TY - JOUR A1 - Machatschek, Rainhard Gabriel A1 - Saretia, Shivam A1 - Lendlein, Andreas T1 - Assessing the influence of temperature-memory creation on the degradation of copolyesterurethanes in ultrathin films JF - Advanced materials interfaces N2 - 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. KW - block copolymers KW - degradation KW - Langmuir monolayers KW - rheology KW - temperature-memory polymers Y1 - 2021 U6 - https://doi.org/10.1002/admi.202001926 SN - 2196-7350 VL - 8 IS - 6 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Deng, Zijun A1 - Wang, Weiwei A1 - Xu, Xun A1 - Ma, Nan A1 - Lendlein, Andreas T1 - Polydopamine-based biofunctional substrate coating promotes mesenchymal stem cell migration JF - MRS advances : a journal of the Materials Research Society (MRS) N2 - 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. Y1 - 2021 U6 - https://doi.org/10.1557/s43580-021-00091-4 SN - 2059-8521 VL - 6 IS - 31 SP - 739 EP - 744 PB - Springer Nature Switzerland AG CY - Cham ER - TY - JOUR A1 - Farhan, Muhammad A1 - Rudolph, Tobias A1 - Nöchel, Ulrich A1 - Yan, Wan A1 - Kratz, Karl A1 - Lendlein, Andreas T1 - Noncontinuously Responding Polymeric Actuators JF - ACS applied materials & interfaces N2 - Reversible movements of current polymeric actuators stem from the continuous response to signals from a controlling unit, and subsequently cannot be interrupted without stopping or eliminating the input trigger. Here, we present actuators based on cross-linked blends of two crystallizable polymers capable of pausing their movements in a defined manner upon continuous cyclic heating and cooling. This noncontinuous actuation can be adjusted by varying the applied heating and cooling rates. The feasibility of these devices for technological applications was shown in a 140 cycle experiment of free-standing noncontinuous shape shifts, as well as by various demonstrators. KW - soft robotics KW - polymer actuators KW - thermo-sensitivity KW - shape shifting materials KW - crystallization behavior Y1 - 2017 U6 - https://doi.org/10.1021/acsami.7b11316 SN - 1944-8244 VL - 9 SP - 33559 EP - 33564 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Farhan, Muhammad A1 - Rudolph, Tobias A1 - Nöchel, Ulrich A1 - Kratz, Karl A1 - Lendlein, Andreas T1 - Extractable Free Polymer Chains Enhance Actuation Performance of Crystallizable Poly(epsilon-caprolactone) Networks and Enable Self-Healing JF - Polymers N2 - Crosslinking of thermoplastics is a versatile method to create crystallizable polymer networks, which are of high interest for shape-memory actuators. Here, crosslinked poly(epsilon-caprolactone) thermosets (cPCLs) were prepared from linear starting material, whereby the amount of extractable polymer was varied. Fractions of 5-60 wt % of non-crosslinked polymer chains, which freely interpenetrate the crosslinked network, were achieved leading to differences in the resulting phase of the bulk material. This can be described as "sponge-like" with open or closed compartments depending on the amount of interpenetrating polymer. The crosslinking density and the average network chain length remained in a similar range for all network structures, while the theoretical accessible volume for reptation of the free polymer content is affected. This feature could influence or introduce new functions into the material created by thermomechanical treatment. The effect of interpenetrating PCL in cPCLs on the reversible actuation was analyzed by cyclic, uniaxial tensile tests. Here, high reversible strains of up to Delta epsilon = 24% showed the enhanced actuation performance of networks with a non-crosslinked PCL content of 30 wt % resulting from the crystal formation in the phase of the non-crosslinked PCL and co-crystallization with network structures. Additional functionalities are reprogrammability and self-healing capabilities for networks with high contents of extractable polymer enabling reusability and providing durable actuator materials. KW - shape-memory polymer actuators KW - soft actuators KW - self-healing KW - poly(epsilon-caprolactone) KW - thermoplastics Y1 - 2018 U6 - https://doi.org/10.3390/polym10030255 SN - 2073-4360 VL - 10 IS - 3 PB - MDPI CY - Basel ER - TY - JOUR A1 - Farhan, Muhammad A1 - Rudolph, Tobias A1 - Kratz, Karl A1 - Lendlein, Andreas T1 - Torsional Fiber Actuators from Shape-memory Polymer JF - MRS Advances N2 - Humanoid robots, prosthetic limbs and exoskeletons require soft actuators to perform their primary function, which is controlled movement. In this wont we explored whether crosslinked poly[ethylene-co-(vinyl acetate)] (cPEVA) fibers, with different vinyl acetate (VA) content can serve as torsional fiber actuators. exhibiting temperature controlled reversible rotational changes. Broad melting transitions ranging from 50 to 90 degrees C for cPEVA18-165 or from 40 to 80 degrees C for cPEVA28-165 fibers in combination with complete crystallization at temperatures around 10 degrees C make them suitable actuating materials with adjustable actuation temperature ranges between 10 and 70 degrees C during repetitive cooling and heating. The obtained fibers exhibited a circular cross section with diameters around 0.4 +/- 0.1 mm, while a length of 4 cm was employed for the investigation of reversible rotational actuation after programming by twist insertion using 30 complete rotations at a temperature above melting transition. Repetitive heating and cooling between 10 to 60 degrees C or 70 degrees C of one-end-tethered programmed fibers revealed reversible rotations and torsional force. During cooling 3 +/- 1 complete rotations (Delta theta(r) = + 1080 +/- 360 degrees) in twisting direction were observed, while 4 +/- 1 turns in the opposite direction (Delta theta(r) = - 1440 +/- 1360 degrees) were found during heating. Such torsional fiber actuators, which are capable of approximately one rotation per cm fiber length, can serve as miniaturized rotary motors to provide rotational actuation in futuristic humanoid robots. Y1 - 2018 U6 - https://doi.org/10.1557/adv.2018.621 SN - 2059-8521 VL - 3 IS - 63 SP - 3861 EP - 3868 PB - Cambridge Univ. Press CY - New York ER - TY - GEN A1 - Moradian, Hanieh A1 - Roch, Toralf A1 - Lendlein, Andreas A1 - Gossen, Manfred T1 - mRNA transfection-induced activation of primary human monocytes and macrophages BT - Dependence on carrier system and nucleotide modifcation T2 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - Monocytes and macrophages are key players in maintaining immune homeostasis. Identifying strategies to manipulate their functions via gene delivery is thus of great interest for immunological research and biomedical applications. We set out to establish conditions for mRNA transfection in hard-to-transfect primary human monocytes and monocyte-derived macrophages due to the great potential of gene expression from in vitro transcribed mRNA for modulating cell phenotypes. mRNA doses, nucleotide modifications, and different carriers were systematically explored in order to optimize high mRNA transfer rates while minimizing cell stress and immune activation. We selected three commercially available mRNA transfection reagents including liposome and polymer-based formulations, covering different application spectra. Our results demonstrate that liposomal reagents can particularly combine high gene transfer rates with only moderate immune cell activation. For the latter, use of specific nucleotide modifications proved essential. In addition to improving efficacy of gene transfer, our findings address discrete aspects of innate immune activation using cytokine and surface marker expression, as well as cell viability as key readouts to judge overall transfection efficiency. The impact of this study goes beyond optimizing transfection conditions for immune cells, by providing a framework for assessing new gene carrier systems for monocyte and macrophage, tailored to specific applications. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1403 KW - sirna transfection KW - mediated delivery KW - gene delivery KW - efficient KW - immunogenicity KW - lipoplexes KW - cells KW - therapeutics KW - polarization KW - pathways Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-515694 SN - 1866-8372 IS - 1 ER - TY - GEN A1 - Farhan, Muhammad A1 - Chaudhary, Deeptangshu A1 - Nöchel, Ulrich A1 - Behl, Marc A1 - Kratz, Karl A1 - Lendlein, Andreas T1 - Electrical actuation of coated and composite fibers based on poly[ethylene-co-(vinyl acetate)] T2 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - 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. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1375 KW - artificial muscles KW - fiber actuators KW - resistive heating KW - shape‐memory polymer actuators KW - soft robotics Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-571679 SN - 1866-8372 IS - 2 ER - TY - JOUR A1 - Moradian, Hanieh A1 - Roch, Toralf A1 - Lendlein, Andreas A1 - Gossen, Manfred T1 - mRNA transfection-induced activation of primary human monocytes and macrophages BT - Dependence on carrier system and nucleotide modifcation JF - Scientific reports N2 - Monocytes and macrophages are key players in maintaining immune homeostasis. Identifying strategies to manipulate their functions via gene delivery is thus of great interest for immunological research and biomedical applications. We set out to establish conditions for mRNA transfection in hard-to-transfect primary human monocytes and monocyte-derived macrophages due to the great potential of gene expression from in vitro transcribed mRNA for modulating cell phenotypes. mRNA doses, nucleotide modifications, and different carriers were systematically explored in order to optimize high mRNA transfer rates while minimizing cell stress and immune activation. We selected three commercially available mRNA transfection reagents including liposome and polymer-based formulations, covering different application spectra. Our results demonstrate that liposomal reagents can particularly combine high gene transfer rates with only moderate immune cell activation. For the latter, use of specific nucleotide modifications proved essential. In addition to improving efficacy of gene transfer, our findings address discrete aspects of innate immune activation using cytokine and surface marker expression, as well as cell viability as key readouts to judge overall transfection efficiency. The impact of this study goes beyond optimizing transfection conditions for immune cells, by providing a framework for assessing new gene carrier systems for monocyte and macrophage, tailored to specific applications. KW - sirna transfection KW - mediated delivery KW - gene delivery KW - efficient KW - immunogenicity KW - lipoplexes KW - cells KW - therapeutics KW - polarization KW - pathways Y1 - 2020 U6 - https://doi.org/10.1038/s41598-020-60506-4 SN - 2045-2322 VL - 10 IS - 1 SP - 1 EP - 15 PB - Springer Nature CY - London ER - TY - GEN A1 - Jiang, Yi A1 - Mansfeld, Ulrich A1 - Kratz, Karl A1 - Lendlein, Andreas T1 - Programmable microscale stiffness pattern of flat polymeric substrates by temperature-memory technology T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - Temperature-memory technology was utilized to generate flat substrates with a programmable stiffness pattern from cross-linked poly(ethylene-co-vinyl acetate) substrates with cylindrical microstructures. Programmed substrates were obtained by vertical compression at temperatures in the range from 60 to 100 degrees C and subsequent cooling, whereby a flat substrate was achieved by compression at 72 degrees C, as documented by scanning electron microscopy and atomic force microscopy (AFM). AFM nanoindentation experiments revealed that all programmed substrates exhibited the targeted stiffness pattern. The presented technology for generating polymeric substrates with programmable stiffness pattern should be attractive for applications such as touchpads. optical storage, or cell instructive substrates. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1102 KW - shape KW - surfaces KW - modulus Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-469745 SN - 1866-8372 VL - 9 IS - 1 SP - 181 EP - 188 ER - TY - JOUR A1 - Lau, Skadi A1 - Gossen, Manfred A1 - Lendlein, Andreas A1 - Jung, Friedrich T1 - Differential sensitivity of assays for determining vein endothelial cell senescence JF - Clinical hemorheology and microcirculation : blood flow and vessels N2 - 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. KW - Ageing KW - population doubling time KW - senescence-associated KW - beta-galactosidase KW - cell cycle inhibitors KW - p16 KW - p21 KW - Ki67 Y1 - 2022 U6 - https://doi.org/10.3233/CH-211294 SN - 1386-0291 SN - 1875-8622 VL - 81 IS - 3 SP - 191 EP - 203 PB - IOS Press CY - Amsterdam ER -