Shape-Memory Effect by Sequential Coupling of Functions over Different Length Scales in an Architectured Hydrogel.

The integration of functions in materials in order to gain macroscopic effects in response to environmental changes is an ongoing challenge in material science. Here, functions on different hierarchical levels are sequentially linked to translate a pH-triggered conformational transition from the molecular to the macroscopic level to induce directed movements in hydrogels. When the pH is increased, lysine-rich peptide molecules change their conformation into a β-hairpin structure because of the reduced electrostatic repulsion among the deprotonated amino groups.

Unraveling the Interplay between Abiotic Hydrolytic Degradation and Crystallization of Bacterial Polyesters Comprising Short and Medium Side-Chain-Length Polyhydroxyalkanoates.

Polyhydroxyalkanoates (PHAs) have attracted attention as degradable (co)polyesters which can be produced by microorganisms with variations in the side chain. This structural variation influences not only the thermomechanical properties of the material but also its degradation behavior. Here, we used Langmuir monolayers at the air-water (A-W) interface as suitable models for evaluating the abiotic degradation of two PHAs with different side-chain lengths and crystallinity.

Age-related morphology and function of human arterial endothelial cells.

Endothelialization of cardiovascular implants is regarded as a promising strategy for long-term compatibility. While umbilical vein endothelial cells are typically applied in research, human arterial endothelial cells (HAEC) from elderly donors would be the obvious source for autologous cellularization strategies.In our approach, HAEC from 16 donors of varying age (16-63 years) were divided into two groups (<30 years and >30 years) and analyzed regarding morphology, viability, proliferation, function and senescence status.

Controlling Actuation Performance in Physically Cross-Linked Polylactone Blends Using Polylactide Stereocomplexation.

Within the field of shape-changing materials, synthetic chemical modification has been widely used to introduce key structural units and subsequently expand the mechanical functionality of actuator devices. The introduction of architectural elements that facilitate control over mechanical properties and complete geometric reconfiguration of a device is highly desirable to increase the morphological diversity of polymeric actuator materials. The subject of the present study is a multiblock copolymer with semicrystalline poly(l-lactide) and poly(ε-caprolactone) (PLLA-PCL) segments.

Coaxial electrospinning of PEEU/gelatin to fiber meshes with enhanced mesenchymal stem cell attachment and proliferation.

Microfibers with a core-shell structure can be produced by co-axial electrospinning, allowing for the functionalization of the outer layer with bioactive molecules. In this study, a thermoplastic, degradable polyesteretherurethane (PEEU), consisting of poly(p-dioxanone) (PPDO) and poly(ɛ-caprolactone) (PCL) segments with different PPDO to PCL weight ratios, were processed into fiber meshes by co-axial electrospinning with gelatin. The prepared PEEU fibers have a diameter of 1.

Matching Magnetic Heating and Thermal Actuation for Sequential Coupling in Hybrid Composites by Design.

Sequentially coupling two material functions requires matching the output from the first with the input of the second function. Here, magnetic heating controls thermal actuation of a hybrid composite in a challenging system environment causing an elevated level of heat loss. The concept is a hierarchical design consisting of an inner actuator of nanocomposite material, which can be remotely heated by exposure to an alternating magnetic field (AMF) and outer layers of a porous composite system with a closed pore morphology.

Characterization of Tissue Transglutaminase as a Potential Biomarker for Tissue Response toward Biomaterials.

Tissue transglutaminase (TGase 2) is proposed to be important for biomaterial-tissue interactions due to its presence and versatile functions in the extracellular environment. TGase 2 catalyzes the cross-linking of proteins through its Ca-dependent acyltransferase activity. Moreover, it enhances the interactions between fibronectin and integrins, which in turn mediates the adhesion, migration, and motility of the cells.

Elasticity of fiber meshes from multiblock copolymers influences endothelial cell behavior.

Background: The behavior of endothelial cells is remarkably influenced by the physical and biochemical signals from their surrounding microenvironments.

Objective: Here, the elasticity of fiber meshes was studied as a design parameter of substrates for endothelial cells in order to modulate angiogenesis.

Methods: Human umbilical vein endothelial cells (HUVECs) were cultured on electrospun fiber meshes made from polyetheresterurethane (PEEU), differing in their elasticity.

Effects of acrolein in comparison to its prodrug cyclophosphamide on human primary endothelial cells in vitro.

Cyclophosphamide (CPA) is one of the most successful anticancer prodrugs that becomes effective after biotransformation in the liver resulting in the toxic metabolite acrolein. Cancer is often accompanied by thromboembolic events, which might be a result of dysfunctional endothelial cells due to CPA treatment. Here, the effect of 1 mM CPA or acrolein (10/50/100/500 μM) on human umbilical vein endothelial cells (HUVECs) was analyzed after two days of treatment.

In Vitro Thrombogenicity Testing of Biomaterials.

The short- and long-term thrombogenicity of implant materials is still unpredictable, which is a significant challenge for the treatment of cardiovascular diseases. A knowledge-based approach for implementing biofunctions in materials requires a detailed understanding of the medical device in the biological system. In particular, the interplay between material and blood components/cells as well as standardized and commonly acknowledged in vitro test methods allowing a reproducible categorization of the material thrombogenicity requires further attention.

The effect of stiffness variation of electrospun fiber meshes of multiblock copolymers on the osteogenic differentiation of human mesenchymal stem cells.

Electrospinning has attracted significant attention as a method to produce cell culture substrates whose fibrous structure mimics the native extracellular matrix (ECM). In this study, the influence of E-modulus of fibrous substrates on the lineage commitment of human adipose-derived stem cells (hADSCs) was studied using fiber meshes prepared via the electrospinning of a polyetheresterurethane (PEEU) consisting of poly(ρ-dioxanone) (PPDO) and poly(ɛ-caprolactone) (PCL) segments. The PPDO: PCL weight ratio was varied from 40:60 to 70:30 to adjust the physiochemical properties of the PEEU fibers.

Microscale roughness regulates laminin-5 secretion of bone marrow mesenchymal stem cells.

Laminin-5 (Ln-5), an important extracellular matrix (ECM) protein, plays a critical role in regulating the growth and differentiation of mesodermal tissues, including bone. Ln-5 can be secreted by the mesenchymal stem cells (MSCs), and Ln-5 promotes MSCs osteogenic differentiation. It has been demonstrated that a substrate's surface topography could regulate MSC secretion and differentiation.

Mechanical characterization of electrospun polyesteretherurethane (PEEU) meshes by atomic force microscopy.

The mechanical properties of electrospun fiber meshes typically are measured by tensile testing at the macro-scale without precisely addressing the spatial scale of living cells and their submicron architecture. Atomic force microscopy (AFM) enables the examination of the nano- and micro-mechanical properties of the fibers with potential to correlate the structural mechanical properties across length scales with composition and functional behavior. In this study, a polyesteretherurethane (PEEU) polymer containing poly(p-dioxanone) (PPDO) and poly(ɛ-caprolactone) (PCL) segments was electrospun into fiber meshes or suspended single fibers.

Bioperspectives for Shape-Memory Polymers as Shape Programmable, Active Materials.

Within the natural world, organisms use information stored in their material structure to generate a physical response to a wide variety of environmental changes. The ability to program synthetic materials to intrinsically respond to environmental changes in a similar manner has the potential to revolutionize material science. By designing polymeric devices capable of responsively changing shape or behavior based on information encoded into their structure, we can create functional physical behavior, including a shape-memory and an actuation capability.

Effect of iodinated contrast media on the oxygen tension in the renal cortico-medullary region of pigs.

Repeated injections of iodinated contrast media (CM) can lead to a deterioration of the renal blood flow, can redistribute blood from the renal cortex to other parts of the kidney and can cause small decreases of the blood flow in cortical capillaries, a significant reduction in blood flow in peritubular capillaries and a significant reduction in blood flow in the vasa recta. Therefore, a study in pigs was designed, to show whether the repeated injection of CM boli, alone, can cause a reduction of oxygenation in the cortico-medullar renal tissue - the region with the highest oxygen demand in the kidney - of pigs.While the mean pO2-value had only decreased by 0.

Shape memory nanocomposite fibers for untethered high-energy microengines.

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.

Phagocytosis of spherical and ellipsoidal micronetwork colloids from crosslinked poly(ε-caprolactone).

The effect of non-spherical particle shapes on cellular uptake has been reported as a general design parameter to control cellular recognition of particulate drug carriers. Beside shape, also size and cell-particle ratio should mutually effect phagocytosis. Here, the capability to control cellular uptake of poly(ɛ-caprolactone) (PCL) based polymer micronetwork colloids (MNC), a carrier system that can be transferred to various shapes, is explored in vitro at test conditions allowing multiple cell-particle contacts.

Amides as Non-polymerizable Catalytic Adjuncts Enable the Ring-Opening Polymerization of Lactide With Ferrous Acetate Under Mild Conditions.

Sn-based catalysts are effective in the ring-opening polymerization (ROP) but are toxic. Fe(OAc) used as an alternative catalyst is suitable for the ROP of lactide only at higher temperatures (>170°C), associated with racemization. In the ROP of ester and amide group containing morpholinediones with Fe(OAc) to polydepsipeptides at 135°C, ester bonds were selectively opened.

Spontaneous and induced platelet aggregation in apparently healthy subjects in relation to age.

Thrombotic disorders remain the leading cause of mortality and morbidity, despite the fact that anti-platelet therapies and vascular implants are successfully used today. As life expectancy is increasing in western societies, the specific knowledge about processes leading to thrombosis in elderly is essential for an adequate therapeutic management of platelet dysfunction and for tailoring blood contacting implants. This study addresses the limited available data on platelet function in apparently healthy subjects in relation to age, particularly in view of subjects of old age (80-98 years).

Collagen Peptide Upregulates Osteoblastogenesis from Bone Marrow Mesenchymal Stem Cells through MAPK- Runx2.

Collagen is the most abundant extracellular fibrous protein that has been widely used for biomedical applications due to its excellent biochemical and biocompatibility features. It is believed that the smaller molecular weight collagen, i.e.

Dedifferentiation of mature adipocytes with periodic exposure to cold.

 Lipid-containing adipocytes can dedifferentiate into fibroblast-like cells under appropriate culture conditions, which are known as dedifferentiated fat (DFAT) cells. However, the relative low dedifferentiation efficiency with the established protocols limit their widespread applications. In this study, we found that adipocyte dedifferentiation could be promoted via periodic exposure to cold (10°C) in vitro.

Molecular Insights into the Physical Adsorption of Amphiphilic Protein PhaF onto Copolyester Surfaces.

Phasins are amphiphilic proteins located at the polymer-cytoplasm interface of bacterial polyhydroxyalkanoates (PHA). The immobilization of phasins on biomaterial surfaces is a promising way to enhance the hydrophilicity and supply cell-directing elements in bioinstructing processes. Optimizing the physical adsorption of phasins requires deep insights into molecular processes during polymer-protein interactions to preserve their structural conformation while optimizing surface coverage.

Extractable Free Polymer Chains Enhance Actuation Performance of Crystallizable Poly(ε-caprolactone) Networks and Enable Self-Healing.

Crosslinking of thermoplastics is a versatile method to create crystallizable polymer networks, which are of high interest for shape-memory actuators. Here, crosslinked poly(ε-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.

Effect of lipopolysaccharide on the adherence of human umbilical vein endothelial cells (HUVEC) on a natural substrate.

 Polymers are often contaminated with lipopolysaccharides also known as endotoxins. Even small amounts of endotoxins can have strong effects on endothelial cell function so that the endothelialisation of cardiovascular implants might be hampered. An open question is how endothelial cells seeded on a body foreign substrate respond to shear load after adding Lipid A (LPA), the domain, which is responsible for much of the toxicity of gram-negative bacteria, and whether morphological changes of endothelial cells occur.

Oligodepsipeptide (nano)carriers: Computational design and analysis of enhanced drug loading.

High drug loads of nanoparticles are essential to efficiently provide a desired dosage in the required timeframe, however, these conditions may not be reached with so far established degradable matrices. Our conceptual approach for increasing the drug load is based on strengthening the affinity between drug and matrix in combination with stabilizing drug-matrix-hybrids through strong intermolecular matrix interactions. Here, a method for designing such complex drug-matrix hybrids is introduced employing computational methods (molecular dynamics and docking) as well as experimental studies (affinity, drug loading and distribution, drug release from films and nanoparticles).