Use of pH Gradients in Responsive Polymer Hydrogels for the Separation and Localization of Proteins from Binary Mixtures

Abstract

Using a molecular-level equilibrium theory where proteins are described using their crystallographic structure, we have studied protein adsorption from binary and ternary mixtures of myoglobin, lysozyme, and cytochrome c to poly­(methacrylic acid) hydrogel films. The pH gradients these films induce can lead to selective protein adsorption, where the solution pH provides a sensible dial to externally control protein separation. Changing the chemical composition of the polymer network, adding either another acidic or a neutral comonomer, allows for protein localization to controlled spatial regions of the film with nanometer resolution. As pH-sensitive polymer hydrogels are promising candidates for smart, responsive biomaterials, understanding the complexity of competitive protein adsorption is essential. In this work, we highlight the decisive role of amino acid protonation in selective protein adsorption. We present conditions such that the hydrogel film will selectively incorporate the more weakly charged protein, provided that it requires less work to protonate its amino acids.

Stimuli responsive dynamic transformations in supramolecular gels

“…Similarly, a change of pH can also induce a diffusion controlled transient gradient in pH during gel-to-gel transitions and thereby integrate transient heterogeneous structures. 234 Longo and co-workers utilized pH gradients to facilitate protein adsorption to a polymer hydrogel film from binary and ternary mixtures of myoglobin, lysozyme and cytochrome c. 462 Change of pH can also be utilized to control the degree of ion-ligand coordination as well as distribution of metal ions in pH responsive metallogels (discussed in Section 3(iii)) and thereby enables to control inhomogeneity in crosslink density, rheological moduli, and responsive properties in gradient hydrogel networks. However, most of the chemical stimuli responsive gradient gels are composed of polymeric backbone.…”

Triggering doxorubicin release from responsive hydrogel films by polyamine uptake

“…To study this system we apply a molecular theory that was recently developed to investigate absorption to such pH-responsive hydrogel films from protein mixtures 28,29 . Our approach is based on the work of Szleifer and collaborators to study the behavior of grafted weak polyelectrolyte layers 30,31 .…”

“…Next, we will present a concise description of the theory with emphasis in the molecular model introduced to describe doxorubicin, putrescine, spermidine and spermine. A full description of this molecular model can be found in our previous work 28 .…”

Theoretical Modeling of Chemical Equilibrium in Weak Polyelectrolyte Layers on Curved Nanosystems

“…The contribution of charge regulation showed to be insensitive to protein orientation under all conditions. MT calculations were also employed to study the effects of charge regulation on protein adsorption in pH-responsive hydrogels [ 139 , 140 ].…”