Cell density monitoring and control of microencapsulated CHO cell cultures

摘要

Though mammalian cells play a key role in the manufacturing of recombinant glycosylated proteins, cell cultures and productivity are limited by the lack of suitable systems to enable stable perfusion culture. Microencapsulation, or entrapping cells within a semi-permeable membrane, offers the potential to generate high cell density cultures and improve the productivity by mimicking the cells natural environment. However, the cells being secluded by the microcapsules membrane are difficult to access for monitoring purposes. In this study, CHO-DP12 cells were cultured within calcium-alginate-poly-Llysine-alginate microcapsules in two bench scale- bioreactors, including a highly sensitive bench-scale calorimeter. The different cultures were monitored by continuous real-time dielectric spectroscopy and/or heat-flow measurements. These measurements were acquired, saved and plotted as time charts for rapid culture evaluation within a LabVIEW Virtual Instrument specifically designed for this study. Findings of this study show that capacitance measurements gave real time information on the viable cell density evolution in batch, fed batch and high density perfusion cultures; and the heat flux measurements allowed to follow the cell evolution in high density perfusion cultures. More significantly, dielectric spectroscopy gave precise information throughout each stage of the culture, from inoculation to the maximum cell density reached and through the early stages of the decline phase. Based on these results, a control strategy was implemented within the tailored LabVIEW program to control the feed rate of fed-batch cultures. The feed rate was calculated directly in the Virtual Instrument in accordance with the viable cell density and growth rate measured by dielectric spectroscopy. The capability of monitoring the evolution of microencapsulated cultures brings microencapsulation technology a step towards a potential industrial application.