TY - JOUR A1 - Schneider, Matthias A1 - Fritzsche, Nora A1 - Puciul-Malinowska, Agnieszka A1 - Baliś, Andrzej A1 - Mostafa, Amr A1 - Bald, Ilko A1 - Zapotoczny, Szczepan A1 - Taubert, Andreas T1 - Surface etching of 3D printed poly(lactic acid) with NaOH BT - a systematic approach JF - Polymers N2 - The article describes a systematic investigation of the effects of an aqueous NaOH treatment of 3D printed poly(lactic acid) (PLA) scaffolds for surface activation. The PLA surface undergoes several morphology changes and after an initial surface roughening, the surface becomes smoother again before the material dissolves. Erosion rates and surface morphologies can be controlled by the treatment. At the same time, the bulk mechanical properties of the treated materials remain unaltered. This indicates that NaOH treatment of 3D printed PLA scaffolds is a simple, yet viable strategy for surface activation without compromising the mechanical stability of PLA scaffolds. KW - surface modification KW - sodium hydroxide etching KW - poly(lactic acid) KW - 3D KW - printing KW - roughness KW - wettability KW - erosion Y1 - 2020 U6 - https://doi.org/10.3390/polym12081711 SN - 2073-4360 VL - 12 IS - 8 PB - MDPI CY - Basel ER - TY - JOUR A1 - Fandrich, Artur A1 - Buller, Jens A1 - Memczak, Henry A1 - Stoecklein, W. A1 - Hinrichs, K. A1 - Wischerhoff, E. A1 - Schulz, B. A1 - Laschewsky, André A1 - Lisdat, Fred T1 - Responsive Polymer-Electrode Interface-Study of its Thermo- and pH-Sensitivity and the Influence of Peptide Coupling JF - Electrochimica acta : the journal of the International Society of Electrochemistry (ISE) N2 - This study introduces a thermally responsive, polymer-based electrode system. The key component is a surface-attached, temperature-responsive poly(oligoethylene glycol) methacrylate (poly(OEGMA)) type polymer bearing photoreactive benzophenone and carboxy groups containing side chains. The responsive behavior of the polymer in aqueous media has been investigated by turbidimetry measurements. Polymer films are formed on gold substrates by means of the photoreactive 2(dicyclohexylphosphino)benzophenone (DPBP) through photocrosslinking. The electrochemical behavior of the resulting polymer-substrate interface has been investigated in buffered [Fe(CN)6](3-)/[Fe (CN)6](4-)solutions at room temperature and under temperature variation by cyclic voltammetry (CV). The CV experiments show that with increasing temperature structural changes of the polymer layer occur, which alter the output of the electrochemical measurement. Repeated heating/cooling cycles analyzed by CV measurements and pH changes analyzed by quartz crystal microbalance with dissipation monitoring (QCM-D) reveal the reversible nature of the restructuring process. The immobilized films are further modified by covalent coupling of two small biomolecules - a hydrophobic peptide and a more hydrophilic one. These attached components influence the hydrophobicity of the layer in a different way the resulting change of the temperature-caused behavior has been studied by CV indicating a different state of the polymer after coupling of the hydrophobic peptide. KW - Stimuli-responsive materials KW - electroanalysis KW - modified electrode KW - bioreceptors KW - peptides KW - surface modification KW - cyclic voltammetry KW - IR ellipsometry KW - quartz crystal microbalance Y1 - 2017 U6 - https://doi.org/10.1016/j.electacta.2017.01.080 SN - 0013-4686 SN - 1873-3859 VL - 229 SP - 325 EP - 333 PB - Elsevier CY - Oxford ER - TY - THES A1 - Nie, Yan T1 - Modulating keratinocyte and induced pluripotent stem cell behavior by microenvironment design or temperature control N2 - Under the in vivo condition, a cell is continually interacting with its surrounding microenvironment, which is composed of its neighboring cells and the extracellular matrix (ECM). These components generate and transmit the microenvironmental signals to regulate the fate and function of the target cells. Except the signals from the microenvironment, stimuli from the ambient environment, such as temperature changes, also play an important in modulating the cell behaviors, which are considered as regulators from the macroenvironment. In this regard, recapitulation of these environmental factors to steer cell function will be of crucial importance for therapeutic purposes and tissue regeneration. Although the role of a variety of environmental factors has been evaluated, it is still challenging to identify and provide the appropriate factors, which are required for optimizing the survival of cells and for ensuring effective cell functions. Thus, in vitro recreating the environmental factors that are present in the extracellular environment would help to understand the mechanism of how cells sense and process those environmental signals. In this context, this thesis is aimed to harness these environmental parameters to guide cell responses. Here, human induced pluripotent stem cells (hiPSCs) and human keratinocytes (KTCs), HaCaT cells, were used to investigate the impact of signals from the microenvironment or stimuli from the macroenvironment. Firstly, polydopamine (PDA) or chitosan (CS) modifications were applied to generate different substrate surfaces for hiPSCs and KTCs (Chapter 4 to Chapter 6). Our results showed that the PDA modification was efficient to increase the cell-substrate adhesion and consequently promoted cell spreading. While CS modification was able to decrease the cell-substrate adhesion and enhance the cell-cell interaction, which enabled the morphology shift from monolayered cells to multicellular spheroids. The quantitative result was acquired using the atomic force microscopy (AFM)-based single-cell force spectroscopy. The balance between the cell-substrate and cell-cell adhesion yielded a net force, which determined the preference of the cell to adhere to its neighboring cells or to the substrate. The difference in the adhesive behaviors further affected the cellular function, such as the proliferation and differentiation potential of both hiPSCs and HaCaT cells. Next, the cyclic temperature changes (ΔT) were selected here to study the influence of macroenvironmental stimuli on hiPSCs and KTCs (Chapter 7 and Chapter 8). The macroenvironmental temperature ranging from 10.0 ± 0.1 °C to 37.0 ± 0.1 °C was achieved using a thermal chamber equipped with a temperature controller. This temperature range was selected to explore the responses of hiPSCs to the extreme environments, while a temperature variation between 25.0 ± 0.1 °C and 37.0 ± 0.1 °C was applied to mimic the ambient temperature variations experienced by the skin epithelial KTCs. The ΔT led to cell stiffening in both hiPSCs and HaCaT cells in a cytoskeleton-dependent manner, which was measured by AFM. Specifically, in hiPSCs, the cell stiffening was resulted from the rearrangement of the actin skeleton; in HaCaT cells, was due to the difference of the Keratin (KRT) filaments. Except for inducing cell hardening, ΔT also caused differences in the protein expression profiles in hiPSCs or HaCaT cells, compared to those without ΔT treatment, which might be attributed to the alterations in their cytoskeleton structures. To sum up, the results of the thesis demonstrated how individual factors from the micro-/macro-environment can be harnessed to modulate the behaviors of hiPSCs and HaCaT cells. Engineering the microenvironmental cues using surface modification and exploiting the macroenvironmental stimuli through temperature control were identified as precise and potent approaches to steer hiPSC and HaCaT cell behaviors. The application of AFM served as a non-invasive and real-time monitoring platform to trace the change in cell topography and mechanics induced by the environmental signals, which provide novel insights into the cell-environment interactions. N2 - In vivo interagiert eine Zelle ständig mit ihrer Mikroumgebung, die aus ihren Nachbarzellen und der extrazellulären Matrix (ECM) besteht. Diese Komponenten erzeugen und übertragen die Mikroumgebungssignale, um das Schicksal und die Funktion der Zielzellen zu regulieren. Außer den Signalen aus der Mikroumgebung spielen auch Reize aus der Makroumgebung, wie Temperaturänderungen, eine wichtige Rolle bei der Modulation des Zellverhaltens. In dieser Hinsicht ist es wichtig, diese Umweltfaktoren zur Steuerung der Zellfunktion für therapeutische Zwecke und die Geweberegeneration zu rekapitulieren. Es stellt sich immer noch eine Herausforderung, geeignete Faktoren zu identifizieren und bereitzustellen, die zur Optimierung des Überlebens von Zellen und zur Sicherstellung effektiver Zellfunktionen erforderlich sind. Daher würde die in vitro-Nachbildung der Umweltfaktoren helfen, den Mechanismus zu verstehen, wie Zellen diese Umweltsignale wahrnehmen und verarbeiten. In diesem Zusammenhang zielt diese Dissertation darauf ab, diese externen Parameter zu nutzen, um Zellantworten zu steuern. Hier wurden humaninduzierte pluripotente Stammzellen (hiPSCs) und humane Keratinozyten (KTCs) wie HaCaT-Zellen verwendet, um den Einfluss von Signalen aus der Mikroumgebung oder Stimuli aus der Makroumgebung zu untersuchen. Zunächst wurden Modifikationen mit Polydopamin (PDA) oder Chitosan (CS) angewendet, um unterschiedliche Substratoberflächen für hiPSCs und KTCs zu erzeugen (Kapitel 4 bis Kapitel 6). Unsere Ergebnisse zeigten, dass die PDA-Modifikation die Zell-Substrat-Adhäsion erhöhte und folglich die Zellausbreitung förderte. Während die CS-Modifikation die Zell-Substrat-Adhäsion verringerte und die Zell-Zell-Interaktion verstärkte, verändeite sich die Morphologie von einschichtigen Zellen zu mehrzelligen Sphäroiden. Das quantitative Ergebnis wurde mittels Rasterkraftmikroskopie (AFM)-basierter Einzelzellkraftspektroskopie gewonnen. Das Gleichgewicht zwischen Zell-Substrat und Zell-Zell-Adhäsion ergab eine Nettokraft, die die Präferenz der Zelle bestimmt, an ihren Nachbarzellen oder am Substrat zu haften. Der Unterschied im Adhäsionsverhalten beeinflusste außerdem die Zellfunktion, wie das Proliferations- und Differenzierungspotential von hiPSCs und HaCaT-Zellen. Als nächstes wurden hier zyklische Temperaturänderungen (ΔT) ausgewählt, um den Einfluss von Stimuli aus der Makroumgebung auf hiPSCs und KTCs zu untersuchen (Kapitel 7 und Kapitel 8). Die Makroumgebungstemperatur im Bereich von 10,0 ± 0,1 °C bis 37,0 ± 0,1 °C wurde unter Verwendung einer mit einem Temperaturregler ausgestatteten Wärmekammer erreicht. Dieser Temperaturbereich wurde gewählt, um die Reaktion von hiPSCs auf extreme Umgebungen zu untersuchen, während eine Temperaturvariation zwischen 25,0 ± 0,1 ° C und 37,0 ± 0,1 ° C angewendet wurde, um die Temperaturänderungen nachzuahmen, die die Epithelzellen erfahren. Das ΔT führte zytoskelettabhängig zu einer Zellversteifung sowohl in hiPSCs als auch in HaCaT-Zellen, die mittels AFM gemessen wurde. Insbesondere bei hiPSCs resultierte die Zellversteifung aus der Neuordnung des Aktinskeletts; in HaCaT-Zellen, war auf den Unterschied der Keratin (KRT)-Filamente zurückzuführen. Abgesehen von der festgestellten Erhärtung der Zellen verursachte ΔT auch Unterschiede in den Proteinexpressionsprofilen in hiPSCs oder HaCaT-Zellen im Vergleich zu denen ohne ΔT-Behandlung. Dies könnte auf die Veränderungen in ihren Zytoskelettstrukturen zurückgeführt werden. Zusammenfassend zeigten die Ergebnisse, wie die drei Faktoren (PDA/CS-Modifikation und ΔT) aus der Mikro-/Makroumgebung genutzt werden können, um das Verhalten von hiPSCs und HaCaT-Zellen zu modulieren. Als präzise und wirksame Ansätze zur Steuerung des hiPSC- und HaCaT-Zellen-Verhaltens wurde das Engineering der Mikroumgebungssignale durch Oberflächenmodifikation und die Nutzung der Makroumgebungsreize durch Temperaturkontrolle identifiziert. Die Anwendung von AFM diente als nicht-invasive und Echtzeit-Überwachungsplattform, um die durch die Umweltsignale induzierten Veränderungen der Zelltopographie und -mechanik zu verfolgen, die neue Einblicke in die Zell-Umwelt-Interaktionen liefern. KW - human induced pluripotent stem cells KW - human keratinocytes KW - cell-environment interactions KW - surface modification KW - temperature variations KW - humaninduzierte pluripotente Stammzellen KW - humane Keratinozyten KW - Zell-Umwelt-Interaktionen KW - Oberflächenmodifikation KW - Temperaturänderungen Y1 - 2022 ER - TY - JOUR A1 - Schneider, Matthias A1 - Fritzsche, Nora A1 - Puciul-Malinowska, Agnieszka A1 - Balis, Andrzej A1 - Mostafa, Amr A1 - Bald, Ilko A1 - Zapotoczny, Szczepan A1 - Taubert, Andreas T1 - Surface etching of 3D printed poly(lactic acid) with NaOH: a systematic approach JF - Polymers N2 - The article describes a systematic investigation of the effects of an aqueous NaOH treatment of 3D printed poly(lactic acid) (PLA) scaffolds for surface activation. The PLA surface undergoes several morphology changes and after an initial surface roughening, the surface becomes smoother again before the material dissolves. Erosion rates and surface morphologies can be controlled by the treatment. At the same time, the bulk mechanical properties of the treated materials remain unaltered. This indicates that NaOH treatment of 3D printed PLA scaffolds is a simple, yet viable strategy for surface activation without compromising the mechanical stability of PLA scaffolds. KW - surface modification KW - sodium hydroxide etching KW - poly(lactic acid) KW - 3D printing KW - roughness KW - wettability KW - erosion Y1 - 2020 VL - 12 IS - 8 PB - MDPI CY - Basel ER - TY - JOUR A1 - Lange, Ilja A1 - Reiter, Sina A1 - Paetzel, Michael A1 - Zykov, Anton A1 - Nefedov, Alexei A1 - Hildebrandt, Jana A1 - Hecht, Stefan A1 - Kowarik, Stefan A1 - Woell, Christof A1 - Heimel, Georg A1 - Neher, Dieter T1 - Tuning the work function of polar zinc oxide surfaces using modified phosphonic acid self-assembled monolayers JF - Advanced functional materials N2 - Zinc oxide (ZnO) is regarded as a promising alternative material for transparent conductive electrodes in optoelectronic devices. However, ZnO suffers from poor chemical stability. ZnO also has a moderate work function (WF), which results in substantial charge injection barriers into common (organic) semiconductors that constitute the active layer in a device. Controlling and tuning the ZnO WF is therefore necessary but challenging. Here, a variety of phosphonic acid based self-assembled monolayers (SAMs) deposited on ZnO surfaces are investigated. It is demonstrated that they allow the tuning the WF over a wide range of more than 1.5 eV, thus enabling the use of ZnO as both the hole-injecting and electron-injecting contact. The modified ZnO surfaces are characterized using a number of complementary techniques, demonstrating that the preparation protocol yields dense, well-defined molecular monolayers. KW - ZnO KW - self-assembled monolayers KW - phosphonic acid KW - surface modification KW - electrodes Y1 - 2014 U6 - https://doi.org/10.1002/adfm.201401493 SN - 1616-301X SN - 1616-3028 VL - 24 IS - 44 SP - 7014 EP - 7024 PB - Wiley-VCH CY - Weinheim ER -