b2815 Tissue Engineering and Nanotheranostics “9.61x6.69”
246 Tissue Engineering and Nanotheranostics
example, Zhan et al. utilized targeting fibronectins PEG–PLA
nanoparticles with a near infrared fluorescent dye (DiR) loaded with
PTX as a theranostic agent. This system was able to selectively target,
treat, and image brain tumors in vivo.^278 Kong et al. developed
ribonucleaseA encapsulated PbS quantum dots which emit in the
second nearinfrared biological window for ultrasensitive fluorescence
in vivo imaging. The result showed the prepared quantum dots with
high Phi(f) (similar to 17.3%) and peak emission at 4300 nm ensure
deep optical penetration to muscle tissues (up to 1.5 cm) and excel
lent imaging contrast at an extremely low threshold dose similar to
5.2 pmol per mouse.^279 Gianotti et al. developed hybrid preparation
by loading highly fluorescent dyes of indocyanine inside the pores of
MSNs.^280 Uniform monomeric existence of dye inside pores was indi
cated under diluted dye concentrations. The formation was observed
in high concentrations of the dye from the hybrid. In vitro fluores
cence bioimaging of this hybrid was demonstrated in mammalian
cancer cells.^280
5.2. Photoacoustic Imaging
Photoacoustic imaging, or namely optoacoustic imaging, unlike con
ventional optical imaging methods, is insensitive to photon scatter
ing within biological tissue and, makes highresolution optical
visualization deep within tissue possible.281–286 The principle of pho
toacoustic imaging is that the endogenous molecules and tissues
absorb laser energy to generate wave sounds, which are recorded by
ultrasound detectors and converted to image. However, due to tissue
scattering and negative influence of some endogenous agents, low
optical absorption by tissues limits the benefits of photoacoustic
imaging. In order to solve the problem for the enhancement of pho
toacoustic signals, nanoparticlebased contrast agents with high NIR
absorption were applied. Among various nanomaterials as contrast
agents for photoacoustic imaging, goldbased nanomaterials, CNTs
and upconversion nanoparticles have been explored extensively for
photoacoustic imaging applications.64,287–294 For example, Cheng et
al. developed Prussian blue nanocubes as theranostic agents for
