Mechanical Enhancement and Kinetics Regulation of Fmoc‐Diphenylalanine Hydrogels by Thioflavin T

Abstract

The self‐assembly of peptides is a key direction for fabrication of advanced materials. Novel approaches for fine tuning of macroscopic and microscopic properties of peptide self‐assemblies are of a high demand for constructing biomaterials with desired properties. In this work, while studying the kinetics of the Fmoc‐Diphenylalanine (Fmoc‐FF) dipeptide self‐assembly using the Thioflavin T (ThT) dye, we observed that the presence of ThT strongly modifies structural and mechanical properties of the Fmoc‐FF hydrogel. Notably, the presence of ThT resulted in a tenfold increase of the gelation time and in the formation of short and dense fibers in the hydrogel. As a result of these morphological alteration higher thermal stability, and most important, tenfold increase of the hydrogel rigidity was achieved. Hence, ThT not only slowed the kinetics of the Fmoc‐FF hydrogel formation, but also strongly enhanced its mechanical properties. In this study, we provide a detailed description of the ThT effect on the hydrogel properties and suggest the mechanisms for this phenomenon, paving the way for the novel approach to the control of the peptide hydrogels’ micro‐ and macroscale properties.

Tunable Self-Assembled Peptide Hydrogel Sensor for Pharma Cold Supply Chain

“…It should be noted that there are other ways to decelerate the hydrogelation kinetics: for instance, the presence of the fluorescence dye Thioflavin T may result in a 10-fold increase of the hydrogelation time. 17 Also, the mechanical and kinetic properties of the peptide hydrogel can be synergistically modulated by a multicomponent assembly, e.g., using a 1:1 ratio of Fmoc-FF and Fmoc-pentafluoro-phenylalanine (Fmoc-F5 F). 31 The use of such mixtures also decreases the rate of gelation and can be applied for tuning the parameters of the defrost sensor.…”

“…The mechanism of hydrogel formation deceleration may vary depending of the substances presented in the self-assembly system: for instance, in the case of fluorescence dye Thioflavin T, its presence decreases the interaction energy between the stacked peptides, thus leading to longer lag times and lower growth rates. 17 The presence of the peptide mixture Fmoc-FF + Fmoc-F5 F also decreases the hydrogel formation kinetics, which is explained by the slow diffusion of the building blocks during the process of structural organization into fibers within a viscous solution, as the Fmoc-F5 F solution became very viscous immediately following the dilution in water, whereas the Fmoc-FF solution remained in a liquid state for several minutes. 31 To explain why the presence of glycerol prolongs the sensor hydrogelation time, the structural changes in the Fmoc-FF in water and Fmoc-FF in glycerol were examined using fluorescence lifetime imaging microscopy (FLIM).…”

“…Several stages could be identified during Fmoc-FF self-assembly in water as well as in glycerol using a low concentration of the ThT dye as a probe. 17 First, amorphous spherical aggregates were formed (Figure 3(A(I)), see figures for water, lag phase). This process corresponds to the initial region of the sigmoidal curve of the system's turbidity over time observed during hydrogel formation (Figure 2B).…”

“…14−16 Importantly, the optical properties of peptide-based hydrogels during hydrogelation exhibit dramatic changes and strongly depend on the self-assembly kinetics and morphology of the formed nanostructures. 17,18 Aromatic moieties such as fluorenylmethoxycarbonyl (Fmoc) can promote the self-assembly of peptides into a hydrogel in aqueous environments, as the aromatic group contribution includes both π−π stacking and hydrophobic interactions. 1 Self-assembly of these peptides takes place because of the multiple noncovalent interactions, which allow the monomeric building blocks to self-assemble into ordered fibrous structures that later entangle and interact with one another to form the three-dimensional hydrogel matrix.…”