Monitorization of pH and OTR using a multiple shake flask platform: A tool for metabolism and cell growth assessment in mammalian cell cultures

Background From 1989 the number of bioprocesses based on mammalian cell systems has been continuously increasing from 33% of the total number of new drug approvals (up to 1989) to 60% of that number (period 2010-2014) [1]. Due to the high costs of these bioprocesses and the increasing competitiveness in the field, the good characterization and optimization of cell growth and product obtention at laboratory scale have become highly necessary. Moreover, PAT (Process Analytical Technology) initiative has beenspreadingalongthegrowingbiopharmaceuticalindustrysince 2004, when FDA published PAT guidance in order to encourageinnovativepharmaceuticaldevelopment and manufacturing [2]. In this line of thinking, big efforts are directed to develop systems at laboratory scale to obtain real-time cell culture monitoring in a non-invasive manner to avoid cell culture disturbance. In the present communication, the shake flask reader (SFR) from Presens was used in combination with the RAMOS-System [3] adapted to disposable shake flask to validate it as an useful tool for online monitoring. In this sense, we performed a study of different metabolic behavior of HEK293 cells triggered by means of environmental conditions manipulation. pH and pO2 were monitored through all cell culture and OTR, CTR and RQ were determined. The comparison of those measurements with off-line metabolite and cell growth assessment, along with further analysis of the variables, led to (1) determine a good correlation between pH evolution and HEK293 metabolic behaviour, (2) define an OTR profile corresponding to cell growth evolution and cell activity and (3) get information of cell culture differences under distinct physicochemical circumstances.