A New Water-Soluble Bactericidal Agent for the Treatment of Infections Caused by Gram-Positive and Gram-Negative Bacterial Strains.

Grapefruit and lemon pectin obtained from the respective waste citrus peels via hydrodynamic cavitation in water only are powerful, broad-scope antimicrobials against Gram-negative and -positive bacteria. Dubbed IntegroPectin, these pectic polymers functionalized with citrus flavonoids and terpenes show superior antimicrobial activity when compared to commercial citrus pectin. Similar to commercial pectin, lemon IntegroPectin determined ca. 3-log reduction in Staphylococcus aureus cells, while an enhanced activity of commercial citrus pectin was detected in the case of Pseudomonas aeruginosa cells with a minimal bactericidal concentration (MBC) of 15 mg mL-1. Although grapefruit and lemon IntegroPectin share equal MBC in the case of P. aeruginosa cells, grapefruit IntegroPectin shows boosted activity upon exposure of S. aureus cells with a 40 mg mL-1 biopolymer concentration affording complete killing of the bacterial cells. Insights into the mechanism of action of these biocompatible antimicrobials and their effect on bacterial cells, at the morphological level, were obtained indirectly through Fourier Transform Infrared spectroscopy and directly through scanning electron microscopy. In the era of antimicrobial resistance, these results are of great societal and sanitary relevance since citrus IntegroPectin biomaterials are also devoid of cytotoxic activity, as already shown for lemon IntegroPectin, opening the route to the development of new medical treatments of polymicrobial infections unlikely to develop drug resistance.

Chromium liquid waste inertization in an inorganic alkali activated matrix: leaching and NMR multinuclear approach.

A class of inorganic binders, also known as geopolymers, can be obtained by alkali activation of aluminosilicate powders at room temperature. The process is affected by many parameters (curing time, curing temperature, relative humidity etc.) and leads to a resistant matrix usable for inertization of hazardous waste. In this study an industrial liquid waste containing a high amount of chromium (≈ 2.3 wt%) in the form of metalorganic salts is inertized into a metakaolin based geopolymer matrix. One of the innovative aspects is the exploitation of the water contained in the waste for the geopolymerization process. This avoided any drying treatment, a common step in the management of liquid hazardous waste. The evolution of the process--from the precursor dissolution to the final geopolymer matrix hardening--of different geopolymers containing a waste amount ranging from 3 to 20%wt and their capability to inertize chromium cations were studied by: i) the leaching tests, according to the EN 12,457 regulation, at different curing times (15, 28, 90 and 540 days) monitoring releases of chromium ions (Cr(III) and Cr(VI)) and the cations constituting the aluminosilicate matrix (Na, Si, Al); ii) the humidity variation for different curing times (15 and 540 days); iii) SEM characterization at different curing times (28 and 540 days); iv) the trend of the solution conductivity and pH during the leaching test; v) the characterization of the short-range ordering in terms of TOT bonds (where T is Al or Si) by (29)Si and (27)Al solid state magic-angle spinning nuclear magnetic resonance (ss MAS NMR) for geopolymers containing high amounts of waste (10-20%wt). The results show the formation of a stable matrix after only 15 days independently on the waste amount introduced; the longer curing times increase the matrices stabilities and their ability to immobilize chromium cations. The maximum amount of waste that can be inertized is around 10 wt% after a curing time of 28 days.

Preparation of Nd:YAG nanopowder in a confined environment.

Nanopowder of yttrium aluminum garnet (YAG, Y3Al5O12) doped with neodymium ions (Nd:YAG) was prepared in the water/cetyltrimethylammonium bromide/1-butanol/n-heptane system. Aluminum, yttrium, and neodymium nitrates were used as starting materials, and ammonia was used as a precipitating agent. Coprecipitate hydroxide precursors where thermally treated at 900 degrees C to achieve the garnet phase. The starting system with and without reactants was characterized by means of the small-angle neutron scattering technique. The system, without reactants, is constituted by a bicontinuous structure laying near the borderline with the lamellar phase region. The introduction of nitrates stabilizes the bicontinuous structure, while the presence of ammonia induces a transformation from the bicontinuous phase to a lamellar phase. Nd:YAG nanopowder was characterized by wide-angle X-ray scattering, transmission electron microscopy, gas adsorption, and photoluminescence spectroscopy. By comparison with a sample prepared by the conventional coprecipitation method, the obtained Nd:YAG nanopowder is constituted by smaller crystalline nanoparticles showing a lower tendency to agglomerate. In addition, the nanoparticles present a well-defined spherical shape. Photoluminescence spectroscopy confirms that the doping Nd3+ ions substitute Y3+ ions in the YAG crystalline lattice. The Nd3+ lifetime value, obtained from the luminescence decay curves, was 286 +/- 10 micros, higher than the single-crystal value (255 micros) and much higher than the nanopowder value obtained by the conventional coprecipitation method (75 micros).

Microwave-assisted synthesis of anhydrous CdS nanoparticles in a water-oil microemulsion.

Microwave irradiation at a frequency of 2.45 GHz and a power ranging between 22 and 30 W was used, in a water-oil microemulsion at 35+/-2 degrees C, to obtain stable, small, crystalline, anhydrous CdS nanoparticles exhibiting enhanced luminescence properties. The process of nanoparticles growth at different irradiation times was followed by UV-vis spectroscopy. It was observed that irradiated nanoparticles grew faster and their size reached a constant value. The final mean nanoparticle diameter was 2.7 nm, smaller than that observed in a non-irradiated sample, in which particle dimensions slowly increased even after 10 h. This finding was confirmed by high resolution transmission electron microscopy which also suggested that the spherical nanoparticles had a narrow size distribution and were spatially well separated. Furthermore, Fourier transform infrared spectroscopy was used to obtain information about structural changes that the microemulsion underwent when irradiated by microwaves. In particular, the evolution of the stretching and bending bands of water molecules along with the CO and SO3 stretching bands of the surfactant molecules, showed that water was selectively and almost completely extracted from the aqueous core of the reversed micelles. Changes in the surroundings of the nanoparticles surface were monitored by photoluminescence spectroscopy and variations in the emission band profiles indicated enhanced luminescence properties. The latter finding, as well as the inhibition of the nanoparticles growth process, are attributable to the progressive reduction of water content in the core of the reversed micelles.