bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bone formation by rat bone marrow cells cultured on titanium fiber mesh: Effect of in vitro culture time
Authors: van den Dolder Juliette , Vehof Johan W. M. , Spauwen Paul H. M. , Jansen John A. 
Published: September 2002

AbstractThe objective of this study was to examine the effect of cell culture time on bone formation by rat bone marrow cells seeded in titanium fiber mesh. As a seeding technique, a high cell suspension was used (3 × 106 cells/mL). Therefore, 30 meshes were repeatedly rotated in a 10 mL tube (containing 30 × 106 cells) on a rotation plate (2 rpm) for 3 h. Osteogenic cells were cultured for 1, 4, and 8 days on titanium fiber mesh and finally implanted subcutaneously in rats. Meshes without cells were also implanted subcutaneously in rats. DNA and scanning electron microscopy (SEM) analyses and calcium measurements determined cellular proliferation and differentiation during the in vitro incubation period of the mesh implants. Four weeks after implant insertion, the animals were sacrificed. The implants, with their surrounding tissue, were retrieved and prepared for histologic evaluation and calcium measurements. DNA analysis of the in vitro experiment showed a lag phase from day 1 through day 4, but a 42% increase in DNA between days 4 and 8. SEM and calcium measurements indicated an increase in calcium from day 1 to day 4, yet only a small but significant increase from days 4 to 8. Histologic analysis demonstrated that bone was formed in all day 1 and day 4 implants, and that the bone‐like tissue was present uniformly through the meshes. The bony tissue was morphologically characterized by osteocytes embedded in a mineralized matrix, with a layer of osteoid and osteoblasts at the surface. The day 8 implants showed only calcium phosphate deposition in the titanium fiber mesh. Calcium measurements of the implants revealed that calcification in day 1 implants was significantly higher (p < 0.05) compared to day 4 and day 8 implants. No significant difference in calcium content existed between day 4 and day 8 implants. On the basis of our results, we conclude that 1) bone formation was generated more effectively in osteogenic cells by a short culture time after seeding in titanium fiber mesh; 2) dynamic cell seeding is probably more effective than static cell seeding; and 3) selection of the right cells from the heterogenous bone marrow population remains a problem. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 62: 350–358, 2002
Carbon dioxide extraction of residual chloroform from biodegradable polymers
Authors: Koegler Wendy S. , Patrick Carmen , Cima Michael J. , Griffith Linda G. 
Published: September 2002

AbstractBiodegradable polymeric devices for drug delivery and tissue engineering are often fabricated with the use of organic solvents and may still contain significant amounts of solvent (> 1 wt%) even after aggressive vacuum drying. This excess solvent can interfere with tissue response and the mechanical properties of the devices. The aim of this article is to demonstrate that liquid CO2 extraction can be used to reduce residual solvent in dense poly(L‐lactide‐co‐glycolide) devices to 50 ppm relatively quickly and with minimal changes in architecture under some conditions. Two liquid CO2 extraction systems were developed to examine the removal of residual solvents from bar‐shaped PLGA devices: (1) a low‐pressure (1400 psi) batch system, and (2) a high‐pressure (5000 psi) continuous‐flow system. Eight hours of extraction in the high‐pressure system reduced residual chloroform in 3 mm thick bars below the 50‐ppm target. A simple Fickian diffusion model was fit to the extraction results. Diffusion coefficients ranged from 1.10×10−6 cm2/s to 2.64×10−6 cm2/s. The model predicts that ∼1 h is needed to dry 1‐mm bars to chloroform levels below 50 ppm, and 7 h are needed for 3 mm thick bars. The micro‐ and macroarchitectures of porous PLGA scaffolds created by particulate leaching were not significantly altered by CO2 drying if the salt used to make the pores was not removed before drying. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res (Appl Biomater) 63: 567–576, 2002
Novel approach for achieving double‐layered cell sheets co‐culture: overlaying endothelial cell sheets onto monolayer hepatocytes utilizing temperature‐responsive culture dishes
Authors: Harimoto Masami , Yamato Masayuki , Hirose Motohiro , Takahashi Chie , Isoi Yuki , Kikuchi Akihiko , Okano Teruo 
Published: September 2002

AbstractConfluent human aortic endothelial cells (HAECs) cultured on thermo‐responsive culture dish grafted with poly (N‐isopropylacrylamide) were recovered as a contiguous cell sheet. The double‐layered co‐culture was achieved by placing the recovered HAEC sheet onto the rat hepatocyte layer directly. The double‐layered structure of HAEC and hepatocytes remained in tight contact during culture. Hepatocytes in the layered co‐culture system with the HAEC sheet maintained the differentiated cell shape and the albumin expression for over 41 days of culture, whereas the functions disappeared within 10 days of culture in control hepatocytes without the HAEC sheet. The layered co‐culture of hepatocytes and the HAEC sheets, which allows for the expression of differentiated functions of hepatocyte continuously, such as liver lobule, offers a major advancement in liver tissue engineering. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 62: 464–470, 2002
Characterization of cartilagenous tissue formed on calcium polyphosphate substratesin vitro
Authors: Waldman Stephen D. , Grynpas Marc D. , Pilliar Robert M. , Kandel Rita A. 
Published: September 2002

AbstractSuccessful joint resurfacing by tissue‐engineered cartilage has been limited, in part, by an inability to secure the implant to bone. To overcome this, we have developed the methodology to form a cartilage implantin vitroconsisting of a layer of cartilagenous tissue overlying a porous, biodegradable calcium polyphosphate (CPP) substrate. As bone will grow into the CPP after implantation, it will result in anchorage of the cartilage. In this study, the cartilagenous tissue formedin vitroafter 8 weeks in culture was characterized and compared to native articular cartilage. Light microscopic examination of histological sections showed that there was a continuous layer of cartilagenous tissue on, and integrated with the subsurface of, the CPP substrate. Thein vitro‐formed tissue achieved a similar thickness to native articular cartilage (mean ± SEM:in vitro= 0.94 ± 0.03 mm;ex vivo= 1.03 ± 0.01 mm). The cells in thein vitro‐formed tissue synthesized large proteoglycans (Kav ± SEM:in vitro= 0.27 ± 0.01;ex vivo= 0.27 ± 0.01) and type II collagen similar to the chondrocytes in theex‐vivocartilage. Thein vitro‐formed tissue had a similar amount of proteoglycan (GAG μg/mg dry wt.:in vitro= 198 ± 10;ex vivo= 201 ± 13) but less collagen than the native cartilage (hydroxyproline μg/mg dry wt.:in vitro= 21 ± 1;ex vivo= 70 ± 8). Thein vitro‐formed tissue had only about 3% of the load‐bearing capacity and stiffness of the native articular cartilage, determined from unconfined mechanical compression testing. Although low, this was within the range of properties reported by others for tissue‐engineered cartilage. It is possible that the limited load‐bearing capacity is the result of the low collagen content and further studies are required to identify the conditions that will increase collagen synthesis. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 62:323–330, 2002
Collagen fiber disruption occurs independent of calcification in clinically explanted bioprosthetic heart valves
Authors: Sacks Michael S. , Schoen Frederick J. 
Published: September 2002

AbstractThe durability of bioprosthetic heart valves (BHV) is severely limited by tissue deterioration, manifested as calcification and mechanical damage to the extracellular matrix. Extensive research on mineralization mechanisms has led to prevention strategies, but little work has been done on understanding the mechanisms of noncalcific matrix damage. The present study tested the hypothesis that calcification‐independent damage to the valvular structural matrix mediated by mechanical factors occurs in clinical implants and could contribute to porcine aortic BHV structural failure. We correlated quantitative assessment of collagen fiber orientation and structural integrity by small angle light scattering (SALS) with morphologic analysis in 14 porcine aortic valve bioprostheses removed from patients for structural deterioration following 5–20 years of function. Calcification of the explants varied from 0 (none) to 1+ (minimal) to 4+ (extensive), as assessed radiographically. SALS tests were performed over entire excised cusps using a 0.254‐mm spaced grid, and the resultant structural information used to generate maps of the local collagen fiber damage that were compared with sites of calcific deposits. All 42 cusps showed clear evidence of substantial noncalcific structural damage. In 29 cusps that were calcified, structural damage was consistently spatially distinct from the calcification deposits, generally in a distribution similar to that noted in porcine BHV subjected to in vitro durability testing. Our results suggest a mechanism of noncalcific degradation dependent on cuspal mechanics that could contribute to porcine aortic BHV failure. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 62: 359–371, 2002
Liquid acrylate‐endcapped biodegradable poly(ϵ‐caprolactone‐co‐trimethylene carbonate). I. Preparation and visible light‐induced photocuring characteristics
Authors: Mizutani Manabu , Matsuda Takehisa 
Published: September 2002

AbstractPhotocurable liquid biodegradable copolymers were prepared by ring‐opening copolymerization of ϵ‐caprolactone (CL) and trimethylene carbonate (TMC) in the presence of a multifunctional hydroxyl group‐bearing substance (di‐, tri‐, and tetra‐functional alcohol and poly(ethylene glycol) (PEG) and its four‐branched derivative) as an initiator and subsequent endcapping with acryloyl chloride at their hydroxyl terminals. These multifunctional, viscous liquid copolymers (molecular weights; approximately 2 × 103 to 7 × 103 g/mol) were converted to crosslinked solids by visible‐light irradiation in the presence of camphorquinone as an initiator. The photocuring rate of these copolymers was enhanced by both higher functionality and lower molecule weight of the copolymers used. The photocuring rate depended on the amount of reducing agent (methacrylic acid 2‐dimethylaminoethyl ester). Upon immersion in a phosphate buffer solution (pH 7.4), hydrolysis occurred preferentially on the surface except for photocured PEG‐based copolymers that were degraded faster via both surface erosion and bulk degradation than low molecular weight alcohols‐based copolymers. Cylindrical photocured constructs prepared by photoirradiation to the whole body in a mold filled with the liquid copolymer was demonstrated as an example of shape fabrication of biodegradable biomedical devices. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 62: 387–394, 2002
Liquid acrylate‐endcapped biodegradable poly(ϵ‐caprolactone‐co‐trimethylene carbonate). II. Computer‐aided stereolithographic microarchitectural surface photoconstructs
Authors: Matsuda Takehisa , Mizutani Manabu 
Published: September 2002

AbstractAdvanced micromedical devices may require computer‐aided photofabrication, by which microarchitectural surface design and entire macroshaped body design are feasible. Liquid acrylate‐endcapped poly(ϵ‐caprolactone‐co‐trimethylene carbonate)s, poly(CL/TMC)s, prepared using trimethylene glycol (TMG) or poly(ethylene glycol) (PEG) as an initiator and an acrylate group for subsequent terminal capping, were used as photocurable copolymers. The stereolithographically microarchitectured photoconstructs were prepared using a custom‐designed apparatus with a moving ultraviolet (UV) light pen driven by a computer‐assisted design program. The prepared photoconstructs included microneedles, a microcylinder and microbanks on surfaces. In vitro hydrolytic degradation proceeded with surface erosion when hydrophobic TMG‐based photocured copolymers were employed, whereas very fast degradation of hydrophilic PEG‐based photocured copolymers probably via concerted actions of surface erosion and bulk degradation was observed. In vivo hydrolytic behavior upon subcutaneous implantation in rats indicated that surface erosion proceeded for TMG‐based photoconstructs. Anti‐inflammatory drug (indomethacin) loading into microneedle‐structured surfaces minimized inflammatory reactions. The possible biomedical microarchitectural three dimensinal in biomedical application photoconstructs was discussed. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 62: 395–403, 2002
Key issues involved with the use of miniature specimens in the characterization of the mechanical behavior of polymeric biomaterials—A review
Authors: Lewis Gladius 
Published: September 2002

AbstractThis article is arranged in three parts. In the first, a brief history of the use of miniature specimens for characterizing the mechanical behavior of materials in general is given. In the second part, several trends in literature reports of small punch and small shear punch tests of ultra‐high‐molecular‐weight polyethylene and acrylic bone cement specimens are examined critically. In this exercise, special attention is paid to one test metric; namely, the work to failure [which is the area under the punch load (P) versus punch displacement (Δ) plot up to the failure point]. In the third part of the article, seven key issues in this field are discussed. In each case, the gaps in the current knowledge base are pointed out. Among those issues are determination of sensitivity of test results to test variables, development of methods for converting P−Δ results to bulk material properties, and constitutive modeling of the mechanical behavior of a polymeric biomaterial, under both small punch and small shear punch loading. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res (Appl Biomater) 63: 455–466, 2002
Biomembranes enriched with TGFβ1 favor bone matrix protein expression by human osteoblasts in vitro
Authors: Lilli C. , Marinucci L. , Stabellini G. , Belcastro S. , Becchetti E. , Balducci C. , Staffolani N. , Locci P. 
Published: September 2002

AbstractThe use of growth factors in oral tissue regeneration is currently under investigation. When growth factors are combined with commercial materials, the in vitro mechanisms of action still remain unclear. The present study first evaluated the capacity of barrier membranes, used in oral surgery, to sequester TGFβ1. Resorbable HYAFF, paroguide, poly DL‐lactide and nonresorbable PTFE membranes were immersed in MEM containing 0.2 ng 125I‐TGFβ1 for different periods of time. It was found that HYAFF membrane and paroguide sequestered the most TGFβ1, which was then released in its active form (as shown by the CCL64 cell line bioassay). Untreated membranes and membranes enriched with TGFβ1 were then used as substrate for human bone cells to evaluate the synthesis of the osteoblast phenotype, as indicated by specific parameters. Results showed that membranes enriched with TGFβ1 increased alkaline phosphatase activity, collagen, and osteocalcin production more than untreated membranes. HYAFF and paroguide membranes, which sequestered the most of TGFβ1, were the most suitable for stimulating bone matrix proteins. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res (Appl Biomater) 63: 577–582, 2002
Long‐term biocompatibility of implanted polymer‐based intrafascicular electrodes
Authors: Lawrence Stephen M. , Larsen Jytte O. , Horch Kenneth W. , Riso Ron , Sinkjær Thomas 
Published: September 2002

AbstractPolymer‐based longitudinal intrafascicular electrodes (polyLIFEs) were chronically implanted into the sciatic nerve of white New Zealand rabbits (n=8) for a period of 6 months (hereafter referred to as the long‐term group). The impact of the implantation procedure, as observed 6 months post surgery, was evaluated in a sham‐treated control group (n=9). The contralateral sciatic nerve served as the control for each animal. Nerve‐fiber counts, fiber diameters, and myelin thickness were estimated at the level of the implant site, 1.5 cm proximally, and 1.5 cm distally for both nerves in sham‐treated and long‐term groups. Implantation of polyLIFEs had no significant effect on fiber counts, nerve‐fiber diameter, or myelin thickness. A slight increase in connective tissue in the vicinity of the implant site was evident in the long‐term group, including a thin but dense capsule immediately surrounding the implanted electrode. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res (Appl Biomater) 63: 501–506, 2002
Morphologic and immunohistochemical observations of tissues surrounding retrieved transvenous pacemaker leads
Authors: Esposito Marco , Kennergren Charles , Holmström Nils , Nilsson Susanne , Eckerdal Johan , Thomsen Peter 
Published: September 2002

AbstractImmunohistochemical and morphologic techniques were employed to evaluate the tissue response around chronically implanted pacing leads. Seventeen leads were retrieved from 12 patients. Leads were extracted by direct manual traction (1), extraction with sheaths and locking stylets (1), or with by a combination of mechanical tools and Excimer laser sheaths (15). Mean lead implantation time was 5.6 years (range 1–8 years). Frozen sections, 6–8 μm thick, were incubated with antibodies against HLA‐DR antigen, endothelial cells, macrophages, T cells, plasma cells, fibrinogen, and interleukin‐1β. Prominent morphologic observations were fibrous encapsulations of the leads. Immunohistochemical analysis revealed a tissue generally devoid of inflammatory and immune cells. The fibrous capsule surrounding the lead was partially or completely covered with a monolayer of CD34 expressing endothelial cells. The results from this study provide useful information in design and material selection for pacemaker leads. Endothelialization of the fibrous encapsulation indicates a functionalization of blood‐contacting surfaces around pacemaker materials, thus providing a mechanism for long‐term persistence of foreign materials in the blood. The laser method allowed an efficient extraction of pacemaker leads without damage to the studied tissues, as suggested by the presence of immunolabeled cells close to the cut surfaces. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res (Appl Biomater) 63: 548–558, 2002
Biological reactivity of zirconia–hydroxyapatite composites
Authors: Silva Viviane V. , Lameiras Fernando S. , Lobato Zélia I. P. 
Published: September 2002

AbstractMaterials and devices intended for end‐use applications as implants and medical devices must be evaluated to determine their biocompatibility potential in contact with physiological systems. The use of standard practices of biological testing provides a reasonable level of confidence concerning the response of a living organism to a given material or device, as well as guidance in selecting the proper procedures to be carried out for the screening of new or modified materials. This article presents results from cytotoxicity assays of cell culture, skin irritation, and acute toxicity by systemic and intracutaneous injections for powders, ceramic bodies, and extract liquids of hydroxyapatite (HA), calcia partially stabilized zirconia (ZO), and two types of zirconia–hydroxyapatite composites (Z4H6 and Z6H4) with potential for future use as orthopedic and dental implants. They indicate that these materials present potential for this type of application because they meet the requirements of the standard practices recommended for evaluating the biological reactivity of ATCC cell cultures (CCL1 NCTC clone 929 of mouse connective tissue and CCL 81 of monkey connective tissue) and animals (rabbit and mouse) with direct or indirect patient contact, or by the injection of specific extracts prepared from the material under test. In addition, studies involving short‐term intramuscular and long‐term implantation assays to estimate the reaction of living tissue to the composites studied, and investigations on long‐term effects that these materials can cause on the cellular metabolism, are already in progress. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res (Appl Biomater) 63: 583–590, 2002
Deconvolution of surface topology for quantification of initial wear in highly cross‐linked acetabular components for THA
Authors: Kurtz S. M. , Turner J. L. , Herr M. , Edidin A. A. 
Published: September 2002

AbstractEvaluation of the surface morphology of short‐term retrieved cross‐linked acetabular components requires differentiation between the features generated during machining and the smaller‐scale morphologies generated during the in vivo wear process. Previously, the distinction between the waviness of machining and the roughness of wear has been related to the grain size of the UHMWPE. Here a low‐frequency cutoff is proposed, based on the maximum spectral frequency of machining marks, rather than on the grain size of the bulk UHMWPE material, as a reliable method for deconvolving machining marks from in vivo wear following short‐term implantation. To this end, as‐machined articulating surfaces of conventional (GUR 1050) and two groups of highly cross‐linked UHMWPE acetabular components were examined to determine whether they exhibited a periodic surface morphology with a well‐defined spatial frequency. The surface frequency spectra revealed low‐frequency peaks associated with the machining marks, which were unique to each type of implant. Furthermore, the surface frequency spectra appeared uniform within a single group of implants. Statistically significant differences in the surface roughness and waviness were observed between the three groups of new implants. Our research suggests that machining marks can be effectively deconvolved from the articulating surface with the use of a Fourier transform algorithm with a single cutoff frequency of 0.08 1/μm, corresponding to a wavelength of 12.5 μm. The results of this study provide a unified conceptual framework for discriminating between waviness and roughness of the articulating surface for machined orthopedic components. The distinction between waviness and roughness is expected to be crucial for the comprehensive evaluation of wear surfaces after short‐term implantation, when machining marks may be partially worn away or plastically deformed in vivo. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res (Appl Biomater) 63: 492–500, 2002
Comparison of two methods to measure permeability of dentin
Authors: De La Macorra Jose C. , Escribano Nuria I. 
Published: September 2002

AbstractDentin permeability was measured alternatively with two methods: a 10‐μl capillary method with visual evaluation (PC) and a motorized automatic measuring device (Flodec, FD), both interposed in a simulated perfusion system. Eight human third molar coronal fragments were connected to systems, and their permeability to distilled water measured at 0, 5, 10, 15, 20, 25, and 29 cm H2O pressure. Resultant permeabilities (in μl/s) for both techniques were interrelated with the use of the Passing and Bablok nonparametric method, which gives information about the range of constant and proportional errors and their 95% confidence intervals (95CI). The relationship between the methods is described by the regression formula: FD = −0.0003 + 0.945·PC, with 95CI for constant (−0.0015–0.0009) and for slope (0.738–1.168), indicating that both methods are interchangeable, although not identical. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res (Appl Biomater) 63: 531–534, 2002