Transient binding promotes molecule penetration into mucin hydrogels by enhancing molecular partitioning.

Here, we present a microfluidics chip platform which allows for studying the charge-dependent transport of molecules across the interface of acidic mucin gels. With this setup, we demonstrate a selective accumulation of molecules at the liquid/gel interface of mucin hydrogels that occurs as a function of the molecule charge: this phenomenon is strongly pronounced for cationic molecules, weakly pronounced for anionic molecules and absent for neutral molecules. We suggest that molecular transport into and across the gel depends on two main factors, i.