bluuebunny/crossref_metadata_2025_split huggingface dataset:
In vitro biocompatibility evaluation of poly(3‐hydroxybutyrate‐co‐4‐hydroxybutyrate) copolymer in fibroblast cells
Authors: Siew Ee Ling , Rajab Nor Fadilah , Osman Annuar Bin , Sudesh Kumar , Inayat‐Hussain Salmaan Hussain 
Published: November 2006

AbstractAmong the various biomaterials available for tissue engineering and therapeutic applications, microbial polyhydroxyalkanoates offer the most diverse range of thermal and mechanical properties. In this study, the biocompatibility of poly(3‐hydroxybutyrate‐co‐4‐hydroxybutyrate) [P(3HB‐co‐4HB); containing 50 mol % of 4‐hydroxybutyrate] copolymer produced by Delftia acidovorans was evaluated. The cytotoxicity, mode of cell death, and genotoxicity of P(3HB‐co‐4HB) extract against V79 and L929 fibroblast cells were assessed using MTT assay, acridine orange/propidium iodide staining, and alkaline comet assay, respectively. Our results demonstrate that P(3HB‐co‐4HB) treated on both cell lines were comparable with clinically‐used Polyglactin 910, where more than 60% of viable cells were observed following 72‐h treatment at 200 mg/mL. Further morphological investigation on the mode of cell death showed an increase in apoptotic cells in a time‐dependent manner in both cell lines. On the other hand, P(3HB‐co‐4HB) at 200 mg/mL showed no genotoxic effects as determined by alkaline comet assay following 72‐h treatment. In conclusion, our study indicated that P(3HB‐co‐4HB) compounds showed good biocompatibility in fibroblast cells suggesting that it has potential to be used for future medical applications. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res 2007
Biodegradation of high‐toughness double network hydrogels as potential materials for artificial cartilage
Authors: Azuma Chinatsu , Yasuda Kazunori , Tanabe Yoshie , Taniguro Hiroko , Kanaya Fuminori , Nakayama Atsushi , Chen Yong Mei , Gong Jian Ping , Osada Yoshihito 
Published: November 2006

AbstractThis study evaluated biodegradation properties of four novel high‐toughness double network (DN) hydrogels as potential materials for artificial cartilage. Concerning each DN gel material, a total of 12 specimens were prepared, and 6 of the 12 specimens were examined to determine the mechanical properties without any treatments. The remaining 6 specimens were implanted into the subcutaneous tissue, using 6 mature female rabbits. At 6 weeks after implantation, the mechanical properties and the water content of the implanted specimens were measured. In the poly(2‐acrylamide‐2‐methyl‐propane sulfonic acid)/poly(N,N′‐dimethyl acrylamide) DN gel, the ultimate stress and the tangent modulus were significantly increased from 3.10 and 0.20 MPa, respectively, to 5.40 and 0.37 MPa, respectively, with a significant reduction of the water content after implantation (94 to 91%). In the poly(2‐acrylamide‐2‐methyl‐propane sulfonic acid)/polyacrylamide DN gel and the cellulose/poly(dimethyl acrylamide) DN gel, the stress (11.4 and 1.90 MPa, respectively) and the modulus (0.30 and 1.70 MPa, respectively) or the water content rarely changed after implantation (90 and 85%, respectively). In the bacterial cellulose/gelatin DN gel, the ultimate stress was dramatically reduced from 4.30 to 1.98 MPa with a significant increase of the water content after implantation (78 to 86%). This study implied that these DN gels except for the cellulose/gelatin DN gel are potential materials that may meet the requirements of artificial cartilage. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res, 2007
Controlled release of nerve growth factor from fibrin gel
Authors: Bhang Suk Ho , Jeon Oju , Choi Cha Yong , Kwon Yun Hee Kim , Kim Byung‐Soo 
Published: November 2006

AbstractNerve growth factor (NGF) is known to promote the axonal regeneration in injured nerve system. Delivery of NGF for a long period in a controlled manner may enhance the regeneration efficacy. In this study, we investigated whether NGF can be released from fibrin gel for a long period in a controlled manner. We also investigated whether sustained delivery of NGF using fibrin gel can enhance the efficacy of NGF in vitro. The addition of heparin to fibrin gel decreased the rate of NGF release from the fibrin gel. As the concentrations of thrombin and fibrinogen in fibrin gel increased, the NGF release rate decreased significantly, and the initial release burst decreased. NGF was released for up to 14 days in vitro. The bioactivity of NGF released from fibrin gel was assessed by morphological changes of pheochromocytoma (PC12) cells cultured in the presence of NGF‐containing fibrin gel. NGF released from fibrin gel exhibited significantly higher degrees of PC12 cell viability and differentiation than NGF added in a free form daily into the culture medium. This study demonstrates that fibrin gel can release NGF in a sustained, controlled manner and in a bioactive form. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res, 2007
Paclitaxel‐loaded composite fibers: Microstructure and emulsion stability
Authors: Kraitzer Amir , Zilberman Meital 
Published: November 2006

AbstractNew core/shell fiber structures loaded with paclitaxel were developed and studied. These composite fibers are ideal for forming thin, delicate, biomedically important structures for various applications. Possible applications include fiber‐based endovascular stents that mechanically support blood vessels while delivering drugs for preventing restenosis directly to the blood vessel wall, or drug delivery systems for cancer treatment. The core/shell fiber structures were formed by “coating” nylon fibers with porous paclitaxel‐containing poly(DL‐lactic‐co‐glycolic acid) structures. Shell preparation (“coating”) was performed by freeze‐drying water in oil emulsions. The present study focused on the effects of the emulsion's formulation (composition) and processing conditions on the porous shell structure, which actually reflects the emulsion's stability and also the drug release profile from the fibers. In general, extremely porous “shell” structures were obtained with good adhesion to the core fiber. An increase in the emulsion's drug content and copolymer composition demonstrated a significant effect on pore size and distribution, because of enhanced emulsion instability, whereas the homogenization rate and duration had only a slight effect on the pores' microstructure. The thermodynamic parameters in the studied system are thus more important than the kinetic parameters in determining the emulsion's stability and the shell's porous structure. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res, 2007
In vitro osteoblastic response to 30 vol% hydroxyapatite‐polyethylene composite
Authors: Zhang Y. , Tanner K.E. , Gurav N. , Di Silvio L. 
Published: November 2006

AbstractHydroxyapatite‐reinforced high‐density polyethylene (HA‐HDPE) composite, as a bone replacement material, has successfully been used clinically as middle ear prostheses and orbital floor implants. The aim of this study was to examine its in vitro biocompatibility in order to develop a further application, that is, as skull reconstruction implants. Human osteoblast cells isolated from femoral heads and crania were used to determine the biological response of the composites. HA‐HDPE composites (30 vol %) with two grades of HA filler that had different surface morphologies were selected for this in vitro assessment. The results showed that HA‐HDPE composite was bioactive and supported osteoblast attachment, proliferation, and differentiation. The composite with rough‐surfaced HA filler demonstrated slightly better cellular response than the composite with smooth‐surfaced HA filler. Although osteoblastic cells derived from skull showed an overall slower response compared with those from femoral heads, these in vitro results show that HA‐HDPE composite potentially could be used as a skull implant. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res, 2007
Osteoblast response to titanium regulates transcriptional activity of Runx2 through MAPK pathway
Authors: Hata Kenji , Ikebe Kazunori , Wada Masahiro , Nokubi Takashi 
Published: November 2006

AbstractBone formation around an implant surface is indispensable for osseointegration of dental implants. Transcriptional factor Runx2 is essential for osteoblast differentiation and bone formation. However, little is known about the involvement of Runx2 in osseointegration. The purpose of this study was to investigate molecular interactions between Runx2 and implant titanium materials at the transcriptional level. Primary osteoblasts isolated from mouse calvaria and C3H10T1/2 cells were cultured on titanium plates or in the presence of titanium particles. Transcriptional activity of Runx2 was measured by reporter assay using osteocalcin gene promoter. We found significant increase (p < 0.05) in Runx2 transcriptional activity in cells cultured on titanium plates compared to plastic plates. Titanium particles also upregulated Runx2 transcriptional activity for over 2‐folds compared to control and this effect was abolished by the specific inhibitor for ERK1/2, PD98059. Moreover, treatment with PD98059 clearly suppressed osteoblast mineralization cultured on titanium plates. These data suggest that osteoblast attachment to titanium enhanced Runx2 transcriptional activity and bone formation via MAPK pathway during the osseointegration of dental implants. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res, 2007
Regulation of cyclin‐dependent kinase 5 and p53 by ERK1/2 pathway in the DNA damage‐induced neuronal death
Authors: Lee Jong‐Hee , Kim Kyong‐Tai 
Published: November 2006

AbstractDNA damage is known to be an initiator of neuronal death in neurodegenerative conditions such as Parkinson's and Alzheimer's diseases. The mechanism linking DNA damage and neuronal death is not completely understood. Here, we delineate the mechanism by which neuronal death evoked by DNA damage is controlled. Using mouse cortical neurons and SH‐SY5Y human neuroblastoma cells, we identify a critical role of ERK signaling in neuronal death induced by DNA damage upon mitomycin C treatment. In addition, we provide evidence that the ERK signaling regulates Cyclin‐dependent kinase 5 (Cdk5) activity and stability of tumor suppressor p53. Mitomycin C increased expression of p35, a specific activator of neuronal Cdk5 in an ERK1/2‐dependent manner. Moreover, stability of p53 was increased by its phosphorylation on Ser33 and Ser46 by Cdk5, leading to neuronal death. Finally, we show that activated ERK induced increased expression of the Egr‐1 transcription factor, which then bound to the promoter region of p35. We suggest subsequent increase of p35 expression and Cdk5 activity contribute to p53‐dependent neuronal death. Thus, the present finding provides a new insight into a molecular mechanism underlying DNA damage‐induced neuronal death. J. Cell. Physiol. 210: 784–797, 2007. © 2006 Wiley‐Liss, Inc.
A benzimidazole‐based chromogenic anion receptor
Authors: Yu Ming , Lin Hai , Zhao Guanhua , Lin Huakuan 
Published: November 2006

AbstractA benzimidazole‐based anion receptor 1 has been designed and synthesized. The structure of 1 is confirmed through single crystal X‐ray diffraction analysis. Anion‐binding studies carried out using 1H NMR and UV–visible revealed that this compound exhibits selective recognition toward F− over other halide anions. The highest selectivity for F− among the halides is attributed mainly to the strongest hydrogen‐bond interaction of the receptor with F−; in addition, the higher match in geometry between the receptor and F− also plays a role in the selective recognition of the receptor for F−. Receptor 1 (1 × 10−5 M) shows dramatic color change from light‐yellow to red in the presence of tetrabutylammonium fluoride (TBAF) (1 × 10−5 M). Moreover, F−‐induced color changes remain the same even in the presence of a large excess of Cl−, Br−, I−. Copyright © 2006 John Wiley & Sons, Ltd.
Polymerization of Styrene Sulfonate Ethyl Ester by ATRP: Synthesis and Characterization of Macromonomers for Suzuki Polycondensation
Authors: Lienkamp Karen , Schnell Ingo , Groehn Franziska , Wegner Gerhard 
Published: November 2006

AbstractSummary: Macromonomers from SSE were synthesized via ATRP with initiators carrying functional groups that are polymerizable by Suzuki polycondensation. The material obtained had a monomodal molar mass distribution with a polydispersity of 1.3–1.6. The reaction kinetics in bulk and in solution were monitored by in situ 1H NMR spectroscopy. Rate constants and the activation energy for SSE polymerization were determined to be k = 5.5 · 10−5 s−1 (DMF, 60 °C), 6.6 · 10−4 s−1/1.4 · 10−3 s−1/4.8 · 10−3 s−1 (bulk, 45/60/75 °C), Ea = 60.1 kJ · mol−1 (bulk). Hydrolysis yielded the corresponding macromonomers of poly(styrene sulfonic acid).Monomer conversion for different reaction temperatures and exponential fit to the data for the SSE polymerization in bulk.magnified imageMonomer conversion for different reaction temperatures and exponential fit to the data for the SSE polymerization in bulk.
Preparation and Characterization of Hybrid Nanocomposites Coated on LDPE
Authors: Mazzocchetti Laura , Scandola Mariastella , Amerio Ezio , Malucelli Giulio , Marano Claudia 
Published: November 2006

AbstractSummary: Hybrid organic‐inorganic nanocomposites containing hyperbranched structures were prepared through a dual‐curing process, which involves photopolymerization and condensation alkoxysilane groups. In particular, an oligomer containing PEO units and α,ω‐methacrylate groups was used together with a HBP bearing acrylic groups as the organic phase precursors. MEMO, as the organic‐inorganic linker, and TEOS, as inorganic phase precursor, were also employed. The kinetics of both photopolymerization and condensation reactions were investigated by double bond conversion analysis (via FT‐IR) and weight loss determination, respectively. The mobility of the organic phase was studied by means of DSC and DMTA and correlated with hybrid composition. TEM analyses performed on microtomed film slices indicated the formation of nanoscale silica domains. Hybrids were coated onto an LDPE film previously subjected to a plasma treatment, and substrate‐coating interfacial adhesion was investigated through stress‐strain and DMTA experiments.Reaction scheme showing the insertion of furanic units in copolyester chains by ester interchange reaction.magnified imageReaction scheme showing the insertion of furanic units in copolyester chains by ester interchange reaction.
Furanic‐Aromatic Copolyesters by Interchange Reactions between Poly(ethylene terephthalate) and Poly[ethylene 5,5′‐isopropylidene‐bis(2‐furoate)]
Authors: Kamoun Wided , Salhi Slim , Rousseau Brigitte , El Gharbi Rachid , Fradet Alain 
Published: November 2006

AbstractSummary: Aromatic copolyesters containing bio‐based furanic units in the main chain were obtained by ester‐interchange reaction between poly(ethylene terephthalate) (PET) and poly[ethylene 5,5′‐isopropylidene‐bis(2‐furoate)] (PEF) at high temperatures in the bulk. Various copolyesters were synthesized by using PET/PEF mass ratios ranging from 90:10 to 50:50 and were characterized by 1H NMR, MALDI‐TOF MS, DSC, and TGA. PET/PEF block copolymers were formed in the first stage of reaction and then slowly randomized. The degree of randomness, determined by 1H NMR, was close to 1 after 2 h reaction. The randomization rate depended on the nature and the concentration of the end‐groups of starting homopolyesters and was much faster when a low molar mass hydroxy‐terminated PET was reacted.Reaction scheme showing the insertion of furanic units in copolyester chains by ester interchange reaction.magnified imageReaction scheme showing the insertion of furanic units in copolyester chains by ester interchange reaction.
Fabrication of Nanoparticle/Polymer Composites by In Situ Bubble‐Stretching and Reactive Compatibilization
Authors: Cai Li Feng , Huang Xian Bo , Rong Min Zhi , Ruan Wen Hong , Zhang Ming Qiu 
Published: November 2006

AbstractSummary: A new route for fabricating polymer nanocomposites is proposed which combines in situ bubble‐stretching and reactive compatibilization techniques. That is, a polymeric foaming agent p‐vinylphenylsulfonylhydrazide was synthesized and grafted onto nano‐SiO2. Then, the grafted nanoparticles were melt mixed with matrix PP. In the meantime, some of the side sulfonyl hydrazide groups on the grafted polymer were gasified to form polymer bubbles, leading to rapid inflation of the surrounding matrix that pulled apart the agglomerated nanoparticles, while the remaining non‐decomposed sulfonyl hydrazide groups reacted with the epoxide groups of PGMA‐grafted PP forming chemical bonds. Owing to the simultaneously improved dispersion of the nanoparticles and the interfacial interaction, the mechanical properties, especially notched impact strength, of the nano‐SiO2/PP composites were greatly enhanced. The structure‐property relationship was carefully studied.Simultaneous improvement of dispersion nanoparticles and interfacial interaction.magnified imageSimultaneous improvement of dispersion nanoparticles and interfacial interaction.
Fabrication of Polyaniline Nanostructures under Ultrasonic Irradiation: From Nanotubes to Nanofibers
Authors: Lu Xiaofeng , Mao Hui , Chao Danming , Zhang Wanjin , Wei Yen 
Published: November 2006

AbstractSummary: An ultrasonic irradiation assisted polymerization method has been used to prepare PANI nanotubes and nanofibers by using different doping concentrations of mineral or organic acids. It has been found that PANI nanotubes can be produced when the concentration of the dopant acid is low. However, PANI nanofibers can also be produced when the concentration of the dopant acid is high. For nanotubes synthesized at a low concentration of the dopant acid, the outer average diameter can be changed from about 150 nm using phosphoric acid to 200 nm using nitric acid as the dopant and the inter diameter is in the range of 10–50 nm. For nanofibers, the diameter ranges from about 50 nm using nitric acid to more than 110 nm using perchloric acid as the dopant. The mechanism of the formation of the nanotubes and nanofibers may be due to the formation of different kinds of micelles and the prevention of the second growth of the PANI by ultrasonic irradiation. The chemical structure of the PANI nanotubes and nanofibers are characterized by FTIR and UV‐vis absorption spectra and XRD patterns. The conductivity of the PANI nanofibers is comparable to that of conventional PANI samples.TEM images of PANI nanofibers synthesized under ultrasonic irradiation doped by perchloric acid.magnified imageTEM images of PANI nanofibers synthesized under ultrasonic irradiation doped by perchloric acid.
Self‐Catalysis of Phthaloylchitosan for Graft Copolymerization of ε‐Caprolactone with Chitosan
Authors: Liu Li , Chen Liuxi , Fang Yue'e 
Published: November 2006

AbstractSummary: A protection‐graft‐deprotection method was developed to prepare chitosan‐g‐polycaprolactone graft copolymers, during which the ring‐opening copolymerization of ε‐caprolactone onto phthaloylchitosan (PHCS) happened without any additional catalysis. The intermediate PHCS was introduced primarily to protect the active amino group of chitosan. After controlled experiments, the phthalimido compound was proposed to be a novel kind of organic catalyst for the ring‐opening polymerization of caprolactone monomers, while the hydroxyl group acted as an initiator. Hence, in this graft system, PHCS was endowed with both self‐catalysis and self‐initiation at the same time, and the PCL side chains grew from the hydroxyl groups of the chitosan backbone.
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Branched Oligovinylcyclopropane by Transfer to Allylic Carbonate Comonomers via Radical Ring‐Opening Polymerization
Authors: Sarker Prodip , Ebdon John R. , Rimmer Stephen 
Published: November 2006

AbstractSummary: Radical copolymerization of 1,1‐bis(ethoxycarbonyl)‐2‐vinylcyclopropane (ECVCP) with allyl carbonates that contain isopropyl groups yields highly branched polyvinylcyclopropanes. The polymerizations were carried out in the presence of 2,2‐azoisobutyronitrile at 150 °C in chlorobenzene. Structural analysis of the polymers suggested that radical ring‐opening polymerization proceeded through 1,5‐ring‐opening followed by transfer to the allylic carbonate comonomers. Intra‐molecular cyclization, which yields polycyclobutane units, was also observed during the polymerization.Synthesis of branched 1,1‐bis(ethoxycarbonyl)‐2‐vinylcyclopropane by transfer to the isopropoxy functional allyl carbonate comonomers.magnified imageSynthesis of branched 1,1‐bis(ethoxycarbonyl)‐2‐vinylcyclopropane by transfer to the isopropoxy functional allyl carbonate comonomers.
Exothermal Process in Miscible Polylactide/Poly(vinyl phenol) Blends: Mixing Enthalpy or Chemical Reaction?
Authors: Zuza Ester , Meaurio Emilio , Etxeberria Agustin , Sarasua Jose‐Ramon 
Published: November 2006

AbstractSummary: In a previous paper (Macromolecules, 2005, 38, 9221), the enthalpy of mixing in poly(DL‐lactide) /poly(vinyl phenol) blends was directly measured by DSC. The first DSC scan for solution/precipitation blends showed phase separation, but miscibility was observed in the second DSC scan. Hence, miscibility was achieved after thermal treatment, an unusual behavior in polymer blend current research. However, the exothermal event observed during the first heating scan could also be the result of a chemical reaction. In this work, a new research study conducted to elucidate the nature of the exothermal heat observed in PDLA/PVPh during the first DSC heating scan. Since the single‐phase PDLLA/PVPh blend obtained after thermal treatment can be redissolved and reprecipitated, results obtained in the consecutive DSC scan prove that the process is completely reversible. Furthermore, GPC and 13C NMR results provide evidence that there is no change in the chemical structure of the studied polymers before and after the thermal treatment, which evidences the absence of transesterification reactions. Therefore, it can be concluded that the exothermal heat is the result of a mixing process, and miscibility is a consequence of specific interactions.New structure expected for transesterfication reactions.magnified imageNew structure expected for transesterfication reactions.