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Two-Dimensional Algal Collection and Assembly by Combining AC-Dielectrophoresis with Fluorescence Detection for Contaminant-Induced Oxidative Stress Sensing.

Siebman C, Velev OD, Slaveykova VI - Biosensors (Basel) (2015)

Bottom Line: An alternative current (AC) dielectrophoretic lab-on-chip setup was evaluated as a rapid tool of capture and assembly of microalga Chlamydomonas reinhardtii in two-dimensional (2D) close-packed arrays.The results showed significant increase of the cellular ROS when C. reinhardtii was exposed to high concentrations of methylmercury, CuO-NPs, and 10⁻⁵ M Cu.Overall, this study demonstrates the potential of combining AC-dielectrophoretically assembled two-dimensional algal structures with cell metabolic analysis using fluorescence staining, as a rapid analytical tool for probing the effect of contaminants in highly impacted environment.

View Article: PubMed Central - PubMed

Affiliation: Environmental Biogeochemistry and Ecotoxicology, Institute F.-A. Forel, Earth and Environmental Science, Faculty of Sciences, University of Geneva, 10 route de Suisse, Versoix CH-1290, Switzerland. coralie.suscillon@unige.ch.

ABSTRACT
An alternative current (AC) dielectrophoretic lab-on-chip setup was evaluated as a rapid tool of capture and assembly of microalga Chlamydomonas reinhardtii in two-dimensional (2D) close-packed arrays. An electric field of 100 V·cm⁻¹, 100 Hz applied for 30 min was found optimal to collect and assemble the algae into single-layer structures of closely packed cells without inducing cellular oxidative stress. Combined with oxidative stress specific staining and fluorescence microscopy detection, the capability of using the 2D whole-cell assembly on-chip to follow the reactive oxygen species (ROS) production and oxidative stress during short-term exposure to several environmental contaminants, including mercury, methylmercury, copper, copper oxide nanoparticles (CuO-NPs), and diuron was explored. The results showed significant increase of the cellular ROS when C. reinhardtii was exposed to high concentrations of methylmercury, CuO-NPs, and 10⁻⁵ M Cu. Overall, this study demonstrates the potential of combining AC-dielectrophoretically assembled two-dimensional algal structures with cell metabolic analysis using fluorescence staining, as a rapid analytical tool for probing the effect of contaminants in highly impacted environment.

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(a) Bright-field image of the algal cell suspensions in the microfluidic chamber with no AC-field applied; (b) Effect of field intensity and frequency; and (c) duration on the percentage of the surface of the chamber covered by cells. The bright-field images represent the 2D-assembly of C. reinhardtii obtained at combination of 100 V·cm−1, 100 Hz after 30 and 120 min duration using four-point stainless steel needle electrodes. Initial concentration of algae in suspensions: 5 × 106 cells·mL−1.
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biosensors-05-00319-f002: (a) Bright-field image of the algal cell suspensions in the microfluidic chamber with no AC-field applied; (b) Effect of field intensity and frequency; and (c) duration on the percentage of the surface of the chamber covered by cells. The bright-field images represent the 2D-assembly of C. reinhardtii obtained at combination of 100 V·cm−1, 100 Hz after 30 and 120 min duration using four-point stainless steel needle electrodes. Initial concentration of algae in suspensions: 5 × 106 cells·mL−1.

Mentions: The key role of DEP on the process of cell assembly was confirmed first by comparing results obtained in the setup without AC-field and with AC-field applied for 30 min, as well as the effect of AC-field intensity and frequency (Figure 2). The application of AC electric field allowed the formation of a closely packed cell structure, defined further as 2D-assembly without any 3D-stacking, covering 31.9% ± 3.7% of the microchamber surface. This is a consequence of the 2D-algal cell assembly being a two stage process. 1D-cell chains are first formed in the direction of the applied electric field due to the attractive axial dipolar interactions. The AC field was then switched to the other electrode pair to let the cells realign along the perpendicular direction. These membrane-like structures disassemble when the electric field is switched off. When no AC-field was applied, 30 min after injection, highly dispersed cells covering 14.8% ± 1.3% of the microfluidic chamber surface were observed.


Two-Dimensional Algal Collection and Assembly by Combining AC-Dielectrophoresis with Fluorescence Detection for Contaminant-Induced Oxidative Stress Sensing.

Siebman C, Velev OD, Slaveykova VI - Biosensors (Basel) (2015)

(a) Bright-field image of the algal cell suspensions in the microfluidic chamber with no AC-field applied; (b) Effect of field intensity and frequency; and (c) duration on the percentage of the surface of the chamber covered by cells. The bright-field images represent the 2D-assembly of C. reinhardtii obtained at combination of 100 V·cm−1, 100 Hz after 30 and 120 min duration using four-point stainless steel needle electrodes. Initial concentration of algae in suspensions: 5 × 106 cells·mL−1.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4493552&req=5

biosensors-05-00319-f002: (a) Bright-field image of the algal cell suspensions in the microfluidic chamber with no AC-field applied; (b) Effect of field intensity and frequency; and (c) duration on the percentage of the surface of the chamber covered by cells. The bright-field images represent the 2D-assembly of C. reinhardtii obtained at combination of 100 V·cm−1, 100 Hz after 30 and 120 min duration using four-point stainless steel needle electrodes. Initial concentration of algae in suspensions: 5 × 106 cells·mL−1.
Mentions: The key role of DEP on the process of cell assembly was confirmed first by comparing results obtained in the setup without AC-field and with AC-field applied for 30 min, as well as the effect of AC-field intensity and frequency (Figure 2). The application of AC electric field allowed the formation of a closely packed cell structure, defined further as 2D-assembly without any 3D-stacking, covering 31.9% ± 3.7% of the microchamber surface. This is a consequence of the 2D-algal cell assembly being a two stage process. 1D-cell chains are first formed in the direction of the applied electric field due to the attractive axial dipolar interactions. The AC field was then switched to the other electrode pair to let the cells realign along the perpendicular direction. These membrane-like structures disassemble when the electric field is switched off. When no AC-field was applied, 30 min after injection, highly dispersed cells covering 14.8% ± 1.3% of the microfluidic chamber surface were observed.

Bottom Line: An alternative current (AC) dielectrophoretic lab-on-chip setup was evaluated as a rapid tool of capture and assembly of microalga Chlamydomonas reinhardtii in two-dimensional (2D) close-packed arrays.The results showed significant increase of the cellular ROS when C. reinhardtii was exposed to high concentrations of methylmercury, CuO-NPs, and 10⁻⁵ M Cu.Overall, this study demonstrates the potential of combining AC-dielectrophoretically assembled two-dimensional algal structures with cell metabolic analysis using fluorescence staining, as a rapid analytical tool for probing the effect of contaminants in highly impacted environment.

View Article: PubMed Central - PubMed

Affiliation: Environmental Biogeochemistry and Ecotoxicology, Institute F.-A. Forel, Earth and Environmental Science, Faculty of Sciences, University of Geneva, 10 route de Suisse, Versoix CH-1290, Switzerland. coralie.suscillon@unige.ch.

ABSTRACT
An alternative current (AC) dielectrophoretic lab-on-chip setup was evaluated as a rapid tool of capture and assembly of microalga Chlamydomonas reinhardtii in two-dimensional (2D) close-packed arrays. An electric field of 100 V·cm⁻¹, 100 Hz applied for 30 min was found optimal to collect and assemble the algae into single-layer structures of closely packed cells without inducing cellular oxidative stress. Combined with oxidative stress specific staining and fluorescence microscopy detection, the capability of using the 2D whole-cell assembly on-chip to follow the reactive oxygen species (ROS) production and oxidative stress during short-term exposure to several environmental contaminants, including mercury, methylmercury, copper, copper oxide nanoparticles (CuO-NPs), and diuron was explored. The results showed significant increase of the cellular ROS when C. reinhardtii was exposed to high concentrations of methylmercury, CuO-NPs, and 10⁻⁵ M Cu. Overall, this study demonstrates the potential of combining AC-dielectrophoretically assembled two-dimensional algal structures with cell metabolic analysis using fluorescence staining, as a rapid analytical tool for probing the effect of contaminants in highly impacted environment.

Show MeSH
Related in: MedlinePlus