OVERVIEW ON THE MAJOR RESEARCH ACTIVITIES ON CARBON NANOTUBES BEING DONE IN AMERICA, EUROPE AND ASIA - Carbon Nanotubes: From Bench Chemistry to Promising Biomedical Applications - page 259

CD4 and/or coreceptors CXCR4/CCR5 can block HIV entry and thus reduce
infection. To that purpose, SWCNTs were irst reacted with a bifunctional
linker, sulphosuccinimidyl 6-(3'-[2-pyridyldithio]-propionamido) hexanoate
(sulpho-LC-SPDP) and then conjugated with thiolated siRNA anti-CXCR4 through
a cleavable disulphide bond (Fig. 9.12). Once transported into cells via
endocytosis, siRNA was released from SWCNTs by sulphide cleavage and
then bound to CXCR4 mRNA to induce gene silencing.

Figure 9.12 A scheme showing siRNA conjugation to SWCNTs through a disulphide
bond. PL-PEG2000-amine-functionalised SWCNTs are activated by the sulpho-LC-
SPDP bifunctional linker. The pyridyl disulphide group can then be coupled to thiolated
siRNA to create a disulphide linkage through a thiol exchange reaction. Reproduced
from Liu et al . 70 with permission. See also Colour Insert.

9.2.2.2 CNTs for bioimaging and biosensing

The same research group has also developed an interesting microarray
for sensitive protein detection, based on functionalised, macromolecular
SWCNTs as multicolour Raman labels. 71 SWCNTs have intrinsic electronic and
spectroscopic properties that render them ideal for surface-enhanced Raman
scattering (SERC). The main advantage of this technique is that SWCNTs
provide multiple-colour SWCNT Raman labels, while requiring only a single
excitation source. Moreover, the SWCNT Raman excitation and scattering
photons are in the NIR region, which is the most transparent optical window
for biological species both in vitro and in vivo . More precisely, SWCNTs were
functionalised with PL-PEG chains, to which a secondary antibody, goat anti-