Browsing by Author "Pavez, Paulina"

Now showing 1 - 7 of 7
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    Crosslinked oxidized-nanocellulose/chitosan hydrogels as a scaffold matrix for mesenchymal stem cell growth
    (2024) Marino, Mayra A.; Oyarce, Karina; Tobar, Catalina; del Rio, Rodrigo Segura; Paredes, Maria G.; Pavez, Paulina; Sarabia, Mauricio; Amoroso, Alejandro; Concha, Jose L.; Norambuena-Contreras, Jose; Barjas, Gustavo Cabrera; Castano, Johanna
    Mesenchymal stem cells (MSC) are recognized for their immunomodulatory effects and regenerative properties, being promising therapeutic agents for a wide range of diseases. To ensure a localized effect of MSC in the organism biobased hydrogels have been tested for their ability to act as a matrix-embedded to improve MSC targeted delivery. In this context, nanocellulose (NC) has been used for drug delivery, showing biocompatibility and durability in time, but until now NC has not been tested for MSC growth exploiting the size and aldehyde content of NC. In this study, cellulose nanocrystals (CNC), cellulose nanofibers (CNF) and microfibrillated cellulose (MFC) were studied after one-pot oxidation and further crosslinking with chitosan (mass ratio 1:5). Size and aldehyde content of oxidized NC samples were evaluated to analyze their influence on the hydrogel's properties. The crosslinked hydrogels were analyzed by FESEM, swelling ability, FTIR, compression tests, thermal stability, and stability in culture cell conditions. Oxidized-MFC hydrogel improved the mechanical stability and swelling behavior, but it lacks stability at cell conditions possibly due to its low aldehyde content (0.54 mmol/g). Conversely, oxidized CNF and oxidized CNC formed suitable crosslinked hydrogels for cell adhesion, and for growing and proliferating of MSC 3D spheroids after 120 h. However, only hydrogel with PO-CNF/chitosan shows antibacterial activity as well as MSC proliferation.
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    Efficient Nucleophilic Degradation of an Organophosphorus Pesticide "Diazinon" Mediated by Green Solvents and Microwave Heating
    (2019) Millán Retamal, Daniela Andrea; Tapia Apati, Ricardo; Pavez, Paulina
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    Ionic liquids: anion effect on the reaction of O,O-diethyl O-(2,4-dinitrophenyl) phosphate triester with piperidine
    (2015) Pavez, Paulina; Millan, Daniela; Cocq, Cristian; Santos, Jose G.; Nome, Faruk
    The reactions of O,O-diethyl 2,4-dinitrophenylphosphate triester (1) with piperidine in ionic liquids and four conventional organic solvents (COS) were subjected to kinetic and product studies. Analytical techniques (UV-vis and NMR) identified two pathways: nucleophilic attack at the phosphoryl center and at the C-1 aromatic carbon. The nucleophilic rate constants (k(N)(T)) for these parallel reactions were separated into two terms: k(N)(P) and k(N)(Ar) for the corresponding electrophilic centers. Both the rate and the selectivities of the reactions are strongly dependent on the nature of the ionic liquid used, and a good correlation with the solvent acceptor capacity to form hydrogen bonds (beta) was observed. Remarkably, an exclusive attack at the phosphoryl center was found using [Bmim] DCA, [Bmpyrr] DCA and [Bmpy] DCA as the reaction solvents. In contrast, with [Bmim]PF6 as the reaction solvent, attack at the C-1 aromatic was the main path (94%). These results suggest that ionic liquids can be considered to be designer solvents because by an appropriate choice of the anion it is possible to steer the selectivity of this reaction.
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    Nucleofugality hierarchy, in the aminolysis reaction of 4-cyanophenyl 4-nitrophenyl carbonate and thionocarbonate. Experimental and theoretical study
    (2021) Montecinos, Rodrigo; Aliaga, Margarita E.; Pavez, Paulina; Cornejo, Patricio; Santos, Jose G.
    Nucleophilic substitution reactions of the title compounds have been investigated with a series of secondary alicyclic amines in several solvents. The solvent, amine, and electrophilic group effects on kinetics, mechanism and nucleofugality hierarchy are discussed from experimental and theoretical studies. These studies show the mechanistic dependence on the solvent polarity; the theoretical results indicate that the relative polarization of the reactive centres (C=O and C=S) and the stabilization of the nucleofuges are the main factors in the control of the product distribution.
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    Nucleophilic Neutralization of Organophosphates: Lack of Selectivity or Plenty of Versatility?
    (2021) Silva, Valmir B.; Campos, Renan B.; Pavez, Paulina; Medeiros, Michelle; Orth, Elisa S.
    Neutralization of organophosphates is an issue of public health and safety, involving agrochemicals and chemical warfare. A promising approach is the nucleophilic neutralization, scope of this review, which focuses on the molecular nucleophiles: hydroxide, imidazole derivatives, alpha nucleophiles, amines and other nucleophiles. A reactivity mapping is given correlating the pathways and reaction efficiency with structural dependence of the nucleophile (basicity) and the organophosphate (electrophilic centers, P=O/P=S shift, leaving and non-leaving group). Reactions extremely unfavorable (>20 years) can be reduced to seconds with various nucleophiles, some which are catalytic. Although there is no universal nucleophile, a lack of selectivity in some cases accounts for plenty of versatility in other reactions. The ideal neutralization requires a solid mechanistic understanding, together with balancing factors such as milder conditions, fast process, selectivity and less toxic products.
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    Photophysics and photochemistry of nalidixic acid
    (2006) Pavez, Paulina; Toro Labbé, Alejandro; Encinas, María Victoria
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    Recycled ionic liquid vs . deep eutectic solvent in cellulose nanocrystals production: Characterization, techno-economic analysis, and life cycle assessment
    (2024) Marino, Mayra A.; Rueda-Ordonez, Diego; Paredes, Maria G.; Tapia, Ricardo A.; Pita, Ramon; Pavez, Paulina
    Three scenarios involving aqueous mixtures of neoteric solvents have been evaluated as solvents and catalysts for the cellulose hydrolysis reaction to obtain CNC in high yields (>70%). The scenarios considered were: scenario 1 (S1) involves a recyclable ionic liquid dilution of [Hmim][(HSO4)(H2SO4)]/H2O (64 wt% IL); scenario 2 (S2) another recyclable dilution of [Hmim][(HSO4)(H2SO4)]//H2O (80 wt% IL) and scenario 3 (S3) S3 ) a non-recyclable ternary deep eutectic solvent (60 wt% DES: choline chloride: oxalic acid/30 wt% PA/10 wt% water). Experimental analysis, techno-economic, and life cycle analysis (LCA) indicate that S1 emerges as a suitable scenario among the three analyzed. S1 demonstrated the highest competitiveness, with a lower raw material cost per gram of CNC produced (US$0.81/g) and lower environmental contributions concerning climate change and fossil fuel depletion, accounting mainly for its recyclability. Therefore, the recyclable dilution of 64 wt% IL used in S1 appears to be the most viable option for sustainable and environmentally conscious CNC production. Besides, the physicochemical properties of the CNC were revealed: aspect ratio range 7-8, high dispersion stability related to zeta potential >-40 mV, good crystallinity range 50-80%, and thermal stability with Tonset> 300 degrees C. These results guided towards a scenario with crucial advantages: a diluted IL that retains its acidity after reuse cycles by a facile recovery process, maintaining high CNC production performance and providing low environmental impacts.