RESUMO
Two monocarbonyl dimethylamino curcuminoids, one derived from acetone (C3) and the second one from cyclohexane (C6), were synthesized aiming to study their photophysical properties and anticancer photodynamic potential. Compound C6 exhibited lower absorbance and fluorescence than C3. Photobleaching studies showed that C3 and C6 photostability behavior in DMSO differ significantly. C3 was completely photoconverted into a new species absorbing at lower wavelength than the parent compound, whereas, C6, upon a 30 min irradiation at λ = 440 nm with 15 mW/cm2 reached a photostationary phase where a smaller amount of the initial compound coexists with some photoproducts of higher and lower absorbance. Both compounds were able to generate significant amounts of ROS upon irradiation in an aqueous environment and exhibited successful intracellular localization in skin cancer cells (A431 cells). After dark cytotoxicity studies the concentrations of 5 µM and 1 µM for C3 and C6, respectively, were selected for the PDT assessment. C3 presented light dose-dependent photodynamic activity against A431 cells, resulting in 40 % cell viability after 12 min of light irradiation (440 nm, 15 mW/cm2). On the other side, C6 showed a biphasic light dose PDT effect with cell viability gradually decreasing up to 50 % after 5 min of light exposure, and then increasing again after 8 and 12 min of light exposure. The photodynamic performance of C6 may provide a new insight into the development of PSs with reduced prolonged photosensitivity.
RESUMO
Sludge-based biosolids can be used for crop fertilization and for soil enrichment with organic matter. The prerequisites for their application are laid out in 86/278/EEC which sets limits for metals of toxicological concern in the biosolid and in the recipient soil. In this context, three kinds of sludge-based biosolids from a municipal wastewater treatment plant were submitted to the leaching tests EN 12457-2 and ΝΕΝ 7341. The leachates were examined for their physicochemical, chemical, and ecotoxicological characteristics four times within a year. Even in the more aggressive metal leaching method (ΝΕΝ 7341), results were much lower than the limits set in Council Directive 86/278/EEC. Correlations were noted between numerous parameters and principal component analysis grouped them in 3 components explaining 76% of total variation. These leaching tests were also performed on soil-biosolid samples from another investigative research in which two of the three kinds of biosolids had been incorporated in corn fields at doses 0, 20, and 40 tn/ha. EN 12457-2 leaching tests indicated that Ni and Cd leaching was affected by biosolid incorporation in soil, in relation to the type of the receiving soil (clay or sand). The leachates from the soil-biosolid mixtures were practically not toxic for the organisms tested (D. magna, V. fischeri, higher plants). In summary the biosolids were considered of low environmental risk when utilized in the field. A detailed risk assessment encompassing both chemical and ecotoxicological analysis is necessary for integrated evaluation of biosolids.