Investigation of the influence of surface defects on peptide adsorption onto carbon nanotubes

The number of possible applications that interface carbon nanotubes with biological systems is rapidly growing, and with these advances comes a need for characterisation of such interfaces. Molecular simulation is one such approach, and many recent examples exist where simulation has been used to investigate the atomic-scale details of the interface between biomolecules and carbon nanotubes (CNTs). However, these studies have been confined to the realm of pristine CNTs. Here, we build on our previous work and use molecular simulation to consider the adsorption on to defective CNTs of peptide sequences known to bind to the CNT surface [Wang et al., Nat. Mater., 2003, 2, 196]. Two types of idealised chemical defects are considered, along with two different distributions of these defects on the CNT surface. We find that the densely-packed defect distribution yields relatively little engagement with the peptides. Spreading the defects out along the nanotube increases the degree of contact with the peptide, without affecting the binding strength of the peptide-CNT interface in most cases. Both types of defect tend to act more as physical barriers to peptide mobility than as a source of attractive interactions. The resulting physical confinement of the peptide did not affect all sequences in the same way; two of the four sequences were found to be more sensitive to the presence of defects. This study has implications for the practical usage of CNTs in a wide range of biological contexts, where well-dispersed, functionalised nanotubes are required.