Browsing by Author "Diaz Diaz, David"

Now showing 1 - 7 of 7
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    Biohydrogel Based on Dynamic Covalent Bonds for Wound Healing Applications
    (2021) Agubata, Chukwuma O.; Mbaoji, Cynthia C.; Nzekwe, Ifeanyi T.; Saldias, Cesar; Diaz Diaz, David
    In this work, a biohydrogel based on alginate and dynamic covalent B-O bonds, and derived composites, has been evaluated for wound healing applications. In particular, a phenylboronic acid-alginate (PBA-Alg) complex was synthesized by coupling 3-aminophenylboronic acid onto alginate, and used to prepare varied concentrations of hydrogels and silicate-based nanocomposites in PBS. The resulting hydrogels were characterized in terms of interfacial tension, moisture uptake and loss, interaction with fresh acid-soluble collagen, self-healing ability, effects on blood clotting and wound healing. The interfacial tension between the hydrogels and biorelevant fluids was low and moisture loss of 55-60% was evident without uptake from the environment. The components of the hydrogels and their mixtures with collagen were found to be compatible. These hydrogels showed efficient self-healing and thixotropic behavior, and the animals in the treatment groups displayed blood clotting times between 9.1 min and 10.7 min. In contrast, the composites showed much longer or shorter clotting times depending on the silicate content. A significant improvement in wound healing was observed in 3% w/v PBA-Alg formulations. Overall, the PBA-Alg hydrogels exhibit self-healing dynamic covalent interactions and may be useful in dressings for incision wounds.
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    Chromophoric Dendrimer-Based Materials: An Overview of Holistic-Integrated Molecular Systems for Fluorescence Resonance Energy Transfer (FRET) Phenomenon
    (2021) Bonardd, Sebastian; Diaz Diaz, David; Leiva, Angel; Saldias, Cesar
    Dendrimers (from the Greek dendros -> tree; meros -> part) are macromolecules with well-defined three-dimensional and tree-like structures. Remarkably, this hyperbranched architecture is one of the most ubiquitous, prolific, and recognizable natural patterns observed in nature. The rational design and the synthesis of highly functionalized architectures have been motivated by the need to mimic synthetic and natural-light-induced energy processes. Dendrimers offer an attractive material scaffold to generate innovative, technological, and functional materials because they provide a high amount of peripherally functional groups and void nanoreservoirs. Therefore, dendrimers emerge as excellent candidates since they can play a highly relevant role as unimolecular reactors at the nanoscale, acting as versatile and sophisticated entities. In particular, they can play a key role in the properties of light-energy harvesting and non-radiative energy transfer, allowing them to function as a whole unit. Remarkably, it is possible to promote the occurrence of the FRET phenomenon to concentrate the absorbed energy in photoactive centers. Finally, we think an in-depth understanding of this mechanism allows for diverse and prolific technological applications, such as imaging, biomedical therapy, and the conversion and storage of light energy, among others.
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    CuAu bimetallic plasmonic-enhanced catalysts supported on alginate biohydrogels
    (2022) Ramirez, Oscar; Bonardd, Sebastian; Saldias, Cesar; Zambrano, Yadira; Diaz Diaz, David; Leiva, Angel
    We describe the synthesis, characterization and catalytic properties of a series of hybrid materials composed of inorganic plasmonic mono-and bimetallic nanoparticles supported on organic bio-based hydrogel beads. The bimetallic materials showed a localized surface plasmon resonance in the visible region, with a maximum light absorption correlated to the metal composition of the alloyed systems. Thermogravimetric analysis revealed a total water content near to 90 % w/w, which was in good agreement with the free-volume calculated from mu CT scan reconstruction of lyophilized samples. Catalytic essays for the reduction of 4-nitrophenol demonstrated that alginate beads loaded with bimetallic nanoparticles exhibit a 5.4-fold higher apparent kinetic constant (k(app)) than its monometallic counterparts. Additionally, taking advantage of the plasmonic properties given by the nanoparticles is that the materials were tested as photocatalysts. The activity of the catalysts was enhanced by near 2.2 times higher in comparison with its performance in dark conditions.
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    Molecular Weight Enables Fine-Tuning the Thermal and Dielectric Properties of Polymethacrylates Bearing Sulfonyl and Nitrile Groups as Dipolar Entities
    (2021) Bonardd, Sebastian; Saldias, Cesar; Leiva, Angel; Diaz Diaz, David; Kortaberria, Galder
    In this work, polymethacrylates containing sulfonyl and nitrile functional groups were successfully prepared by conventional radical polymerization and reversible addition-fragmentation chain-transfer polymerization (RAFT). The thermal and dielectric properties were evaluated, for the first time, considering differences in their molecular weights and dispersity values. Variations of the aforementioned properties do not seem to substantially affect the polarized state of these materials, defined in terms of the parameters epsilon'(r), epsilon"(r) and tan (delta). However, the earlier appearance of dissipative phenomena on the temperature scale for materials with lower molecular weights or broader molecular weight distributions, narrows the range of working temperatures in which they exhibit high dielectric constants along with low loss factors. Notwithstanding the above, as all polymers showed, at room temperature, epsilon'(r) values above 9 and loss factors below 0.02, presenting higher dielectric performance when compared to conventional polymer materials, they could be considered as good candidates for energy storage applications.
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    Polymer topology-controlled self-healing properties of polyelectrolyte hydrogels based on DABCO-containing aromatic ionenes
    (2019) Haering, Marleen; Grijalvo, Santiago; Haldar, Debasish; Saldias, Cesar; Diaz Diaz, David
    DABCO-containing polymers based on a disubstituted phenylene dibenzamide core constitute versatile gelators enabling the formation of hydrogels for different applications. In this work we have found that the polymer topology, controlled by the disubstitution pattern of the aromatic core, plays a crucial role on the self-healing properties of the corresponding hydrogels. Specifically, the ortho-isomer showed very superior shape persistent, self-standing and self-healing properties compared to its meta - and pare-analogues. Interestingly, the healing process occurred without the need of involving oppositely charged species.
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    Sulfonamide as amide isostere for fine-tuning the gelation properties of physical gels
    (2020) Alegre-Requena, Juan, V; Grijalvo, Santiago; Sampedro, Diego; Mayr, Judith; Saldias, Cesar; Juan Marrero-Tellado, Jose; Eritja, Ramon; Herrera, Raquel P.; Diaz Diaz, David
    (S)-2-Stearamidopentanedioic acid (C-18-Glu) is a known LMW gelator that forms supramolecular gels in a variety of solvents. In this work, we have carried out the isosteric substitution of the amide group by a sulfonamide moiety yielding the new isosteric gelator (S)-2-(octadecylsulfonamido)pentanedioic acid (Sulfo-Glu). The gelation ability and the key properties of the corresponding gels were compared in terms of gelation concentration, gel-to-sol transition temperature, mechanical properties, morphology, and gelation kinetics in several organic solvents and water. This comparison was also extended to (S)-2-(4-hexadecyl-1H-1,2,3-triazol-4-yl)pentanedioic acid (Click-Glu), which also constitutes an isostere of C-18-Glu. The stabilizing interactions were explored through computational calculations. In general, Sulfo-Glu enabled the formation of non-toxic gels at lower concentrations, faster, and with higher thermal-mechanical stabilities than those obtained with the other isosteres in most solvents. Furthermore, the amide-sulfonamide isosteric substitution also influenced the morphology of the gel networks as well as the release rate of an embedded antibiotic (vancomycin) leading to antibacterial activity in vitro against Staphylococcus aureus.
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    Visible-Light-Triggered Degradation of pH-Responsive Micelles Based on ortho-Hydroxy Cinnamates
    (2022) Abramov, Alex; Bonardd, Sebastian; Saldias, Cesar; Diaz Diaz, David
    Micelles made by connecting hydrophobic and hydrophilic chains via photo-responsive ortho-hydroxy cinnamate (oHC) units undergo complete degradation within 10 min under visible light irradiation at basic pH values. This proof of concept relies on the controlled cyclization of the oHC moiety affording the corresponding coumarin with the concomitant separation of the hydrophobic portion. Furthermore, the neat polymeric micelles are stable under daylight conditions, thus allowing its storage without special precautions at neutral pH. The amphiphilic nature of mPEG(750)-oHC-dociecyl, expressed as the ability to self-assemble into micellar aggregates in aqueous media, was corroborated by the measurement of its critical micellar concentration (CMC) by fluorescence analysis, as well as the successful visualization of these aggregates using transmission electron microscopy (TEM). Moreover, the size distribution and suspension stability of these aggregates obtained at different pH values was analyzed in terms of dynamic light scattering (DLS) and zeta potential measurements.