Schematics of the microfluidic chamber with two coplanar gold electrodes used for dielectrophoretic trapping and chaining of algal cells.
Effect of the AC-field intensity and frequency on chaining of C. reinhardtii suspended in different test media after the AC-field was applied for 45 s. Left: Percentage of cells captured in chains under voltage/frequency combinations of (a)10 V mm−1 and 200 Hz; (b) 10 V mm−1 and 1 kHz; and (c) 20 V mm−1 and 1 kHz. Right: Microscope images illustrating the chain structure and length for each combination of field intensity and frequency.
Effect of the AC-field duration on the collection of the algal cells in chains (a) and on the chain structure at different voltages in 10−3M MOPS ((b) and (c)). (a) Kinetics of cells collection in chains for 10 and 20 V mm−1. The signal frequency was 1 kHz. Optical micrographs of algal chains assembled after 45 s (b) and 600 s (c) for AC-field intensity of 10 and 20 V mm−1. Initial slope used as a measure of the initial rate of chaining is given in red.
Collection of cells of C. reinhardtii in freshwaters and structure of the chains as a function of time. The graphs represent the percentage of chained cells at 10 and 20 V mm−1 in water from Geneva Lake (a), Rhône River (b), and Laconnex Pond (c). The optical micrographs show the structure of the chains at 45 s and 600 s for both voltages. The frequency was 1 kHz in all experiments.
Effect of the medium on the collection of cells of C. reinhardtii and structure of the chains at 45 s (a) and 600 s (b). The graphs represent the percentage of cells in chain at 20 V mm−1 and 1 kHz. The optical micrographs show the structure of the chains at 45 s and 600 s for each model system.
Percentage of cells in chains at 45 s (a) and 600 s (b) in different media versus the conductivity of cell suspensions. The data at 600 s point out to abnormally high rate of chain formation. (c) Percentage of cells in chains vs. the cell zeta potential. AC-field intensity of 20 V mm−1 and frequency of 1 kHz.
Effect of DEP on the C. reinhardtii lipid peroxidation status ((a)–(c)) and membrane integrity ((d)–(f)) obtained by flow cytometry prior DEP ((a) and (d)) after 600 s of DEP ((b) and (e)) and after treatment with pro-oxidant 5 × 10−3M H2O2 ((c) and (f)). Two dimensional dot plots represent algal autofluorescence (FL3) versus fluorescence signal of BODYPI (FL1) or PI (FL2). Micrographs ((a)–(c)) obtained with fluorescence microscopy represent (up to down): algae observed with the bright field, algae observed with the fluorescent filter allowing the detection of chlorophyll a (red), and algae observed with the fluorescent filter allowing the detection of BODIPY (green). Micrographs ((d)–(f)) show algae observed with the bright field and algae observed with the fluorescent filter allowing the detection of chlorophyll a and PI (red). Medium 10−3M MOPS, pH = 7.0.
Major cation and anion concentrations in the tested surface waters. The values are averaged over 3 measurements ± standard deviations.
Composition of the tested model systems and concentration range. pH = 7.0.
Zeta potential (ζ), electrophoretic mobility (μ), and conductivity (σ) of C. reinhardtii suspensions in surface waters and simple model media. The values are mean of 3 replicates and standard deviations.
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