Process analytical technology (PAT) instruments are generally built for large-scale bioprocesses, leaving smaller production runs with fewer options for real-time monitoring. As batch sizes decline with process intensification and more personalized therapies, that gap is becoming more significant, particularly for measuring viable cell density inside small vessels.
Researchers from Eastern Switzerland University of Applied Sciences and Zurich University of Applied Sciences have developed a miniature bioimpedance sensor as a potential solution. The proof-of-concept device has a 1 x 10 mm footprint and operates with a 25 µL working volume. In tests with Chinese hamster ovary (CHO) cells, its measurements closely tracked reference cell counts.
The team measured electrical impedance across a frequency range of 10 kHz to 5 MHz. The sensor’s detection limit was approximately 0.5 × 10⁶ cells per milliliter, and the reported correlation with reference counts was R² = 0.92. The researchers presented the results at the Eurosensors 2026 meeting, noting that the work is still at an early stage.
The device uses platinum thin-film electrodes fabricated on fused silica and includes two microfluidic channels. In 14-day CHO fed-batch studies, the chip demonstrated continuous at-line monitoring through an external module. The researchers are now working to account for changes in culture medium that can affect the signal.
Their next steps include packaging the chip as an insertion probe for direct in-line use in a bioreactor and developing multivariate data models. The team is also seeking industrial partners to help advance the sensor toward commercial use.