Scientists from a global institute for bioprocessing research are pioneering two new approaches for continuous monitoring without fluorescent labels. Michael Butler, PhD, a principal investigator at Ireland’s National Institute for Bioprocessing Research & Training (NIBRT), is leading projects developing high-resolution optical and capacitance methods to investigate the viability of Chinese Hamster Ovary (CHO) cells in bioreactors.

“The uniqueness is getting these high-resolution images that will tell us what stage of metabolism cells are in the [growth/death] process,” Butler explains, referring to the optical system.

The first project uses a high-resolution camera to produce images of layers of cells streamed out of a bioreactor. After these images are digitized, they can run through an algorithm to produce 40 parameters, including convexity and circularity, which can be put into clusters with principal component analysis (PCA) to produce a viability measure, notes Butler.

“This is of value compared to the standard method, Trypan Blue, which can tell us if the membrane of the cell is damaged, but it’s only a late-stage measure of the demise of cells,” Butler says.

The second project uses a sterilized capacitance probe that is placed in the bioreactor where it creates a spherical electrical field with a current frequency of 0.58Mhz. The electrical field polarizes the cells, and the electrical current perturbs that polarization.  According to Butler, this allows the researchers to measure the ionic balance in the cell, which is a measure of its metabolism and proliferation.

“One of the questions that always comes up is the apparent plateau of cell growth and decrease in cell viability that occurs when measuring with a capacitance probe,” continues Butler. “What we’re measuring with the capacitance probe, unlike with Trypan blue, is the limited nutrient affect the ionic balance in the cell and that change in internal conductivity affects the probe at an early stage.”

Butler points out that his monitoring methods are applicable to all cell types, including virus-perturbed cells for vaccine production.

The NIBRT is working with Canty Engineering to develop the optical system, which Butler says should be available in a year or so, adding that the capacitance probe is already available Aber Instruments used in the brewing industry.

“We’re looking at extra applications [for the pharmaceutical industry] using these frequency sweeps,” he says.

He spoke about his monitoring methods at Bioprocessing Summit Europe in March.