Síntesis de nuevas formulaciones para la vehiculización de la curcumina como estrategia antiviral para el tratamiento de las infecciones causadas por el virus zika

El poli(D,L-láctido-co-glicólido) (PLGA) es un copolímero de gran interés para aplicaciones medicinales, debido a que es bioreabsorbible, biocompatible, no tóxico, y su cinética de degradación puede modificarse por la relación de copolimerización de los monómeros. En este estudio, se sintetizó PLGA por apertura de los anillos de los dímeros cíclicos de los monómeros D,L-láctido y glicólido en presencia de octoato estannoso como iniciador y alcohol laurílico como co-iniciador. El PLGA fue caracterizado por técnicas espectroscópicas y térmicas, resultando una relación equimolecular para ambos monómeros, con una temperatura de transición vítrea de aproximadamente 35ºC, características que lo hacen apropiado para liberación controlada de medicamentos. Por otro lado, la curcumina es una sustancia de origen natural de gran interés biológico, que inhibe la actividad de la inosina monofosfato deshidrogenasa (IMPDH) enzima blanco para el descubrimiento de drogas antivirales, en especial las causadas por el flavivirus Zika (ZIKV). Teniendo en cuenta la difícil en la administración de la curcumina como fármaco, se sintetizaron micropartículas de PLGA que encapsulen dicha sustancia, las cuales fueron caracterizadas y se evaluó su efectividad en el tratamiento del ZIKV mediante diferentes ensayos biológicosFil: Pacho, María Natalia. Universidad de Buenos AiresFil: D’Accorso, Norma B. Universidad de Buenos AiresFil: Damonte, Elsa. Universidad de Buenos AiresFil: García, Cybele. Universidad de Buenos Aire

Controlling Nanodomain Morphology of Epoxy Thermosets Modified with Reactive Amine-Containing Epoxidized Poly(styrene‑<i>b</i>‑isoprene‑<i>b</i>‑styrene) Block Copolymer

Controlling nanodomain morphology of nanostructured epoxy thermosets is critical to modulate the mechanical properties of the cross-linked matrix. In this contribution, we demonstrate that this can be achieved by using a suitable block copolymer containing an epoxy soluble block with the ability to react toward the epoxy system during curing. For this purpose we designed an epoxidized poly­(styrene-<i>b</i>-isoprene-<i>b</i>-styrene) block copolymer incorporating amine-reactive functionalities (eSIS-AEP) in the epoxidized block as modifier for an epoxy system, which allowed the formation of nanostructured thermosets with controlled spherelike nanodomain morphology. The eSIS-AEP was obtained in two steps from poly­(styrene-<i>b</i>-isoprene-<i>b</i>-styrene) (SIS) block copolymer by controlled epoxidation of the olefinic block followed by partial oxirane ring-opening reaction using 1-(2-aminoethyl)­piperazine as nucleophile. Before the curing reaction it was observed that poly­(styrene) blocks self-assembled to form ordered spherelike nanostructures in blends of eSIS-AEP with epoxy precursors. Since the amine-reactive moiety was incorporated to the block copolymer so that it could react toward diglicidyl ether of bisphenol A (DGEBA) at a similar temperature than the DGEBA/hardener reaction, the epoxy miscible block of eSIS-AEP (ePI-AEP) was able to react with DGEBA during curing. Once the cross-linked network was formed, the initially obtained spherelike nanodomains were preserved, indicating that no reaction-induced microphase separation of ePI-AEP subchains occurred. A completely different scenario was ascertained for epoxidized SIS block copolymer, which conducted to nonspherical nanodomains due to the uncontrolled epoxidized poly­(isoprene) demixing process during the curing reaction. These results demonstrate the importance of the epoxy soluble block being reactive toward the epoxy precursors to control the morphology of the obtained nanostructure

High-Energy Dissipation Performance in Epoxy Coatings by the Synergistic Effect of Carbon Nanotube/Block Copolymer Conjugates

Hierarchical assembly of hard/soft nanoparticles holds great potential as reinforcements for polymer nanocomposites with tailored properties. Here, we present a facile strategy to integrate polystyrene-grafted carbon nanotubes (PSgCNT) (0.05–0.3 wt %) and poly­(styrene-<i>b</i>-[isoprene-<i>ran</i>-epoxyisoprene]-<i>b</i>-styrene) block copolymer (10 wt %) into epoxy coatings using an ultrasound-assisted noncovalent functionalization process. The method leads to cured nanocomposites with core–shell block copolymer (BCP) nanodomains which are associated with carbon nanotubes (CNT) giving rise to CNT–BCP hybrid structures. Nanocomposite energy dissipation and reduced Young’s Modulus (<i>E</i>*) is determined from force–distance curves by atomic force microscopy operating in the PeakForce QNM imaging mode and compared to thermosets modified with BCP and purified carbon nanotubes (pCNT). Remarkably, nanocomposites bearing PSgCNT–BCP conjugates display an increase in energy dissipation of up to 7.1-fold with respect to neat epoxy and 53% more than materials prepared with pCNT and BCP at the same CNT load (0.3 wt %), while reduced Young’s Modulus shows no significant change with CNT type and increases up to 25% compared to neat epoxy <i>E</i>* at a CNT load of 0.3 wt %. The energy dissipation performance of nanocomposites is also reflected by the lower wear coefficients of materials with PSgCNT and BCP compared to those with pCNT and BCP, as determined by abrasion tests. Furthermore, scanning electron microscopy (SEM) images taken on wear surfaces show that materials incorporating PSgCNT and BCP exhibit much more surface deformation under shear forces in agreement with their higher ability to dissipate more energy before particle release. We propose that the synergistic effect observed in energy dissipation arises from hierarchical assembly of PSgCNT and BCP within the epoxy matrix and provides clues that the CNT–BCP interface has a significant role in the mechanisms of energy dissipation of epoxy coating modified by CNT–BCP conjugates. These findings provide a means to design epoxy-based coatings with high-energy dissipation performance

Synthesis and nematocide activity of S-glycopyranosyl-6,7- diarylthiolumazines

6,7-Diaryl derivatives of mono and di-S-glycopyranosylthiolumazine derivatives 5-8 were prepared to test their nematocide activity. In vitro tests against Caenorhabditis elegans were performed and it was found that monosubstituted derivatives 5-7 showed higher activity than the corresponding unsubstituted 2-thiolumazines 1-3, whilst 2-S,4-S-di-glycopyranosylpteridine derivative 8 was inactive in contrast to unsubstituted derivative 4. In order to check whether the lack of activity of 8 was due to the two bulky substituents of the pteridine nucleus, 2-S,4-S-dimethyl derivative 9 was synthesized and assayed showing also lack of activity. A theoretical study on the stability of the different possible tautomers of compound 4 was carried out in an attempt to explain some, in appearance, anomalous 13C NMR data of this compound. © 2004 Elsevier Ltd. All rights reserved.Peer Reviewe