Mammalian cell viability in electrospun composite nanofiber structures

Incorporation of mammalian cells into nanofibers (cell electrospinning) and multilayered cell-nanofiber structures (cell layering) via electrospinning are promising techniques for tissue engineering applications. We investigate the viability of 3T3-L1 mouse fibroblasts after incorporation into poly(vinyl alcohol) nanofibers and multilayering with poly(caprolactone) nanofibers and analyze the possible factors that affect cell viability. We observe that cells do not survive cell electrospinning but survive cell layering. Assessing the factors involved in cell electrospinning, we find that dehydration and fiber stretching are the main causes of cell death. In cell layering, the choice of solvent is critical, as residual solvent in the electrospun fibers could be detrimental to the cells.     

Growth of an oligopyridine adlayer on Ag(100)--a scanning tunnelling microscopy study

The growth behaviour of the oligopyridine derivative 2-phenyl-4,6-bis(6-(pyridine-2-yl)-4-(pyridine-4-yl)pyridine-2-yl)pyrimidine (2,4'-BTP) on Ag(100) in the sub-monolayer regime was investigated by variable temperature scanning tunneling microscopy under ultra-high vacuum conditions. Over the entire coverage range, the molecules are adsorbed in a flat lying configuration, with preferential orientations with respect to the <110> direction of the surface. The azimuth angles are derived using a previously introduced algorithm that fits the positions of the intramolecular N atoms geometrically to the underlying surface lattice ("points-to-lattice fit") [H.E. Hoster et al., Langmuir 2007, 23, 11570], indicating that the orientation of the admolecules and thus of the adllayer structure with respect to the Ag(100) surface lattice is determined by the 2,4'-BTP-Ag(100) interaction, while intermolecular interactions are decisive for the structure of the adlayer. The results will be compared to other adsorption systems.     

Electrochemically controlled self-assembled monolayers characterized with molecular and sub-molecular resolution

Self-assembled organization of functional molecules on solid surfaces has developed into a powerful and sophisticated tool for surface chemistry and nanotechnology. A number of reviews on the topic have been available since the mid 1990s. This perspective article aims to focus on recent development in the investigations of electronic structures and assembling dynamics of electrochemically controlled self-assembled monolayers (SAMs) of thiol containing molecules on gold surfaces. A brief introduction is first given and particularly illustrated by a Table summarizing the molecules studied, the surface lattice structures and the experimental operating conditions. This is followed by discussion of two major high-resolution experimental methods, scanning tunnelling microscopy (STM) and single-crystal electrochemistry. In Section 3, we briefly address choice of supporting electrolytes and substrate surfaces, and their effects on the SAM structures. Section 4 constitutes the major body of the article by offering some details of recent studies for the selected cases, including in situ monitoring of assembling dynamics, molecular electronic structures, and the key external factors determining the SAM packing. In Section 5, we give examples of what can be offered by theoretical computations for the detailed understanding of the SAM electronic structures revealed by STM images. A brief summary of the current applications of SAMs in wiring metalloproteins, design and fabrication of sensors, and single-molecule electronics is described in Section 6. In the final two sections (7 and 8), we discuss the current status in understanding of electronic structures and properties of SAMs in electrochemical environments and what could be expected for future perspectives.     

A molecular Mo4Bi4 framework composed exclusively of unsupported metal-metal bonds

Reaction of [Cp(2)MoH(2)] with bismuth allyloxide, [Bi{OCH(CH(3))CH==CH(2)}(3)], gave rise to an extended octanuclear complex wherein two cyclic Mo(2)Bi(2) units composed of four Mo-Bi bonds are linked by a Bi-Bi bond. The fact that the construction of such an assembly could be accomplished only in the case of a monomethylation of the parent allyl residue demonstrates a subtle substituent effect.     

Monolithic methacrylate packed 96-tips for high throughput bioanalysis

In the pharmaceutical industry the growing number of samples to be analyzed requires high throughput and fully automated analytical techniques. Commonly used sample-preparation methods are solid-phase extraction (SPE), liquid–liquid extraction (LLE) and protein precipitation. In this paper we will discus a new sample-preparation technique based on SPE for high throughput drug extraction developed and used by our group. This new sample-preparation method is based on monolithic methacrylate polymer as packing sorbent for 96-tip robotic device. Using this device a 96-well plate could be handled in 2–4 min. The key aspect of the monolithic phase is that monolithic material can offer both good binding capacity and low back-pressure properties compared to e.g. silica phases. The present paper presents the successful application of monolithic 96-tips and LC–MS/MS by the sample preparation of busulphan, rescovitine, metoprolol, pindolol and local anaesthetics from human plasma samples and cyklophosphamid from mice blood samples.     

Comparison of the internal energy deposition of direct analysis in real time and electrospray ionization time-of-flight mass spectrometry

The internal energy (E_int) distributions of a series of p-substituted benzylpyridinium ions generated by both direct analysis in real time (DART) and electrospray ionization (ESI) were compared using the “survival yield” method. DART mean E_int values at gas flow rates of 2, 4, and 6 L min⁻¹, and at set temperatures of 175, 250, and 325 °C were in the 1.92–2.21 eV range. ESI mean E_int at identical temperatures in aqueous and 50% methanol solutions ranged between 1.71 and 1.96 eV, and 1.53 and 1.63 eV, respectively. Although the results indicated that ESI is a “softer” ionization technique than DART, there was overlap between the two techniques for the particular time-of-flight mass spectrometer used. As a whole, there was an increase in E_int with increasing reactive and drying gas temperatures for DART and ESI, respectively, indicating thermal ion activation. Three dimensional computational fluid dynamic simulations in combination with direct temperature measurements within the DART ionization region revealed complex inversely coupled fluid-thermal phenomena affecting ion E_int values during atmospheric transport. Primarily, that DART gas temperature in the ionization region was appreciably less than the set gas temperature of DART due to the set gas flow rates. There was no evidence of E_int deposition pathways from metastable-stimulated desorption, but fragmentation induced by high-energy helium metastables was observed at the highest gas flow rates and temperatures.     

Natural product-guided discovery of a fungal chitinase inhibitor

Natural products are often large, synthetically intractable molecules, yet frequently offer surprising inroads into previously unexplored chemical space for enzyme inhibitors. Argifin is a cyclic pentapeptide that was originally isolated as a fungal natural product. It competitively inhibits family 18 chitinases by mimicking the chitooligosaccharide substrate of these enzymes. Interestingly, argifin is a nanomolar inhibitor of the bacterial-type subfamily of fungal chitinases that possess an extensive chitin-binding groove, but does not inhibit the much smaller, plant-type enzymes from the same family that are involved in fungal cell division and are thought to be potential drug targets. Here we show that a small, highly efficient, argifin-derived, nine-atom fragment is a micromolar inhibitor of the plant-type chitinase ChiA1 from the opportunistic pathogen Aspergillus fumigatus. Evaluation of the binding mode with the first crystal structure of an A. fumigatus plant-type chitinase reveals that the compound binds the catalytic machinery in the same manner as observed for argifin with the bacterial-type chitinases. The structure of the complex was used to guide synthesis of derivatives to explore a pocket near the catalytic machinery. This work provides synthetically tractable plant-type family 18 chitinase inhibitors from the repurposing of a natural product.     

A validated method for the quantification of curcumin in plasma and brain tissue by fast narrow-bore high-performance liquid chromatography with fluorescence detection

Curcumin, a lipophilic polyphenol derived from the rhizome of the plant turmeric (Curcuma longa), might be useful in the prevention and treatment of a number of degenerative brain disorders, including glioma multiforma and Alzheimer’s disease. Thus, there is growing interest in measuring curcumin concentrations in the brain and other target tissues in relevant animal models. We therefore developed and validated (according to the Food and Drug Administration guidelines for bioanalytical method validation), a simple, fast and reliable method for the quantification of curcumin in biological matrices by fast high-performance liquid chromatography with fluorescence detection. This method involves a simple extraction with 95% ethyl acetate and 5% methanol, rapid separation (<2 min if external standards and <4 min if the internal standard β-estradiol 17-acetate is used) on a Jasco Reprosil-Pur Basic C₁₈ column (75 × 2 mm, 1.8 μm) with an eluent of acetonitrile, methanol, de-ionised water and acetic acid (49:20:30:1, v/v; flow rate, 0.4 mL/min) and fluorescence detection (excitation wavelength, 420 nm; emission wavelength, 470 nm). The method is selective, precise (<15% RSD at the lower limit of quantification), accurate (<15% of the coefficient of variation at the lower limit of quantification) and sensitive over a linear range of 0.05–10 μg/mL for curcumin. The developed method was used for the quantification of curcumin in the brains of mice force-fed (50 mg/kg bw) or i.p. injected (100 mg/kg bw) with curcumin. Brain curcumin concentrations of the mice were below the limit of detection at 30, 60 and 120 min after oral gavage and reached 4–5 μg/g brain 20–40 min after i.p. injection. In conclusion, the developed and validated method should be useful for the accurate and precise quantification of curcumin in target organs from relevant animal models of human diseases.     

SU X (r, L) is separably unirational

We show that the moduli space of SU _X (r, L) of rank r bundles of fixed determinant L on a smooth projective curve X is separably unirational.