Probing the Surface Hydration of Nonfouling Zwitterionic and PEG Materials in Contact with Proteins

Abstract

Zwitterionic polymers and poly(ethylene glycol) (PEG) have been reported as promising nonfouling materials, and strong surface hydration has been proposed as a significant contributor to the nonfouling mechanism. Better understanding of the similarity and difference between these two types of materials in terms of hydration and protein interaction will benefit the design of new and effective nonfouling materials. In this study, sum frequency generation (SFG) vibrational spectroscopy was applied for in situ and real-time assessment of the surface hydration of the sulfobetaine methacrylate (SBMA) and oligo(ethylene glycol) methacrylate (OEGMA) polymer brushes, denoted as pSBMA and pOEGMA, in contact with proteins. Whereas a majority of strongly hydrogen-bonded water was observed at both pSBMA and pOEGMA surfaces, upon contact with proteins, the surface hydration of pSBMA remained unaffected, but the water ordering at the pOEGMA surface was disturbed. The effects of free sulfobetaine, free PEG chains with two different molecular weights, and PEG coated gold nanoparticles on the surface hydration of proteins were investigated. The results indicated that free sulfobetaine could strengthen the protein hydration layer, but free PEG chains greatly disrupt the protein hydration layer and likely directly interact with the protein molecules. In contrast to free PEG, the PEG chains anchored on the nanoparticles behave similarly to the pOEGMA surface and could induce strong hydrogen bonding of the water molecules at the protein surfaces.

Repelling and ordering: the influence of poly(ethylene glycol) on protein adsorption

“…[27][28][29] In the past SFG spectroscopy has frequently been used to investigate the hydration of PEGylated surfaces in presence or absence of proteins in the subphase. [30][31][32][33][34][35][36][37] Moreover, there are several in situ studies probing the water structure or protein backbone in the amide I region after adsorption on hydrophobic or hydrophilic surfaces. 28,[38][39][40][41][42][43][44] Understanding the interaction of proteins with PEGylated surfaces plays an important role e.g.…”

Transport properties of small molecules in zwitterionic polymers

“…The zwitterionic polymers show water sorption ( v W ) similar to XLPEGDA, indicating that the zwitterionic polymers are comparable to the PEG‐containing materials in terms of hydrophilicity. This result also corroborates with the observation that the better antifouling properties in zwitterionic polymers than nonion‐containing PEG‐based materials are due to the amphiphilic nature in PEG that has nonspecific hydrophobic interactions with foulants, instead of more water layers bound by the zwitterionic polymers.…”

“…Increasing the zwitterionic monomer content has two effects on the polymers: higher content of ionic groups that are expected to have higher affinity with water, and lower crosslinking density that is expected to increase the water sorption . To decouple these two effects, the water sorption in the zwitterionic polymers is compared with that of XLPEGDA prepared from prepolymer solutions containing PEGDA and H 2 O, as shown in Figure (b).…”

Heparin-functionalized polymer graft surface eluting MK2 inhibitory peptide to improve hemocompatibility and anti-neointimal activity

“…The previous studies demonstrated that the negatively charged groups (SO 3 - and COO − ) in heparin reduced absorption of albumin (isoelectric point; PI = 4.8) and fibrinogen (PI = 5.5) proteins by electrostatic repulsion effect, and the non- fouling degree against protein absorption was dependent on the surface heparin density [44]. In addition, the hydrophilic polymer-bound surface can also serve as a physical barrier against protein/platelet absorption through hydrogen bond-induced surface hydration [45, 46]. …”