g-C3N4 Coated Upconversion Nanoparticles for 808 nm Near-Infrared

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g‑C3N4 Coated Upconversion Nanoparticles for 808 nm Near-Infrared Light Triggered Phototherapy and Multiple Imaging Lili Feng,† Fei He,*,† Bin Liu,† Guixin Yang,† Shili Gai,† Piaoping Yang,*,† Chunxia Li,‡ Yunlu Dai,† Ruichan Lv,† and Jun Lin*,‡ †

Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, College of Material Sciences and Chemical Engineering, Harbin Engineering University, Harbin 150001, P. R. China ‡ State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, P. R. China S Supporting Information *

ABSTRACT: Exploring novel photosensitizer (PS) with good stability and high light converting efficiency and designing novel structure to integrate deep penetrating near-infrared (NIR) light excitable up-conversion nanoparticles (UCNPs) and PS into one system are highly fascinating in the photodynamic therapy (PDT) field. In this study, a novel core−shell structured platform (UCNPs@g-C3N4−PEG) with all-in-one “smart” functions for simultaneous photodynamic therapy, photothermal therapy (PTT), and trimodal imaging properties has been rationally designed and fabricated. This system is composed of a core−shell−shell structured NaGdF4:Yb/Tm@NaGdF4:Yb@NaNdF4:Yb up-conversion luminescence (UCL) core and photoactive graphitic-phase carbon nitride (g-C3N4) mesoporous shell closely coated on individual core. This designed structure allows large specific surface area, high loading amount, close proximity to the UCL core, and almost no leakage of g-C3N4 PS, thus ensuring sufficient reactive oxygen species (ROS) to damage tumor cells. Excitation by 808 nm NIR light, the emitted ultraviolet, and visible light can activate g-C3N4 to generate significant amount of ROS and the doped Nd3+ ions give rise to obvious thermal effect, which leads to excellent antitumor efficiency due to the combined PDT and PTT effect. Considering the trimodal imaging properties (UCL, computed tomography, and magnetic resonance imaging), we achieved an imaging guided cancer phototherapy motivated by a single NIR laser.

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thus can effectively activate molecular oxygen to produce more active radicals for PDT.18 Especially, this kind of material is a metal-free semiconductor with thermally/chemically stable, low production cost, good biocompatibility, low cytotoxicity, and extremely high photoluminescence quantum yield.19−25 These unique physical and chemical properties have enabled its diverse applications in energy conversion, catalysis, environmental fields, and biomedicine. However, rare application in PDT field was reported, which allows us to extend this function by producing it as a mesoporous nanostructure with controlled dimensions and surface functionalities. Despite the fact that gC3N4 can be used as potentially therapeutic agent, it can only absorb the short wavelength lights (UV and visible light) that have strong tissue interference, low penetration depth, and possible skin damage, which greatly limits its biomedical applications.26−28 Therefore, design of unique composite and structure that can fully take advantage of NIR light with deeper

hotodynamic therapy (PDT) has drawn public attention due to the unique advantages and negligible systematic toxicity, which has been regarded as a noninvasive nature tool applied in the biomedical domain, especially for anticancer therapy. Choosing a proper photosensitizer (PS) that can generate a vast of reactive oxygen species (ROS) with some kind of light irradiation greatly determines the PDT efficiency.1−7 The commonly used organic photosensitive reagents (ZnPc and Ce6 et al.) are suffering from poor hydrophilicity, facility light bleaching, premature leakage, and other ambiguous security issues, which greatly hinder their biomedical applications.8−12 Thus, recently, some semiconductors and photocatalysts have emerged as new kinds of inorganic PDT reagents, which can be responsive to broad range of wavelength from UV to visible light.13−18 Compared with the reported TiO2 photosensitizer with wide band gap (3.7 eV), which can only respond to UV light,17,18 the N-substituted graphite (g-C3N4) can be responsive to UV and visible (UV− vis) region light owing to its relatively narrow band gap (2.7 eV). In addition, the conduction band (CB) electrons of gC3N4 have a stronger reduction ability than that of TiO2 and © 2016 American Chemical Society

Received: August 26, 2016 Revised: October 7, 2016 Published: October 10, 2016 7935

DOI: 10.1021/acs.chemmater.6b03598 Chem. Mater. 2016, 28, 7935−7946

Article

Chemistry of Materials

Scheme 1. Schematic Illustration of the UCNPs@g-C3N4− PEG Nanocomposite, the Charge Transfer, and the ROS Generation upon 808 nm NIR Light Irradiation

penetration to excite g-C3N4 for generating ROS is highly desirable. Moreover, this kind of therapeutic system should also be combined with diagnostic function for the purpose of clinical application. Recently, the use of up-conversion nanoparticles (UCNPs) has offered us a new way to overcome the shortcomings of gC3N4 excitation wavelength. UCNPs can absorb photons in the near-infrared region (NIR) and convert it to high-energy emission in shorter wavelength region (UV−vis region).29−36 However, for the conventional Yb3+ sensitized UCNPs, the long irradiation time and high power density of the excited 980 nm laser can cause serious tissue overheating owing to the adsorption overlap of Yb3+ ions and water molecules in body, which greatly hinder their clinical application. As an alternative, the 808 nm laser light located at the optical transparency window (700−900 nm) can not only overcome the hyperthermia, but also has deeper tissue penetration due to the minimum absorbance for all biomolecules. Thus, Nd3+ ions sensitized UCNPs can enlighten the research of harsh NIR 808 nm light triggered PDT.37−40 In addition, the energy emitted from UCNPs can be transferred to excite photosensitive drugs for photodynamic or photothermal therapy via the fluorescence resonance energy transfer (FRET) process.41−46 Thereby, integration of UCNPs with photosensitizers may offer an intriguing solution to enable NIR laser utilization. However, the loading mode of PS and the structure of hybrid composite greatly influence the loading amount and the distance between PS and UCNPs, which both play key roles in ROS generation. Exploration of novel NIR-activated g-C3N4 structure with high light converting efficiency still remains a grand challenge. Furthermore, the up-conversion luminescence (UCL) imaging is considered to have deeper biopenetration and better biocompatibility using NIR light excitation.47−53 Also, Gddoped UCNPs with unpaired 4f electrons can be effectively regarded as T1 contrast agent for magnetic resonance imaging (MRI), which performs with a noninvasive fashion to gain functional information and high soft-tissue contrast.54−59 Thus, the therapeutic system in combination with the imaging properties should be highly promising for real time diagnosis and therapy. Recently, we reported two anticancer platforms based on UCNPs and TiO2 composites.60,61 However, the linking/ conjunction mode gives rise to the low specific surface area and limited loading amount of PS (TiO2) on UCNPs,60 which are unfavorable for ROS generation. On the other hand, the photosensitizer TiO2, which can only respond to UV light, cannot make full use of the UV and visible emissions from Yb/ Tm doped UCNPs upon NIR light irradiation, especially the visible (blue) light is much stronger than UV one. In this study, the issue of combining lanthanide ion-doped UCNPs with gC3N4 into one system was first established, where the cancer therapy effect may combine the imaging function to form a phototherapeutic platform and achieve the real time monitoring of performance in the process of cancer treatment. As illustrated in Scheme 1, the UV and visible lights emitted from the NaGdF4:Yb/Tm@NaGdF4:Yb @NaNdF4:Yb upconversion core upon NIR light irradiation excite the electrons in the valence band (VB) transfer to conduction band (CB), which leads to the formation of photogenerated electron−hole pair. These generated electrons react with the electron acceptors (dissolved O2) to produce ROS (•O2−). Meanwhile, as well-known strong oxidants, the photogenerated holes can produce •OH by reacting with H2O. The generated ROS (•O2−

and •OH) are responsible for the cancer killing effect. Moreover, the doped Nd3+ ions in the UCNPs endow the sample with photothermal effect upon NIR light irradiation, which makes it possible to achieve a combined therapy with PDT. The tumor inhibition efficacy and the imaging properties have been well discussed in vitro and in vivo.

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RESULTS AND DISCUSSION Synthesis and Characterization of UCNPs@g-C3N4− PEG Nanocomposite. A novel theranostic nanoplatform was first rationally designed and fabricated by coating a novel photosensitive agent g-C3N4 on Nd3+ sensitized UCNPs. First, to prepare multiple core−shell structured UCNPs, oleic acid capped β-NaGdF4:Yb/Tm core with an mean diameter of 26 nm was prepared through pyrolytic process (Figure 1a). Then two external shell layers of β-NaGdF4:Yb and β-NaNdF4:Yb have been sequentially coated on UCL core by a continuous growth process (Figure 1b,c). A gradual particle size increment (Figure 1a−c) and core−shell−shell structure (inset, Figure 1c) have been achieved. A template etching process was performed to obtain uniform UCNPs@g-C3N4 nanocomposite. The hydrophobic UCNPs dispersed in cyclohexane were first converted to hydrophilic phase utilizing CTAB as blocking agent, which is still used as the surfactant to produce mesoporous silica shell on UCNPs surface by a sol−gel reaction. Then mesoporous silica with thickness of about 30 nm was coated on the as-prepared UCNPs (UCNPs@mSiO2, Figure 1d) after removal of CTAB. After that, the UCNPs@ mSiO2 nanocomposite served as a template to synthesize UCNPs@g-C3N4 mesoporous spheres by etching silica layer. Simply, cyanamide served as nitrogen, and carbon sources were deposited into the mesoporous of silica shell layer, which is easily converted to UCNPs@mSiO2@g-C3N4 nanocomposite (Figure 1e) via the thermal-induced self-condensation of cyanamide at 550 °C. After the mesoporous silica was etched with HF, uniform UCNPs@g-C3N4 mesoporous nanospheres with mean size of 80 nm are finally obtained (Figure 1f). It should be mentioned that the modification of PEG on UCNPs@g-C3N4 is to enhance the biocompatibility. The UCNPs@g-C3N4 nanocomposite before and after modification of PEG exhibits even appearance with excellent dispersity, which is certified by dynamic light scattering (DLS) detection (Figure S1a). The zeta potential of UCNPs@g-C3N4 nanocomposite before and after PEG modification was recorded at pH value of 7.0, as given in Figure S1b. The zeta potential of UCNPs@g-C3N4 is −11.1 ± 0.96 due to the existence of striazine ring modes and aromatic CN heterocycles. After 7936


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Figure 1. TEM images of (a) NaGdF4:Yb/Tm, (b) NaGdF4:Yb/Tm@NaGdF4:Yb, (c) NaGdF4:Yb/Tm@NaGdF4:Yb@NaNdF4:Yb, (d) UCNPs@ mSiO2, (e) UCNPs@mSiO2@g-C3N4, and (f) UCNPs@g-C3N4 (insets in panels c−e are their corresponding magnified TEM images). (g) STEM image and the corresponding EDS mapping images of UCNPs@g-C3N4−PEG and (h) schematic illustration for the synthetic procedure of UCNPs@g-C3N4−PEG.

and acceptor (g-C3N4) are favorable for generating large amount of ROS upon 808 nm NIR light irradiation. Such a structurally optimized nanomaterial demonstrates promising properties for photodynamic therapy. In Figure S3, the XRD patterns of UCNPs were well matched with hexagonal phased NaGdF4 (JCPDS No. 27− 0699), and the wide peaks reveal the nanosized nature. For UCNPs@mSiO2, besides the peaks of β-NaGdF4, the shoulder peak at 22° assigned to amorphous SiO2 indicates the successful coating of silica. For UCNPs@g-C3N4 XRD pattern, the peak at 27.8° conforms to the (002) reflection of a graphitic-phase aromatic structure (g-C3N4), and the diffractions of β-NaGdF4 can also be found, which indicate that two phases exist in the composite. In the Fourier transform infrared (FT-IR) spectrum of UCNPs@g-C3N4 (Figure 2a), the band at 810 cm−1 pertains to the s-triazine ring modes, and the bands at 1200−1600 cm−1 are characteristic of aromatic CN heterocycles. In the X-ray photoelectron spectroscopy (XPS) spectra of UCNPs@g-C3N4 (Figure 2b−d), the peak the binding energy of at 288.3 eV is attributed to the N−C−N coordination. The main N 1s peak at 398.2 eV can be assigned to sp2-hybridized nitrogen in triazine rings (CN−C). The residual two weak feature peaks at approximately 400 and 401.2 eV are attributed to tertiarynitrogen (N−C3) and terminal amino (C−N−H), respectively. All of the above results suggest the successful integration of gC3N4 and UCNPs. The UCL emission spectra of UCNPs show the UV−vis emissions of Tm3+ under 808 nm NIR laser excitation (Figure 3a), that is, 1I6 → 3F4 (348 nm), 1D2 → 3H6 (362 nm), 1D2 → 3 F4 (453 nm), and 1G4 → 3H6 (474 nm). After silica or g-C3N4

passivation with PEG-NH2, the zeta potential of UCNPs@gC3N4−PEG nanocomposite is −7.98 ± 1.36. Test results exhibit that all the samples have a negative charge, which can be the most important sign of as-synthesized nanocomposite with a high water dispersity. This well-dispersed UCNPs@g-C3N4 nanocomposite shows distinct photodynamic effect when irradiated with 808 nm NIR light due to the FRET process from Nd3+ sensitized and Yb3+/Tm3+-doped UCNPs to g-C3N4 mesoporous shell. Together with the photothermal effect generated from the doped Nd3+ in UCNPs, a dual-mode phototherapy is therefore achieved. The scanning transmission electron microscopy (STEM) and the energy-dispersive X-ray spectroscopy (EDS) elemental mapping images show the core−shell structure and uniform dispersion of the elements (Figure 1g). The synthetic process, the PDT and PTT processes upon 808 nm NIR light irradiation, are schematically illustrated in Figure 1, panel h. The porous properties were studied by N2 adsorption/ desorption measurement (Figure S2). As shown, the N2 absorption/desorption isotherms of UCNPs@mSiO 2 , UCNPs@mSiO2@g-C3N4 and UCNPs@g-C3N4 can be classified as type-IV isotherms with H1 hysteresis loops. The Brunauer−Emmett−Teller (BET) surface area of UCNPs@gC3N4 is calculated to be 671 m2 g−1, which is a little smaller than that (881 m2 g−1) of UCNPs@mSiO2 but much higher than that of UCNPs@mSiO2@g-C3N4 (127 m2 g−1). The mesoporous pores (2.6 nm) are mainly distributed in the shell close to the luminescent core, which is in agreement with the TEM observation. The large surface area, mesoporous channel, and good interfacial interaction between donor (UCL core) 7937


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Figure 2. (a) FT-IR spectra of oleic acid capped UCNPs, UCNPs@mSiO2, and UCNPs@g-C3N4. (b) XPS survey spectra of UCNPs@g-C3N4. (c) High-resolution C 1s spectra of UCNPs@g-C3N4, fitted to three energy components centered at around 288.3, 287.0, and 283.8 eV. (d) Highresolution N 1s spectra of UCNPs@g-C3N4, fitted to four energy components centered at around 398.2, 400, 401.2, and 404.4 eV.

Figure 3. (a) UC emission spectra of UCNPs, UCNPs@mSiO2, and UCNPs@g-C3N4 excited by 808 nm NIR light. Inset is the luminescence photograph of UCNPs@g-C3N4 solution under 808 nm NIR light in the dark. (b) UV−vis absorption and normalized PL emission spectra of UCNPs@g-C3N4 in water solution. (c) Decay curves for the 1G4 → 3H6 emissions (475 nm) of Tm3+ in UCNPs@mSiO2 and UCNPs@g-C3N4. Fluorescence spectra of DCFH solutions treated with 10 mg mL−1 (d) UCNPs@mSiO2@g-C3N4 and (e) UCNPs@g-C3N4 under 808 nm NIR light irradiation as a function of the irradiation time. (f) Change of photoluminescence intensity at 525 nm of DCFH-DA-containing solutions of UCNPs@g-C3N4 NPs (triangle) and UCNPs@mSiO2@g-C3N4 (rhombus), given based on three times measurements. Error bars were defined as standard deviations.

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Figure 4. (a) Inverted fluorescence microscope images of HeLa cells incubated with UCNPs@g-C3N4−PEG (500 μg/mL) for different times (0.5, 1, and 3 h) at 37 °C. Each series can be classified to UCL images in dark field (left column), the bright field (middle column), and overlay of both above (right column). (b) The confocal laser scanning microscopy images of HeLa cells incubated with g-C3N4 for 0.5, 1, and 3 h. (c) The viability of L929 cells incubated with UCNPs@g-C3N4−PEG and UCNPs@g-C3N4 with different concentrations for 24 h measured by MTT assay. (d) In vitro HeLa cell viabilities versus particle concentration treated with different conditions. All scale bars are 50 μm. Error bars indicate standard deviations, n = 5.

layer is coated, the UCL emission intensities are decreased due to the FRET process from the donor (UCNPs) to acceptor. Two important factors are necessary to guarantee the FRET process. First, the close proximity to the energy donor (UCNPs) of the acceptor (g-C3N4) has been achieved by the successful coating, which has been verified by the aforementioned TEM, XRD, FT-IR, and XPS results. Second, the UC emissions of UCNPs overlap or partially overlap with the absorption spectrum of g-C3N4 (Figure 3b). As revealed in Figure 3, panel a, the emission intensity in the overlapped range is markedly decreased for UCNPs@g-C3N4, which indicates the efficient FRET process. However, the sample still reveals bright blue emission under 808 nm NIR light excitation (inset, Figure 3a), which makes it applicable for the UCL imaging. To further discuss the FRET effect of UCNPs@g-C3N4 upon irradiation of 808 nm NIR light, we estimated the decay curves of 1G4 → 3H6 (475 nm) transition of Tm3+ in UCNPs@mSiO2 and UCNPs@ g-C3N4 (Figure 3c). It is found that the lifetime of the 1G4 state in UCNPs@g-C3N4 is shorter than that in UCNPs@mSiO2. In UCNPs@g-C3N4, the excited photons on the 1G4 state can be absorbed by g-C3N4 thus resulting in the decreased lifetime, which further suggests an efficient FTER process between UCNPs and g-C3N4.62−64 ROS Generation and Heat Detection of Nanocomposite upon NIR Light Irradiation. It is well-known that ROS can cause damage to mitochondria and DNA in cells, giving rise to the death of tumor cells. Therefore, the crucial factor to determine the PDT efficacy is the capability of yielding ROS. The extracellular ROS were detected by monitoring the fluorescent intensity of dichlorofluorescein (DCF), which is converted from nonfluorescent DCFH-DA oxided by ROS. We

compared the ROS generation abilities of UCNPs@mSiO2@gC3N4 and UCNPs@g-C3N4 irradiated by 808 nm NIR light in the dark. The fluorescent intensity correspondingly represents the amount of the generated ROS. Figure 3, panels d and e show how the fluorescence spectra of DCFH mixed with two samples irradiated with 808 nm NIR light vary with the illumination time. It is apparent that the DCF fluorescent intensities of both UCNPs@mSiO2@g-C3N4 and UCNPs@gC3N4 samples increase with the extended irradiation time. In addition, we calculated the initial reaction rate (Q) of DCFH reacted with ROS in the existence of UCNPs@g-C3N4 or UCNPs@mSiO2@g-C3N4 according to the following equations:65 Q UCNPs@g − C N = RUCNPs@g − C3N4 /PL UCNPs@g − C3N4 3 4

Q UCNPs@mSiO2@g − C N

3 4

= RUCNPs@mSiO2@g − C3N4 /PL UCNPs@mSiO2@g − C3N4

where R is the initial reaction rate of DCFH with ROS in the existence of a photosensitizer (UCNPs@g-C3N4 or UCNPs@ mSiO2@g-C3N4). The R values are supposed to be identical to the initial slope (ΔPL/Δtime). PL is the photoluminescence intensity at 525 nm of the photosensitizer (UCNPs@g-C3N4 or UCNPs@mSiO2@g-C3N4). The value of QUCNPs@mSiO2@g‑C3N4/ QUCNPs@g‑C3N4 is estimated to be 0.82, which implies a higher ROS production efficiency of UCNPs@g-C3N4, as shown in Figure 3, panel f. It is noted that UCNPs@g-C3N4 yields more ROS than UCNPs@mSiO2@g-C3N4 under the same circumstances, which confirms the high generation efficiency of extracellular ROS. The above analysis implies that efficient 7939


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Figure 5. (a) In vivo tumor volume growth curves of U14 tumor-bearing Balb/c mice in different groups after various treatments indicated (5 mice per group). (b) Body weight changes of Balb/c mice versus treated time under different conditions (control, NIR laser, UCNPs@g-C3N4−PEG, UCNPs-PEG with 808 nm NIR laser, and UCNPs@g-C3N4−PEG with 808 nm NIR laser). Error bars indicate standard deviations, n = 5 (∗∗, p < 0.01 as compared with the control group). (c) Photographs of excised tumors from representative Balb/c mice after 14 day treatment and (d) the corresponding digital photographs of mice in the control group and “UCNPs@g-C3N4−PEG with 808 nm laser” group after 14 day treatment. (e) H&E stained tumor sections after 14 day treatment from different groups. All the groups received twice nanocomposite injection and treatment.

Imaging, Uptake, Biocompatibility, and in Vitro Antitumor Properties. As UCNPs@g-C3N4−PEG nanocomposite can efficiently generate ROS when irradiated with 808 nm NIR laser, the tumor suppressor efficiency against HeLa cells was detected in vitro. First, the trimodal imaging properties of UCNPs@g-C3N4−PEG for anticancer diagnosis were investigated. The inverted UCL images of HeLa cells treated with UCNPs@g-C3N4−PEG (500 μg mL−1) at 37 °C for different times (0.5 h, 1 h, 3 h) are presented in Figure 4, panel a. When irradiated upon 808 nm NIR laser, blue UC luminescence of Tm3+ can be clearly seen, and the intensity is increased with prolonged time from 0.5 to 3 h. Moreover, the overlay of UCL images and bright field verifies that the UCL centers were located in the intracellular, which suggests that the as-prepared nanocomposite has been internalized into the cells instead of simply staining the membrane surface. Furthermore, the UCL and overlay of the bright field and UCL images of in vivo UCL imaging of tumor-bearing mice reveal that a significant signal can be found in the tumor sites by intravenous injection at different time periods (Figure S6). All the results manifest that the as-synthesized UCNPs@g-C3N4−PEG is a potential probe to track the carrier, localize the tumor position,

PDT effect can be achieved by coating g-C3N4 mesoporous shell on UCNPs, thus making it possbile for photodynamic therapy. Moreover, electron spin resonance (ESR) spectroscopy of the nanocomposite was also measured to verify the reactive oxygen species to be •OH and O2−. As shown in Figure S4, a characteristic DDMPO−OH spin adduct with four resolved peaks is found, which reveals that ·OH and O2− are generated from UCNPs@g-C3N4 upon NIR light irradiation. Because of heat induced by the Nd3+ ions in the sample, the well cultivated with UCNPs@g-C3N4−PEG nanocomposite shows much higher temperature upon an 808 nm laser irradiation than that cultivated with pure medium (Figure S5a). Encouraged by the photothermal result in vitro, which reveals the effective PTT effect of the platform, we performed the in vivo experiments. Apparent temperature increase is detected on the positions of tumors after injection of UCNPs@ g-C3N4−PEG nanocomposite when exposed to 808 nm laser (Figure S5b). By contrast, no apparent temperature variation for the control group is observed. The in vitro and in vivo results are vividly confirmed by the corresponding temperature curves versus irradiation time (Figure S5c,d). 7940


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Figure 6. Representative histological H&E stained tissue sections from mice to monitor the histological changes in heart, liver, spleen, lung, and kidney were collected from different groups followed by dissections at 14 days postinjection.

responsive fluorescence effect proves that the particles are engulfed by the HeLa cells. In Figure 4, panel c, after incubation with UCNPs@g-C3N4−PEG with various concentrations of 0−1000 μg mL−1 for 12 h, the cellular survival rate descended slightly with the increased concentration, and the cellular viability was still higher than 93.57%, which implied that the sample has low toxicity to normal cells. The cells incubated with UCNPs@g-C3N4 exhibited a realtively low survival rate, which indicated that PEG modification can improve the biocompatibility of the nanocomposite. The cytotoxic effect of UCNPs@g-C3N4−PEG nanocomposite against HeLa cancer cells is assessed in vitro by MTT assay (Figure 4d). When HeLa cells are only irradiated by 808 nm laser, more than 90% cells are viable, which suggests that the NIR light has no obvious impact on cell viability. In addition, the UCNPs@g-C3N4−PEG itself has no apparent toxicity to HeLa cells. However, compared with the UCNPs-PEG only upon 808 nm laser irradiation, the viability of HeLa cancer cells cultured with UCNPs@g-C3N4−PEG in a varied concentration from 7.813 to 1000 μg mL−1 under 808 nm laser irradiation is markedly decreased. It should be noted that the combined PDT and PTT induces over 85% cell death, which is superior to PTT only. In the confocal images of AM (live cells) and PI (dead cells) costained HeLa cells (Figure S10), it is apparent that the tumor cells are almost totally killed when cultured with UCNPs@gC3N4−PEG excitation upon 808 nm NIR laser, yet no apparent cell death is detected for the cells incubated with pure culture. Hemolysis Assay and in Vivo Tumor Inhibition Efficiency. In Figure S11, there is no obvious hemolysis of red blood cells when the UCNPs@g-C3N4−PEG nanocomposite was added with different concentration, which indicates the excellent blood compatibility and low toxicity to the live cells of as-prepared sample. In vivo experiments were further performed to assess the ability of UCNPs@g-C3N4− PEG to inhibit tumor growth upon 808 nm laser irradiation (Figure 5). We used cancer tumor cell line U14 as the

and monitor the therapeutic process real-time. According to the ICP measurement of the Gd in the tumor site at different time points (Figure S7), an effective accumulation of the nanoparticles in the tumor site and slow followed clearance process can be inferred. The effective accumulation of the nanoparticles in the tumor site can be ascribed to the particles size (∼80 nm) and PEG modified surface of the nanomaterials, which are necessary to avoid aggregation of the nanoparticles in the blood vessel and clearance by the immune system. On this condition, the nanoparticles can be delivered to the tumor site effectively with the blood circulation.66 Meanwhile, the brighter signals in in vitro and in vivo T1-weighted images with enhanced Gd concentration demonstrate that the UCNPs@g-C3N4−PEG nanocomposite can act as effective T1 MRI contrast agent on account of the positive signal enhancement property of Gd3+ ions (Figure S8). Besides, the doped Gd/Yb ions endow the product with CT imaging property, which is corroborated by in vitro and in vivo experimental results. In Figure S9, the CT signals increase clearly with the enhanced Gd/Yb concentration, and the CT value is 393.5 HU (Hounsfield units) after injection, which is far higher than that (48.2 HU) without injection. MRI affords excellent spatial resolution, high penetration depth, and has practice in a clinical setting. CT imaging is a clinically diagnostic technique on the basis of the high tissue penetration depth and high-resolution 3D structure details. The UCL possesses large Stokes shift, sharp emission line and superior photostability related with the NIR laser, and provides negligible photodamage to biological specimens and high penetration depth in biological tissues. The achievement of three imaging modalities in one single system can make full use of the superiority of each modality, thereby realizing high quality imaging. In Figure 4, panel b, the blue fluorescence assigned to the material itself (g-C3N4) increases with the increased incubation time. Combined with the above UCL imaging of the cell uptake process of UCNPs@g-C3N4−PEG (Figure 4a), the dual7941


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mediated multimodal imaging guided phototherapy. The gC3N4 mesoporous shell coated on the UCNPs can be irradiated by the UV and visible light from UCNPs through FRET process and generates a large amount of ROS. The PDT coming from this process combined with the PTT effect derived from Nd3+ in UCNPs causes remarkable tumor inhibiting effect in vitro and in vivo under the observation by UCL, MRI, and CT imaging. As a consequence, we convince that this novel multifunctional anticancer therapeutic system could be a promising candidate to achieve NIR laser triggered and imaging-guided cancer therapy.

xenografted model. First, the therapeutic effect of the UCNPs@ g-C3N4−PEG nanocomposite was verified via the procedure of intratumoral injection. As shown in Figure S12, both 808 nm NIR light and UCNPs@g-C3N4−PEG nanocomposite have little effect on the tumor growth, and UCNPs@g-C3N4−PEG with 808 nm NIR irradiation exhibits obvious tumor inhibition effect. To further prove the efficiency of the combined phototherapy based on UCNPs@g-C3N4−PEG nanocomposite, we added control experiment and treated the Balb/c mice by the tail intravenous injection. The Balb/c mice were randomly separated into five groups (5 mice per group). Group 1 injected with saline (100 μL) was taken as normal control. Group 2 was only irradiated by NIR light. The mice in groups 3−5 were intravenously injected with UCNPs@g-C3N4−PEG, UCNPs-PEG, and UCNPs@g-C3N4−PEG, respectively. After injection of 48 h, the tumor sites were excited by 808 nm NIR light for 30 min (2.5 W cm−2, 5 min break after 10 min exicitation, groups 2, 4, and 5), and without NIR irradiation (group 3). In each group, the injected amount was 100 μL (1 mg mL−1), and all groups adopted second nanocomposite injection (4 days after first injection) and treatment. As revealed in Figure 5, panel a, the tumor sizes in the five groups treated with different conditions show different inhibition effects. Similar to the above intratumoral injection results, NIR light and pure UCNPs@g-C3N4−PEG have little influence. Comparison of UCNPs-PEG with NIR light irradiation for PTT only, group 5 (UCNPs@g-C3N4−PEG with NIR light irradiation) exhibits markedly enhanced inhibition efficacy due to the combined PDT and PTT effect, which is achieved by a single NIR light irradiation. The body weight of a mouse is a significant argument to estimate the systemic toxicity of the nanocomposite to tumor-bearing mice. As shown in Figure 5, panel b, the average body weight of each group does not lessen with the prolonged time, which suggests the insignificant side effect of UCNPs@g-C3N4−PEG in comparison with the traditional anticancer therapy drugs. In Figure 5, panel c, the group injected with UCNPs@g-C3N4−PEG and irradiated by 808 nm NIR laser demonstrates the best antitumor inhibition efficacy, which can be vividly verified by the representative photograph of mice with tumors (Figure 5d). The photographs of hematoxylin and eosin (H&E) stained tumor tissues from different groups are proposed in Figure 5, panel e. As given, significantly augmented apoptotic and necrotic tumor cells can be detected in the best inhibition group (group 5), which are attributed to the combined PDT and PTT. In the control group, little damage is found in the tumor issue. We also performed the histological analysis on the main organs including heart, lung, kidney, liver, and spleen in different experimental groups after 14 days of post-treatment, and the results are given in Figure 6. The typical organs treated with UCNPs@g-C3N4−PEG with 808 nm NIR light exhibit no pathological changes (Figure S13), and hepatocytes and the glomerulus structure in the liver, kidney section were observed to be no abnormal phenomenon, whereas pulmonary fibrosis was not examined in the lung samples. Necrosis was not found in any of the histological samples analyzed, which indicates that the UCNPs@g-C3N4−PEG with 808 nm NIR light could be a safe and potential imaging-guided anticancer treatment technique.

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EXPERIMENTAL SECTION

Reagents and Materials. All of the aforementioned chemicals were used without further purification. Gd2O3 (99.99%), Yb2O3 (99.99%), Tm2O3 (99.99%), and Nd2O3 (99.99%) were all purchased from Sinopharm Chemical Reagent. Oleic acid (OA), 2,7-dichlorofluorescein-diacetate (DCFH-DA), 1-octadecene (ODE), and cyanamide were purchased from Sigma-Aldrich. Hydrochloric acid (HCl), cyclohexane, sodium oleate (C18H33NaO2), sodium fluoride (NaF), cetyltrimethylammonium bromide (CTAB, ≥ 99%), tetraethylorthosilicate (TEOS), trifluoroacetic acid (CF3COOH), and sodium trifluoroacetate (CF3COONa), cyananmide were obtained from Beijing Chemical Regent. Synthesis of Oleic Acid Stabilized Core−Shell Structure NaGdF4:Yb/Tm@NaGdF4:Yb @NaNdF4:Yb. The core−shell structure NaGdF4:Yb/Tm@NaGdF4:Yb@NaNdF4:Yb nanoparticles has been synthesized through a previous method with a little modification.67 First, for the fabrication β-NaGdF4:Yb/Tm, 1 mmol of RE(oleate)3 (RE = 79.5% Gd + 20% Yb + 0.5% Tm), 20 mL of oleic acid (OA)/1-octadecene (ODE) (v/v = 1:1), and 12 mmol of NaF component solvent were placed to the three-necked, round-bottomed flask and heated to 110 °C under a vacuum condition for 30 min to remove residual water and oxygen. Afterward, the solution was heated once again, and the temperature kept at 300 °C for 1.5 h under the protection of nitrogen. The β-NaGdF4:Yb/Tm core nanoparticles were achieved through centrifugalization and washed by the ethanol and cyclohexane. For the synthesis of core−shell structure nanoparticles, a template method has been employed. Typically, for the synthesis of NaGdF4:Yb/Tm@NaGdF4:Yb sample, 5 mL of cyclohexane stock solution with NaGdF4:Yb/Tm core sample and 1 mmol CF3COONa, 0.9 mmol Gd(CF3COO)3, and 0.1 mmol Yb(CF3COO)3 were placed into a mixture of OA and ODE in a three-necked roundbottomed flask. The solution was then stirred for 30 min vigorously, and the temperature was improved to 120 °C under the condition of vacuum for a certain time to remove of impurities. After that, the solution was heated to 310 °C and kept for 1 h in N2. After being naturally cooled to room temperature, the NaGdF4:Yb/Tm@ NaGdF4:Yb sample was obtained by centrifugalization and was washed by the ethanol and cyclohexane. The synthetic process of NaGdF4:Yb/ Tm@NaGdF4:Yb@NaNdF4:Yb was analogous to that of NaGdF4:Yb/ Tm@NaNdF4:Yb, except that 1 mmol CF3COONa, 1 mmol RE(CF 3 COO) 3 (RE = 90%Nd + 10%Yb), and as-obtained NaGdF4:Yb/Tm@ NaYF4:Yb nanoparticles were added to a mixture of OA (15 mL) and ODE (15 mL) in a vessel and temperature to 310 °C for 1 h. The final core−shell−shell structured NaGdF4:Yb/Tm@ NaGdF4:Yb@NaNdF4:Yb nanoparticles were denoted as UCNPs, which were dispersed in hexane solution. Synthesis of UCNPs@mSiO2 Spheres. The UCNPs@mSiO2 sample was synthesized by a classical method in a previous work.3 Typically, 2 mL of cyclohexane solution with certain concentration NaGdF4:Yb/Tm@NaGdF4:Yb@NaNdF4:Yb UCNPs (approximately 5−10 mg mL−1) and 0.1 g of CTAB were added into 20 mL of deionized water. The mixture was then stirred vigorously to evaporate cyclohexane at room temperature to the formation of a transparent UCNPs-CTAB solution. Afterward, half of the UCNPs solution was mixed with deionized water (20 mL), ethanol (3 mL), and NaOH solutions (150 μL, 2 mol L−1). The mixed solution was heated up to

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CONCLUSIONS In summary, a novel cancer theranostic system of UCNPs@gC3N4−PEG nanocomposite was first fabricated for the 808 nm 7942


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Chemistry of Materials 70 °C with continuous agitation. Then 150 μL of TEOS was dropped into above solution and kept stirring last 10 min. The product can be obtained by centrifugalization. CTAB was removed via an exchanged approach, where the as-obtained UCNPs@mSiO2 (20 mg) was shifted to 50 mL of ethanol containing 0.25 g of NH4NO3 and refluxed at 60 °C last 2 h. Eventually, the UCNPs (NaGdF4:Yb/Tm@NaGdF4:Yb@ NaNdF4:Yb)@mSiO2 NPs with mesoporous silica shell were achieved and dispersed in ethanol. Synthesis of UCNPs@g-C3N4−PEG Nanocomposite. The UCNPs@mSiO2 nanospheres were used to prepare UCNPs@gC3N4. Typically, 2 g of the UCNPs@mSiO2 nanospheres was added into 10 g of cyanamide (Alfa Aesar) and kept under ultrasonic vibration and vacuum at 60 °C last 2 h. After that, the mixture was put in water bath pot and stirred strictly at 60 °C for 12 h. The product was obtained by centrifugalization and washed by ethanol three times. The obtained powder was dried and treated with hydrofluoric acid for 8 h to elimination the silica template. The as-prepared UCNPs@gC3N4 nanocomposite was obtained and formed an aqueous solution. Afterward, 10 mg of PEG-NH2 was added and continuously stirred for 24 h. UCNPs@g-C3N4−PEG was gained by centrifugation. The yellow UCNPs@g-C3N4−PEG nanocomposite was achieved through vacuum drying. Characterization. Power X-ray diffraction (XRD) patterns were obtained from a Rigaku D/max TTR- III diffractometer with a scanning rate of 10° min−1 in a certain range. Images were acquired with a transmission electron microscope (TEM, FEI Tecnai G2 STwin) and high-resolution transmission electron microscopy (HRTEM). N2 adsorption/desorption isotherms were acquired via a Micromeritrics ASAP Tristar II 3020 instrument. Pore size distribution was estimated by the Barrete−Jonere−Halenda (BJH) approach. The surface-charging characteristics of the product were examined using a zetasizer instrument (NICOMPTM 380 ZLS, PSS·NICOMP). The EPR spectrum was obtained on a JES-FA 200 EPR spectrometer. UCL emission spectrum was performed on Edinburgh FLS 980 equipment utilizing an 808 nm laser as the excitation source. The UC spectra in our experiment were achieved with identical experimental conditions. FT-IR spectra were acquired by an AVATAR 360 FT-IR spectrophotometer. The UV−vis absorbance spectra of the solutions were measured by UV-1601 spectrophotometer. Detection of Reactive Oxygen Species. The generation of extracellular ROS yield was examined by utilizing DCFH-DA as a chemical probe and then measuring the photoluminescence intensity, which could be oxidized by ROS to produce the highly fluorescence DCF. In a typical procedure, DCFH was obtained by mixing methanol solution of DCFH-DA (0.5 mL, 1 mmol L−1) with 2 mL of NaOH (0.01 mol L−1) and then protecting from light and stirring rigorously for 30 min at room temperature. Ten milliliters of sodium phosphate buffer (pH = 7.4) was utilized to make the solution to achieve neutral. Then, 2 mL of the aforementioned solution containing DCFH (25 mmol L−1) was mixed with 2 mL of UCNPs@mSiO2@g-C3N4 and UCNPs@g-C3N4 nanocomposite solutions (10 μg mL−1) and then placed into a 5 mL quartz tube. The reaction solution was irradiated by 808 nm NIR laser for 0, 1, 2, 3, 4, and 5 min in the dark, respectively. Finally, the solution was collected for photoluminescence spectra measurement. In Vitro Cytotoxicity of UCNPs@g-C3N4−PEG. Typically, HeLa cells were planted in 96-well plate (7000 well−1) and then cultured in 5% CO2 at 37 °C overnight to let the cultured cells grew against the wall of flask. Group 1 was only irradiated by 808 nm laser last 30 min. HeLa cells in the following two groups were then incubated with UCNPs@g-C3N4−PEG for approximately 6 h and exposed to 808 nm light last 30 min (group 2) and do not need any illumination (group 3). HeLa cells in group 4 were incubated with UCNPs-PEG with 808 nm light irradiated for 30 min. The laser intensity of all groups accepted NIR irradiation was 2.5 W cm−2, and there was a 5 min break after 10 min of irradiation. Afterward, the cells continued to incubate for another 24 h. Then each well was added with 20 μL of the asprepared MTT (5 mg mL−1) and incubated at 37 °C maintain for another 4 h. At last, each well was added 150 μL of DMSO and shaken for 10 min to mix DMSO with the formazan completely. Microplate

reader was used to measure the absorbance spectra at 490 nm. Further experimental details have been performed to proof the cell viability, Calcein AM and propidium iodide (PI) costained assay were executed to mark dead (red) and live (green) cells, representatively. Cell Viability of UCNPs@g-C3N4−PEG. The in vitro biocompatibility of UCNPs@g-C3N4 and UCNPs@g-C3N4−PEG was detected similar to MTT cytotoxicity assay by incubating L929 fibroblast cells. Briefly, 100 μL of product per well was added, eight wells of them were left with culture medium only serve as normal control, and they cultured overnight to let the cultured cells grow against the wall of flask at 37 °C in 5% CO2. Subsequently, the samples were diluted into respective concentration of 7.8125, 15.625, 31.25, 62.5, 125, 250, 500, and 1000 μg mL−1. Afterward, the cells continued to incubate for another 24 h. Then each well was added 20 μL of the as-prepared MTT solution (5 mg mL−1) and incubated at 37 °C for another 4 h. At last, each well was added 150 μL of DMSO and shaken for 10 min to mix DMSO with the formazan completely. Microplate reader was used to measure the absorbance spectra at 490 nm. Hemolysis Assay of UCNPs@g-C3N4−PEG. To ascertain the in vivo biocompatibility of as-synthesized sample, the detection of hemolysis is necessary. Typically, the acquired red blood cells were washed with 0.9% saline, then centrifugated five times. Afterward, blood cells were mixed with 10 mL of PBS buffer solution. A sample of 0.3 mL of diluted cells suspension was mixed with 1.2 mL of deionized water and PBS considered as a positive and negative control respectively, and 1.2 mL of material suspensions with a series of concentrations (500, 250, 125, 62.5, 31.25, and 15.6 μg mL−1). The eight samples were agitated and kept stable last 1 h at normal temperature. Ultimately, the mixtures were centrifuged, and the upper supernatants were collected to detect the absorbance by UV−vis spectroscopy. The hemolysis percentage was determined by the following formula: Hemolysis % = (A sample − Acontrol(−))/(Acontrol(+) − Acontrol(−)) where A is the value of absorbance via UV−vis spectrum. UCL Microscopy Observation of UCNPs@g-C3N4−PEG. HeLa cells (105 well−1) were cultivated in a culture plates with six-wells, let to grow against the wall of flask, and UCNPs@g-C3N4−PEG (500 μg mL−1) was added to incubate for different times at 37 °C. Posteriorly, the cells were washed with PBS three times and then immobilized with 1 mL of 2.5% formaldehyde at 37 °C maintained for 10 min, and washed three times with PBS. The inverted fluorescence microscopy (Nikon Ti−S) was utilized to assess UCL effect, and meanwhile the samples were exposed to an external 808 nm NIR light. In Vivo Toxicity Studies. Female Balb/c mice (20−25 g) were purchased from Harbin Veterinary Research Institute. Primarily, the tumors were built up by subcutaneous injection of U14 tumor cells into the left axilla of each female Balb/c mice. When the tumors grew to a mean volume of 100 mm3, the tumor-bearing mice were randomly divided into five groups (5 mice per group). All the mice were treated by intratumoral and intravenous injection. For intratumoral injection, the tumor-bearing mice were randomly divided into four groups (5 mice per group) and were treated by intratumoral injection with UCNPs@g-C3N4−PEG, pure 808 nm NIR irradiation, UCNPs@gC3N4−PEG with 808 nm NIR irradiation, and control (without any treatment). The control group did not need any treatment and was utilized for blank control. The dose of injection is 100 μL (1 mg mL−1). For the groups treated with NIR laser, the tumor site was exposed to 808 nm NIR irradiation for 30 min. The tumor size and body weights were measured every other day after treatment. For the intravenous injection group, the first group intravenously injected with saline was taken as normal control. Group two was illuminated with the 808 nm NIR irradiation for 30 min without any injection. The third group was treated by intravenous administration with UCNPs@ g-C3N4−PEG without NIR laser irradiation. Groups four and five were injected with UCNPs-PEG and UCNPs@g-C3N4−PEG, respectively. After 48 h, the tumor sites of the mice in groups 2, 4, and 5 were illuminated with 808 nm light for 30 min (2.5 W cm−2, 5 min break after 10 min irradiation, group 3). The dose of injection is 100 μL (1 7943


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Chemistry of Materials mg mL−1). The tumor site was denuded, and 0.1 mL of chloral hydrate solution was utilized to anesthetize the mice before irradiation. All the groups adopted second nanocomposite injection (4 days after first injection) and treatment. The average tumor volumes and body weights were estimated every 2 days after post-treatment, up to 14 days. The diameters of tumors were measured by a Vernier caliper in two dimensions every other day and estimated as volume V = (width2 × length)/2. The average body weight of mice per group was also calculated. Relative tumor volume was estimated as V/V0 (V0 was the initiated tumor volume before treatment). Histology Examination. Histology analysis was carried out after 14 days of treatment, immediately. The representative photographs of different tissues (heart, liver, spleen, lung, and kidney) of the mice in different treatment groups were presented. Then the mouse organs were dehydrated using buffered formalin, different concentrations of ethanol solution, and xylene. Afterward, the dehydrated organs were trapped in liquid paraffin. The organs and tumor tissues (3−5 mm) were sliced and stained with H&E and then observed on Leica TCS SP8. Measurement of Accumulation Effect in Tumor. The mice were divided into eight groups (three mice per group) and injected with UCNPs@g-C3N4−PEG sample intravenously. The tumors were collected at various times (0.5, 1, 3, 6, 12, 18, 24, and 48 h) after intravenous injection. Post-treatment was performed for further characterization. ICP-MS was utilized to examine the gadolinium concentration in the solution. In Vitro and in Vivo X-ray CT Imaging. The in vitro CT imaging was acquired on a Philips 64-slice CT scanner (120 kV). For in vitro CT imaging, the UCNPs@g-C 3 N4 −PEG nanocomposite was dissolved in saline and diluted to different concentrations of 0, 1, 2, 4, 8, and 16 mg mL−1 and then put in 2 mL tubes. First, 10% chloral hydrate anesthetized was injected in the intraperitoneal of tumorbearing mice to execute in vivo CT imaging. After that, 100 μL of UCNPs@g-C3N4−PEG (500 μg mL−1) was intratumorally injected into the tumor-bearing mice in situ for in vivo CT imaging. In Vitro and In Vivo T1-Weighted MR Imaging. The in vitro MR imaging was operated on a 0.5 T MRI magnet. A sample of 100 μL of UCNPs@g-C3N4−PEG nanocomposite (500 μg mL−1) was dissolved in water with various Gd concentrations. T1 measurements were measured using a nonlinear fit to changes in the mean signal intensity within each well versus repetition time (RT) with a Huantong 1.5 T MR scanner. At last, the values of r1 relaxivity were evaluated via the fitted curve of 1/T1 relaxation time (s−1) on the basis of Gd concentration. In Vivo Photothermal Imaging of UCNPs@g-C3N4−PEG. U14 tumor cells were incubated into the left armpit of the female mice subcutaneously. When the average tumors sizes were reached about 100 mm3, 100 μL of UCNPs@g-C3N4−PEG (500 μg mL−1) was injected into the U14 tumor-bearing mice. After injection 48 h, R300SR-HD infrared camera was utilized to record the thermal images effect as irradiation time goes on when the tumors were illuminated by 808 nm NIR laser. In Vivo Upconversion Fluorescence Imaging. In vivo upconversion fluorescence imaging was operated through an in vivo imaging equipment with 808 nm NIR light as the excitation source. UCL signals were rectified by Andor DU897 EMCCD and for further estimated.

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*E-mail: [email protected]. *E-mail: [email protected]. Author Contributions

The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS Financial support from the Natural Science Foundation of China (NSFC 21271053, 21401032, 51472058, 51332008, 51502050, 51422209, and 51572258), Outstanding Youth Foundation of Heilongjiang Province (JC2015003), and the Fundamental Research funds for the Central Universities is greatly acknowledged.

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(1) Li, C. X.; Hou, Z. Y.; Dai, Y. L.; Yang, D. M.; Cheng, Z. Y.; Ma, P. A.; Lin, J. A Facile Fabrication of Upconversion Luminescent and Mesoporous Core-Shell Structured Beta-NaYF4:Yb3+,Er3+@mSiO2 Nanocomposite Spheres for Anti-cancer Drug Delivery and Cell Imaging. Biomater. Sci. 2013, 1, 213−223. (2) Chen, G. Y.; Ohulchanskyy, T. Y.; Kachynski, A.; Agren, H.; Prasad, P. N. Intense Visible and Near-Infrared Upconversion Photoluminescence in Colloidal LiYF4:Er3+ Nanocrystals under Excitation at 1490 nm. ACS Nano 2011, 5, 4981−4986. (3) He, F.; Yang, G. X.; Yang, P. P.; Yu, Y. X.; Lv, R. C.; Li, C. X.; Dai, Y. L.; Gai, S. L.; Lin, J. A New Single 808 nm NIR Light-Induced Imaging-Guided Multifunctional Cancer Therapy Platform. Adv. Funct. Mater. 2015, 25, 3966−3976. (4) Zhou, J.; Liu, Z.; Li, F. Y. Upconversion Nanophosphors for Small-animal Imaging. Chem. Soc. Rev. 2012, 41, 1323−1349. (5) Idris, N. M.; Gnanasammandhan, M. K.; Zhang, J.; Ho, P. C.; Mahendran, R.; Zhang, Y. In Vivo Photodynamic Therapy Using Upconversion Nanoparticles as Remote-Controlled Nanotransducers. Nat. Med. 2012, 18, 1580−U190. (6) Min, Y. Z.; Li, J. M.; Liu, F.; Yeow, E. K. L.; Xing, B. G. NearInfrared Light-Mediated Photoactivation of a Platinum Antitumor Prodrug and Simultaneous Cellular Apoptosis Imaging by Upconversion-Luminescent Nanoparticles. Angew. Chem., Int. Ed. 2014, 53, 1012−1016. (7) Pan, L. Y.; He, M.; Ma, J. B.; Tang, W.; Gao, G.; He, R.; Su, H. C.; Cui, D. X. Phase and Size Controllable Synthesis of NaYbF4 Nanocrystals in Oleic Acid/Ionic Liquid Two-Phase System for Targeted Fluorescent Imaging of Gastric Cancer. Theranostics 2013, 3, 210−222. (8) Chien, Y. H.; Chou, Y. L.; Wang, S. W.; Hung, S. T.; Liau, M. C.; Chao, Y. J.; Su, C. H.; Yeh, C. S. Near-Infrared Light Photocontrolled Targeting, Bioimaging, and Chemotherapy with Caged Upconversion Nanoparticles in Vitro and in Vivo. ACS Nano 2013, 7, 8516−8528. (9) Gu, Z. J.; Yan, L.; Tian, G.; Li, S. J.; Chai, Z. F.; Zhao, Y. L. Recent Advances in Design and Fabrication of Upconversion Nanoparticles and Their Safe Theranostic Applications. Adv. Mater. 2013, 25, 3758−3779. (10) Wang, Y. H.; Wang, H. G.; Liu, D. P.; Song, S. Y.; Wang, X.; Zhang, H. J. Graphene Oxide Covalently Grafted Upconversion Nanoparticles for Combined NIR Mediated Imaging and Photothermal/Photodynamic Cancer Therapy. Biomaterials 2013, 34, 7715− 7724. (11) Li, X. M.; Zhang, F.; Zhao, D. Y. Highly efficient lanthanide upconverting nanomaterials: Progresses and challenges. Nano Today 2013, 8, 643−676. (12) Su, Q. Q.; Han, S. Y.; Xie, X. J.; Zhu, H. M.; Chen, H. Y.; Chen, C. K.; Liu, R. S.; Chen, X. Y.; Wang, F.; Liu, X. G. The Effect of Surface Coating on Energy Migration-Mediated Upconversion. J. Am. Chem. Soc. 2012, 134, 20849−20857.

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.chemmater.6b03598. Supporting figures (PDF)

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REFERENCES

AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected].

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Article


(32) Zhang, C. S.; Zhao, J. Z.; Wu, S.; Wang, Z. L.; Wu, W. H.; Ma, J.; Guo, S.; Huang, L. Intramolecular RET Enhanced Visible LightAbsorbing Bodipy Organic Triplet Photosensitizers and Application in Photooxidation and Triplet-Triplet Annihilation Upconversion. J. Am. Chem. Soc. 2013, 135, 10566−10578. (33) Heer, S.; Kompe, K.; Gudel, H. U.; Haase, M. Highly Efficient Multicolour Upconversion Emission in Transparent Colloids of Lanthanide-Doped NaTF4 Nanocrystals. Adv. Mater. 2004, 16, 2102−2105. (34) Haase, M.; Schafer, H. Upconverting Nanoparticles. Angew. Chem., Int. Ed. 2011, 50, 5808−5829. (35) Wang, G. F.; Peng, Q.; Li, Y. D. Lanthanide-Doped Nanocrystals: Synthesis, Optical-Magnetic Properties, and Applications. Acc. Chem. Res. 2011, 44, 322−332. (36) Boyer, J. C.; Cuccia, L. A.; Capobianco, J. A. Synthesis of Colloidal Upconverting NaYF4: Er3+/Yb3+ and Tm3+/Yb3+ Monodisperse Nanocrystals. Nano Lett. 2007, 7, 847−852. (37) Zhong, Y. T.; Tian, G.; Gu, Z. J.; Yang, Y. J.; Gu, L.; Zhao, Y. L.; Ma, Y.; Yao, J. N. Elimination of Photon Quenching by a Transition Layer to Fabricate a Quenching-Shield Sandwich Structure for 800 nm Excited Upconversion Luminescence of Nd3+ Sensitized Nanoparticles. Adv. Mater. 2014, 26, 2831−2837. (38) Liu, C. H.; Chen, D. P. Controlled synthesis of Hexagon Shaped Lanthanide-Doped LaF3 Nanoplates with Multicolor Upconversion Fluorescence. J. Mater. Chem. 2007, 17, 3875−3880. (39) Xie, X. J.; Gao, N. Y.; Deng, R. R.; Sun, Q.; Xu, Q. H.; Liu, X. G. Mechanistic Investigation of Photon Upconversion in Nd3+-Sensitized Core-Shell Nanoparticles. J. Am. Chem. Soc. 2013, 135, 12608−12611. (40) Jacinto, C.; Oliveira, S. L.; Catundab, T.; Andrade, A. A.; Myers, J. D.; Myers, M. J. Upconversion Effect on Fluorescence Quantum Efficiency and Heat Generation in Nd3+-Doped Materials. Opt. Express 2005, 13, 2040−2046. (41) Xia, L.; Kong, X. G.; Liu, X. M.; Tu, L. P.; Zhang, Y. L.; Chang, Y. L.; Liu, K.; Shen, D. Z.; Zhao, H. Y.; Zhang, H. An Upconversion Nanoparticle - Zinc Phthalocyanine Based Nanophotosensitizer for Photodynamic Therapy. Biomaterials 2014, 35, 4146−4156. (42) Liu, X. M.; Zheng, M.; Kong, X. G.; Zhang, Y. L.; Zeng, Q. H.; Sun, Z. C.; Buma, W. J.; Zhang, H. Separately Doped Upconversion-C60 Nanoplatform for NIR Imaging-Guided Photodynamic Therapy of Cancer Cells. Chem. Commun. 2013, 49, 3224−3226. (43) He, L.; Feng, L. Z.; Cheng, L.; Liu, Y. M.; Li, Z. W.; Peng, R.; Li, Y. G.; Guo, L.; Liu, Z. Multilayer Dual-Polymer-Coated Upconversion Nanoparticles for Multimodal Imaging and Serum-Enhanced Gene Delivery. ACS Appl. Mater. Interfaces 2013, 5, 10381−10388. (44) Cheng, L.; Yang, K.; Li, Y. G.; Chen, J. H.; Wang, C.; Shao, M. W.; Lee, S. T.; Liu, Z. Facile Preparation of Multifunctional Upconversion Nanoprobes for Multimodal Imaging and DualTargeted Photothermal Therapy. Angew. Chem., Int. Ed. 2011, 50, 7385−7390. (45) Yi, G. S.; Chow, G. M. Water-soluble NaYF4:Yb,Er(Tm)/ NaYF4/Polymer Core/Shell/Shell Nanoparticles with Significant Enhancement of Upconversion Fluorescence. Chem. Mater. 2007, 19, 341−343. (46) Lim, S. F.; Riehn, R.; Ryu, W. S.; Khanarian, N.; Tung, C. K.; Tank, D.; Austin, R. H. In Vivo and Scanning Electron Microscopy Imaging of Upconverting Nanophosphors in Caenorhabditis Elegans. Nano Lett. 2006, 6, 169−174. (47) Liu, Y. S.; Tu, D. T.; Zhu, H. M.; Li, R. F.; Luo, W. Q.; Chen, X. Y. A Strategy to Achieve Efficient Dual-Mode Luminescence of Eu3+ in Lanthanides Doped Multifunctional NaGdF4 Nanocrystals. Adv. Mater. 2010, 22, 3266−3271. (48) Huang, P.; Zheng, W.; Zhou, S. Y.; Tu, D. T.; Chen, Z.; Zhu, H. M.; Li, R. F.; Ma, E.; Huang, M. D.; Chen, X. Y. Lanthanide-Doped LiLuF4 Upconversion Nanoprobes for the Detection of Disease Biomarkers. Angew. Chem., Int. Ed. 2014, 53, 1252−1257. (49) Zhao, J. Z.; Wu, W. H.; Sun, J. F.; Guo, S. Triplet Photosensitizers: from Molecular Design to Applications. Chem. Soc. Rev. 2013, 42, 5323−5351.

(13) Chatterjee, D. K.; Yong, Z. Upconverting Nanoparticles as Nanotransducers for Photodynamic Therapy in Cancer Cells. Nanomedicine 2008, 3, 73−82. (14) Feng, W.; Zhu, X. J.; Li, F. Y. Recent Advances in the Optimization and Functionalization of Upconversion Nanomaterials for in Vivo Bioapplications. NPG Asia Mater. 2013, 5, e75. (15) Wang, C.; Cheng, L.; Liu, Z. Upconversion Nanoparticles for Photodynamic Therapy and Other Cancer Therapeutics. Theranostics 2013, 3, 317−330. (16) Qiao, X. F.; Zhou, J. C.; Xiao, J. W.; Wang, Y. F.; Sun, L. D.; Yan, C. H. Triple-functional Core-Shell Structured Upconversion Luminescent Nanoparticles Covalently Grafted with Photosensitizer for Luminescent, Magnetic Resonance Imaging and Photodynamic Therapy. Nanoscale 2012, 4, 4611−4623. (17) Yang, Y. M.; Liu, F.; Liu, X. G.; Xing, B. G. NIR Light Controlled Photorelease of Sirna and its Targeted Intracellular Delivery Based on Upconversion Nanoparticles. Nanoscale 2013, 5, 231−238. (18) Zhou, L.; Li, Z. H.; Liu, Z.; Yin, M. L.; Ren, J. S.; Qu, X. G. OneStep Nucleotide-Programmed Growth of Porous Upconversion Nanoparticles: Application to Cell Labeling and Drug Delivery. Nanoscale 2014, 6, 1445−1452. (19) Zheng, Y.; Liu, J.; Liang, J.; Jaroniec, M.; Qiao, S. Z. Graphitic Carbon Nitride Materials: Controllable Synthesis and Applications in Fuel Cells and Photocatalysis. Energy Environ. Sci. 2012, 5, 6717−6731. (20) Thomas, A.; Fischer, A.; Goettmann, F.; Antonietti, M.; Muller, J. O.; Schlogl, R.; Carlsson, J. M. Graphitic Carbon Nitride Materials: Variation of Structure and Morphology and Their Use as Metal-Free Catalysts. J. Mater. Chem. 2008, 18, 4893−4908. (21) Xiang, Q. J.; Yu, J. G.; Jaroniec, M. Preparation and Enhanced Visible-Light Photocatalytic H-2-Production Activity of Graphene/ C3N4 Composites. J. Phys. Chem. C 2011, 115, 7355−7363. (22) Liu, G.; Niu, P.; Sun, C. H.; Smith, S. C.; Chen, Z. G.; Lu, G. Q.; Cheng, H. M. Unique Electronic Structure Induced High Photoreactivity of Sulfur-Doped Graphitic C3N4. J. Am. Chem. Soc. 2010, 132, 11642−11648. (23) Jiang, S.; Win, K. Y.; Liu, S. H.; Teng, C. P.; Zheng, Y. G.; Han, M. Y. Surface-functionalized Nanoparticles for Biosensing and Imaging-Guided Therapeutics. Nanoscale 2013, 5, 3127−3148. (24) Wang, L. Y.; Yan, R. X.; Huo, Z. Y.; Wang, L.; Zeng, J. H.; Bao, J.; Wang, X.; Peng, Q.; Li, Y. D. Fluorescence Resonant Energy Transfer Biosensor Based on Upconversion-Luminescent Nanoparticles. Angew. Chem., Int. Ed. 2005, 44, 6054−6057. (25) Kramer, K. W.; Biner, D.; Frei, G.; Gudel, H. U.; Hehlen, M. P.; Luthi, S. R. Hexagonal Sodium Yttrium Fluoride Based Green and Blue Emitting Upconversion Phosphors. Chem. Mater. 2004, 16, 1244−1251. (26) Wang, Y.; Wang, X. C.; Antonietti, M. Polymeric Graphitic Carbon Nitride as a Heterogeneous Organocatalyst: From Photochemistry to Multipurpose Catalysis to Sustainable Chemistry. Angew. Chem., Int. Ed. 2012, 51, 68−89. (27) Ge, L.; Han, C. C.; Liu, J. Novel Visible Light-Induced G-C3N4/ Bi2WO6 Composite Photocatalysts for Efficient Degradation of Methyl Orange. Appl. Catal., B 2011, 108-109, 100−107. (28) Chen, X. F.; Zhang, J. S.; Fu, X. Z.; Antonietti, M.; Wang, X. C. Fe-g-C3N4-Catalyzed Oxidation of Benzene to Phenol Using Hydrogen Peroxide and Visible Light. J. Am. Chem. Soc. 2009, 131, 11658− 11659. (29) Wang, F.; Deng, R. R.; Wang, J.; Wang, Q. X.; Han, Y.; Zhu, H. M.; Chen, X. Y.; Liu, X. G. Tuning Upconversion through Energy Migration in Core-Shell Nanoparticles. Nat. Mater. 2011, 10, 968− 973. (30) Xiao, Q. B.; Ji, Y. T.; Xiao, Z. H.; Zhang, Y.; Lin, H. Z.; Wang, Q. B. Novel Multifunctional Nayf4:Er3+,Yb3+/PEGDA Hybrid Microspheres: NIR-Light-Activated Photopolymerization and Drug Delivery. Chem. Commun. 2013, 49, 1527−1529. (31) Zhao, J. W.; Li, H. T.; Zeng, Q. H.; Song, K.; Wang, X. F.; Kong, X. G. Temperature-dependent Upconversion Luminescence of NaYF4:Yb3+,Er3+ Nanoparticles. Chem. Lett. 2013, 42, 310−312. 7945


Article

Chemistry of Materials (50) Chen, F.; Bu, W. B.; Zhang, L. X.; Fan, Y. C.; Shi, J. L. Is black iron oxide nanoparticle always a light absorber. J. Mater. Chem. 2011, 21, 7990−7995. (51) Li, C. X.; Lin, J. Rare Earth Fluoride Nano-/Microcrystals: Synthesis, Surface Modification and Application. J. Mater. Chem. 2010, 20, 6831−6847. (52) Jayakumar, M. K. G.; Idris, N. M.; Zhang, Y. Remote Activation of Biomolecules in Deep Tissues Using Near-Infrared-To-UV Upconversion Nanotransducers. Proc. Natl. Acad. Sci. U. S. A. 2012, 109, 8483−8488. (53) Ye, X. C.; Collins, J. E.; Kang, Y. J.; Chen, J.; Chen, D. T. N.; Yodh, A. G.; Murray, C. B. Morphologically Controlled Synthesis of Colloidal Upconversion Nanophosphors and Their Shape-Directed Self-Assembly. Proc. Natl. Acad. Sci. U. S. A. 2010, 107, 22430−22435. (54) Liu, Q.; Sun, Y.; Li, C. G.; Zhou, J.; Li, C. Y.; Yang, T. S.; Zhang, X. Z.; Yi, T.; Wu, D. M.; Li, F. Y. F-18-Labeled MagneticUpconversion Nanophosphors via Rare-Earth Cation-Assisted Ligand Assembly. ACS Nano 2011, 5, 3146−3157. (55) Yang, D. M.; Dai, Y. L.; Liu, J. H.; Zhou, Y.; Chen, Y. Y.; Li, C. X.; Ma, P. A.; Lin, J. Ultra-Small BaGdF5-Based Upconversion Nanoparticles as Drug Carriers and Multimodal Imaging Probes. Biomaterials 2014, 35, 2011−2023. (56) Niu, X. J.; Chen, H. Y.; Wang, Y. Q.; Wang, W. H.; Sun, X. Y.; Chen, L. X. Upconversion Fluorescence-SERS Dual-Mode Tags for Cellular and in Vivo Imaging. ACS Appl. Mater. Interfaces 2014, 6, 5152−5160. (57) Park, Y.; Kim, H. M.; Kim, J. H.; Moon, K. C.; Yoo, B.; Lee, K. T.; Lee, N.; Choi, Y.; Park, W.; Ling, D.; Na, K.; Moon, W. K.; Choi, S. H.; Park, H. S.; Yoon, S. Y.; Suh, Y. D.; Lee, S. H.; Hyeon, T. Theranostic Probe Based on Lanthanide-Doped Nanoparticles for Simultaneous In Vivo Dual-Modal Imaging and Photodynamic Therapy. Adv. Mater. 2012, 24, 5755−5761. (58) Shibu, E. S.; Hamada, M.; Murase, N.; Biju, V. Nanomaterials Formulations for Photothermal and Photodynamic Therapy of Cancer. J. Photochem. Photobiol., C 2013, 15, 53−72. (59) Xiao, Q. F.; Zheng, X. P.; Bu, W. B.; Ge, W. Q.; Zhang, S. J.; Chen, F.; Xing, H. Y.; Ren, Q. G.; Fan, W. P.; Zhao, K. L.; Hua, Y. Q.; Shi, J. L. A Core/Satellite Multifunctional Nanotheranostic for in Vivo Imaging and Tumor Eradication by Radiation/Photothermal Synergistic Therapy. J. Am. Chem. Soc. 2013, 135, 13041−13048. (60) Hou, Z.; Zhang, Y.; Deng, K.; Chen, Y.; Li, X.; Deng, X.; Cheng, Z.; Lian, H.; Li, C.; Lin, J. UV-Emitting Upconversion-Based TiO2 Photosensitizing Nanoplatform: Near-Infrared Light Mediated in Vivo Photodynamic Therapy via Mitochondria-Involved Apoptosis Pathway. ACS Nano 2015, 9, 2584−2599. (61) Yang, G.; Yang, D.; Yang, P.; Lv, R.; Li, C.; Zhong, C.; He, F.; Gai, S.; Lin, J. A Single 808 nm Near-Infrared Light-Mediated Multiple Imaging and Photodynamic Therapy Based on Titania Coupled Upconversion Nanoparticles. Chem. Mater. 2015, 27, 7957−7968. (62) Shan, J. N.; Uddi, M.; Yao, N.; Ju, Y. G. Anomalous Raman Scattering of Colloidal Yb3+,Er3+ Codoped NaYF4 Nanophosphors and Dynamic Probing of the Upconversion Luminescence. Adv. Funct. Mater. 2010, 20, 3530−3537. (63) Lee, K. Y.; Seow, E.; Zhang, Y.; Lim, Y. C. Targeting CCL21folic Acid-Upconversion Nanoparticles Conjugates to Folate ReceptorAlpha Expressing Tumor Cells in An Endothelial-Tumor Cell Bilayer Model. Biomaterials 2013, 34, 4860−4871. (64) Wang, C.; Tao, H. Q.; Cheng, L.; Liu, Z. Near-Infrared Light Induced in Vivo Photodynamic Therapy of Cancer Based on Upconversion Nanoparticles. Biomaterials 2011, 32, 6145−6154. (65) Kawasaki, H.; Kumar, S.; Li, G.; Zeng, C.; Kauffman, D. R.; Yoshimoto, J.; Iwasaki, Y.; Jin, R. Generation of Singlet Oxygen by Photoexcited Au25(SR)18 Clusters. Chem. Mater. 2014, 26, 2777− 2788. (66) Sykes, E.; Chen, J.; Zheng, G.; Chan, W. Investigating the Impact of Nanoparticle Size on Active and Passive Tumor Targeting Efficiency. ACS Nano 2014, 8, 5696−5706. (67) Yang, G.; Lv, R.; He, F.; Qu, F.; Gai, S.; Du, S.; Wei, Z.; Yang, P. A core/shell/satellite anticancer platform for 808 NIR light-driven

multimodal imaging and combined chemo-/photothermal therapy. Nanoscale 2015, 7, 13747−13758.

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