The flavonoid quercetin is extensively studied for its antioxidant and chemopreventive properties.However the poor water-solubility, low stability and short half-life could restrict its use in skin care products and therapy.The present study is aimed to evaluate the potential of aminopropyl functionalized mesoporous silica nanoparticles (NH 2 -MSN) as topical carrier system for quercetin delivery. Thermo gravimetric analysis, X-ray diffraction, high resolution transmission electron microscopy, nitrogen adsorption isotherms, FT-IR spectroscopy, zeta potential measurements and differential scanning calorimetry allowed analyzing with great detail the organic-inorganic molecular interaction.The protective effect of this vehicle on UV-induced degradation of the flavonoid was investigated revealing a certain positive influence of the inclusion on the photostability over time.Epidermal accumulation and transdermal permeation of this molecule were ex vivo evaluated using porcine skin mounted on Franz diffusion cells. The inclusion complexation with the inorganic nanoparticles increased the penetration of quercetin into the skin after 24 h post-application without transdermal delivery.The effect of quercetin alone or given as complex with NH 2 -MSN on proliferation of JR8 human melanoma cells was evaluated by sulforhodamine B colorimetric proliferation assay. At a concentration 60 M the complex with NH 2 -MSN was more effective than quercetin alone, causing about 50% inhibition of cell proliferation.

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TiO(2) nanoparticles hazard is associated to their photocatalytic activity causing release of DNA damaging ROS (Reactive Oxygen Species), lipid peroxidation and skin damage. Various coatings have been proposed to minimize photocatalysis, while keeping the potential to block UV radiations. Uncoated and variously coated commercial nano-titania have been classified on the basis of UVB-induced lipoperoxidation of linoleic acid. A selection of the most and the least protective specimens was then examined by ESR (Electron Spin Resonance) to evidence the presence of surface paramagnetic centres and the release of ROS in aqueous suspensions (spin trapping). Paramagnetic centres and ROS were correlated with the extent of lipid peroxidation. When tested on porcine skin (mimicking the human one), titania acted as on linoleic acid. The combined use of lipid peroxidation of simple fatty acids with ESR analysis is here proposed as a possible screening tool for the evaluation of the potential toxicity of nano-titania in sunscreen preparations.

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