Browsing by Author "Norambuena-Contreras, Jose"

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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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    Microwave Heating and Self-Healing Performance of Asphalt Mixtures Containing Metallic Fibres from Recycled Tyres
    (2024) Norambuena-Contreras, Jose; Concha, Jose L.; Varela, Maria J.; Trigos, Laura; Poulikakos, Lily; González Fehrmann, Álvaro Ignacio; Arraigada, Martin
    This study investigates how recycled metal fibres from End-of-Life Tyres (ELTs) affect both microwave heating efficiency and crack healing properties in dense asphalt mixtures. The aim is to improve tyre recyclability by using their fibres in asphalt and exploring their self-healing potential with microwave heating. To achieve this, four dense asphalt mixture designs were studied in the laboratory. Each mixture used the same aggregate gradation and bitumen content, but with three different percentages of metallic fibres by binder volume (i.e., 1.5%, 2.5%, and 3.5%), along with an asphalt mixture without fibres serving as a reference material. The microwave heating properties of the asphalt mixtures and their individual components (i.e., aggregates and bitumen) were measured at six different heating times, ranging from 10 to 60 s. Based on the microwave heating results, the cracking and subsequent self-healing properties of the mixtures were evaluated by exposing them to microwave radiation at three heating times: 30, 40, and 50 s. The main results indicated that adding metallic fibres to facilitate microwave heating of the asphalt mixture is unnecessary because healing can be triggered predominately through the aggregates used. Unlike previous studies, it was observed that the healing level of asphalt mixtures, both with and without metallic fibres, increases with the accumulation of crack-healing cycles. Finally, it was determined that the advised microwave heating time for laboratory-sized mixtures, with or without fibres, is 40 s.
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    Temperature effect of asphalt production on the thermo-chemical properties of Kraft lignin
    (2024) Marquez, J. Waldo; Fuentes, Valentina; Rueda, Eduardo J.; Tundidor-Camba, Alain; Escalona, Nestor; Norambuena-Contreras, Jose; Gonzalez, Alvaro
    Global warming has triggered a series of strategies and efforts to reduce greenhouse gas emissions and increase the reuse and recycling into asphalt pavements. One of these, is the reduction of production temperatures of asphalt mixtures, and the other is using sustainable antioxidants, such as Kraft lignin, with high phenolic content. Kraft lignin is usually mixed at high temperatures without considering the effect of temperature on its antioxidant properties. This research aimed to study the impact of the production temperatures of asphalt mixtures on the thermo-chemical properties of Kraft lignin and its antioxidant capacity. To evaluate these properties, thermogravimetry, infrared spectroscopy, and DPPH tests were done. To validate the results, bitumen-lignin blends were prepared considering representative temperatures for Hot-Mix-Asphalt (HMA), 160 degrees C, and for Warm-Mix-Asphalt (WMA), 135 degrees C. Bitumen-lignin blends were prepared considering 0% and 20% Kraft lignin by total weight bitumen. The blended samples, unaged and aged. were evaluated considering mechanical, rheological, and chemical properties. The main conclusion of the study demonstrated that although Kraft lignin can be used in HMA, using it in mixtures with lower temperatures conserve its properties. WMA production temperatures preserve Kraft lignin's chemical properties, increasing the durability and resilience of bitumen throughout its service life.