The interactions between proteins and solid surfaces govern important processes in bioengineering, biosensing, and bioseparation. Next-generation devices for healthcare applications require further development in materials for protein-resistant interfaces, biosensor designs with increased sensitivity for detecting proteins at low concentrations, and improved stationary phases with controllable properties for separating biological therapeutics.

While much work has been done to measure the factors impacting protein-surface interactions, recent advances in imaging techniques have brought better spatial and temporal resolution. Misiura et al. used single molecule fluorescence microscopy to probe glass surfaces covered with a self-assembled monolayer (SAM).

“This is the first work to study the combination of hydrophobicity, roughness, and electrostatic force effects at the single molecule level,” said author Anastasiia Misiura.

The monolayer can be adjusted to change these parameters, which can impact biological interactions. For example, increasing SAM concentration results in increased hydrophobicity and surface roughness. While the increased surface roughness suppresses protein dynamics, the increased hydrophobicity has the opposite effect.

“Because all these complicated things are happening at different time scales and space scales, you could never separate the mechanistic contributions of each one of those individual effects,” said author Christy Landes. “The real value of single molecule spectroscopy and measuring at these scales is that you can distinguish the contributing factors.”

The team believes understanding and controlling hydrophobicity, roughness, and electrostatic force at the molecular level will allow for the tuning of protein-surface interactions. They plan to explore how antibodies interact with rough and charged surfaces, as the proteins have unexpected properties important for medical research.

Source: “The competing influence of surface roughness, hydrophobicity, and electrostatics on protein dynamics on a self-assembled monolayer,” by Anastasiia Misiura, Chayan Dutta, Wesley Leung, Jorge Zepeda O, Tanguy Terlier, and Christy F. Landes, Journal of Chemical Physics (2022). The article can be accessed at

This paper is part of The Ever-Expanding Optics of Single-Molecules and Nanoparticles Collection, learn more here.