Kidney Podocytes as Specific Targets for cyclo(RGDfC)‐Modified Nanoparticles

Renal nanoparticle passage opens the door for targeting new cells like podocytes, which constitute the exterior part of the renal filter. When cyclo(RGDfC)‐modified Qdots are tested on isolated primary podocytes for selective binding to the αvβ3 integrin receptor a highly cell‐ and receptor‐specific binding can be observed. In displacement experiments with free cyclo(RGDfC) IC₅₀ values of 150 nM for αvβ3 integrin over‐expressing U87‐MG cells and 60 nM for podocytes are measured. Confocal microscopy shows a cellular Qdot uptake into vesicle‐like structures. Our ex vivo study gives clear evidence that, after renal filtration, nanoparticles can be targeted to podocyte integrin receptors in the future. This could be a highly promising approach for future therapy and diagnostics of podocyte‐associated diseases.     

Advanced characterization technique for mechanochemically synthesized materials: neutron total scattering analysis

Materials that adopt the pyrochlore (A₂B₂O₇) structure show promise for use in a variety of energy-related applications such as immobilization of actinide-rich nuclear waste and oxide fuel cells. Mechanochemical synthesis, a combination of milling and high-temperature treatment, has been successfully applied to fabricate many different pyrochlore compositions. High-resolution neutron total scattering experiments were used to gain fundamental insight into the structural details of milled Er₂Ti₂O₇ pyrochlore and the subsequent evolution under high-temperature treatment. The milling process creates a highly disordered structure in which local atomic ordering is present that is significantly different than the observed long-range behavior. Thermal annealing leads to a complex defect recovery scheme with a gradual local rearrangement from a weberite-type atomic ordering to a pyrochlore phase independent of the sharp long-range crystallization process. Annealing of the milled sample up to 1200 °C does not reproduce the local structure of the same pyrochlore sample prepared by solid-state synthesis. This indicates that despite both samples possessing identical long-range structures, local defects induced by the milling process persist to very high temperatures. These findings provide a direct insight into the mechanochemical synthesis of pyrochlore oxides and help to better elucidate the structural properties of highly disordered complex oxides under extreme conditions from the local atomic arrangement to the macroscale.     

Fabrication of discontinuous surface patterns within microfluidic channels using photodefinable vapor-based polymer coatings

In this report, we introduce a surface modification method for the fabrication of discontinuous surface patterns within microfluidic systems. The method is based on chemical vapor deposition (CVD) of a photodefinable coating, poly(4-benzoyl-p-xylylene-co-p-xylylene), onto the luminal surface of a microfluidic device followed by a photopatterning step to initiate spatially controlled surface binding. During photopatterning, light-reactive groups of the CVD polymer spontaneously react with molecules adjunct to the surface, such as poly(ethylene oxide). We demonstrate the potential of these reactive polymers for surface modification by preventing nonspecific protein adsorption on different substrates including silicon and poly(dimethylsiloxane) as measured by fluorescence microscopy. More importantly, three-dimensional patterns have successfully been created within polymer-based microfluidic channels, establishing spatially controlled, bioinert surfaces. The herein reported surface modification method addresses a critical challenge with respect to surface engineering of microfluidic devices, namely, the fabrication of discontinuous patterns within microchannels.     

Environmentally responsive core/shell particles via electrohydrodynamic co-jetting of fully miscible polymer solutions

Herein it is demonstrated that electrohydrodynamic co-jetting is not limited to Janus-type particles, but can also be used for the preparation of core/shell particles. Using side-by-side flow of miscible polymer solutions, electrohydrodynamic co-jetting offers an elegant and scalable route towards preparation of core/shell particles with otherwise difficult-to-prepare particle architectures, including particles with hydrophilic shell and core. Throughout this study, electrohydrodynamic co-jetting of aqueous solutions consisting of a mixture of PAAm-co-AA and PAA is used, and a range of different types of particles with distinct compartments are observed. Transition from Janus particles to core/shell particles appears to be caused by changes in the relative conductivity of the two jetting solutions. After crosslinking, the core/shell particles are stable in aqueous solution and exhibit reproducible swelling behavior while maintaining the original core/shell geometry. In addition, the pH-responsiveness of the particles is demonstrated by repeatedly switching the environmental pH between 1.3 and 12. Moreover, the core/shell particles show surprising uptake selectivity. For instance, a 450% increase in uptake of 6-carboxyfluorescein over rhodamine B base is found.     

Hydrogel-based piezoresistive pH sensors: investigations using FT-IR attenuated total reflection spectroscopic imaging

The strong swelling ability of the pH-responsive poly(acrylic acid)/poly(vinyl alcohol) (PAA/PVA) hydrogel makes the development of a new type of sensor possible, which combines piezoresistive-responsive elements as mechanoelectrical transducers and the phase transition behavior of hydrogels as a chemomechanical transducer. The sensor consists of a pH-responsive PAA/PVA hydrogel and a standard pressure sensor chip. However, a time-dependent sensor output voltage mirrors only the physical swelling process of the hydrogel but not the corresponding chemical reactions. Therefore, an investigation of the swelling behavior of this hydrogel is essential for the optimization of sensor design. In this work, Fourier transform infrared (FT-IR) spectroscopic imaging was used to study the swelling of the hydrogel under in situ conditions. In particular, laterally and time-resolved FT-IR images were obtained in the attenuated total reflection mode and the entire data set of more than 80,000 FT-IR spectra was evaluated by principal component analysis (PCA). The first and third principal components (PCs) indicate the swelling process. Molecular changes within the carboxyl groups were observed in the second and fourth PC and identified as key processes for the swelling behavior. It was found that time-dependent molecular changes are similar to the electrical sensor output signal. The results of the FT-IR spectroscopic images render an improved chemical sensor possible and demonstrate that in situ FT-IR imaging is a powerful method for the characterization of molecular processes within chemical-sensitive materials.     

Linear and non-linear dynamic response of sandwich panels to blast loading

The problem of the dynamic response of sandwich flat panels exposed to blast loadings is addressed. The sandwich model includes a number of non-classical effects such as the anisotropy and heterogeneity of face sheets, transverse orthotropy of the core layer, the geometrical non-linearities considered in the von Kármán sense, as well as the initial geometric imperfections. As concerns the blast pulses considered in this analysis, these are due to either an underwater/in-air explosion, or are due to a pressure wave traveling across the panel span. Implications of the explosive charge, stand-off distance, directionality property of face sheets material, damping ratio, geometric non-linearity, initial geometric imperfection, and of the characteristics of the blast, on dynamic response and dynamic magnification factor are put into evidence via a parametric study, and pertinent conclusions are outlined.     

SiGe channels for VT control of high-k metal gate transistors for 32 nm complementary metal oxide semiconductor technology and beyond

GLOBALFOUNDRIES 32 nm high-k metal gate technology, with SiGe channel for V_T control of P-field effect transistor, is taken into production. This epitaxial channel material is being introduced into high volume manufacturing in complementary metal oxide semiconductor technology. The morphology of the SiGe channel (cSiGe) for narrow width transistors is carefully controlled by process conditions such as epitaxial growth temperature, pre bake condition or in-situ Si recess prior epitaxial deposition. A micro loading effect observed in 28 nm technology was eliminated by an in-situ recess of the silicon before epitaxial deposition. Due to the significant cost of this process step, an epitaxial batch system has been evaluated to reduce the cost of ownership dramatically. Also the cSiGe process has been optimized to minimize the thickness variation of the SiGe channel due to the strong response of V_T to cSiGe thickness.