture of marrow stromal osteoblasts in titanium fiber mesh
Authors: van den Dolder Juliette , Bancroft Gregory N. , Sikavitsas Vassilios I. , Spauwen Paul H. M. , Jansen John A. , Mikos Antonios G. 
Published: January 2003

AbstractThe objective of this study was to evaluate the effect of two cell culture techniques, static and flow perfusion, on the osteogenic expression of rat bone marrow cells seeded into titanium fiber mesh for a period up to 16 days. A cell suspension of rat bone marrow stromal osteoblasts (5 × 105 cells/300 μL) was seeded into the mesh material. Thereafter, the constructs were cultured under static conditions or in a flow perfusion system for 4, 8, and 16 days. To evaluate cellular proliferation and differentiation, constructs were examined for DNA, calcium content, and alkaline phosphatase activity. Samples were also examined with scanning electron microscopy (SEM) and plastic‐embedded histological sections. Results showed an increase in DNA from day 4 to day 8 for the flow perfusion system. At day 8, a significant enhancement in DNA content was observed for flow perfusion culture compared with static culture conditions, but similar cell numbers were found for each culture system at 16 days. Calcium measurements showed a large increase in calcium content of the meshes subjected to flow perfusion at day 16. The SEM examination revealed that the 16‐day samples subjected to flow perfusion culture were completely covered with layers of cells and mineralized matrix. In addition, this matrix extended deep into the scaffolds. In contrast, meshes cultured under static conditions had only a thin sheet of matrix present on the upper surface of the meshes. Evaluation of the light microscopy sections confirmed the SEM observations. On the basis of our results, we conclude that a flow perfusion system can enhance the early proliferation, differentiation, and mineralized matrix production of bone marrow stromal osteoblasts seeded in titanium fiber mesh. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 64A: 235–241, 2003
Behavior of the bone–titanium interface after push‐in testing: A morphological study
Authors: Zaffe Davide , Rodriguez y Baena Ruggero , Rizzo Silvana , Brusotti Cesare , Soncini Monica , Pietrabissa Riccardo , Cavani Francesco , Quaglini Virginio 
Published: January 2003

AbstractFourteen titanium dental implants (Tioblast™) were implanted singly in the proximal tibia of New Zealand rabbits for 120 days. A bone defect was surgically produced and filled with Bio‐Oss® around six of these implants. After the animals were sacrificed and their organs harvested, bone segments were fixed and methacrylate embedded after the push‐in test had been performed. Microradiography was performed on longitudinal sections of the implants, whereas scanning electron microscope analysis was performed on the remaining embedded half‐implants using secondary electrons only. The results showed that the implants were apically and coronally surrounded by bone, whether Bio‐Oss® was used or not. Fractures were evident through the newly formed bone and between the pre‐existing and newly formed bone. Some fracture lines propagated through the bone and stopped at the implant surface without continuing along the bone–titanium interface. Detachment between the implant and the bone occurred at the coronal extremity of the implants and along its cervical region. These results highlight the fact that the bone–titanium interface has a high resistance to loading. It exhibited greater resistance than the newly formed bone and seems to behave in a manner similar to the cement lines of osteons. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 64A: 365–371, 2003
Chondrogenesis of human mesenchymal stem cells encapsulated in alginate beads
Authors: Ma Hsiao‐Li , Hung Shih‐Chieh , Lin Shan‐Yang , Chen Yuh‐Lien , Lo Wai‐Hee 
Published: January 2003

AbstractMesenchymal stem cells (MSCs) have the capacity for self‐renewal and can form bone, fat, and cartilage. Alginate forms a viscous solution when dissolved in 0.9% saline and gels on contact with divalent cations. The viability and phenotype maintenance of chondrocytes in alginate beads have been well documented. However, little is known about the effect of microencapsulation in alginate on chondrogenesis of MSCs. In this study, human MSCs encapsulated in alginate beads were cultured in serum‐free medium with the addition of transforming growth factor (TGF)β1 (10 ng/mL), dexamethasone (10−7M), and ascorbate 2‐phosphate (50 μg/mL). The MSCs in alginate assumed a rounded morphology with lacunae around them after 1 week in culture. Cell aggregates were observed at 2 weeks or longer in culture. Histological findings agreed with the clinical determination of hyaline cartilage, characterized by isolated cells with ground substance positive in Safranin‐O staining and immunohistochemistry for collagen type II at the periphery of cells. Reverse transcriptase–polymerase chain reaction (RT‐PCR) revealed the expression of COL2A1 and COL10A1, marker of chondrocytes and hypertrophy chondrocytes, respectively. These results indicate MSCs in alginate can form cartilage and the MSCs‐alginate system represents a relevant model for the study of the molecular mechanisms involved in the chondrogenesis and endochondral ossification. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 64A: 273–281, 2003
Vascularization and tissue infiltration of a biodegradable polyurethane matrix
Authors: Ganta Sudhakar R. , Piesco Nicholas P. , Long Ping , Gassner Robert , Motta Luis F. , Papworth Glenn D. , Stolz Donna B. , Watkins Simon C. , Agarwal Sudha 
Published: January 2003

AbstractUrethanes are frequently used in biomedical applications because of their excellent biocompatibility. However, their use has been limited to bioresistant polyurethanes. The aim of this study was to develop a nontoxic biodegradable polyurethane and to test its potential for tissue compatibility. A matrix was synthesized with pentane diisocyanate (PDI) as a hard segment and sucrose as a hydroxyl group donor to obtain a microtextured spongy urethane matrix. The matrix was biodegradable in an aqueous solution at 37°C in vitro as well as in vivo. The polymer was mechanically stable at body temperatures and exhibited a glass transition temperature (Tg) of 67°C. The porosity of the polymer network was between 10 and 2000 μm, with the majority of pores between 100 and 300 μm in diameter. This porosity was found to be adequate to support the adherence and proliferation of bone‐marrow stromal cells (BMSC) and chondrocytes in vitro. The degradation products of the polymer were nontoxic to cells in vitro. Subdermal implants of the PDI–sucrose matrix did not exhibit toxicity in vivo and did not induce an acute inflammatory response in the host. However, some foreign‐body giant cells did accumulate around the polymer and in its pores, suggesting its degradation is facilitated by hydrolysis as well as by giant cells. More important, subdermal implants of the polymer allowed marked infiltration of vascular and connective tissue, suggesting the free flow of fluids and nutrients in the implants. Because of the flexibility of the mechanical strength that can be obtained in urethanes and because of the ease with which a porous microtexture can be achieved, this matrix may be useful in many tissue‐engineering applications. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 64A: 242–248, 2003
Porous PEOT/PBT scaffolds for bone tissue engineering: Preparation, characterization, and in vitro bone marrow cell culturing
Authors: Claase Menno B. , Grijpma Dirk W. , Mendes Sandra C. , de Bruijn Joost D. , Feijen Jan 
Published: January 2003

AbstractThe preparation, characterization, and in vitro bone marrow cell culturing on porous PEOT/PBT copolymer scaffolds are described. These scaffolds are meant for use in bone tissue engineering. Previous research has shown that PEOT/PBT copolymers showed in vivo degradation, calcification, and bone bonding. Despite this, several of these copolymers do not support bone marrow cell growth in vitro. Surface modification, such as gas‐plasma treatment, is needed to improve the in vitro cell attachment. Porous structures were prepared using a freeze‐drying and a salt‐leaching technique, the latter one resulting in highly porous interconnected structures of large pore size. Gas‐plasma treatment with CO2 generated a surface throughout the entire structure that enabled bone marrow cells to attach. The amount of DNA was determined as a measure for the amount of cells present on the scaffolds. No significant effect of pore size on the amount of DNA present was seen for scaffolds with pore sizes between 250–1000 μm. Light microscopy data showed cells in the center of the scaffolds, more cells were observed in the scaffolds of 425–500 μm and 500–710 μm pore size compared to the ones with 250–425 μm and 710–1000 μm pores. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 64A: 291–300, 2003
Bone formation on two‐dimensional poly(DL‐lactide‐co‐glycolide) (PLGA) films and three‐dimensional PLGA tissue engineering scaffolds in vitro
Authors: Karp Jeffrey M. , Shoichet Molly S. , Davies John E. 
Published: January 2003

AbstractFor some bone tissue engineering strategies, direct contact of newly synthesized bone with a scaffold is important for structural continuity and stability at the scaffold/bone interface. Thus, as the polymer degrades, the support function of the scaffold could be adopted by the developing bone structure. This study was designed to determine whether poly(DL‐lactide‐co‐glycolide) with a comonomer ratio of 75:25 supports bone apposition in vitro. Osteogenic cells derived from rat bone marrow cells were cultured for 2 weeks on polymeric two‐dimensional films and three‐dimensional tissue engineering scaffolds. Bacteriological grade polystyrene and tissue culture polystyrene dishes served as negative and positive controls for interfacial bone deposition, respectively. The surfaces of the prepared substrates were characterized by X‐ray photoelectron spectroscopy, dynamic water contact angle, scanning electron microscopy, and atomic force microscopy. After cell culture, the elaborated matrix was examined using scanning electron microscopy, transmission electron microscopy, and energy dispersive spectroscopy. The results show that poly(DL‐lactide‐co‐glycolide) supports appositional bone growth on both two‐dimensional films and three‐dimensional scaffolds, including the formation of a mineralized cement line matrix. Furthermore, surface topographical features are not required for the adherence of the cement line matrix to the polymer. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 64A: 388–396, 2003
Surface‐dependent conformations of human plasma fibronectin adsorbed to silica, mica, and hydrophobic surfaces, studied with use of Atomic Force Microscopy
Authors: Bergkvist Magnus , Carlsson Jan , Oscarsson Sven 
Published: January 2003

AbstractHuman plasma fibronectin (Fn) is a large flexible protein stabilized by intermolecular ionic interactions forming a compact structure. On altering solution conditions, the structure can revert to a more expanded state, thereby exposing previously hidden domains (e.g., cell‐binding sites). Electron microscopy images of Fn air‐sprayed onto mica surfaces show elongated protein structures, indicating a surface‐induced structural change. This makes it interesting to investigate the influence of surface properties on the structure of adsorbed Fn. We have used intermittent‐contact Atomic Force Microscopy to investigate the structure of Fn adsorbed onto mica, silica, and methylated silica surfaces. We observed that on silica surfaces, which is hydrophilic, most (70%) of the molecules had an elongated structure with partial intramolecular chain interactions, compare to molecules adsorbed on hydrophobic, methylated surfaces, where a compact structure predominated (70%). On mica surfaces, both compact and elongated protein structures were observed, with a slight preference for the elongated form (53%). Results show that surface physical properties influence the molecular structure of fibronectin on adsorption, which could provide useful information in understanding surface‐induced in vivo responses. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 64A: 349–356, 2003
Hydrogels based on poly(ethylene oxide) and poly(tetramethylene oxide) or poly(dimethyl siloxane). III. In vivo biocompatibility and biostability
Authors: Hyung Park Jae , Bae You Han 
Published: January 2003

AbstractTo investigate the effects of polymer chemistry and topology (linear or graft copolymer) on in vivo biocompatibility and biostability based on cage implant system, various hydrogels, composed of short hydrophilic [polyethylene oxide (PEO)] and hydrophobic block, were prepared by polycondensation reaction. Poly(tetramethylene oxide) (PTMO) or poly(dimethyl siloxane) (PDMS) was chosen as a hydrophobic block because of their wide utilization as a biomaterial. By using the specimens retrieved from rats killed after 1, 2, 3, 5, and 7 weeks' implantation, cellular and material responses were assessed. Most hydrogels showed a comparable value of macrophage density to Pellethane®, control polymer, whereas they did significantly lower foreign body giant cell (FBGC) density and coverage because of the presence of PEO. However, PEO block length and polymer topology did not affect macrophage adhesion and FBGC formation in our polymer composition. The hydrogel based on PDMS alone showed significantly lower macrophage density and FBGC density than Pellethane®, indicating that PDMS plays a role in inhibiting cellular adhesion. The results obtained from gel permeation chromatography curve and Fourier transform infrared spectra exhibited that all the polymers were susceptible to oxidative degradation in vivo. Although Pellethane® revealed surface degradation by 5 weeks in vivo, hydrogels showed rapid degradation in the bulk within 2 weeks because of the penetration of oxidative chemicals released from phagocytic cells into PEO domain of phase‐separated hydrogels. The more significant degradation was observed in the hydrogels with longer PEO block and PTMO as a hydrophobic block instead of PDMS. It was evident that the minor degradation could be achieved by grafting PEO and adopting PDMS as a hydrophobic block in the hydrogel. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 64A: 309–319, 2003
In vivo leukocyte cytokine mRNA responses to biomaterials are dependent on surface chemistry
Authors: Brodbeck William G. , Voskerician Gabriela , Ziats Nicholas P. , Nakayama Yasuhide , Matsuda Takehisa , Anderson James M. 
Published: January 2003

AbstractAn in vivo mouse cage implant system was used to determine whether leukocyte cytokine mRNA responses to implanted biomaterials were dependent on surface chemistry. Surfaces displaying various chemistries (hydrophobic, hydrophilic, anionic, and cationic) were placed into stainless steel cages and implanted subcutaneously. Semiquantitative RT‐PCR analyses revealed that hydrophilic surfaces showed a decreased expression of proinflammatory cytokines, IL‐6 and IL‐8, and pro‐wound healing cytokines, IL‐10 and TGF‐β by adherent cells, and mRNA levels of the proinflammatory cytokine, IL‐1β, and the pro‐wound healing cytokine IL‐13 were decreased in surrounding, exudate cells. Cytokine responses by adherent and exudate cells to hydrophobic, anionic and cationic surfaces were similar and indicative of a strong inflammatory response at the earliest time point followed by a wound healing response at later time points. However, no differences in the types or levels of exudate cells for any of the surfaces or the empty cage at each of the respective time points were observed, indicating their respective biocompatibility. These studies identify hydrophilic surface chemistries as having significant effects on leukocyte cytokine responses in vivo by decreasing the expression of inflammatory and wound healing cytokines by inflammatory cells adherent to the biomaterial as well as present in the surrounding exudate. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 64A: 320–329, 2003