Phytochrome‐Based Extracellular Matrix with Reversibly Tunable Mechanical Properties

Interrogation and control of cellular fate and function using optogenetics is providing revolutionary insights into biology. Optogenetic control of cells is achieved by coupling genetically encoded photoreceptors to cellular effectors and enables unprecedented spatiotemporal control of signaling processes. Here, a fast and reversibly switchable photoreceptor is used to tune the mechanical properties of polymer materials in a fully reversible, wavelength‐specific, and dose‐ and space‐controlled manner. By integrating engineered cyanobacterial phytochrome 1 into a poly(ethylene glycol) matrix, hydrogel materials responsive to light in the cell‐compatible red/far‐red spectrum are synthesized. These materials are applied to study in human mesenchymal stem cells how different mechanosignaling pathways respond to changing mechanical environments and to control the migration of primary immune cells in 3D. This optogenetics‐inspired matrix allows fundamental questions of how cells react to dynamic mechanical environments to be addressed. Further, remote control of such matrices can create new opportunities for tissue engineering or provide a basis for optically stimulated drug depots.     

Electrochemical investigations on amorphous Fe-base alloys for alkaline water electrolysis

In this work different amorphous melt-spun Fe-alloys (Fe₈₂B₁₈, Fe₈₀Si₁₀B₁₀, Fe₆₀Co₂₀Si₁₀B₁₀) were investigated as cathode materials for the alkaline electrolysis of water. In particular, the influence of cobalt as well as the metalloids boron and silicon on the activity for the hydrogen evolution reaction (HER) was studied in 1 M KOH at 298 K using cyclic voltammetric, galvanostatic and polarization techniques. The electrocatalytic activity was evaluated in the view of the overpotential. It was found that cyclic voltammetric techniques can be used to activate the melt-spun Fe-alloys strongly. Different cyclic voltammetric activation procedures are discussed and the influence of the sweep rate and the potential window on the HER activity was elucidated. The experimental data indicate that the addition of metalloids and, most importantly, of cobalt improves the HER activity of the materials. Thus, the overpotential can be reduced by 200 mV compared to polycrystalline Ni.     

Experimental and theoretical assessment of flexural properties of hybrid natural fibre composites

The concept of hybridization of natural fibre composites with synthetic fibres is attracting increasing scientific attention. The present study addresses the flexural properties of hybrid flax/glass/epoxy composites to demonstrate the potential benefits of hybridization. The study covers both experimental and theoretical assessments. Composite laminates with different hybrid fibre mixing ratios and different layer configurations were manufactured, and their volumetric composition and flexural properties were measured. The relationship between volume fractions in the composites is shown to be well predicted as a function of the hybrid fibre mixing ratio. The flexural modulus of the composites is theoretically assessed by using micromechanical models and laminate theory. The model predictions are compared with the experimentally determined flexural properties. Both approaches show that the flexural modulus of the composites is consistently increased when the flax fibre fabrics are replaced by glass fibre fabrics from the inner layers to the outer layers. The observed deviations between the experimental and theoretical values are explained by the simplifying model assumptions applied for the configuration of the composites, in particular the flax fibre composites. This needs to be addressed in further work.     

Costimulatory molecules in ocular cicatricial pemphigoid

PURPOSE: To examine normal and inflamed conjunctiva from patients with ocular cicatricial pemphigoid (OCP) for the presence of costimulatory molecule CD28 and its ligands B7-1 (CD80) and B7-2 (CD86). METHODS: Conjunctival biopsy specimens from 12 patients with OCP and from five healthy persons undergoing cataract surgery were analyzed by light microscopy and immunohistochemical examination with monoclonal antibody probes for CD28, B7-1, and B7-2 molecules and for mononuclear cell subtypes. RESULTS: Epithelium of OCP conjunctiva showed more Langerhans' cells, B7-1-positive (+) cells, and B7-2 expression (ratio of B7-2-positive cells to antigen-presenting cells). In the substantia propria, OCP specimens showed significantly increased numbers of T cells (CD3 +), macrophages (CD68+), CD28+ cells, B7-2+ cells (CD86+), Langerhans' cells (CD1a), and B7-1+ cells (CD80). Most of the B7-2+ cells, macrophages, and Langerhans' cells were located subepithelially. B7-2 expression was significantly higher in OCP conjunctival substantia propria compared with normal conjunctiva. CONCLUSIONS: The results of this study indicate that the expression of the costimulatory molecule B7-2 is upregulated in conjunctiva of patients with active OCP. This increased subepithelial B7-2 expression may contribute to the sustained immune activation in OCP conjunctiva.