@article{LauLiuMaieretal.2021, author = {Lau, Skadi and Liu, Yue and Maier, Anna and Braune, Steffen and Gossen, Manfred and Neffe, Axel T. and Lendlein, Andreas}, title = {Establishment of an in vitro thrombogenicity test system with cyclic olefin copolymer substrate for endothelial layer formation}, series = {MRS communications / a publication of the Materials Research Society}, volume = {11}, journal = {MRS communications / a publication of the Materials Research Society}, number = {5}, publisher = {Springer}, address = {Berlin}, issn = {2159-6867}, doi = {10.1557/s43579-021-00072-6}, pages = {559 -- 567}, year = {2021}, abstract = {In vitro thrombogenicity test systems require co-cultivation of endothelial cells and platelets under blood flow-like conditions. Here, a commercially available perfusion system is explored using plasma-treated cyclic olefin copolymer (COC) as a substrate for the endothelial cell layer. COC was characterized prior to endothelialization and co-cultivation with platelets under static or flow conditions. COC exhibits a low roughness and a moderate hydrophilicity. Flow promoted endothelial cell growth and prevented platelet adherence. These findings show the suitability of COC as substrate and the importance of blood flow-like conditions for the assessment of the thrombogenic risk of drugs or cardiovascular implant materials.}, language = {en} } @article{TungSunWangetal.2021, author = {Tung, Wing Tai and Sun, Xianlei and Wang, Weiwei and Xu, Xun and Ma, Nan and Lendlein, Andreas}, title = {Structure, mechanical properties and degradation behavior of electrospun PEEU fiber meshes and films}, series = {MRS advances : a journal of the Materials Research Society (MRS)}, volume = {6}, journal = {MRS advances : a journal of the Materials Research Society (MRS)}, number = {10}, publisher = {Springer Nature Switzerland AG}, address = {Cham}, issn = {2059-8521}, doi = {10.1557/s43580-020-00001-0}, pages = {276 -- 282}, year = {2021}, abstract = {The capability of a degradable implant to provide mechanical support depends on its degradation behavior. Hydrolytic degradation was studied for a polyesteretherurethane (PEEU70), which consists of poly(p-dioxanone) (PPDO) and poly(epsilon-caprolactone) (PCL) segments with a weight ratio of 70:30 linked by diurethane junction units. PEEU70 samples prepared in the form of meshes with average fiber diameters of 1.5 mu m (mesh1.5) and 1.2 mu m (mesh1.2), and films were sterilized and incubated in PBS at 37 degrees C with 5 vol\% CO2 supply for 1 to 6 weeks. Degradation features, such as cracks or wrinkles, became apparent from week 4 for all samples. Mass loss was found to be 11 wt\%, 6 wt\%, and 4 wt\% for mesh1.2, mesh1.5, and films at week 6. The elongation at break decreased to under 20\% in two weeks for mesh1.2. In case of the other two samples, this level of degradation was achieved after 4 weeks. The weight average molecular weight of both PEEU70 mesh and film samples decreased to below 30 kg/mol when elongation at break dropped below 20\%. The time period of sustained mechanical stability of PEEU70-based meshes depends on the fiber diameter and molecular weight.}, language = {en} } @article{ZhouXuMaetal.2021, author = {Zhou, Shuo and Xu, Xun and Ma, Nan and Jung, Friedrich and Lendlein, Andreas}, title = {Influence of sterilization conditions on sulfate-functionalized polyGGE}, series = {Clinical hemorheology and microcirculation : blood flow and vessels}, volume = {79}, journal = {Clinical hemorheology and microcirculation : blood flow and vessels}, number = {4}, publisher = {IOS Press}, address = {Amsterdam}, issn = {1386-0291}, doi = {10.3233/CH-211241}, pages = {597 -- 608}, year = {2021}, abstract = {Sulfated biomolecules are known to influence numerous biological processes in all living organisms. Particularly, they contribute to prevent and inhibit the hypercoagulation condition. The failure of polymeric implants and blood contacting devices is often related to hypercoagulation and microbial contamination. Here, bioactive sulfated biomacromolecules are mimicked by sulfation of poly(glycerol glycidyl ether) (polyGGE) films. Autoclaving, gamma-ray irradiation and ethylene oxide (EtO) gas sterilization techniques were applied to functionalized materials. The sulfate group density and hydrophilicity of sulfated polymers were decreased while chain mobility and thermal degradation were enhanced post autoclaving when compared to those after EtO sterilization. These results suggest that a quality control after sterilization is mandatory to ensure the amount and functionality of functionalized groups are retained.}, language = {en} } @article{TungMaringXuetal.2022, author = {Tung, Wing Tai and Maring, Janita A. and Xu, Xun and Liu, Yue and Becker, Matthias and Somesh, Dipthi Bachamanda and Klose, Kristin and Wang, Weiwei and Sun, Xianlei and Ullah, Imran and Kratz, Karl and Neffe, Axel T. and Stamm, Christof and Ma, Nan and Lendlein, Andreas}, title = {In vivo performance of a cell and factor free multifunctional fiber mesh modulating postinfarct myocardial remodeling}, series = {Advanced Functional Materials}, volume = {32}, journal = {Advanced Functional Materials}, number = {31}, publisher = {Wiley}, address = {Weinheim}, issn = {1616-301X}, doi = {10.1002/adfm.202110179}, pages = {17}, year = {2022}, abstract = {Guidance of postinfarct myocardial remodeling processes by an epicardial patch system may alleviate the consequences of ischemic heart disease. As macrophages are highly relevant in balancing immune response and regenerative processes their suitable instruction would ensure therapeutic success. A polymeric mesh capable of attracting and instructing monocytes by purely physical cues and accelerating implant degradation at the cell/implant interface is designed. In a murine model for myocardial infarction the meshes are compared to those either coated with extracellular matrix or loaded with induced cardiomyocyte progenitor cells. All implants promote macrophage infiltration and polarization in the epicardium, which is verified by in vitro experiments. 6 weeks post-MI, especially the implantation of the mesh attenuates left ventricular adverse remodeling processes as shown by reduced infarct size (14.7\% vs 28-32\%) and increased wall thickness (854 mu m vs 400-600 mu m), enhanced angiogenesis/arteriogenesis (more than 50\% increase compared to controls and other groups), and improved heart function (ejection fraction = 36.8\% compared to 12.7-31.3\%). Upscaling as well as process controls is comprehensively considered in the presented mesh fabrication scheme to warrant further progression from bench to bedside.}, language = {en} } @article{XuNieWangetal.2021, author = {Xu, Xun and Nie, Yan and Wang, Weiwei and Ma, Nan and Lendlein, Andreas}, title = {Periodic thermomechanical modulation of toll-like receptor expression and distribution in mesenchymal stromal cells}, series = {MRS communications / a publication of the Materials Research Society}, volume = {11}, journal = {MRS communications / a publication of the Materials Research Society}, number = {4}, publisher = {Springer}, address = {Berlin}, issn = {2159-6867}, doi = {10.1557/s43579-021-00049-5}, pages = {425 -- 431}, year = {2021}, abstract = {Toll-like receptor (TLR) can trigger an immune response against virus including SARS-CoV-2. TLR expression/distribution is varying in mesenchymal stromal cells (MSCs) depending on their culture environments. Here, to explore the effect of periodic thermomechanical cues on TLRs, thermally controlled shape-memory polymer sheets with programmable actuation capacity were created. The proportion of MSCs expressing SARS-CoV-2-associated TLRs was increased upon stimulation. The TLR4/7 colocalization was promoted and retained in the endoplasmic reticula. The TLR redistribution was driven by myosin-mediated F-actin assembly. These results highlight the potential of boosting the immunity for combating COVID-19 via thermomechanical preconditioning of MSCs.}, language = {en} } @article{DengWangXuetal.2021, author = {Deng, Zijun and Wang, Weiwei and Xu, Xun and Ma, Nan and Lendlein, Andreas}, title = {Polydopamine-based biofunctional substrate coating promotes mesenchymal stem cell migration}, series = {MRS advances : a journal of the Materials Research Society (MRS)}, volume = {6}, journal = {MRS advances : a journal of the Materials Research Society (MRS)}, number = {31}, publisher = {Springer Nature Switzerland AG}, address = {Cham}, issn = {2059-8521}, doi = {10.1557/s43580-021-00091-4}, pages = {739 -- 744}, year = {2021}, abstract = {Rapid migration of mesenchymal stem cells (MSCs) on device surfaces could support in vivo tissue integration and might facilitate in vitro organoid formation. Here, polydopamine (PDA) is explored as a biofunctional coating to effectively promote MSC motility. It is hypothesized that PDA stimulates fibronectin deposition and in this way enhances integrin-mediated migration capability. The random and directional cell migration was investigated by time-lapse microscopy and gap closure assay respectively, and analysed with softwares as computational tools. A higher amount of deposited fibronectin was observed on PDA substrate, compared to the non-coated substrate. The integrin beta 1 activation and focal adhesion kinase (FAK) phosphorylation at Y397 were enhanced on PDA substrate, but the F-actin cytoskeleton was not altered, suggesting MSC migration on PDA was regulated by integrin initiated FAK signalling. This study strengthens the biofunctionality of PDA coating for regulating stem cells and offering a way of facilitating tissue integration of devices.}, language = {en} } @article{MachatschekSaretiaLendlein2021, author = {Machatschek, Rainhard Gabriel and Saretia, Shivam and Lendlein, Andreas}, title = {Assessing the influence of temperature-memory creation on the degradation of copolyesterurethanes in ultrathin films}, series = {Advanced materials interfaces}, volume = {8}, journal = {Advanced materials interfaces}, number = {6}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {2196-7350}, doi = {10.1002/admi.202001926}, pages = {8}, year = {2021}, abstract = {Copolyesterurethanes (PDLCLs) based on oligo(epsilon-caprolactone) (OCL) and oligo(omega-pentadecalactone) (OPDL) segments are biodegradable thermoplastic temperature-memory polymers. The temperature-memory capability in these polymers with crystallizable control units is implemented by a thermomechanical programming process causing alterations in the crystallite arrangement and chain organization. These morphological changes can potentially affect degradation. Initial observations on the macroscopic level inspire the hypothesis that switching of the controlling units causes an accelerated degradation of the material, resulting in programmable degradation by sequential coupling of functions. Hence, detailed degradation studies on Langmuir films of a PDLCL with 40 wt\% OPDL content are carried out under enzymatic catalysis. The temperature-memory creation procedure is mimicked by compression at different temperatures. The evolution of the chain organization and mechanical properties during the degradation process is investigated by means of polarization-modulated infrared reflection absorption spectroscopy, interfacial rheology and to some extend by X-ray reflectivity. The experiments on PDLCL Langmuir films imply that degradability is not enhanced by thermal switching, as the former depends on the temperature during cold programming. Nevertheless, the thin film experiments show that the leaching of OCL segments does not induce further crystallization of the OPDL segments, which is beneficial for a controlled and predictable degradation.}, language = {en} } @article{NeffeLoewenbergJulichGruneretal.2021, author = {Neffe, Axel T. and L{\"o}wenberg, Candy and Julich-Gruner, Konstanze K. and Behl, Marc and Lendlein, Andreas}, title = {Thermally-induced shape-memory behavior of degradable gelatin-based networks}, series = {International journal of molecular sciences}, volume = {22}, journal = {International journal of molecular sciences}, number = {11}, publisher = {Molecular Diversity Preservation International}, address = {Basel}, issn = {1422-0067}, doi = {10.3390/ijms22115892}, pages = {15}, year = {2021}, abstract = {Shape-memory hydrogels (SMH) are multifunctional, actively-moving polymers of interest in biomedicine. In loosely crosslinked polymer networks, gelatin chains may form triple helices, which can act as temporary net points in SMH, depending on the presence of salts. Here, we show programming and initiation of the shape-memory effect of such networks based on a thermomechanical process compatible with the physiological environment. The SMH were synthesized by reaction of glycidylmethacrylated gelatin with oligo(ethylene glycol) (OEG) alpha,omega-dithiols of varying crosslinker length and amount. Triple helicalization of gelatin chains is shown directly by wide-angle X-ray scattering and indirectly via the mechanical behavior at different temperatures. The ability to form triple helices increased with the molar mass of the crosslinker. Hydrogels had storage moduli of 0.27-23 kPa and Young's moduli of 215-360 kPa at 4 degrees C. The hydrogels were hydrolytically degradable, with full degradation to water-soluble products within one week at 37 degrees C and pH = 7.4. A thermally-induced shape-memory effect is demonstrated in bending as well as in compression tests, in which shape recovery with excellent shape-recovery rates R-r close to 100\% were observed. In the future, the material presented here could be applied, e.g., as self-anchoring devices mechanically resembling the extracellular matrix.}, language = {en} } @article{BochoveGrijpmaLendleinetal.2021, author = {Bochove, Bas van and Grijpma, Dirk W. and Lendlein, Andreas and Sepp{\"a}l{\"a}, Jukka}, title = {Designing advanced functional polymers for medicine}, series = {European polymer journal : EPJ}, volume = {155}, journal = {European polymer journal : EPJ}, publisher = {Elsevier}, address = {Oxford}, issn = {0014-3057}, doi = {10.1016/j.eurpolymj.2021.110573}, pages = {2}, year = {2021}, language = {en} } @misc{FarhanChaudharyNoecheletal.2020, author = {Farhan, Muhammad and Chaudhary, Deeptangshu and N{\"o}chel, Ulrich and Behl, Marc and Kratz, Karl and Lendlein, Andreas}, title = {Electrical actuation of coated and composite fibers based on poly[ethylene-co-(vinyl acetate)]}, series = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {2}, issn = {1866-8372}, doi = {10.25932/publishup-57167}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-571679}, pages = {10}, year = {2020}, abstract = {Robots are typically controlled by electrical signals. Resistive heating is an option to electrically trigger actuation in thermosensitive polymer systems. In this study electrically triggerable poly[ethylene-co-(vinyl acetate)] (PEVA)-based fiber actuators are realized as composite fibers as well as polymer fibers with conductive coatings. In the coated fibers, the core consists of crosslinked PEVA (cPEVA), while the conductive coating shell is achieved via a dip coating procedure with a coating thickness between 10 and 140 mu m. The conductivity of coated fibers sigma = 300-550 S m(-1) is much higher than that of the composite fibers sigma = 5.5 S m(-1). A voltage (U) of 110 V is required to heat 30 cm of coated fiber to a targeted temperature of approximate to 65 degrees C for switching in less than a minute. Cyclic electrical actuation investigations reveal epsilon '(rev) = 5 +/- 1\% reversible change in length for coated fibers. The fabrication of such electro-conductive polymeric actuators is suitable for upscaling so that their application potential as artificial muscles can be explored in future studies.}, language = {en} } @misc{DengWangXuaetal.2020, author = {Deng, Zijun and Wang, Weiwei and Xua, Xun and Gould, Oliver E. C. and Kratz, Karl and Ma, Nan and Lendlein, Andreas}, title = {Polymeric sheet actuators with programmable bioinstructivity}, series = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {4}, issn = {1866-8372}, doi = {10.25932/publishup-51549}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-515490}, pages = {9}, year = {2020}, abstract = {Stem cells are capable of sensing and processing environmental inputs, converting this information to output a specific cell lineage through signaling cascades. Despite the combinatorial nature of mechanical, thermal, and biochemical signals, these stimuli have typically been decoupled and applied independently, requiring continuous regulation by controlling units. We employ a programmable polymer actuator sheet to autonomously synchronize thermal and mechanical signals applied to mesenchymal stem cells (MSC5). Using a grid on its underside, the shape change of polymer sheet, as well as cell morphology, calcium (Ca2+) influx, and focal adhesion assembly, could be visualized and quantified. This paper gives compelling evidence that the temperature sensing and mechanosensing of MSC5 are interconnected via intracellular Ca2+. Up-regulated Ca2+ levels lead to a remarkable alteration of histone H3K9 acetylation and activation of osteogenic related genes. The interplay of physical, thermal, and biochemical signaling was utilized to accelerate the cell differentiation toward osteogenic lineage. The approach of programmable bioinstructivity provides a fundamental principle for functional biomaterials exhibiting multifaceted stimuli on differentiation programs. Technological impact is expected in the tissue engineering of periosteum for treating bone defects.}, language = {en} } @article{DengWangXuaetal.2020, author = {Deng, Zijun and Wang, Weiwei and Xua, Xun and Gould, Oliver E. C. and Kratz, Karl and Ma, Nan and Lendlein, Andreas}, title = {Polymeric sheet actuators with programmable bioinstructivity}, series = {PNAS}, volume = {117}, journal = {PNAS}, number = {4}, publisher = {National Academy of Sciences}, address = {Washington, DC}, issn = {1091-6490}, doi = {10.1073/pnas.1910668117}, pages = {1895 -- 1901}, year = {2020}, abstract = {Stem cells are capable of sensing and processing environmental inputs, converting this information to output a specific cell lineage through signaling cascades. Despite the combinatorial nature of mechanical, thermal, and biochemical signals, these stimuli have typically been decoupled and applied independently, requiring continuous regulation by controlling units. We employ a programmable polymer actuator sheet to autonomously synchronize thermal and mechanical signals applied to mesenchymal stem cells (MSC5). Using a grid on its underside, the shape change of polymer sheet, as well as cell morphology, calcium (Ca2+) influx, and focal adhesion assembly, could be visualized and quantified. This paper gives compelling evidence that the temperature sensing and mechanosensing of MSC5 are interconnected via intracellular Ca2+. Up-regulated Ca2+ levels lead to a remarkable alteration of histone H3K9 acetylation and activation of osteogenic related genes. The interplay of physical, thermal, and biochemical signaling was utilized to accelerate the cell differentiation toward osteogenic lineage. The approach of programmable bioinstructivity provides a fundamental principle for functional biomaterials exhibiting multifaceted stimuli on differentiation programs. Technological impact is expected in the tissue engineering of periosteum for treating bone defects.}, language = {en} } @article{SaretiaMachatschekLendlein2021, author = {Saretia, Shivam and Machatschek, Rainhard Gabriel and Lendlein, Andreas}, title = {Degradation kinetics of oligo(ε-caprolactone) ultrathin films}, series = {MRS advances : a journal of the Materials Research Society (MRS)}, volume = {6}, journal = {MRS advances : a journal of the Materials Research Society (MRS)}, number = {33}, publisher = {Springer Nature Switzerland AG}, address = {Cham}, issn = {2059-8521}, doi = {10.1557/s43580-021-00067-4}, pages = {790 -- 795}, year = {2021}, abstract = {The potential of using crystallinity as morphological parameter to control polyester degradation in acidic environments is explored in ultrathin films by Langmuir technique. Films of hydroxy or methacrylate end-capped oligo(epsilon-caprolactone) (OCL) are prepared at the air-water interface as a function of mean molecular area (MMA). The obtained amorphous, partially crystalline or highly crystalline ultrathin films of OCL are hydrolytically degraded at pH similar to 1.2 on water surface or on silicon surface as-transferred films. A high crystallinity reduces the hydrolytic degradation rate of the films on both water and solid surfaces. Different acceleration rates of hydrolytic degradation of semi-crystalline films are achieved either by crystals complete melting, partially melting, or by heating them below their melting temperatures. Semi-crystalline OCL films transferred via water onto a solid surface retain their crystalline morphology, degrade in a controlled manner, and are of interest as thermoswitchable coatings for cell substrates and medical devices.}, language = {en} } @article{TarazonaLizcanoMachatschekBalcuchoetal.2022, author = {Tarazona Lizcano, Natalia Andrea and Machatschek, Rainhard Gabriel and Balcucho, Jennifer and Castro-Mayorga, Jinneth Lorena and Saldarriaga, Juan Francisco and Lendlein, Andreas}, title = {Opportunities and challenges for integrating the development of sustainable polymer materials within an international circular (bio)economy concept}, series = {MRS energy \& sustainability : science \& technology \& socio-economics \& policy}, volume = {9}, journal = {MRS energy \& sustainability : science \& technology \& socio-economics \& policy}, number = {1}, publisher = {Springer Nature}, address = {London}, issn = {2329-2229}, doi = {10.1557/s43581-021-00015-7}, pages = {28 -- 34}, year = {2022}, abstract = {The production and consumption of commodity polymers have been an indispensable part of the development of our modern society. Owing to their adjustable properties and variety of functions, polymer-based materials will continue playing important roles in achieving the Sustainable Development Goals (SDG)s, defined by the United Nations, in key areas such as healthcare, transport, food preservation, construction, electronics, and water management. Considering the serious environmental crisis, generated by increasing consumption of plastics, leading-edge polymers need to incorporate two types of functions: Those that directly arise from the demands of the application (e.g. selective gas and liquid permeation, actuation or charge transport) and those that enable minimization of environmental harm, e.g., through prolongation of the functional lifetime, minimization of material usage, or through predictable disintegration into non-toxic fragments. Here, we give examples of how the incorporation of a thoughtful combination of properties/functions can enhance the sustainability of plastics ranging from material design to waste management. We focus on tools to measure and reduce the negative impacts of plastics on the environment throughout their life cycle, the use of renewable sources for their synthesis, the design of biodegradable and/or recyclable materials, and the use of biotechnological strategies for enzymatic recycling of plastics that fits into a circular bioeconomy. Finally, we discuss future applications for sustainable plastics with the aim to achieve the SDGs through international cooperation.
Leading-edge polymer-based materials for consumer and advanced applications are necessary to achieve sustainable development at a global scale. It is essential to understand how sustainability can be incorporated in these materials via green chemistry, the integration of bio-based building blocks from biorefineries, circular bioeconomy strategies, and combined smart and functional capabilities.}, language = {en} } @article{FolikumahBehlLendlein2021, author = {Folikumah, Makafui Y. and Behl, Marc and Lendlein, Andreas}, title = {Reaction behaviour of peptide-based single thiol-thioesters exchange reaction substrate in the presence of externally added thiols}, series = {MRS communications / a publication of the Materials Research Society}, volume = {11}, journal = {MRS communications / a publication of the Materials Research Society}, number = {4}, publisher = {Springer}, address = {Berlin}, issn = {2159-6859}, doi = {10.1557/s43579-021-00041-z}, pages = {402 -- 410}, year = {2021}, abstract = {Identification of patterns in chemical reaction pathways aids in the effective design of molecules for specific applications. Here, we report on model reactions with a water-soluble single thiol-thioester exchange (TTE) reaction substrate, which was designed taking in view biological and medical applications. This substrate consists of the thio-depsipeptide, Ac-Pro-Leu-Gly-SLeu-Leu-Gly-NEtSH (TDP) and does not yield foul-smelling thiol exchange products when compared with aromatic thiol containing single TTE substrates. TDP generates an alpha,omega-dithiol crosslinker in situ in a 'pseudo intramolecular' TTE. Competitive intermolecular TTE of TDP with externally added "basic" thiols increased the crosslinker concentration whilst "acidic" thiols decreased its concentration. TDP could potentially enable in situ bioconjugation and crosslinking applications.}, language = {en} } @article{HoffmannMachatschekLendlein2022, author = {Hoffmann, Falk and Machatschek, Rainhard Gabriel and Lendlein, Andreas}, title = {Analytical model and Monte Carlo simulations of polymer degradation with improved chain cut statistics}, series = {Journal of materials research : JMR}, volume = {37}, journal = {Journal of materials research : JMR}, number = {5}, publisher = {Springer}, address = {Heidelberg}, issn = {0884-2914}, doi = {10.1557/s43578-022-00495-4}, pages = {1093 -- 1101}, year = {2022}, abstract = {The degradation of polymers is described by mathematical models based on bond cleavage statistics including the decreasing probability of chain cuts with decreasing average chain length. We derive equations for the degradation of chains under a random chain cut and a chain end cut mechanism, which are compared to existing models. The results are used to predict the influence of internal molecular parameters. It is shown that both chain cut mechanisms lead to a similar shape of the mass or molecular mass loss curve. A characteristic time is derived, which can be used to extract the maximum length of soluble fragments l of the polymer. We show that the complete description is needed to extract the degradation rate constant k from the molecular mass loss curve and that l can be used to design polymers that lose less mechanical stability before entering the mass loss phase.}, language = {en} } @article{NeffeLoewenbergLendlein2021, author = {Neffe, Axel T. and L{\"o}wenberg, Candy and Lendlein, Andreas}, title = {Hydrogel networks by aliphatic dithiol Michael addition to glycidylmethacrylated gelatin}, series = {MRS advances : a journal of the Materials Research Society (MRS)}, volume = {6}, journal = {MRS advances : a journal of the Materials Research Society (MRS)}, number = {33}, publisher = {Springer Nature Switzerland AG}, address = {Cham}, issn = {2059-8521}, doi = {10.1557/s43580-021-00136-8}, pages = {796 -- 800}, year = {2021}, abstract = {Functionalization of gelatin with glycidylmethacrylate (GMA-gelatin) enables network formation employing the double bond, so that the reaction is orthogonal to the inherent functional groups in the biomacromolecule. Here, network formation by crosslinking of GMA-gelatin with hexane 1,6-dithiol or nonane 1,9-dithiol to tailor properties and enable a shape-memory effect is shown by H-1 NMR and FT-IR spectroscopy. Hydrogel swelling (460-1900 vol\%) and mechanical properties (Young's modulus E = 59-512 kPa, elongation at break epsilon(b) = 44-127\%) depended on the molecular composition of the networks and temperature. Increased crosslinker length, thiol:methacrylate molar ratio, and precursor concentrations led to denser networks. Change of properties with temperature suggested adoption of triple helices by gelatin chains, forming physical netpoints at lower temperatures (< 20 degrees C). However, the limited freedom of the gelatin chains to move allowed only a minimal extent of triple helices formation, as it became apparent from the related signal in wide-angle X-ray scattering and the thermal transition associated to triple helices in some networks by DSC. The presented strategy is likely transferable to other biomacromolecules, and the results suggest that too short crosslinkers may result in a significant amount of grafting rather than network formation.}, language = {en} } @article{LauMaierBrauneetal.2021, author = {Lau, Skadi and Maier, Anna and Braune, Steffen and Gossen, Manfred and Lendlein, Andreas}, title = {Effect of endothelial culture medium composition on platelet responses to polymeric biomaterials}, series = {International journal of molecular sciences}, volume = {22}, journal = {International journal of molecular sciences}, number = {13}, publisher = {Molecular Diversity Preservation International}, address = {Basel}, issn = {1422-0067}, doi = {10.3390/ijms22137006}, pages = {13}, year = {2021}, abstract = {Near-physiological in vitro thrombogenicity test systems for the evaluation of blood-contacting endothelialized biomaterials requires co-cultivation with platelets (PLT). However, the addition of PLT has led to unphysiological endothelial cell (EC) detachment in such in vitro systems. A possible cause for this phenomenon may be PLT activation triggered by the applied endothelial cell medium, which typically consists of basal medium (BM) and nine different supplements. To verify this hypothesis, the influence of BM and its supplements was systematically analyzed regarding PLT responses. For this, human platelet rich plasma (PRP) was mixed with BM, BM containing one of nine supplements, or with BM containing all supplements together. PLT adherence analysis was carried out in six-channel slides with plasma-treated cyclic olefin copolymer (COC) and poly(tetrafluoro ethylene) (PTFE, as a positive control) substrates as part of the six-channel slides in the absence of EC and under static conditions. PLT activation and aggregation were analyzed using light transmission aggregometry and flow cytometry (CD62P). Medium supplements had no effect on PLT activation and aggregation. In contrast, supplements differentially affected PLT adherence, however, in a polymer- and donor-dependent manner. Thus, the use of standard endothelial growth medium (BM + all supplements) maintains functionality of PLT under EC compatible conditions without masking the differences of PLT adherence on different polymeric substrates. These findings are important prerequisites for the establishment of a near-physiological in vitro thrombogenicity test system assessing polymer-based cardiovascular implant materials in contact with EC and PLT.}, language = {en} } @article{LauGossenLendleinetal.2022, author = {Lau, Skadi and Gossen, Manfred and Lendlein, Andreas and Jung, Friedrich}, title = {Differential sensitivity of assays for determining vein endothelial cell senescence}, series = {Clinical hemorheology and microcirculation : blood flow and vessels}, volume = {81}, journal = {Clinical hemorheology and microcirculation : blood flow and vessels}, number = {3}, publisher = {IOS Press}, address = {Amsterdam}, issn = {1386-0291}, doi = {10.3233/CH-211294}, pages = {191 -- 203}, year = {2022}, abstract = {In vivo endothelialization of polymer-based cardiovascular implant materials is a promising strategy to reduce the risk of platelet adherence and the subsequent thrombus formation and implant failure. However, endothelial cells from elderly patients are likely to exhibit a senescent phenotype that may counteract endothelialization. The senescence status of cells should therefore be investigated prior to implantation of devices designed to be integrated in the blood vessel wall. Here, human umbilical vein endothelial cells (HUVEC) were cultivated up to passage (P) 4, 10 and 26/27 to determine the population doubling time and the senescence status by four different methods. Determination of the senescence-associated beta-galactosidase activity (SA-beta-Gal) was carried out by colorimetric staining and microscopy (i), as well as by photometric quantification (ii), and the expression of senescence-associated nuclear proteins p16 and p21 as well as the proliferation marker Ki67 was assessed by immunostaining (iii), and by flow cytometry (iv). The population doubling time of P27-cells was remarkably greater (103 +/- 65 h) compared to P4-cells (24 +/- 3 h) and P10-cell (37 +/- 15 h). Among the four different methods tested, the photometric SA-beta-Gal activity assay and the flow cytometric determination of p16 and Ki67 were most effective in discriminating P27-cells from P4- and P10-cells. These methods combined with functional endothelial cell analyses might aid predictions on the performance of implant endothelialization in vivo.}, language = {en} } @article{ZhangRešetičBehletal.2021, author = {Zhang, Pengfei and Rešetič, Andraž and Behl, Marc and Lendlein, Andreas}, title = {Multifunctionality in polymer networks by dynamic of coordination bonds}, series = {Macromolecular chemistry and physics}, volume = {222}, journal = {Macromolecular chemistry and physics}, number = {3}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1521-3935}, doi = {10.1002/macp.202000394}, pages = {11}, year = {2021}, abstract = {The need for multifunctional materials is driven by emerging technologies and innovations, such as in the field of soft robotics and tactile or haptic systems, where minimizing the number of operational components is not only desirable, but can also be essential for realizing such devices. This study report on designing a multifunctional soft polymer material that can address a number of operating requirements such as solvent resistance, reshaping ability, self-healing capability, fluorescence stimuli-responsivity, and anisotropic structural functions. The numerous functional abilities are associated to rhodium(I)-phosphine coordination bonds, which in a polymer network act with their dynamic and non-covalently bonded nature as multifunctional crosslinks. Reversible aggregation of coordination bonds leads to changes in fluorescence emission intensity that responds to chemical or mechanical stimuli. The fast dynamics and diffusion of rhodium-phosphine ions across and through contacting areas of the material provide for reshaping and self-healing abilities that can be further exploited for assembly of multiple pieces into complex forms, all without any loss to material-sensing capabilities.}, language = {en} }