Physical Properties and Erosion Behavior of Poly(trimethylene carbonate‐co‐ε‐caprolactone) Networks

Form‐stable resorbable networks are prepared by gamma irradiating trimethylene carbonate (TMC)‐ and ε‐caprolactone (CL)‐based (co)polymer films. To evaluate their suitability for biomedical applications, their physical properties and erosion behavior are investigated. Homopolymer and copolymer networks that are amorphous at room temperature are flexible and rubbery with elastic moduli ranging from 1.8 ± 0.3 to 5.2 ± 0.4 MPa and permanent set values as low as 0.9% strain. The elastic moduli of the semicrystalline networks are higher and range from 61 ± 3 to 484 ± 34 MPa. The erosion behavior of (co)polymer networks is investigated in vitro using macrophage cultures, and in vivo by subcutaneous implantation in rats. In macrophage cultures, as well as upon implantation, a surface erosion process is observed for the amorphous (co)polymer networks, while an abrupt decrease in the rate and a change in the nature of the erosion process are observed with increasing crystallinity. These resorbable and form‐stable networks with tuneable properties may find application in a broad range of biomedical applications.

     

Synthesis Of 5-tert-Butyl Benzo[b]thiophene-2-carboxylic Acid

The title compound was prepared from 4-tert-butyl cyclohexanone in high yield by a simple three step procedure.     

Reactive intermediates in the reaction of hydrazinecarbothioamides with 2-(bis(methylthio)methylene)malononitrile and ethyl 2-cyano-3,3-bis(methylthio)acrylate

Research on Chemical Intermediates - The reaction of N-substituted hydrazinecarbothioamides with both 2-(bis(methylthio)methylene)malononitrile and ethyl 2-cyano-3,3-bis(methylthio)acrylate...     

Purified oxygen- and nitrogen-modified multi-walled carbon nanotubes as metal-free catalysts for selective olefin hydrogenation

Oxygen- and nitrogen-functionalized carbon nanotubes (OCNTs and NCNTs) were applied as metal-free catalysts in selective olefin hydrogenation. A series of NCNTs was synthesized by NH₃ post-treatment of OCNTs. Temperature-programmed desorption, N₂ physisorption, Raman spectroscopy, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy were employed to characterize the surface properties of OCNTs and NCNTs, aiming at a detailed analysis of the type and amount of oxygen- and nitrogen-containing groups as well as surface defects. The gas-phase treatments applied for oxygen and nitrogen functionalization at elevated temperatures up to 600 °C led to the increase of surface defects, but did not cause structural damages in the bulk. NCNTs showed a clearly higher activity than the pristine CNTs and OCNTs in the hydrogenation of 1,5-cyclooctadiene, and also the selectivity to cyclooctene was higher. The favorable catalytic properties are ascribed to the nitrogen-containing surface functional groups as well as surface defects related to nitrogen species. In contrast, oxygen-containing surface groups and the surface defects caused by oxygen species did not show clear contribution to the hydrogenation catalysis.     

Simultaneous measurement of glucose and glutamine in aqueous solutions by near infrared spectroscopy

A method is described for measuring the concentrations of both glucose and glutamine in binary mixtures from near infrared (NIR) absorption spectra. Spectra are collected over the range from 5000–4000/cm (2.0–2.5μm) with a 1-mm optical path length. Glucose absorbance features at 4710, 4400, and 4300/cm and glutamine features at 4700, 4580, and 4390/cm provide the analytical information required for the measurement. Multivariate calibration models are generated by using partial least squares (PLS) regression alone and PLS regression combined with a preprocessing digital Fourier filtering step. The ideal number of PLS factors and spectral range are identified separately for each analyte. In addition, the optimum Fourier filter parameters are established for both compounds. The best overall analytical performance is obtained by combining Fourier filtering and PLS regression. Glucose measurements are established over the concentration range from 1.66–59.91 mM, with a standard error of prediction (SEP) of 0.32 mM and a mean percent error of 1.84%. Glutamine can be measured over the concentration range from 1.10–30.65 mM with a SEP of 0.75 mM and a mean percent error of 6.67%. These results demonstrate the analytical utility of NIR spectroscopy for monitoring glucose and glutamine levels in mammalian and insect cell cultures.     

Ellipsometry studies of fibronectin adsorption

The adsorption of fibronectin on a series of different surfaces was investigated with in situ ellipsometry. For silica and methylated silica, the adsorbed amount (Γ), the adsorbed layer thickness (δ_el) and the mean adsorbed layer refractive index (n_f) were obtained by a procedure involving studies of the bare substrate at two different ambient refractive indices, as well as four-zone averaging. It was found that the adsorbed amount of fibronectin was the same (1.9 ± 0.1 mg m⁻²) on both silica and methylated silica surfaces. However, the adsorbed layers formed on methylated silica were more extended and had a lower average protein concentration than those formed on silica. Furthermore, on both silica and methylated silica, an increasing adsorbed amount is achieved both by a denser packing of the fibronectin molecules and by a growth of the adsorbed layer normal to the surface. Furthermore, the adsorption of fibronectin on lipid surfaces was investigated. It was found that the adsorption of fibronectin on phosphatidic acid was quite significant (2.2 ± 0.2 mg m⁻²), while that on phosphatidylcholine, phosphatidylinositol and phosphatidylserine was much smaller (all 0.1 ± 0.05 mg m⁻²). These results are correlated to findings on the adsorption of fibrinogen on these surfaces, as well as on the opsonization of lipid-stabilized colloidal particles.