Functionalized Cellulose Based Microcomposites

Summary: A technique has been developed that allows the production of cellulosic micro composites by immobilizing super-ground functionalised materials in the cellulose matrix. For this purpose, the well-established ALCERU® process has been a subject of technological modification. Depending on the degree of filling, several types of composites are accessible. At lower concentrations, the fibres maintain their textile-physical parameters and may be used in applications, where a textile appearance is required. The increasing concentration of the functional additives influences increasingly the overall properties of the composite and leads to composites with special functions such as water retention, electric conductivity, and specific absorption ability for organics or heat storage functions. In addition, loads exceeding the cellulose portion are useful as green shapes for ceramics.     

Cyclo­decyl 4‐nitro­phenyl­acetate

Cyclodecyl 4‐nitrophenylacetate, C₁₈H₂₅NO₄, has its ten‐membered ring in the expected diamond‐lattice boat–chair–boat [2323] conformation, with the substituent 4‐nitro­phenyl­acet­oxy group in the BCB IIIe position. The ester unit has the expected Z conformation, with an O=C—O—C torsion angle of −0.3 (3)°, and the connection to the benzene ring is nearly perpendicular to the ester, with an O=C—C—C torsion angle of 85.5 (2)°. An inter­molecular contact exists between the ester C atom and a nitro O atom, having a C⋯O distance of 2.909 (2) Å.     

Ultrasonic synthesis of stable, functional lysozyme microbubbles

High-intensity ultrasound induces emulsification and cross-linking of protein molecules in aqueous medium. The stability and the functionality of the resultant protein-coated microbubbles are crucial in many of their applications. For example, the stability of drug-loaded microbubbles should be sufficiently long enough, in vivo, so that they can be ruptured only at specific sites for release of the drugs. In this study, we report the synthesis of stable and functional microbubbles, coated with chemically reduced lysozyme, using high-intensity ultrasound in aqueous solution. In the absence of chemical reduction, stable microbubbles were not produced with native lysozyme, indicating the importance of free -SH functional groups for protein cross-linking. The degree of cross-linking between lysozyme molecules was controlled by manipulating both the extent of chemical reduction of the intramolecular disulfide bonds and sonication time. The lysozyme-coated microbubbles are stable for several months and retain the enzymatic (antimicrobial) activity of lysozyme. The layer-by-layer (LbL) deposition of polyelectrolytes onto the protein-shell air-core template has been used as a versatile procedure to modify the surface properties of the microbubbles, indicating the possibility of adsorbing potential drugs and/or biolabels on the surface of these microbubbles for therapeutic and diagnostic applications.     

Rheological behavior of self-assembling PEG-beta-cyclodextrin/PEG-cholesterol hydrogels

The rheological properties of a recently developed self-assembling hydrogel system composed of beta-cyclodextrin (betaCD)- and cholesterol-derivatized 8-arm star-shaped poly(ethylene glycol) (PEG8) were investigated. To understand and predict the gel rheological properties, data fitting with the Maxwell model as well as comparing the system's concentration-dependent behavior with Cates' model for reversibly breaking chains were performed. To investigate the influence of the polymer architecture, networks were also prepared by replacing the cholesterol-derivatized 8-arm star-shaped PEG by linear bifunctional PEG-cholesterol or by using 4-arm instead of 8-arm polymers. Rheological analysis showed that the 8-arm polymer-based mixtures yielded tight viscoelastic networks, but their storage and loss moduli significantly deviated from those predicted by the Maxwell model. The scaling of the plateau moduli, relaxation times, and zero-shear viscosities with concentration for gels composed of 8-arm cholesterol- and betaCD-derivatized PEG followed a power law with exponents higher than predicted by Cates' model. On the other hand, hydrogels in which linear bifunctional PEG-cholesterol was used instead of 8-arm star-shaped PEG-cholesterol or which were based on 4-arm polymers showed a substantially better fit with the Maxwell model and reduced differences between empirical and Cates' theoretical scaling exponents. Rheological analysis also showed that the hydrogels were thermoreversible. At low temperatures, the gels showed viscoelastic behavior due to slow overall relaxation of the polymer chains. At higher temperatures, however, a reduced number of betaCD/cholesterol complexes and concomitant faster chain relaxation processes eventually led to liquid-like behavior. The relationship between temperature and the relaxation time was used to determine an activation energy of 46 kJ/mol for breaking and reptation of the polymers.     

Creating a fatty acid methyl ester database for lipid profiling in a single drop of human blood using high resolution capillary gas chromatography and mass spectrometry

Capillary gas chromatography (CGC) in combination with mass spectrometry (MS) was optimized for the separation and detection of the fatty acids occurring in the lipid fraction of blood. A fingertip blood sample (ca. 50 microL) was transesterified into the methyl esters and analyzed on a 100 m x 0.25 mm ID column coated with a biscyanopropyl polysiloxane (HP-88) stationary phase. The method was retention time locked. Programmed temperature vaporization injection (PTV) in the solvent venting mode was applied to minimize the sample size, while maintaining high sensitivity. The total analysis time was ca. 60 min. Retention times and both electron impact (EI) and positive chemical ionization (PCI) mass spectrometry were combined to elucidate the fatty acids according to alkyl chain, degree of unsaturation and position of the double bonds. Using extracted ion chromatograms about 100 fatty acids and related compounds were detected in blood samples and most of them were identified. This work resulted in a very large fatty acid methyl esters database, containing retention time and mass spectral information that will be applied to metabolomic studies.     

"Fatal adsorption" of brushlike macromolecules: high sensitivity of C-C bond cleavage rates to substrate surface energy

Adsorption-induced degradation of brushlike macromolecules was monitored through molecular imaging by atomic force microscopy. The rate constant for C-C bond cleavage was shown to be extremely sensitive to the substrate surface energy. A few percent increase in the surface energy from 69.2 to 71.2 mN/m led to an order of magnitude increase of the scission rate. The absolute values of the rupture forces ranging from 2.57 to 2.47 nN are in agreement with previously calculated and measured values for stretching surface-tethered molecules.