TY - JOUR A1 - Wang, Weiwei A1 - Kratz, Karl A1 - Behl, Marc A1 - Yan, Wan A1 - Liu, Yue A1 - Xu, Xun A1 - Baudis, Stefan A1 - Li, Zhengdong A1 - Kurtz, Andreas A1 - Lendlein, Andreas A1 - Ma, Nan T1 - The interaction of adipose-derived human mesenchymal stem cells and polyether ether ketone JF - Clinical hemorheology and microcirculation : blood flow and vessels N2 - Polyether ether ketone (PEEK) as a high-performance, thermoplastic implant material entered the field of medical applications due to its structural function and commercial availability. In bone tissue engineering, the combination of mesenchymal stem cells (MSCs) with PEEK implants may accelerate the bone formation and promote the osseointegration between the implant and the adjacent bone tissue. In this concept the question how PEEK influences the behaviour and functions of MSCs is of great interest. Here the cellular response of human adipose-derived MSCs to PEEK was evaluated and compared to tissue culture plate (TCP) as the reference material. Viability and morphology of cells were not altered when cultured on the PEEK film. The cells on PEEK presented a high proliferation activity in spite of a relatively lower initial cell adhesion rate. There was no significant difference on cell apoptosis and senescence between the cells on PEEK and TCP. The inflammatory cytokines and VEGF secreted by the cells on these two surfaces were at similar levels. The cells on PEEK showed up-regulated BMP2 and down-regulated BMP4 and BMP6 gene expression, whereas no conspicuous differences were observed in the committed osteoblast markers (BGLAP, COL1A1 and Runx2). With osteoinduction the cells on PEEK and TCP exhibited a similar osteogenic differentiation potential. Our results demonstrate the biofunctionality of PEEK for human MSC cultivation and differentiation. Its clinical benefits in bone tissue engineering may be achieved by combining MSCs with PEEK implants. These data may also provide useful information for further modification of PEEK with chemical or physical methods to regulate the cellular processes of MSCs and to consequently improve the efficacy of MSC-PEEK based therapies. KW - Polyether ether ketone KW - mesenchymal stem cells KW - biocompatibility KW - cell-material interaction KW - osteogenic differentiation Y1 - 2015 U6 - https://doi.org/10.3233/CH-152001 SN - 1386-0291 SN - 1875-8622 VL - 61 IS - 2 SP - 301 EP - 321 PB - IOS Press CY - Amsterdam ER - TY - JOUR A1 - Liu, Yue A1 - Razzaq, Muhammad Yasar A1 - Rudolph, Tobias A1 - Fang, Liang A1 - Kratz, Karl A1 - Lendlein, Andreas T1 - Two-Level Shape Changes of Polymeric Microcuboids Prepared from Crystallizable Copolymer Networks JF - Macromolecules : a publication of the American Chemical Society N2 - Polymeric microdevices bearing features like nonspherical shapes or spatially segregated surface properties are of increasing importance in biological and medical analysis, drug delivery, and bioimaging or microfluidic systems as well as in micromechanics, sensors, information storage, or data carrier devices. Here, a method to fabricate programmable microcuboids with shape-memory capability and the quantification of their recovery at different levels is reported. The method uses the soft lithographic technique to create microcuboids with well-defined sizes and surface properties. Microcuboids having an edge length of 25 mu m and a height of 10 mu m were prepared from cross-linked poly[ethylene-co-(vinyl acetate)] (cPEVA) with different vinyl acetate contents and were programmed by compression with various deformation degrees at elevated temperatures. The microlevel shape-recovery of the cuboidal geometry during heating was monitored by optical microscopy (OM) and atomic force microscopy (AFM) studying the related changes in the projected area (PA) or height, while the nanolevel changes of the nanosurface roughness were investigated by in situ AFM. The shape-memory effect at the microlevel was quantified by the recovery ratio of cuboids (R-r,R-micro), while at the. nanolevel, the recovery ratio of the nanoroughness (R-r,R-nano) was measured. The values of R-r,R-micro,,micro could be tailored in a range from 42 +/- 1% to 102 +/- 1% and Rr,nano from 89 +/- 6% to 136 +/- 21% depending on the applied compression ratio and the amount of vinyl acetate content in the cPEVA microcuboids. Y1 - 2017 U6 - https://doi.org/10.1021/acs.macromol.6b02237 SN - 0024-9297 SN - 1520-5835 VL - 50 SP - 2518 EP - 2527 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Liu, Yue A1 - Gould, Oliver E. C. A1 - Kratz, Karl A1 - Lendlein, Andreas T1 - Shape-memory actuation of individual micro-/nanofibers JF - MRS Advances N2 - Advances in the fabrication and characterization of polymeric nanomaterials has greatly advanced the miniaturization of soft actuators, creating materials capable of replicating the functional physical behavior previously limited to the macroscale. Here, we demonstrate how a reversible shape-memory polymer actuation can be generated in a single micro/nano object, where the shape change during actuation of an individual fiber can be dictated by programming using an AFM-based method. Electrospinning was used to prepare poly(epsilon-caprolactone) micro-/nanofibers, which were fixed and crosslinked on a structured silicon wafer. The programming as well as the observation of recovery and reversible displacement of the fiber were performed by vertical three point bending, using an AFM testing platform introduced here. A plateau tip was utilized to improve the stability of the fiber contact and working distance, enabling larger deformations and greater rbSMPA performance. Values for the reversible elongation of epsilon(rev)= 3.4 +/- 0.1% and 10.5 +/- 0.1% were obtained for a single micro (d = 1.0 +/- 0.2 mu m) and nanofiber (d = 300 +/- 100 nm) in cyclic testing between the temperatures 10 and 60 degrees C. The reversible actuation of the nanofiber was successfully characterized for 10 cycles. The demonstration and characterization of individual shape-memory nano and microfiber actuators represents an important step in the creation of miniaturized robotic devices capable of performing complex physical functions at the length scale of cells and structural component of the extracellular matrix. Y1 - 2020 U6 - https://doi.org/10.1557/adv.2020.276 SN - 2059-8521 VL - 5 IS - 46-47 SP - 2391 EP - 2399 PB - Cambridge Univ. Press CY - New York ER - TY - JOUR A1 - Liu, Yue A1 - Gould, Oliver E. C. A1 - Rudolph, Tobias A1 - Fang, Liang A1 - Kratz, Karl A1 - Lendlein, Andreas T1 - Polymeric microcuboids programmable for temperature-memory JF - Macromolecular materials and engineering N2 - 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. KW - actuation KW - atomic force microscopy KW - biomaterials KW - microparticles KW - shape-memory polymers Y1 - 2020 U6 - https://doi.org/10.1002/mame.202000333 SN - 1438-7492 SN - 1439-2054 VL - 305 IS - 10 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Bäckemo, Johan Dag Valentin A1 - Liu, Yue A1 - Lendlein, Andreas T1 - Bio-inspired and computer-supported design of modulated shape changes in polymer materials JF - MRS communications / a publication of the Materials Research Society N2 - The Venus flytrap is a fascinating plant with a finely tuned mechanical bi-stable system, which can switch between mono- and bi-stability. Here, we combine geometrical design of compliant mechanics and the function of shape-memory polymers to enable switching between bi- and mono-stable states. Digital design and modelling using the Chained Beam Constraint Model forecasted two geometries, which were experimentally realized as structured films of cross-linked poly[ethylene-co-(vinyl acetate)] supported by digital manufacturing. Mechanical evaluation confirmed our predicted features. We demonstrated that a shape-memory effect could switch between bi- and mono-stability for the same construct, effectively imitating the Venus flytrap. KW - Additive manufacturing KW - Biomimetic KW - Shape memory KW - Modelling KW - Polymer Y1 - 2021 U6 - https://doi.org/10.1557/s43579-021-00056-6 SN - 2159-6867 VL - 11 IS - 4 SP - 462 EP - 469 PB - Springer CY - Berlin ER - TY - JOUR A1 - Izraylit, Victor A1 - Liu, Yue A1 - Tarazona, Natalia A. A1 - Machatschek, Rainhard Gabriel A1 - Lendlein, Andreas T1 - Crystallization and degradation behaviour of multiblock copolyester blends in Langmuir monolayers JF - MRS communications / a publication of the Materials Research Society N2 - Supporting the wound healing of soft tissues requires fixation devices becoming more elastic while degrading. To address this unmet need, we designed a blend of degradable multiblock copolymers, which is cross-linked by PLA stereocomplexation combining two soft segments differing substantially in their hydrolytic degradation rate. The degradation path and concomitant structural changes are predicted by Langmuir monolayer technique. The fast hydrolysis of one soft segment leads to a decrease of the total polymer mass at constant physical cross-linking density. The corresponding increase of the average spacing between the network nodes suggests the targeted increase of the blend's flexibility. KW - Degradable KW - In situ KW - Microstructure KW - Thin film Y1 - 2021 U6 - https://doi.org/10.1557/s43579-021-00107-y SN - 2159-6859 SN - 2159-6867 VL - 11 IS - 6 SP - 850 EP - 855 PB - Springer CY - Berlin ER - TY - JOUR A1 - Liu, Yue A1 - Gould, Oliver E. C. A1 - Kratz, Karl A1 - Lendlein, Andreas T1 - On demand sequential release of (sub)micron particles controlled by size and temperature JF - Small : nano micro N2 - Polymeric devices capable of releasing submicron particles (subMP) on demand are highly desirable for controlled release systems, sensors, and smart surfaces. Here, a temperature-memory polymer sheet with a programmable smooth surface served as matrix to embed and release polystyrene subMP controlled by particle size and temperature. subMPs embedding at 80 degrees C can be released sequentially according to their size (diameter D of 200 nm, 500 nm, 1 mu m) when heated. The differences in their embedding extent are determined by the various subMPs sizes and result in their distinct release temperatures. Microparticles of the same size (D approximate to 1 mu m) incorporated in films at different programming temperatures T-p (50, 65, and 80 degrees C) lead to a sequential release based on the temperature-memory effect. The change of apparent height over the film surface is quantified using atomic force microscopy and the realization of sequential release is proven by confocal laser scanning microscopy. The demonstration and quantification of on demand subMP release are of technological impact for assembly, particle sorting, and release technologies in microtechnology, catalysis, and controlled release. KW - on demand particle release KW - temperature-memory effect KW - thermosensitive KW - polymer surface Y1 - 2022 U6 - https://doi.org/10.1002/smll.202104621 SN - 1613-6810 SN - 1613-6829 VL - 18 IS - 5 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Zhang, Shanshan A1 - Liu, Yue A1 - Machatschek, Rainhard Gabriel A1 - Lendlein, Andreas T1 - Ultrathin collagen type I films formed at the air-water interface JF - MRS advances : a journal of the Materials Research Society (MRS) N2 - Collagen-based biomaterials with oriented fibrils have shown great application potential in medicine. However, it is still challenging to control the type I collagen fibrillogenesis in ultrathin films. Here, we report an approach to produce cohesive and well-organized type I collagen ultrathin films of about 10 nm thickness using the Langmuir-Blodgett technique. Ellipsometry, rheology, and Brewster angle microscopy are applied to investigate in situ how the molecules behave at the air-water interface, both at room temperature and 37 degrees C. The interfacial storage modulus observed at room temperature vanishes upon heating, indicating the existence and disappearance of the network structure in the protein nanosheet. The films were spanning over holes as large as 1 mm diameter when transferred at room temperature, proving the strong cohesive interactions. A highly aligned and fibrillar structure was observed by atomic force microscopy (AFM) and optical microscopy. Y1 - 2022 U6 - https://doi.org/10.1557/s43580-021-00160-8 SN - 2059-8521 VL - 7 IS - 4 SP - 56 EP - 62 PB - Springer Nature Switzerland AG CY - Cham ER - TY - JOUR A1 - Tung, Wing Tai A1 - Maring, Janita A. A1 - Xu, Xun A1 - Liu, Yue A1 - Becker, Matthias A1 - Somesh, Dipthi Bachamanda A1 - Klose, Kristin A1 - Wang, Weiwei A1 - Sun, Xianlei A1 - Ullah, Imran A1 - Kratz, Karl A1 - Neffe, Axel T. A1 - Stamm, Christof A1 - Ma, Nan A1 - Lendlein, Andreas T1 - In vivo performance of a cell and factor free multifunctional fiber mesh modulating postinfarct myocardial remodeling JF - Advanced Functional Materials N2 - 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. KW - bioinstructive materials KW - cardiac regeneration KW - function by structure; KW - modulation of in vivo regeneration KW - multifunctional biomaterials Y1 - 2022 U6 - https://doi.org/10.1002/adfm.202110179 SN - 1616-301X SN - 1616-3028 VL - 32 IS - 31 PB - Wiley CY - Weinheim ER -