In their report, Ohta et al. described that single-walled carbon nanotubes (SWCNTs) with superior dispersion stability in water are expected to serve as a good drug delivery system carrier in various biomedical applications. The SWCNTs composites with designed peptide having polyethylene glycol (PEG) modification were further conjugated with mitomycin C (MMC) for achieving its controlled release. The obtained conjugate of SWCNTs composites and MMC showed good dispersion stability even under physiological conditions. The release of MMC followed the first-order kinetics with half-lives of 32.2-256.2 hours being accelerated by the pH increase. In addition, the MMC conjugate demonstrated the antitumor activity with delayed growth inhibition comparing with free MMC.