Chemistry Reference
In-Depth Information
3D MIP image of the lungs
3D MIP whole body
image of the mouse
Fig. 22 3D subtraction CT image (measured at 80 and 140 kVp) of mice treated with thiol
lisinopril-coated AuNPs resulting in a specific targeting of the lungs and heart (enlargement of the
lungs and heart area on the right side). Figure reprinted with kind permission from [
115
]
nonionizing radiation relative deep in the tissue without the loss of high spatial
resolution [
126
-
128
]. A temperature increase is induced by short pulses of electro-
magnetic irradiation in the range of strong absorbance. This causes a local increase
in pressure via thermoelastic expansion leading to a generation of acoustic waves
which can be detected with an ultrasound transducer [
125
-
129
].
AuNPs have gained immense interest for PAI since they combine size-
dependent optical properties with a versatile surface chemistry [
130
-
132
]. As
compared to the established group of organic dyes with its standard PAI contrast
agent methylene blue (MB), recent research has demonstrated the superiority of
AuNPs as they show high absorption cross sections combined with a resistance
toward photobleaching. By controlling the particle size and geometry, the extinc-
tion characteristics of AuNPs can be tuned. Numerous groups have found that
nanospheres [
133
-
135
], nanorods [
136
-
143
], nanoshells [
132
], hollow nanospheres
[
127
], and nanocages [
144
-
146
] are eminently suitable.
The first studies with gold nanomaterials were done by Sokolov et al. who
showed that 12 nm AuNPs conjugated with anti-epidermal growth factor receptor
(anti-EGFR) antibodies specifically bound to EGFR proteins that are overexpressed
on the surfaces of cervical cancer cells [
147
]. The receptor-mediated aggregation of
AuNPs causes plasmon coupling of the clustered NPs, leading to an optical redshift
of the plasmon resonances. Based on these results, the group of Emelianov
demonstrated in ex vivo mouse tissue that multiwavelength photoacoustic imaging
can detect cancer with high selectivity and sensitivity based on the plasmon
