RESUMO
In the past decade, hydrogels have attracted growing interest for emerging applications in flexible electronic devices, human-machine interactions, energy supply, or energy storage. Developing a multifunctional gel architecture with superior ionic conductivity and good mechanical flexibility is a bottleneck to overcome. Herein, poly(vinyl alcohol)/sulfuric acid (PVA-H2SO4) hydrogels were prepared via a freeze-thaw method. With the aim of tuning the formulation in view of a possible application in energy storage, the effects of different combinations in terms of the molecular weight (MW) of PVA and PVA-H2SO4 weight ratio were investigated. Moreover, exploiting the self-healing properties of these hydrogels and the easy possibility of functionalizing them, i.e., introducing a conducting polymer such as poly(2-acrylamido-2-methyl-1-propane) sulfonic acid doped polyaniline (PANI_PAMPSA), a sandwiched all-in-one double-layer hydrogel (electrode/electrolyte configuration) was prepared (PVA-H2SO4-PANI_PAMPSA/PVA-H2SO4). Results showed that the water content is independent of the PVA amount and MW; the polymer concentration has a significant effect on the formation of crystalline domains and therefore on swelling degree, whereas the cross-linking degree depends on the MW. The PVA MW has the maximum effect on the swelling percentage normalized with respect to the polymer fraction and the tensile properties of the hydrogel. The assembled all-in-one electrode/electrolyte shows promising ionic conductivity (439.7 mS cm-1) and specific capacitance performance (0.297 mF cm-2 at a current density of 0.025 mA cm-2), as well as excellent flexibility and considerable self-healing properties. These results will promote the development of self-healing symmetrical supercapacitors for storage devices in wearable electronics.
RESUMO
Metal-organic frameworks (MOFs) are a class of crystalline porous materials with outstanding physical and chemical properties that make them suitable candidates in many fields, such as catalysis, sensing, energy production, and drug delivery. By combining MOFs with polymeric substrates, advanced functional materials are devised with excellent potential for biomedical applications. In this research, Zeolitic Imidazolate Framework 8 (ZIF-8), a zinc-based MOF, was selected together with cellulose, an almost inexhaustible polymeric raw material produced by nature, to prepare cellulose/ZIF-8 composite flat sheets via an in-situ growing single-step method in aqueous media. The composite materials were characterized by several techniques (IR, XRD, SEM, TGA, ICP, and BET) and their antibacterial activity as well as their biocompatibility in a mammalian model system were investigated. The cellulose/ZIF-8 samples remarkably inhibited the growth of Gram-positive and Gram-negative reference strains, and, notably, they proved to be effective against clinical isolates of Staphylococcus epidermidis and Pseudomonas aeruginosa presenting different antibiotic resistance profiles. As these pathogens are of primary importance in skin diseases and in the delayed healing of wounds, and the cellulose/ZIF-8 composites met the requirements of biological safety, the herein materials reveal a great potential for use as gauze pads in the management of wound infections.
RESUMO
The development of green, low cost and sustainable synthetic routes to produce metal nanoparticles is of outmost importance, as these materials fulfill large scale applications in a number of different areas. Herein, snail slime extracted from Helix Aspersa snails was successfully employed both as bio-reducing agent of silver nitrate and as bio-stabilizer of the obtained nanoparticles. Several trials were carried out by varying temperature, the volume of snail slime and the silver nitrate concentration to find the best biogenic pathway to produce silver nanoparticles. The best results were obtained when the synthesis was performed at room temperature and neutral pH. UV-Visible Spectroscopy, SEM-TEM and FTIR were used for a detailed characterization of the nanoparticles. The obtained nanoparticles are spherical, with mean diameters measured from TEM images ranging from 15 to 30 nm and stable over time. The role of proteins and glycoproteins in the biogenic production of silver nanoparticles was elucidated. Infrared spectra clearly showed the presence of proteins all around the silver core. The macromolecular shell is also responsible of the effectiveness of the synthesized AgNPs to inhibit Gram positive and Gram negative bacterial growth.
RESUMO
Percutaneous devices are extensively used in modern medicine therapies, even in long term applications. Complications from their use, related to bacterial colonization and/or to materials thrombogenicity, may result in a significant morbidity and mortality incidence. In this study, a novel polycarbonate-urethane (PCU), incorporating a tailor-made diamino-diamide-diol (PIME) showing the ability to bind heparin at physiological pH, was compared to commercial medical-grade PCUs (Carbothane and Bionate). Mechanical and thermal properties were evaluated by tensile tests, dynamic mechanical analysis and differential scanning calorimetry. The presence of a low amount of PIME chain extender in Bionate polyurethanes (Bionate-PIME) slightly affects the mechanical properties, remaining however comparable with the medical grade PCUs used for the fabrication of cardiovascular devices. To verify thereof heparin surface adsorbed in disfavouring bacterial colonization, heparinized Bionate-PIME was tested for bacterial adhesion, using Bionate and Carbothane as reference. In vitro bacterial interaction tests were performed with the strains mainly involved in the pathogenesis of device-related infections (S. epidermidis and S. aureus). MTT tests and SEM observations showed a decrease in colonization of the different strains on the heparinized Bionate-PIME surfaces, confirming that preadsorbed heparin plays a role in mediating the biomaterial surface/bacterial cells interactions.
