Mechanisms by Which Organic Solvent Exchange Transforms Responsive Pure Protein Hydrogels into Responsive Organogels

Abstract

Responsive pure protein organogel sensors and catalysts are fabricated by replacing the aqueous mobile phase of protein hydrogels with pure ethylene glycol (EG). Exchanging water for EG causes irreversible volume phase transitions (VPT) in bovine serum albumin (BSA) polymers; however, BSA hydrogel and organogel sensors show similar volume responses to protein–ligand binding. This work elucidates the mechanisms involved in this enabling irreversible VPT by examining the protein secondary structure, hydration, and protein polymer morphology. Organogel proteins retain their native activity because their secondary structure and hydration shell are relatively unperturbed by the EG exchange. Conversely, the decreasing solvent quality initiates polymer phase separation to minimize the BSA polymer surface area exposed to EG, thus decreasing distances between BSA polymer strands. These protein polymer morphology changes promote interprotein interactions between BSA polymer strands, which increase the effective polymer cross-link density and prevent organogel swelling as the mobile phase is exchanged back to water.

Gelation of a Pentapeptide in Alcohols

“…The derivatives of amino acids and short peptides are attractive LMWOs owing to their good biocompatibility, simple preparation, and easy access. − Short peptides are particularly versatile building blocks of LMWOs, which have extensive applications in different fields ranging from materials, physics to biomedicine. , For example, it was reported that peptide-based organogels exhibited high activity in catalyzing asymmetric reactions . Peptide organogels coassembled with carbon nanomaterials were found to facilitate the reduction of benzoic acid to benzyl alcohol by NaBH 4 .…”