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Gene & Protein in Disease Photothermal therapy of pentamethine cyanine

(296.2 mg, 1.14 mmol) in a mixture of acetic anhydride mice bearing human CRC cell HCT-116 xenografts model
(4 mL) and acetic acid (4 mL) were heated at 110°C for 1 h were established as described previously . CY5-664
[23]
under argon. The intermediate 5 (638.8 mg, 1.71 mmol) was was injected into the nude mice bearing HCT-116 tumor
added, and then the mixture was heated at 110°C for another xenografts at a dose of 1 mg/kg through the tail vein and
3 h under argon. The blue solution was poured into 100 mL the NIR fluorescent imaging was carried out from 30 min to
of ethyl acetate. The precipitate was filtered and washed with 96 h after injection using a non-invasive imaging system .
[33]
ethyl acetate. The pure product (181.4 mg) was obtained in The results of fluorescence imaging analysis showed that
30% yield by the purification using reversed-phase (C18) CY5-664 preferentially accumulated in the tumor as
chromatography with CH CN/CH OH (3:1, V/V) as eluent. time elapsed, and the maximum fluorescence intensity
3
3
The structural spectrum of CY5-664 is shown in Figures was obtained at 24 h (Figure 3A). To further confirm the
S2-S4. tumor-targeted accumulation of the compounds, nude
mice were dissected and pivotal organs and tissues, such
Photofading experiments were carried out in the quartz
cuvette (3.5 mL volume) containing a 5×10 M solution as heart, liver, spleen, lung, kidney, and tumor, and were
-6
obtained at 24 h after injection with CY5-664 through tail
of the dye in ultrapure water, where the sample solution vein . The obtained organs and tissues were analyzed by
[34]
was irradiated with 0.5 W of 660 nm red laser pointer at a fluorescence imaging system. The results of fluorescence
room temperature. UV-vis spectra were recorded at 2-min imaging analysis showed that CY5-664 was confirmed
intervals for 20 min. The irreversible bleaching of the dye with significant tumor preferential accumulation by ex vivo
at the absorption peak was monitored as a function of time. imaging of the dissected organs and tissues (Figure 3B).
The highest absorption spectrum of CY5-664 was 646 nm
and 652 nm, and the fluorescence peak was 664 nm and To evaluate the antitumor activity of CY5-664 in vivo,
670 nm in phosphate-buffered solution and dimethyl HCT116 subcutaneous tumor xenograft models were
sulfoxide (DMSO) solution, respectively (Figure 1B). CY5- established, and the tumor-bearing nude mice were
664 has a substantial absorption at 660 nm, which leads randomly divided into three groups: (1) NS + Laser,
to photothermal conversion and fluorescence imaging. (2) CY5-664 treated only, and (3) CY5-664 + Laser.
The absorption intensity decreases with the increase of HCT116 subcutaneous tumor xenograft models were
laser irradiation (660 nm, 0.5 W/cm ) time, but the light established on both shoulders of each mouse in the CY5-
2
absorption was not reduced significantly after 2 min of 664 treatment group. The tumor on one shoulder was
irradiation (Figure 1C). These results showed that CY5- irradiated by laser, while the tumor on the other shoulder
664 remained stable after irradiation for 2 min. was not irradiated by laser. The tumor in NS group mice
was irradiated by laser. According to the results of NIR
3.2. Photoinduced cytotoxicity of CY5-664 fluorescence imaging described above, tumors in laser
Low toxicity under dark conditions and high toxicity under irradiation group were irradiated with 660 nm laser for
2
laser irradiation are the noteworthy characteristics of 2 min (0.8 W/cm ) at 24 h after injection. The results are
phototherapy . To evaluate the photoinduced cytotoxicity shown in Figure 3C-E. Compared with the NS group, tumor
[32]
cancer specificity of CY5-664, cell viability was determined growth was significantly retarded in the CY5-664 + Laser
with or without CY5-664 treatment and 660 nm laser irradiation group. Similar results were further observed by
irradiation on HCT116 and SW480 cells. MTT was used means of tumor imaging and tumor weight analysis in the
as an indicator of cell viability. The results showed that CY5-664 + Laser irradiation group. The antitumor effect
different concentrations of CY5-664 did not significantly of CY5-664 was further evaluated using H&E staining of
inhibit the viability of HCT116 and SW480 cells without tumor tissue sections. As shown in Figure 3F-H, all of the
laser irradiation, and Cy5-664 significantly inhibited the tumor cells in the NS-treated group with laser irradiation
viability of the CRC cells in a dose-dependent manner. and CY5-664-treated group without laser irradiation
However, under laser irradiation, the viability of HCT116 displayed deeper hematoxylin staining, larger nuclei,
and SW480 cells was significantly decreased with the complete morphology, and vigorous division. In contrast,
increased concentration of CY5-664 (0–25 μM) (Figure 2). the tumor cells in the CY5-664 + Laser irradiation group
These results confirmed the photoinduced cytotoxicity of showed lighter hematoxylin staining, damaged nuclear
CY5-664 in a dose-dependent manner. integrity, and shrunk chromatin. These results showed that
CY5-664 significantly inhibits tumor growth with laser
3.3. Imaging, phototherapy, and in vivo toxicity irradiation in vivo.
evaluation To evaluate the toxic side effects of CY5-664 in vivo, the
To demonstrate the tumor-targeting properties and the weight of nude mice was monitored in real time during the
tumor imaging capability of CY5-664 in vivo, BALB/c nude treatment. As displayed in Figure 3I, compared with the

Volume 1 Issue 1 (2022) 5 https://doi.org/10.36922/gpd.v1i1.87