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photostability, low toxicity to DBT cells, high hydrophilicity and
60 functionality ready for bioconjugation, these NIR dendrimers
appear to be promising for biomedical imaging applications. In
addition, QR-G2-COOH appears to be more emissive than QR-
G1-COOH, indicating that increasing dendrimer size is an
effective strategy to improve the emission of the
65 quaterrylenediimide dendrimers. As such, the development of
quaterrylenediimide dendrimers with higher generations is
currently in process.
5
10 Fig. 3. The photostability of QR-G1-COOH, QR-G2-COOH
and ICG in DMSO. Samples were exposed to the ambient light
We thank Dr. Nephi Stella at University of Washington for
providing wild-type mouse malignant astrocytoma DBT cells for
and the change of optical density at absorption maximum 70 the cytotoxicity study. The work was supported by the startup
wavelength was monitored over time. All samples have the initial
absorbance of about 1.2 at the absorption maximum wavelength.
15 The signals were normalized against the values at 0 hour.
fund provided by the Department of Radiology, University of
Pittsburgh.
Notes and references
a Molecular Imaging Laboratory, Department of Radiology, University of
75 Pittsburgh School of Medicine, Pittsburgh, PA 15219, USA. Email:
baim@upmc.edu; Fax:(+1)-412-624-2598; Tel:(+1)-412- 624-2565
b University of Pittsburgh Cancer Institute, Pittsburgh, PA 15232, USA
† Electronic Supplementary Information (ESI) available: [Synthesis and
Characterization]. See DOI: 10.1039/b000000x/
20
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Fig. 4. Cell viability tests of QR-G1-COOH and QR-G2-COOH
on the wt-DBT cell line. Values are presented as means
30 standard deviations.
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of QR-G1-COOH and QR-G2-COOH exhibited no significant
absorbance change. After 3 days of illumination, no significant
absorbance from ICG sample was observed, while QR-G1-
COOH and QR-G2-COOH showed an absorbance change of
35 only 1% and 3%, respectively. Even after being exposed to the
ambient light for 31 days, QR-G1-COOH and QR-G2-COOH
remained strong NIR absorbance of 85% and 77%, respectively.
These data demonstrate that QR-G1-COOH and QR-G2-COOH
are dramatically more photostable than ICG. The remarkable
40 photostability of these dendrimers provides opportunities in long-
term imaging and accurate signal quantification.
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COOH against wild-type mouse malignant astrocytoma DBT
(wt-DBT) cells was investigated using a Hemocytometer-based
45 trypan blue dye exclusion method.25 Fig. 4 shows the cell
viability after incubation with QR-G1-COOH and QR-G2-
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hours. Cell viabilities of more than 97% were observed for both
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comparable to those of the solvent and cell medium control
groups, while only 66.9% live cells were found in the positive
control group (5% DMSO). The cytotoxicity results indicate that
QR-G1-COOH and QR-G2-COOH have low cytotoxicity to
55 DBT cells.
115
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In conclusion, we have developed two polyamide-based
quaterrylenediimide dendrimers with twelve and thirty-six
carboxylic acid groups. With strong NIR absorption, remarkable
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