Counterion-Specific Protein Adsorption on Polyelectrolyte Brushes

Protein adsorption is an important issue in biorelated fields. We have investigated the protein adsorption on the poly(ionic liquid) (PIL) brushes in the presence of different types of counterions. The protein adsorption is driven by a decrease in osmotic pressure within the brushes with an increase in entropy via the release of counterions. Our study demonstrates that counterion specificity has a significant influence on protein adsorption on the PIL brushes. There have been two different regimes for counterion-specific protein adsorption. When the released counterions cannot bind to the protein surface, the counterion-specific protein adsorption is dominated by the ion-specific counterion condensation within the PIL brushes. If the released counterions can bind to the protein surface, then counterion-specific protein adsorption is dominated by the ion-specific rebinding of released counterions on the protein surface. This work opens up a new opportunity for controlling protein adsorption on polyelectrolyte brushes.