Continuous production of inorganic magnetic nanocomposites for biomedical applications by laser pyrolysis

Magnetic composites of Fe-based nanoparticles encapsulated in carbon/silica (C/SiO₂@Fe) or carbon (C@Fe) matrices were prepared by laser-induced pyrolysis of aerosols. The powders were dispersed in aqueous solutions at pH 7 resulting in biocompatible colloidal dispersions with a high resistance to biodegradation. Structural and magnetic properties and the suitability of aqueous dispersions as contrast agent for MRI were analyzed. The results of these characterizations and the NMR relaxivity data are very encouraging for application of laser pyrolysis products in the field of living tissues.     

End‐functionalized polystyrene by ATRP: A facile approach to primary amino and carboxylic acid terminal groups

Monoamino‐terminated and monocarboxylic acid‐terminated polystyrenes containing active halogenated end groups were prepared by atom transfer radical polymerization (ATRP) using the so‐called initiator method and protective group chemistry. α‐Chloropropionates were synthesized and utilized as initiators containing the tert‐butoxycarbonyl (t‐BOC)‐protected amino and the tert‐butyl (t‐Bu)‐protected carboxylic acid function, respectively. Optimum polymerization conditions were attained using CuCl/N,N,N′,N′′,N′′‐pentamethyldiethylenetriamine (PMDETA) as catalyst and 10 vol % n‐butanol as homogenizing agent at 110 °C. However, targeting larger quantities an alternative route was established employing 50 vol % N,N‐dimethylformamide (DMF). Subsequent hydrolysis of the ω‐tert‐butoxycarbonyl polystyrenes afforded well‐defined polymers with quantitative deprotection of the functional groups. Comparatively, thermolytic cleavage of the protective sites was studied. ¹H NMR verified the quantitative removal of the t‐BOC‐protecting groups. Furthermore, the resulting α‐amino‐ω‐chloro polystyrenes were reacted with Sanger reagent to confirm the existence of the thereby converted primary amino groups. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3845–3859, 2009     

Einen Beitrag zur Kenntnis der Gummisorten des Handels, nebst einem Vergleich der Bestimmungsverfahren

Ohne Zusammenfassung     

SIMS Characterisation of Aluminum-Alloyed Hot Isostatic Pressed Steel

 Recently, interest in steel alloyed with∼1% Al increased. These materials are expected to show a higher resistance against oxidation at high temperatures which will improve their performance when used as high-speed-steels. Furthermore, efforts have been made to combine the advantages of Al-steels with those of powder-metallurgic methods like hotisostatic-pressing (hip). This should result in a better macro- and microscopic homogeneity of the distribution of all compounds, yielding less waste-production and a longer life-time of products. In order to gain deeper insights in the process of “hipping” of the considered material and to see the distribution of both main as well as trace components, 2D and 3D-SIMS measurements of the material were performed before and after having undergone the hip process. The measurements showed enrichments of Na, K, Mg, Ca, and S at the particle boundaries before as well as after the hip-process. In the hipped material, the enrichments are significantly stronger in the spatial domains in-between larger particles. They also reveal, that the concentration of C is not equal in all particles and that the particles are covered with an Al₂O₃-layer which is not dispersed by the hip-process. There were also found small (∼50–100 nm) nitride-precipitates before as well as after the hip-process.     

Grafting of copolymer styrene maleic anhydride on poly(ethylene terephthalate) film by chemical reaction and by plasma method: Optimization of the grafting reaction using experimental design

This work deals with the chemical grafting of a styrene maleic anhydride copolymer on the surface of a previously hydrolyzed polyethylene terephthalate (PET) film 12 μm thick via covalent bond. Two different ways are studied. The first one involves an activation of the hydrolyzed PET by the triethylamine before the grafting step. In the second one, the copolymer reacts with the 4-dimethylaminopyridine in order to form maleinyl pyridinium salt which reacts with alcohol function of the hydrolyzed PET. Characterization and quantification of the grafting are performed by Fourier transform infrared spectroscopy. Factorial experiment designs are used to optimize the process and to estimate experimental parameters effects. The opportunity to associate the chemical process to a cold remote nitrogen plasma one is also examined.     

Nanosized cancer cell-targeted polymeric immunomicelles loaded with superparamagnetic iron oxide nanoparticles

Stable 30–50 nm polymeric polyethylene glycol–phosphatidylethanolamine (PEG–PE)-based micelles entrapping superparamagnetic iron oxide nanoparticles (SPION) have been prepared. At similar concentrations of SPION, the SPION-micelles had significantly better magnetic resonance imaging (MRI) T2 relaxation signal compared to ‘plain’ SPION. Freeze-fracture electron microscopy confirmed SPION entrapment in the lipid core of the PEG–PE micelles. To enhance the targeting capability of these micelles, their surface was modified with the cancer cell-specific anti-nucleosome monoclonal antibody 2C5 (mAb 2C5). Such mAb 2C5-SPION immunomicelles demonstrated specific binding with cancer cells in vitro and were able to bring more SPION to the cancer cells thus demonstrating the potential to be used as targeted MRI contrast agents for tumor imaging.     

Period 2 regulates neural stem/progenitor cell proliferation in the adult hippocampus

Background  

Newborn granule neurons are generated from proliferating neural stem/progenitor cells and integrated into mature synaptic networks in the adult dentate gyrus of the hippocampus. Since light/dark variations of the mitotic index and DNA synthesis occur in many tissues, we wanted to unravel the role of the clock-controlled Period2 gene (mPer2) in timing cell cycle kinetics and neurogenesis in the adult DG.     

The influence of porosity on the elastoplastic behavior of high performance cast alloys

Based on geometrical data of porous components obtained by computer tomography, a micromechanical unit cell model is proposed to predict the influence of porosity on mechanical properties of high performance cast alloys. Simulations of uniaxial loaded periodic unit cells are compared to experimental data of tensile tests on porous materials. In this way a relationship between some significant geometrical data of the pores and the macroscopic material parameters is obtained. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)