  Biomedical applications of carbon nanotubes have attracted much attention in
recent years. Here, we summarize our previously developed protocols for
functionalization and bioconjugation of single wall carbon nanotubes (SWNTs)
for various biomedical applications including biological imaging, sensing and
drug delivery. Sonication of SWNTs in solutions of phospholipid-polyethylene
glycol (PL-PEG) is our most commonly used protocol of SWNT functionalization.
Compared to other frequently used covalent strategies, our non-covalent
functionalization protocol largely retains the intrinsic optical properties of
SWNTs, which are useful in various biological imaging and sensing applications.
Functionalized SWNTs are conjugated with targeting ligands for specific cell
labeling in vitro or tumor targeting in vivo. Radio labels are introduced for
tracking and imaging of SWNTs in real time in vivo. Moreover, SWNTs can be
conjugated with small interfering RNA (siRNA) or loaded with chemotherapy drugs
for drug delivery. These procedures take various times ranging from one to five
days.
