bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dry mechanochemical synthesis of hydroxyapatites from dicalcium phosphate dihydrate and calcium oxide: A kinetic study
Authors: Briak‐BenAbdeslam Hassane El , Mochales Carolina , Ginebra Maria Pau , Nurit Josiane , Planell Josep A. , Boudeville Philippe 
Published: November 2003

AbstractCalcium phosphate ceramics have been used successfully as synthetic bone substitutes in orthopedics, dentistry, and maxillofacial surgery. One way of preparing these ceramics is the sintering of a calcium‐deficient hydroxyapatite (CDHA), which can be obtained in different ways. Mechanochemistry is one possible means of synthesizing CDHA, with an expected molar calcium‐to‐phosphate (Ca/P) ratio ± 0.005. The grinding can be carried out under dry or wet conditions. To optimize the experimental conditions of CDHA preparation by dry mechanosynthesis and for a better understanding of the DCPD/CaO mechanochemical reaction, we performed a kinetic study in which some of the experimental parameters were varied. Carried out with two different vertical rotating ball mills, this kinetic study showed that (1) experiments are reproducible and give as a final product a hydroxyapatite powder, formed of nano‐sized crystals of around 20 nm, with a controlled Ca/P ratio; (2) the time for complete disappearance of DCPD and the time for complete reaction are in direct proportion to the mass of the ground powder; but (3) the time for complete disappearance of DCPD is independent of the Ca/P ratio while the time for complete reaction increases exponentially with the Ca/P ratio; and (4) the time for complete disappearance of DCPD corresponds to the time for complete reaction solely for Ca/P = 1.5. These observations suggest a reaction mechanism in two well differentiated stages: (First stage) CaO reacts with DCPD to give first an amorphous calcium phosphate (ACP) with a low Ca/P ratio that transforms into CDHA when its Ca/P ratio reaches 1.5. At the same time, CaO is hydrated into Ca(OH)2 by the water produced by the reaction. (Second stage) If the Ca/P > 1.5 in the initial mixture, the excess Ca(OH)2 is added to CDHA 1.5 by reacting with the HPO4 group of CDHA until its Ca/P ratio reaches the expected value. The slower the reaction, the higher the Ca/P in the initial mixture. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 927–937, 2003
Adhesion and growth of human Schwann cells on trimethylene carbonate (co)polymers
Authors: Pêgo Ana Paula , Vleggeert‐Lankamp Carmen L. A. M. , Deenen Marga , Lakke Egbert A. J. F. , Grijpma Dirk W. , Poot André A. , Marani Enrico , Feijen Jan 
Published: November 2003

AbstractSeeding of artificial nerve grafts with Schwann cells is a promising strategy for bridging large nerve defects. The aim of the present study was to evaluate the adhesion and growth of human Schwann cells (HSCs) on 1,3‐trimethylene carbonate (TMC) and ϵ‐caprolactone copolymers, with the final goal of using these materials in the development of an artificial nerve graft. The adhesion, proliferation, and morphology of HSCs on copolymers containing 10 and 82 mol % of TMC and on the parent homopolymers were investigated. HSCs adhered faster and in greater numbers on the copolymer with 82 mol % of TMC and on the TMC homopolymer compared with the other (co)polymers. On all polymer films, cell adhesion was lower than on gelatin (positive control). Despite differences in cell adhesion, cells displayed exponential growth on all tested surfaces, with similar growth rates. Cell numbers doubled approximately every 3 days on all substrates. When the polymer films were coated with fibronectin, no significant differences in cell adhesion and proliferation were observed between coated polymer surfaces and gelatin. The results indicate that all tested materials support the adhesion and proliferation of HSCs and can in principle be used for the preparation of flexible and slowly degrading nerve guides. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 876–885, 2003
In vivo mechanisms of hydroxyapatite ceramic degradation by osteoclasts: Fine structural microscopy
Authors: Wenisch S. , Stahl J.‐P. , Horas U. , Heiss C. , Kilian O. , Trinkaus K. , Hild A. , Schnettler R. 
Published: November 2003

AbstractIn the present study the in vivo mechanism of calcium‐phosphate (CaP) ceramic degradation has been investigated by means of transmission electron microscopy. The results revealed osteoclast‐mediated degradation of hydroxyapatite ceramic implanted into sheep bone by simultaneous resorption and phagocytosis. After 6 weeks of implantation, osteoclasts were localized immediately beneath the ceramic surface. They had formed resorption lacunae and exhibited typical ultrastructural features, such as the ruffled border, the clear zone, and the dorsal microvilli. Their resorption capacity also had become evident by alterations of the electron density and the shape of the CaP crystals localized within the acidic microenvironment of the ruffled border. Moreover, the osteoclasts simultaneously were capable of phagocytosing the resorbed CaP crystals. The formation of endophagosomes was performed (1) by the uptake of particles into large intracellular vacuoles, which were generated by deep invagination of the membranes of the osteoclastic ruffled border, and (2) by the encircling of particles due to the development of pseudopodia‐like plasmaprotrusions of the ruffled border. The formation of endophagosomes was followed by the in situ fragmentation of the inclusion material, which subsequently was released into the extracellular space and phagocytosed by macrophages. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 713–718, 2003
Effect of silicon rubber crosslink density on fibroblast cell behavior in vitro
Authors: Mirzadeh Hamid , Shokrolahi Fateme , Daliri Morteza 
Published: November 2003

AbstractIn this study, samples of poly(dimethylsiloxane) (PDMS) with different crosslink densities were prepared in order to produce samples with different crosslink density and, subsequently, different molecular mobilities. Crosslink density and chain mobility changes in PDMS networks were determined using differential scanning calorimetery and dynamic mechanical thermal analysis, respectively. Surface roughness was studied by scanning electron microscopy (SEM). To evaluate biocompatibility, mouse fibroblast L‐929 cells were cultured onto different samples, and their numbers and growth behaviors were investigated by optical microscopy. The results showed that crosslink density and, consequently, molecular mobility cause changes in cell behavior. Moreover, we found that there is an optimum molecular mobility for PDMS at which the number and the surface areas of cells show the best cell attachment and proliferation. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 727–732, 2003
Atomic force microscopy and nanoindentation characterization of human lamellar bone prepared by microtome sectioning and mechanical polishing technique
Authors: Xu J. , Rho J. Y. , Mishra S. R. , Fan Z. 
Published: November 2003

AbstractSurface topography, microstructure, and micromechanical properties of human lamellar bone were characterized by atomic force microscopy and nanoindentation. The lamellar bone surfaces were prepared by two different methods: microtome sectioning and mechanical polishing. The lamellar bone surfaces prepared by mechanical polishing revealed that thin lamellae formed depressions approximately 200 nm deep, whereas the surfaces prepared by microtome sectioning were flat. Atomic force microscopy surface topographic images at higher magnification showed differences between thick and thin lamellae in polished samples, but these differences were less pronounced in microtomed samples. Roughness measurements confirmed that there was a significant difference between thick (21.0 nm) and thin lamellae (8.3 nm) in polished samples (p < 0.001). The difference in surface roughness between thick (13.9 nm) and thin lamellae (12.7 nm) in microtomed sample was statistically insignificant (p = 0.74). Higher elastic modulus values were observed for thick lamella in microtomed samples compared with that of thin lamellae, whereas measured elastic modulus differences between thick and thin lamellae in polished samples were found to be statistically insignificant. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 719–726, 2003
Characterization of the mechanical properties of demineralized bone
Authors: Summitt Matthew C. , Reisinger Kim D. 
Published: November 2003

AbstractDemineralized bone has had limited use as a medical implant, although, recently Jackson et al. (Am J Sports Med 1996;24(4):405–414) examined using demineralized bone as an anterior cruciate ligament (ACL) replacement and found that within 1 year the demineralized bone had remodeled from a haversian system (bone‐like) into a ligament‐like structure. Little research has been done to characterize the mechanical properties of demineralized bone and examine its potential as a ligament replacement. This research examined the mechanical properties of demineralized bone as a function of acid saturation time and methods of processing and sterilization using specimens from various anatomic locations. Bone specimens were manufactured from the tibia, metatarsus, femur, radius, and humerus of bovine bone. Tensile strength, strain, and modulus of elasticity were examined for various acid saturation times and sterilization treatments. Additionally, viscoelastic properties, creep and stress relaxation, and fatigue properties were examined. The findings indicate that completely demineralized bone has mechanical properties similar to the ACL and, therefore, has increased likelihood for success in ACL reconstruction surgery. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 742–750, 2003
Influence of the in vitro culture period on the in vivo performance of cell/titanium bone tissue‐engineered constructs using a rat cranial critical size defect model
Authors: Sikavitsas Vassilios I. , Dolder Juliette van den , Bancroft Gregory N. , Jansen John A. , Mikos Antonios G. 
Published: November 2003

AbstractThe aim of this study was to investigate the in vivo performance in bone‐regenerating capability of cell/scaffold constructs implanted into an orthotopic site. Bone marrow stromal osteoblasts were seeded on titanium fiber mesh scaffolds using a cell suspension (5 × 105 cells per scaffold) and cultured for 1, 4, and 8 days under either static or flow perfusion conditions forming six different treatment groups. A total of 16 constructs from each one of the six treatment groups were then implanted into an 8‐mm critical size calvarial defect created in the cranium of adult syngeneic male Fisher rats. Half of the constructs from each group were retrieved 7 days postimplantation, and the other half of the constructs were retrieved 30 days postimplantation and examined for new bone formation and tissue response. Constructs retrieved 7 days postimplantation were filled with fibrous tissue and capillaries, but no bone formation was observed in any of the six treatment groups. Constructs retrieved 30 days postimplantation showed bone formation (at least 7 out of 8 constructs in all treatment groups). Titanium fiber meshes seeded with bone marrow stromal osteoblasts and cultured for 1 day under flow perfusion conditions before implantation appeared to give the highest percentage of bone formation per implant (64 ± 17%). They also showed the highest ratio of critical size cranial defects that resulted in union of the defect 30 days postimplantation (7 out of 8) together with the constructs cultured for 1 day under static conditions before implantation. There were no significant differences between the different treatment groups; this finding is most likely due to the large variability of the results and the small number of animals per group. However, these results show that titanium fiber mesh scaffolds loaded with bone marrow stromal osteoblasts can have osteoinductive properties when implanted in an orthotopic site. They also indicate the importance of the stage of the osteoblastic differentiation and the quality of the in vitro generated extracellular matrix in the observed osteoinductive potential. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 944–951, 2003
Evaluation of a galactose‐carrying gelatin sponge for hepatocytes culture and transplantation
Authors: Hong Sung Ran , Lee Young Moo , Akaike Toshihiro 
Published: November 2003

AbstractThis study proposes a new three‐dimensional culture of mouse hepatocytes in a porous galactose‐carrying modified gelatin sponge matrix. The modification of gelatin using galactose residues significantly increased the attachment of hepatocytes on the substrate. A modified gelatin sponge with lactobionic acid (MGLA) was prepared to increase the specific interaction between the hepatocytes and the matrix. Hepatocytes cultured in a three‐dimensional MGLA sponge released much less lactate dehydrogenase than those cultured on a collagen Type I‐coated monolayer. Moreover, the survival rate of hepatocytes cultured on an MGLA sponge was longer than the survival rate of hepatocytes cultured on a collagen Type I‐coated monolayer. Hepatic specific metabolic functions, namely, the secretion of serum albumin and the synthesis of urea, were well maintained and promoted by spheroidal hepatocytes formed in the MGLA sponge. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 733–741, 2003
Nonadhesive nanotopography: Fibroblast response to poly(n‐butyl methacrylate)‐poly(styrene) demixed surface features
Authors: Dalby M. J. , Riehle M. O. , Johnstone H. J. H. , Affrossman S. , Curtis A. S. G. 
Published: November 2003

AbstractIt is becoming clear that cells do not only respond to micrometric scale topography, but may also respond to topography at the nanometric scale. Nano‐fabrication methods such as electron beam lithography are, however, expensive and time consuming. Polymer demixing of poly(styrene) and poly(4‐bromostyrene) has been found to produce nano‐scale islands of reproducible height, and the islands have been previously shown to effect cell events such as adhesion, spreading, proliferation, and differentiation. This study uses demixed poly(styrene) and poly(n‐butyl methacrylate) to produce nano‐islands with closer packing and narrower widths compared with those previously studied. Observations have been made of morphological and cytoskeletal changes in human fibroblasts interacting with 10‐ and 50‐nm‐high islands. The methods used included scanning electron microscopy, fluorescent microscopy, and optical microscopy. The results indicated that the cells do not respond differently to the 10‐nm islands compared with planar samples but, in contrast, the 50‐nm islands are nonadhesive. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 1025–1032, 2003
Hydroxyapatite whiskers provide improved mechanical properties in reinforced polymer composites
Authors: Roeder Ryan K. , Sproul Michael M. , Turner Charles H. 
Published: November 2003

AbstractSynthetic hydroxyapatite (HA) whiskers have been utilized as a new, biocompatible reinforcement for orthopedic biomaterials. High‐density polyethylene (HDPE) was reinforced with either the synthesized HA whiskers or a commercially available spherical HA powder using a novel powder processing technique that facilitated uniform dispersion of the reinforcements in the matrix prior to compression molding. Composites were processed for up to 60 vol % HA whiskers and up to 50 vol % spherical HA. The mechanical properties of the new composite biomaterials were examined by uniaxial tensile tests. As expected, increased volume fraction of either reinforcement type over 0–50 vol % resulted in increased elastic modulus, a maximum in ultimate tensile stress, and decreased work to failure. Composites reinforced with HA whiskers had higher elastic modulus, ultimate tensile strength, and work to failure relative to composites reinforced with spherical HA. Thus, HA whisker‐reinforced HDPE composites possessed improved mechanical properties over those reinforced with spherical HA. HA whisker‐reinforced composites were anisotropic due to alignment of the whiskers in the matrix during processing. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 801–812, 2003
Effect of hydrophilicity and agmatine modification on degradation of poly(propylene fumarate‐co‐ethylene glycol) hydrogels
Authors: Tanahashi Kazuhiro , Mikos Antonios G. 
Published: November 2003

AbstractWe synthesized positively charged biodegradable hydrogels with different poly(propylene fumarate‐co‐ethylene glycol) [P(PF‐co‐EG)] block copolymers and agmatine‐modified poly(ethylene glycol)‐tethered fumarate [Agm‐PEGF] by radical crosslinking and investigated the effect of copolymer composition and agmatine modification on their degradation. Hydrogels were incubated in phosphate‐buffered saline (PBS) at 37°C with periodic PBS changes. All hydrogels experienced a slight mass loss over 4 weeks, ranging from 10–20%. Hydrogels with a molar ratio of ethylene glycol repeating units to propylene fumarate repeating units (EG/PF) of 9.3 degraded faster than hydrogels with an EG/PF ratio of 0.6. Agmatine‐modified hydrogels degraded faster than unmodified hydrogels. The weight swelling ratio of the hydrogels at pH 7 increased over 4 weeks while increases in the EG/PF ratio and agmatine modification showed greater swelling. After 2 weeks, degraded hydrogels swollen at pH 3 demonstrated significantly lower weight swelling ratios than at pH 5, 7, and 9. Our results suggest that the hydrophilicity of the P(PF‐co‐EG) copolymer and agmatine modification have a small effect on the degradation of P(PF‐co‐EG) hydrogels. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 1148–1154, 2003
Biomedical application of a superabsorbent hydrogel for body water elimination in the treatment of edemas
Authors: Sannino A. , Esposito A. , Rosa A. De , Cozzolino A. , Ambrosio L. , Nicolais L. 
Published: November 2003

AbstractA novel system of body water elimination to be used for the treatment of edemas, based on superabsorbent cellulose derivatives able to absorb large amounts of water and water solutions, has been investigated. Hydrogels have been synthesized starting from water solutions of carboxymethylcellulose sodium salt and hydroxyethylcellulose, chemically crosslinked with divinylsulphone. Polyelectrolyte hydrogels displayed high sensitivity in sorption capacity to variations of the ionic strength and pH of the external solution, which is a key parameter for the application under investigation. Further, swelling properties have been modulated acting on the degree of crosslinking of the macromolecular network, and a direct method for the measurement of this parameter based on NMR solid‐state analysis has been provided. The hydrogel biocompatibility has been studied in terms of its capacity either to induce nitric oxide and lactate dehydrogenase release by macrophages or influence their viability. The eventual release of toxic substances from the hydrogel was also investigated using Swiss 3T3 fibroblasts. The results obtained from the biocompatibility studies carried out in this work are consistent with the hypothesis that this gel may represent an alternative to diuretic therapies in those pathologic conditions in which edemas occur. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 1016–1024, 2003
Alternating gene expression in fibroblasts adhering to multilayers of chitosan and dextran sulfate
Authors: Serizawa Takeshi , Yamaguchi Miyuki , Kishida Akio , Akashi Mitsuru 
Published: November 2003

AbstractThe alternating compatibility of fibroblast cells adhering to multilayers of chitosan and dextran sulfate (Dex) on a substrate was analyzed at the gene expression level. A greater number of round‐shaped cells adhered to the films with an outermost surface composed of Dex, although the total number of adherent cells was independent of the film surface. Greater expression of heat‐shock protein 70B mRNA was demonstrated in cells adhering to films with the Dex surface. It was found that analysis of gene expression was a powerful tool for evaluating the bioactivity of multilayers. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 1060–1063, 2003
Plasma‐enhanced chemical vapor deposited silicon carbide as an implantable dielectric coating
Authors: Cogan Stuart F. , Edell David J. , Guzelian Andrew A. , Ping Liu Ying , Edell Robyn 
Published: November 2003

AbstractAmorphous silicon carbide (a‐SiC) films, deposited by plasma‐enhanced chemical vapor deposition (PECVD), have been evaluated as insulating coatings for implantable microelectrodes. The a‐SiC was deposited on platinum or iridium wire for measurement of electrical leakage through the coating in phosphate‐buffered saline (PBS, pH 7.4). Low leakage currents of <10−11 A were observed over a ±5‐V bias. The electronic resistivity of a‐SiC was 3 × 1013 Ω‐cm. Dissolution rates of a‐SiC in PBS at 37 and 90°C were determined from changes in infrared absorption band intensities and compared with those of silicon nitride formed by low‐pressure chemical vapor deposition (LPCVD). Dissolution rates of LPCVD silicon nitride were 2 nm/h and 0.4 nm/day at 90 and 37°C, respectively, while a‐SiC had a dissolution rate of 0.1 nm/h at 90°C and no measurable dissolution at 37°C. Biocompatibility was assessed by implanting a‐SiC‐coated quartz discs in the subcutaneous space of the New Zealand White rabbit. Histological evaluation showed no chronic inflammatory response and capsule thickness was comparable to silicone or uncoated quartz controls. Amorphous SiC‐coated microelectrodes were implanted in the parietal cortex for periods up to 150 days and the cortical response evaluated by histological evaluation of neuronal viability at the implant site. The a‐SiC was more stable in physiological saline than LPCVD Si3N4 and well tolerated in the cortex. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 856–867, 2003
Preparation and characterization of macroporous chitosan–gelatin/β‐tricalcium phosphate composite scaffolds for bone tissue engineering
Authors: Yin Yuji , Ye Fen , Cui Junfeng , Zhang Fujiang , Li Xiulan , Yao Kangde 
Published: November 2003

AbstractA biodegradable composite scaffold was developed using β‐tricalcium phosphate (β‐TCP) with chitosan (CS) and gelatin (Gel) in the form of a hybrid polymer network (HPN) via co‐crosslinking with glutaraldehyde. Various types of scaffolds were prepared by freezing and lyophilizing. These scaffolds were characterized by Fourier transform infrared, X‐ray diffractometer, and scanning electron microscopy. The macroporous composite scaffolds exhibited different pore structures. Compressive properties were improved, especially compressive modulus from 3.9–10.9 MPa. Biocompatibility was evaluated subcutaneously on rabbits. A mild inflammatory response was observed over 12 weeks. The results suggest that the scaffolds can be utilized in nonloading bone regeneration. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 844–855, 2003