Abstract
The surfactant Pluronic Fβ68 (PFβ68) is widely used in largeβscale mammalian cell culture to protect cells from shear stress that arises from agitation and gas sparging. Several studies suggested that PFβ68 is incorporated into the cell plasma membrane and could enter the cells, but without providing any direct evidence. The current study has examined this question for two cell types, one of pharmaceutical interest (CHO cells) and the other of biomedical interest (chondrocytes or cartilage cells). A fluorescent derivative of PFβ68 was synthesized to detect and localize internalized Pluronic with culture time. PFβ68 uptake by the cells was quantified and characterized. We clearly demonstrate that PFβ68 enters the cells, and possibly accumulates in the endocytic pathway. CHO cells showed an average uptake of 11.7βΒ±β6.7 (SEM) Β΅g PFβ68/10^6^ cells while the uptake of chondrocytes was 56.0βΒ±β10.9 (SEM) Β΅g PFβ68/10^6^ cells, independently of the initial PFβ68 concentration (between 0.01 and 0.2%, w/v) and of cell concentration (from 1βΓβ10^6^ to 4βΓβ10^6^ cells/mL). These uptake values were identical for both static and agitated culture conditions. Finally, we found that CHO cells are able to eliminate intracellular fluorescent PFβ68 but chondrocytes are not. These results show that the uptake of PFβ68 by the cells can severely affect PFβ68 concentration in the culture medium and thus shear protection effect. Biotechnol. Bioeng. 2008;100: 975β987. Β© 2008 Wiley Periodicals, Inc.