“9.61x6.69” b2815 Tissue Engineering and Nanotheranostics
Multifunctional Nanomaterials for Cancer Theranostics 245
than in normal tissues, it is highly overexpressed in several aggressive
cancer cell lines including leukemia, ovarian, colon, mastocytoma,
lung, renal, and breast cancer cells. The αvβ 3 integrin, highly
expressed on neovascular endothelial cells but poorly expressed in
resting endothelial cells and most normal organs, is important in the
calcium dependent signaling pathway leading to endothelial cell
migration.260,261 Cyclic or linear derivatives of RGD (Arg–Gly–Asp)
oligopeptides are the most studied peptides.^2 62–267 In addition, there
are many small molecular compounds for cholecystokin receptor, tro
pomyosin receptor kinase, glucose transport system, estrogen recep
tor, progesterone receptor, androgen receptor that will not be
discussed here.
5. Imaging Techniques
Imaging technology is an important tool for the diagnosis and prog
nosis of the disease. The combination of nanomaterials and imaging
technology has become a hot research field in nanomedicine, which
leads to the development of nanotheranostics. Major imaging tech
niques are described below:
5.1. Fluorescence Imaging
Fluorescence imaging is one of the most powerful noninvasive imag
ing techniques that have been widely performed for the detection of
disease states.268–272 The advantages of fluorescence imaging include
high sensitivity, realtime observation, lack of nonionizing radiation,
ability to image the spectrum from visible to nearinfrared. Moreover,
it is inexpensive to detect the photons. The disadvantages are their
poor tissue penetration, susceptibility to noise due to scattering, and
potential autofluorescence. An ideal fluorescent probe used for nano
diagnosis is expected to show high fluorescence quantum yields,
robust photostability, excellent dispersibility in biological conditions,
high resistance to degradation in biological systems and favorable
biocompatibility. The fluorescent probes include organic dyes, semi
conductor quantum dots, organic–inorganic nanohybrids.273–277 For
