Multivalent Ion-Activated Protein Adsorption Reflecting Bulk Reentrant Behavior

TL;DR

This study investigates how multivalent ions influence the adsorption of negatively charged proteins at solid-liquid interfaces, revealing a reentrant behavior linked to bulk phase transitions, modeled through ion-activated patchy interactions.

Contribution

It demonstrates the control of protein adsorption via multivalent ions and connects bulk phase behavior with interfacial phenomena using a density functional theory model.

Findings

Reentrant protein adsorption behavior observed with salt concentration.

Bulk phase behavior correlates with interfacial adsorption patterns.

Model successfully explains ion-activated patchy interactions at interfaces.

Abstract

Protein adsorption at the solid-liquid interface is an important phenomenon that often can be observed as a first step in biological processes. Despite its inherent importance, still relatively little is known about the underlying microscopic mechanisms. Here, using multivalent ions, we demonstrate the control of the interactions and the corresponding adsorption of net-negatively charged proteins (bovine serum albumin) at a solid-liquid interface. This is demonstrated by ellipsometry and corroborated by neutron reflectivity and quartz-crystal microbalance experiments. We show that the reentrant condensation observed within the rich bulk phase behavior of the system featuring a nonmonotonic dependence of the second virial cofficient on salt concentration c_s is reflected in an intriguing way in the protein adsorption d(c_s) at the interface. Our findings are successfully described and understood by a model of ion-activated patchy interactions within the framework of classical density functional theory. In addition to the general challenge of connecting bulk and interface behavior, our work has implications for, inter alia, nucleation at interfaces.