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Adhesive Strength (adhesive + strength)
Selected AbstractsApplication of chitosan solutions gelled by melB tyrosinase to water-resistant adhesivesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2008Kazunori Yamada Abstract An investigation was undertaken on the application of dilute chitosan solutions gelled by melB tyrosinase-catalyzed reaction with 3,4-dihydroxyphenethylamine (dopamine). The tyrosinase-catalyzed reaction with dopamine conferred water-resistant adhesive properties to the semi-dilute chitosan solutions. The viscosity of the chitosan solutions highly increased by the tyrosinase-catalyzed quinone conversion and the subsequent nonenzymatic reactions of o -quinones with amino groups of the chitosan chains. The viscosity of chitosan solutions highly increased in shorter reaction times by addition of melB tyrosinase. Therefore, in this study, the gelation of a chitosan solution was carried out without poly(ethylene glycol) (PEG), which was added for the gelation of chitosan solutions using mushroom tyrosinase. The highly viscous, gel-like modified chitosan materials were allowed to spread onto the surfaces of the glass slides, which were tightly lapped together and were held under water. Tensile shear adhesive strength of over 400 kPa was observed for the modified chitosan samples. An increase in either amino group concentration of the chitosan solutions or molecular mass of the chitosan samples used effectively led to an increase in adhesive strength of the glass slides. Adhesive strength obtained by chitosan materials gelled enzymatically was higher than that obtained by a chitosan gel prepared with glutaraldehyde as a chemical crosslinking agent. In addition, the use of melB tyrosinase led to a sharp increase in adhesive strength in shorter reaction times without other additives such as PEG. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Steroid hormones strongly support bovine articular cartilage integration in the absence of interleukin-1,ARTHRITIS & RHEUMATISM, Issue 12 2006Carsten Englert Objective Posttraumatic integration of articular cartilage at fracture sites is essential for mechanical stability of cartilage, and ruptured cartilage is a prerequisite for early osteoarthritis. This study was undertaken to investigate effects on articular cartilage integration mediated by steroid hormones, interleukin-1, (IL-1,), and combinations thereof. Methods Articular cartilage blocks were cultured in partial apposition for 2 weeks with ascorbic acid, testosterone, 17,-estradiol, and dehydroepiandrosterone (DHEA), with or without IL-1,. Mechanical integration was measured as adhesive strength, i.e., the maximum force at rupture of integrated cartilage blocks divided by the overlap area. Glycosaminoglycan content was used to study synthesized extracellular matrix. Results Culture in medium without supplements did not lead to integration (adhesive strength 0 kPa). With administration of ascorbic acid (100 ,g/ml), the median adhesive strength was 49 kPa. In comparison with ascorbic acid alone, all steroid hormones induced a strong, concentration-dependent stimulation of integration (with maximum values observed with DHEA at 3 × 10,5M, testosterone at 10,8M, and 17,-estradiol at 10,11M). For testosterone and 17,-estradiol, this was also reflected by an increase of glycosaminoglycan content. Adhesive strength was increased with IL-1, at 10 pg/ml, but not at 1 pg/ml or 100 pg/ml. In the presence of both IL-1, and sex hormones, integration of articular cartilage was reduced. Conclusion This is the first study to demonstrate that steroid hormones such as 17,-estradiol, DHEA, and testosterone stimulate articular cartilage integration. This effect is abrogated by low concentrations of IL-1,. In the absence of IL-1, or after neutralization of IL-1,, steroid hormones might be favorable adjuvant compounds to optimize cartilage integration. [source] A FAK/Src chimera with gain-of-function properties promotes formation of large peripheral adhesions associated with dynamic actin assemblyCYTOSKELETON, Issue 1 2008Priscila M. F. Siesser Abstract Formation of a complex between the tyrosine kinases FAK and Src is a key integrin-mediated signaling event implicated in cell motility, survival, and proliferation. Past studies indicate that FAK functions in the complex primarily as a "scaffold," acting to recruit and activate Src within cell/matrix adhesions. To study the cellular impact of FAK-associated Src signaling we developed a novel gain-of-function approach that involves expressing a chimeric protein with the FAK kinase domain replaced by the Src kinase domain. This FAK/Src chimera is subject to adhesion-dependent activation and promotes tyrosine phosphorylation of p130Cas and paxillin to higher steady-state levels than is achieved by wild-type FAK. When expressed in FAK ,/, mouse embryo fibroblasts, the FAK/Src chimera resulted in a striking cellular phenotype characterized by unusual large peripheral adhesions, enhanced adhesive strength, and greatly reduced motility. Live cell imaging of the chimera-expressing FAK ,/, cells provided evidence that the large peripheral adhesions are associated with a dynamic actin assembly process that is sensitive to a Src-selective inhibitor. These findings suggest that FAK-associated Src kinase activity has the capacity to promote adhesion integrity and actin assembly. Cell Motil. Cytoskeleton 2008. © 2007 Wiley-Liss, Inc. [source] Plakoglobin-dependent disruption of the desmosomal plaque in pemphigus vulgarisEXPERIMENTAL DERMATOLOGY, Issue 6 2007Alain De Bruin Abstract:, We recently reported that the pathogenesis of pemphigus vulgaris (PV), an autoimmune blistering skin disorder, is driven by the accumulation of c-Myc secondary to abrogation of plakoglobin (PG)-mediated transcriptional c-Myc suppression. PG knock-out mouse keratinocytes express high levels of c-Myc and resemble PVIgG-treated wild-type keratinocytes in most respects. However, they fail to accumulate nuclear c-Myc and loose intercellular adhesion in response to PVIgG-treatment like wild-type keratinocytes. This suggested that PG is also required for propagation of the PVIgG-induced events between augmented c-Myc expression and acantholysis. Here, we addressed this possibility by comparing PVIgG-induced changes in the desmosomal organization between wild-type and PG knock-out keratinocytes. We found that either bivalent PVIgG or monovalent PV-Fab (known to trigger blister formation in vivo) disrupt the linear organization of all major desmosomal components along cell borders in wild-type keratinocytes, simultaneously with a reduction in intercellular adhesive strength. In contrast, PV-Fab failed to affect PG knock-out keratinocytes while PVIgG cross-linked their desmosomal cadherins without significantly affecting desmoplakin. These results identify PG as a principle effector of the PVIgG-induced signals downstream of c-Myc that disrupt the desmosomal plaque at the plasma membrane. [source] Application of chitosan solutions gelled by melB tyrosinase to water-resistant adhesivesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2008Kazunori Yamada Abstract An investigation was undertaken on the application of dilute chitosan solutions gelled by melB tyrosinase-catalyzed reaction with 3,4-dihydroxyphenethylamine (dopamine). The tyrosinase-catalyzed reaction with dopamine conferred water-resistant adhesive properties to the semi-dilute chitosan solutions. The viscosity of the chitosan solutions highly increased by the tyrosinase-catalyzed quinone conversion and the subsequent nonenzymatic reactions of o -quinones with amino groups of the chitosan chains. The viscosity of chitosan solutions highly increased in shorter reaction times by addition of melB tyrosinase. Therefore, in this study, the gelation of a chitosan solution was carried out without poly(ethylene glycol) (PEG), which was added for the gelation of chitosan solutions using mushroom tyrosinase. The highly viscous, gel-like modified chitosan materials were allowed to spread onto the surfaces of the glass slides, which were tightly lapped together and were held under water. Tensile shear adhesive strength of over 400 kPa was observed for the modified chitosan samples. An increase in either amino group concentration of the chitosan solutions or molecular mass of the chitosan samples used effectively led to an increase in adhesive strength of the glass slides. Adhesive strength obtained by chitosan materials gelled enzymatically was higher than that obtained by a chitosan gel prepared with glutaraldehyde as a chemical crosslinking agent. In addition, the use of melB tyrosinase led to a sharp increase in adhesive strength in shorter reaction times without other additives such as PEG. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] PR-39 coordinates changes in vascular smooth muscle cell adhesive strength and locomotion by modulating cell surface heparan sulfate,matrix interactionsJOURNAL OF CELLULAR PHYSIOLOGY, Issue 2 2001John H. Chon PR-39 is proline-rich peptide produced at sites of tissue injury. While the functional properties of this peptide have not been fully defined, PR-39 may be an important regulator of processes related to cell-matrix adhesion since it reportedly upregulates syndecan-4, which is a critical determinant of focal adhesion formation. The ability of PR-39 to modulate the adhesion and chemokinetic migration behavior of arterial smooth muscle cells (SMCs) in a fashion coordinated with syndecan-4 expression was investigated. Treatment of SMCs with PR-39 did not alter syndecan-1 mRNA, but did induce a two-fold increase in syndecan-4 mRNA (P,<,0.0001) and significantly enhanced cell surface expression of both syndecan-4 (P,<,0.01) and heparan sulfate (HS) (P,<,0.05). These observations were consistent with an observed increase in cell-matrix adhesive strength (P,<,0.05) and a reduction in cell speed (P,<,0.01) on fibronectin-coated substrates. Incubation of PR-39 treated cells with a soluble fibronectin derived heparin-binding peptide, as a competitive inhibitor of heparan sulfate/matrix interactions, abolished these effects. These data suggest that PR-39 mediated alterations of cell adhesion and motility may be related, in part, to the increased expression of heparan sulfate glycosaminoglycans (GAGs) that accompany the upregulation of cell surface syndecan-4. Futhermore, this investigation supports the notion that factors which control syndecan-4 expression may play an important role in regulating adhesion related cell processes. © 2001 Wiley-Liss, Inc. [source] Treatment of cartilage with ,-aminopropionitrile accelerates subsequent collagen maturation and modulates integrative repairJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 3 2005Kevin B. McGowan Abstract Integrative repair of cartilage was previously found to depend on collagen synthesis and maturation. ,-aminopropionitrile (BAPN) treatment, which irreversibly blocks lysyl oxidase, inhibited the formation of collagen crosslinks, prevented development of adhesive strength, and caused a buildup of GuHCl-extractable collagen crosslink precursors. This buildup of crosslink precursor in the tissue may be useful for enhancing integrative repair. We tested in vitro the hypothesis that pre-treatment of cartilage with BAPN, followed by washout before implantation, could be a useful therapeutic strategy to accelerate subsequent collagen maturation. In individual cartilage disks, collagen processing was reversibly blocked by BAPN treatment (0.1 mM) as indicated by a BAPN-induced increase in the total and proportion of incorporated radiolabel that was extractable by 4 M guanidine-HCl, followed by a decrease, within 3,4 days of BAPN washout, in the proportion of extractable radiolabel to control levels. With a similar pattern, integration between pairs of apposed cartilage blocks was reversibly blocked by BAPN treatment, and followed by an enhancement of integration after BAPN washout. The low and high levels of integration were associated with enrichment in [3H]proline in a form that was susceptible and resistant, respectively, to extraction. With increasing duration up to 7 days after BAPN pre-treatment, the levels of [3H]proline extraction decreased, and the development of adhesive strength increased. Thus, BAPN can be used to modulate integrative cartilage repair. © 2004 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved. [source] Effect of hybrid network formation on adhesion properties of polycyanurate/polyurethane semi-interpenetrating polymer networksPOLYMER ENGINEERING & SCIENCE, Issue 12 2002O. Grigoryeva The adhesion characteristics of modified polycyanurates based on the principle of semi-interpenetrating polymer networks (semi-IPNs) have been studied. It has been shown that the formation of a polycyanurate network in the presence of linear polyurethane (LPU) leads to increasing adhesion strength to aluminum and titanium. The peculiarities of polycyanurate network (PCN) formation in the presence of different amounts of LPU are discussed. It has been found that chemical incorporation of LPU into PCN occurs during network formation owing to chemical interaction of urethane groups with cyanate groups of growing PCN. At LPU content in the initial composition up to around 20 wt% only a hybrid network is formed. The maximal values of adhesive strength to aluminum and titanium are achieved at LPU content of 20,25%, corresponding to formation of a hybrid network. The further increase of LPU content leads to the presence of non-incorporated LPU (semi-IPN formation) in the adhesive layer and to reduction of the adhesive strength. [source] Steroid hormones strongly support bovine articular cartilage integration in the absence of interleukin-1,ARTHRITIS & RHEUMATISM, Issue 12 2006Carsten Englert Objective Posttraumatic integration of articular cartilage at fracture sites is essential for mechanical stability of cartilage, and ruptured cartilage is a prerequisite for early osteoarthritis. This study was undertaken to investigate effects on articular cartilage integration mediated by steroid hormones, interleukin-1, (IL-1,), and combinations thereof. Methods Articular cartilage blocks were cultured in partial apposition for 2 weeks with ascorbic acid, testosterone, 17,-estradiol, and dehydroepiandrosterone (DHEA), with or without IL-1,. Mechanical integration was measured as adhesive strength, i.e., the maximum force at rupture of integrated cartilage blocks divided by the overlap area. Glycosaminoglycan content was used to study synthesized extracellular matrix. Results Culture in medium without supplements did not lead to integration (adhesive strength 0 kPa). With administration of ascorbic acid (100 ,g/ml), the median adhesive strength was 49 kPa. In comparison with ascorbic acid alone, all steroid hormones induced a strong, concentration-dependent stimulation of integration (with maximum values observed with DHEA at 3 × 10,5M, testosterone at 10,8M, and 17,-estradiol at 10,11M). For testosterone and 17,-estradiol, this was also reflected by an increase of glycosaminoglycan content. Adhesive strength was increased with IL-1, at 10 pg/ml, but not at 1 pg/ml or 100 pg/ml. In the presence of both IL-1, and sex hormones, integration of articular cartilage was reduced. Conclusion This is the first study to demonstrate that steroid hormones such as 17,-estradiol, DHEA, and testosterone stimulate articular cartilage integration. This effect is abrogated by low concentrations of IL-1,. In the absence of IL-1, or after neutralization of IL-1,, steroid hormones might be favorable adjuvant compounds to optimize cartilage integration. [source] Click chemistry in materials synthesis.JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2007Abstract 1,2,3-Triazole-based polymers generated from the Cu(I)-catalyzed cycloaddition between multivalent azides and acetylenes are effective adhesive materials for metal surfaces. The adhesive capacities of candidate mixtures of azide and alkyne components were measured by a modified peel test, using a customized adhesive tester. A particularly effective tetravalent alkyne and trivalent azide combination was identified, giving exceptional strength that matches or exceeds the best commercial formulations. The addition of Cu catalyst was found to be important for the synthesis of stronger adhesive polymers when cured at room temperature. Heating also accelerated curing rates, but the maximum adhesive strengths achieved at both room temperature and high temperature were the same, suggesting that crosslinking reaches the same advanced point in all cases. Polytriazoles also form adhesives to aluminum, but copper is bound more effectively, presumably because active Cu(I) ions may be leached from the surface to promote crosslinking and adhesion. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5182,5189, 2007 [source] Preliminary study of laser welding for aortic dissection in a porcine model using a diode laser with indocyanine greenLASERS IN SURGERY AND MEDICINE, Issue 5 2003Masanori Fujita MD Abstract Background and Objectives The objective of this study was to determine whether a dissected aorta could be welded by a diode laser with a solder using an in vitro porcine aortic dissection model. Study Design/Materials and Methods Porcine aortic strips were dissected into two flaps and the dissected faces were immersed in a solution of indocyanine green. The two flaps were pressed at 0.2 kg/cm2 with contact between the two immersed faces. The pressed flaps were irradiated with a diode laser (810 nm) at intensities of 170,425 W/cm2 for 8 seconds. The welded flaps were studied by light microscopy and the adhesive strengths were measured. Results The irradiated flaps were successfully welded. The breaking stress, the maximum stress recorded in a stress-strain curve, increased with increase in irradiation intensity up to 396 W/cm2 (2.7,×,102 mmHg) and decreased when the intensity reached 425 W/cm2. In the specimen irradiated at 396 W/cm2, the welded faces showed continuous fusion of elastin layers, while some voids were seen between the welded faces in the specimen irradiated at 425 W/cm2. Conclusions The dissected porcine aortas were successfully welded using a laser with solder. The results suggest that the welded aorta can bear physiological blood pressure. Lasers Surg. Med. 32:341,345, 2003. © 2003 Wiley-Liss, Inc. [source] | ||||||||||||||||