Analytical Sciences, Talk
2D-algal arrays on-chip as a tool for environmental biosensing
Coralie Suscillon1, Vera Slaveykova1
1University of Geneva
Whole-cell biosensors using microalgae as biological component allow fast and sensitive screening of environmental samples [1, 2]. However reproducible immobilization of the living cells as well as maintenance of cell viability, are still challenging [3]. Recent advances in the field of electrokinetic cell handling offer rapid on-chip concentration and immobilization. Such techniques and especially dielectrophoresis (DEP) enable to electrically trap, concentrate and focus suspended cells [4]. The present study focuses on the capture and immobilization in two-dimensional arrays by DEP of green microalga Chlamydomonas reinhardtii, a model widely used in ecotoxicology,and in combination with fluorescence detection explores sub-toxic responses such as the production of reactive oxygen species (ROS) upon short term exposure to various micropollutants. Electric field voltage and frequency, as well as collection time were optimized while ROS were used as an indicator of induced oxidative stress on cells and were detected by fluorescent microscopy using a fluorescent dye CellRox GreenĀ®. Voltage of 50V and frequency of 100 Hz of AC-current applied for 30 minutes were found to be optimal for the formation of 2D arrays. Regarding the application for environmental biosensing, the results showed an increase in the production of ROS with some of the micropollutants. Indeed, MeHg showed to induce high production of ROS at concentrations of 10-9 and 10-7 M, while rapid effect on ROS production was observed at 10-7 M Hg and a high increase of ROS production was also observed with 10-5 M Cu and with both concentrations of CuO-NPs (10 mg/L and 50 mg/L) after 60 min of exposition. However, 10-8 M Hg as well as high concentrations of diuron did not show significant impact to the cells.
The study demonstrates the capacity of DEP to trap and assemble cells in 2D arrays without affecting their viability, as well as their applicability to explore the oxidative state of algal cells exposed to different micropollutants and the potential of the 2D-whole cell algal arrays in development of early warning tools for environmental monitoring.
[1] Durrieu, C., et al., Algal biosensors for aquatic ecosystems monitoring. European Physical Journal-Applied Physics, 2006. 36(2): p. 205-209.
[2] Brayner, R., et al., Micro-algal biosensors. Analytical and Bioanalytical Chemistry, 2011. 401(2): p. 581-597.
[3] Michelini, E. and A. Roda, Staying alive: new perspectives on cell immobilization for biosensing purposes. Analytical and Bioanalytical Chemistry, 2012. 402(5): p. 1785-1797.
[4] C. Suscillon, O.D. Velev, V.I. Slaveykova, Biomicrofluidics, 2013, 7, 024109.