With an increasing use of quantum dots (QDs) in many applications, their potential hazard is of growing concern. However, little is known about their ecotoxicity, especially in vivo. In the present study, we employed freshwater macroinvertebrate, Daphnia magna, to evaluate toxicity characteristics of cadmium selenide/zinc selenide (CdSe/ZnSe) in relation to surface coatings, e.g., mercaptopropionic acid QD ((MPA)QD), and gum arabic/tri-n-octylphosphine oxide QD ((GA/TOPO)QD), and light conditions, i.e., dark, fluorescent light, environmental level of ultraviolet (UV) light, and sunlight. The results of the present study showed that D. magna was more susceptible to (GA/TOPO)QD exposure compared to (MPA)QD. The surface coating of QD appeared to determine the stability of QDs and hence the toxicity, potentially by size change of or the release of toxic components from QDs. However, (GA/TOPO)QD was still less toxic than the equivalent level of CdCl₂. The toxicity of all the tested compounds increased by changing the light condition from dark to white fluorescence to UV-B light, and to natural sunlight. The effect of light condition on QDs toxicity could also be explained by photostability of the QDs, which would affect size of the particle, release of toxic component ions, and generation of reactive oxygen species. Considering increasing use of QDs in various applications, their environmental fates and corresponding toxic potentials deserve further investigation.

A modified MTT protocol-based microfluidic image cytometry (lFIC) was performed to assess Cd 21 induced cytotoxicity. The expanded capabilities of lFIC, such as in situ measurement, high-throughput, and multiparametric analysis of adherent cells under precisely controlled chemical environments of microfluidic channels, were demonstrated in this study. Multiparametric analysis of lFIC data has enabled us to categorize the progress of cell death into at least four different subgroups based on their morphology and metabolic activity. These advantages of the MTT-based lFIC as a simpler, cheaper, and faster in vitro cell-based assay tool have many implications in biomedical, pharmaceutical, toxicological, and biological application areas, and we propose this technique as a future high throughput-high content screening (HT-HCS) platform for cytotoxicity assays and drug screening. ' 2012 International Society for Advancement of Cytometry

Microfluidic systems have significant implications in the field of in vitro cell-based assays since they may allow conventional cell-based assays to be conducted in an automated and high-throughput fashion. In this study, we combined a simple microfluidic cells-on-chip system with a morphology-based image cytometric analysis approach for the assessment of Cd(2+) induced apoptosis of Chang liver cell line. A simple and efficient in situ monitoring method for quantifying the progress of a cell death event was developed and is presented here. Reasonable agreement of the estimated EC(50) value from this study with those from the literature and a close correlation between the observed changes in cell morphology (i.e., circularity) and the amount of reactive oxygen species (ROS) generation confirmed the validity of this morphology-based microfluidic image cytometric (microFIC) assessment method. We propose this morphology-based microFIC approach as an easy and efficient way to assess cytotoxicity which can be adapted to high-throughput screening platforms for in vitro cytotoxicity assays as well as drug screening.

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