Ecotoxicity assessment using ciliate cells in millifluidic droplets.

Area of Science:

• Environmental Science
• Cell Biology
• Microfluidics

Background:

• Aquatic cell analysis is vital for ecosystem health.
• Understanding cellular responses to toxic chemicals like disinfectants is crucial.
• Existing methods for single-cell analysis and ecotoxicity testing have limitations.

Purpose of the Study:

• To demonstrate a droplet-based millifluidic tool for isolating and monitoring single *Paramecium tetraurelia* cells.
• To assess cellular metabolic dynamics using a viability indicator within droplets.
• To perform ecotoxicity tests and determine EC50 levels for silver nitrate, comparing results with conventional assays.

Main Methods:

• Utilized a droplet-based millifluidic system with water-in-oil emulsion droplets.
• Employed automated fluorescence signal monitoring to distinguish cells from empty droplets.
• Incorporated a viability indicator for real-time metabolic dynamic tracking.
• Conducted ecotoxicity assays exposing encapsulated *Paramecium tetraurelia* to silver nitrate.

Main Results:

• Successfully isolated and monitored individual *Paramecium tetraurelia* cells over extended periods.
• Differentiated between cell-containing and empty droplets via automated fluorescence detection.
• Quantified cellular metabolic responses and determined EC50 levels for silver nitrate.
• Demonstrated comparable or improved output compared to traditional microtiter plate assays.

Conclusions:

• Droplet-based millifluidics provides a robust platform for single aquatic cell isolation and long-term monitoring.
• This approach enables precise ecotoxicity assessment, including EC50 determination.
• The developed method offers a valuable alternative to conventional assays for aquatic toxicology studies.