Influence of stress on the degradation behavior of Mg LAE442 implant systems

In this paper the performance of a magnesium based implant system is analyzed. A special emphasis is placed on the impact of stress on the corrosion behavior of the magnesium alloy. An implant system containing a plate and 4 corresponding screws is machined from Mg LAE442. Its corrosion behavior is tested in-vivo in New Zealand White Rabbits for 6 and 12 weeks of implantation. The plate is monocortically fixated on the medial tibia. At the interface between screw and plate increased corrosion is observed. This phenomenon is stronger on the caudal side of the screw. Parallel to the in-vivo test the influence of stress load on the corrosion rate is analyzed for LAE442 in in-vitro tests. Compressive load is applied on cylindrical specimens in axial direction and the corrosion rate is measured in 0.9 wt% NaCl solution by eudiometry and mass loss. Additionally rectangular samples are bent to apply tensile stress on the surface. A drop of 5 wt% NaCl is deposited on the surface and the corrosion is evaluated by microscopic images. It is shown that stress essentially influences the corrosion rate. While tensile stress decreases the corrosion, compressive stress leads to higher corrosion rates

The polyphenol EGCG directly targets intracellular amyloid-β aggregates and promotes their lysosomal degradation

The accumulation of amyloidogenic protein aggregates in neurons is a pathogenic hallmark of a large number of neurodegenerative diseases including Alzheimer's disease (AD). Small molecules targeting such structures and promoting their degradation may have therapeutic potential for the treatment of AD. Here, we searched for natural chemical compounds that decrease the abundance of stable, proteotoxic β-sheet-rich amyloid-β (Aβ) aggregates in cells. We found that the polyphenol (-)-epigallocatechin gallate (EGCG) functions as a potent chemical aggregate degrader (CAD) in SH-EP cells. We further demonstrate that a novel, fluorescently labeled EGCG derivative (EGC-dihydroxybenzoate (DHB)-Rhodamine) also shows cellular activity. It directly targets intracellular Aβ42 aggregates and competes with EGCG for Aβ42 aggregate binding in vitro. Mechanistic investigations indicated a lysosomal accumulation of Aβ42 aggregates in SH-EP cells and showed that lysosomal cathepsin activity is critical for efficient EGCG-mediated aggregate clearance. In fact, EGCG treatment leads to an increased abundance of active cathepsin B isoforms and increased enzymatic activity in our SH-EP cell model. Our findings suggest that intracellular Aβ42 aggregates are cleared through the endo-lysosomal system. We show that EGCG directly targets intracellular Aβ42 aggregates and facilitates their lysosomal degradation. Small molecules, which bind to protein aggregates and increase their lysosomal degradation could have therapeutic potential for the treatment of amyloid diseases

Silicification of Peptide-Coated Silver Nanoparticles-A Biomimetic Soft Chemistry Approach toward Chiral Hybrid Core-Shell Materials

Silica and silver nanoparticles are relevant materials for new applications in optics, medicine, and analytical chemistry. We have previously reported the synthesis of pH responsive, peptide-templated, chiral silver nanoparticles. The current report shows that peptide-stabilized nanoparticles can easily be coated with a silica shell by exploiting the ability of the peptide coating to hydrolyze silica precursors such as TEOS or TMOS. The resulting silica layer protects the nanoparticles from chemical etching, allows their inclusion in other materials, and renders them biocompatible. Using electron and atomic force microscopy, we show that the silica shell thickness and the particle aggregation can be controlled simply by the reaction time. Small-angle X ray scattering confirms the Ag/peptide@silica core-shell structure. UV-vis and circular dichroism spectroscopy prove the conservation of the silver nanoparticle chirality upon silicification. Biological tests show that the biocompatibility in simple bacterial systems is significantly improved once a silica layer is deposited on the silver particles