Browsing by Author "Rodriguez-Umanzor, Fernando E."

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    Fabrication and Testing of Multi-Hierarchical Porous Scaffolds Designed for Bone Regeneration via Additive Manufacturing Processes
    (2022) Gonzalez-Henriquez, Carmen M.; Rodriguez-Umanzor, Fernando E.; Acuna-Ruiz, Nicolas F.; Vera-Rojas, Gloria E.; Terraza-Inostroza, Claudio; Cohn-Inostroza, Nicolas A.; Utrera, Andres; Sarabia-Vallejos, Mauricio A.; Rodriguez-Hernandez, Juan
    Bone implants or replacements are very scarce due to the low donor availability and the high rate of body rejection. For this reason, tissue engineering strategies have been developed as alternative solutions to this problem. This research sought to create a cellular scaffold with an intricate and complex network of interconnected pores and microchannels using salt leaching and additive manufacturing (3D printing) methods that mimic the hierarchical internal structure of the bone. A biocompatible hydrogel film (based on poly-ethylene glycol) was used to cover the surface of different polymeric scaffolds. This thin film was then exposed to various stimuli to spontaneously form wrinkled micropatterns, with the aim of increasing the contact area and the material's biocompatibility. The main innovation of this study was to include these wrinkled micropatterns on the surface of the scaffold by taking advantage of thin polymer film surface instabilities. On the other hand, salt and nano-hydroxyapatite (nHA) particles were included in the polymeric matrix to create a modified filament for 3D printing. The printed part was leached to eliminate porogen particles, leaving homogenously distributed pores on the structure. The pores have a mean size of 26.4 +/- 9.9 mu m, resulting in a global scaffold porosity of similar to 42% (including pores and microchannels). The presence of nHA particles, which display a homogeneous distribution according to the FE-SEM and EDX results, have a slight influence on the mechanical resistance of the material, but incredibly, despite being a bioactive compound for bone cells, did not show a significant increase in cell viability on the scaffold surface. However, the synergistic effect between the presence of the hydrogel and the pores on the material does produce an increase in cell viability compared to the control sample and the bare PCL material.
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    Thermoresponsive microwrinkled hydrogel surfaces with modulated chemical composition
    (2021) Gonzalez-Henriquez, Carmen M.; Medel-Molina, Gonzalo E.; Rodriguez-Umanzor, Fernando E.; Inostroza, Claudio Terraza; Sarabia-Vallejos, Mauricio A.; Rodriguez-Hernandez, Juan
    Smart wrinkled hydrogel patterns with modulated chemical composition and wrinkle characteristics (amplitude and period) were formed by taking advantage of surface instabilities using a simple, cost-affordable, and robust method. The microstructured surfaces were prepared by dip coating and were designed to be stimuli-responsive by introducing poly(ethylene glycol) methyl ether methacrylate (PEGMEMA) in the initial feed. For this purpose, a silylated substrate surface serves as an anchor for the non-polymerized hydrogel molecules, thus forming a homogenous and reproducible coating. Once the film was achieved, the samples were exposed to vacuum and UV irradiation to form wrinkled patterns spontaneously. The response of the thermosensitive wrinkles reveals significant variations in the properties of the wrinkled films depending on the temperature. In addition to the simplicity, this deposition strategy allows the preparation of highly reproducible films using an easy-scalable methodology with potential interest for industrial applications.
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    Wrinkling on Stimuli-Responsive Functional Polymer Surfaces as a Promising Strategy for the Preparation of Effective Antibacterial/Antibiofouling Surfaces
    (2021) Gonzalez-Henriquez, Carmen M.; Rodriguez-Umanzor, Fernando E.; Alegria-Gomez, Matias N.; Terraza-Inostroza, Claudio A.; Martinez-Campos, Enrique; Cue-Lopez, Raquel; Sarabia-Vallejos, Mauricio A.; Garcia-Herrera, Claudio; Rodriguez-Hernandez, Juan
    Biocompatible smart interfaces play a crucial role in biomedical or tissue engineering applications, where their ability to actively change their conformation or physico-chemical properties permits finely tuning their surface attributes. Polyelectrolytes, such as acrylic acid, are a particular type of smart polymers that present pH responsiveness. This work aims to fabricate stable hydrogel films with reversible pH responsiveness that could spontaneously form wrinkled surface patterns. For this purpose, the photosensitive reaction mixtures were deposited via spin-coating over functionalized glasses. Following vacuum, UV, or either plasma treatments, it is possible to spontaneously form wrinkles, which could increase cell adherence. The pH responsiveness of the material was evaluated, observing an abrupt variation in the film thickness as a function of the environmental pH. Moreover, the presence of the carboxylic acid functional groups at the interface was evidenced by analyzing the adsorption/desorption capacity using methylene blue as a cationic dye model. The results demonstrated that increasing the acrylic acid in the microwrinkled hydrogel effectively improved the adsorption and release capacity and the ability of the carboxylic groups to establish ionic interactions with methylene blue. Finally, the role of the acrylic acid groups and the surface topography (smooth or wrinkled) on the final antibacterial properties were investigated, demonstrating their efficacy against both gram-positive and gram-negative bacteria model strains (E. coli and S. Aureus). According to our findings, microwrinkled hydrogels presented excellent antibacterial properties improving the results obtained for planar (smooth) hydrogels.