Interactions of fluorescein isothiocyanate-labeled poloxamer P188 with cultured cells

Poloxamer 188 (P188) is a tri-block copolymer with well-established membrane sealing properties. Langmuir trough experiments using lipid monolayers have suggested that P188 interacts only with damaged membranes and that it is capable of being “squeezed out” upon the restoration of membrane integrity. Here, we investigate the interactions of P188 with cultured cells by producing a fluorescent version of P188 in which the molecule is tagged with fluorescein isothiocyanate (FITC). Uninjured cells were incubated in the presence of the fluorescent poloxamer, which was then found inside the cells. This indicates that cells are capable of internalizing the molecule such that the mechanisms by which the poloxamer is retained or released by the cell may be more complex than previously thought.