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

Gelation of a Pentapeptide in Alcohols

Properties of solvents such as polarity and H-bond-forming ability are critical for the formation of an organogel and have a significant impact on the gel behavior, as solvents are the majority of organogel systems. However, so far, there is still a lack of systematic studies regarding the effects of molecular structures of solvents on the characteristics of organogels. Motivated by revealing such a relationship, in this paper, we studied the morphologies of assemblies, gelation behaviors, and secondary structures of a pentapeptide termed EAF-5 in a wide variety of alcohols. The side chains and lengths of carbon chains of the solvent molecules were found to play a critical role in the self-assembly and gelation of EAF-5. EAF-5 was capable of self-assembling into fibers and entangling into a network in alcohols including ethanol, propanol, butanol, n-pentanol, and n-hexanol, which further immobilized the corresponding alcohols to form gels. In these organogels, increasing β-sheet secondary structures of the peptides were formed by introducing side chains and extending the length of primary alcohol molecules. We hypothesized that alcohol molecules with extended lengths and side chains reduced the gelator-solvent interactions and promoted the gelator-gelator interactions, resulting in the self-assembly of EAF-5 into fibril structures and development of gels. These findings provide a new sight into the interactions between gelators and solvents and are helpful for designing peptide-based organogelators.

Engineering hydrogels by soaking: from mechanical strengthening to environmental adaptation

The soaking strategy could not only strengthen hydrogels with superior mechanical properties but also provide the hydrogels with environmentally adapting properties.