Abstract
The investigation of contaminant impact on algae requires rapid and reliable cell collection and optical detection. The capability of alternative current (AC) dielectrophoresis (DEP) collection of whole cell arrays with combined fluorescence microscopy detection to follow the alterations of chlorophyll fluorescence during environmental contaminant exposure was explored. The application of an AC-field of 100 V cm−1, 100 Hz for 30 min to capture and immobilize the cells of green alga Chlamydomonas reinhardtii in two-dimensional (2D) arrays does not induce changes in chlorophyll fluorescence. The results demonstrate that DEP-based 2D-arrays allow non-invasive detection of chlorophyll fluorescence change upon exposure to high concentrations of copper oxide nanoparticles and ionic copper. These results were in agreement with data obtained by flow cytometry used as a comparative method. The tool was also applied to follow the effect of a number of ubiquitous contaminants such as inorganic mercury, methylmercury, and diuron. However, a statistically significant short-term effect was observed only for mercury. Overall, DEP-based 2D-arrays of algal cells with fluorescence detection appear to be suitable for stain-free probing the effects on the photosynthetic microorganisms in highly polluted environment.
Highlights
Among different biological responses used for ecotoxicological purposes, chlorophyll a fluorescence is widely applied for the determination of contaminant-induced effects on photosynthetic organisms [1,2]
The present study explores the capabilities of the newly developed 2D-microalgal arrays to follow the change in the chlorophyll fluorescence during the short-term exposure to an emerging contaminant such as copper oxide nanoparticles (CuO-NPs), as well as other contaminants including dissolved copper sulfate (Cu), inorganic mercury (Hg), methylmercury (MeHg), and diuron
A unicellular green alga C. reinhardtii (CPCC 11, Canadian Phycological Culture Centre, Waterloo, ON, Canada), was grown in a 4× diluted Tris-Acetate-Phosphate medium (Sigma-Aldrich, Buchs, Switzerland) to the mid-exponential growth phase at 20 ◦ C under continuous illumination of 6000 lux and continuous shaking at 115 rpm (INFORS HT, Basel, Switzerland)
Summary
Among different biological responses used for ecotoxicological purposes, chlorophyll a fluorescence is widely applied for the determination of contaminant-induced effects on photosynthetic organisms [1,2]. Some of the most hazardous contaminants present in the environment can induce a modification in photosynthesis activity [4,5] and an alteration of the fluorescence of chlorophyll in a concentration-dependent manner [4,5]. A number of studies have already demonstrated the effect of different contaminants on the photosystem II (PSII) of the photosynthetic organisms [3]. The interaction of these contaminants, from herbicides or pesticides to heavy metals, with PSII could cause an inhibition of the electron transfer from the primary acceptor
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