  Biological systems are known to be highly transparent to 700-1100nm
near-infrared (NIR) light. It is shown here that the strong optical absorbance
of single-walled carbon nanotubes (SWNTs) in this special spectral window, an
intrinsic property of SWNTs, can be utilized for optical stimulation of
nanotubes inside living cells to afford multifunctional nanotube biological
transporters. For oligonucleotides transported inside living cells by
nanotubes, the oligos can translocate into cell nucleus upon endosomal rupture
triggered by NIR laser pulses. Continuous NIR radiation can cause cell death
due to excessive local heating of SWNT in vitro. Selective cancer cell
destruction can be achieved via functionalization of SWNT with a folate moiety,
selective internalization of SWNTs inside cells labeled with folate receptor
tumor-markers and NIR triggered cell death, without harming receptor-free
normal cells. Thus, the transporting capabilities of carbon nanotubes combined
with suitable functionalization chemistry and their intrinsic optical
properties can lead to new classes of novel nanomaterials for drug delivery and
cancer therapy.
