The application of single-walled carbon nanotubes (SWCNTs) in the field of biomedicine is becoming an exciting topic
because of their flexible structure and propensity for chemical functionalization. In this assay, a novel noncovalently
functional SWCNTs based on a natural biocompatible polymer chitosan has been developed for tumor cells targeting.
First, SWCNTs were modified by chitosan (CHIT-SWCNT). Second, CHIT-SWCNT was coupled with fluorescein
isothiocyanate (FITC), based on the reaction between the isothiocyanate group of FITC and the primary amino group of
chitosan. Third, the FITC functionalized CHIT-SWCNT was conjugated with folic acid (FA) after activation with
EDC/NHS, based on the reaction between the NHS group of FA and the primary free amino group of chitosan to
construct the functional SWCNT/CHIT conjugate, CHIT-SWCNT-FA. The fluorescence CHIT-SWCNT-FA has been
used to detect tumor cells with confocal microscopy imaging technology. Our experimental results indicate that the novel
CHIT-SWCNT-FA is soluble and stable in PBS, and it can be readily transported inside tumor cells. Combining the
intrinsic properties of carbon nanotubes and the versatility of chitosan, CHIT-SWCNT can be used as potential devices
for targeted drug delivery and tumor cell sensing. The proposed assay could provide a feasible alternative to presently
available functional SWCNTs in biological applications.