RESUMEN

As the global urgency for effective antimicrobial agents intensifies, this work harnesses the widely demonstrated antimicrobial activity of silver nanoparticles (Ag-NPs) and proposes alternative synthesis approaches to metal-organic hybrid systems with antimicrobial activity. In this study, the proposed synthesis route involves decorating metallic nanoparticles into organic substrates without previous doping. The synthesis simultaneously uses polyethylene glycol for three crucial purposes: (1) acting as a mild reducing agent to generate Ag-NPs with a spherical shape and diameters ranging from 10 to just over 20 nm, (2) functioning as a dispersing agent for flakes of commercial nanostructured carbon supports, including reduced graphene oxide (rGO, ID-nano), and commercial carbon nanoplatelets from Sigma-Aldrich (GNPs, Sigma-Aldrich), and (3) serving as a promoter for the homogeneous anchoring of Ag-NPs in the carbon lattice without altering the conformation of the carbon lattice. This intricate interaction involves the π-orbitals from the sp2 hybridization honeycomb and the d-orbitals from the Ag-NPs, leading to the constructive rehybridization of rGO and GNPs. In our study, Ag-NPs/rGO are compared with a support lacking oxygenated groups in the lattice, such as commercial GNPs (Sigma-Aldrich), to produce Ag-NPs/GNPs. This comparison maintains constructive sp2 rehybridization, preserving the characteristic properties of rGO (ID-nano) and graphene nanoplatelets, including commercial GNPs (Sigma-Aldrich). Notably, oxygenated groups from rGO exhibit greater availability for exchanging oxo and hydroxy defects for Ag-NPs compared with GNPs (Sigma-Aldrich). The resulting Ag-NPs/rGO and Ag-NPs/GNP systems are thoroughly physicochemically characterized, employing techniques such as Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy, high-resolution transmission electron microscopy, and scanning transmission electron microscopy, revealing the successful integration of Ag-NPs with minimal alteration to the carbon lattice. Subsequent antimicrobial evaluation against Escherichia coli (E. coli) demonstrates significant activity, with Ag-NPs/rGO and Ag-NPs/GNPs registering similar minimum inhibitory concentrations of 50 µg mL-1. This study underscores the potential of our metal-organic hybrid systems as antimicrobial agents and provides insights into the constructive rehybridization process, paving the way for diverse applications in the biomedical and environmental fields.

RESUMEN

Bismuth titanate (BTO) nanoparticles were obtained by pulsed laser ablation in liquid media (PLAL). Distilled water, ethanol, isopropanol, and acetone were used as media for laser ablation experiments, in which the colloidal solutions were obtained. Laser ablation was carried out using the second harmonic and fundamental wavelength of a pulsed Nd:YAG laser (532 nm and 1064 nm, respectively) with laser fluences of 25 and 12 mJ/cm2, respectively. Transmission electron microscopy was utilized for morphological characterization. BTO nanoparticles obtained have spherical shapes with orthorhombic structure and the average size distribution depended on the liquid media nature. In alcohols, BTO NPs were spherical with a carbon layer around them. X-ray diffraction, UV-Vis absorption spectra, and X-ray photoelectron spectroscopy were used to confirm the structural, optical, and elemental properties of the ablated products. The presented results show that PLAL is a viable technique for the synthesis of high-quality BTO nanoparticles with enhanced optical properties for possible applications in photocatalysis.

RESUMEN

Biopolymer microgels present many opportunities in biomedicine and tissue engineering. To understand their in vivo behavior in therapeutic interventions, long-term monitoring is critical, which is usually achieved by incorporating fluorescent materials within the hydrogel matrix. Current research is limited due to issues concerning the biocompatibility and instability of the conventional fluorescent species, which also tend to adversely affect the bio-functionality of the hydrogels. Here, we introduce a microfluidic-based approach to generate nitrogen-functionalized graphene quantum dot (NGQD) incorporated gelatin methacryloyl (GelMA) hydrogel microspheres, capable of long-term monitoring while preserving or enhancing the other favorable features of 3D cell encapsulation. A multilayer droplet-based microfluidic device was designed and fabricated to make monodisperse NGQD-loaded GelMA hydrogel microspheres encapsulating skeletal muscle cells (C2C12). Control over the sizes of microspheres could be achieved by tuning the flow rates in the microfluidic device. Skeletal muscle cells encapsulated in these microgels exhibited high cell viability from day 1 (82.9 ± 6.50%) to day 10 (92.1 ± 3.90%). The NGQD-loaded GelMA microgels encapsulating the cells demonstrated higher metabolic activity compared to the GelMA microgels. Presence of sarcomeric α-actin was verified by immunofluorescence staining on day 10. A fluorescence signal was observed from the NGQD-loaded microgels during the entire period of the study. The investigation reveals the advantages of integrating NGQDs in microgels for non-invasive imaging and monitoring of cell-laden microspheres and presents new opportunities for future therapeutic applications.

Asunto(s)

Grafito , Microgeles , Puntos Cuánticos , Ingeniería de Tejidos , Hidrogeles , Gelatina , Metacrilatos

RESUMEN

Phase transition issues in the field of foods and drugs have significantly influenced these industries and consequently attracted the attention of scientists and engineers. The study of thermodynamic parameters such as the glass transition temperature (Tg), melting temperature (Tm), crystallization temperature (Tc), enthalpy (H), and heat capacity (Cp) may provide important information that can be used in the development of new products and improvement of those already in the market. The techniques most commonly employed for characterizing phase transitions are thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), thermomechanical analysis (TMA), and differential scanning calorimetry (DSC). Among these techniques, DSC is preferred because it allows the detection of transitions in a wide range of temperatures (-90 to 550 °C) and ease in the quantitative and qualitative analysis of the transitions. However, the standard DSC still presents some limitations that may reduce the accuracy and precision of measurements. The modulated differential scanning calorimetry (MDSC) has overcome some of these issues by employing sinusoidally modulated heating rates, which are used to determine the heat capacity. Another variant of the MDSC is the supercooling MDSC (SMDSC). SMDSC allows the detection of more complex thermal events such as solid-solid (Ts-s) transitions, liquid-liquid (Tl-l) transitions, and vitrification and devitrification temperatures (Tv and Tdv, respectively), which are typically found at the supercooling temperatures (Tco). The main advantage of MDSC relies on the accurate detection of complex transitions and the possibility of distinguishing reversible events (dependent on the heat capacity) from non-reversible events (dependent on kinetics).