Filtern
Volltext vorhanden
- nein (163)
Erscheinungsjahr
Dokumenttyp
- Wissenschaftlicher Artikel (163) (entfernen)
Gehört zur Bibliographie
- ja (163)
Schlagworte
- biomaterials (7)
- Polymer (6)
- shape-memory effect (6)
- biomaterial (5)
- polymer (5)
- stimuli-sensitive polymers (5)
- Biomaterial (4)
- shape memory (4)
- Degradation (3)
- Hydrogel (3)
- Langmuir monolayer (3)
- cell adhesion (3)
- endothelial cells (3)
- hemocompatibility (3)
- mesenchymal stem cells (3)
- microparticles (3)
- multiblock copolymer (3)
- Actuation (2)
- Biomaterials (2)
- Biomimetic (2)
- Biopolymer (2)
- Degradable (2)
- Depsipeptide (2)
- Hyaluronic acid (2)
- Membrane (2)
- Molecular modeling (2)
- Nanostructure (2)
- Oligo(epsilon-caprolactone) (2)
- Phase morphology (2)
- Poly(epsilon-caprolactone) (2)
- Polymers (2)
- Rheology (2)
- Shape memory (2)
- Shape-memory effect (2)
- Shape-memory polymer (2)
- Temperature-memory effect (2)
- Thin film (2)
- actuation (2)
- artificial muscles (2)
- atomic force microscopy (2)
- crystallization (2)
- crystallization behavior (2)
- degradation (2)
- electrospinning (2)
- ellipsometry (2)
- hydrogels (2)
- mechanical (2)
- morphology (2)
- oligodepsipeptides (2)
- phase morphology (2)
- platelets (2)
- poly(epsilon-caprolactone) (2)
- poly(ethylene glycol) (2)
- polyester (2)
- polyesterurethanes (2)
- properties (2)
- ring-opening polymerization (2)
- shape-memory polymers (2)
- soft actuators (2)
- soft robotics (2)
- spectroscopic ellipsometry (2)
- surface functionalization (2)
- (NMR) (1)
- 2D materials (1)
- 3D-printing (1)
- 4D-actuation (1)
- Actuators (1)
- Additive manufacturing (1)
- Adipocyte (1)
- Adsorption of uremic toxins (1)
- Aerophobicity (1)
- Ageing (1)
- Air bubble repellence (1)
- Angle-dependent X-ray induced photoelectron spectroscopy (1)
- Antiviral (1)
- Biocompatible polymers (1)
- Biomolecules coupling (1)
- Biopolymer material (1)
- Biopolymers (1)
- Brewster angle microscopy (1)
- COVID-19 (1)
- Cartilage repair (1)
- Chronic kidney disease (1)
- Chronic kidney disease (CKD) (1)
- Cinnamylidene acetic acid (1)
- Click chemistry (1)
- Collagen-binding peptide (1)
- Crosslinking (1)
- Deformation (1)
- Docking study (1)
- Drug loading (1)
- Electrospinning (1)
- Energy (1)
- Energy storage (1)
- Enzymatic degradation (1)
- Enzymatic polymer degradation (1)
- Fastener (1)
- Fiber (1)
- Function by design (1)
- Functionalization (1)
- Gelatin (1)
- Gripper (1)
- HDAC1 (1)
- High-throughput (1)
- Hydrogels (1)
- Hydrolytic degradation (1)
- Hydrolytic stability (1)
- Hypoxia (1)
- In situ (1)
- Inflammation (1)
- Ink (1)
- Ki67 (1)
- Langmuir layers (1)
- Langmuir monolayer degradation technique (1)
- Langmuir monolayers (1)
- Langmuir technique (1)
- Langmuir thin-films (1)
- Langmuir-Schafer films (1)
- Macrophage (1)
- Magnetic composites (1)
- Magnetite nanoparticles (1)
- Mass spectrometry (1)
- Matrix metalloproteinase (1)
- Mechanical properties (1)
- Methacrylate (1)
- Microindentation (1)
- Microstructure (1)
- Modeling (1)
- Modelling (1)
- Molecular (1)
- Molecular dynamics simulation (1)
- Molecular interaction design (1)
- Molecular orientation (1)
- Molecular weight (1)
- Morpholindione (1)
- Multiblock copolymer (1)
- Multiblock copolymers (1)
- Multifunctional polyester networks (1)
- Multifunctionality (1)
- NICE-2014 (1)
- Nanofiber (1)
- Nanoparticles (1)
- Near infrared light triggered shape-recovery (1)
- Negative control (1)
- Nuclear magnetic resonance (1)
- Oligo(ethylene glycol) (1)
- Oligo(omega-pentadecalactone) (1)
- Oligodepsipeptide (1)
- Oligoglycerols (1)
- On-demand release (1)
- PDLLGA (1)
- PHA-depolymerases (1)
- Packaging (1)
- Particle shape (1)
- Particle size (1)
- Phagocytosis (1)
- Photoresponsive polymers (1)
- Physical Network (1)
- Platelet (1)
- Poly(carbonate-urea-urethane)s (1)
- Poly(epsilon-caprolactone) networks (1)
- Poly(ether imide) (1)
- Poly(n-butyl acrylate) (1)
- Polyesterurethane (1)
- Polyether ether ketone (1)
- Polylactide stereocomplex (1)
- Polymer architecture (1)
- Polymer functionalization (1)
- Polymer micronetwork colloids (1)
- Polymer network properties (1)
- Polymer networks (1)
- Polymeric substrate (1)
- Porous poly(ether imide) microparticulate absorbers (1)
- Protein (1)
- Proteins (1)
- RGD peptides (1)
- RGD-peptide (1)
- RUNX2 (1)
- Raman spectroscopy (1)
- Random copolymer (1)
- Ring-opening polymerization (1)
- Robotic synthesis (1)
- Robotics (1)
- SAXS (1)
- Scaffold contraction (1)
- Scaffold degradation (1)
- Scaffold stiffness (1)
- Scanning probe microscopy (SPM) (1)
- Sequence structure (1)
- Shape-memory (1)
- Simulation (1)
- Sn(IV) alkoxide (1)
- Submicron particles (1)
- Surface functionalization (1)
- Surface reaction (1)
- Surfactants (1)
- Switchable wettability (1)
- TCP (1)
- THP-1 cells (1)
- Telechel (1)
- Thermo-responsive polymer (1)
- Thermomechanical history (1)
- Tin octanoate (1)
- Uremic toxins (1)
- VEGF (1)
- WAXS (1)
- Water (1)
- X-ray scattering (1)
- actin cytoskeleton (1)
- active polymer (1)
- active scaffold (1)
- amide ligand (1)
- amorphous polymers (1)
- assembly capabilities (1)
- atomic force microscopy (AFM) (1)
- basement membrane (1)
- beta-galactosidase (1)
- biocompatibility (1)
- biodegradable polymers (1)
- biofunctionalization (1)
- bioinspired materials (1)
- bioinstructive implants (1)
- bioinstructive materials (1)
- biological applications of polymers (1)
- biological membrane (1)
- biomaterial-tissue interface (1)
- biomedical (1)
- biomimetic (chemical reaction) (1)
- biopolymer (1)
- bioprinting (1)
- blend (1)
- block copolymers (1)
- body temperature (1)
- brewster angle microscopy (1)
- broad melting temperature range (1)
- calcium influx (1)
- cardiac regeneration (1)
- cardiovascular disease (1)
- cardiovascular implant (1)
- catalyst (1)
- cavitation-based mechanical force (1)
- cell culture device (1)
- cell cycle inhibitors (1)
- cell-material interaction (1)
- chain-extended (1)
- chemical synthesis (1)
- chronic kidney disease (CKD) (1)
- cold (1)
- collagen (1)
- collagen-IV (1)
- composite (1)
- controlled release (1)
- coordination bonds (1)
- copolymer networks (1)
- copper-catalyzed alkyne-azide cycloaddition (1)
- critical micellation temperature (1)
- cross-linking (1)
- crosslinking (1)
- crystal structures (1)
- crystalline (1)
- crystallinity (1)
- cyclic olefin copolymer (1)
- cyclic thermomechanical testing (1)
- cyclodextrin (1)
- cytotoxicity (1)
- dedifferentiation (1)
- degradable (1)
- degradable polyester (1)
- dendritic cells (1)
- elastomers (1)
- electron microscopy (1)
- ellipsometric mapping (1)
- endothelial basement membrane (1)
- engineering (1)
- enzymatic-degradation (1)
- enzyme (1)
- excimer UV light (1)
- extracellular matrix modifying enzymes (1)
- fiber actuators (1)
- fiber meshes (1)
- fibers (1)
- fibrinogen (1)
- fibroblast (1)
- fluorescence stimuli‐ responsivity (1)
- foam (1)
- focal adhesion (1)
- form stability (1)
- function by structure; (1)
- functional (1)
- functionalization of polymers (1)
- gelatin (1)
- gelatin-based hydrogels (1)
- gels (1)
- glass (1)
- hemodialysis (1)
- human monocytic (THP-1) cells (1)
- hydrogel (1)
- hydrophobic uremic toxins (1)
- in vitro thrombogenicity testing (1)
- inclusion complex (1)
- induced pluripotent stem cells (1)
- inverse (1)
- iron (1)
- langmuir monolayer (1)
- libraries (1)
- library (1)
- life cycle assessment (1)
- lipase release (1)
- lipases (1)
- lipid (1)
- liquid-crystalline polymers (1)
- magnetic (1)
- magnetic nanoparticles (1)
- magnetosensitivity (1)
- materials science (1)
- mechanical property (1)
- microgels (1)
- microporous (1)
- microstructure (1)
- modulation of in vivo regeneration (1)
- molecular dynamics simulations (1)
- molecular modeling (1)
- multiblock copolymers (1)
- multifunctional biomaterials (1)
- multifunctional polymers (1)
- multiple functions (1)
- nanocomposites (1)
- nanoparticle characterization (1)
- nanostructure (1)
- networks (1)
- on demand particle release (1)
- optical imaging (1)
- orientational memory (1)
- osteogenic differentiation (1)
- oxygen plasma (1)
- p16 (1)
- p21 (1)
- particulate (1)
- peptides (1)
- photoinduced radical polymerization (1)
- platelet activation (1)
- platelet adhesion (1)
- platelet aging (1)
- platelet function (1)
- platelet rich plasma (1)
- platelet storage (1)
- platelet-rich plasma (1)
- poly(e-caprolactone) (1)
- poly(epsilon-caprolactone) methacrylate (1)
- poly(ether imide) (1)
- poly(ether imide) microparticles (1)
- poly(n-butyl acrylate) (1)
- poly(tetrafluoroethylene) (1)
- poly[(rac-lactide)-co-glycolide] (1)
- polyamines (1)
- polycaprolactone (1)
- polydepsipeptide (1)
- polyesters (1)
- polyesterurethane (1)
- polyglycerol (1)
- polyhydroxyalkanoates (PHA) (1)
- polyimides (1)
- polymer actuators (1)
- polymer surface (1)
- polymers (1)
- polysiloxanes (1)
- population doubling time (1)
- porosity (1)
- processing (1)
- protein (1)
- protein adsorption (1)
- protein-protein interactions (1)
- reactive oxygen species (ROS) (1)
- reference (1)
- renewable (1)
- reshaping abilities (1)
- resistive heating (1)
- responsive (1)
- reversible bidirectional shape-memory polymer (1)
- reversible shape-memory actuator (1)
- reversible shape-memory effect (1)
- rheology (1)
- rhodium(I)– phosphine (1)
- rhodium-phosphine coordination bonds (1)
- ring opening polymerization (1)
- root mean square roughness (1)
- self-healing (1)
- semi-IPN hydrogels (1)
- semi-crystalline (1)
- senescence-associated (1)
- sequence structures (1)
- shape change (1)
- shape shifting materials (1)
- shape-memory (1)
- shape-memory hydrogel (1)
- shape-memory polymer (1)
- shape-memory polymer actuators (1)
- shape-memory properties (1)
- shape‐memory polymer actuators (1)
- side reaction (1)
- side-chains functionalization (1)
- soft matter micro- and nanowires (1)
- solvent resistance (1)
- stem cell adhesion (1)
- stereocomplexes (1)
- stimuli-sensitive materials (1)
- supramolecular polymer network (1)
- surface chemistry (1)
- surface coating (1)
- sustainability (1)
- switch (1)
- telechelics (1)
- temperature (1)
- temperature-memory effect (1)
- temperature-memory polymers (1)
- thermal properties (1)
- thermal treatments (1)
- thermo-sensitivity (1)
- thermomechanical properties (1)
- thermoplastic elastomer (1)
- thermoplastics (1)
- thermoresponsive polymers (1)
- thermosensitive (1)
- thrombocyte adhesion (1)
- thrombogenicity (1)
- tin(II) 2-ethylhexanoate (1)
- tissue (1)
- triple-shape effect (1)
- two dimensional network (1)
- ultrasound (1)
- uremia (1)
- vascular graft (1)
- vascular grafts (1)
- viability (1)
- whole blood (1)
- wide angle x‐ ray scattering (1)
Institut
- Institut für Chemie (163) (entfernen)
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.
Shape-Memory Capability of Copolyetheresterurethane Microparticles Prepared via Electrospraying
(2015)
Multifunctional thermo-responsive and degradable microparticles exhibiting a shapememory effect (SME) have attracted widespread interest in biomedicine as switchable delivery vehicles or microactuators. In this work almost spherical solid microparticles with an average diameter of 3.9 +/- 0.9 mm are prepared via electrospraying of a copolyetheresterurethane named PDC, which is composed of crystallizable oligo(p-dioxanone) (OPDO) hard and oligo(e-caprolactone) (OCL) switching segments. The PDC microparticles are programmed via compression at different pressures and their shapememory capability is explored by off-line and online heating experiments. When a low programming pressure of 0.2 MPa is applied a pronounced thermally-induced shape-memory effect is achieved with a shape recovery ratio about 80%, while a high programming pressure of 100 MPa resulted in a weak shape-memory performance. Finally, it is demonstrated that an array of PDC microparticles deposited on a polypropylene (PP) substrate can be successfully programmed into a smart temporary film, which disintegrates upon heating to 60 degrees C.
Fibrous membranes capable of dynamically responding to external stimuli are highly desirable in textiles and biomedical materials, where adaptive behavior is required to accommodate complex environmental changes. For example, the creation of fabrics with temperature-dependent moisture permeability or self-regulating membranes for air filtration is dependent on the development of materials that exhibit a reversible stimuli-responsive pore size change. Here, by imbuing covalently crosslinked poly(ε-caprolactone) (cPCL) fibrous meshes with a reversible bidirectional shape-memory polymer actuation (rbSMPA) we create a material capable of temperature-controlled changes in porosity. Cyclic thermomechanical testing was used to characterize the mechanical properties of the meshes, which were composed of randomly arranged microfibers with diameters of 2.3 ± 0.6 μm giving an average pore size of approx. 10 μm. When subjected to programming strains of εm = 300% and 100% reversible strain changes of εʹrev = 22% ± 1% and 6% ± 1% were measured, with switching temperature ranges of 10 °C–30 °C and 45 °C–60 °C for heating and cooling, respectively. The rbSMPA of cPCL fibrous meshes generated a microscale reversible pore size change of 11% ± 3% (an average of 1.5 ± 0.6 μm), as measured by scanning electron microscopy. The incorporation of a two-way shape-memory actuation capability into fibrous meshes is anticipated to advance the development and application of smart membrane materials, creating commercially viable textiles and devices with enhanced performance and novel functionality.
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.
Inspired by the application of ultrasonic cavitation based mechanical force (CMF) to open small channels in natural soft materials (skin or tissue), it is explored whether an artificial polymer network can be created, in which shape-changes can be induced by CMF. This concept comprises an interconnected macroporous rhodium-phosphine (Rh-P) coordination polymer network, in which a CMF can reversibly dissociate the Rh-P microphases. In this way, the ligand exchange of Rh-P coordination bonds in the polymer network is accelerated, resulting in a topological rearrangement of molecular switches. This rearrangement of molecular switches enables the polymer network to release internal tension under ultrasound exposure, resulting in a CMF-induced shape-memory capability. The interconnected macroporous structure with thin pore walls is essential for allowing the CMF to effectively permeate throughout the polymer network. Potential applications of this CMF-induced shape-memory polymer can be mechanosensors or ultrasound controlled switches.
Chemoresponsive polymers are of technological significance for smart sensors or systems capable of molecular recognition. An important key requirement for these applications is the material’s structural integrity after stimulation. We explored whether covalently cross-linked metal ion–phosphine coordination polymers (MPN) can be shaped into any temporary shape and are capable of recovering from this upon chemoresponsive exposure to triphenylphosphine (Ph3P) ligands, whereas the MPN provide structural integrity. Depending on the metal-ion concentration used during synthesis of the MPN, the degree of swelling of the coordination polymer networks could be adjusted. Once the MPN was immersed into Ph3P solution, the reversible ligand-exchange reaction between the metal ions and the free Ph3P in solution causes a decrease of the coordination cross-link density in MPN again. The Ph3P-treated MPN was able to maintain its original shape, indicating a certain stability of shape even after stimulation. In this way, chemoresponsive control of the elastic properties (increase in volume and decrease of mechanical strength) of the MPN was demonstrated. This remarkable behavior motivated us to explore whether the MPN are capable of a chemoresponsive shape-memory effect. In initial experiments, shape fixity of around 60% and shape recovery of almost 90% were achieved when the MPN was exposed to Ph3P in case of rhodium. Potential applications for chemoresponsive shape-memory systems could be shapable semiconductors, e.g., for lighting or catalysts, which provide catalytic activity on demand.
On-demand motion of highly swollen polymer systems can be triggered by changes in pH, ion concentrations, or by heat. Here, shape-programmable, architectured hydrogels are introduced, which respond to ultrasonic-cavitation-based mechanical forces (CMF) by directed macroscopic movements. The concept is the implementation and sequential coupling of multiple functions (swellability in water, sensitivity to ultrasound, shape programmability, and shape-memory) in a semi-interpenetrating polymer network (s-IPN). The semi-IPN-based hydrogels are designed to function through rhodium coordination (Rh-s-IPNH). These coordination bonds act as temporary crosslinks. The porous hydrogels with coordination bonds (degree of swelling from 300 +/- 10 to 680 +/- 60) exhibit tensile strength sigma(max) up to 250 +/- 60 kPa. Shape fixity ratios up to 90% and shape recovery ratios up to 94% are reached. Potential applications are switches or mechanosensors.
Biomaterials are used in regenerative medicine for induced autoregeneration and tissue engineering. This is often challenging, however, due to difficulties in tailoring and controlling the respective material properties. Since functionalization is expected to offer better control, in this study gelatin chains were modified with physically interacting groups based on tyrosine with the aim of causing the formation of physical crosslinks. This method permits application-specific properties like swelling and better tailoring of mechanical properties. The design of the crosslink strategy was supported by molecular dynamic (MD) simulations of amorphous bulk models for gelatin and functionalized gelatins at different water contents (0.8 and 25 wt.-%). The results permitted predictions to be formulated about the expected crosslink density and its influence on equilibrium swelling behavior and on elastic material properties. The models of pure gelatin were used to validate the strategy by comparison between simulated and experimental data such as density, backbone conformation angle distribution, and X-ray scattering spectra. A key result of the simulations was the prediction that increasing the number of aromatic functions attached to the gelatin chain leads to an increase in the number of physical netpoints observed in the simulated bulk packing models. By comparison with the Flory-Rehner model, this suggested reduced equilibrium swelling of the functionalized materials in water, a prediction that was subsequently confirmed by our experimental work. The reduction and control of the equilibrium degree of swelling in water is a key criterion for the applicability of functionalized gelatins when used, for example, as matrices for induced autoregeneration of tissues.
Classic rotating engines are powerful and broadly used but are of complex design and difficult to miniaturize. It has long remained challenging to make large-stroke, high-speed, high-energy microengines that are simple and robust. We show that torsionally stiffened shape memory nanocomposite fibers can be transformed upon insertion of twist to store and provide fast and high-energy rotations. The twisted shape memory nanocomposite fibers combine high torque with large angles of rotation, delivering a gravimetric work capacity that is 60 times higher than that of natural skeletal muscles. The temperature that triggers fiber rotation can be tuned. This temperature memory effect provides an additional advantage over conventional engines by allowing for the tunability of the operation temperature and a stepwise release of stored energy.
N-terminal methacrylation of peptide MAXI, which is capable of conformational changes variation of the pH, results in a peptide, named VK20. Increasing the reactivity of this terminal group enables further coupling reactions or chemical modifications of the peptidc. However, this end group functionalization may influence the ability of confonnational changes of VK20; as well as its properties. In this paper; the influence of pH on the transition between random coil and beta-sheet conformation of VK20; including the transition kinetics, were investigated. At pH values of 9 and higher, the kinetics beta-sheet formation increased tor VK(2 0, compared to MAXI. The self-assembly into beta-sheets recognized by the formation of a physically crosslinked gel was furthermore indicated by a significant increase of G. An increase in pH (from 9 to 9.5) led to a faster gelation of the peptide VK20. Simultaneously, G was increased from 460 +/- 70 Pa (at pH 9) to 1520 +/- 180 Pa (at pH 9.5). At the nanoscale, the gel showed a highly interconnected fibrillar/network structure with uniform fibril widths of approximately 3.4 +/- 0.5 nm (N=30). The recovery of the peptide conformation back to random coil resulted in the dissolution of the gel; whereby the kinetics of the recovery depended on the pH. Conclusively, the ability of MAXI to undergo confommtional changes was not affected by N-terminal methacrylation whereas the kinetics of pH-sensitive beta-sheet formations has been increased.
Polymeric materials possessing specific features like programmability, high deformability, and easy processability are highly desirable for creating modern actuating systems. In this study, thermoplastic shape-memory polymer actuators obtained by combining crystallizable poly(epsilon-caprolactone) (PCL) and poly(3S-isobutylmorpholin-2,5-dione) (PIBMD) segments in multiblock copolymers are described. We designed these materials according to our hypothesis that the confinement of glassy PIBMD domains present at the upper actuation temperature contribute to the stability of the actuator skeleton, especially at large programming strains. The copolymers have a phase-segregated morphology, indicated by the well-separated melting and glass transition temperatures for PIBMD and PCL, but possess a partially overlapping T-m of PCL and T-g of PIBMD in the temperature interval from 40 to 60 degrees C. Crystalline PIBMD hard domains act as strong physical netpoints in the PIBMD-PCL bulk material enabling high deformability (up to 2000%) and good elastic recoverability (up to 80% at 50 degrees C above T-m,T-PCL). In the programmed thermoplastic actuators a high content of crystallizable PCL actuation domains ensures pronounced thermoreversible shape changes upon repetitive cooling and heating. The programmed actuator skeleton, composed of PCL crystals present at the upper actuation temperature T-high and the remaining glassy PIBMD domains, enabled oriented crystallization upon cooling. The actuation performance of PIBMD-PCL could be tailored by balancing the interplay between actuation and skeleton, but also by varying the quantity of crystalline PIBMD hard domains via the copolymer composition, the applied programming strain, and the choice of T-high. The actuator with 17 mol% PIBMD showed the highest reversible elongation of 11.4% when programmed to a strain of 900% at 50 degrees C. It is anticipated that the presented thermoplastic actuator materials can be applied as modern compression textiles.
Degradable multiblock copolymers prepared from equal weight amounts of poly(epsilon-caprolactone)-diol (PCL-diol) and poly[oligo(3S-iso-butylmorpholine-2,5-dione)]-diol (PIBMD-diol), named PCL-PIBMD, provide a phase-segregated morphology. It exhibits a low melting temperature from PCL domains (T-m,T-PCL) of 382 degrees C and a high T-m,T-PIBMD of 170 +/- 2 degrees C with a glass transition temperature (T-g,T-PIBMD) at 42 +/- 2 degrees C from PIBMD domains. In this study, we explored the influence of applying different thermal treatments on the resulting morphologies of solution-cast and spin-coated PCL-PIBMD thin films, which showed different initial surface morphologies. Differential scanning calorimetry results and atomic force microscopy images after different thermal treatments indicated that PCL and PIBMD domains showed similar crystallization behaviors in 270 +/- 30 mu m thick solution-cast films as well as in 30 +/- 2 and 8 +/- 1nm thick spin-coated PCL-PIBMD films. Existing PIBMD crystalline domains highly restricted the generation of PCL crystalline domains during cooling when the sample was annealed at 180 degrees C. By annealing the sample above 120 degrees C, the PIBMD domains crystallized sufficiently and covered the free surface, which restricted the crystallization of PCL domains during cooling. The PCL domains can crystallize by hindering the crystallization of PIBMD domains via the fast vitrification of PIBMD domains when the sample was cooled/quenched in liquid nitrogen after annealing at 180 degrees C. These findings contribute to a better fundamental understanding of the crystallization mechanism of multi-block copolymers containing two crystallizable domains whereby the T-g of the higher melting domain type is in the same temperature range as the T-m of the lower melting domain type. Copyright (c) 2016 John Wiley & Sons, Ltd.
A multiblock copolymer termed as PCL-PIBMD, consisting of crystallizable poly(epsilon-caprolactone) (PCL) segments and crystallizable poly(3S-isobutyl-morpholine-2,5-dione) (PIBMD) segments, has been reported as a material showing a thermally-induced shape-memory effect. While PIBMD crystalline domains act as netpoints to determine the permanent shape, both PCL crystalline domains and PIBMD amorphous domains, which have similar transition temperatures (T-trans) can act as switching domains. In this work, the influence of the deformation temperature (T-deform = 50 or 20 degrees C), which was above or below T-trans, on the structural changes of PCL-PIBMD during uniaxial deformation and the shapememory properties were investigated. Furthermore, the relative contribution of crystalline PCL and PIBMD amorphous phases to the fixation of the temporary shape were distinguished by a toluene vapor treatment approach. The results indicated that at 50 degrees C, both PCL and PIBMD amorphous phases can be orientated during deformation, resulting in thermally-induced crystals of PCL domains and joint contribution to the switching domains. In contrast at 20 degrees C, the temporary shape was mainly fixed by PCL crystals generated via strain-induced crystallization.
Multiblock copolymers named PCL-PIBMD consisting of crystallizable poly(epsilon-caprolactone) segments and crystallizable poly[oligo(3S-iso-butylmorpholine-2,5-dione)] segments coupled by trimethyl hexamethylene diisocyanate provide a versatile molecular architecture for achieving shape-memory effects (SMEs) in polymers. The mechanical properties as well as the SME performance of PCL-PIBMD can be tailored by the variation of physical parameters during programming such as deformation strain or applied temperature protocols. In this study, we explored the influence of applying different strain rates during programming on the resulting nanostructure of PCL-PIBMD. Programming was conducted at 50 degrees C by elongation to epsilon(m)=50% with strain rates of 1 or 10 or 50 mmmin(-1). The nanostructural changes were visualized by atomic force microscopy (AFM) measurements and investigated by in situ wide and small angle X-ray scattering experiments. With increasing the strain rate, a higher degree of orientation was observed in the amorphous domains. Simultaneously the strain-induced formation of new PIBMD crystals as well as the fragmentation of existing large PIBMD crystals occurred. The observed differences in shape fixity ratio and recovery stress of samples deformed with various strain rates can be attributed to their different nanostructures. The achieved findings can be relevant parameters for programming the shape-memory polymers with designed recovery forces. (c) 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 1935-1943
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.
Non-swelling hydrophobic poly(n-butyl acrylate) network (cPnBA) is a candidate material for synthetic vascular grafts owing to its low toxicity and tailorable mechanical properties. Mesenchymal stem cells (MSCs) are an attractive cell type for accelerating endothelialization because of their superior anti-thrombosis and immune modulatory function. Further, they can differentiate into smooth muscle cells or endothelial-like cells and secret pro-angiogenic factors such as vascular endothelial growth factor (VEGF). MSCs are sensitive to the substrate mechanical properties, with the alteration of their major cellular behavior and functions as a response to substrate elasticity. Here, we cultured human adipose-derived mesenchymal stem cells (hADSCs) on cPnBAs with different mechanical properties (cPnBA250, Young’s modulus (E) = 250 kPa; cPnBA1100, E = 1100 kPa) matching the elasticity of native arteries, and investigated their cellular response to the materials including cell attachment, proliferation, viability, apoptosis, senescence and secretion. The cPnBA allowed high cell attachment and showed negligible cytotoxicity. F-actin assembly of hADSCs decreased on cPnBA films compared to classical tissue culture plate. The difference of cPnBA elasticity did not show dramatic effects on cell attachment, morphology, cytoskeleton assembly, apoptosis and senescence. Cells on cPnBA250, with lower proliferation rate, had significantly higher VEGF secretion activity. These results demonstrated that tuning polymer elasticity to regulate human stem cells might be a potential strategy for constructing stem cell-based artificial blood vessels.
Polydepsipeptide Block-Stabilized Polyplexes for Efficient Transfection of Primary Human Cells
(2017)
The rational design of a polyplex gene carrier aims to balance maximal effectiveness of nucleic acid transfection into cells with minimal adverse effects. Depsipeptide blocks with an M (n) similar to 5 kDa exhibiting strong physical interactions were conjugated with PEI moieties (2.5 or 10 kDa) to di- and triblock copolymers. Upon nanoparticle formation and complexation with DNA, the resulting polyplexes (sizes typically 60-150 nm) showed remarkable stability compared to PEI-only or lipoplex and facilitated efficient gene delivery. Intracellular trafficking was visualized by observing fluorescence-labeled pDNA and highlighted the effective cytoplasmic uptake of polyplexes and release of DNA to the perinuclear space. Specifically, a triblock copolymer with a middle depsipeptide block and two 10 kDa PEI swallowtail structures mediated the highest levels of transgenic VEGF secretion in mesenchymal stem cells with low cytotoxicity. These nanocarriers form the basis for a delivery platform technology, especially for gene transfer to primary human cells.
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.
Soft robots and devices with the advanced capability to perform adaptive motions similar to that of human beings often have stimuli-sensitive polymeric materials as the key actuating component. The external signals triggering the smart polymers’ actuations can be transmitted either via a direct physical connection between actuator and controlling unit (tethered) or remotely without a connecting wire. However, the vast majority of such polymeric actuator materials are limited to one specific type of motion as their geometrical information is chemically fixed. Here, we present magnetically driven nanocomposite actuators, which can be reversibly reprogrammed to different actuation geometries by a solely physical procedure. Our approach is based on nanocomposite materials comprising spatially segregated crystallizable actuation and geometry determining units. Upon exposure to a specific magnetic field strength the actuators’ geometric memory is erased by the melting of the geometry determining units allowing the implementation of a new actuator shape. The actuation performance of the nanocomposites can be tuned and the technical significance was demonstrated in a multi-cyclic experiment with several hundreds of repetitive free-standing shape shifts without losing performance.
Background: Magnetic composites of thermosensitive shape-memory polymers (SMPs) and magnetite nanoparticles (MNPs) allow noncontact actuation of the shape-memory effect in an alternating magnetic field. In this study, we investigated whether the magnetic heating capability of cross-linked poly(epsilon-caprolactone)/MNP composites (cPCLC) could be improved by covalent coating of MNPs with oligo(epsilon-caprolactone) (OCL).
Methods: Two different types of cPCLC containing uncoated and OCL-coated MNP with identical magnetite weight content were prepared by thermally induced polymerization of poly(epsilon-caprolactone) diisocyanatoethyl methacrylate. Both cPCLCs exhibited a melting transition at T-m = 48 degrees C, which could be used as switching transition.
Results: The dispersion of the embedded nanoparticles within the polymer matrix could be substantially improved, when the OCL-coated MNPs were used, as visualized by scanning electron microscopy. We could further demonstrate that in this way the maximal achievable bulk temperature (T-bulk) obtained within the cPCLC test specimen in magnetic heating experiments at a magnetic field strength of H = 30 kA.m(-1) could be increased from T bulk = 48 degrees C to T bulk = 74 degrees C.