Influence of Salt and pH on the Adsorption of Fibrinogen and Lysozyme to Self-Assembled Monolayers Using a Surface Plasmon Resonance Sensor

This work examines protein adsorption on surfaces in an attempt to provide a fundamental understanding of the molecular-level mechanism for protein interactions with biomaterials. Carboxylic acid, amine, and hydroxyl terminated self-assembled monolayers (SAMs) are used to model negatively, positively, and hydrophilic/neutrally charged surfaces, respectively. The adsorption of fibrinogen and lysozyme on these SAM surfaces under different ionic strengths and pH values is studied using a surface plasmon resonance (SPR) sensor. It is shown that variations in ionic strength have little effect on the adsorbed amount of fibrinogen and lysozyme on these SAMs at a fixed pH value. Analysis of the effect of pH on protein adsorption at a fixed ionic strength shows that charge interactions are a significant component of protein adsorption. These studies provide insights into the role of hydrogen bonding and electrostatic interactions in protein adsorption.