Unexpected hydrophobicity on self-assembled monolayers terminated with two hydrophilic hydroxyl groups

Abstract

An unexpected hydrophobicity with a contact angle of 82° on (OH)2-SAM terminated only with two hydrophilic OH groups was found, which is attributed to the formation of a hexagonal-ice-like H-bonding structure in the OH matrix of (OH)2-SAM.

Unexpectedly resisting protein adsorption on self-assembled monolayers terminated with two hydrophilic hydroxyl groups

“…The model atoms at the other end of the alkyl chains were bound to a (111) facet of a face-centered cubic (FCC) lattice. The packing densities were 4.5 nm À2 and 6.5 nm À2 , corresponding to the hydrophobic and hydrophilic structures in our previous study, 24 respectively. The protein solvated by the SPC/E 25 water molecules was initially placed at 6 Å above the (OH) 2 -SAM.…”

“…It is worth noting that the researchers 23 found that the SAM terminated with only a hydrophilic OH group could resist peptide adsorption among the SAMs terminated with four different hydrophilic and hydrophobic groups (i.e., CH 3 , NH 2 , COOH, and OH), and the hydrophobic CH 3 -terminated SAM did not exhibit resistance to peptide adsorption. It is found that the structure of the hydrophobic SAM 24 itself terminated with only hydrophilic OH groups can significantly improve the performance of resistance to protein adsorption in our current study compared with their results of the OH-terminated SAM resistance to peptide adsorption. Therefore, the hydrophobic OH-terminated SAM is very suitable for resisting protein adsorption in our study.…”

“…Our previous study has demonstrated that these parameters can produce a reasonable wetting phenomenon. 24 These parameters are listed in Table S2 of the ESI †. Each system was equilibrated in the canonical ( NVT ) ensemble using a velocity rescaling thermostat at room temperature for 600 ns.…”

“…However, we note that the OH-terminated SAM itself can form a hexagonal-ice-like H-bond structure in the OH groups, exhibiting unexpected hydrophobicity in our previous study. 24 To answer the question, ‘how does this SAM structure affect resistance to protein adsorption? ', it is necessary to explore the effect of the structure of the OH-terminated SAM itself on resistance to protein adsorption to improve the performance of the SAM resistance to protein adsorption.…”

Factors resisting protein adsorption on hydrophilic/hydrophobic self-assembled monolayers terminated with hydrophilic hydroxyl groups

“…This physical barrier effect was traditional mechanistic explanation for OH-SAM resistance to protein adsorption. However, our previous study [15] found that SAM terminated with only hydrophilic OH groups exhibited different hydrophilic and hydrophobic characteristics at different pack-ing densities. For such structures, is the effect of interfacial water on OH-SAM resistance to protein adsorption consistent?…”