bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nanofabrication for micropatterned cell arrays by combining electron beam‐irradiated polymer grafting and localized laser ablation
Authors: Yamato Masayuki , Konno Chie , Koike Shunsuke , Isoi Yuki , Shimizu Tatsuya , Kikuchi Akihiko , Makino Kimiko , Okano Teruo 
Published: November 2003

AbstractMost methods reported for cell‐surface patterning are generally based on photolithography and use of silicon or glass substrates with processing analogous to semiconductor manufacturing. Herein, we report a novel method to prepare patterned plastic surfaces to achieve cell arrays by combining homogeneous polymer grafting by electron beam irradiation and localized laser ablation of the grafted polymer. Poly(N‐isopropylacrylamide) (PIPAAm) was covalently grafted to surfaces of tissue culture‐grade polystyrene dishes. Subsequent ultraviolet ArF excimer laser exposure to limited square areas (sides of 30 or 50 μm) produced patterned ablative photodecomposition of only the surface region (∼100‐nm depth). Three‐dimensional surface profiles showed that these ablated surfaces were as smooth and flat as the original tissue culture‐grade polystyrene surfaces. Time‐of‐flight secondary ion mass spectrometry analysis revealed that the ablated domains exposed basal polystyrene and were surrounded with PIPAAm‐grafted chemistry. Before cell seeding, fibronectin was adsorbed selectively onto ablated domains at 20°C, a condition in which the non‐ablated grafted PIPAAm matrix remains highly hydrated. Hepatocytes seeded specifically adhered onto the ablated domains adsorbed with fibronectin. Because PIPAAm inhibits cell adhesion and migration even at 37°C when the grafted density is >3 μg/cm2, all the cells were confined within the ablated domains. A 100‐cell domain array was achieved by this method. This surface modification technique can be utilized for fabrication of cell‐based biosensors as well as tissue‐engineered constructs. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 1065–1071, 2003
Biological response of chondrocytes cultured in three‐dimensional nanofibrous poly(ϵ‐caprolactone) scaffolds
Authors: Li Wan‐Ju , Danielson Keith G. , Alexander Peter G. , Tuan Rocky S. 
Published: November 2003

AbstractNanofibrous materials, by virtue of their morphological similarities to natural extracellular matrix, have been considered as candidate scaffolds for cell delivery in tissue‐engineering applications. In this study, we have evaluated a novel, three‐dimensional, nanofibrous poly(ϵ‐caprolactone) (PCL) scaffold composed of electrospun nanofibers for its ability to maintain chondrocytes in a mature functional state. Fetal bovine chondrocytes (FBCs), maintained in vitro between passages 2 to 6, were seeded onto three‐dimensional biodegradable PCL nanofibrous scaffolds or as monolayers on standard tissue culture polystyrene (TCPS) as a control substrate. Gene expression analysis by reverse transcription–polymerase chain reaction showed that chondrocytes seeded on the nanofibrous scaffold and maintained in serum‐free medium supplemented with ITS+, ascorbate, and dexamethasone continuously maintained their chondrocytic phenotype by expressing cartilage‐specific extracellular matrix genes, including collagen types II and IX, aggrecan, and cartilage oligomeric matrix protein. Specifically, expression of the collagen type IIB splice variant transcript, which is indicative of the mature chondrocyte phenotype, was up‐regulated. FBCs exhibited either a spindle or round shape on the nanofibrous scaffolds, in contrast to a flat, well‐spread morphology seen in monolayer cultures on TCPS. Organized actin stress fibers were only observed in the cytoplasm of cells cultured on TCPS. Histologically, nanofibrous cultures maintained in the supplemented serum‐free medium produced more sulfated proteoglycan‐rich, cartilaginous matrix than monolayer cultures. In addition to promoting phenotypic differentiation, the nanofibrous scaffold also supported cellular proliferation as evidenced by a 21‐fold increase in cell growth over 21 days when the cultures were maintained in serum‐containing medium. These results indicate that the biological activities of FBCs are crucially dependent on the architecture of the extracellular scaffolds as well as the composition of the culture medium, and that nanofibrous PCL acts as a biologically preferred scaffold/substrate for proliferation and maintenance of the chondrocytic phenotype. We propose that the PCL nanofibrous structure may be a suitable candidate scaffold for cartilage tissue engineering. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 1105–1114, 2003
Manipulations in hydrogel chemistry control photoencapsulated chondrocyte behavior and their extracellular matrix production
Authors: Bryant Stephanie J. , Durand Kevin L. , Anseth Kristi S. 
Published: November 2003

AbstractIn engineering a cell‐carrier to support cartilage growth, hydrogels provide a unique, largely aqueous environment for 3‐dimensional chondrocyte culture that facilitates nutrient transport yet provides an elastic framework dictating tissue shape and supporting external loads. Although the gel environment is often >90% water, we demonstrate that slight variations in hydrogel chemistry control gel degradation, evolving macroscopic properties, and ultimately the secretion and distribution of extracellular matrix molecules. Specifically, biodegradable poly(ethylene glycol)‐co‐poly(lactic acid) hydrogels were fabricated via photopolymerization. When chondrocytes were photoencapsulated in these gels, changes in the poly(ethylene glycol)‐co‐poly(lactic acid) repeat unit ratio from 19 to 7 increased total collagen synthesis 2.5‐fold after 6 weeks in vitro. Furthermore, the ratio of collagen to glycosaminoglycans varied from glycosaminoglycan‐rich, 0.33 ± 0.13, to collagen‐rich, 4.58 ± 1.21, depending on gel chemistry and in vitro versus in vivo culture environment. By tuning scaffold chemistry, and subsequently, gel structure and degradation behavior, we can better guide tissue evolution and development. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 1430–1436, 2003
Gradient micropattern immobilization of a thermo‐responsive polymer to investigate its effect on cell behavior
Authors: Liu Hongchun , Ito Yoshihiro 
Published: November 2003

AbstractA gradient micropattern immobilization technique using a photomask was developed to investigate by microscopic observation the effect of the surface concentration of an immobilized thermo‐responsive polymer. Poly(N‐isopropylacrylamide‐co‐acrylic acid) was chosen as the thermo‐responsive polymer, and was conjugated with 4‐azidoaniline to form a photo‐reactive thermo‐responsive polymer (PIA‐Az). The PIA‐Az was coated onto a polystyrene plate, and immobilized using UV irradiation in the presence of a gradient micropattern photomask. The immobilization was performed with and without gelatin. Mouse fibroblast STO cells cultured on the plate did not adhere to the surface when PIA‐Az had a high surface density, and no cell detachment was observed in any region when the temperature was lowered. However, on the gelatin coimmobilized surfaces, the cells adhered to all surfaces independent of the PIA‐Az density, and detached from the high PIA‐Az surface density areas when the temperature was lowered. The present technique demonstrates the effect of the surface concentration‐dependent immobilization of the molecules. We show that cell detachment can be regulated by perturbating a small part of the cell‐immobilized polymer interface. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 1424–1429, 2003
Variations in the ability of adsorbed fibrinogen to mediate platelet adhesion to polystyrene‐based materials: A multivariate statistical analysis of antibody binding to the platelet binding sites of fibrinogen
Authors: Tsai Wei‐Bor , Grunkemeier John M. , Horbett Thomas A. 
Published: November 2003

AbstractPlatelet adhesion to the surfaces of biomaterials preadsorbed with plasma previously has been shown to be mediated exclusively by surface‐bound fibrinogen and does not seem to involve the other adhesion proteins in plasma (Tsai et al., J Biomed Mater Res 2002;60:348–359). In this study, the influence of surface‐bound fibrinogen on platelet adhesion to five different types of polystyrene‐based microtiter plates preadsorbed with plasma was analyzed relative to the amount of adsorbed fibrinogen and monoclonal antibody binding to the adsorbed fibrinogen. There was no significant correlation between platelet adhesion and the absolute amount of adsorbed fibrinogen. However, platelet adhesion was positively correlated to the ability of the adsorbed fibrinogen to bind three types of monoclonal antibodies. The antibodies used bound to the sites on fibrinogen thought to be involved in platelet binding (the two γ chain C‐terminal dodecapeptides and the RGDF and RGDS sequences in each of the Aα chains). A partial least‐squares calibration model was used to analyze the relative importance of these binding sites in fibrinogen to platelet adhesion. The γ chain C‐terminal dodecapeptide was shown to be the most important site in adsorbed fibrinogen in mediating platelet adhesion. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 1255–1268, 2003
Isolation of intact aortic valve scaffolds for heart‐valve bioprostheses: Extracellular matrix structure, prevention from calcification, and cell repopulation features
Authors: Spina M. , Ortolani F. , Messlemani A. El , Gandaglia A. , Bujan J. , Garcia‐Honduvilla N. , Vesely I. , Gerosa G. , Casarotto D. , Petrelli L. , Marchini M. 
Published: November 2003

AbstractExtracellular matrix (ECM) scaffolds isolated from valvulated conduits can be useful in developing durable bioprostheses by tissue engineering provided that anatomical shape, architecture, and mechanical properties are preserved. As evidenced by SEM, intact scaffolds were derived from porcine aortic valves by the combined use of Triton X‐100 and cholate (TRI‐COL) or N‐cetylpyridinium (CPC) and subsequent nucleic acid removal by nuclease. Both treatments were effective in removing most cells and all the cytomembranes, with preservation of (1) endothelium basal membranes, (2) ECM texture, including the D‐periodical interaction of small proteoglycans with normally D‐banded collagen fibrils, and (3) mechanical properties of the treated valves. Ultrastructural features agreed with DNA, hexosamine, and uronic acid biochemical estimations. Calcification potential, assessed by a 6‐week rat subdermal model, was significantly reduced by TRI‐COL/nuclease treatment. This was not true for CPC only, despite better proteoglycan preservation, suggesting that nucleic acids also are involved in calcification onset. Human fibroblasts, used to repopulate TRI‐COL samples, formed mono‐ or multilayers on surfaces, and groups of cells also were scattered within the valve leaflet framework. A biocompatible scaffolds of this kind holds promise for production of durable valve bioprostheses that will be able to undergo probable turnover and/or remodeling by repopulating recipient cells. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 1338–1350, 2003
Performance of hydroxyapatite bone repair scaffolds created via three‐dimensional fabrication techniques
Authors: Dutta Roy Tithi , Simon Joshua L. , Ricci John L. , Rekow E. Dianne , Thompson Van P. , Parsons J. Russell 
Published: November 2003

AbstractThe current study analyzes the in vivo performance of porous sintered hydroxyapatite (HA) bone repair scaffolds fabricated using the TheriForm™ solid freeform fabrication process. Porous HA scaffolds with engineered macroscopic channels had a significantly higher percentage of new bone area compared with porous HA scaffolds without channels in a rabbit calvarial defect model at an 8‐week time point. An unexpected finding was the unusually large amount of new bone within the base material structure, which contained pores less than 20 μm in size. Compared with composite scaffolds of 80% polylactic‐co‐glycolic acid and 20% β‐tricalcium phosphate with the same macroscopic architecture as evaluated in a previous study, the porous HA scaffolds with channels had a significantly higher percentage of new bone area. Therefore, the current study indicates that scaffold geometry, as determined by the fabrication process, can enhance the ability of a ceramic material to accelerate healing of calvarial defects. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 1228–1237, 2003
Polymers with nano‐dimensional surface features enhance bladder smooth muscle cell adhesion
Authors: Thapa Anil , Webster Thomas J. , Haberstroh Karen M. 
Published: November 2003

AbstractPrevious studies investigating the design of synthetic bladder wall substitutes have involved polymers with micro dimensional structures. Since the body is made up of nano‐structured components (e.g., extracellular matrix proteins), the focus of the present in vitro study was to design nano‐structured polymers for use as synthetic bladder constructs that mimic the topography of natural bladder tissue. In order to complete this task, novel nano‐structured biodegradable polymeric films of poly‐lactic‐co‐glycolic‐acid (PLGA), poly‐ether‐urethane (PU), and poly‐caprolactone (PCL) were fabricated and separately treated with various concentrations of NaOH (for PLGA and PCL) and HNO3 (for PU) for select time periods. These treatments reduced the polymer surface feature dimensions from conventional micron dimensions to biologically inspired nanometer dimensions. Select cytocompatibility properties of these biomaterials were tested in vitro. Results provide the first evidence that adhesion of bladder smooth muscle cells is enhanced as polymer surface feature dimensions are reduced into the nanometer range. In addition, surface analysis results reveal that the polymer nanometer surface roughness is the primary design parameter that increases bladder smooth muscle cell adhesion. For this reason, the “next generation” of tissue‐engineered bladder constructs with increased efficacy should contain surfaces with nanometer (as opposed to micron) surface features. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 1374–1383, 2003
Effects of matrix stabilization when using glutaraldehyde on the material properties of porcine meniscus
Authors: Hunter Shawn A. , Noyes Frank R. , Haridas Balakrishna , Levy Martin S. , Butler David L. 
Published: November 2003

AbstractMeniscus transplantation frequently is one of the only options available for treating symptomatic younger patients with tibiofemoral pain and early arthrosis after a prior meniscectomy. However, clinical results indicate that current meniscal allografts may undergo degenerative changes due to enzymatic degradation during the remodeling phase. The objective of this study was to evaluate the effects of glutaraldehyde‐induced matrix stabilization on the material properties of porcine meniscus prior to surgical implantation. Protocols for fabricating heart‐valve replacements were examined, followed by an exploration of the effects of reducing glutaraldehyde concentration and exposure time. Cylindrical meniscus specimens were tested in uniaxial confined compression under a 0.196 MPa compressive stress, and aggregate modulus (HA), permeability (k), and compressive strains at equilibrium (ϵeq) were calculated from the creep response. Compared to controls, the mean values for HA and k increased, on average, by 213 and 709%, respectively, and ϵeq decreased by 57% for all “heart‐valve” treatments. Reducing tissue exposure time to glutaraldehyde had little effect, but decreasing glutaraldehyde concentration to 0.02% resulted in tissues with material properties no different from the untreated controls. We conclude that minimal concentrations of glutaraldehyde (less than 0.2%) should be used in future studies to preserve normal meniscus properties. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 1245–1254, 2003
Competitive plasma protein adsorption onto fluorinated polyimide surfaces
Authors: Kawakami H. , Kanno M. , Nagaoka S. , Kubota S. 
Published: November 2003

AbstractA series of fluorinated polyimides cured at different temperatures was prepared, and plasma protein adsorption and platelet adhesion onto the polyimide films were evaluated in vitro using scanning electron microscopy, a micro‐bicinchoninic acid protein assay, and a gold–colloid‐labeled immunoassay. In particular, we focused on competitive plasma protein adsorption onto polyimide film because elucidation of the competitive adsorption mechanism is needed for a good understanding of in vivo biocompatibility of polyimide. Interestingly, the trend of IgG adsorption onto the polyimide surface measured in human plasma was completely contrary to that observed with IgG dissolved in PBS, and the adsorption increased with an increase in the curing temperature. We propose that the human plasma Fc region in IgG might selectively adsorb onto polyimide film cured at high temperatures because of competitive plasma protein adsorption to the surface. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 1393–1400, 2003
Bioinspired organic‐inorganic composite materials prepared by an alternate soaking process as a tissue reconstitution matrix
Authors: Ogomi Daisuke , Serizawa Takeshi , Akashi Mitsuru 
Published: November 2003

AbstractPoly(acrylic acid) (PAAc) grafted poly(ethylene) (PE) (PAAc‐g‐PE) film‐apatite or calcium carbonate (CaCO3) composite materials were prepared by an alternate soaking process, which simply forms apatite or CaCO3 on the polymer materials by alternate soaking in Ca2+‐ and PO‐ or CO32−‐containing solutions. X‐ray diffraction analysis of the composite films indicated the presence of hydroxyapatite or CaCO3 on the film. Scanning electron microscopic observation revealed that the whole surface of the film was covered by the apatite or CaCO3. Cell compatibility tests of the apatite‐ or CaCO3‐coated film suggested that the greater number of cells adhered on the films and that the cell proliferation properties were extremely greater on the films. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 1360–1366, 2003
In vitroevaluation of novel bioactive composites based on Bioglass®‐filled polylactide foams for bone tissue engineering scaffolds
Authors: Blaker J. J. , Gough J. E. , Maquet V. , Notingher I. , Boccaccini A. R. 
Published: November 2003

AbstractHighly porous poly(DL‐lactic acid) (PDLLA) foams and Bioglass®‐filled PDLLA composite foams were characterized and evaluatedin vitroas bone tissue engineering scaffolds. The hypothesis was that the combination of PDLLA with Bioglass® in a porous structure would result in a bioresorbable and bioactive composite, capable of supporting osteoblast adhesion, spreading and viability. Composite and unfilled foams were incubated in simulated body fluid (SBF) at 37°C to study thein vitrodegradation of the polymer and to detect hydroxyapatite (HA) formation, which is a measure of the materials'in vitrobioactivity. HA was detected on all the composite samples after incubation in SBF for just 3 days. After 28 days immersion the foams filled with 40 wt % Bioglass® developed a continuous layer of HA. The formation of HA for the 5 wt % Bioglass®‐filled foams was localized to the Bioglass® particles. Cell culture studies using a commercially available (ECACC) human osteosarcoma cell line (MG‐63) were conducted to assess the biocompatibility of the foams and cell attachment to the porous substrates. The osteoblast cell infiltration study showed that the cells were able to migrate through the porous network and colonize the deeper regions within the foam, indicating that the composition of the foams and the pore structures are able to support osteoblast attachment, spreading, and viability. Rapid formation of HA on the composites and the attachment of MG‐63 cells within the porous network of the composite foams confirms the highin vitrobioactivity and biocompatibility of these materials and their potential to be used as scaffolds in bone tissue engineering and repair. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 1401–1411, 2003
Epigenetic regulation of Igf2/H19 imprinting at CTCF insulator binding sites
Authors: Yang Youwen , Hu Ji‐Fan , Ulaner Gary A. , Li Tao , Yao Xiaoming , Vu Thanh H. , Hoffman Andrew R. 
Published: November 2003

AbstractThe mouse insulin‐like growth factor II (Igf2) and H19 genes are located adjacent to each other on chromosome 7q11‐13 and are reciprocally imprinted. It is believed that the allelic expression of these two genes is regulated by the binding of CTCF insulators to four parent‐specific DNA methylation sites in an imprinting control center (ICR) located between these two genes. Although monoallelically expressed in peripheral tissues, Igf2 is biallelically transcribed in the CNS. In this study, we examined the allelic DNA methylation and CTCF binding in the Igf2/H19 imprinting center in CNS, hypothesizing that the aberrant CTCF binding as one of the mechanisms leads to biallelic expression of Igf2 in CNS. Using hybrid F1 mice (M. spretus males × C57BL/6 females), we showed that in CNS, CTCF binding sites in the ICR were methylated exclusively on the paternal allele, and CTCF bound only to the unmethylated maternal allele, showing no differences from the imprinted peripheral tissues. Among three other epigenetic modifications examined, histone H3 lysine 9 methylation correlated well with Igf2 allelic expression in CNS. These results suggest that CTCF binding to the ICR alone is not sufficient to insulate the Igf2 maternal promoter and to regulate the allelic expression of the gene in the CNS, thus challenging the aberrant CTCF binding as a common mechanism for lack of Igf2 imprinting in CNS. Further studies should be focused on the identification of factors that are involved in histone methylation and CTCF‐associated factors that may be needed to coordinate Igf2 imprinting. © 2003 Wiley‐Liss, Inc.
High dose M‐CSF partially rescues the Dap12−/− osteoclast phenotype
Authors: Faccio Roberta , Zou Wei , Colaianni Graziana , Teitelbaum Steven L. , Patrick Ross F. 
Published: November 2003

AbstractOsteoclasts are macrophage derived cells and as such are subject to regulation by molecules impacting other members of the immune system. Dap12 is an adaptor protein expressed by NK cells and B and T lymphocytes. Dap12 also mediates maturation of myeloid cells and is expressed by osteoclasts which are dysfunctional in its absence. We find Dap12−/− osteoclast precursors fail to differentiate, in vitro, and the abnormality is partially rescued by high dose M‐CSF. The relative paucity of osteoclast number, even in presence of high dose cytokine, is attended by dampened proliferation of precursor cells and their failure to normally migrate towards the osteoclast‐recognized matrix protein, osteopontin. Furthermore, Dap12−/− osteoclasts generated in high dose M‐CSF fail to normally organize their cytoskeleton. The incapacity of Dap12 null cells to undergo normal osteoclast differentiation is not due to blunted stimulation of major RANK ligand (RANKL) or M‐CSF induced signaling pathways. On the other hand, when plated on osteopontin, Dap12−/− pre‐osteoclasts do not activate the tyrosine kinase, Syk, which normally binds to the adaptor protein and transmits downstream signals. Attesting to the importance of the Dap12/Syk complex, Syk deficient macrophages do not undergo normal osteoclastogenesis. Furthermore, the same cells plated onto osteopontin, adhere poorly and fail to phosphorylate c‐Src or Pyk2, two kinases central to organization of the osteoclast cytoskeleton. © 2003 Wiley‐Liss, Inc.