Retention dynamics of amphiphilic polymers PEG-lipids and PVA-Alkyl on the cell surface

We tested two kinds of amphiphilic polymers for cell surface modification: a poly(ethylene glycol)-conjugated phospholipid (PEG-lipid) and a poly(vinyl alcohol) that carried alkyl side chains (PVA-alkyl). Both polymers were expected to anchor to the lipid bilayer of the cell membrane through hydrophobic interactions. We followed the kinetics of these fluorescently labeled amphiphilic polymers (fPEG-lipid, fPVA-alkyl) over time on living cells with confocal scanning laser microscopy and flow cytometry. We found that fPEG-lipids and fPVA-alkyl polymers were not cytotoxic, and they were released from the cell surface without triggering endocytosis. The gradual release from the cell surface was influenced by the hydrophobicity of the alkyl chains, which affected their stability. The amphiphilic polymers tended to aggregate on the cell surface; in particular, the aggregation of PVA-alkyl was clearly identified. Although most of PEG-lipids and PVA-alkyl polymers did not appear to in the cytoplasm, the cells were able to endocytose lipid molecules, as expected. These results suggested that the retention time of modified amphiphilic polymers on the cell surface should be a consideration when modifying cell surfaces to enhance cell transplantation.