Traceable impedance-based single-cell pipetting, from a research set-up to a robust and fast automated robot: DispenCell-S1.

Single-cell isolation is a truly transformative tool for the understanding of biological systems. It allows single-cell molecular analyses and considers the heterogeneity of cell populations, which is of particular relevance for the diagnosis and treatment of evolving diseases and for personalized medicine. Single-cell isolation is also a key process in cell line development, where it is used to obtain stable and high producing clonally-derived cell lines, thus contributing to the efficiency, safety and reproducible quality of the drug produced. High producing clonally-derived cell lines are however rare events and their identification is a time-consuming process that requires the screening of thousands of clones. Therefore, there is an unmet need for a device that would allow the fast and efficient isolation of single cells, while preserving their integrity and providing an insurance of their clonality. We proposed earlier an impedance based pipetting technology for isolation of single cells (Bonzon et al., 2020), with initial validations for state-of-the-art stem cell in-vitro and in-vivo assays (Muller et al., 2020). Here, we present the transition from this pioneering technology developed in an academic setting into an automated instrument, called DispenCell-S1, allowing for traceable isolation of single cells. We developed and validated models predicting the performances for 96-well plates single-cell isolation. This resulted in a time of dispense down to 3 min and a plate filling rate up to 96%. Finally, we obtained an impedance signal reliability for proof of single particle isolation of 99% with beads and ranging from 93 to 95% with CHO cells.

Impedance-Based Single-Cell Pipetting.

Many biological methods are based on single-cell isolation. In single-cell line development, the gold standard involves the dilution of cells by means of a pipet. This process is time-consuming as it is repeated over several weeks to ensure clonality. Here, we report the modeling, designing, and testing of a disposable pipet tip integrating a cell sensor based on the Coulter principle. We investigate, test, and discuss the effects of design parameters on the sensor performances with an analytical model. We also describe a system that enables the dispensing of single cells using an instrumented pipet coupled with the sensing tip. Most importantly, this system allows the recording of an impedance trace to be used as proof of single-cell isolation. We assess the performances of the system with beads and cells. Finally, we show that the electrical detection has no effect on cell viability.