Selective labeling of single-walled carbon nanotubes using solid binding proteins

Abstract

Robust and simple strategies to noncovalently functionalize single walled carbon nanotubes (SWNT) are of considerable interest for building hybrid nanomaterials and biosensors. Here, we show that fusion of the Car9 and Car15 carbon binding peptides to the C-termini of the sfGFP and mCherry fluorescent protein scaffolds, allows for selective labeling of the ends and sidewalls of SWNT, respectively. By further modifying carbon-binding sfGFP derivatives through the engineering of a gold-binding peptide or a single cysteine residue in a solvent exposed loop that lies opposite to the carbon binding extensions, we further show that it is possible to produce dual material binders supporting the selective conjugation of Au nanoparticles to the ends and sidewalls of nanotubes. The approach described here is generic and should prove useful for controlled and hierarchical assembly of other hybrid materials. It also holds promise for the creation of reconfigurable assemblies through the use of stimuli-responsive protein scaffolds.