Noninvasive Viability Profiling of 3D Spheroids via Flow-through Electrical Impedance Spectroscopy

Area of Science:

• Biomedical Engineering
• Cancer Research
• Drug Discovery

Background:

• Three-dimensional (3D) cell models like spheroids and organoids improve preclinical study prediction for anti-cancer therapies.
• Integrating 3D models into drug discovery is limited by the need for rapid, reliable viability assessment in high-throughput screening.
• Current viability assays are often labor-intensive, destructive, and unsuitable for high-throughput applications or model reuse.

Purpose of the Study:

• To demonstrate electrical impedance spectroscopy (EIS) for label-free, individual spheroid viability profiling.
• To develop and validate an EIS sensor integrated into a microfluidic chip for high-throughput screening.
• To assess the reliability and transferability of EIS for monitoring spheroid responses to different drug treatments.

Main Methods:

• A differential EIS sensor was integrated into a flow-through microfluidic chip with self-aligned electrodes.
• Liver cancer spheroids were exposed to varying concentrations of dimethyl sulfoxide and doxorubicin.
• EIS responses were measured across six frequencies, and results were compared with fluorescence imaging and ATP quantification.

Main Results:

• An optimized EIS frequency pair enabled size-independent monitoring of spheroid viability.
• The EIS method reliably reflected viability changes and detected inter- and intra-treatment differences with single-spheroid resolution.
• The same frequency pair detected viability changes for both tested compounds, indicating method transferability.
• Additional EIS features improved the classification of spheroids with subtle viability differences.

Conclusions:

• EIS is a promising non-invasive technique for single-spheroid viability profiling.
• This method supports high-throughput drug screening using 3D spheroid models.
• EIS offers a valuable tool to enhance the predictive power of in vitro cancer drug discovery.