Synthesis of solvatochromic merocyanine dyes and their immobilization to polymers

Solvatochromic merocyanine dyes were immobilized onto polymer surfaces and copolymerized with acrylic resins, yielding novel reversibly solvatochromic polymers, which were used as solvent polarity indicators that exhibited different colors in water and alcohols. To generate solvatochromic polymer for solvent polarity indication, two solvatochromic merocyanine dyes containing moieties, which allow their immobilization onto polymer surfaces, or copolymerization with acrylic and vinyl monomers, were sequentially synthesized in four and six steps. Merocyanine dye (E)‐2‐(2‐(1‐(6‐aminohexyl)pyridinium‐4‐yl)vinyl)‐4,6‐dichlorophenolate (AHPVD) was prepared with a terminal aminohexyl group which allowed covalent bonding to activated carboxylated or sulfonated polymeric materials. The dyes were covalently bonded to the polymer surfaces, such as, nylon, polycarbonate, polyethylene terephthalate, and silicone. Solvatochromic merocyanine dye (E)‐2‐(2‐(1‐(6‐acrylamidohexyl)pyridinium‐4‐yl)vinyl)‐4,6‐dichlorophenolate (AAPVD) was synthesized for radical copolymerization with acrylate and vinyl monomers and oligomers. Side‐chain solvatochromic merocyanine‐containing hydrophilic polymers with differential water and alcohol absorption were obtained upon photoinitiated radical copolymerization with specially formulated acrylated resins. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44451.     

Deformation Control During Thermal Treatment of Electrospun PbZr0.52Ti0.48O3 Nanofiber Mats

This paper focuses on the deformation origin of PbZr_0.52Ti_0.48O₃ (PZT) fiber mats obtained by electrospinning. The main cause of deformation of the green mats during heating was found to be a nonuniform relaxation of the stretched PVP polymer, due to nonuniform thermal decomposition of the Pb‐hexanoate in the fibers. This relaxation starts under 100°C, well below the polymer decomposition temperature. The shrinkage was found to accelerate above the polymer glass transition point, giving rise to an overall linear change of almost 50%. The “green” PZT mats were easily separated from the collector by first depositing a pure PVP sublayer on the collector. An optimal fabrication and slow multistep thermal treatment process that provides fiber mats with desired PZT phase and overcomes the nonuniform deformation is described.     

Homochirality of Organic Matter – Objective Law or Curious Incident?

Of the many hypotheses on the origin of biological homochirality on the Earth, the combination of the notion of subatomic particles composing a homochiral pool of primary matter, on the one hand, with the suggestion of the synthesis of chiral organic molecules in the plasma torch generated by super-high-velocity impacts (SHVI) of meteorites, on the other hand, was chosen as the working assumption.     

Self-disproportionation of Enantiomers (SDE) of Chiral Nonracemic Amides via Achiral Chromatography

This article is based on a review of literature devoted to the phenomenon of SDE via achiral chromatography since the appearance of the seminal work of Professor Emanuel Gil-Av. The discussed examples of chromatographic studies are related to amides derived from chiral amines and α- and β-amino acids. We discuss the observed SDE magnitude as a function of a compound's structure, and composition of eluent and stationary phases, providing some mechanistic considerations. Particular emphasis is given to the aspect of SDE via achiral chromatography as an emerging unconventional enantiomeric purification technique.     

Complex Formation of Divalent Cations with Carboxylic Acid Resins as a Factor Determining Different Stationary States of Their Swelling

Three samples of carboxylic acid gel-type cross-linked polyelectrolytes were examined by registering the extent and kinetics of their volume change depending on the temperature, concentration, and nature of external electrolyte solutions, as well as the initial state (ionic form, water content) of the bead. It is found that in some systems the swelling of the bead (as a result of lowering the temperature) proceeds much more slowly than the preceding shrinking (as a result of the increase of temperature). Moreover, the initial volume of the bead is not restored, and a new stationary state of swelling is established. By means of optical dilatometry, it is found that in the systems in which the differences in the stationary states of swelling are found, the beads display plasto-elastic properties, whereas in the absence of such differences the beads show elastic properties. It is found that different stationary states of swelling are also established when the beads of copolymer of methacrylic acid cross-linked with divinylbenzene in Na⁺ form in the dry state and in the NaCl solution-swollen state are placed into a solution of a divalent cation salt. The difference in the stationary states of swelling reaches 12% in 4 N NiCl₂ solution. The substantial differences in the swelling behavior and viscoelastic properties of the resins in their Na⁺, Mg²⁺, Ca²⁺, and Ni²⁺ forms are interpreted in terms of formation of different kinds of complexes of functional groups of the polymer with Ca²⁺ and Ni²⁺ ions.     

Bivalent EGFR-Targeting DARPin-MMAE Conjugates

Epidermal growth factor receptor (EGFR) is a validated tumor marker overexpressed in various cancers such as squamous cell carcinoma (SSC) of the head and neck and gliomas. We constructed protein-drug conjugates based on the anti-EGFR Designed Ankyrin Repeat Protein (DARPin) E01, and compared the bivalent DARPin dimer (DD1) and a DARPin-Fc (DFc) to the monomeric DARPin (DM) and the antibody derived scFv425-Fc (scFvFc) in cell culture and a mouse model. The modular conjugation system, which was successfully applied for the preparation of protein-drug and -dye conjugates, uses bio-orthogonal protein-aldehyde generation by the formylglycine-generating enzyme (FGE). The generated carbonyl moiety is addressed by a bifunctional linker with a pyrazolone for a tandem Knoevenagel reaction and an azide for strain-promoted azide-alkyne cycloaddition (SPAAC). The latter reaction with a PEGylated linker containing a dibenzocyclooctyne (DBCO) for SPAAC and monomethyl auristatin E (MMAE) as the toxin provided the stable conjugates DD1-MMAE (drug-antibody ratio, DAR = 2.0) and DFc-MMAE (DAR = 4.0) with sub-nanomolar cytotoxicity against the human squamous carcinoma derived A431 cells. In vivo imaging of Alexa Fluor 647-dye conjugates in A431-xenografted mice bearing subcutaneous tumors as the SCC model revealed unspecific binding of bivalent DARPins to the ubiquitously expressed EGFR. Tumor-targeting was verified 6 h post-injection solely for DD1 and scFvFc. The total of four administrations of 6.5 mg/kg DD1-MMAE or DFc-MMAE twice weekly did not cause any sequela in mice. MMAE conjugates showed no significant anti-tumor efficacy in vivo, but a trend towards increased necrotic areas (p = 0.2213) was observed for the DD1-MMAE (n = 5).     

Sterically Hindered Quaternary Phosphonium Salts (QPSs): Antimicrobial Activity and Hemolytic and Cytotoxic Properties

Structure–activity relationships are important for the design of biocides and sanitizers. During the spread of resistant strains of pathogenic microbes, insights into the correlation between structure and activity become especially significant. The most commonly used biocides are nitrogen-containing compounds; the phosphorus-containing ones have been studied to a lesser extent. In the present study, a broad range of sterically hindered quaternary phosphonium salts (QPSs) based on tri-tert-butylphosphine was tested for their activity against Gram-positive (Staphylococcus aureus, Bacillus cereus, Enterococcus faecalis) and Gram-negative (Escherichia coli, Pseudomonas aeruginosa) bacteria and fungi (Candida albicans, Trichophyton mentagrophytes var. gypseum). The cation structure was confirmed to determine their biological activity. A number of QPSs not only exhibit high activity against both Gram-positive and -negative bacteria but also possess antifungal properties. Additionally, the hemolytic and cytotoxic properties of QPSs were determined using blood and a normal liver cell line, respectively. The results show that tri-tert-butyl(n-dodecyl)phosphonium and tri-tert-butyl(n-tridecyl)phosphonium bromides exhibit both low cytotoxicity against normal human cells and high antimicrobial activity against bacteria, including methicillin-resistant strains S. aureus (MRSA). The mechanism of QPS action on microbes is discussed. Due to their high selectivity for pathogens, sterically hindered QPSs could serve as effective tunable biocides.     

AICAR Protects Vascular Endothelial Cells from Oxidative Injury Induced by the Long-Term Palmitate Excess

Hyperlipidemia manifested by high blood levels of free fatty acids (FFA) and lipoprotein triglycerides is critical for the progression of type 2 diabetes (T2D) and its cardiovascular complications via vascular endothelial dysfunction. However, attempts to assess high FFA effects in endothelial culture often result in early cell apoptosis that poorly recapitulates a much slower pace of vascular deterioration in vivo and does not provide for the longer-term studies of endothelial lipotoxicity in vitro. Here, we report that palmitate (PA), a typical FFA, does not impair, by itself, endothelial barrier and insulin signaling in human umbilical vein endothelial cells (HUVEC), but increases NO release, reactive oxygen species (ROS) generation, and protein labeling by malondialdehyde (MDA) hallmarking oxidative stress and increased lipid peroxidation. This PA-induced stress eventually resulted in the loss of cell viability coincident with loss of insulin signaling. Supplementation with 5-aminoimidazole-4-carboxamide-riboside (AICAR) increased endothelial AMP-activated protein kinase (AMPK) activity, supported insulin signaling, and prevented the PA-induced increases in NO, ROS, and MDA, thus allowing to maintain HUVEC viability and barrier, and providing the means to study the long-term effects of high FFA levels in endothelial cultures. An upgraded cell-based model reproduces FFA-induced insulin resistance by demonstrating decreased NO production by vascular endothelium.     

复合材料深度方向超声C扫描检测技术

介绍一种基于超声传播时域特性的深度方向超声C扫描成象检测技术,一次扫描可以同时获取被测材料内部若干层的扫描检测图象。