DATA: THE NEW CORPORATE RESOURCE - Carbon Nanotubes: From Bench Chemistry to Promising Biomedical Applications - page 8

To assess the stacking motif of LPC micelles onto the CNT sidewalls, atomic
force microscopy (AFM) imaging was utilised. 20 An uneven distribution of
micelles over SWCNT surfaces was observed. The calculated height value for
the uncoated part of the nanostructure was 1.4 ± 0.1 nm, typical of individual
single-walled nanotubes. In sharp contrast, the height value for the coated
region of the nanostructure was ca. 7.4 ± 0.4 nm ( n = 10). The increased
height values can be attributed to the presence of lipid moieties coating the
graphitic surface.
In a recent study, single bilayer membranes of 1-palmitoyl-2-oleoyl- sn -
glycero-3-phosphocholine (POPC) were fused onto a network of hydrophobic
CNTs. By doping the nanotubes to enhance hydrophilicity, it was possible to
create a structure that may act as a nanoporous support for a single lipid
bilayer. 21 Such systems might be used for biomaterials or biosensors.
In another approach, phosphatidylserine (PS)-coated SWCNTs were used
for targeted delivery into macrophages to control their functions, including
inlammatory responses to SWCNTs themselves. More speciically, PS-coated
SWCNTs were able to successfully deliver cytochrome c (cyt c), a pro-apoptotic
death signal, and cause apoptosis in macrophages, emphasizing that non-
covalent modiication of SWCNTs with speciic phospholipid molecules can
be employed for targeted delivery and regulation of phagocytes. 22
Lipid vesicles composed of 1-stearoyl-2-oleoyl- sn -glycero-3-[phospho--
serine] sodium salt (SOPS), 1-palmitoyl-2-oleoyl- sn -glycero-3-phosphocholine
(POPC), and 2-(4,4-diluoro-5-methyl-4-bora-3a,4a-diaza-s-indacene-3-do-
decanoyl)-1-hexadecanoyl- sn -glycero-3-phosphocholine (BODIPY-PC) in the
ratio 75:23:2 (SOPS:POPC:BODIPY-PC) were incubated with polymer-coated
CNTs to produce self-assembled phospholipids into tubular one-dimensional
geometry. Given that lipid membranes can support a large number of
membrane proteins and receptors, f -CNTs with lipid bilayers could further
be employed for utilising membrane proteins in nanodevices. 23
1.4 STABILISATION OF AQUEOUS SUSPENSIONS OF CARBON
NANOTUBES BY SELFASSEMBLING BLOCK COPOLYMERS
Self-assembling polymers offer an ideal system for the non-covalent
stabilisation of hydrophobic molecules in aqueous solutions. They tend to
form micellar systems with a hydrophobic core that can be loaded with the
water-insoluble molecule and a hydrophilic corona that interacts with the
surrounding water. Owing to the hydrophobic nature of CNTs, these micellar
systems are very effective for aqueous stabilisation.