Role of Interfacial Water in Protein Adsorption onto Polymer Brushes as Studied by SFG Spectroscopy and QCM

The adsorption of large biomolecules such as proteins is of high relevance in medicine; adsorbed proteins can initiate undesirable biOlogice reactions such as blood coagulation or immune responses, which adversely affect the human body and the functioning of medical devices. Thus, the suppression of protein adsorption onto material surfaces is essential for medical and biomedical applications. Interfacial water molecules may play a key role in protein adsorption. In this context, in this study, we prepare various types of surfaces (hydrophobic, hydrophilic, anionic, cationic, and zwitterionic) using polymer brushes with different molecular structures. We analyze the adsorption of negatively and positively charged proteins using a quartz crystal microbalance (QCM) to quantitatively investigate protein adsorption onto the polymer brush surfaces. The structure of the interface between the polymer brushes and water media is investigated using sum frequency generation (SFG) spectroscopy. Our comparison of the protein adsorption characteristics with the properties of the interfacial water molecules of each polymer brush indicates that the interfacial water molecules, which strongly interact with polymer brushes, are important for suppressing protein adsorption. The findings can significantly contribute to the functional biomaterial design.