Near-Infrared Organic Dye-Based Nanoagent for the Photothermal

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Near-infrared organic dye-based nanoagent for the photothermal therapy of cancer Bingjiang Zhou, Yunzheng Li, Guangle Niu, Minhuan Lan, Qingyan Jia, and Qionglin Liang ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.6b07838 • Publication Date (Web): 19 Oct 2016 Downloaded from http://pubs.acs.org on October 19, 2016

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ACS Applied Materials & Interfaces

Near-infrared organic dye-based nano-agent for the photothermal therapy of cancer Bingjiang Zhou, † Yunzheng Li, †Guangle Niu, ‡ Minhuan Lan, § Qingyan Jia, ‡ and Qionglin Liang †* †

Key Laboratory of Bioorganic Phosphorus Chemistry and Chemical Biology (Ministry of

Education), Department of Chemistry, Tsinghua University, Beijing 100084, China ‡

Key Laboratory of Photochemical Conversion and Optoelectronic Materials and City U-CAS

Joint Laboratory of Functional Materials and Devices, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences Beijing 100190, China §

Center Of Super-Diamond and Advanced Films and Department of Physics and Materials

Science, City University of Hong Kong, Hong Kong SAR, China KEYWORDS: near-infrared, organic dye, photothermal therapy, nanopartical, cancer

ABSTRACT. Given their easy structural modification and good biocompatibility advantages, near-infrared (NIR) organic dyes with a large molar extinction coefficient while a super-low fluorescence quantum yield show considerable potential application in photothermal therapy (PTT). Herein, a new NIR-absorbing asymmetric cyanine dye, namely, RC, is designed and

1 Environment ACS Paragon Plus


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synthesized via the hybrid of rhodamine and hemicyanine derivatives. RC-BSA nanoparticles (NPs) are fabricated by using the bovine serum albumin (BSA) matrix. The NPs exhibit a strong NIR absorption peak at ~868 nm and 28.7% photothermal conversion efficiency. Based on these features, RC-BSA NPs exhibit excellent performance in ablating tumor under a 915 nm laser radiation through a PTT mechanism. These NPs show no obvious toxicity to the treated mice. Thus, RC-BSA NPs can used as a new NIR laser-triggered PTT agent in cancer treatment.

1 INTRODUCTION As a non-invasive approach for cancer therapy, photothermal therapy (PTT) has developed quckely these years . This approach is based on the fact that PTT agents can convert light energy to heat and thus kill the cancer cell. 1 Various inorganic nanomaterials with NIR-absorbing, for instance, gold nanostructures, sulfide nanoparticles,

12–14

2–6

carbon nanomaterials, 7–9 palladium nanosheets,

and tungsten oxide nanowires

15

10–11

copper

have recently been used by

photothermal agents for PTT. Despite that tumor PTT treatment is highly efficient in animal therapy, most inorganic nanomaterials are non-biodegradable and will be retained inside the body for long period, thereby causing a long-term toxicity risk. Recently, organic polymer materials, such as porphysome, polypyrrole, and a variety of conjugated polymers, have drawn considerable attention in PTT application.6,16 Nonetheless, the biodegradation behaviors of these polymers still need further investigation; some of these materials exhibit shallow tissue penetration 17 because their absorption peaks are not in the NIR region. 18–19 NIR organic dyes are applied in fluorescent labeling and imaging widely.

20–21

High

photothermal conversion efficiency are usually observed in dyes with low fluorescence quantum yield (FL-QY), because of the completive relationship between the fluorescence and


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photothermal conversion in the excited energy inactivation process.

22–23

By combining the

strong NIR extinction coefficient, good biodegradability, and structural modifiability merits, the NIR-absorbing organic dyes show significant potential application in PTT. few NIR dyes, that is, IR825,

23

IR780, 25 and indocyanine green (ICG),

23–26

26

Nevertheless,

are used as PTT

agents. Moreover, 915 nm is an optimal wavelength for PTT compared with the two other commonly used laser wavelengths (808 and 980 nm). Deeper tissue penetration was achieved compared with 808 nm laser and lower water absorbance than 980 nm laser. However, only IR825 exhibits an absorption peak at 915 nm in J-aggregates form. 27 Therefore, developing new NIR dye-based PTT agents with absorption peak at ~915 nm will acquire low water overheat effect and excellent tissue penetration and biodegradation. The large π-conjugation molecular structure will generally cause a bathochromic shift on its fluorescence, and the energy gap law effect will cause high photothermal conversion efficiency. 28 In this paper, we present a novel NIR organic dye-based nano-agent for the photothermal therapy of cancer. The NIR-absorbing asymmetric cyanine dye (RC) was designed and synthesized via a hybrid of hemicyanine and rhodamine derivatives. RC exhibits a broad and strong NIR absorption with a peak at ~868 nm, but an extremely low FL-QY (considerably low to be detected) in methanol. To expand their application in physiological solutions other than methanol solution, bovine serum albumin (BSA) was used to solubilize RC by forming RC-BSA nanoparticles (NPs). Moreover, RC-BSA NPs show excellent biocompatibility in the dark, and can destroy cancer cells under 915 nm laser irradiation by PTT mechanism. The in vivo PTT performance of RC-BSA NPs was further studied by the tumor-bearing mice model. Almost 100% of the tumor was destoyed after the RC-BSA NPs were intratumorally injected into mice



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and radiated by the 915 nm laser for 10 min (1.0 W cm−2). No distinct toxicity was observed on RC-BSA NPs-treated mice. 2 MATERIALS AND METHODS 2.1 Materials All commercial chemicals were used without further purification. The cell bank of Chinese Academy of Sciences (Shanghai, China) provided the 4T1 murine breast cancer cells . Female BALB/c nude mice were obtained from the Vital River Laboratories (Beijing, China). 2.2 Synthesis of RC 29-30 The RC synthesis is illustrated in Scheme 1. Phosphoroxychlorid (18.5 mL) was slowly added into dry dimethylfomamid (DMF; 20 mL) and heating the mixture for 30 min at 50 °C. Cyclohexanone (5.0 g, 51 mM） was added dropwise into the mixture, stirring for 8 h at 60 °C. Subsequently, the mixture poured into ice water (20 mL), and kept overnight to obtain a yellow solid. Afterward, the yellow acicular crystal compound 1 was recrystallized from absolute acetone. Cyclohexanone (2.0 g, 20 mM) was added dropwise to concentrated H2SO4 (10 mL) and cooled the mixture to 0 °C. With vigorous stirring, 2-(4-Diethylamino-2-hydroxybenzoyl) benzoic acid (3.1 g, 10 mM) was also added in portions into the above mixture, then heated (90 °C, 2 h) and placed in ice (300 g) to cool down to 0 °C. Perchloric acid (70%, 4 mL) was added into the above mixture to give a red precipitate, then the mixture was filtered and washed by 100 mL cold water to afford compound 2. Subsequently, ethyl iodide (4.0 g, 25.6 mM) was added into 2,3,3-trimethylbenzoindolenine (4.0 g, 19.1 mM) dry acetonitrile solution and refluxed at 85 °C for 10 h. Compound 3 was separated from the solution as purple solid after cooling down. To synthesize RC, compounds 1 (0.5 g, 3 mM) and 2 (1.4 g, 3 mM) were added to 30 mL of cyclohexane and 1-butanol (7/3, v/v). The mixture was heated (135 °C , 3 h) to


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remove water ,then cooled to room temperature. Compound 3 (1.1 g, 3 mM was dissolved in the above solvent mixture as a slurry (20 mL), was added into the reaction mixture, then heated again (reflux, 10 h). A solid residue was obtained after distilling off solvents in vacuum, washing with 20 mL of ether, and drying in vacuum to gain a black powder. The neutral aluminum oxide column chromatography (elutent: v (CH2Cl2)/v (CH3OH) = 30:1) was used to purified the raw product, yielding RC as an orange powder. 2.3 Preparation of RC-BSA NPs 31-32 BSA (100 mg) was dissolved in 5 mL water, Then 1 equiv amount of RC methanol solution (1.0 mL) was added to the BSA solution dropwise with a microtip probe sonicator (19 W) at room temperature; consequently, RC-BSA NPs were obtained. Glutaraldehyde solution (25%, 5µL) was added to cross-link NPs for 12 h at room temperature. A dialysis bag (MWCO, 14 kDa) was used in dialyzing, against phosphate buffer (pH = 7.4) for two days, the cross-linked RC-BSA NPs solution was obtained. The basically colorless filtrate after dialysis or centrifugal filtration using a 100 kDa filter (6000 rmp for 20 min) (Figure S4) demonstrated a nearly 100% encapsulation efficiency of RC by BSA. Consequently, the concentration of the RC-BSA NPs is 0.25 mM ([RC]=0.25 mM). 2.4 Characterization The RC structure was confirmed by 1H NMR (600 MHz), and

13

C NMR (151 MHz) spectra

(Jeol JNM-ECA 600) and Electrospray ionization high-resolution mass spectra (ESI-HRMS) (Shimadzu LCMS IT/TOF). 1

H NMR (600 MHz, DMSO-d6) δ 8.00 (d, J = 8.8 Hz, 1H, Ar H), 7.90 (d, J = 7.7 Hz, 1H, Ar H),

7.84 – 7.71 (m, 3H, Ar H), 7.64 (t, J = 7.5 Hz, 1H, Ar H), 7.40 (t, J = 7.3 Hz, 1H, Ar H), 7.35 (d, J = 12.0 Hz, 1H, Ar H), 7.31 (d, J = 7.6 Hz, 1H, Ar H), 7.24 (d, J = 8.7 Hz, 1H, Ar H), 7.22 –



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7.14 (m, 2H, –CH=), 6.40 (d, J = 10.7 Hz, 2H, Ar H), 6.34 (d, J = 8.8 Hz, 1H, Ar H), 5.47 (d, J = 12.7 Hz, 1H, –CH=), 3.81 (dd, J = 12.6, 6.2 Hz, 2H, CH2), 3.34 – 3.30 (m, 2H, CH2), 2.54 (dd, J = 39.4, 11.9 Hz, 6H, CH2), 1.84 (s, 6H, CH3), 1.73 (d, J = 4.9 Hz, 2H, CH2), 1.57 (s, 4H, CH2), 1.36 (s, 2H, CH2), 1.14 (t, J = 6.9 Hz, 3H, CH3), 1.06 (t, J = 7.0 Hz, 6H, CH3). 13C NMR (151 MHz, DMSO-d6) δ 169.48, 158.72, 152.20, 149.59, 147.27, 142.12, 135.74, 133.21, 130.38, 130.21, 130.00, 129.74, 129.13, 128.78, 128.17, 127.36, 127.30, 126.45, 125.22, 124.26, 123.90, 122.41, 121.82, 110.13, 109.55, 107.96, 104.87, 97.17, 92.43, 47.66, 44.24, 40.63, 36.80, 32.09, 28.15, 27.19, 26.55, 24.17, 23.31, 22.56, 12.89, 11.70. ESI-HRMS m/z calcd for [C49H50ClN2O3+], 749.3510; found, 749.3510. The size of RC-BSA NPs was characterized by dynamic light scattering (DLS; Horiba SZ-100) at 25 °C. TEM image was obtained from H-7650B (Hitachi, Japan). NIR absorption spectrum was recorded by UV-1100 spectrophotometer (Beijing Eternal Cause Instrument Co., Ltd.). Fluorescence spectra were recorded by a NanoLog infrared fluorescence spectrometer (Nanolog FL3-2iHR, Horiba Jobin Yvon). The absolute FL-QY of RC or RC-BSA NPs was obtinaed with a FLSP920 fluorescence spectrometer (Edinburgh Instruments, Ltd.), which had an integrating sphere (λex = 808 nm, laser). 2.5 Photothermal Performance Evaluation14 Given the photothermal performance measurement of RC-BSA NPs, a 915 nm NIR laser (Changchun New Industries Optoelectronics Tech. Co., Ltd., China) was used as a light source to irradiate the nanoparticles aqueous suspension (1 mL) with different concentrations (0, 0.025, 0.05, and 0.1 mM) in a quartz cuvette. A handy optical power meter (Vega, Ophir, Israel) was used to calibrate the output power to ~1.0 W cm−2. An online thermocouple thermometer


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(YA200R1-4, Shanghai YaDu Electronic Technology Co., Ltd., China) was used to record the temperature changes. The photothermal conversion efficiency of RC-BSA NPs, η, can be calculated by Equation (1): =

ℎ − − 1 1 − 10

where S is the container’s surface area, h represents the heat transfer coefficient, Tmax is the maximum laser-triggered temperature, TSurr is the indoor temperature, QDis is the heat dissipation caused by the the quartz sample cell light absorbing, I is the power of laser (1.0 W cm-2), and A915 is the absorbance of RC-BSA NPs at 915 nm. The value of hS can caculated by Equation 2: 2 ℎ where τs is the time constant of sample system; mD and CD are the mass (1.0 g) and the water =

(solvent) heat capacity (4.2 J/g), respectively. A quartz sample cell containing pure water was used in the independently determination of QDis (46.9 mW). Cellular culture: The 4T1 cells were grown in the RPMI-1640 medium, supplemented with 1% penicillin/streptomycin, and 10% fetal bovine serum and incubated under 5% CO2 at 37 °C. 2.6 Cytotoxicity Test and In vitro PTT The CCK-8 assays was used to measure the cell viability. 4T1 cells were grown in a 96-well plate for 12–24 h before experiments. Afterward, different concentrations of RC-BSA NPs medium solutions replaced the cell medium. For the cytotoxicity test of RC-BSA NPs, cells were incubated with these solutions for 24 h or 48 h in incubator before the cell viability measurement. For the 915 nm laser treatment, after incubated with different concentrations of RC-BSA NPs for 2 h, then cells were exposed to the 915 nm laser (1.0 W cm−2 , 10 min). Subsequently, cells were incubated for another 24 h after replacing the aged medium by fresh medium, and cell viability measurement was performed.



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For live-dead cell staining, 4T1 cells were incubated in media containing RC-BSA NPs (15 µM) for 2 h, then iradiated by the 915 nm laser (1.0 W cm−2, 10 min). Cells were washed by PBS twice after 30 min calcine-AM/PI staining and imaged by an fluorescence microscope (IX81, Olympus Optical Co., Tokyo, Japan). Tumor model for IR Thermal Imaging and PTT: 4T1 cells were implanted into the buttock of female BALB/c nude mice (five-week-old). Solid tumor models in mice were established (~60 mm3) after ~7 days. For the IR thermal imaging, the mice were treated with PBS or RC-BSA NPs solutions and 10 min exposure to the 915 nm laser (1.0 W cm−2). This observation was simultaneously imaged by a Fluke Ti400 IR Camera and quantified by Ti400 examiner software. For the PTT, 20 tumor-bearing mice were randomly distributed into four groups (n=5/group). Mice were intratumorally injected with RC-BSA NPs solution (0.25 mM, 150 µL) and the same volume of PBS with the control mice groups. Laser-treated groups were exposed to the 915 nm NIR laser (1.0 W cm−2, 10 min) only once . Tumor sizes measurement were taken every other day using an electronic digital caliper. The volume was calculated based on the formula: v = a × b

2

/2 (a: length of tumor, b: width of tumor). The relative tumor volumes and weighs were

normalized according to their initial values. 2.7 Tumor Tissue Histological Examination Tumors tissue from PBS- or RC-BSA-NPs injected mice were immediately removed after laser irradiation, fixed in 4% formalin, and embedded in paraffin. Subsequently, the slices were stained by hematoxylin and eosin (H&E). An optical microscope (IX71, Olympus Optical Co., Tokyo, Japan) was used to examine the slices. 3 RESULTS AND DISCUSSION


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3.1 Synthesis and Characterization of RC The RC dye was prepared via two-step condensation reaction. The synthetic routes are illustrated in Scheme 1, and the detailed procedures are presented in the Methods section. The molecular structure of RC was characterized by ESI-HRMS, 1H NMR, and 13C NMR (Figures S1–S3).

Scheme 1. Synthetic route of RC

The photophysical properties of RC in methanol were studied. A strong and wide absorption band in the first NIR region were obeserved the absorption spectra of RC, with a peak at 868 nm and a 950 nm shoulder peak The emission spectra was mainly extended to the sencond NIR region, with a peak at 1023 nm (Figure 1). The molar extinction coefficient of RC was 0.9×105 M−1cm−1 at 868 nm. However, the absolute FL-QY of RC was considerably too low to be detected, with the value lower than that of IR825

23

and ICG 26. Such a low FL-QY originated

from the narrow energy gap of NIR dyes and enhanced the non-radiative transitions by the energy gap law effect. 33 These results indicated that absorbed light energy of RC can be mainly dissipated through nonradiative transition pathways; thus, heat could be produced.



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Figure 1. Normalized absorption (blue line) and emission (red line) spectra of RC in methanol.

3.2 Preparation and Characterization of RC-BSA NPs The synthesized RC was water-insoluble. To expand its application in physiological solutions, The non-antigenic, biocompatible, and clinically utilized BSA protein that is used as the matrix to load with RC to fabricate RC-BSA NPs.

31,34

The detailed procedure was described in the

Methods section (Figure 2a).

Figure 2. (a) Schematic diagram of the fabrication of RC- BSA NPs. (b) Absorption spectra of RC in methanol and RC-BSA NPs in water. (c) TEM image and (d) DLS result of RC-BSA NPs.

As expected, RC-BSA NPs exhibited good water solubility and showed the same absorbance peak (868 nm) as RC in methanol. Nevertheless, a slight decrease was observed in the absorbance at the 905–980 nm region compared with the free CR in methanol. Such a change


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was caused by the different local environment of RC in the BSA matrix compared with that in methanol (Figure 2b). In particular, the molar extinction coefficient of RC-BSA NPs at 915 nm (0.83×105 M−1cm−1) was comparable to that of 868 nm (0.9×105 M−1cm−1) because of the broad absorption peak. Consequently, 915 nm laser can serve as the light source in PTT applications. The absolute FL-QY of RC-BSA NPs in water was 0.01%, which was higher than that of free RC in methanol; this trend was dependent on the more restrict conformation in the BSA matrix than in methanol.

35

TEM and DLS techniques were used to characterized the size and

morphology of RC-BSA NPs . TEM image revealed the spherical shape of RC-BSA NPs with a uniform size of ~110 nm. The average hydrodynamic diameter of the RC-BSA NPs was 135 nm as DLS analysis showed, corresponds to the TEM results (Figure 2c). The zeta potential of the NPs was determined to be -28.4 mV in aqueous. Additionally, the NPs exhibited a great stability in aqueous for the diameter and zeta potential of RC-BSA NPs in 10% fetal bovine serum remained change little with time (Figure S5). 3.3 Photothermal Conversion Property of RC-BSA NPs To demonstrate the photothermal conversion of RC-BSA NPs, the temperature changes of the RC-BSA NPs solution under laser irradiation were investigated. The 915 nm laser was chosen as the PTT light source, acoounting for the strong tissue-penetration ability and the high molar extinction coefficient of RC-BSA NPs at a wavelength of 915 nm, .



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Figure 3. (a) Temperature changes of pure water and different concentrations RC-BSA NPs aqueous suspension under 10 min laser exposure (915 nm, 1.0 W cm−2). (b) Photostability test of RC-BSA NPs aqueous suspension with multiple cycles of laser exposure (RC content: 0.05 mM; 915 nm, 1.0 W cm−2). (c) Photothermal effect of RC-BSA NPs aqueous suspension (RC content: 0.1 mM). After 10 min exposure, the laser was switched off. (d) Time constant for heat transfer of the system (τs).

When exposed to the 915 nm laser (1.0 W cm−2, 10 min), a rapid temperature increase was observed even at rather low concentrations of NPs solution , and the temperature of pure water changed a little (Figure 3a). Notably, those RC-BSA NPs showed excellent photostability (Figure 3b), with a 28.7% photothermal conversion efficiency (Figures 3c and 3d). 3.4 In Vitro PTT Efficacy The cytotoxicity and PTT efficacy in vitro of the RC-BSA NPs was also tested. The standard CCK8 assay was used to determined the relative cell viabilities of 4T1 cells incubated with different RC-BSA NPs concentrations for 24 h or 48 h. Encouragingly, RC-BSA NPs showed no obvious cytotoxicity (Figure 4a). The PTT efficacy of RC-BSA NPs was determined by the viability of cells treated with 10 min laser exposure ( 915 nm, 1.0 W cm−2) after 2 h incubation of different RC-BSA NPs concentrations. As expected, the high nanoparticle concentration


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killed a large number of cells under laser irradiation (Figure 4b). Most of the cells were destroyed after incubation with 15 µM of RC-BSA NPs and 10 min exposure to 915 nm laser (1.0 W cm−2). More cells were killed after prolonging the incubation time to 48 h. The high efficacy of RC-BSA NPs in cancer cell photothermal ablation was further confirmed by the fluorescent images of live-dead cell staining (Figure 4c).

Figure 4. In vitro PTT. (a) Viability of 4T1 cells with various concentrations RC-BSA NPs for 24 h or 48 h. (b) The PTT efficacy of RC-BSA NPs in vitro. (c) Calcein AM/PI live/dead staining of 4T1 cells after PTT by RC-BSA NPs (15 µM). Live cell, green; dead cell, red. Scale bar: 50 µm.

3.5 In vivo PTT Efficacy Based on the photothermal ablation effectivity of RC-BSA NPs in vitro, the in vivo PTT capability of NPs was further studied by the 4T1 tumor-bearing mouse model. Mice were intratumorally injected with RC-BSA NPs (150 µL, 0.25 mM) and subjected to 10 min exposure to 915 nm laser (1.0 W cm−2). A Fluke Ti400 IR camera was taken to monitor the local temperature variation (Figure 5a). After laser exposure, only a mild increase of temperature to ~41 °C on the tumor of PBS-injected mice was detected, while a rapid temperature increase to ~56 °C was observed on the tumor of RC-BSA NP-injected mice(Figure 5b); this change was



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caused by the strong photothermal effect of RC-BSA NPs. Such an increase was sufficient to perform effective tumor ablation at such a temperature. 1

Figure 5. (a) Thermal images of PBS-injected (150 µL) and RC-BSA NPs-injected (0.25 mM, 150 µL) 4T1 tumor-bearing mice after 10 min exposure to 915 nm laser (1.0 W cm−2) (b) Temperature variation of tumors after laser exposure.

To further investigate the therapeutic effect of RC-BSA NPs, 4T1 tumors bearing mice were distribute into four groups: RC-BSA NPs+laser, RC-BSA NPs only, PBS+laser, and PBS only. Mice were intratumorally injected with RC-BSA NPs (150 µL, 0.25 mM) or PBS (150 µL) (Figure 6a). After 10 min of injection, the mice were treated with 10 min exposure to 915 nm laser (1.0 W cm−2) via PTT mechanism. The tumor sizes and mice weights in each group were examined every other day (Figures 6b and 6c). Tumors in the RC-BSA NPs+laser group disappeared within two days after laser exposure, thereby on the original tumor sites only leaving black scars; these scars fell off within 8–10 days post-laser exposure. By contrast, tumor volume increased rapidly over time in the three other groups. The results indicated that RC-BSA NP injection or laser exposure alone could inhibit tumor growth. Furthermore, no tumor regrowth was observed in the RC-BSA NPs+laser group within 20 days after treatment, thereby further confirming that the RC-BSA NPs injection with laser irradiation could completely ablate tumors on mice.


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Figure 6. In vivo PTT. (a) Images of one mouse from each group at different time points after PTT. (b) The relative tumor volume in various mice groups after PTT. (c) Mice weight changes after PTT and (d) Tumor H&E-stained slices of PBS- and RC-BSA-injected mice immediately after laser irradiation. Scale bar: 100 µm.

During the course of therapy, the behaviors of RC-BSA NPs-injected mice after PTT were carefully monitored. The treatment group showed unapparent toxicity sign or distinct physiological weight-decrease within 20 days (Figure 6c). Tumors of PBS- and RC-BSA NPsinjected mice were immediately collected after laser irradiation. Histological examination was performed after H&E staining. As expected, distinct signs of cell damage, such as cell shrinkage, nuclear damage, and loss of contact, were observed in RC-BSA NPs-treated tumors exposed to laser irradiation (Figure 6d). Moreover, the hepatic or kidney disorder of mice was not obvious through the nomal results of serum biochemistry assay and optical images of H&E stained slices



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of major organs after RC-BSA NPs intravenous injection (Figure S6). It is further evidence that RC-BSA NPs has no noticeably long term toxic in vivo to mice. 4 CONCLUSIONS This study designed and synthesized a novel organic dye RC with strong NIR absorption but extremely low FL-QY. BSA was selected as the encapsulation matrix to fabricate RC-BSA NPs and solubilize the lipophilic RC. The molar extinction coefficient of RC-BSA NPs at 915 nm was considerably high, thereby enabling the 915 nm laser used as the light source in PTT treatment. The prepared NPs exhibited fine biocompatibility, good photostability, and 28.7% photothermal conversion efficiency. More importantly, the NPs showed good performance against tumor PTT, thereby resulting in tumor ablation with unapparent toxicity sign to treated mice. These investigations indicated that the RC-BSA NPs could serve as an excellent NIR PTT agent. Moreover, these results provided useful guidelines for the development of NIR dye-based PTT agent. ASSOCIATED CONTENT Supporting Information. The Supporting Information is available free of charge on the ACS Publications website at DOI: Characterization of RC and in vivo toxicology study AUTHOR INFORMATION Corresponding Author [email protected] Notes The authors declare no competing financial interest.


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ACKNOWLEDGMENT This work was supported by the Ministry of Science and Technology (Grant Nos. 2014ZX09304307001 and 2013ZX09507005), the Natural Science Foundation of China (Grant Nos. 21621003, 21235004 and 21175080), and the Program for International S&T Cooperation Projects of China (Grant No. 2011DFA31860 ). REFERENCES 1. Habash, R. W.; Bansal, R.; Krewski, D.; Alhafid, H. T., Thermal Therapy, part 1: An Introduction to Thermal therapy. Crit. Rev. Bioeng. 2006, 34 (6), 459-489. 2. Yang, L. Y.; Tseng, Y. T.; Suo, G. L.; Chen, L. L.; Yu, J. T.; Chiu, W. J.; Huang, C. C.; Lin, C. H., Photothermal Therapeutic Response of Cancer Cells to Aptamer-Gold Nanoparticle-Hybridized Graphene Oxide under NIR Illumination. ACS Appl. Mater. Interfaces 2015, 7 (9), 5097-5106. 3. Schnarr, K.; Mooney, R.; Weng, Y. M.; Zhao, D. H.; Garcia, E.; Armstrong, B.; Annala, A. J.; Kim, S. U.; Aboody, K. S.; Berlin, J. M., Gold Nanoparticle-Loaded Neural Stem Cells for Photothermal Ablation of Cancer. Adv. Healthcare Mater. 2013, 2 (7), 976-982. 4. Liu, H.; Liu, T.; Wu, X.; Li, L.; Tan, L.; Chen, D.; Tang, F., Targeting Gold Nanoshells on Silica Nanorattles: a Drug Cocktail to Fight Breast Tumors via a Single Irradiation with Near-infrared Laser Light. Adv. Mater. 2012, 24 (6), 755-761. 5. Song, J. B.; Yang, X. Y.; Jacobson, O.; Huang, P.; Sun, X. L.; Lin, L. S.; Yan, X. F.; Niu, G.; Ma, Q. J.; Chen, X., Ultrasmall Gold Nanorod Vesicles with Enhanced Tumor Accumulation and Fast Excretion from the Body for Cancer Therapy. Adv. Mater. 2015, 27 (33), 4910-4917. 6. Cheng, L.; Wang, C.; Feng, L. Z.; Yang, K.; Liu, Z., Functional Nanomaterials for Phototherapies of Cancer. Chem. Rev. 2014, 114 (21), 10869-10939. 7. Zhang, B.; Wang, H.; Shen, S.; She, X.; Shi, W.; Chen, J.; Zhang, Q.; Hu, Y.; Pang, Z.; Jiang, X., Fibrin-targeting Peptide CREKA-conjugated Multi-walled Carbon Nanotubes for Self-amplified Photothermal Therapy of Tumor. Biomaterials 2016, 79, 46-55. 8. Wang, H.; Sun, Y.; Yi, J.; Fu, J.; Di, J.; del Carmen Alonso, A.; Zhou, S., Fluorescent Porous Carbon



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Near-Infrared Organic Dye-Based Nanoagent for the Photothermal

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