Capacitance spectroscopy enables real‐time monitoring of early cell death in mammalian cell culture

Abstract

Background/Aims Previous work developed a quantitative model using capacitance spectroscopy in an at‐line setup to predict the dying cell percentage measured from a flow cytometer. This work aimed to transfer the at‐line model to monitor lab‐scale bioreactors in real‐time, waiving the need for frequent sampling and enabling precise controls. Methods and Results Due to the difference between the at‐line and in‐line capacitance probes, direct application of the at‐line model resulted in poor accuracy and high prediction bias. A new model with a variable range and offering similar spectral shape across all probes was first constructed, improving prediction accuracy. Moreover, the global calibration method included the variance of different probes and scales in the model, reducing prediction bias. External parameter orthogonalization, a preprocessing method, also mitigated the interference from feeding, which further improved model performance. The root‐mean‐square error of prediction of the final model was 6.56% (8.42% of the prediction range) with an R2 of 92.4%. Conclusion The culture evolution trajectory predicted by the in‐line model captured the cell death and alarmed cell death onset earlier than the trypan blue exclusion test. Additionally, the incorporation of at‐line spectra following orthogonal design into the calibration set was shown to generate calibration models that are more robust than the calibration models constructed using the in‐line spectra only. This is advantageous, as at‐line spectral collection is easier, faster, and more material‐sparing than in‐line spectra collection.

Adaptive modeling optimized by the data fusion strategy: Real‐time dying cell percentage prediction using capacitance spectroscopy

“…Figure2shows the Cole-Cole α evolution overlaid with the To-Pro-3%. The trajectory of α closely resembled the previously reported PLS model, indicating a similar pattern 1. Notably, the deflection of Cole-Cole effectively signaled the onset of early cell death, evident in substantial increases in To-Pro-3% at around 84 h (Figure2a) and 100 h (Figure2b).…”

“…The cells were cultured in 5-L Sartorius Biostat bioreactors with a 4 L working volume, which has similar process conditions to those previously described. 1 Six independent lab-scale cell cultures were performed in three runs, with two batches in each run. Fed-batch mode was applied in the first two runs (four batches), which had periodical bolus feed and temperature changes.…”

“…The healthy mammalian cells (viable cells that have not initiated the cell death pathway) in the bioreactors are the primary workhorses for biologics manufacturing 1,2 . Under the guidance of transgenes, these healthy cells efficiently convert nutrients into the desired products 3 .…”

“…Moreover, Ma et al and Zalai et al have qualitatively captured cell death onset using mechanistic modeling or multivariate data analysis 34,35 . Our previous articles have reported the quantitative monitoring of cell death with capacitance spectroscopy and MVDA 1,36 . This manuscript aims to enhance model accuracy through the implementation of a data fusion strategy.…”

“…34,35 Our previous articles have reported the quantitative monitoring of cell death with capacitance spectroscopy and MVDA. 1,36 This manuscript aims to enhance model accuracy through the implementation of a data fusion strategy. Additionally, this manuscript explores the model difference between MVDA and mechanistic models (Cole-Cole model 34 ).…”