Impedance spectroscopy flow cytometry: on-chip label-free cell differentiation

Area of Science:

• Biophysics
• Microfluidics
• Cell Biology

Background:

• Microfabricated impedance spectroscopy enables rapid dielectric characterization of cells.
• Impedance measurements provide insights into cell size, membrane capacitance, and cytoplasm conductivity.
• Amplitude, opacity, and phase data allow label-free discrimination of cell populations.

Purpose of the Study:

• To demonstrate label-free cell differentiation using impedance spectroscopy in a microfluidic flow cytometer.
• To characterize polystyrene beads, red blood cells (RBCs), ghosts, and fixed RBCs.

Main Methods:

• Utilized a microfabricated impedance spectroscopy flow cytometer with a simple microfluidic channel.
• Measured individual cells at a rate of 1,000 per minute across a frequency range of 350 kHz to 20 MHz.
• Employed two simultaneously applied discrete frequencies for impedance measurements.

Main Results:

• Achieved submicron accuracy in cell size measurement.
• Successfully differentiated polystyrene beads from RBCs using opacity.
• Distinguished RBCs from ghosts via phase information and RBCs from fixed RBCs using opacity.
• Observed increased opacity in fixed RBCs correlated with decreased cytoplasm conductivity and membrane capacitance due to protein cross-linking.

Conclusions:

• Presents a novel on-chip flow cytometer utilizing impedance spectroscopy for label-free cell differentiation.
• Highlights the potential of this technology as a powerful tool for advanced cell characterization.
• Demonstrates the efficacy of impedance spectroscopy in distinguishing cell types based on their dielectric properties.