Spatially-resolved optical monitoring of bioreactor cell growth.

Bioreactors are used for the industrial-scale culture of cells to obtain valuable products such as pharmaceuticals, enzymes, and biofuels; however, monitoring the growth conditions within the vessels is challenging and is often dependent on single-point ex-situ measurements. Further, spatial heterogeneities are known to exist within these environments, thereby creating regions of low growth or incomplete reactions, reducing yield, and importantly, reducing the applicability of single-point measurement methods. Optical imaging is an attractive method for remote spatially-resolved measurement platforms; however, the strong optical scattering within cell cultures makes imaging almost impossible. Here, we utilise this parasitic scattering effect and present a spatially resolved optical method for monitoring cell density within a bioreactor, using optical measurement of local scattering parameters as a proxy measurement for cell density. Our method is non-invasive and does not require the removal of any cell material from within the vessel. We propose that our optical measurement method can be incorporated into process-control feedback systems, providing insightful information on cell growth that can be used to deliver higher spatial homogeneity and increased yields.