Maria Bastianini

Ag/AgCl nanoparticle decorated layered double hydroxides: synthesis, characterization and antimicrobial properties

A layered double hydroxide (LDH) surface was employed as a substrate for growing silver nanoparticles (NPs). An efficient method to produce stable silver/silver chloride nanoparticles supported on the ZnAl-LDH surface was developed. NPs of AgCl were grown on the ZnAl-LDH surface by using AgNO3 as the silver source. The ZnAl-LDH in chloride form acts as a nucleating agent, and depending on the pH of the LDH dispersion, AgClNPs with different dimensions were obtained. In particular AgClNPs with a diameter of 60 nm were formed at pH 5. The AgClNPs supported on LDH sheets were partially reduced by different reducing agents (NaBH4 and formaldehyde) resulting in a Ag/AgCl-LDH nanocomposite. The silver chloride and silver NP dimensions were evaluated by X-ray powder diffraction, field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). UV-Vis spectra of the samples upon reduction showed a band centred at 415 nm due to the surface plasmon resonance of silver nanoparticles with a diameter of about 10 nm, in agreement with the TEM analysis. The AgCl-LDH and Ag/AgCl-LDH nanocomposites, subjected to antimicrobial tests, exhibited good antimicrobial activity against both Gram-negative (Pseudomonas aeruginosa) and Gram-positive (Staphylococcus epidermidis and S. aureus) bacteria and yeast (Candida albicans). The nanocomposites were also studied for their ability to release silver by obtaining release curves, under conditions of antibacterial assays. Finally, the nanocomposites antibacterial behavior, as a function of time, was investigated by performing time-kill experiments using S. aureus and Candida albicans.

On the Intercalation of the Iodine−Iodide Couple on Layered Double Hydroxides with Different Particle Sizes

Molecular iodine was intercalated from nonaqueous solution into microsized ZnAl-layered double hydroxide (LDH) in the iodide form, generating the I(3)(-)/I(-) redox couple into the interlayer region. Chloroform, ethanol, acetonitrile, or diethyl ether were used as solvents to dissolve the molecular iodine. The intercalation compounds were characterized by thermogravimetric analysis, X-ray powder diffraction, UV-vis spectroscopy, and scanning and transmission electron microscopy. The stability of iodine-solvent adducts and the iodine concentration affected the LDH iodine loading, and samples with I(2)/I(-) molar ratio ranging from 0.14 to 0.82 were prepared. Nanosized, well dispersible LDH, synthesized by the urea method in water-ethylene glycol media, were also prepared and successfully functionalized with the I(3)(-)/I(-) redox couple applying the conditions optimized for the micrometric systems.

Hydrotalcite composites for an effective fluoride buccal administration: a new technological approach.

The aim of this work was to develop new mucoadhesive buccal patches containing an inorganic fluorinated compound, MgAl-F, intended for decay prevention. Firstly MgAl-F was synthesized and characterized, then the patches were prepared starting from a physical blend of mucoadhesive polymers (NaCMC and polycarbophil) in which MgAl-F was dispersed in different amounts in order to obtain the films. The prepared mucoadhesive patches were characterized in terms of swelling capacity, mucoadhesion force and time, surface morphology and in vitro release studies. Moreover, the organoleptic properties and acceptability have been evaluated by in vivo application. The performed studies demonstrated that the proposed formulations are practical, manageable, flexible and adaptable to the biological substrate showing, at the same time, good organoleptic properties. Moreover, the presence of the MgAl-F is able to decrease the strong adhesion of the employed polymers, reducing pain and irritations resulting in a high patient acceptability. Data obtained from release studies revealed that the application of small patch portions is enough able to release, for a prolonged time, an amount of fluoride ions able to reach the efficacious dose. These observations suggest the applicability of such formulations for buccal administration of different active ingredients.