Morena Nocchetti

Oleogels containing silica–silver-based nanomaterials were prepared to be used as potential antimicrobial treatment for preventing and curing skin infections. Fumed silica was used as a bifunctional excipient able to offer support to silver-based nanoparticle growth and act as a gelling agent for oleogel formulation. First, silica–silver composites were prepared following a sustainable method by contact of fumed silica and silver nitrate in the presence of ethanol and successive UV irradiation. The composites were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), ATR FT-IR spectroscopy and UV-Vis spectrophotometry. The presence of 8–20 nm spherical nanoparticles, in addition to the silica aggregates and AgNO3 crystals, was detected. The composites showed good antimicrobial activity against the Gram-negative Pseudomonas aeruginosa and the Gram-positive bacteria Staphylococcus aureus and Staphylococcus epidermidis. Thus, they were formulated in an oleogel, obtained using fumed silica as a gelling agent. For comparison, oleogels containing AgNO3 were prepared according to two different formulative techniques. The silica–silver-based oleogels showed good antimicrobial activity and did not show cytotoxic effects for fibroblasts and keratinocytes.

Different amounts of sodium-alendronate (ALN) were loaded into layered zirconium phosphates of alpha and gamma type (αZP and γZP) by means of topotactic exchange reactions of phosphate with ALN. In order to extend the exchange process to the less accessible interlayer regions, ALN solutions were contacted with colloidal dispersions of the layered solids previously exfoliated in single sheets by means of intercalation reaction of propylamine (for αZP) or acetone (for γZP). The ALN loading degree was determined by liquid P-nuclear magnetic resonance (NMR) and inductively coupled plasma (ICP), and it was reported as ALN/Zr molar ratios (Rs). The maximum R obtained for γZP was 0.34, while αZP was able to load a higher amount of ALN, reaching Rs equal to 1. The synthesized compounds were characterized by X-ray powder diffractometry, scanning electron microscopy (SEM), solid-state NMR, and infrared spectroscopy. The way the grafted organo-phosphonate groups were bonded to the layers of the host structure was suggested. The effect of ZP derivatives was assessed on cell proliferation, and the results showed that after 7 days of incubation, none of the samples showed a decrease in cell proliferation.