Debundling and selective dispersion of semiconducting single-walled carbon nanotubes (SWNTs) has been demonstrated using a neutral pH water soluble chitosan derivative, N-acetylated chitosan (NACHI), which is synthesized by controlled N-acetylation of chitosan using acetic anhydride. The SWNT-NACHI supernatant solution demonstrated semiconductor-enriched property owing to the preferential adsorption of N-groups of the NACHI on semiconducting nanotubes with a fairly weak charge transfer. The dispersion of nearly individualized SWNTs achieved by surface modification of nanotubes with a biocompatible polymer can be utilized for electronic and biomedical applications such as field effect transistor, biosensor, cell culture medium and SWNT-biomacromolecule hybrid materials. (C) 2010 Elsevier Inc. All rights reserved.