Fluorescence in vivo imaging in the monitoring of effect of nanoparticles on microalgae

In this study, the fluorescence in vivo imaging was used to investigate the effect of selected nanoparticles – NPs (ZnO) on microalgae (Scenedesmus quadricauda and Chlorella vulgaris) growth. The intrinsic fluorescence was affected by application of nanoparticles into the growing medium (liquid and solid) due to a change in growth and metabolic activity of microalgae. Pigments, especially chlorophylls and carotenoids, are responsible for autofluorescence of microorganisms. Therefore, fluorescence can be used as a tool for rapid and easy evaluation of the expression of these compounds. These pigments minimize photooxidative cell damage. Pigments expression can be disturbed by other stress-related substances such as presence of NP that are likely to damage this protective mechanism i) indirectly (by formation of reactive oxygen species) and ii) directly (by disturbing biomembranes). Fluorescence imaging is an efficient and powerful technique, but its application to plants or algae is not very common. By fluorescence imaging and correlation with the total amount of chlorophylls and carotenoids, it was possible to evaluate the effect of NPs on individual microalgae specie by in vivo imaging.