No abstract

Antioxidants of natural origin are used in medicines and cosmetics with several benefits, such as: photoprotective action, anti-aging, moisturizing and anti-pollutant. The human epidermis has an important barrier effect and limited anti-oxidative capacity, so studies with the epidermis is essential. Shed snakeskin (SS) is composed of the stratum corneum and provide a barrier like human stratum corneum. This alternative does not show a tendency to microbiological degradation and can be considered ecologically correct. This study intends to present, in an innovative way, the Electron Paramagnetic Resonance spectroscopy (EPR) and The Forster Resonance Energy Transfer (FRET) were employed to evaluate the natural antioxidant substances (Resveratrol/ RES 3.0 w/w and Ferulic acid/ FA 1.0 w/w) associated with organic sunscreens ingredients (Ethylhexyl Methoxycinnamate/ EHMC 10.0%w/w and Butyl Methoxydibenzoylmethano/ BMBM 5.0%w/w in a photoprotective emulsion (PB). Furthermore, the use of SS seedlings as a possible alternative to the use of human or animal skin ex-vivo. RES and FA can absorb the energy emitted by the EHMC in FRET, preventing the passage through the triplet state, favoring the photostability of this sunscreen, the same not ocorred with the BMBM. Antioxidant activity of the photoprotective formulations was evaluated in vitro by the percentual inhibition of the radical 2,2-diphenyl-1-picrihydrazyl (DPPH•). The antioxidant activity with RES, 97.0% inhibition of DPPH• in the PB, was higher than PB + FA (91.0%), however the concentration of RES in PB was higher than FA. The sample SS + PB + FA was the one with the lowest number of free radicals after irradiation, which corroborated the high percentage of radical inhibition in vitro and it was the better association with the photoprotective formulation.

Designing new materials with suitable dose-response efficiency is a great challenge in radiation dosimetry search. Yttria (Y2O3) has excellent optical, mechanical, chemical, and thermal properties. Besides, yttria exhibits crystal characteristics that provide insertion of other rare earths, forming innovative materials. Nevertheless, there are quite few studies on formation, microstructural and EPR response evaluation of yttria. This work reports the formation and EPR characterization of europium-yttria micro rods for radiation dosimetry. Ceramic rods obtained by sintering at 1600ºC/4h in air were exposed to gamma radiation with doses from 1Gy to 150kGy. Particle, microstructural and dosimetry characterizations were performed by PCS, XRD, SEM, OM, and EPR techniques. As sintered europium-yttrium rods exhibited dense microstructure (90% theoretical density) and linear EPR dose response behavior up to 10kGy. These results show that europium-yttria is a promising material for radiation dosimetry.