Novel routes to epoxy functionalization of PHA‐based electrospun scaffolds as ways to improve cell adhesion

Straightforward and versatile routes to functionalize the surface of poly(3‐hydroxyalkanoate) (PHA) electrospun fibers for improving cell compatibility are reported under relatively mild conditions. The modification of nanofibrous PHAs is implemented through two different methodologies to introduce epoxy groups on the fiber surface: (1) preliminary chemical conversion of double bonds of unsaturated PHAs into epoxy groups, followed by electrospinning of epoxy‐functionalized PHAs blended with nonfunctionalized PHAs, (2) electrospinning of nonfunctionalized PHAs, followed by glycidyl methacrylate grafting polymerization under UV irradiation. The latter approach offers the advantage to generate a higher density of epoxy groups on the fiber surface. The successful modification is confirmed by ATR‐FTIR, Raman spectroscopy, and TGA measurements. Further, epoxy groups are chemically modified via the attachment of a peptide sequence such as Arg‐Gly‐Asp (RGD), to obtain biomimetic scaffolds. Human mesenchymal stromal cells exhibit a better adhesion on the latter scaffolds than that on nonfunctionalized PHA mats. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 816–824     

Surface modification of poly(butylene terephthalate) nonwoven by photochemistry and biofunctionalization with peptides for blood filtration

The surface of meltblown poly(butylene terephthalate) (PBT) nonwoven was modified by photochemistry using the photolinker O‐succinimidyl 4‐azido‐2,3,5,6‐tetrafluorobenzoate for the introduction of activated ester functions and then coupling of molecular probes or biomolecules. Approximately 4000 pmol of (L )‐4,5‐[³H]‐lysine was fixed per PBT sample (1.13 cm²) and measured by liquid scintillation counting. The method consisted in a two‐step process: (a) coating of the clip (0.05 mg/sample) on the fibrous surface of the PBT followed by UV irradiation (30 min, 254 nm) and (b) coupling of amine‐terminated molecules (10^?3 M in phosphate buffer–CH₃CN [1/1, v/v], 20 h). Moreover, about 2000 pmol of ³H‐lysine can be immobilized on the PBT surface after UV irradiation (without clip) by aminolysis reactions with the created oxygenated functions. The derivatizations (via the clip and UV irradiation only) were stable after long‐term heating at 100 °C in water or under steam‐sterilization conditions. They induce neither modifications of the nonwoven morphology nor cytotoxicity. This method was applied for the grafting of peptides Gly‐Arg‐Gly‐Asp‐Ser and Gly‐Gly‐Gly‐Gly‐Gly to perform blood filtration experiments and to retain the leukocytes. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Palladium-catalyzed coupling of N-tosylhydrazones with ortho substituted aryl halides: synthesis of 4-arylchromenes and related heterocycles

A convenient and efficient procedure for the synthesis of 4-arylchromenes, thiochromenes, and related heterocycles via a four step-sequence has been developed. The first three steps, which involve hydration of alkynes, hydrazones formation, and their Pd-coupling with ortho substituted aryl halides, furnished stereoselectively Z-trisubstituted olefins without any purification of the intermediates generated in each stage. These latter proved to be suitable precursors, in the last step, for the synthesis of the desired heterocycles of biological interest.     

Theoretical investigation of hydrodynamic surface mode in a lined duct with sheared flow and comparison with experiment

A spectral collocation method is used to solve the linearized Euler equations in a duct with shear flow and lined walls in order to identify a possible hydrodynamic instability observed in published experiments. This method is first checked against a reference test case in a cylindrical duct. Then a theoretical test case in a plane bi-dimensional duct with no-slip flow is considered: the Briggs-Bers stability criterion is proved to be valid and it shows that the hydrodynamic instability does correspond to a right-running amplified wave. Eigenmode analyses are then performed on the experimental configuration. An unstable hydrodynamic surface mode is found, with an axial wavenumber and velocity eigenfunctions which are in good agreement with the experimental ones. Acoustic energy calculations show that the hydrodynamic instability paradoxically carries noticeable levels of acoustic energy in the upstream direction. Finally, the influence of Mach number and frequency is investigated.     

Facile Synthesis of Multicompartment Micelles Based on Biocompatible Poly(3‐hydroxyalkanoate)

In this paper, a straightforward method to produce poly(3‐hydroxyalkanoate)‐based multicompartment micelles (MCMs) is presented. Thiol‐ene addition is used to graft sequentially perfluorooctyl chains and poly(ethylene glycol) oligomers onto poly(3‐hydroxyoctanoate‐co‐hydroxyundecenoate) oligomers backbone. Well‐defined copolymers are obtained as shown by ¹H NMR and size‐exclusion chromatography. After nanoprecipitation in water, novel PHA‐based MCMs are evidenced by cryo‐transmission electron microscopy. Moreover, the cytocompatibility of MCMs is demonstrated in vitro via cell viability assay.     

Developmental aspects of amperometric ATP biosensors based on entrapped enzymes

A novel concept for a dual-enzyme-based microbiosensor for the detection of adenosine-5′-triphosphate (ATP) was developed. The employed enzymes pyrroloquinoline quinone-dependent glucose dehydrogenase (PQQ-GDH) and hexokinase were entrapped, using pH-shift-induced precipitation of electrodeposition paint (EDP) at platinum microelectrodes (diameter of 25 µm). PQQ-GDH is known showing a superior activity for glucose conversion at the relevant conditions (low oxygen concentration) for ATP detection in targeted biomedical studies. For immobilizing the two enzymes PQQ-GDH and hexokinase, the deposition conditions of EDP Resydrol AY498w/35WA were adapted to ensure high immobilization rates. Prior to ATP sensing, the conversion of glucose, which is the co-substrate for both enzymatic reactions, was optimized. Optimization was targeted towards ATP measurements in biomedical environments by optimizing the PQQ-GDH sensor for glucose. Therefore, different mediators were tested regarding their electron transfer rate and their compatibility with the enzyme: free-diffusing N-methylphenazonium methyl sulfate (PMS) and ferrocenemethanol, and an immobilized chromium hexacyanoferrate layer at platinum electrode. Free-diffusing ferrocenemethanol reveals high sensitivity towards glucose of 1.5?±?0.4 nA/mM. In a next step, hexokinase was co-entrapped in the polymer film resulting in a sensitivity of up to 290 pA/µM.     

Fluorine‐Directed β‐Galactosylation: Chemical Glycosylation Development by Molecular Editing

Validation of the 2‐fluoro substituent as an inert steering group to control chemical glycosylation is presented. A molecular editing study has revealed that the exceptional levels of diastereocontrol in glycosylation processes by using 2‐fluoro‐3,4,6‐tri‐O‐benzyl glucopyranosyl trichloroacetimidate (TCA) scaffolds are a consequence of the 2R,3S,4S stereotriad. This study has also revealed that epimerization at C4, results in a substantial enhancement in β‐selectivity (up to β/α 300:1).     

Low‐Temperature Growth of Carbon Nanotubes Catalyzed by Sodium‐Based Ingredients

Synthesis of low‐dimensional carbon nanomaterials such as carbon nanotubes (CNTs) is a key driver for achieving advances in energy storage, computing, and multifunctional composites, among other applications. Here, we report high‐yield thermal chemical vapor deposition (CVD) synthesis of CNTs catalyzed by reagent‐grade common sodium‐containing compounds, including NaCl, NaHCO₃, Na₂CO₃, and NaOH, found in table salt, baking soda, and detergents, respectively. Coupled with an oxidative dehydrogenation reaction to crack acetylene at reduced temperatures, Na‐based nanoparticles have been observed to catalyze CNT growth at temperatures below 400 °C. Ex situ and in situ transmission electron microscopy (TEM) reveal unique CNT morphologies and growth characteristics, including a vaporizing Na catalyst phenomenon that we leverage to create CNTs without residual catalyst particles for applications that require metal‐free CNTs. Na is shown to synthesize CNTs on numerous substrates, and as the first alkali group metal catalyst demonstrated for CNT growth, holds great promise for expanding the understanding of nanocarbon synthesis.