9 Aptamers for the Diagnosis of Malign Tumors
261
through the positive-ion mode of an Autoflex III LDI TOF-MS [131] (Fig. 9.8b).
These results are consistent with those obtained through IHC. However, only highly
abundant targets could be identified through the LDI-MSI technique, which makes
it important for using this approach combined with in vivo imaging to provide more
valuable clinical information [132].
9.6 In Vivo Molecular Imaging
In vivo molecular imaging is a major non-invasive strategy, and strongly pushes the
development of cancer diagnosis and medical treatment evaluation. Comparing with
in vitro analysis, the in vivo molecular imaging technique requires biocompatible
probes with good tissue penetration, and the methods for signal amplification [133].
Aptamers have several advantages as better tissue penetration capacity, low immunogenicity, and biocompatible nature, proving a huge potential for in vivo molecular
imaging. Recently, many studies reported the utilization of aptamers for in vivo
imaging of tumor molecular biomarkers through a variety of imaging techniques,
such as fluorescence imaging, MRI, SPECT, PET, CT, and photoacoustic imaging.
In this section, several cancer-targeted aptamer-based strategies for in vivo imaging
will be discussed.
9.6.1 Fluorescence Imaging
Fluorescence is the most common technique of aptamer-based in vivo imaging, for its
high sensitivity and flexible design. The most adapted fluorophore includes diverse
organic dyes, and several novel luminescent nanomaterials.
DNA aptamer against Ramos cells (B cells lymphoma cancer cells) labeled with
an organic Cy5 dye was used to constitute a cancer cell-type-specific probe(Cy5TD05). The efficacy of Cy5-TD05for in vivo imaging was observed in subcutaneously xenografted nude mice, showing the accumulation of Cy5-TD05 within
engrafted tumor regions and a high signal-to-background ratio as 115.50 [134].
Similarly, the A549 cells (lung carcinoma cells)-targeting DNA aptamers were
labeled with Cy5 dye to construct Cy5-S6 probe for in vivo imaging of tumor,
resulting in tumor-specific accumulation and significant fluorescence signal. The
same strategy was also effective to other two cancer cell-targeting DNA aptamers
against Bel-7404 and SMMC-7721 liver carcinoma cells respectively [135]. Because
of minimal absorption, reduced scattering, and negligible autofluorescence, nearinfrared imaging performs a high signal-to-noise ratio, high resolution, and predominant tissue penetration capability for in vivo imaging. For example, aPSMA (prostatespecific membrane antigen)-targeting RNA aptamer (A9g) was labeled with NIR
dye (IRDye 800CW) for constructing the smart drug for prostate cancer (PC). This
NIR aptamer-based drug can target the PC-3 tumor cells and inhibit the enzymatic
261
through the positive-ion mode of an Autoflex III LDI TOF-MS [131] (Fig. 9.8b).
These results are consistent with those obtained through IHC. However, only highly
abundant targets could be identified through the LDI-MSI technique, which makes
it important for using this approach combined with in vivo imaging to provide more
valuable clinical information [132].
9.6 In Vivo Molecular Imaging
In vivo molecular imaging is a major non-invasive strategy, and strongly pushes the
development of cancer diagnosis and medical treatment evaluation. Comparing with
in vitro analysis, the in vivo molecular imaging technique requires biocompatible
probes with good tissue penetration, and the methods for signal amplification [133].
Aptamers have several advantages as better tissue penetration capacity, low immunogenicity, and biocompatible nature, proving a huge potential for in vivo molecular
imaging. Recently, many studies reported the utilization of aptamers for in vivo
imaging of tumor molecular biomarkers through a variety of imaging techniques,
such as fluorescence imaging, MRI, SPECT, PET, CT, and photoacoustic imaging.
In this section, several cancer-targeted aptamer-based strategies for in vivo imaging
will be discussed.
9.6.1 Fluorescence Imaging
Fluorescence is the most common technique of aptamer-based in vivo imaging, for its
high sensitivity and flexible design. The most adapted fluorophore includes diverse
organic dyes, and several novel luminescent nanomaterials.
DNA aptamer against Ramos cells (B cells lymphoma cancer cells) labeled with
an organic Cy5 dye was used to constitute a cancer cell-type-specific probe(Cy5TD05). The efficacy of Cy5-TD05for in vivo imaging was observed in subcutaneously xenografted nude mice, showing the accumulation of Cy5-TD05 within
engrafted tumor regions and a high signal-to-background ratio as 115.50 [134].
Similarly, the A549 cells (lung carcinoma cells)-targeting DNA aptamers were
labeled with Cy5 dye to construct Cy5-S6 probe for in vivo imaging of tumor,
resulting in tumor-specific accumulation and significant fluorescence signal. The
same strategy was also effective to other two cancer cell-targeting DNA aptamers
against Bel-7404 and SMMC-7721 liver carcinoma cells respectively [135]. Because
of minimal absorption, reduced scattering, and negligible autofluorescence, nearinfrared imaging performs a high signal-to-noise ratio, high resolution, and predominant tissue penetration capability for in vivo imaging. For example, aPSMA (prostatespecific membrane antigen)-targeting RNA aptamer (A9g) was labeled with NIR
dye (IRDye 800CW) for constructing the smart drug for prostate cancer (PC). This
NIR aptamer-based drug can target the PC-3 tumor cells and inhibit the enzymatic