Biomedical Engineering Reference
In-Depth Information
with a PT effect [81]. The authors also stated that incubation of sWNTs with Icg,
a strong and stable binding of Icg molecules to the surface of the sWNT occurs, leads
to a approximately 20-fold increase in the optical absorption of the sWNT [81].
While small optical dyes such as Icg have lower optical absorption absorptivity
than sWNTs, they are also significantly smaller in size. The absorption coefficient
of Icg divided by its molecular weight, however, is higher than that of sWNTs and
significantly greater than that of gold-based nanoparticles. Thus, while Icg exhibits 30
times and 5 × 10
3
times lower optical absorbance than sWNTs and gold nanorods,
respectively, it is also 220 times and 45 × 10
6
times lighter than sWNTs and nanorods.
Hence, on an absorbance-per-weight measure, Icg is approximately 7 times more effi-
cient than sWNT and approximately 9000 times more efficient than nanorods at absorbing
light [81]. It should be noted that if volume of nanoparticle is considered instead of
molecular weight, gold nanorods will be more efficient in absorbing than sWNTs.
sWNTs conjugated with RgD peptide through phospholipid-polyethylene glycol-
amine (PL-Peg-NH
2
) linker with long (5400 Da) Peg chains were also demonstrated
to target αvβ3 in tumors, a vascular integrin associated with tumor angiogenesis [82].
This included testing the PA signal stability when introduced to serum, cell uptake and
photobleaching, and characterizing the signal-concentration curve. In another report
[88], the sensitivity of Icg-modified sWNT-RgD in living mice has been estimated
to be 170 pm. This represents a significant improvement in sensitivity of over 300-fold
as compared with plain sWNT-RgD. This improvement in sensitivity was primarily
due to the higher optical absorption induced by Icg, as well as the ability to shift the
laser excitation wavelength from 690 to 780 nm (the absorption spectrum maximum of
sWNT-Icg-RgD), at which the background tissue absorption is significantly reduced.
The combination of cNTs and their conjugates is well suited for theranostic appli-
cations and can be exploited for diagnostic purposes with OA imaging and drug
delivery in cancer treatment [93, 94]. control for local concentration and biodistribu-
tion of sWNT in these conditions is important, and the nanoparticle concentrations
could be monitored with a 3D OAT
in vivo
, as demonstrated in figure 5.9 by the
Before
3 days
Before
3 days
Before
3 days
1
S
S
S
L
L
S
L
L
0
K
K
K
K
Back
Right
10 mm
Left
figure 5.9
Three-dimensional OA images of a mouse before and 3 days after sWNT
injection. The grayscale intensity is the same for all images. Dorsoventral, left mediolateral,
and right mediolateral views are shown. s, L, and K show locations of the spleen, liver, and
kidney, respectively. (Adopted with permission from Ref. [95]. © sPIe-International society
for Optical engineers.)
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