Polymer-wrapped peptide nanotubes: peptide-grafted polymer mass impacts length and diameter.

The external structure of polymer-wrapped nanotubes resembles that of small nanorods with a core/shell morphology, where the core consists of a self-assembled peptide nanotube surrounded by a soft polymeric coat. The length and the diameter of the nanorods are investigated as a function of the molar mass of the peptide-grafted macromolecules by statistical atomic force microscopy cross-section analysis of dry nanorods adsorbed to a solid substrate. With increasing molar mass of the grafted polymers, the height increases from less than 2 nm up to more than 10 nm, and the length of the objects decreases from about 120 nm to about 30 nm. Additional analysis suggests excluded volume interactions between the highly grafted polymer chains on the surface of the peptide nanotube to be the major driving force for the shortening of the nanotubes. The present findings may provide a base for fine tuning the dimensions of such novel bioinspired nanomaterials.