Disposable flowcell for spectroscopic analysis in bioprocesses

The US Food and Drug Administration (FDA) has high regulatory and quality requirements for the development and more importantly production of pharmaceuticals. Ideally, the production process is continuously monitored and recorded noninvasively to allow immediate control action if necessary. There are a multitude of established optical detection systems for classical stainless steel bioreactors using fiber optic probes, light guides, light sources and detectors for absorbance, fluorescence and Raman detection techniques. These systems are steam-sterilizable in place, reusable but are complex and expensive. Such systems are not well suited to use on the growing market of pre-sterilized disposable bioreactors, since there is a lack of sterile interface technology. A novel disposable and pre-sterilized flow cell has been developed, which can be easily connected to disposable bioreactors by sterile tube connections. The disposable BioFlowCell is clamped into a reusable flow cell holder, which is equipped with light guides, a light source and a detection unit. By this modular construction, spectroscopic techniques, like UV/Vis, fluorescence, turbidity by scattered light, near infrared or Raman spectroscopy are now usable for modern disposable bioreactors. We report on the suitability for in-line monitoring of mammalian cell cultures by detecting optical absorbance at 260, 280, 340 and 450 nm wavelengths to study aromatic amino acids, NADH and flavins simultaneously in a BioFlowCell with multiple pathlengths. Further, we studied in a second optical flowcell design, if light scattering and absorption in turbid samples can be used for biomass concentration measurements, as well as size or the viability of cells during continuous bioprocess experiment lasting several days.