Gabriela Martínez-Mejía

Hydrogels are 3D networks of hydrophilic crosslinked polymers, which are synthesized from synthetic or natural sources such as chitosan and alginic acid derived from shrimp shell and brown seaweed, respectively. These materials exhibit biodegradability, biocompatibility, and non-cytotoxic properties to be used as scaffolds for tissue engineering applications. In this study, four types of alginic acid hydrogels were chemically synthesized using spermidine as a crosslinking agent with concentrations ranging from 5% (w/w) to 100% (w/w). The results of scanning electron microscopy (SEM) revealed a small average pore size (≤5 μm), while electrospray ionization mass spectrometry (ESI-MASS) and Fourier transform infrared spectroscopy (FT-IR) showed the characteristic vibrations and formed bonds between alginic acid and spermidine, respectively. Finally, the alginic acid hydrogels demonstrated potential ability for tissue regeneration treatments.

Up-conversion nanoparticles (UCNPs) are materials that convert near-infrared (NIR) photons into ultraviolet (UV) or visible emissions. To enhance their optical properties, UCNPs are often synthesized with oxide (Y₂O₃) or fluoride (NaYF₄) support matrices, useful for energy storage applications. In this study, NaYF₄-UCNPs were synthesized via coprecipitation and heat-treated at 400 °C. Then, a tetraethyl orthosilicate (TEOS) film was synthesized by the sol–gel technique at varying pH and temperatures from 25 °C to 80 °C. Characterization using scanning electron microscopy (SEM), X-ray diffraction (XRD), and confocal microscopy (CM) confirmed the up-conversion properties. These materials show promise for enhancing solar radiation density in polymer degradation.

Siderophores are low-molecular-weight chelating agents secreted by microorganisms under iron-limiting conditions, playing a crucial role in metal bioavailability and microbial survival. In this study, siderophores produced by Glutamicibacter sp. strain Al-Teq-24-F2, isolated from plant-associated samples, were characterized through a combination of spectroscopic and analytical methods. ESI-MS analysis of the crude extract revealed several abundant ions between 175 and 800 m/z, suggesting a mixture of secondary metabolites. After chromatographic purification, FT-IR and NMR analyses indicated the presence of amide, hydroxyl, and carboxylate functional groups. Integrating these data allowed for the proposal of a siderophore structure with a molecular weight of 438.25 Da. Thermogravimetric analysis showed thermal stability below 115 °C. During Fe (III) complexation, the zeta potential shifted from −21.15 mV to +42 mV, confirming strong interaction between the ligand and the metal. UV–Vis and fluorescence spectroscopy displayed characteristic bathochromic and hypochromic shifts, together with pronounced fluorescence quenching upon iron binding. These findings provide new insight into the structural and physicochemical properties of siderophores produced by Glutamicibacter sp. and highlight their potential applications in biosensing and metal chelation processes.

Background: Cancer therapeutics development has been a challenge in medical and scientific areas due to their toxicity, limited biocompatibility, and unfortunate side effects. However, despite advances in early detection and the study of novel treatments, the mortality rate for breast cancer remains high, making it a significant global health concern. Objectives: In this study, poly(methyl methacrylate) (PMMA) nanoparticles functionalized with acrylic acid (AA), fumaramide (FA), and curcumin (CUR) as chelating and inhibitor agents were synthesized by emulsion polymerization techniques. Methods and Results: Comprehensive physiochemical characterization studies based on gravimetry, dynamic light scattering (DLS), electrophoresis, Fourier transform infrared (FT-IR), ultraviolet–visible (UV–Vis) and photoluminescence (PL) spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM) revealed a pH dependence of nanoparticles that exhibit structural changes upon interaction with calcium (Ca²⁺) and magnesium (Mg²⁺) ions. Calorimetric thermodynamic properties measured by isothermal titration calorimetry (ITC) confirmed chelating coordination and positive cooperativity between the nanoparticles and metal ions. In vitro studies showed the low cytotoxicity of nanoparticles by fibroblast proliferation, and their chelation process was observed by fluorescence microscopy, with the loss of interaction between cells. Conclusions: These results suggest that the functionalized nanoparticles have potential in drug delivery systems (DDS) for targeted breast cancer therapies, providing a promising polymer material for more efficient and less toxic treatments.

Cancer therapeutics development has been a challenge in medical and scientific areas by their toxicity, biocompatibility and unfortunate side effects on the human body. However, despite advances in early detection and the study of novel treatments, the mortality rate for breast cancer remains high, making it a significant global health concern. Thus, there is still a need for more effective and targeted therapies, where nanotechnology emerges as a promising solution in this field. For this reason, four series of core–shell for breast cancer remains poly(methyl methacrylate, MMA) nanoparticles functionalized with acrylic acid (AA), fumaramide (FA) and curcumin (CUR) as chelating agents were synthesized by emulsion polymerization techniques. Comprehensive physiochemical characterization studies based on gravimetry, dynamic light scattering (DLS), electrophoresis, Fourier transform infrared (FT-IR), ultraviolet-visible (UV-Vis) and photoluminescence (PL) spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM) were made to analyze their pH-dependence. The calorimetric thermodynamic properties of interaction between the particles and calcium chloride (CaCl2) or magnesium chloride (MgCl2) solutions were evaluated by isothermal titration calorimetry (ITC). Among the most relevant results were that nanoparticles showed a strong pH-dependence by underwent structural changes when they interacted with calcium (Ca2+) and magnesium (Mg2+) ions. Furthermore, the interaction parameters such as intermolecular forces, binding constant (Kb), interaction enthalpies (H), and Gibbs free energy (G) confirmed a strong coordination bond between the functional groups and the metal ions. According to obtained results, nanoparticles could have the ability to chelate ions available in the medium, suggesting their potential use in improving drug delivery systems (DDS) for breast cancer therapies.

Polymeric composite solutions (PCSs) reinforced with carbon nanotubes sponges (CNT-sponges) have attracted interest in material science and engineering due to their physicochemical properties. Understanding the influence of CNT-sponges content (0.1 wt.%, 0.3 wt.% and 0.5 wt.%) on rheological behavior of poly(styrene-co-acrylonitrile) P(S:AN) (0:100, 20:80, 40:60 and 50:50, wt.%:wt.%) solutions synthesized by emulsion polymerization can predict the viscoelastic parameters for their possible application in electrospinning processes. The obtained nanofibers can be used as sensors, textiles, purifying agents or artificial muscles and tissues. For this, amplitude and frequency sweeps were performed to measure the viscosity (η), storage (G’) and loss (G”) moduli and loss factor (tan δ). Most PCSs showed a shear thinning behavior over the viscosity range of 0.8 < η/Pa·s < 20. At low CNT-sponges concentration in the polymer matrix, the obtained loss factor indicated a liquid-like behavior, while as CNT-sponges content increases, the solid-like behavior predominated. Then, the polymeric solutions were successfully electrospun; however, some agglomerations were formed in materials containing 0.5 wt.% of CNT-sponges attributed to the interaction forces generated within the structure. Finally, the rheological analysis indicates that the PCS with a low percentage of CNT-sponges are highly suitable to be electrospun.

The influence of carbon nanotubes sponges (CNT–sponges) content at 0.1 wt.%, 0.3 wt.% and 0.5 wt.% on rheological properties of three series of polymeric solutions of poly (styrene-co-acrylonitrile) P(S:AN) was evaluated. For that, amplitude and frequency sweeps were made in order to determine the storage (G’) and loss (G’’) moduli, loss factor (tan δ), structural changes and homogeneity of polymeric composite solutions as function of polymeric content P(S:AN) 0:100, 20:80, 40:60 and 50:50 wt%:wt%. For polymeric composite solutions (PCS) of pristine polyacrylonitrile, the rheological measurements show a Newtonian behavior at low shear rates and non-Newtonian behavior at higher values, meanwhile, all copolymeric PCS perform a non-Newtonian (shear thinning) behavior with a viscosity range of 0.8 < η /Pa·s < 20. The loss factor indicates a liquid-like behavior for solutions with 0.1 wt.% and 0.3 wt.% of CNT–sponges content, meanwhile a solid-like behavior was observed for 0.5 wt.% concentration. Finally, the polymeric composite solutions were processed in an electrospinning system to obtain fibers and were analyzed by SEM technique, CNT-sponges agglomerations were found into fibers with 0.5 wt.% content. The aim of this rheological analysis was carried out to predict the viscoelastic parameters and the suitability of solutions to electrospun process.