Browsing by Author "Leal, Matias"

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    Blends based on amino acid functionalized poly (ethylene-alt-maleic anhydride) polyelectrolytes and PEO for nanofiber elaboration: Biocompatible and angiogenic polyelectrolytes
    (2022) Leal, Matias; Leiva, Angel; Villalobos, Valeria; Palma, Veronica; Carrillo, Daniela; Edwards, Natalie; Maine, Arianne; Cauich-Rodriguez, Juan, V; Tamayo, Laura; Neira-Carrillo, Andronico; Urzua, Marcela
    A wide variety of polymers have been electrospun to obtain nanofibers. However, obtaining nanofibers from polyelectrolytes is less frequent due to the charges of these polymers, which hinder the electrospinning process. Poly (ethylene-alt-maleic anhydride) (PEMA) was modified with a series of amino acids (Aa). The functionalization of PEMA with Aa (PEMA-Aa) was demonstrated by FT-IR, H-1 NMR, and C-13 NMR. Blends of PEMA-Aa and poly (ethylene oxide), PEO, with different ratios were prepared. Nanofibers were obtained by electrospinning using blends of 10-20% w/v of PEMA-Aa and 10% w/v of PEO. The conductivity of blends decreased, and the surface tension increased as the quantity of PEO in the blends was increased. TGA showed intermediate thermal properties compared with the blend components. Nanofibers were obtained for all PEMA-Aa/PEO blends, with diameters between 170 and 350 nm. Continuous fibers without morphological defects were obtained at concentrations of 20% w/v and 10% w/v of PEMA-Aa and PEO. Wharton's Jelly Mesenchymal Stem Cells viability, chicken embryo chorioallantoic membrane (CAM) assay and embryo viability measurements were realized for PEMA-Aa. Cytotoxicity test showed both composition and concentration-dependent behavior for PEMA-Aa, with higher WJ-MSC viability at 0.1 mg/mL at 24 h. CAM assay showed the formation of a high number of blood vessels and chicken embryo viability was close to 100% in the presence of polyelectrolytes. This, study demonstrates that electrospun nanofibers obtained from PEMA-Aa/PEO modified polyelectrolyte blends can be considered as a promising material for biomedical applications.
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    Conformational Changes of Poly(Maleic Anhydride-alt-styrene) Modified with Amino Acids in an Aqueous Medium and Their Effect on Cytocompatibility and Hemolytic Response
    (2023) Maine, Arianne; Tamayo, Laura; Leiva, Angel; Gonzalez, Alex; Rios, Hernan E.; Rojas-Romo, Carlos; Jara, Paul; Araya-Duran, Ingrid; Gonzalez-Nilo, Fernando; Yazdani-Pedram, Mehrdad; Santana, Paula; Leal, Matias; Gonzalez, Nicolas; Briones, Ximena; Villalobos, Valeria; Urzua, Marcela
    The conformational changes of poly-(maleic anhydride-alt-styrene) (PSMA) modified with different amino acids (PSMA-Aa) were studied in an aqueous medium as a function of ionic strength and pH. The specific viscosity of PSMA-Aa decreased with increasing salt concentration due to a more compact conformation. There was a decrease in surface tension with increasing concentrations of the modified polyelectrolyte having a greater effect for the PSMA modified with l-phenylalanine at pH 7.0, demonstrating a greater surface-active character. The conformational changes were also confirmed by molecular dynamics studies, indicating that PSMA-Aa exhibits a compact structure at pH 4.0 and a more extended structure at pH 7.0. On the other hand, the conformational changes of PSMA-Aa were related to its biological response, where the higher surface-active character of the PSMA modified with l-phenylalanine correlates very well with the higher hemolytic activity observed in red blood cells, in which the surface-active capacity supports lytic potency in erythrocytes. The cytocompatibility assays indicated that there were no significant cytotoxic effects of the PSMA-Aa. Additionally, in solvent-accessible surface area studies, it was shown that the carboxylate groups of the PSMA modified with l-phenylalanine are more exposed to the solvent at pH 7.0 and high salt concentrations, which correlates with lower fluorescence intensity, reflecting a loss of mitochondrial membrane potential. It is concluded that the study of the conformational changes in PE modified with amino acids is essential for their use as biomaterials and relevant to understanding the possible effects of PE modified with amino acids in biological systems.
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    New Hybrid Nanocomposites with Catalytic Properties Obtained by In Situ Preparation of Gold Nanoparticles on Poly (Ionic Liquid)/Poly (4-Vinylpyridine) Nanofibers
    (2022) Ramirez, Oscar; Leal, Matias; Briones, Ximena; Urzua, Marcela; Bonardd, Sebastian; Saldias, Cesar; Leiva, Angel
    In this work, we report the obtaining of new hybrid nanocomposites with catalytic activity formed by nanofibers of polymer blends and gold nanoparticles. The nanofibers were obtained by electrospinning blends of a poly (ionic liquid) (PIL) and its precursor polymer, poly (4-vinyl pyridine) (P4VPy). The characteristics of the nanofibers obtained proved to be dependent on the proportion of polymer in the blends. The nanofibers obtained were used to synthesize, in situ, gold nanoparticles on their surface by two-step procedure. Firstly, the adsorption of precursor ions on the nanofibers and then their reduction with sodium borohydride to generate gold nanoparticles. The results indicated a significant improvement in the performance of PIL-containing nanofibers over pure P4VPy NFs during ion adsorption, reaching a 20% increase in the amount of adsorbed ions and a 6-fold increase in the respective adsorption constant. The catalytic performance of the obtained hybrid systems in the reduction reaction of 4-nitrophenol to 4-aminophenol was studied. Higher catalytic conversions were obtained using the hybrid nanofibers containing PIL and gold nanoparticles achieving a maximum conversion rate of 98%. Remarkably, the highest value of kinetic constant was obtained for the nanofibers with the highest PIL content.