Multiwalled carbon nanotube-doxorubicin supramolecular complexes for cancer therapeutics

Multiwalled carbon nanotube aqueous dispersions using block copolymers are able to form supramolecular complexes with the aromatic chromophore and anticancer agent doxorubicin via pi-pi stacking and enhance its cytotoxic activity.     

Isolation of calcium phosphate crystals from complex biological fluids using bisphosphonate-modified superparamagnetic beads

The surface of superparamagnetic magnetic beads was modified with bisphosphonates to selectively capture calcium phosphate crystals from complex biological fluids (i.e. synovial fluid).     

A surprise from 1954: siloxane equilibration is a simple, robust, and obvious polymer self-healing mechanism

Tetramethylammonium silanolate-initiated ring-opening copolymerization of octamethylcyclotetrasiloxane (D(4)) and bis(heptamethylcyclotetrasiloxanyl)ethane (bis-D(4)) renders cross-linked network polymers that contain ethylene bridges and active silanolate end groups. These "living" reactive anionic species are not neutralized by ambient atmosphere exposure (are stable to water, oxygen, CO(2)) and promote thermally activated equilibration among different network isomers and cyclic oligomers. The cross-link density of these living networks can be controlled by the ratio of D(4):bis-D(4), and the density of active chain ends is determined from the initiator:monomer ratio. We report that samples prepared with particular ratios of initiator:D(4):bis-D(4) can be cut with a sharp knife, even into two pieces, and can heal by siloxane equilibration to restore the original strength of the silicone sample. Fracture toughness measurements were carried out and revealed complete (mechanical) healing. Broken and healed samples generally failed in locations other than the initially cracked region. We call attention to publications and patents from the 1950s that suggest that this self-healing behavior was likely obvious 60 years ago.     

Contact angle hysteresis explained

A view of contact angle hysteresis from the perspectives of the three-phase contact line and of the kinetics of contact line motion is given. Arguments are made that advancing and receding are discrete events that have different activation energies. That hysteresis can be quantified as an activation energy by the changes in interfacial area is argued. That this is an appropriate way of viewing hysteresis is demonstrated with examples.     

Rediscovering silicones: molecularly smooth, low surface energy, unfilled, UV/vis-transparent, extremely cross-linked, thermally stable, hard, elastic PDMS

We demonstrate the preparation of extremely cross-linked poly(dimethylsiloxane) (PDMS)-based materials and report optical, mechanical, and surface properties. Transparent monolithic molded objects are prepared catalytically with no byproducts; parts per million levels of platinum (catalyst) remain in the articles. Essentially the same material was prepared in 1993 and described as a "hard transparent glass." We confirm the thermal stability and chemical structure described in this report. We show that the catalytic reaction used, which was reported in 1999 always to exhibit a "violent exotherm", can be controlled conveniently using a low (parts per million) catalyst concentration. The combination of low surface energy, transparency, hardness, elasticity, and thermal stability makes this an unusual and interesting material. That it can be prepared from commercially available low-viscosity monomers adds to its interest. We comment that the class of materials known as siloxanes or silicones and PDMS in particular is not currently generally well understood (or taught) and review aspects of the structure, properties, and cross-linking chemistry of PDMS.     

Entropy generation across Earth's collisionless bow shock

Earth's bow shock is a collisionless shock wave but entropy has never been directly measured across it. The plasma experiments on Cluster and Double Star measure 3D plasma distributions upstream and downstream of the bow shock allowing calculation of Boltzmann's entropy function H and his famous H theorem, dH/dt≤0. The collisionless Boltzmann (Vlasov) equation predicts that the total entropy does not change if the distribution function across the shock becomes nonthermal, but it allows changes in the entropy density. Here, we present the first direct measurements of entropy density changes across Earth's bow shock and show that the results generally support the model of the Vlasov analysis. These observations are a starting point for a more sophisticated analysis that includes 3D computer modeling of collisionless shocks with input from observed particles, waves, and turbulences.     

Development and validation of a rapid multiplex ELISA for pyrrolizidine alkaloids and their N-oxides in honey and feed

Pyrrolizidine alkaloids (PAs) are a group of plant secondary metabolites with carcinogenic and hepatotoxic properties. When PA-producing plants contaminate crops, toxins can be transferred through the food chain and cause illness in humans and animals, most notably hepatic veno-occlusive disease. Honey has been identified as a direct risk of human exposure. The European Food Safety Authority has recently identified four groups of PAs that are of particular importance for food and feed: senecionine-type, lycopsamine-type, heliotrine-type and monocrotaline-type. Liquid or gas chromatography methods are currently used to detect PAs but there are no rapid screening assays available commercially. Therefore, the aim of this study was to develop a rapid multiplex ELISA test for the representatives of three groups of alkaloids (senecionine, lycopsamine and heliotrine types) that would be used as a risk-management tool for the screening of these toxic compounds in food and feed. The method was validated for honey and feed matrices and was demonstrated to have a detection capability less than 25 μg/kg for jacobine, lycopsamine, heliotrine and senecionine. The zinc reduction step introduced to the extraction procedure allows for the additional detection of the presence of N-oxides of PAs. This first multiplex immunoassay for PA detection with N-oxide reduction can be used for the simultaneous screening of 21 samples for >12 PA analytes. Honey samples (n?=?146) from various origins were analysed for PA determination. Six samples were determined to contain measurable PAs >25 μg/kg by ELISA which correlated to >10 μg/kg by LC-MS/MS.