Photoacoustic and Ultrasound Imaging with Nanosized Contrast Agents - Nanotechnology for Biomedical Imaging and Diagnostics - page 298

(a)

Targeting
peptide

(c)

SWNT-ICG-RGD

O

O

Photograph

Tumor

C=O

HN
O
O

O-P=O

100

O

O

Preinjection

CH 3 H 2 C

H 2 C CH 3

N +

N

(CH 2 ) 4
SO -

(H 2 C) 4

SO 2 Na

SWNT-ICG

2 h
postinjection

(b)

Plain SWNT
SWNT-ICG-RAD

2

SWNT-ICG-RCD

1.5

skin

20X Substraction

image

1

0.5

0

3 mm

0 400

600 800 1000 1200

Wavelength (nm)

figure 10.9 In vivo photoacoustic (PA) imaging of U87 tumors in living mice using single-
walled carbon nanotube-indocyanine green conjugated with rgd peptide (SWCnT-ICg-rgd).
(a) Schematic of a SWCnT-ICg particle. (b) optical spectra of plain SWCnT and SWCnT-
ICg-rgd. (c) In vivo PA images of U87 tumors in living mice acquired with SWCnT-ICg-
rgd injection. (reprinted with permission from ref. [137]. © American Chemical Society.)

shown in Figure 10.9b. When SWCnTs were conjugated with ICg, the optical
absorption was enhanced by 20-fold. The in vivo PA sensitivity of SWCnT-ICg
(~0.8 nM) was approximately 100 times higher than that of plain SWCnTs (~100 nM).
A subcutaneous U87 brain tumor xenograft was photoacoustically imaged after
injection of SWCnT-ICg-rgd, which targeted α v β 3 integrins overexpressed in the
tumor (Fig. 10.9c). The PA signal was enhanced by greater than 300% with SWCnT-
ICg-rgd injection, whereas the improvement was limited to only 80% with
SWCnT-rgd injection under the same injection dose.

10.5.4 dual-modality Photoacoustic and ultrasound
contrast agents

due to the hybrid nature of PAT (i.e., combination of light and US), PAT has been
easily integrated with existing US imaging systems [138, 139]. The combined system
shared the same US detectors. At the same time, the dual-modality contrast agents for
PA and US imaging have been investigated to improve the sensitivity and specificity.
Microbubbles filled with gas are successfully adapted in clinical practice as US