Poly(2‐(dimethylamino)ethyl methacrylate) Brushes with Incorporated Nanoparticles as a SERS Active Sensing Layer

A simple, fast, and versatile approach to the fabrication of outstanding surface enhanced Raman spectroscopy (SERS) substrates by exploiting the optical properties of the Ag nanoparticles and functional as well as organizational characteristics of the polymer brushes is reported. First, poly(2‐(dimethylamino)ethyl methacrylate) brushes are synthesized directly on glassy carbon by self‐initiated photografting and photopolymerization and thoroughly characterized in terms of their thickness, wettability, morphology, and chemical structure by means of ellipsometry, contact angle, AFM, and XPS, respectively. Second, Ag nanoparticles are homogeneously immobilized into the brush layer, resulting in a sensor platform for the detection of organic molecules by SERS. The surface enhancement factor (SEF) as determined by the detection of Rhodamine 6G is calculated as 6 × 10⁶.     

Dimerization determines substrate specificity of a bacterial prenyltransferase

We have identified the native dimer interface of heptaprenylglyceryl phosphate synthase PcrB from the bacterium Bacillus subtilis and analyzed the significance of oligomer formation for stability and catalytic activity. Computational methods predicted two different surface regions of the PcrB protomer that could be responsible for dimer formation. These bona fide interfaces were assessed both in silico and experimentally by the introduction of amino acid substitutions that led to monomerization, and by incorporation of an unnatural amino acid to allow cross-linking of the two protomers. The results showed that, in contrast to previous assumptions, PcrB uses the same interface for dimerization as the homologous geranylgeranylglyceryl phosphate synthase from Archaea. Thermal unfolding demonstrated that the monomeric proteins are only slightly less stable than wild-type PcrB. However, activity assays showed that monomerization limits the length of accepted polyprenyl pyrophosphates to three isoprene units, whereas the native PcrB substrate contains seven isoprene entities. We provide a plausible hypothesis as to how dimerization determines substrate specificity of PcrB.     

Antimicrobial Potential of Copper‐Containing Titanium Surfaces Generated by Ion Implantation and Dual High Power Impulse Magnetron Sputtering

The application of antimicrobial surfaces to titanium alloy (Ti) implants would be beneficial to prevent implant‐associated infections of joint endoprostheses and osteosyntheses. Copper (Cu) could be advantageously applied for this purpose, since it exhibits a well‐known antimicrobial activity and is a trace element in the human body, i.e., it is non‐toxic in small concentrations. This approach was evaluated with two plasma‐based surface modification procedures:

• 1) Implantation of Cu ions into Ti by means of plasma immersion ion implantation (PIII) and
• 2) Coating of Ti surfaces with Cu? Ti films by means of dual high power impulse magnetron sputtering (dual HiPIMS).

In this manner, the surfaces could be equipped with various amounts of Cu, as it was analyzed by X‐ray photoelectron spectroscopy (XPS). The surfaces released up to 8 mmol · L^?1 of Cu within 24 h, measured with atomic absorption spectroscopy (AAS). Hence, the surfaces possessed an antimicrobial potential against typical infect‐associated bacteria (Staphylococcus aureus). Surfaces with a higher Cu release prepared by HiPIMS technique revealed a higher antimicrobial effect, while surfaces implanted by PIII were less cytotoxic to osteoblasts (MG‐63 cells). These results show that Cu doped and coated implants could be useful for prevention and therapy of implant‐associated infections.     

Initial Attatchment of rMSC and MG‐63 Cells on Patterned Bioglass® Substrates

A soft lithography technique was used to introduce surface patterns on the surface of sintered bioactive glass substrates. Osteoblast‐like MG‐63 cells and rat mesenchymal stem cells (rMSC) seeded on micropatterned bioactive glass surfaces showed different behavior with rMSC exhibiting a better initial attachment than MG‐63 cells. Both cytoskeleton formation and cell spreading of rMSC were supported by the bioactive surfaces. In addition, the structured surfaces seemed to guide MG‐63 cells to a larger extent than rMSC. The in vitro results are important considering the continuous development of bone tissue scaffolds based on silicate bioactive glasses.     

Reliable fabrication of 3 nm gaps between nanoelectrodes by electron-beam lithography

The reliable fabrication of nanoelectrode pairs with predefined separations in the few nanometer range is an essential prerequisite for future nanoelectronic devices. Here we demonstrate a fine-tuned electron-beam lithographic (EBL) fabrication route which is suitable for defining nanoelectrode pairs with a gap size down to 3 ± 1 nm and with a yield of 55%. This achievement is based on an optimized two-layer resist system in combination with an adopted developer system, as well as on an elaborated nanoelectrode pattern design taking into consideration the EBL inherent proximity effect. Thus, even a structural control in the nanometer scale is achieved in the EBL process.     

Handling of particulate solids on the International Space Station

We present the principles of a particle-handling system for the International Space Station (ISS) with which experiments with astrophysical and planetological applications will be performed. The principle of dust deagglomeration and dispersion was successfully tested in short-duration microgravity experiments. The flight of the systems on the ISS is planned for 2012.     

Recognizing Simple Subextensions of Purely Transcendental Field Extensions

Let k(X)/k be a finitely generated purely transcendental extension of fields with transcendence basis X. From a generalization of Lüroth's theorem it is known that all intermediate fields K of k(X)/k with (K/k) = 1 are of the form K = k(f) for some f∈k(X). In this note we give a criterion which allows to decide effectively whether the extension K/k is simple if a finite generating set of K over k is known and computations in K are effective. In the affirmative case a primitive element of K over k is computed. Received: August 13, 1999; revised version: February 4, 2000     

Water-dispersible PVA-based dry microballoons with potential for biomedical applications

This paper reports on the preparation and characterization of stable poly(vinyl alcohol) (PVA)-based dry hollow microparticles, readily convertible to gas-filled microballoons (MBs) in water suspension. The rehydrated MBs can be used as ultrasound contrast agents and for targeted drug delivery, while the dry MBs are suitable for encapsulation of biologically active gases. The MBs powder material is obtained by freeze-drying the as-prepared telechelic PVA-shelled MBs aqueous dispersion. The microstructure of the lyophilized MBs as well as of the starting and the reconstituted MBs in water suspension was examined using transmission electron microscopy (TEM), scanning electron microscopy (SEM), scanning transmission X-ray microspectroscopy (STXM) and confocal laser scanning microscopy (CLSM). STXM observations below and above the oxygen K-edge reveal that 80% of the MBs originating from the lyophilized particles are gas-filled. Moreover, local carbon K near-edge X-ray absorption fine structure spectroscopy (NEXAFS) measurements evidenced that the chemical composition of the polymeric shell is preserved during the freeze-drying process and subsequent shelf storage for at least more than one year.