An optical counting technique with vertical hydrodynamic focusing for biological cells

Area of Science:

• Biomedical Engineering
• Microfluidics
• Cell Biology

Background:

• Scaling laboratory assays to automated microfluidic devices faces challenges in accurate cell dispensing.
• Reliable quantification of biological cells is crucial for microfluidic applications.

Purpose of the Study:

• To present a novel optical counting technique for efficient cell quantification in microfluidic systems.
• To improve the accuracy and reliability of cell number determination in microtube flow.

Main Methods:

• Cells (REH, B-lymphoid precursor leukemia) stained with fluorescent dye and imaged using a charge-coupled device (CCD) camera.
• Quantification based on total image fluorescence intensity divided by average single-cell intensity.
• Utilized vertical hydrodynamic focusing in a microdevice to concentrate cells and reduce background noise.

Main Results:

• Achieved cell counting with an uncertainty of +/-5%, significantly better than the manual Trypan Blue assay (20% uncertainty).
• Vertical hydrodynamic focusing reduced cell vertical displacement by 82% via CFD simulation and microscopy.
• Demonstrated a throughput of 100-200 cells per second at imposed flow rates.

Conclusions:

• The novel optical counting technique offers a non-destructive, accurate, and efficient method for cell quantification in microfluidics.
• Hydrodynamic focusing enhances the optical counting technique's performance by improving cell alignment.
• This method addresses a critical need for precise cell handling in automated microfluidic biological assays.