Controlling supramolecular filament chirality of hydrogel by co-assembly of enantiomeric aromatic peptides.

Supramolecular chirality plays an indispensable role in living and synthetic systems. However, the generation and control of filament chirality in the supramolecular hydrogel of short peptides remains challenging. In this work, as the first example, we report that the heterodimerization of the enantiomeric mixture controls the alignment, chirality, and stiffness of fibrous hydrogels formed by aromatic building blocks. The properties of the resulting racemic hydrogel could not be achieved by either pure enantiomer. Cryo-EM images indicate that the mixture of L and D enantiomers forms chiral nanofibers, the percentage of which can be readily controlled through stoichiometric co-assembly of heterochiral enantiomers. 2D NOESY NMR and diffusion-ordered NMR spectroscopy reveal that heterodimerization of enantiomers plays a crucial role in the formation of chiral nanofibers. Further mechanistic studies unravel the mechanism of supramolecular chirality formation in this two-component system. Molecular dynamics simulations confirm that the intermolecular hydrogen bond and π-π interaction of heterodimers play important roles in forming a chiral hydrogel. Furthermore, regulation of the adhesion and morphology of mammalian cells is achieved by tuning the relative ratio of L and D enantiomers at the same concentration. This work illustrates a novel strategy to control the supramolecular chirality of aromatic peptide hydrogels for materials science.