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  • 1.
    Aminlashgari, Nina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Höglund, Odd V
    Borg, Niklas
    Hakkarainen, Minna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Degradation profile and preliminary clinical testing of a resorbable device for ligation of blood vessels2013In: Acta Biomaterialia, ISSN 1742-7061, E-ISSN 1878-7568, Vol. 9, no 6, p. 6898-904Article in journal (Refereed)
    Abstract [en]

    A resorbable device for ligation of blood vessels was developed and tested in vitro to reveal the degradation profile of the device and to predict the clinical performance in terms of adequate mechanical support during a healing period of I week. In addition, preliminary clinical testing was performed that showed complete hemostasis and good tissue grip of renal arteries in five pigs. The device was made by injection molding of poly(glycolide-co-trimethylene carbonate) triblock copolymer, and it consisted of a case with a locking mechanism connected to a partly perforated flexible band. A hydrolytic degradation study was carried out for 7, 30 and 60 days in water and buffer medium, following the changes in mass, water absorption, pH and mechanical properties. A new rapid matrix-free laser desorption ionization-mass spectrometry (LDI-MS) method was developed for direct screening of degradation products released into the degradation medium. The combination of LDI-MS and electrospray ionization-mass spectrometry analyses enabled the comparison of the degradation product patterns in water and buffer medium. The identified degradation products were rich in trimethylene carbonate units, indicating preferential hydrolysis of amorphous regions where trimethylene units are located. The crystallinity of the material was doubled after 60 days of hydrolysis, additionally confirming the preferential hydrolysis of trimethylene carbonate units and the enrichment of glycolide units in the remaining solid matrix. The mechanical performance of the perforated band was followed for the first week of hydrolysis and the results suggest that sufficient strength is retained during the healing time of the blood vessels.

  • 2.
    Gasser, T. Christian
    et al.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Biomechanics.
    Gallinetti, Sara
    Xing, Xiao
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Biomechanics.
    Forsell, Caroline
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Biomechanics.
    Swedenborg, Jesper
    Roy, Joy
    Spatial orientation of collagen fibers in the abdominal aortic aneurysm's wall and its relation to wall mechanics2012In: Acta Biomaterialia, ISSN 1742-7061, E-ISSN 1878-7568, Vol. 8, no 8, p. 3091-3103Article in journal (Refereed)
    Abstract [en]

    Collagen is the most abundant protein in mammals and provides the abdominal aortic aneurysm (AAA) wall with mechanical strength, stiffness and toughness. Specifically, the spatial orientation of collagen fibers in the wall has a major impact on its mechanical properties. Apart from valuable microhistological information, this data can be integrated by histomechanical constitutive models thought to improve biomechanical simulations, i.e. to improve the biomechanical rupture risk assessment of AAAs. Tissue samples (n = 24) from the AAA wall were harvested during elective AAA repair, fixated, embedded, sectioned and investigated by polarized light microscopy. The birefringent properties of collagen were reinforced by picrosirius red staining and the three-dimensional collagen fiber orientations were identified with a universal rotary stage. Two constitutive models for collagen fibers were used to integrate the identified structural information in a macroscopic AAA wall model. The collagen fiber orientation in the AM wall was widely dispersed and could be captured by a Bingham distribution function (kappa(1) = 11.6, kappa(2) = 9.7). The dispersion was much larger in the tangential plane than in the cross-sectional plane, and no significant difference between the medial and adventitial layers could be identified. The layered directional organization of collagen in normal aortas was not evident in the AAA. The collagen organization identified, combined with constitutive descriptions of collagen fibers that depend on its orientation, explain the anisotropic (orthotropic) mechanical properties of the AAA wall. The mechanical properties of collagen fibers depend largely on their undulation, which is an important structural parameter that requires further experimental investigation.

  • 3.
    Guo, Baolin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Sun, Yang
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Finne-Wistrand, Anna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Mustafa, Kamal
    Albertsson, Ann-Christine
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Electroactive porous tubular scaffolds with degradability and non-cytotoxicity for neural tissue regeneration2011In: Acta Biomaterialia, ISSN 1742-7061, E-ISSN 1878-7568, Vol. 8, no 1, p. 144-153Article in journal (Refereed)
    Abstract [en]

    Electroactive degradable porous tubular scaffolds were fabricated from the blends of polycaprolactone and a hyperbranched degradable conducting copolymer at different feed ratios by a solution-casting/salt-leaching method. Scaning electron microscopy (SEM) and microcomputed tomography tests indicated that these scaffolds had homogeneously distributed interconnected pores on the cross-section and surface. The electrical conductivity of films with the same composition as the scaffolds was between 3.4×10(-6) and 3.1×10(-7)Scm(-1), depending on the ratio of hyperbranched degradable conducting copolymer to polycaprolactone. A hydrophilic surface with a contact angle of water about 30° was achieved by doping the films with (±)-10-camphorsulfonic acid. The mechanical properties of the films were investigated by tensile tests, and the morphology of the films was studied by SEM. The scaffolds were subjected to the WST test (a cell proliferation and cytotoxicity assay using water-soluble tetrazolium salts) with HaCaT keratinocyte cells, and the results show that these scaffolds are non-cytotoxic. These degradable electroactive tubular scaffolds are good candidates for neural tissue engineering application.

  • 4.
    Holzapfel, Gerhard A.
    et al.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.). Institute of Biomechanics, Center of Biomedical Engineering, Graz University of Technology, Austria .
    Ogden, Ray W.
    Elasticity of biopolymer filaments2013In: Acta Biomaterialia, ISSN 1742-7061, E-ISSN 1878-7568, Vol. 9, no 7, p. 7320-7325Article in journal (Refereed)
    Abstract [en]

    Within the general one-dimensional theory of nonlinear elasticity we analyze the elasticity of biopolymer filaments. The approach adopted is purely mechanical but is reconciled with statistical physics approaches and allows for a proper formulation of boundary-value problems. By specializing the general framework we obtain force-extension relations for inextensible filaments and show how previous work on the biophysics of filaments fits within the framework. On the other hand, within the same framework, the theory of extensible filaments, which is appropriate for semi-flexible filaments such as F-actin, enables us to fit representative F-actin data. The specific formulas derived are relatively simple and the parameters involved have direct mechanical interpretations and are immediately related to the filament properties, including the initial end-to-end length, contour length and persistence length.

  • 5.
    Paulraj, T.
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Riazanova, A. V.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Svagan, A. J.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. KTH Royal Inst Technol, Wallenberg Wood Sci Ctr, SE-10044 Stockholm, Sweden. KTH Royal Inst Technol, Dept Fiber & Polymer Technol, SE-10044 Stockholm, Sweden..
    Bioinspired capsules based on nanocellulose, xyloglucan and pectin - The influence of capsule wall composition on permeability properties2018In: Acta Biomaterialia, ISSN 1742-7061, E-ISSN 1878-7568, Vol. 69, p. 196-205Article in journal (Refereed)
    Abstract [en]

    Materials based on renewable biopolymers, selective permeability and stimuli-responsive release/loading properties play an important role in biomedical applications. Here, in order to mimic the plant primary cell-wall, microcapsules have been fabricated using cell wall polysaccharides, namely pectin, xyloglucan and cellulose nanofibers. For the first time, a large amount of xyloglucan was successfully included in such capsules. These capsules demonstrated stimuli-responsive (ON/OFF) permeability and biocompatibility. The live cell staining revealed that the microcapsules' surface enhanced cell growth and also the non-toxic nature of the microcapsules. In water, the microcapsules were completely and partially permeable to fluorescent dextrans with an average molecular weight of 70 kDa (hydrodynamic diameter of ca. 12 nm) and 2000 kDa (ca. 54 nm), respectively. On the other hand, the permeability dropped quickly when the capsules were exposed to 250 mM NaCl solution, trapping a fraction of the 70 kDa dextrans in the capsule interior. The decrease in permeability was a direct consequence of the capsule-wall composition, i.e. the presence of xyloglucan and a low amount of charged molecules such as pectin. The low permeability of capsules in saline conditions (and in a model biological medium), combined with a capsule wall that is made from dietary fibers only, potentially enables their use in biological applications, such as colon targeted delivery in the gastro-intestinal tract. 

  • 6. Polzer, S.
    et al.
    Gasser, Christian
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Biomechanics.
    Novak, K.
    Man, V.
    Tichy, M.
    Skacel, P.
    Bursa, J.
    Structure-based constitutive model can accurately predict planar biaxial properties of aortic wall tissue2015In: Acta Biomaterialia, ISSN 1742-7061, E-ISSN 1878-7568, Vol. 14, p. 133-145Article in journal (Refereed)
    Abstract [en]

    Structure-based constitutive models might help in exploring mechanisms by which arterial wall histology is linked to wall mechanics. This study aims to validate a recently proposed structure-based constitutive model. Specifically, the model's ability to predict mechanical biaxial response of porcine aortic tissue with predefined collagen structure was tested. Histological slices from porcine thoracic aorta wall (n = 9) were automatically processed to quantify the collagen fiber organization, and mechanical testing identified the non-linear properties of the wall samples (n = 18) over a wide range of biaxial stretches. Histological and mechanical experimental data were used to identify the model parameters of a recently proposed multi-scale constitutive description for arterial layers. The model predictive capability was tested with respect to interpolation and extrapolation. Collagen in the media was predominantly aligned in circumferential direction (planar von Mises distribution with concentration parameter b(M) = 1.03 +/- 0.23), and its coherence decreased gradually from the luminal to the abluminal tissue layers (inner media, b = 1.54 +/- 0.40; outer media, b = 0.72 +/- 0.20). In contrast, the collagen in the adventitia was aligned almost isotropically (b(A) = 0.27 +/- 0.11), and no features, such as families of coherent fibers, were identified. The applied constitutive model captured the aorta biaxial properties accurately (coefficient of determination R-2 = 0.95 +/- 0.03) over the entire range of biaxial deformations and with physically meaningful model parameters. Good predictive properties, well outside the parameter identification space, were observed (R-2 = 0.92 +/- 0.04). Multi-scale constitutive models equipped with realistic micro-histological data can predict macroscopic non-linear aorta wall properties. Collagen largely defines already low strain properties of media, which explains the origin of wall anisotropy seen at this strain level. The structure and mechanical properties of adventitia are well designed to protect the media from axial and circumferential overloads.

  • 7. Saez, P.
    et al.
    Garcia, A.
    Pena, E.
    Gasser, T. Christian
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Martinez, M. A.
    Microstructural quantification of collagen fiber orientations and its integration in constitutive modeling of the porcine carotid artery2016In: Acta Biomaterialia, ISSN 1742-7061, E-ISSN 1878-7568, Vol. 33, p. 183-193Article in journal (Refereed)
    Abstract [en]

    Background: Mechanical characteristics of vascular tissue may play a role in different arterial pathologies, which, amongst others, requires robust constitutive descriptions to capture the vessel wall's anisotropic and non-linear properties.Specifically, the complex 3D network of collagen and its interaction with other structural elements has a dominating effect of arterial properties at higher stress levels.The aim of this study is to collect quantitative collagen organization as well as mechanical properties to facilitate structural constitutive models for the porcine carotid artery.This helps the understanding of the mechanics of swine carotid arteries, being a standard in clinical hypothesis testing, in endovascular preclinical trials for example. Method: Porcine common carotid arteries (n = 10) were harvested and used to (i) characterize the collagen fiber organization with polarized light microscopy, and (ii) the biaxial mechanical properties by inflation testing.The collagen organization was quantified by the Bingham orientation density function (ODF), which in turn was integrated in a structural constitutive model of the vessel wall.A one-layered and thick-walled model was used to estimate mechanical constitutive parameters by least-square fitting the recorded in vitro inflation test results.Finally, uniaxial data published elsewhere were used to validate the mean collagen organization described by the Bingham ODF. Results: Thick collagen fibers, i.e.the most mechanically relevant structure, in the common carotid artery are dispersed around the circumferential direction.In addition, almost all samples showed two distinct families of collagen fibers at different elevation, but not azimuthal, angles.Collagen fiber organization could be accurately represented by the Bingham ODF (kappa(1,2,3) = [13.5, 0.0, 25.2] and kappa(1,2,3) = [14.7, 0.0,26.6]; average error of about 5%), and their integration into a structural constitutive model captured the inflation characteristics of individual carotid artery samples.Specifically, only four mechanical parameters were required to reasonably (average error from 14% to 38%) cover the experimental data over a wide range of axial and circumferential stretches.However, it was critical to account for fibrilar links between thick collagen fibers.Finally, the mean Bingham ODF provide also good approximation to uniaxial experimental data. Conclusions: The applied structural constitutive model, based on individually measured collagen orientation densities, was able to capture the biaxial properties of the common carotid artery. Since the model required coupling amongst thick collagen fibers, the collagen fiber orientations measured from polarized light microscopy, alone, seem to be insufficient structural information. Alternatively, a larger dispersion of collagen fiber orientations, that is likely to arise from analyzing larger wall sections, could have had a similar effect, i.e. could have avoided coupling amongst thick collagen fibers. Statement of Significance The applied structural constitutive model, based on individually measured collagen orientation densities, was able to capture the biaxial and uniaxial properties of the common carotid artery. Since the model required coupling amongst thick collagen fibers, an effective orientation density that accounts for cross links between the main collagen fibers has been porposed. The model provides a good approximation to the experimental data.

  • 8. Shi, J.
    et al.
    Hedberg, Yolanda
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Lundin, Maria
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Odnevall Wallinder, Inger
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Karlsson, H. L.
    Möller, L.
    Hemolytic properties of synthetic nano- and porous silica particles: The effect of surface properties and the protection by the plasma corona2012In: Acta Biomaterialia, ISSN 1742-7061, E-ISSN 1878-7568, Vol. 8, no 9, p. 3478-3490Article in journal (Refereed)
    Abstract [en]

    Novel silica materials incorporating nanotechnology are promising materials for biomedical applications, but their novel properties may also bring unforeseen behavior in biological systems. Micro-size silica is well documented to induce hemolysis, but little is known about the hemolytic activities of nanostructured silica materials. In this study, the hemolytic properties of synthetic amorphous silica nanoparticles with primary sizes of 7-14 nm (hydrophilic vs. hydrophobic), 5-15 nm, 20 nm and 50 nm, and model meso/macroporous silica particles with pore diameters of 40 nm and 170 nm are investigated. A crystalline silica sample (0.5-10 ÎŒm) is included for benchmarking purposes. Special emphasis is given to investigations of how the temperature and solution complexity (solvent, plasma), as well as the physicochemical properties (such as size, surface charge, hydrophobicity and other surface properties), link to the hemolytic activities of these particles. Results suggests the potential importance of small size and large external surface area, as well as surface charge/structure, in the hemolysis of silica particles. Furthermore, a significant correlation is observed between the hemolytic profile of red blood cells and the cytotoxicity profile of human promyelocytic leukemia cells (HL-60) induced by nano- and porous silica particles, suggesting a potential universal mechanism of action. Importantly, the results generated suggest that the protective effect of plasma towards silica nanoparticle-induced hemolysis as well as cytotoxicity is primarily due to the protein/lipid layer shielding the silica particle surface. These results will assist the rational design of hemocompatible silica particles for biomedical applications.

  • 9. Sommer, G.
    et al.
    Eder, M.
    Kovacs, L.
    Pathak, H.
    Bonitz, L.
    Mueller, C.
    Regitnig, P.
    Holzapfel, Gerhard
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.). Institute of Biomechanics, Center of Biomedical Engineering, Graz University of Technology, Austria.
    Multiaxial mechanical properties and constitutive modeling of human adipose tissue: A basis for preoperative simulations in plastic and reconstructive surgery2013In: Acta Biomaterialia, ISSN 1742-7061, E-ISSN 1878-7568, Vol. 9, no 11, p. 9036-9048Article in journal (Refereed)
    Abstract [en]

    A preoperative simulation of soft tissue deformations during plastic and reconstructive surgery is desirable to support the surgeon's planning and to improve surgical outcomes. The current development of constitutive adipose tissue models, for the implementation in multilayer computational frameworks for the simulation of human soft tissue deformations, has proved difficult because knowledge of the required mechanical parameters of fat tissue is limited. Therefore, for the first time, human abdominal adipose tissues were mechanically investigated by biaxial tensile and triaxial shear tests. The results of this study suggest that human abdominal adipose tissues under quasi-static and dynamic multiaxial loadings can be characterized as a nonlinear, anisotropic and viscoelastic soft biological material. The nonlinear and anisotropic features are consequences of the material's collagenous microstructure. The aligned collagenous septa observed in histological investigations causes the anisotropy of the tissue. A hyperelastic model used in this study was appropriate to represent the quasi-static multiaxial mechanical behavior of fat tissue. The constitutive parameters are intended to serve as a basis for soft tissue simulations using the finite element method, which is an apparent method for obtaining promising results in the field of plastic and reconstructive surgery.

  • 10. Sommer, Gerhard
    et al.
    Schriefl, Andreas
    Zeindlinger, Georg
    Katzensteiner, Andreas
    Ainoedhofer, Herwig
    Saxena, Amulya
    Holzapfel, Gerhard A.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Multiaxial mechanical response and constitutive modeling of esophageal tissues: Impact on esophageal tissue engineering2013In: Acta Biomaterialia, ISSN 1742-7061, E-ISSN 1878-7568, Vol. 9, no 12, p. 9379-9391Article in journal (Refereed)
    Abstract [en]

    Congenital defects of the esophagus are relatively frequent, with 1 out of 2500 babies suffering from such a defect. A new method of treatment by implanting tissue engineered esophagi into newborns is currently being developed and tested using ovine esophagi. For the reconstruction of the biological function of native tissues with engineered esophagi, their cellular structure as well as their mechanical properties must be considered. Since very limited mechanical and structural data for the esophagus are available, the aim of this study was to investigate the multiaxial mechanical behavior of the ovine esophagus and the underlying microstructure. Therefore, uniaxial tensile, biaxial tensile and extension-inflation tests on esophagi were performed. The underlying microstructure was examined in stained histological sections through standard optical microscopy techniques. Moreover, the uniaxial ultimate tensile strength and residual deformations of the tissue were determined. Both the mucosa-submucosa and the muscle layers showed nonlinear and anisotropic mechanical behavior during uniaxial, biaxial and inflation testing. Cyclical inflation of the intact esophageal tube caused marked softening of the passive esophagi in the circumferential direction. The rupture strength of the mucosa-submucosa layer was much higher than that of the muscle layer. Overall, the ovine esophagus showed a heterogeneous and anisotropic behavior with different mechanical properties for the individual layers. The intact and layer-specific multiaxial properties were characterized using a well-known three-dimensional microstructurally based strain-energy function. This novel and complete set of data serves the basis for a better understanding of tissue remodeling in diseased esophagi and can be used to perform computer simulations of surgical interventions or medical-device applications.

  • 11.
    Törne, Karin
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Ornberg, Andreas
    Weissenrieder, Jonas
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Influence of strain on the corrosion of magnesium alloys and zinc in physiological environments2017In: Acta Biomaterialia, ISSN 1742-7061, E-ISSN 1878-7568, Vol. 48, p. 541-550Article in journal (Refereed)
    Abstract [en]

    During implantation load-bearing devices experience stress that may influence its mechanical and corrosion profile and potentially lead to premature rupture. The susceptibility to stress corrosion cracking (SCC) of the Mg-Al alloy AZ61 and Zn was studied in simulated body fluid (m-SBF) and whole blood by slow strain rate (SSR) testing in combination with electrochemical impedance spectroscopy (EIS) and further ex situ analysis including scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy. AZ61 was found to be highly susceptible to SCC. EIS analysis show that although the majority of cracking occurred during the apparent plastic straining, cracking initiation occurs already in the elastic region at similar to 50% of the ultimate tensile strength (UTS). Shifts in EIS phase angle and open circuit potential can be used to detect the onset of SCC. Zinc demonstrated a highly ductile behavior with limited susceptibility to SCC. No significant decrease in UTS was observed in m-SBF but a decrease in time to failure by similar to 25% compared to reference samples indicates some effect on the mechanical properties during the ductile straining. The formation of micro cracks, similar to 10 mu m deep, was indicated by the EIS analysis and later confirmed by ex situ SEM. The results of SSR analysis of zinc in whole blood showed a reduced effect compared to m-SBF and no cracks were detected. It appears that formation of an organic surface layer protects the corroding surface from cracking. These results highlight the importance of considering the effect of biological species on the degradation of implants in the clinical situation. Statement of Significance Strain may deteriorate the corrosion properties of metallic implants drastically. We study the influence of load on the corrosion properties of a magnesium alloy and zinc by a combination of electrochemical impedance spectroscopy (EIS) and slow strain rate analysis. This combination of techniques has previously not been used for studying degradation in physiological relevant electrolytes. EIS provide valuable information on the initial formation of cracks, detecting crack nucleation before feasible in slow strain rate analysis. This sensitivity of EIS shows the potential for electrochemical methods to be used for in situ monitoring crack formation of implants in more applied studies.

  • 12. Unterberger, Michael J.
    et al.
    Schmoller, Kurt M.
    Wurm, Christine
    Bausch, Andreas R.
    Holzapfel, Gerhard A.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.). Graz University of Technology, Austria .
    Viscoelasticity of cross-linked actin networks: Experimental tests, mechanical modeling and finite-element analysis2013In: Acta Biomaterialia, ISSN 1742-7061, E-ISSN 1878-7568, Vol. 9, no 7, p. 7343-7353Article in journal (Refereed)
    Abstract [en]

    Filamentous actin is one of the main constituents of the eukaryotic cytoskeleton. The actin cortex, a densely cross-linked network, resides underneath the lipid bilayer. In the present work we propose a continuum mechanical formulation for describing the viscoelastic properties of in vitro actin networks, which serve as model systems for the cortex, by including the microstructure, i.e. the behavior of a single filament and its spatial arrangement. The modeling of the viscoelastic response in terms of physically interpretable parameters is conducted using a multiscale approach consisting of two steps: modeling of the single filament response of F-actin by a worm-like chain model including the extensibility of the filament, and assembling the three-dimensional biopolymer network by using the microsphere model which accounts for filaments equally distributed in space. The viscoelastic effects of the network are taken into account using a generalized Maxwell model. The Cauchy stress and elasticity tensors are obtained within a continuum mechanics framework and implemented into a finite-element program. The model is validated on the network level using large strain experiments on reconstituted actin gels. Comparisons of the proposed model with rheological experiments recover reasonable values for the material parameters. Finite-element simulations of the indentation of a sphere on a network slab and the aspiration of a droplet in a micropipette allow for further insights of the viscoelastic behavior of actin networks.

  • 13. Xiang, T.
    et al.
    Lu, T.
    Xie, Y.
    Zhao, Weifeng
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology. State Key Laboratory of Polymer Materials Engineering, Sichuan University, China.
    Sun, S. -D
    Zhao, C. -S
    Zwitterionic polymer functionalization of polysulfone membrane with improved antifouling property and blood compatibility by combination of ATRP and click chemistry2016In: Acta Biomaterialia, ISSN 1742-7061, E-ISSN 1878-7568, Vol. 40, p. 162-171Article in journal (Refereed)
    Abstract [en]

    The chemical compositions are very important for designing blood-contacting membranes with good antifouling property and blood compatibility. In this study, we propose a method combining ATRP and click chemistry to introduce zwitterionic polymer of poly(sulfobetaine methacrylate) (PSBMA), negatively charged polymers of poly(sodium methacrylate) (PNaMAA) and/or poly(sodium p-styrene sulfonate) (PNaSS), to improve the antifouling property and blood compatibility of polysulfone (PSf) membranes. Attenuated total reflectance-Fourier transform infrared spectra, X-ray photoelectron spectroscopy and water contact angle results confirmed the successful grafting of the functional polymers. The antifouling property and blood compatibility of the modified membranes were systematically investigated. The zwitterionic polymer (PSBMA) grafted membranes showed good resistance to protein adsorption and bacterial adhesion; the negatively charged polymer (PNaSS or PNaMAA) grafted membranes showed improved blood compatibility, especially the anticoagulant property. Moreover, the PSBMA/PNaMAA modified membrane showed both antifouling property and anticoagulant property, and exhibited a synergistic effect in inhibiting blood coagulation. The functionalization of membrane surfaces by a combination of ATRP and click chemistry is demonstrated as an effective route to improve the antifouling property and blood compatibility of membranes in blood-contact.

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