Not all polymers are equal.

The effects of extracellular fluid viscosity on cell behavior are increasingly appreciated. Smith et al. observed that cells respond differently to two polymers that generate identical fluid viscosity, suggesting that molecular origins of viscosity shape cellular behavior. One possible explanation is that differences in interpolymer interaction arising from a polymer's charge distribution produce Newtonian vs Non-Newtonian rheology, thereby changing the interactions with cell membrane and contributing to distinct cellular responses.