Sequence Adaptive Peptide-Polysaccharide Nanostructures by Biocatalytic Self-Assembly.

Coassembly of peptides and polysaccharides can give rise to the formation of nanostructures with tunable morphologies. We show that in situ enzymatic exchange of a dipeptide sequence in aromatic peptide amphiphiles/polysaccharide coassemblies enables dynamic formation and degradation of different nanostructures depending on the nature of the polysaccharide present. This is achieved in a one-pot system composed of Fmoc-cysteic acid (CA) and Fmoc-lysine (K) plus phenylalanine amide (F) in the presence of thermolysin that, through dynamic hydrolysis and amide formation, gives rise to a dynamic peptide library composed of the corresponding Fmoc-dipeptides (CAF and KF). When the cationic polysaccharide chitosan is added to this mixture, selective amplification of the CAF peptide is observed giving rise to formation of nanosheets through coassembly. By contrast, upon addition of anionic heparin, KF is formed that gives rise to a nanotube morphology. The dynamic adaptive potential was demonstrated by sequential morphology changes depending on the sequence of polysaccharide addition. This first demonstration of the ability to access different peptide sequences and nanostructures, depending on the presence of biopolymers, may pave the way to biomaterials that can adapt their structure and function and may be of relevance in the design of materials able to undergo dynamic morphogenesis.