Electrospun Membranes of Poly(butylene succinate) and Poly(butylene/2-butyl,2-ethyl-propylene succinate)

Poly(butylene succinate) (PBS) and poly(butylene/2-butyl,2-ethyl-propylene succinate) (PBSBEPS) membranes are prepared by electrospinning technique. In recent years, interest in biodegradable aliphatic polyesters, including PBS and its copolymers, is increasing as they have potential applications in various sectors such as mulching films, food packaging, tissue engineering, and drug delivery. In this work, the synthesized polymers are dissolved in different solvents, namely acetone, chloroform (CHCl3), methanol, dichloromethane (DCM), and dimethylformamide in order to obtain the best solvent system. These solutions are then electrospun at room temperature to produce micron-sized fibers. The variables examined in determining the optimal solution and electrospinning conditions are the solvent system used, the concentration of PBS and PBS-based random copolymer, applied voltage, flow rate, humidity, and the distance between the needle tip and the collector, all of which have a meaningful effect on the fiber morphology. Among the various solvents used, the DCM and the less toxic CHCl3 result in fewer bead defects among fibers. Besides, an increase in PBS and PBS-based random copolymer concentration determines the reduction of bead defects, which from 12 to 14 wt% results in bead-free uniform fibers, when suitable processing parameters are set. Promising results, which can pave the way for the production of membranes loaded with appropriate anticancer molecules for targeted biomedical applications, are obtained

Regioselective Photooxidation of Citronellol: A Way to Monomers fo Functionalized Bio-Polyesters

Dye-sensitized photooxygenation reaction of bio-based double bond-containing substrates is proposed as sustainable functionalization of terpenes and terpenoids to transform them into polyoxygenated compounds to be employed for the synthesis of new bio-based polyesters. As proof of concept, citronellol 1 has been regioselectively converted into diol 4 using singlet oxygen (O-1(2)), a traceless reagent that can be generated from air, visible light and zeolite supported-photosensitizer (Thionine-NaY). With our synthetic approach, diol 4 has been obtained in two-steps, with good regioselectivity, using green reagents such as light and air, and finally a solvent-free oxidation step. From this compound, a citronellol-based copolyester of poly(butylene succinate) (PBS) has been synthesized and fully characterized. The results obtained evidence that the proposed copolymerization of PBS with the citronellol-based building blocks allows to obtain a more flexible and functionalizable material, by exploiting a largely available natural molecule modified through a green synthetic path

Cold-crystallization of poly(butylene 2,6-naphthalate) following Ostwald's rule of stages

© 2018 Elsevier B.V. Melt-crystallization of poly (butylene 2,6-naphthalate) (PBN) at temperatures lower than about 160 °C follows Ostwald's rule of stages, leading first to formation of a transient smectic liquid crystalline phase (LC) which then may convert in a second step into crystals, controlled by kinetics. In the present work, the PBN melt was cooled at different rates in a fast scanning chip calorimeter to below the glass transition temperature, to obtain different structural states before analysis of the cold-crystallization behavior on heating. It was found that heating of fully amorphous PBN at 1000 K/s leads to a similar two-step crystallization process as on cooling the quiescent melt, with LC-formation occurring slightly above Tg and their transformation into crystals at their stability limit close to 200 °C. In-situ polarized-light optical microscopy provided information that the transition of the LC-phase into crystals on slow heating is not connected with a change of the micrometer-scale superstructure, as the recently found Schlieren texture remains unchanged

Effects of the blending ratio on the design of keratin/poly (Butylene succinate) nanofibers for drug delivery applications

In recent years there has been a growing interest in the use of proteins as biocompatible and environmentally friendly biomolecules for the design of wound healing and drug delivery sys-tems. Keratin is a fascinating protein, obtainable from several keratinous biomasses such as wool, hair or nails, with intrinsic bioactive properties including stimulatory effects on wound repair and excellent carrier capability. In this work keratin/poly (butylene succinate) blend solutions with functional properties tunable by manipulating the polymer blending ratios were prepared by using 1,1,1,3,3,3‐hexafluoroisopropanol as common solvent. Afterwards, these solutions doped with rho-damine B (RhB), were electrospun into blend mats and the drug release mechanism and kinetics as a function of blend composition was studied, in order to understand the potential of such mem-branes as drug delivery systems. The electrophoresis analysis carried out on keratin revealed that the solvent used does not degrade the protein. Moreover, all the blend solutions showed a non‐ Newtonian behavior, among which the Keratin/PBS 70/30 and 30/70 ones showed an amplified orientation ability of the polymer chains when subjected to a shear stress. Therefore, the resulting nan-ofibers showed thinner mean diameters and narrower diameter distributions compared to the Ker-atin/PBS 50/50 blend solution. The thermal stability and the mechanical properties of the blend elec-trospun mats improved by increasing the PBS content. Finally, the RhB release rate increased by increasing the keratin content of the mats and the drug diffused as drug‐protein complex

Laser-Induced Periodic Surface Structures on Conjugated Polymers: Poly(3-hexylthiophene)

8 pags.; 11 figs.© 2015 American Chemical Society. In this work, we report on the surface patterning of semiconducting poly(3-hexylthiophene) (P3HT) thin films by means of laser-induced periodic surface structures (LIPSS). Two different laser wavelengths, 266 and 532 nm, and a broad range of fluences and number of pulses have been used in order to optimize the LIPSS morphology. Ripples period and depth can be tuned by laser parameters. In particular, the high optical absorption of P3HT at 532 nm enables the formation of well-ordered nanostructures with periodicities around 460 nm. Near edge X-ray absorption fine structure (NEXAFS) and Raman spectroscopy reveal a good chemical stability of P3HT thin films during LIPSS formation. Conducting atomic force microscopy (C-AFM) performed on the LIPSS reveals a higher electrical conduction in the trenches than in the ridge regions. Resonance Raman spectroscopy and grazing incidence wide-angle X-ray scattering (GIWAXS) indicate a loss of crystallinity of P3HT thin films during LIPSS formation, suggesting melting of the outer polymer surface. This effect produces ridges with molecular order lower than that of the original thin film. As a consequence of this transformation, the electrical conduction in the ridges becomes lower than that in the trenches.The authors gratefully acknowledge the financial support of the Spanish Ministry of Economy and Competitiveness (MINECO) through Projects MAT 2011-23455, MAT 2012-33517 and CTQ 2013-43086-P. A.R.-R. and E.R. are indebted to MINECO for a FPI (BES-2013-062620) and Ramon y Cajal (RYC-2011-08069) contracts, respectively. We thank the Swiss Light Source for beamtime at PolLux, where the NEXAFS experiments were performed. We also thank the ESRF for beamtime at BM26 where in situ GISAXS and GIWAXS experiments were carried out. We thank B. Watts for assistance in using beamline PolLux and G. Portale and W. Bras for beamline support at BM26. P. Müller-Buschbaum and S. Guo are thanked for seminal comments at the beginning of this workPeer Reviewe

Enthalpy of formation and disordering temperature of transient monotropic liquid crystals of poly(butylene 2,6-naphthalate)

© 2018 Elsevier Ltd Melt-crystallization of poly(butylene 2,6-naphthalate) (PBN) at temperatures lower than about 160 °C follows Ostwald's rule of stages via intermediate formation of a smectic liquid crystalline phase (LC-phase). The transient LC-phase has been isolated by interruption of the isothermal crystallization process at 140 °C at sub-second timescale, and then its disordering was analyzed on heating at a rate of 2000 K/s, which suppresses the transition into α-crystals. The disordering temperature of the LC-mesophase is slightly lower than 200 °C, and as such 20–30 K lower than the melting temperature of α-crystals formed from the LC-phase at 140 °C. Analysis of the bulk enthalpy of formation of the LC-phase revealed that it covers only 20–25% of the total bulk enthalpy of crystallization, which is considered further proof of its smectic nature

On the assessment by grazing-incidence small-angle X-ray scattering of replica quality in polymer gratings fabricated by nanoimprint lithography

Grazing-incidence small-angle X-ray scattering (GISAXS) can be used to characterize the replica quality of polymer gratings prepared by thermal nanoimprint lithography (NIL). Here it is shown using GISAXS experiments that a series of NIL polymer gratings with different line quality present characteristic features that can be associated with the level of defects per line. Both stamps and NIL polymer gratings exhibit characteristic semicircle-like GISAXS patterns. However NIL polymer gratings with defective lines exhibit GISAXS patterns with an excess of diffuse scattering as compared to those of the corresponding stamps. In a first approach, this effect is attributed to a reduction of the effective length of the lines diffracting coherently as the number of defects per line increases

Antioxidant capacity of durum wheat large flour particles may be evaluated by QUENCHER_ABTS assay by adopting a proper calculation mode

Assessment of Antioxidant Capacity (AC) of foods is useful to consider cumulative/ synergistic action of all dietary antioxidants, thus providing a more integrated information than the simple sum of measurable antioxidants. Among the different AC assays, the QUENCHERABTS (QUick, Easy, New, CHEap and Reproducible) procedure is based on the direct reaction of ABTS•+ reagent with fine solid food particles without extraction of antioxidants. This assay is able to measure both soluble and insoluble antioxidants, that simultaneously come into contact with ABTS•+ molecules by either liquid–liquid or solid–liquid interactions, respectively. These interactions may change depending on the particle diameter. Usually, particles having 0.1–0.3 mm size are used. Here, AC was evaluated on whole flour (WF), derived from a mix of grains of ten durum wheat varieties, characterized by three different particle sizes: a smaller one, ≤0.2 mm (control, WF0.2), and two larger ones, ≤0.5 mm and ≤1 mm (WF0.5 and WF1, respectively). Moreover, a novel AC calculation procedure based on the slope value of the regression line of ABTS•+ response vs flour amount is presented in detail. The classical QUENCHERABTS procedure provided for WF0.2 an AC value of 42.0±2.7 μmol eq. Trolox/g d.w. A similar result was obtained for WF0.5 (38.3±0.9 μmol eq. Trolox/g d.w.), thus indicating that these large particles may be analyzed by the QUENCHERABTS assay provided that the “slope” calculation procedure is used. On the contrary, WF1 showed about half AC (20.3±0.2 μmol eq. Trolox/g d.w.), thus showing that very large particles cannot be used even adopting the “slope” calculation

The Dynamin Chemical Inhibitor Dynasore Impairs Cholesterol Trafficking and Sterol-Sensitive Genes Transcription in Human HeLa Cells and Macrophages

Intracellular transport of cholesterol contributes to the regulation of cellular cholesterol homeostasis by mechanisms that are yet poorly defined. In this study, we characterized the impact of dynasore, a recently described drug that specifically inhibits the enzymatic activity of dynamin, a GTPase regulating receptor endocytosis and cholesterol trafficking. Dynasore strongly inhibited the uptake of low-density lipoprotein (LDL) in HeLa cells, and to a lower extent in human macrophages. In both cell types, dynasore treatment led to the abnormal accumulation of LDL and free cholesterol (FC) within the endolysosomal network. The measure of cholesterol esters (CE) further showed that the delivery of regulatory cholesterol to the endoplasmic reticulum (ER) was deficient. This resulted in the inhibition of the transcriptional control of the three major sterol-sensitive genes, sterol-regulatory element binding protein 2 (SREBP-2), 3-hydroxy-3-methyl-coenzymeA reductase (HMGCoAR), and low-density lipoprotein receptor (LDLR). The sequestration of cholesterol in the endolysosomal compartment impaired both the active and passive cholesterol efflux in HMDM. Our data further illustrate the importance of membrane trafficking in cholesterol homeostasis and validate dynasore as a new pharmacological tool to study the intracellular transport of cholesterol