Cyclodextrins as growth controlling agents for enhancing the catalytic activity of PVP-stabilized Ru(0) nanoparticles

Cyclodextrins act as growth controllers in the synthesis of PVP-stabilized Ru(0) nanoparticles, leading to enhancement of the catalytic activity in the hydrogenation of furfural.     

Inclusion complex of usnic acid with β-cyclodextrin: characterization and nanoencapsulation into liposomes

In this study β-cyclodextrin (β-CD) was used to improve usnic acid (UA) solubility and the inclusion complex (UA:β-CD) was incorporated into liposomes in order to produce a targeted drug delivery system for exploiting the antimycobacterial activity of UA. A phase-solubility assay of UA in β-CD at pH 7.4 was performed. An apparent stability constant of K_1:1 = 234.5 M^?1 and a complexation efficiency of 0.005 was calculated. In the presence of 16 mM of β-CD the solubility of UA (7.3 μg/mL) increased more than 5-fold. The UA:β-CD complex was prepared using the freeze-drying technique and characterized through infrared and ¹HNMR spectroscopy, X-ray diffraction and thermal analyses. The UA:β-CD inclusion complex presented IR spectral modifications when compared with UA and β-CD spectra. ¹HNMR spectrum of UA:β-CD inclusion complex showed significant chemical shifts in proton H5 located inside the cavity of β-CD (Δδ = 0.127 ppm), suggesting that phenyl ring moiety of UA would be expected to be included within the β-CD cavity, interacting with the H-5 proton. A change in UA from its crystalline to amorphous form was observed on X-ray, suggesting the formation of a drug inclusion complex. DSC analysis showed the disappearance of the UA fusion peak UA:βCD complex. No differences between the antimicrobial activity of free UA and UA:βCD were found, supporting the hypothesis that the complexation with cyclodextrin did not interfere with drug activity. Liposomes containing UA:βCD were prepared using hydration of a thin lipid film method with subsequent sonication. Formulations of liposomes containing UA:βCD exhibited a drug encapsulation efficiency of 99.5% and remained stable for four months in a suspension form. Interestingly, the encapsulation of UA:βCD into the liposomes resulted in a modulation of in vitro kinetics of release of UA. Indeed, liposomes containing UA:β-CD presented a more prolonged release profile of free usnic acid compared to usnic acid-loaded liposomes.     

Controlled hydrolysis of lanthanide complexes of the N-donor tripod tris(2-pyridylmethyl)amine versus bisligand complex formation

The reaction of the lanthanide salts LnI3(thf)4 and Ln(OTf)3 with tris(2-pyridylmethyl)amine (tpa) was studied in rigorously anhydrous conditions and in the presence of water. Under rigorously anhydrous conditions the successive formation of mono- and bis(tpa) complexes was observed on addition of 1 and 2 equiv of ligand, respectively. Addition of a third ligand equivalent did not yield additional complexes. The mono(tpa) complex [Ce(tpa)I3] (1) and the bis(tpa) complexes [Ln(tpa)2]X3 (X = I, Ln = La(III) (2), Ln = Ce(III) (3), Ln = Nd(III) (4), Ln = Lu(III) (5); X = OTf, Ln = Eu(III) (6)) were isolated under rigorously anhydrous conditions and their solid-state and solution structures determined. In the presence of water, 1H NMR spectroscopy and ES-MS show that the successive addition of 1-3 equiv of tpa to triflate or iodide salts of the lanthanides results in the formation of mono(tpa) aqua complexes followed by formation of protonated tpa and hydroxo complexes. The solid-state structures of the complexes [Eu(tpa)(H2O)2(OTf)3] (7), [Eu(tpa)(mu-OH)(OTf)2]2 (8), and [Ce(tpa)(mu-OH)(MeCN)(H2O)]2I4 (9) have been determined. The reaction of the bis(tpa) lanthanide complexes with stoichiometric amounts of water yields a facile synthetic route to a family of discrete dimeric hydroxide-bridged lanthanide complexes prepared in a controlled manner. The suggested mechanism for this reaction involves the displacement of one tpa ligand by two water molecules to form the mono(tpa) complex, which subsequently reacts with the noncoordinated tpa to form the dimeric hydroxo species.     

Hepatocyte Targeting and Intracellular Copper Chelation by a Thiol-Containing Glycocyclopeptide

Metal overload plays an important role in several diseases or intoxications, like in Wilson's disease, a major genetic disorder of copper metabolism in humans. To efficiently and selectively decrease copper concentration in the liver that is highly damaged, chelators should be targeted at the hepatocytes. In the present work, we synthesized a molecule able to both lower intracellular copper, namely Cu(I), and target hepatocytes, combining within the same structure a chelating unit and a carbohydrate recognition element. A cyclodecapeptide scaffold displaying a controlled conformation with two independent faces was chosen to introduce both units. One face displays a cluster of carbohydrates to ensure an efficient recognition of the asialoglycoprotein receptors, expressed on the surface of hepatocytes. The second face is devoted to metal ion complexation thanks to the thiolate functions of two cysteine side-chains. To obtain a chelator that is active only once inside the cells, the two thiol functions were oxidized in a disulfide bridge to afford the glycopeptide P(3). Two simple cyclodecapeptides modeling the reduced and complexing form of P(3) in cells proved a high affinity for Cu(I) and a high selectivity with respect to Zn(II). As expected, P(3) becomes an efficient Cu(I) chelator in the presence of glutathione that mimics the intracellular reducing environment. Finally, cellular uptake and ability to lower intracellular copper were demonstrated in hepatic cell lines, in particular in WIF-B9, making P(3) a good candidate to fight copper overload in the liver.     

Self-assembly of soluble anthracene, tetracene and pentacene derivatives

New soluble disubstituted acenes (tetracene, pentacene) have been designed in order to mimic 2,3-alkoxy derivatives of anthracene. They have been shown to self-assemble and gellify a large variety of organic solvents. This process involves the formation of nano-fibres through non-covalent molecular interactions (van der Waals, π-π stacking), weaving a three-dimensional supramolecular network. Efficient transfer of excitation energy through these nano-structures has been evidenced in an anthracene light-harvesting matrix doped with less than 1 mol% of a tetracene energy trap.     

Poling influence on the mechanical properties and molecular mobility of highly piezoelectric P(VDF‐TrFE) copolymer

The calorimetric, dielectric, and mechanical responses of highly piezoelectric 70/30 P(VDF‐TrFE) displaying homogenous d₃₃ of ?19 pC N^?1 are studied. This work aims at better understanding the influence of poling on the mechanical properties of this copolymer. To explain the one decade mechanical modulus drop observed across the Curie transition, a stiffening process of the amorphous phase due to the local electric fields in the ferroelectric crystals is proposed. In poled P(VDF‐TrFE), these fields are preferentially aligned resulting in a more stable and higher modulus below the Curie transition. This hypothesis accounts for the lower dielectric signals obtained with the poled sample. Through the Curie transition, the vanishing of these local electric fields, stemming from progressive disorientation and conversion of ferroelectric crystals to paraelectric ones, releases the constraints on the amorphous phase, leading to a storage modulus drop typical of a viscoelastic transition. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55 , 1414–1422