Browsing by Author "Valdes, Oscar"

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    Comparative Study of Three Dyes' Adsorption onto Activated Carbon from Chenopodium quinoa Willd and Quillaja saponaria
    (2022) Abril, Diana; Ferrer, Victor; Mirabal-Gallardo, Yaneris; Cabrera-Barjas, Gustavo; Segura, Cristina; Marican, Adolfo; Pereira, Alfredo; Duran-Lara, Esteban F.; Valdes, Oscar
    The present study shows porous activated carbon obtained from Chenopodium quinoa Willd and Quillaja saponaria and their use as potential adsorbents to remove three types of dyes from aqueous solutions. The adsorption results were compared with commercial charcoal to check their efficiency. All porous carbon materials were activated using carbon dioxide and steam and fully characterized. Moreover, the steam-activated samples exhibited a high total pore volume with a BET surface area of around 800 m(2) g(-1). Batch adsorption experiments showed that commercial charcoal is the charcoal that offered the best adsorption efficiency for tartrazine and sunset yellow FCF. However, in the case of crystal violet, all activated carbons obtained from Chenopodium quinoa Willd and Quillaja saponaria showed the best captures, outperforming commercial charcoal. Molecular dockings of the dyes on the commercial charcoal surface were performed using AutoDock Vina. The kinetic results of the three isotherm's models for the present data follow the order: Langmuir similar to Freundlich > Temkin.
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    Effect of cellulose nanofibrils on vancomycin drug release from chitosan nanocomposite films
    (2023) Cabrera-Barjas, Gustavo; Becheran, Liliam; Valdes, Oscar; Giordano, Ady; Segura-del Rio, Rodrigo; Bravo-Arrepol, Gaston; Duran-Lara, Esteban F.; Cea, Juan; Berg, Alex; Castanos, Johana; Rodriguez-Llamazares, Saddys; Fuentes, Gaston; Katsarov, Plamen; Lukova, Paolina; Delattre, Cedric
    Overuse of antibiotic drugs usually leads to the further development of resistance to targeted bacteria. In this context, a controlled release system could be a solution to achieve higher drug efficiency without overdosing and drug resistance. In this work, nanocomposite films based on chitosan (CHI) reinforced with cellulose nanofibrils (CNF) for antibiotic release were prepared and characterized. Several nanocomposite films containing vancomycin hydrochloride and different amounts of CNF (5, 10, and 20 wt%) were prepared by the solvent casting method. Spectroscopic (FTIR), thermal (TG), morphological (SEM), mechanical, and swelling analyses of the films were performed to study the effect of nanofibers content on the nanocomposite properties. A good dispersion of CNF and the model drug was observed in the CHI matrix. FTIR spectroscopy confirmed the interaction between the film components (CNF and CHI). Film swelling capacity decreased with an increase of CNF content in the film formulation, whereas stiffness and tensile strength of the film increased. In addition, vancomycin release at pH = 7.4 was studied, and it was observed that controlled slower release could be achieved by tuning the CNF content in the chitosan film. The results confirm that these films could be useful for pharmaceutical purposes where the controlled release of drugs is required.
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    Influence of chitin nanofibers and gallic acid on physical-chemical and biological performances of chitosan-based films
    (2024) Cabrera-Barjas, Gustavo; Albornoz, Karin; Belchi, Maria Dolores Lopez; Giordano, Ady; Bravo-Arrepol, Gaston; Moya-Elizondo, Ernesto; San Martin, Juan; Valdes, Oscar; Nesic, Aleksandra
    In this work, chitosan films loaded with gallic acid and different content of chitin nanofibers were prepared and subjected to different characterization techniques. The results showed that the inclusion of gallic acid to chitosan films caused moderate decrease in water vapor permeability (by 29 %) and increased tensile strength of films (by 169 %) in comparison to the neat chitosan films. Furthermore, it was found that the addition of chitin nanofibers up to 30 % into chitosan/gallic acid films additionally improved tensile strength (by 474 %) and reduced plasticity of films (by 171 %), when compared to the chitosan/gallic acid films. Increased concentration of chitin nanofibers in films reduced the overall water vapor permeability of films by 51 %. In addition, gallic acid and chitin nanofibers had synergic effect on high chitosan film's antioxidant and antifungal activity toward Botrytis cinerea (both above 95 %). Finally, chitosan/gallic acid/chitin nanofibers films reduced decay incidence of strawberries, increased total soluble solid content, and promoted high production of some polyphenols during cold storage, in comparison to the control chitosan films and uncoated strawberry samples. Hence, these results suggest that chitosan/gallic acid/chitin nanofibers can present eco-sustainable approach for preservation of strawberries, giving them additional nutritional value.
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    Sulfated Polysaccharide Extracted from the Green Algae Codium bernabei: Physicochemical Characterization and Antioxidant, Anticoagulant and Antitumor Activity
    (2022) Figueroa, Fabian A.; Abdala-Diaz, Roberto T.; Perez, Claudia; Casas-Arrojo, Virginia; Nesic, Aleksandra; Tapia, Cecilia; Duran, Carla; Valdes, Oscar; Parra, Carolina; Bravo-Arrepol, Gaston; Soto, Luis; Becerra, Jose; Cabrera-Barjas, Gustavo
    Codium bernabei is a green alga that grows on Chilean coasts. The composition of its structural polysaccharides is still unknown. Hence, the aim of this work is to isolate and characterize the hot water extracted polysaccharide fractions. For this purpose, the water extracts were further precipitated in alcohol (TPs) and acid media (APs), respectively. Both fractions were characterized using different physicochemical techniques such as GC-MS, GPC, FTIR, TGA, and SEM. It is confirmed that the extracted fractions are mainly made of sulfated galactan unit, with a degree of sulfation of 19.3% (TPs) and 17.4% (ATs) and a protein content of 3.5% in APs and 15.6% in TPs. Other neutral sugars such as xylose, glucose, galactose, fucose, mannose, and arabinose were found in a molar ratio (0.05:0.6:1.0:0.02:0.14:0.11) for TPs and (0.05:0.31:1.0:0.03:0.1:0.13) for ATs. The molecular weight of the polysaccharide samples was lower than 20 kDa. Both polysaccharides were thermally stable (Tonset > 190 degrees C) and showed antioxidant activity according to the ABTS(center dot+) and DPPH tests, where TPs fractions had higher scavenging activity (35%) compared to the APs fractions. The PT and APTTS assays were used to measure the anticoagulant activity of the polysaccharide fractions. In general, the PT activity of the TPs and APs was not different from normal plasma values. The exception was the TPs treatment at 1000 mu g mL(-1) concentration. The APTTS test revealed that clotting time for both polysaccharides was prolonged regarding normal values at 1000 mu g mL(-1). Finally, the antitumor test in colorectal carcinoma (HTC-116) cell line, breast cancer (MCF-7) and human leukemia (HL-60) cell lines showed the cytotoxic effect of TPs and APs. Those results suggest the potential biotechnological application of sulfate galactan polysaccharides isolated from a Chilean marine resource.