Tuning protein adsorption on charged polyelectrolyte brushes via salinity adjustment

Adsorption and desorption of biomolecules on/from polyelectrolyte surfaces play a critical role in numerous biomedical and engineering applications. Though some weak polyelectrolytes have been developed for protein adsorption and desorption by regulating the salinity and pH, limited reports are available about the regeneration of strong polyelectrolyte surfaces between protein-attractive and protein-repulsive states, which is highly desirable but challenging to realize as it is more difficult to fully release the pre-adsorbed proteins from strong polyelectrolytes due to their permanent charges comparing to weak polyelectrolytes. Here we report a strategy to facilely tune the resistance to nonspecific protein adsorption onto a charged cationic poly([2-(methacryloyloxy)ethyl] trimethylammonium chloride (PMTAC) or anionic Poly(3-sulfopropyl methacrylate potassium salt) (PSPMA)) strong polyelectrolyte brush coating via salinity adjustment. It has been demonstrated that the charged polyelectrolyte coating displays strong adhesion to proteins at low salinity (e.g., 0.1 mM NaCl) but proteinre-pellent property at high salinity (e.g., 1.0 M NaCl). The adsorbed proteins on the strong polyelectrolyte coatings under low salinity condition could be readily removed via rinsing with high-salinity water, demonstrating the excellent surface regeneration capability.