Copper (Cu) is a cofactor of various metalloenzymes and has a role in neurodegenerative diseases with disturbed Cu homeostasis, for example, in Alzheimer's disease (AD) and Menkes disease. To address Cu imbalances, we synthesized two different dendritic nanoparticles (NP) for the transport of Cu(II) ions across the blood-brain barrier (BBB). The synthesized NPs show low toxicity and high water solubility and can stabilize high amounts of Cu(II). The Cu(II)-laden NPs crossed cellular membranes and increased the cellular Cu level. A human brain microvascular endothelial cell (HBMEC) model was established to investigate the permeability of the NPs through the BBB. By comparing the permeability × surface area product (PSe) of reference substances with those of NPs, we observed that NPs crossed the BBB model two times more effectively than (14)C-sucrose and sodium fluorescein (NaFl) and up to 60× better than Evans Blue labeled albumin (EBA). Our results clearly indicate that NPs cross the BBB model effectively. Furthermore, Cu was shielded by the NPs, which decreased the Cu toxicity. The novel design of the core-shell NP enabled the complexation of Cu(II) in the outer shell and therefore facilitated the pH-dependent release of Cu in contrast to core-multishell NPs, where the Cu(II) ions are encapsulated in the core. This allows a release of Cu into the cytoplasm. In addition, by using a cellular detection system based on a metal response element with green fluorescent protein (MRE-GFP), we demonstrated that Cu could also be released intracellularly from NPs and is accessible for biological processes. Our results indicate that NPs are potential candidates to rebalance metal-ion homeostasis in disease conditions affecting brain and neuronal systems.

In this paper we present the asymmetric hydrogenation of a-keto esters with platinum nanoparticles homogeneously stabilized in dendritic coremultishell architectures. The main focus lies on recycling and metal leaching, because little is reported so far about these aspects. It is shown that the stabilizing polymer allows for the efficient modification of the Pt surface with the chiral alkaloid cinchonidine, thereby inducing enantioselectivity and enhancing the reaction rate in the asymmetric hydrogenation of ethyl pyruvate. After optimization of the reaction conditions 63% ee for (R)-ethyl lactate was obtained. During recycling it was found that this value could even be increased upon ultrafiltration of the catalyst prior to use. Recycling was accomplished for 10 cycles with stable activity and enantioselectivity (~73% ee) in the first eight runs. Aggregation of the initially well dispersed nanoparticles was observed by transmission electron microscope (TEM) analysis, leading to reduced conversion after the 8 th cycle, but metal leaching into the product has been observed only in the very first run.

Cores célèbre: The synthesis of metal nanoparticle‐loaded mesoporous silica and their application to enantioselective reactions are described. Dendritic core–multishell polymers are used as stabilizers for Pt nanoparticles and as templates for the synthesis of mesoporous silica. The catalysts can be recycled for at least nine cycles with high enantiomeric excesses and full conversion in the reduction of ethyl pyruvate.

Core-shell and core-multishell nanocarriers were designed to transport copper ions into cells. Herein, we present their synthesis and physicochemical characterization and demonstrate the high influence of their architectures on the loading and release of copper. Their low toxicity may open a new way to balance the Cu-homeostasis in neurodegenerative diseases.

Core–multishell architectures are a new approach to homogeneously stabilize metal nanoparticles for harsh conditions. Herein, we present the synthesis and stabilization of Pt nanoparticles in dendritic core–multishell polymers and their application in hydrogenation reactions. The successful recycling of the catalyst was demonstrated for the hydrogenation of methyl crotonate 1 and was either achieved by ultrafiltration or in a two‐phase system for at least 14 cycles. Thereby, the total turnover number (TON) was increased to 22 000. In the recycling experiments, low metal leaching into the product (as low as 0.3 ppm) was detected. Additionally, the selective hydrogenation of isophorone 3 was investigated and selectivities of 99:1 for CC versus CO hydrogenation were achieved.