Quantification of water solubilized CdSe/ZnS quantum dots in Daphnia magna

The relative transparency of Daphnia magna (daphnia) and the unique optical properties of quantum dots (QDs) were paired to study the accumulation potential and surface coating effects on uptake of amphiphilic polymer coated CdSe/ZnS QDs. Fluorescence confocal laser scanning microscopy was used to visualize and spectrally distinguish QDs from competing autofluorescent signals arising from the daphnia themselves and their food sources. QDs were found to accumulate within the digestive tracts of daphnia, as well as, in some cases, adhere to the carapace, antennae, and thoracic appendages. After 48 h of gut clearance with and without feeding, QD fluorescence signal was still apparent in the digestive tracts of daphnia, and inductively coupled plasma mass spectrometry (ICP-MS) measurements confirmed that 36-53% of the initial uptake was retained. As surface charge and pegylation can influence the uptake of nanoparticles, uptake of QDs coated with two different amphililic polymers and their polyethylene glycol (PEG) coated counterparts was also examined. Fluorescence microscopy and ICP-MS measurements revealed differences in uptake after 24 h of exposure which were attributed to particle surface coating and stability.