In-situ microscopy: Online process monitoring of mammalian cell cultures.

The in-situ microscope is a system developed to acquire images of mammalian cells directly inside a bioreactor (in-situ) duringa fermentation process. It requires only minimal operator intervention and it is well suited for either batch or long-termperfusion fermentation runs. The system fits into a 25 mm standard port and has a retractable housing, similar to the industry standard InTrac. Therefore, it can be cleaned and serviced without interruption of the process or risking contamination. A sampling zone inside the bioreactor encloses adefined volume of culture and an image sequence is taken. The height of the sampling zone is set by the control program and canbe adjusted during the cultivation to accommodate a wide range of change in cell density. The system has an infinity correctedoptical train and uses a progressive scan CCD camera to acquirehigh quality images. Process relevant information like cell density is extracted fromthe images by digital image processing software, currently in development for mammalian cells (CHO, BHK). The first version ofthe software will be able to estimate the cell density, cellsize distribution and to give information of the degree of aggregation (single and double cells, cell clusters).