Examinando por Autor "Zúñiga, César"
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Ítem Atomic force microscopy (AFM) and 3D confocal microscopy as alternative techniques for the morphological characterization of anodic TiO2 nanoporous layers(Elsevier, 2016-02) Oyarzún, Diego P.; Linarez Pérez, Omar E.; López Teijelo, Manuel; Zúñiga, César; Jeraldo, Eduardo; Geraldo, Daniela A.; Arratia-Perez, RamiroThe morphologic characterization of self-organized TiO2 nanostructures by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) was compared with results obtained by both atomic force microscopy (AFM) and 3D confocal microscopy, which were employed as alternative characterization methods. It is demonstrated that AFM with tuning fork configuration (intermittent mode) is also a powerful tool that allows obtaining conclusive information on the morphology of one-dimensional nanostructures. 3D confocal microscopy employed for the first time for obtaining thickness of nanoporous TiO2 films, is a new and powerful method that provides definite information on thickness of the nanostructures. The results employed for the characterization are fairly reliable besides novel and interesting. © 2015 Elsevier B.V.Ítem Comparative study of the anchorage and the catalytic properties of nanoporous TiO2 films modified with ruthenium (II) and rhenium (I) carbonyl complexes(Elsevier B.V., 2018-02) Oyarzún, Diego P.; Chardon-Noblat, Sylvie; Linarez Pérez, Omar E.; López Teijelo, Manuel; Zúñiga, César; Zarate, Ximena; Shott, Eduardo; Carreño, Alexander; Arratia-Perez, RamiroIn this article we study the anchoring of cis-[Ru(bpyC4pyr)(CO)2(CH3CN)2]2+, cis-[Ru(bpy)2(CO)2]2+ and cis-[Ru(bpyac)(CO)2Cl2], onto nanoporous TiO2 employing electropolymerization, electrostatic interaction and chemical bonding. Also, the [Re(bpyac)(CO)3Cl] rhenium(I) complex for chemical anchorage was analyzed. The characterization of TiO2/Ru(II) and TiO2/Re(I) nanocomposite films was performed by field emission scanning electron microscopy (FESEM), electron dispersive X-ray spectroscopy (EDS) and Raman spectroscopy. In addition, for the more stable nanocomposites obtained, the catalytic properties (solar energy conversion and CO2 reduction) were evaluated. The efficiency improvement in redox process derived from the (photo)electrochemical evidence indicates that modified nanoporous TiO2 structures enhance the rate of charge transfer reactions. © 2018 Elsevier B.V.Ítem Screening of the antileishmanial and antiplasmodial potential of synthetic 2-arylquinoline analogs(Nature Research, 2023-12) Espinosa‑Saez, Roger; Robledo, Sara M.; Pineda, Tatiana; Murillo, Javier; Zúñiga, César; Yañez, Osvaldo; Cantero‑López, Plinio; Saez‑Vega, Alex; Guzmán‑Teran, CamiloIn this study, six analogs of 2-arylquinoline were synthesized and evaluated for their in vitro and in vivo antiplasmodial and leishmanicidal activity. At a later stage, hemolytic activity and druggability were tested in vitro and in silico, respectively, observing as a result: firstly, compounds showed half-maximal effective concentration (EC50) values between 3.6 and 19.3 µM. Likewise, a treatment using the compounds 4a–f caused improvement in most of the treated hamsters and cured some of them. Regarding the antiplasmodial activity, the compounds showed moderate to high activity, although they did not show hemolytic activity. Furthermore, 4e and 4f compounds were not able to control P. berghei infection when administered to animal models. Molecular dynamic simulations, molecular docking and ligand binding affinity indicate good characteristics of the studied compounds, which are expected to be active. And lastly, the compounds are absorbable at the hematoencephalic barrier but not in the gastrointestinal tract. In summary, ADMET properties suggest that these molecules may be used as a safe treatment against Leishmania.Ítem Structural Characterization, DFT Calculation, NCI, Scan-Rate Analysis and Antifungal Activity against Botrytis cinerea of (E)-2-{[(2-Aminopyridin-2-yl)imino]-methyl}-4,6-di-tert-butylphenol (Pyridine Schiff Base)(MDPI, 2020-06) Carreño, Alexander; Paéz-Hernández, Dayán; Cantero-López, Plinio; Zúñiga, César; Nevermann, Jan; Ramírez-Osorio, Angélica; Gacituá, Manuel; Oyarzún, Poldie; Saéz-Cortez, Felipe; Polanco, Rubén; Otero, Carolina; Fuentes, Juan A.Botrytis cinerea is a ubiquitous necrotrophic filamentous fungal phytopathogen that lacks host specificity and can affect more than 1000 different plant species. In this work, we explored L1 [(E)-2-{[(2-aminopyridin-2-yl)imino]-methyl}-4,6-di-tert-butylphenol], a pyridine Schiff base harboring an intramolecular bond (IHB), regarding their antifungal activity against Botrytis cinerea. Moreover, we present a full characterization of the L1 by NMR and powder diffraction, as well as UV-vis, in the presence of previously untested different organic solvents. Complementary timedependent density functional theory (TD-DFT) calculations were performed, and the noncovalent interaction (NCI) index was determined. Moreover, we obtained a scan-rate study on cyclic voltammetry of L1. Finally, we tested the antifungal activity of L1 against two strains of Botrytis cinerea (B05.10, a standard laboratory strain; and A1, a wild type strains isolated from Chilean blueberries). We found that L1 acts as an efficient antifungal agent against Botrytis cinerea at 26 °C, even better than the commercial antifungal agent fenhexamid. Although the antifungal activity was also observed at 4 °C, the effect was less pronounced. These results show the high versatility of this kind of pyridine Schiff bases in biological applications. © 2020 MDPI AG. All rights reserved.Ítem Two new fluorinated phenol derivatives pyridine schiff bases: Synthesis, spectral, theoretical characterization, inclusion in epichlorohydrin-β-cyclodextrin polymer, and antifungal effect(Frontiers Media S.A., 2018-07) Carreño, Alexander; Rodríguez, Leonardo; Páez-Hernández, Dayán; Martin-Trasanco, Rudy; Zúñiga, César; Oyarzún, Diego P.; Gacitúa, Manuel; Schott, Eduardo; Arratia-Pérez, Ramiro; Fuentes, Juan A.It has been reported that the structure of the Schiff bases is fundamental for their function in biomedical applications. Pyridine Schiff bases are characterized by the presence of a pyridine and a phenolic ring, connected by an azomethine group. In this case, the nitrogen present in the pyridine is responsible for antifungal effects, where the phenolic ring may be also participating in this bioactivity. In this study, we synthesized two new pyridine Schiff Bases: (E)-2-[(3-Amino-pyridin-4-ylimino)-methyl]-4,6-difluoro-phenol (F1) and (E)- 2-[(3-Amino-pyridin-4-ylimino)-methyl]-6-fluoro-phenol (F2), which only differ in the fluorine substitutions in the phenolic ring. We fully characterized both F1 and F2 by FTIR, UV-vis, 1H; 13C; 19F-NMR, DEPT, HHCOSY, TOCSY, and cyclic voltammetry, as well as by computational studies (DFT), and NBO analysis. In addition, we assessed the antifungal activity of both F1 (two fluorine substitution at positions 4 and 6 in the phenolic ring) and F2 (one fluorine substitution at position 6 in the phenolic ring) against yeasts. We found that only F1 exerted a clear antifungal activity, showing that, for these kind of Schiff bases, the phenolic ring substitutions can modulate biological properties. In addition, we included F1 and F2 into in epichlorohydrin-β-cyclodextrin polymer (βCD), where the Schiff bases remained inside the βCD as determined by the ki, TGA, DSC, and SBET. We found that the inclusion in βCD improved the solubility in aqueous media and the antifungal activity of both F1 and F2, revealing antimicrobial effects normally hidden by the presence of common solvents (e.g., DMSO) with some cellular inhibitory activity. The study of structural prerequisites for antimicrobial activity, and the inclusion in polymers to improve solubility, is important for the design of new drugs. © 2018 Carreño, Rodríguez, Páez-Hernández, Martin-Trasanco, Zúñiga, Oyarzún, Gacitúa, Schott, Arratia-Pérez and Fuentes.