Single-Stimulus Dual-Drug Sensitive Nanoplatform for Enhanced

May 11, 2016 - Compared with small free drugs and individual photoactivated therapy, Cur@DPNs exhibited enhanced photoactivated cytotoxicity and in vi...
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A single-stimulus dual-drug sensitive nanoplatform for enhanced photo-activated therapy Shasha He, Yanxin Qi, Gaizhen Kuang, Dongfang Zhou, Jizhen Li, Zhigang Xie, Xuesi Chen, Xiabin Jing, and Yubin Huang Biomacromolecules, Just Accepted Manuscript • DOI: 10.1021/acs.biomac.6b00353 • Publication Date (Web): 11 May 2016 Downloaded from http://pubs.acs.org on May 15, 2016

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A single-stimulus dual-drug sensitive nano-platform for enhanced photo-activated therapy Shasha He,a,b Yanxin Qi,a Gaizhen Kuang,c Dongfang Zhou,*a Jizhen Li,d Zhigang Xie,a Xuesi Chen,a Xiabin Jing a and Yubin Huang*a a

State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied

Chemistry, Chinese Academy of Sciences, Changchun, 130022, PR China b

c

University of Chinese Academy of Sciences, Beijing 100049, PR China Department of Gastroenterology, the Second Affiliated Hospital, Medical School of Xi’an

Jiaotong University, Xi’an, 710048, PR China d

College of Chemistry, Jilin University, Changchun, 130023, PR China

KEYWORDS:

photo-activated

therapy,

photodynamic

therapy,

photo-chemotherapy,

nanoparticles, cancer, co-delivery ABSTRACT: Photo-activated therapy has become complementary and attractive modality for traditional cancer treatment. Herein, we demonstrated a novel single-stimulus dual-drug sensitive nano-platform, Cur-loaded Dex–Pt(N3) nanoparticles (Cur@DPNs) for enhanced photo-activated therapy. The developed Cur@DPNs could be photo-activated by UVA light to simultaneously generate instant ROS from Cur for fast photodynamic therapy (PDT) and release lasting Pt(II) from Pt(N3) for long-acting photo-chemotherapy (PCT). Compared with small free drugs and individual photo-activated therapy, Cur@DPNs exhibited enhanced photo-activated cytotoxicity and in vivo antitumor efficacy with low systemic toxicity accompanied. Therefore, the single-

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stimulus dual-drug sensitive nano-platform is convinced to be a promising strategy for multidrug delivery, site-selective and combinational photo-activated therapy in the near future. 1. INTRODUCTION Traditional cancer treatment, including surgery, radiotherapy and chemotherapy has serious side effects causing partial or complete loss of normal organ function. 1 Photo-activated therapy with several advantages such as low systemic toxicity, noninvasiveness, site selectivity, precisely controllable photo-cytotoxicity and easy-regulative light condition has become complementary and attractive modality for traditional cancer treatment.2 Most modern photo-activated therapies involve photodynamic therapy (PDT), (PTT) and so on.

5

3

photo-chemotherapy (PCT),

4

photo-thermal therapy

Due to the complexity of tumor including multi-drug resistance and

heterogeneity, usually a single photo-activated therapy remains suboptimal.6 When applied with light, photosensitizer (PS) for PDT would generate reactive oxygen species (ROS) with a short life-time less than 40 ns for instant cell-killing,2 and photo-activated metal chemotherapeutic drug (PCD) for PCT would release active chemotherapeutic drug for lasting cell-killing.4,7 Therefore, combination of fast PDT and long-acting PCT should be an attractive strategy for more effective cancer treatment. Many compounds including chemicals, drugs, dyes with photo-sensitivity have been advocated for photo-activated therapy.8–10 Curcumin (Cur), a traditional Chinese medicine, is capable of inhibiting a variety of cancers.11 Recently, Cur has also been utilized as an effective PS due to its conjugated double bonds and absorption between 350–500 nm.12,13 However, the poor solubility and instability of Cur have highly confined its clinical usage for PDT.11 To address the problems, Berg et al. have used Pluronics to encapsulate Cur, and the Cur-loaded Pluronics showed intensified photo-activated cytotoxicity than that of under dark.14 For selective

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activation of anticancer drugs within tumors, Sadler et al. have developed a series of photoactivated PtIV–azide complexes (Pt(N3)) as PCD.15–17 Pt(N3) exhibits chemical inertness in the dark while can be activated to active Pt(II) form upon irradiation by UVA or visible light. Taking advantage of the enhanced permeability and retention (EPR) effect of tumors, delivery of Pt(N3) was explored by conjugating them onto the surface of upconversion nanoparticles or the sidechain of block copolymer micelles for PCT.18–24 Xiao et al. reported a biodegradable copolymer carrier grafted with a series of Pt(N3) prodrugs, which showed prolonged blood circulation time and enhanced effective anticancer ability compared with free drugs upon UVA irradiation.20 Recently, several works have been concerned about combination of Cur and Ptbased drugs. For instance, a bi-functional hybrid complex of Cur and Pt(II) named Platicur was reported by Kondaiah et al. which formed stable DNA crosslinking through the released Pt(II) and also served as a PS from Cur.25 Besides the combination in small molecule, Stenzel et al. synthesized a triblock copolymer for physical encapsulation of Cur and a cisplatin prodrug was further used as a core-crosslinking agent.26 The nanoparticles showed noticeable synergistic effect of Cur and cisplatin prodrug. However, to our knowledge, there is no report on co-delivery of Cur (as a PS) and Pt(N3) (as a PCD) in one nano-platform to perform combinational PDT and PCT. We hypothesized that the photo-activated process of Cur and Pt(N3) would be controlled by a single-stimulus (UVA light) simultaneously, and the instant action of Cur and lasting action of Pt(N3) upon cancer cells would be co-reflected for enhanced photo-activated therapy. Herein, we demonstrated a novel single-stimulus dual-drug sensitive nano-platform to codeliver Cur and Pt(N3) for combinational photo-activated therapy. A hydrophobic Pt(N3) was grafted to the sidechains of hydrophilic dextran, and the obtained amphiphilic Dex–Pt(N3) conjugates self-assembled into nanoparticles for further Cur encapsulation. Both Cur and Pt(N3)

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in Cur-loaded Dex–Pt(N3) nanoparticles (Cur@DPNs) could be photo-activated by UVA irradiation. Therefore, Cur@DPNs were expected to have dual modes of action upon cancer cells. Cur would be photo-activated to generate instant ROS within cancer cell for fast PDT and simultaneously active Pt(II) would be photo-reduced and released for long-acting PCT (Scheme 1). The enhanced photo-activated anticancer activity of the single-stimulus dual-drug sensitive nano-platform was evaluated in vitro and in vivo. 2. EXPERIMENTAL SECTION 2.1. Materials Dextran10k,

succinic

anhydride,

N-(3-Dimethylaminopropyl)-N’-ethylcarbodiimide

hydrochloride (EDC·HCl), 4-Dimethylaminopyridine (DMAP) were bought from SigmaAldrich. Cisplatin (purity 99%) was purchased from Shandong Boyuan Chemical Company, China. Curcumin (Cur) was bought from Sinopharm Chemical Reagent Limited Company. Indocyanine green, Hoechst and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) were acquisited from Sigma-Aldrich. Lyso-tracker and cellular reactive oxygen species assay kit (DCF-DA) were bought from Shanghai Biyuntian Biological Co., Ltd. Dimethyl sulphoxide (DMSO) was distilled followed by dried with calcium hydride for 3 days. 2.2. Methods 1

H-NMR spectra were measured at room temperature by a Unity-400 MHz NMR spectrometer

(Bruker). Fourier Transform Infrared (FT-IR) spectra were recorded with a Bruker Vertex 70 spectrometer. Mass Spectroscopy (ESI-MS) measurements were conducted using a Quattro Premier XE system (Waters) equipped with an electrospray interface (ESI). The platinum content was measured by Inductively Coupled Plasma Optical Emission Spectrometer (ICPOES) and Inductively Coupled Plasma Mass Spectrometer (ICP-MS, Thermoscientific, USA).

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Diameters were performed with a Brookhaven 90Plus size analyzer. Transmission electron microscopy (TEM) images were recorded on a JEOL JEM-1011 electron microscope. Confocal laser scanning microscopy (CLSM) images were visualized with a Zeiss 710 confocal laser scanning microscopy image system. Clinic parameters were measured by an automatic biochemical analyzer (Mindray BS-220, China). UV-visible absorption spectra were recorded via a Varian Cary 300 UV-visible spectrophotometer in 1 cm path-length cuvette. UVA irradiation was performed by a xenon lamp source (CEL-S500, AuLight, China) equipped with a UVA filter (340–375 nm) for a parallel light. The power outage was determined by a powermeter (FZ-A, AuLight, China). 2.3. Synthesis and characterization of Dex–Pt(N3) conjugates The synthesis of Pt(N3) and Dex–Pt(N3) conjugates is presented in the supporting information.20–27 Pt(N3) was characterized by 1H-NMR, FT-IR and ESI-MS. Dex–Pt(N3) conjugates were characterized using 1H-NMR and FT-IR. The morphology and size distribution of Dex–Pt(N3) conjugate nanoparticles (DPNs) in distilled water were also monitored through TEM and DLS measurements. 2.4. Preparation and characterization of Cur@DPNs Cur (10 mg) and Dex–Pt(N3) conjugate (100 mg) were dissolved in DMSO (5 mL) and stirred at room temperature for 30 min. The mixture solution was dropwise added into deionized water (60 mL) within 30 min and continuously stirred for another 2 h. Then the mixture solution was dialyzed (MWCO = 3500) against distilled water for 36 h to remove DMSO. Unloaded Cur was filtered with a syringe filter (0.45 µm) and the final clear solution was freeze-dried.28 The lyophilized Cur@DPNs (1 mg) were dissolved in DMF/water (1 mL/1 mL) and the UV-vis absorbance at 425 nm was recorded. The content of Cur in the Cur@DPNs was then calculated

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by using a standard curve. The drug loading content (DLC) and drug loading efficiency (DLE) were further calculated as following equations: DLC (%) = [Cur weight in nanoparticles/total weight of nanoparticles] × 100. DLE (%) = [Cur weight in nanoparticles/initial feeding amount of Cur] × 100. 2.5. Photo-sensitivity of Cur@DPNs Aqueous solutions of Cur, Pt(N3), Dex–Pt(N3) nanoparticles (DPNs) and Cur@DPNs were UVA irradiated (365 nm, 10 mW/cm2) for the indicated periods of time, and the UV–vis spectra of the aqueous solutions were recorded. The changes of morphology and size distribution of DPNs and Cur@DPNs were also monitored through TEM and DLS measurements. For stability in the dark, aqueous solutions of Pt(N3) and Cur@DPNs in distilled water were kept in the dark and UV–vis spectra were also taken at over days. 2.6. Platinum release of Cur@DPNs Lyophilized Cur@DPNs (3 mg) were dissolved in 1 mL of PBS (0.01 M, pH 7.4) or acetate buffer solution (0.01 M, pH 5.0), placed into a pre-swelled dialysis bag (MWCO = 1000) and immersed into the corresponding buffer solution (19 mL). The dialysis was conducted at 37 °C in a shaking culture incubator. Samples were kept in the dark or monitored upon UVA irradiation (365 nm, 10 mW/cm2) in three different ways: (1) fixed time pre-irradiation (30 min initial irradiation before incubation in the dark); (2) continuous irradiation; (3) periodic irradiation (irradiation was turned on for 10 min and then off for 50 min). 1 mL was withdrawn at specified time points from the dialysate and measured for platinum using ICP-OES. After sampling, fresh buffer solution (1 mL) was added to the dialysate. The platinum released from the micelles was expressed as a percentage of cumulative platinum outside the dialysis bag to the total platinum in the micelles as a function of time.

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2.7. Detection of ROS in solution Indocyanine green (ICG) was used as a probe of ROS in vitro.29 ICG solution (1 mL, 25 µg/mL) and Cur@DPNs (1 mL, 5 µg Cur/mL) solution were mixed and irradiated with UVA light (365 nm, 10 mW/cm2) for the indicated periods of time, and the UV–vis spectra of the solution were recorded. 2.8. In vitro assays The human cervical carcinoma HeLa cells and normal fibroblasts L929 cells were obtained from Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, Shanghai, China. The cells were cultured with DMEM (10% fetal bovine serum; 5% CO2 at 37 °C). 2.8.1. Detection of intracellular ROS The intracellular production of ROS was detected using dichlorofluorescein diacetate (DCFDA) (cellular reactive oxygen species assay kit).30 HeLa cells were cultured in a 6-well plate with a density of 5 × 104 cells per well and incubated overnight. The medium was replaced by Cur (3 µg/mL) or Cur@DPNs (3 µg Cur/mL). Cells were incubated for 4 h in the dark and the medium was then replaced by 1 mL of DMEM containing 1 µL of DCFH-DA. After incubated for another 20 min in the dark, the cells were washed twice with PBS. For the samples with irradiation, cells were exposed to UVA light (365 nm, 10 mW/cm2) for 5 min. Finally, the fluorescence images of all the samples were observed immediately with a Zeiss 710 confocal laser scanning microscopy image system. 2.8.2. Cell viability Cytotoxicity was assessed using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. MTT assay was performed in the absence and presence of UVA irradiation. Cells were seeded in 96-well plates at a density of 5 × 103 cells per well and

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incubated in DMEM overnight. The medium was replaced by cisplatin, Pt(N3), Cur, DPNs and Cur@DPNs (Cur 5.4%, Pt 9.6%) at a final Pt concentration from 3.375 to 216 µM or Cur concentration from 0.375 to 24 µg for 4 hours’ incubation. Cells were then washed with PBS twice and incubated with fresh DMEM in the dark for another 24 h, 48 h or 72 h. For the irradiation groups, cells were UVA irradiated (365 nm, 10 mW/cm2) for 15 min before incubated with fresh DMEM in the dark for another 24 h, 48 h or 72 h. MTT solution (20 µL) in PBS (5 mg/mL) was added and the plates were incubated for another 4 h at 37 °C, followed by removal of culture medium containing MTT and addition of DMSO (150 µL) to each well to dissolve the formazan crystals formed. Finally, the plates were shaken for 10 min, and the absorbance of formazan product was measured at 490 nm by a microplate reader. 2.8.3. Combination index analysis Combination index (CI), calculated as the equation described below provides qualitative information on the extent of drug interaction. C

CI =

C A, X B, X + IC IC X, A X, B

CA,x and CB,x are the concentrations of drug A (Cur) and drug B (DPNs) used in combination to achieve x% drug effect. ICx,A and ICx,B are the concentrations for individual agents to achieve the same effect. The CI values lower than, equal to, and higher than 1 denote synergism, additivity, and antagonism, respectively. 2.8.4. Cellular uptake HeLa cells were cultured in a 6-well plate with a density of 5 × 104 cells per well and incubated overnight. The medium was replaced with 1 mL of Lyso-Tracker (50 nM) culture medium for another 30 min.31 Then 1 mL of Cur and Cur@DPNs solution (3 µg Cur/mL) were added. After further 4 h incubation, cells were washed with cold PBS and fixed with 4%

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formaldehyde for 25 min in the dark. For the irradiation groups, cells were UVA irradiated (365 nm, 10 mW/cm2) for 5 min before incubated with fresh DMEM in the dark. Then the cell nucleus was stained with Hoechst for 8 min. The intracellular uptake images were visualized with a Zeiss 710 confocal laser scanning microscopy image system. 2.9. In vivo studies Kunming (KM) mice were purchased from Jilin University (Changchun, China). The murine hepatocarcinoma H22 cells were purchased from Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, Shanghai, China. H22 cells were cultured with the peritoneal system of KM mice. The mice bearing H22 xenografts tumor model used in the experiments were developed by subcutaneously injecting H22 cells (1 × 106, 0.1 mL PBS) into the right legs. All the in vivo study protocols were approved by the local institution review board and performed according to the Guidelines of the Committee on Animal Use and Care of Changchun Institute of Applied Chemistry, Chinese Academy of Sciences. 2.9.1. Tumor inhibition H22 tumor nodules were allowed to grow to a volume about 100 mm3 before initiating treatment. Prior to treatment, all the mice were numbered using ear tags, and their weight and the initial tumor volume were measured and recorded. Saline (n = 16), Cur (2.6 mg/kg) (n = 16), cisplatin (2.6 mg Pt/kg) (n = 16), DPNs (2.6 mg Pt/kg) and Cur@DPNs (2.6 mg Pt/kg, 2.6 mg Cur/kg) (n = 16) were administered intravenously at day 0, day 3 and day 6 in the dark, where n is the number of mice in each group. Mice were then split into two groups: one group was kept constantly in the dark and the other group was irradiated with UVA light (365 nm, 10 mW/cm2) for 30 min at the tumor site on day 1, day 4 and day 7. After the light treatment, mice were returned to the dark. Tumor length and width were measured with calipers, and the tumor

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volume was calculated using the following equation: tumor volume = length × width × width/2. The weight and tumor volume of each mouse were measured every three days over three weeks. 2.9.2. Systemic toxicity KM mice, three per group, were injected intravenously with Cur (2.6 mg Cur/kg), cisplatin (2.6 mg Pt/kg), DPNs (2.6 mg Pt/kg) and Cur@DPNs (2.6 mg Pt/kg, 2.6 mg Cur/kg) on day 0, day 3 and day 6 in the dark. 7 days later, the blood samples were collected and centrifuged (3000 rpm, 5 min) to obtain plasma samples for measuring clinical parameters including aspartate aminotransferase (AST), alanine aminotransferase (ALT), urea nitrogen (UREA), creatinine (CREA) and uric acid (UA) by an automatic biochemical analyzer. 2.9.3. Bio-distribution H22 tumor bearing KM mice, three per group, were injected intravenously with cisplatin (2.6 mg Pt/kg) and Cur@DPNs (2.6 mg Pt/kg) in the dark when the average tumor volume reached 100 mm3. 2 h and 24 h later, major tissues including heart, liver, spleen, lung, kidney and tumor were collected and washed with saline before weighed. Then the tissues were dissolved in nitric acid (65%, v/v) to measure platinum concentrations by ICP-MS and the contents in each tissue were subsequently calculated. 3. RESULTS AND DISCUSSION 3.1. Preparation and characterization of Cur@DPNs Dextran, a kind of hydrophilic polymer with plentiful side hydroxyl groups, has been widely used to prepare nanoparticles for biomedical applications.27,32 In our design, Pt(N3) as a hydrophobic PCD was first synthesized and grafted to dextran through coupling reaction to prepare Dex–Pt(N3) conjugates (Scheme S1 and Figure S1-S3). As shown in Table 1, the grafting ratios of Pt(N3) to dextran could be regulated linearly by the feeding amounts (Figure

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S4), and the obtained amphiphilic conjugates with different Pt contents self-assembled into stable and uniform Dex–Pt(N3) nanoparticles (DPNs) in water with micelles or vesicles morphologies (Figure S5). It is reasonable that variation of hydrophilic-hydrophobic balance made great contribution to the complicated and different self-assembly morphologies.27,33 To address the water insolubility and instability, Cur as a PS was further encapsulated by the above DPNs. As shown in Figure 1A, the coexisted UV-vis absorption peaks at 258 nm belonged to the grafted Pt(N3) and 425 nm ascribed to Cur confirmed the successful encapsulation.20,34 Due to the strong hydrophobic interaction between Cur and Pt(N3), the Cur-loading capacity of DPNs was affected by the grafting content of Pt(N3). DPNs with 14.2 wt% of Pt content had the highest Cur DLE of 54.1% and DLC of 5.4% (Table 1), which was used as the referenced Cur@DPNs sample in following experiments. After encapsulation, the solubility of Cur in water was well improved (Figure 1C), and the diameter of Cur@DPNs (215 nm) was slightly larger than DPNs (197 nm) (Figure 1B, 2B and S5E).34 Adding 10% blood serum did not induce an increase in the apparent size of Cur@DPNs and the PDI of Cur@DPNs was almost the same with time (Figure S6). The normalized UV-vis absorbance of Cur@DPNs at 425 nm in PBS (pH 7.4) in the dark was also recorded to confirm the improved stability of the loaded Cur in the nanoparticles (Figure S7). Free Cur decomposed quickly to only 50% within 90 min, while loaded Cur@DPNs had a significantly increased half lifetime of more than 8 hours. Meantime, the UV-vis absorption peak of Cur@DPNs at 258 nm remained constant during a half month in the dark (Figure S8A). All the results emphasized that Cur@DPNs could co-deliver dual photoactivated drugs (Cur as a PS and Pt(N3) as a PCD) in one nano-platform with improved drug solubility and stability. 3.2. Photo-sensitivity of Cur@DPNs

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When applied with UVA or visible light, Cur displays enhanced anticancer effect due to the generated ROS as a PS, capable of killing cancer cells quickly and efficiently.12 As a PCD, Pt(N3) can also be photo-activated to active Pt(II) under UVA light for lasting DNA crosslinking to induce cancer cell apoptosis.16 Hence, Cur@DPNs were expected to exhibit dual-drug sensitivity through a single-stimulus, UVA light for combinational photo-activated therapy. To study the photo-sensitivity of Cur@DPNs, we recorded the change of their UV-vis spectra under UVA irradiation. Both Cur and DPNs showed rapid response to UVA irradiation, respectively (Figure S8). The characteristic UV-vis peak at 258 nm of DPNs rapidly decreased after light irradiation, denoting the breakdown of Pt-N3 bond and simultaneous photo-reduction of Pt(N3) to active Pt(II). The peak at 425 nm of Cur was also drastically descended at the same irradiation condition. Combining the photo-activated characteristics of Cur and Pt(N3) in one nano-platform, the UV-vis peaks at 258 nm and 425 nm of Cur@DPNs were decreased simultaneously (Figure 2A). From the photolysis curves, it should be noted that the absorbance of Cur dropped much quicker than that of Pt(N3) in Cur@DPNs upon UVA irradiation (Figure 2A and S8). The peak for Cur at 425 nm was almost disappeared after UVA irradiation for 15 min while the peak for Pt(N3) at 258 nm was still remained. All the results demonstrated that Cur@DPNs exhibited single-stimulus dual-drug sensitive property, combining the instant photo-sensitive Cur for fast PDT and lasting photo-sensitive Pt(N3) for long-acting PCT. 13, 35 When hydrophobic Pt(N3) was photo-reduced to hydrophilic Pt(II) and cleaved from dextran backbone partially or completely, the hydrophilic-hydrophobic balance of Cur@DPNs would be shifted and the morphology would be changed (Scheme S1).33 We then monitored the morphology of Cur@DPNs using TEM and DLS under UVA irradiation. As shown in Figure 2, upon continuous UVA irradiation, few vesicles were emerged from the original micelles within

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10 min (Figure 2C), and nearly all the self-assembly structures changed to vesicles after 20 min (Figure 2D). The morphology was further changed to smaller micelles again after UVA treatment for 30 min (Figure 2E) and to irregular structures at last (Figure 2F), agreeing with the DLS results (Figure S10). Similar phenomenon was also observed for DPNs (Figure S9). It is reasonable that the gradual cleavage of Pt(N3) from dextran under irradiation changed the Pt content of DPNs, leading to different morphologies of Cur@DPNs (Table 1). All the results demonstrated that Cur@DPNs would serve as a single-stimulus dual-drug sensitive nanoplatform for photo-activated therapy. 3.3. On-demand Pt release of Cur@DPNs The on-demand Pt release potential and profile from Cur@DPNs were also investigated. The release of Pt from nanoparticles was conducted at pH 5.0 and pH 7.4 with a dialysis method. As shown in Figure 3, upon UVA pre-irradiation, 45-50% of Pt was released within 30 min from Cur@DPNs, and the release rates were much faster than the un-irradiated nanoparticles (Figure 3A, B). What’s more, the Pt release rate was a little quicker at pH 5.0 than that at pH 7.4, possibly due to the easier hydrolysis of the ester linkage between Pt(N3) and dextran.27,

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However, compared with photo-reduction, the contribution of acidolysis was negligible. Upon continuous UVA irradiation, the total Pt release was continuously accelerated and almost reached the maximum value within 90 min (Figure 3C). The “on-off” Pt release profiles were also conducted. As shown in Figure 3D, when irradiation was turned on for 10 min and then off for 50 min, the release rate was accelerated quickly during the 10 min irradiation. For instance, at pH 5.0, only 15% of Pt was released within one hour in the dark while the Pt release was drastically increased to 31% upon irradiation for 10 min, and the release content only increased by 10% in the following 50 min. The “on-off” Pt release was repeatedly observed in response to

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periodic UVA irradiation. These properties could be beneficial for remote control over Pt drug release at tumor site as well as release rates and release modes. 3.4. Intracellular uptake and ROS generation of Cur@DPNs Intracellular uptake of Cur@DPNs was monitored by confocal laser scanning microscopy (CLSM). HeLa cells were respectively incubated with Cur@DPNs and Cur, and lysosomes were labeled with Lyso-Tracker Red to visualize the endocytic pathway. As shown in Figure 4, in the dark, both Cur and Cur@DPNs were successfully ingested (green fluorescence) by cells after 4 h incubation, and nearly all Cur@DPNs were co-located within red fluorescent lysosomes.37, 38 After 4 h incubation and 5 min UVA irradiation, although some yellow dots still remained, it was interesting to found that a certain amount of green fluorescent Cur escaped from red fluorescent lysosomes into the cytoplasm, indicating the successful lysosomal escape and drug unpacking of Cur@DPNs under irradiation. 39 According to references, Cur could react with molecular oxygen to generate ROS under irradiation,

14, 40

and ROS is capable of destroying membrane structure of lysosome to improve

drug/gene escape and unpacking.39, 41 Therefore, indocyanine green (ICG) was used as a probe of ROS in vitro.29 The absorption of ICG is little affected by light irradiation. While Cur@DPNs were irradiated with ICG, the maximum absorption of ICG at 780 nm decreased drastically within 5 min, indicating the ROS-induced decomposition of

ICG (Figure S11).

Dichlorofluorescein diacetate (DCF-DA) (a cell permeable fluorescent dye) was further used as ROS indicator to evaluate the ROS generation of Cur@DPNs after cell internalization upon UVA irradiation.30 Dichlorofluorescein (DCF) with high fluorescent intensity could be formed by rapid oxidization of DCF-DA in the presence of ROS. As shown in Figure 5, after intracellular uptake for 4 h, very weak green fluorescence was observed from the blank cells, Cur

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and Cur@DPNs incubated cells with the co-existence of DCF-DA in the dark, due to the small amount of intrinsic intracellular ROS (Figure 5A, C, E). After exposure to UVA light for 5 min, strong green fluorescence was gained both for Cur and Cur@DPNs incubated cells resulting from the substantial ROS generation (Figure 5H, J). In contrast, the fluorescence almost kept the same for blank cells in the dark and under irradiation (Figure 5A, F). Control cell experiments incubated with Cur and Cur@DPNs without DCF-DA were also conducted (Figure 5B, D, G, I). Under the same excitation parameters as the above ROS detection experiment, no green fluorescence was observed both in the dark and upon irradiation. Simultaneously, the intracellular intake of Cur@DPNs was not affected by UVA irradiation and DCF-DA (Figure S12), implying that Cur itself made no contribution to the green fluorescence and the enhanced fluorescence under irradiation was attributed to the generated ROS. In short, upon UVA irradiation, Cur@DPNs could generate ROS for quick and effective PDT. 3.5. Cytotoxicity Upon a single stimulus (UVA irradiation), both Cur and Pt(N3) in Cur@DPNs were photoactivated to generate ROS for PDT and release active Pt(II) for PCT, respectively. Hence, the cytotoxicity against normal cells and cancer cells of Cur@DPNs under dark and after light irradiation was further assessed by MTT assay using cisplatin, Cur, Pt(N3) and DPNs as control. Without light treatment, cisplatin still killed both HeLa cervical cancer cells and L929 normal fibroblasts without selectivity (Figure 6A, S13 and S15). While, Cur@DPNs exhibited almost no cytotoxicity against normal cells even incubated for 72 h, indicating the safety of Cur@DPNs for site-selective photo-activated therapy. Upon light treatment (10 mW/cm2), cell viability was over 95% after 30 min irradiation in the absence of any drug (Figure S14), and all IC50 values (50% inhibiting concentration) for Cur, Pt(N3), DPNs and Cur@DPNs against HeLa cancer cells

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improved dramatically (Figure 6B, C), since Cur and Pt(N3) were photo-activated to release ROS and active Pt(II), respectively. Cur@DPNs were found to be 17-fold more cytotoxic against HeLa cells upon UVA irradiation than in the dark, suggesting that the cytotoxicity of the dualdrug sensitive platform can be effectively controlled by external light stimulation. Cur@DPNs also showed much higher cytotoxicity than that of equal-dose(Pt) of DPNs and cisplatin and equal-dose(Cur) of Cur, demonstrating the synergism of photo-activated ROS from Cur and active Pt(II) from Pt(N3). We also found that Cur exhibited almost the same photo-activated efficacy after 2 and 4 h incubation, and DPNs showed increased cytotoxicity with incubation time prolonged (Figure S16), confirming the instant cell-killing action of Cur as a PS and lasting action of Pt(N3) as a PCD. To further study the synergy of combinational photo-activated therapy, DPNs and Cur were considered as the individual drug systems and Cur@DPNs as corresponding combination system, and the combination index (CI) determination was carried out. The CI values lower than, equal to, and higher than 1 denote synergism, additivity, and antagonism, respectively.42 As shown in Figure 6D, CI values are plotted against drug effect levels (ICx values, e.g. IC50), and all of the CI vs. ICx plots of Cur@DPNs are under the line of CI = 1, which confirmed the synergy of Cur for PDT and DPNs for PCT in Cur@DPNs. Taken together, all the results revealed that Cur@DPNs could be an ideal single-stimulus dual-drug sensitive nano-platform for enhanced photo-activated therapy with combination of PDT and PCT. 3.6. In vivo antitumor efficacy and systemic toxicity We finally evaluated the photo-activated therapeutic efficacy of Cur@DPNs in vivo against subcutaneous KM mice bearing H22 murine hepatocarcinoma model. Cisplatin, Cur, DPNs and Cur@DPNs were administered intravenously for three times on day 0, day 3 and day 6 under

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dark. Mice were then split into two groups: one group was kept constantly under dark and the other group was irradiated with UVA light at the tumor site for 30 min on day 1, day 4 and day 7. After light treatment, mice were placed back to the dark. Tumor growth inhibition effects in the presence and absence of light treatment are shown in Figure 7. Cisplatin group was almost not affected by light treatment and the tumor was out of control after 12 days. Cur and DPNs were only slightly more effective in inhibiting tumor growth upon light irradiation than under dark. The antitumor effect of Cur@DPNs was greatly enhanced upon light irradiation, implying the greatest efficacy when compared to Cur, DPNs and even cisplatin, in agreement with the cytotoxicity results in vitro. Tumor growth was completely suppressed without excessive growth even over three weeks. The results demonstrated that through the combination of Cur for PDT and Pt(N3) for PCT in one nano-platform, Cur@DPNs exhibited enhanced photo-activated therapeutic efficacy in vivo upon UVA stimulus. Body weight and survival rate were also monitored to evaluate systemic toxicity (Figure 7C, D and S17). Mice in all groups demonstrated continually increased body weight with the exception of cisplatin group both under dark and after light irradiation. Meantime, the survival rate of cisplatin groups was rather lower than the other groups. The decreased values of AST/ALT associated with the function of liver and changed levels of UREA, CREA and UA associated with the function of kidney resulting from cisplatin and Cur treatments indicated the severe hepatotoxicity and renal toxicity induced by free small drugs (Figure 8).43-45 We also found that the concentrations of Pt in normal tissues (heart, liver, spleen, lung) following administration of Cur@DPNs were lower than those treated with free cisplatin, especially the concentration in liver was nearly 1.5-fold lower after 24 h injection (Figure S18). All the data presented herein suggest that cisplatin and Cur exhibited high systemic toxicity, while Cur@DPNs were able to

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enhance anti-tumor efficacy but reduce the side effects and improve the total life quality of mice undergoing photo-activated therapy. 4. Conclusion In conclusion, we have introduced for the first time, a single-stimulus dual-drug sensitive nano-platform for combinational photo-activated therapy. Hydrophobic Pt(N3) was grafted to hydrophilic dextran to prepare Dex–Pt(N3) conjugates for further Cur encapsulation. The developed Cur@DPNs could be photo-activated by UVA light to simultaneously generate instant ROS from Cur for fast photodynamic therapy (PDT) and release lasting Pt(II) from Pt(N3) for long-acting photo-chemotherapy (PCT). Compared with small free drugs and individual photoactivated therapy, Cur@DPNs exhibited enhanced photo-activated cytotoxicity and in vivo antitumor efficacy with low systemic toxicity accompanied. Therefore, the single-stimulus dualdrug sensitive nano-platform is convinced to be a promising strategy for multi-drug delivery, site-selective and combinational photo-activated therapy in the near future.

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Scheme 1 (A) Preparation and single-stimulus (light) dual-drug sensitivity of Cur@DPNs and (B) schematic representation of the intracellular action after endocytosis of Cur@DPNs for combinational photo-activated therapy.

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Table 1 Characteristics of Cur@DPNs n[Pt(N3)] Pt content of Morphology Cur DLE Cur DLC Diameter c /n(Dex)a Dex–Pt(N3) (%)d (%)e (nm) f b (wt%) 10 2.1 micelle 8.9 0.9 194

Zeta potential PDIh (mV)g − 5.1

0.109

20

5.7

micelle

15.7

1.6

175

− 3.2

0.153

30

7.8

micelle

28.9

2.9

182

− 4.2

0.188

40

10.1

vesicle

42.3

4.2

191

− 5.6

0.142

50 14.2 micelle 54.1 5.4 215 − 7.8 0.195 a b Molar ratio of dextran and Pt(N3) in feed; Pt content in Dex–Pt(N3) conjugates estimated by ICP-OES; c Morphology of DPNs with different Pt content; d Cur loading efficiency; e Cur loading content; f Size of Cur@DPNs; g Zeta potential of Cur@DPNs; h Size distribution parameter of Cur@DPNs.

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Figure 1. (A) UV-vis spectra and (B) hydrodynamic diameters of DPNs and Cur@DPNs, (C) photograph of Cur (left) and Cur@DPNs (right) in water (0.1 mg Cur /mL).

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Figure 2. (A) UV-vis spectra of Cur@DPNs upon UVA irradiation (365 nm, 10 mW/cm2) for the indicated intervals of time, and TEM images of Cur@DPNs in response to UVA irradiation for (B) 0 min, (C) 10 min, (D) 20 min, (E) 30 min and (F) 40 min.

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Figure 3. Pt release profiles of Cur@DPNs in pH 5.0 and 7.4 media: (A) in the dark, (B) preirradiation for 30 min, (C) continuous irradiation, (D) periodic irradiation (irradiation was turned on for 10 min and then off for 50 min).

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Figure 4. CLSM images of HeLa cells after (A) Cur and (B) Cur@DPNs treatment for 4 h in the dark, and following UVA irradiation (scale bar: 20 µm).

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Figure 5. CLSM images of HeLa cancer cells incubated with DCF-DA (A, F), Cur (B, G), DCFDA + Cur (C, H), Cur@DPNs (D, I), DCF-DA + Cur@DPNs (E, J) in the absence and presence of UVA irradiation (scale bar: 20 µm).

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Figure 6. (A) In vitro cytotoxicity curves against L929 normal fibroblasts after 72 h incubation in the dark, (B, C) IC50 values of cisplatin (Pt/µM), Pt(N3) (Pt/µM), DPNs (Pt/µM), Cur@DPNs (Pt/µM; Cur/µg) and Cur (Cur/µg) against HeLa cervical cancer cells after 72 h incubation in the absence and presence of UVA irradiation, (D) combination index (CI) curve of Cur@DPNs against HeLa cervical cancer cells after 72 h incubation upon irradiation.

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Figure 7. Tumor growth inhibition curves (A, B) and body weight change (C, D) of mice treated with saline, cisplatin (2.6 mg Pt/kg), Cur (2.6 mg Cur/kg), DPNs (2.6 mg Pt/kg) and Cur@DPNs (2.6 mg Pt/kg, 2.6 mg Cur/kg) in the dark (A, C) and upon UVA irradiation (B, D). Data are expressed as mean ± standard deviation, n = 8, *p < 0.05.

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Figure 8. Alteration of (A) AST/ALT, (B) CREA, (C) UREA and (D) UA levels after 1 week intravenous administration of: a, saline; b, cisplatin; c, Cur; d, DPNs; and e, Cur@DPNs. Values are means ± SD of 3 mice.

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ASSOCIATED CONTENT Supporting Information. Additional experimental protocols, characterization data and in vitro and in vivo results for Cur@DPNs are available at free of charge via the Internet at http://pubs.acs.org . AUTHOR INFORMATION Corresponding Author * Dongfang Zhou: Tel: ++86-431-85262538; E-mail: [email protected] Yubin Huang: Tel & Fax: +86-431-85262769; E-mail: [email protected]. ACKNOWLEDGEMENTS The authors would like to thank the financial support from the National Natural Science Foundation of China (No.51403198 and 51573069), and Jilin Provincial Science and Technology Department (No.20150520019JH). REFERENCES (1) Seeta Rama Raju, G.; Benton, L.; Pavitra, E.; Yu, J. S. Chem. Commun. 2015, 51, 13248– 13259. (2) Ethirajan, M.; Chen, Y.; Joshi, P.; Pandey, R. K. Chem. Soc. Rev. 2011, 40, 340–362. (3) Lucky, S. S.; Soo, K. C.; Zhang, Y. Chem. Rev. 2015, 115, 1990–2042. (4) Crespy, D.; Landfester, K.; Schubert, U. S.; Schiller, A. Chem. Commun. 2010, 46, 6651– 6662. (5) Yu, M.; Guo, F.; Wang, J.; Tan, F.; Li, N. Biomaterials 2016, 79, 25–35. (6) Yin, Q.; Shen, J.; Zhang, Z.; Yu, H.; Li, Y. Adv. Drug Delivery Rev. 2013, 65, 1699–1715. (7) Bonnet, S. Comments Inorg. Chem. 2014, 35, 179–213.

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A single-stimulus dual-drug sensitive nano-platform for enhanced photoactivated therapy Shasha He, Yanxin Qi, Gaizhen Kuang, Dongfang Zhou,* Jizhen Li, Zhigang Xie, Xuesi Chen, Xiabin Jing and Yubin Huang*

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