Peptide-Directed Formation of Gels

Natural extracellular matrices in vivo consist of various protein fibrils and fibers, interwoven within a hydrated network of glycosaminoglycan chains and may require less than 1% solid materials to form mechanically robust 

Tonegawa et al. (2004) created a cationic polylysine with a tetrapeptide end sequence (glycine-tyrosine-glycine-lysine), which is a motif common to the consensus sequences of mussel adhesive proteins. They then cross-linked this with the anionic polysaccharide, gellan, enzymatically. The polyionic complexation between the cationic peptide and the anionic polysaccharide formed a hybrid fiber at the aqueous solution interface that, when cross-linked, mimicked the byssus gel that marine mussels use to adhere to surfaces, despite the presence of water and salt. 

Although such nanotubes form an interesting structure with potential for exterior functionalization, they are currently limited to passive transport/ release of molecules in the interior. Future work may focus on using non-canonical amino acids to impart functionalizable interior surfaces to allow orthogonal functionalization of the interior and exterior surfaces (ten Cate et al., 2006). 

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