Silver Nanoparticles: Multifunctional Tool in Environmental Water Remediation.

Water pollution is a worldwide environmental and health problem that requires the development of sustainable, efficient, and accessible technologies. Nanotechnology is a very attractive alternative in environmental remediation processes due to the multiple properties that are conferred on a material when it is at the nanometric scale. This present review focuses on the understanding of the structure-physicochemical properties-performance relationships of silver nanoparticles, with the objective of guiding the selection of physicochemical properties that promote greater performance and are key factors in their use as antibacterial agents, surface modifiers, colorimetric sensors, signal amplifiers, and plasmonic photocatalysts. Silver nanoparticles with a size of less than 10 nm, morphology with a high percentage of reactive facets {111}, and positive surface charge improve the interaction of the nanoparticles with bacterial cells and induce a greater antibacterial effect. Adsorbent materials functionalized with an optimal concentration of silver nanoparticles increase their contact area and enhance adsorbent capacity. The use of stabilizing agents in silver nanoparticles promotes selective adsorption of contaminants by modifying the surface charge and type of active sites in an adsorbent material, in addition to inducing selective complexation and providing stability in their use as colorimetric sensors. Silver nanoparticles with complex morphologies allow the formation of hot spots or chemical or electromagnetic bonds between substrate and analyte, promoting a greater amplification factor. Controlled doping with nanoparticles in photocatalytic materials produces improvements in their electronic structural properties, promotes changes in charge transfer and bandgap, and improves and expands their photocatalytic properties. Silver nanoparticles have potential use as a tool in water remediation, where by selecting appropriate physicochemical properties for each application, their performance and efficiency are improved.

Cell behavior on silica-hydroxyapatite coaxial composite.

Progress in the manufacture of scaffolds in tissue engineering lies in the successful combination of materials such as bioceramics having properties as porosity, biocompatibility, water retention, protein adsorption, mechanical strength and biomineralization. Hydroxyapatite (HA) is a ceramic material with lots of potential in tissue regeneration, however, its structural characteristics need to be improved for better performance. In this study, silica-hydroxyapatite (SiO2-HA) non-woven ceramic electrospunned membranes were prepared through the sol-gel method. Infrared spectra, scanning electron microscopy and XRD confirmed the structure and composition of composite. The obtained SiO2-HA polymeric fibers had approximately 230±20 nm in diameter and were then sintered at 800°C average diameter decreased to 110±17 nm. Three configurations of the membranes were obtained and tested in vitro, showing that the composite of SiO2-HA fibers showed a high percentage of viability on a fibroblast cell line. It is concluded that the fibers of SiO2-HA set in a coaxial configuration may be helpful to develop materials for bone regeneration.

Preliminary Biocompatibility Tests of Poly-ε-Caprolactone/Silver Nanofibers in Wistar Rats.

Currently, nanotechnology is perceived as a promising science that produces materials with diverse unique properties at a nanometric scale. Biocompatibility tests of poly-ε-caprolactone nanofibers, embedded with silver nanoparticles manufactured by means of the electrospinning technique, were carried out in Wistar rats to be used as oral dressings for the eradication of bacteria. Solutions of 12.5, 25, 50 and 100 mM of silver nitrate were made using N-dimethylformamide (DMF) and tetrahydrofuran (THF) as reducing solvents with 8% of poly-ε-caprolactone (PCL) polymer. The solutions were electrospun, and the nanofibers obtained in the process were characterized by infrared spectroscopy, Raman spectroscopy, dark field optical microscopy, scanning electron microscopy and X-ray scattering spectroscopy. The nanofibers had an average diameter of 400 ± 100 nm. Once the characterization of the material was done, three implants of each concentration of the nanofibers were formed and placed in the subcutaneous tissue of the rats. Three experimental subjects were used, leaving the material in them for a length of two, four and six weeks, respectively. The rats showed good healing, with the lesions completely healed at four weeks after implantation. After that time, biopsies were taken, and histopathological sections were made to evaluate the inflammatory infiltrate. The tissues of the rats presented chronic inflammatory infiltrate composed mainly of lymphocytes and giant multinucleated cells. The material was rejected by the rats when a layer of collagen and fibroblasts was produced, coating the material, a process characteristic of a foreign body reaction.