@article{BrauneGrossWalteretal.2016, author = {Braune, Steffen and Gross, M. and Walter, M. and Zhou, Shengqiang and Dietze, Siegfried and Rutschow, S. and Lendlein, Andreas and Tschoepe, C. and Jung, Friedrich}, title = {Adhesion and activation of platelets from subjects with coronary artery disease and apparently healthy individuals on biomaterials}, series = {Journal of biomedical materials research : an official journal of the Society for Biomaterials, the Japanese Society for Biomaterials; the Australian Society for Biomaterials}, volume = {104}, journal = {Journal of biomedical materials research : an official journal of the Society for Biomaterials, the Japanese Society for Biomaterials; the Australian Society for Biomaterials}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {1552-4973}, doi = {10.1002/jbm.b.33366}, pages = {210 -- 217}, year = {2016}, abstract = {On the basis of the clinical studies in patients with coronary artery disease (CAD) presenting an increased percentage of activated platelets, we hypothesized that hemocompatibility testing utilizing platelets from healthy individuals may result in an underestimation of the materials' thrombogenicity. Therefore, we investigated the interaction of polymer-based biomaterials with platelets from CAD patients in comparison to platelets from apparently healthy individuals. In vitro static thrombogenicity tests revealed that adherent platelet densities and total platelet covered areas were significantly increased for the low (polydimethylsiloxane, PDMS) and medium (Collagen) thrombogenic surfaces in the CAD group compared to the healthy subjects group. The area per single platelet—indicating the spreading and activation of the platelets—was markedly increased on PDMS treated with PRP from CAD subjects. This could not be observed for collagen or polytetrafluoroethylene (PTFE). For the latter material, platelet adhesion and surface coverage did not differ between the two groups. Irrespective of the substrate, the variability of these parameters was increased for CAD patients compared to healthy subjects. This indicates a higher reactivity of platelets from CAD patients compared to the healthy individuals. Our results revealed, for the first time, that utilizing platelets from apparently healthy donors bears the risk of underestimating the thrombogenicity of polymer-based biomaterials.}, language = {en} } @misc{BrauneLatourReinthaleretal.2019, author = {Braune, Steffen and Latour, Robert A. and Reinthaler, Markus and Landmesser, Ulf and Lendlein, Andreas and Jung, Friedrich}, title = {In Vitro Thrombogenicity Testing of Biomaterials}, series = {Advanced healthcare materials}, volume = {8}, journal = {Advanced healthcare materials}, number = {21}, publisher = {Wiley}, address = {Hoboken}, issn = {2192-2640}, doi = {10.1002/adhm.201900527}, pages = {17}, year = {2019}, abstract = {The short- and long-term thrombogenicity of implant materials is still unpredictable, which is a significant challenge for the treatment of cardiovascular diseases. A knowledge-based approach for implementing biofunctions in materials requires a detailed understanding of the medical device in the biological system. In particular, the interplay between material and blood components/cells as well as standardized and commonly acknowledged in vitro test methods allowing a reproducible categorization of the material thrombogenicity requires further attention. Here, the status of in vitro thrombogenicity testing methods for biomaterials is reviewed, particularly taking in view the preparation of test materials and references, the selection and characterization of donors and blood samples, the prerequisites for reproducible approaches and applied test systems. Recent joint approaches in finding common standards for a reproducible testing are summarized and perspectives for a more disease oriented in vitro thrombogenicity testing are discussed.}, language = {en} } @article{BrauneWalterSchulzeetal.2014, author = {Braune, Steffen and Walter, M. and Schulze, F. and Lendlein, Andreas and Jung, Friedrich}, title = {Changes in platelet morphology and function during 24 hours of storage}, series = {Clinical hemorheology and microcirculation : blood flow and vessels}, volume = {58}, journal = {Clinical hemorheology and microcirculation : blood flow and vessels}, number = {1}, publisher = {IOS Press}, address = {Amsterdam}, issn = {1386-0291}, doi = {10.3233/CH-141876}, pages = {159 -- 170}, year = {2014}, abstract = {For in vitro studies assessing the interaction of platelets with implant materials, common and standardized protocols for the preparation of platelet rich plasma (PRP) are lacking, which may lead to non-matching results due to the diversity of applied protocols. Particularly, the aging of platelets during prolonged preparation and storage times is discussed to lead to an underestimation of the material thrombogenicity. Here, we study the influence of whole blood-and PRP-storage times on changes in platelet morphology and function. Whole blood PFA100 closure times increased after stimulation with collagen/ADP and collagen/epinephrine. Twenty four hours after blood collection, both parameters were prolonged pathologically above the upper limit of the reference range. Numbers of circulating platelets, measured in PRP, decreased after four hours, but no longer after twenty four hours. Mean platelet volumes (MPV) and platelet large cell ratios (P-LCR, 12 fL - 40 fL) decreased over time. Immediately after blood collection, no debris or platelet aggregates could be visualized microscopically. After four hours, first debris and very small aggregates occurred. After 24 hours, platelet aggregates and also debris progressively increased. In accordance to this, the CASY system revealed an increase of platelet aggregates (up to 90 mu m diameter)with increasing storage time. The percentage of CD62P positive platelets and PF4 increased significantly with storage time in resting PRP. When soluble ADP was added to stored PRP samples, the number of activatable platelets decreased significantly over storage time. The present study reveals the importance of a consequent standardization in the preparation of WB and PRP. Platelet morphology and function, particularly platelet reactivity to adherent or soluble agonists in their surrounding milieu, changed rapidly outside the vascular system. This knowledge is of crucial interest, particularly in the field of biomaterial development for cardiovascular applications, and may help to define common standards in the in vitro hemocompatibility testing of biomaterials.}, language = {en} } @article{DegtyarHarringtonPolitietal.2014, author = {Degtyar, Elena and Harrington, Matthew J. and Politi, Yael and Fratzl, Peter}, title = {The mechanical role of metal ions in biogenic protein-based materials}, series = {Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition}, volume = {53}, journal = {Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition}, number = {45}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1433-7851}, doi = {10.1002/anie.201404272}, pages = {12026 -- 12044}, year = {2014}, abstract = {Protein-metal interactions-traditionally regarded for roles in metabolic processes-are now known to enhance the performance of certain biogenic materials, influencing properties such as hardness, toughness, adhesion, and self-healing. Design principles elucidated through thorough study of such materials are yielding vital insights for the design of biomimetic metallopolymers with industrial and biomedical applications. Recent advances in the understanding of the biological structure-function relationships are highlighted here with a specific focus on materials such as arthropod biting parts, mussel byssal threads, and sandcastle worm cement.}, language = {en} } @article{FedericoPiercePilusoetal.2015, author = {Federico, Stefania and Pierce, Benjamin F. and Piluso, Susanna and Wischke, Christian and Lendlein, Andreas and Neffe, Axel T.}, title = {Design of Decorin-Based Peptides That Bind to CollagenI and their Potential as Adhesion Moieties in Biomaterials}, series = {Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition}, volume = {54}, journal = {Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition}, number = {37}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1433-7851}, doi = {10.1002/anie.201505227}, pages = {10980 -- 10984}, year = {2015}, abstract = {Mimicking the binding epitopes of protein-protein interactions by using small peptides is important for generating modular biomimetic systems. A strategy is described for the design of such bioactive peptides without accessible structural data for the targeted interaction, and the effect of incorporating such adhesion peptides in complex biomaterial systems is demonstrated. The highly repetitive structure of decorin was analyzed to identify peptides that are representative of the inner and outer surface, and it was shown that only peptides based on the inner surface of decorin bind to collagen. The peptide with the highest binding affinity for collagenI, LHERHLNNN, served to slow down the diffusion of a conjugated dye in a collagen gel, while its dimer could physically crosslink collagen, thereby enhancing the elastic modulus of the gel by one order of magnitude. These results show the potential of the identified peptides for the design of biomaterials for applications in regenerative medicine.}, language = {en} } @article{HardyBertinTorresRendonetal.2018, author = {Hardy, John G. and Bertin, Annabelle and Torres-Rendon, Jose Guillermo and Leal-Egana, Aldo and Humenik, Martin and Bauer, Felix and Walther, Andreas and C{\"o}lfen, Helmut and Schlaad, Helmut and Scheibel, Thomas R.}, title = {Facile photochemical modification of silk protein-based biomaterials}, series = {Macromolecular bioscience}, volume = {18}, journal = {Macromolecular bioscience}, number = {11}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1616-5187}, doi = {10.1002/mabi.201800216}, pages = {6}, year = {2018}, abstract = {Silk protein-based materials show promise for application as biomaterials for tissue engineering. The simple and rapid photochemical modification of silk protein-based materials composed of either Bombyx mori silkworm silk or engineered spider silk proteins (eADF4(C16)) is reported. Radicals formed on the silk-based materials initiate the polymerization of monomers (acrylic acid, methacrylic acid, or allylamine) which functionalize the surface of the silk materials with poly(acrylic acid) (PAA), poly(methacrylic acid) (PMAA), or poly(allylamine) (PAAm). To demonstrate potential applications of this type of modification, the polymer-modified silks are mineralized. The PAA- and PMAA-functionalized silks are mineralized with calcium carbonate, whereas the PAAm-functionalized silks are mineralized with silica, both of which provide a coating on the materials that may be useful for bone tissue engineering, which will be the subject of future investigations.}, language = {en} } @article{HardyTorresRendonLealEganaetal.2016, author = {Hardy, John G. and Torres-Rendon, Jose Guillermo and Leal-Egana, Aldo and Walther, Andreas and Schlaad, Helmut and Coelfen, Helmut and Scheibel, Thomas R.}, title = {Biomineralization of Engineered Spider Silk Protein-Based Composite Materials for Bone Tissue Engineering}, series = {Materials}, volume = {9}, journal = {Materials}, publisher = {MDPI}, address = {Basel}, issn = {1996-1944}, doi = {10.3390/ma9070560}, pages = {93 -- 108}, year = {2016}, abstract = {Materials based on biodegradable polyesters, such as poly(butylene terephthalate) (PBT) or poly(butylene terephthalate-co-poly(alkylene glycol) terephthalate) (PBTAT), have potential application as pro-regenerative scaffolds for bone tissue engineering. Herein, the preparation of films composed of PBT or PBTAT and an engineered spider silk protein, (eADF4(C16)), that displays multiple carboxylic acid moieties capable of binding calcium ions and facilitating their biomineralization with calcium carbonate or calcium phosphate is reported. Human mesenchymal stem cells cultured on films mineralized with calcium phosphate show enhanced levels of alkaline phosphatase activity suggesting that such composites have potential use for bone tissue engineering.}, language = {en} } @misc{HardyTorresRendonLealEganaetal.2017, author = {Hardy, John G. and Torres-Rendon, Jose Guillermo and Leal-Ega{\~n}a, Aldo and Walther, Andreas and Schlaad, Helmut and C{\"o}lfen, Helmut and Scheibel, Thomas R.}, title = {Biomineralization of engineered spider silk protein-based composite materials for bone tissue engineering}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-400519}, pages = {13}, year = {2017}, abstract = {Materials based on biodegradable polyesters, such as poly(butylene terephthalate) (PBT) or poly(butylene terephthalate-co-poly(alkylene glycol) terephthalate) (PBTAT), have potential application as pro-regenerative scaffolds for bone tissue engineering. Herein, the preparation of films composed of PBT or PBTAT and an engineered spider silk protein, (eADF4(C16)), that displays multiple carboxylic acid moieties capable of binding calcium ions and facilitating their biomineralization with calcium carbonate or calcium phosphate is reported. Human mesenchymal stem cells cultured on films mineralized with calcium phosphate show enhanced levels of alkaline phosphatase activity suggesting that such composites have potential use for bone tissue engineering.}, language = {en} } @misc{JungingerKuebelSchacheretal.2013, author = {Junginger, Mathias and K{\"u}bel, Christian and Schacher, Felix H. and M{\"u}ller, Axel H. E. and Taubert, Andreas}, title = {Crystal structure and chemical composition of biomimetic calcium phosphate nanofibers}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-95176}, pages = {11301 -- 11308}, year = {2013}, abstract = {Calcium phosphate nanofibers with a diameter of only a few nanometers and a cotton-ball-like aggregate morphology have been reported several times in the literature. Although fiber formation seems reproducible in a variety of conditions, the crystal structure and chemical composition of the fibers have been elusive. Using scanning transmission electron microscopy, low dose electron (nano)diffraction, energy-dispersive X-ray spectroscopy, and energy-filtered transmission electron microscopy, we have assigned crystal structures and chemical compositions to the fibers. Moreover, we demonstrate that the mineralization process yields true polymer/calcium phosphate hybrid materials where the block copolymer template is closely associated with the calcium phosphate.}, language = {en} } @article{LiuGouldRudolphetal.2020, author = {Liu, Yue and Gould, Oliver E. C. and Rudolph, Tobias and Fang, Liang and Kratz, Karl and Lendlein, Andreas}, title = {Polymeric microcuboids programmable for temperature-memory}, series = {Macromolecular materials and engineering}, volume = {305}, journal = {Macromolecular materials and engineering}, number = {10}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1438-7492}, doi = {10.1002/mame.202000333}, pages = {7}, year = {2020}, abstract = {Microobjects with programmable mechanical functionality are highly desirable for the creation of flexible electronics, sensors, and microfluidic systems, where fabrication/programming and quantification methods are required to fully control and implement dynamic physical behavior. Here, programmable microcuboids with defined geometries are prepared by a template-based method from crosslinked poly[ethylene-co-(vinyl acetate)] elastomers. These microobjects could be programmed to exhibit a temperature-memory effect or a shape-memory polymer actuation capability. Switching temperaturesT(sw)during shape recovery of 55 +/- 2, 68 +/- 2, 80 +/- 2, and 86 +/- 2 degrees C are achieved by tuning programming temperatures to 55, 70, 85, and 100 degrees C, respectively. Actuation is achieved with a reversible strain of 2.9 +/- 0.2\% to 6.7 +/- 0.1\%, whereby greater compression ratios and higher separation temperatures induce a more pronounced actuation. Micro-geometry change is quantified using optical microscopy and atomic force microscopy. The realization and quantification of microparticles, capable of a tunable temperature responsive shape-change or reversible actuation, represent a key development in the creation of soft microscale devices for drug delivery or microrobotics.}, language = {en} }