Biotoxicity assays of quantum dots in in vitro cultures of Medicago sativa and Medicago truncatula

Dissertação apresentada na Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para obtenção do grau de Mestre em Biotecnologia

The aim of this thesis is a survey of the toxicity of Quantum Dots (QD’s) in in vitro cultures of the legumes Medicago sativa and Medicago truncatula. Two samples of QD’s were used to assess toxicity: QD50_MPA tested in a concentration of [160 nM] and QD68_MPA with [40 nM]. The QD50_MPA sample was applied in the already available embryogenic cell suspension culture of M. truncatula (M9-10a) to evaluate the effect of QD’s in plant differentiation at somatic embryogenesis. Results showed no differences in embryo morphology or development time. A fine suspension culture of Medicago sativa (line M699) was established to evaluate the effect of QD68_MPA QD’s in cell growth, viability as well in oxidative stress by ROS production. It was concluded that no major differences were seen when cells were exposed to QD’s in a period of 4 hours, despite an overall oxidative stress was detected. After 24 hours of exposure of cell suspension cultures to QD’s viability of cells started to decrease and ROS production was intensified, also the morphology of cells had significant changes. Moreover, it was visualized the internalization of both QD´s samples after 72 h of cell suspension cultures exposure to QD’s. QD50_MPA sample was used in the two cell suspension cultures used: M. sativa and M. truncatula, and in both lines QD’s were visualized in the nucleus and in cytosol, with the exception of the vacuoles. QD68_MPA sample was found to be up-taked by M. sativa cells and located mainly in the hyaloplasm and organelles such as plasts, and similarly to the other sample, no internalization was observed in the vacuoles.