Conjugated Polymers-Based Thermal-Responsive Nanoparticles for

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Conjugated Polymers-Based Thermal-Responsive Nanoparticles for Controlled Drug Delivery, Tracking and Synergistic Photodynamic Therapy/Chemotherapy Zhuanning Lu, Ziqi Zhang, and Yanli Tang ACS Appl. Bio Mater., Just Accepted Manuscript • DOI: 10.1021/acsabm.9b00640 • Publication Date (Web): 28 Aug 2019 Downloaded from pubs.acs.org on August 29, 2019

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ACS Applied Bio Materials

Conjugated Polymers-Based Thermal-Responsive Nanoparticles Tracking

for and

Controlled Synergistic

Drug

Delivery,

Photodynamic

Therapy/Chemotherapy Zhuanning Lu, Ziqi Zhang and Yanli Tang* Key Laboratory of Analytical Chemistry for Life Science of Shaanxi Province, Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi’an 710119, P. R. China.

KEYWORDS. Conjugated polymer nanoparticles, thermal-responsive drug release, tracking, PDT, synergistic therapy.

ABSTRACT. Stimuli-responsive multifunctional nanomaterials have attracted much attention due to drug release on-demand for cancer therapy. In this study, the thermal-responsive nanoparticles are prepared based on cationic conjugated poly(fluorene-co-vinylene) (PFV), temperature-responsive poly(N-isopropylacrylamide) (PNIPAM) and anti-tumor model drug

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doxorubicin (DOX). Interestingly, the nanoparticles possess multiple functions including thermo-responsive drug release, cell imaging and chemo- and photodynamic synergistic therapy. The drug is released efficiently above the lower critical solution temperature (LCST) of PNIPAM and more than 70% of the loaded drugs were delivered at pH 5.5 and 37 °C. Importantly, the drug release process can be tracked by fluorescent imaging owing to the bright fluorescence of conjugated polymer-based nanoparticles. Specifically, conjugated polymer PFV act as a photosensitizer to produce high reactive oxygen species under white light irradiation, bringing effective chemo-/ photodynamic therapy (PDT) synergistic effect. The cell viability of MCF-7 decreases to only 3.2% after treating with PNIPAM-DOX-CPNs under white irradiation, which is much lower than that with single treatment. Therefore, the multifunctional nanoparticles provide a promising platform for controllable drug delivery, tracking and tumor therapy in biomedical applications.

INTRODUCTION Cancer is one of the most serious diseases that threaten human health. Chemotherapy as the most important tool for the treatment of tumor, has been severely hampered by its side effects, including cytotoxicity to the normal cells and tissues, low bioavailability, multidrug resistance (MDR) and poor tumor selectivity.1-3 It is still urgent to develop new therapeutic methods to increase the efficiency of cancer treatment. Recently, photodynamic therapy (PDT) has been widely utilized as a non-invasive cancer therapeutic technology. PDT is dependent on reactive oxygen species (ROS) that are produced by photosensitizers under illumination, then the


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generated ROS can make cell damage or death through disrupting membrane structure or inhibiting enzyme activity.4-7 Especially, nano drug delivery systems (NDDS) combining PDT and chemotherapy have attracted much attention for tumor therapy in virtue of highly enhanced

permeability

and

retention

(EPR)

effect,

tumor

accumulation,

great

biocompatibility, induced antitumor immunity and enhanced therapeutic efficiency.8-13 To improve drug delivery, the stimuli-responsive materials are much more preferred since drugs could be controllably released on demand.14-20 Specifically, the tracking of drug release under stimuli is important to investigate the drug delivery strategy and cell apoptosis mechanism. Among the temperature-responsive materials, poly(N-isopropylacrylamide) (PNIPAM) is a kind of macromolecular compound that is widely studied, which attributes to its sharp coil-to-globule phase transition property of polymer chains in aqueous solution at a lower critical solution temperature (LCST).21 Due to the advantage, PNIPAM has been employed in many biomedical fields including drug delivery, gene therapy, surface modifiers, and so on. 14, 15, 22-24 However, it is difficult to monitor the drug delivery when PNIPAM was used alone. Conjugated polymer nanoparticles (CPNs), as one of promising nanomaterials, have received increasing recognition for their applications in biosensors and bioanalysis, such as biological sensing, drug delivery and cell imaging, in virtue of their modifiable properties, excellent photostability, high fluorescence brightness, and good biocompatibility.25-33 Moreover, conjugated polymers demonstrated the ability to produce ROS under light irradiation, and were applied as a promising PDT agent.34-36 Thus, CPNs-based drug delivery system can act not


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only as drug carrier but also as image and PDT agents, which greatly simplifies the synthesis of nano-drug carriers and provides a platform for drug release monitoring. Herein, we constructed a conjugated polymers-based nanoparticles for temperature-stimuli drug release, tracking and chemo- and PDT synergistic therapy. The nanoparticles were prepared by a self-assembly of cationic conjugated poly(fluorene-co-vinylene) (PFV), temperature-responsive polymer PNIPAM and anticancer model drug DOX. In the nano reprecipitation process, conjugated polymer PFV and DOX form the core by hydrophobic and π-π interactions, and a shell of the nanoparticles is formed by PNIPAM on the surface (Scheme 1). The nanoparticles demonstrate strong fluorescence, which provides the platform for cell imaging. When incubated with cells, nanoparticles can be accumulated in cancer cells by the effect of EPR. The nanoparticles are quite stable when the temperature is lower than the LCST of PNIPAM. However, a phase transition will occur from hydrophilic swelling to hydrophobic condense upon the temperature being above the LCST. Thus the interparticle space is greatly reduced by the agglomeration process and DOX is squeezed out at a higher rate. Meanwhile, the nanoparticles can generate plenty of ROS for PDT therapy under the irradiation of white light. Thus, the nanoparticles can be used for controllable drug release, the monitoring of drug release and synergistic therapy.


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Scheme 1. Schematic illustration of formation of thermal-responsive nanoparticle (PNIPAM-DOX-CPNs), drug release and chemo-/PDT synergistic therapeutic mechanism. EXPERIMENTAL SECTION Synthesis of conjugated polymers. Monomer 1 and monomer 2 were synthesized according to the literature.37, 38 Under nitrogen, monomer 1 (0.1 mmol, 66.2 mg), monomer 2 (0.02 mmol, 10.0 mg), 1,4-Dibromobenzene (0.08 mmol, 18.7 mg), and triethylamine (0.5 mL) were dissolved completely in degassed DMF (1.0 mL). Then Pd (OAc)2 (0.005 mmol, 1.15 mg) and P(o-tolyl)3 (0.0228 mmol, 7.0 mg) were added to the solution. The reaction mixture was


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vigorously stirred for 12 h at 100 °C. The cooled solution was dialyzed using a membrane with molecular cutoff of 3500 for 3 days, and then the solution was lyophilized to afford an orange compound (70 mg). Then the compound was added into CH3OH (20 mL) to form a homogeneous solution, and trimethylamine ethanol solution (2 mL) was added. The mixture was stirred at room temperature for 48 h. Finally, the solid was collected and dried under reduced vacuum. (80 mg, 74%). 1H NMR (400 MHz, DMSO-d6) δ: 7.84 - 7.27 (m), 4.14 - 3.83 (m), 3.26 - 3.18 (m), 2.97 (s), 2.11 (m), 1.74 (b), 1. 47 (b), 1. 06 (m), 0.6 (b). GPC: Mn = 16600,

Mw = 18816, PDI = 1.13. Preparation of nanoparticles. The conjugated polymer nanoparticles were prepared by a reprecipitation method. Firstly, in dimethyl sulfoxide, doxorubicin hydrochloride (DOX·HCl) was reacted with triethylamine overnight to make the DOX. In a typical process, for the preparation of PNIPAM- DOX-CPNs, 100 μL of PFV (1.0 mg/mL in CH3OH), 25 μL of PNIPAM (1.0 mg/mL in CH3OH) and 50 μL of DOX (1.0 mg/mL in CH3OH) were mixed in 5 mL CH3OH to give a homogeneous mixed solution. Then the mixed solution was rapidly poured into water (20 mL) under ultrasonic and ice bath. The solvents were then removed by ultrafiltration and washed three times by water. The final volume was adjusted to 5 mL for further experiments. Similar protocol was adopted to prepare other nanoparticles with different mass concertation ratios (PFV/PNIPAM). In vitro drug release. In a release medium (phosphate buffered saline, PBS), release of DOX from the nanoparticles was assayed by using dialysis membrane tubing (molecular weight cutoff of 3,500 Da) in different pH conditions at different temperatures (25 or 37 °C). Each


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nanoparticles solution (3 mL, containing 30 µg of DOX) was sealed in a dialysis bag and was dialyzed in 20 mL PBS. At a certain time interval, 2 mL medium was drawn out, followed by addition of 2 mL of fresh buffer solution. Then the drawn medium was tested to determine the amount of released DOX by a Hitachi F-7000 spectrophotometer with the emission wavelength at 560 nm. The release behavior of other samples with different mass concertation ratios (PFV/PNIPAM) were measured using the same method mentioned above. The measurement was repeated for three times.

RESULT AND DISCUSSION

Synthesis and characterization of PNIPAM-DOX-CPNs. The synthesis route for PFV is shown in Figure 1A. Monomer 1 and monomer 2 were synthesized according to the literature.37, 38 The polymer was synthesized by a Heck coupling reaction between monomer 1, monomer 2, and 1,4-diiodobenzene (molar ratio is 1.0, 0.2, and 0.8, respectively), and its weight-average molecular weight Mw is 18816 with a polydispersity index (PDI) of 1.13. 39 The absorption and emission spectra of the PFV were measured in aqueous solution. As shown in Figure 1B, the maximal absorption wavelength of PFV is at 437 nm and the maximal emission wavelength is at 502 nm. The strong fluorescence provides the platform for cell imaging.


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Figure 1. (A) The synthetic route of compounds (1, 2, and 3), monomer 1, monomer 2 and cationic conjugated polymer PFV. Absorption and emission spectra of (B) conjugated polymer PFV, (C) PNIPAM-CPNs, and (D) PNIPAM-DOX-CPNs in aqueous solution. The concentration of PFV is 10 μM for absorption and 1 μM for emission, respectively.

To obtain thermal-responsive drug loaded nanoparticles, we introduced the temperatureresponsive poly(N-isopropylacrylamide) (PNIPAM). PNIPAM will play an important role in


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increasing the stability of nanoparticles and also will provide effective stimulus condition for the nano drug delivery system. The nanoparticles PNIPAM-DOX-CPNs thus were prepared by a nano-precipitation method based on conjugated polymers, the model drug DOX and PNIPAM. As a comparison, the PNIPAM-CPNs nanoparticles without DOX were also prepared. Figure 1C shows that the maximal absorption and emission wavelength for PNIPAM-CPNs are 438 nm and 506 nm, respectively. Additionally, the maximal absorption and emission wavelengths of PNIPAM-DOX-CPNs are at 437 and 504 nm (Figure 1D), respectively, which are very similar with PNIPAM-CPNs and PFV in aqueous solution. Interestingly, PNIPAM-DOX-CPNs have another absorption peak at 510 ~ 550 nm, which corresponds to the absorption of DOX. This result turns out that DOX has been successfully encapsulated into nanoparticles. It is observed that the fluorescence intensity of PNIPAMDOX-CPNs decreases comparing to PNIPAM-CPNs and PFV, which may result from the quenching of DOX by the π-π stacking interactions between PFV backbone and DOX. Besides, the absolute fluorescence quantum yields (ΦF) of PFV, PNIPAM-CPNs and PNIPAM-DOXCPNs in aqueous solution were measured as 8.9 %, 8.8 % and 4.9 % respectively, which are consistent with the results obtained by the fluorometry. The hydrodynamic diameter of the nanoparticles was investigated by DLS. As shown in Figure 2A and 2B, the diameter of PNIPAM-CPNs is 73.7 nm, whereas that of PNIPAM-DOXCPNs is 86.2 nm, which is about 13 nm larger than PNIPAM-CPNs because of the successful load of the DOX. Then the morphology of the PNIPAM-DOX-CPNs was investigated by scanning electron microscopy. As shown in Figure 2C, PNIPAM-DOX-CPNs display a uniform


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and spherical morphology. Furthermore, the size and fluorescence intensity of PNIPAMDOX-CPNs can remain unchanged during the experimental period, demonstrating the excellent colloidal stability and photostability (Figure 2D and 2E).

Figure 2. Size distribution of (A) PNIPAM-CPNs and (B) PNIPAM-DOX-CPNs. (C) SEM image of PNIPAM-DOX-CPNs. The scale bar is 2.0 μm. (D) Particle size and (E) fluorescence intensity of PNIPAM-DOX-CPNs at different storing time.

ROS and 1O2 generation ability. Firstly, ROS production under white light irradiation was investigated by a ROS-sensitive probe 2′,7′-dichlorodihydrofluorescein diacetate (DCFH-DA). 35, 36

DCFH-DA has very weak fluorescence, but it could be rapidly oxidized by ROS into highly

fluorescent 2,7-dichlorofluor-escein (DCF). An apparent emission of DCF at 525 nm was detected (excitation: 488 nm). Thus, the fluorescence intensity of DCF can be used to monitor


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the ROS production rate. As shown in Figure 3A, PFV, PNIPAM-CPNs and PNIPAM-DOXCPNs have an extremely similar and high ROS production rate under white light irradiation. Compared to the control DCFH, the rates show a 7.5-fold enhancement in the fluorescence intensity of DCF which was measured at 525 nm with the excitation wavelength of 488 nm. Among the cytotoxic reactive oxygen species, 1O2 plays a more important role in destructing cells and tumor blood vessels. Thus, we further measured the yield of singlet oxygen using singlet oxygen sensor reagent SOSG. Similar to DCFH-DA, the non-luminous SOSG will emit strong fluorescence at 525 nm after interaction with 1O2, thus the recovered fluorescence of SOSG can be used to measure the 1O2 generation. As shown in Figure 3B, the generation of O2 by PNIPAM-DOX-CPNs is higher than those by PNIPAM-CPNs and PFV. The

1

fluorescence intensity of SOSG induced by PNIPAM-DOX-CPNs, PNIPAM-CPNs and PFV has the 7.3-fold, 5.2-fold and 4.3-fold enhancement, respectively, compared to the control. It is reported that the ROS are generated via Type 1 and Type 2 photochemical mechanisms. 40 Combined with the results of ROS measurements, it is possible that the ROS produced by PNIPAM-DOX-CPNs is mainly derived from 1O2 via Type 1 mechanism, whereas PNIPAMCPNs and PFV may generate both 1O2 by Type 1 and other ROS by Type 2. The detailed mechanism is still unclear. These results further confirm that PNIPAM-DOX-CPNs are an efficient PDT agent for treatment of tumor.


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Figure 3. (A) Fluorescence intensity of DCF at 525nm in PBS (25 mM; pH 7.4) in the presence of PNIPAM-DOX-CPNs, PNIPAM-CPNs or PFV under white light irradiation (0−5 min) with an excitation wavelength of 488 nm. [DCFH] = 40 μM and [PFV] = 0.5 μM. (B) Fluorescence intensity of SOSG at 525 nm in Tri-HCl (100 mM; pH 7.5) in the presence of PNIPAM-DOXCPNs, PNIPAM-CPNs or PFV under white light irradiation (0-5 min). [SOSG] = 1.0 μM, and [PFV] = 1.0 μM. The error bars represent the standard deviations of three parallel measurements. Drug loading and in vitro drug release. In order to evaluate the effect of the PNIPAM content on release of DOX, we prepared series of PNIPAM-DOX-CPNs with different mass concentration ratios of the PFV / PNIPAM, including 2:1, 4:1, 6:1 and 1:0 (PFV/PNIPAM). Figure 4A demonstrates that under the same conditions (37 oC, pH 7.4), drug release by


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nanoparticles with the rate of 4:1 is prior to the NPs with other ratios. Thus we chose the NPs with 4:1 (PFV/PNIPAM) for the subsequent experiments. Figure 4. (A) In vitro DOX release of PNIPAM-DOX-CPNs under different mass concentration ratios of the PFV and PNIPAM in PBS (10 mM, pH 7.4) at 37 oC. (B) DOX release of PNIPAMDOX-CPNs with 4:1 ratio at different pH and temperatures in PBS (10 mM). (C) SEM image of PNIPAM-DOX-CPNs after drug release.

It is well known that water-soluble drugs could be easily leaked out from hydrophobic inner core of the nano drug carriers. However, by hydrophobic interactions, the water-insoluble drugs could be physically encapsulated and stabilized in the hydrophobic inner core of nanoparticles. Doxorubicin hydrochloride (DOX. HCl), a weak amphipathic base (pKa 8.3), is a widely used anti-cancer drug. To load DOX into nanoparticles, we first deprotonated DOX.HCl under alkaline conditions and converted it into hydrophobic DOX. Then utilizing the self-assembly of the PFV, PNIPAM and DOX, DOX-loaded thermo-responsive conjugated polymers-based nanoparticles PNIPAM-DOX-CPNs were prepared in water by a nanoprecipitation method. In this case, the results shows that DOX is successfully incorporated into polymer nanoparticles, and the drug loading content (DLC) and encapsulation efficiency (EE) are about 20% and 50% (See calculation equations in Supporting Information), respectively. Furthermore, to study the thermal-triggered release behavior of DOX from the PNIPAMDOX-CPNs, phosphate buffer saline (PBS) with the same ionic strength and different pH was


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used as dialysis medium in this work. The pH was set at both physiological pH (7.4) and lysosomal pH (5.5), and the temperature was regulated at 25 oC (below the LCST) and 37 oC (above the LCST). As shown in Figure 4B, at pH 5.5 and 37 °C, more than 70% of the loaded drugs were delivered, whereas less than 30% drugs were delivered at pH 7.4 and 25 °C. The results reveal that the DOX release rate increases with the increasing of temperature and acidity. The different release rates should result from the structure change of the thermoresponsive shell and protonation of DOX. Specifically, the hydrophilic PNIPAM segments in the shell of the nanoparticles are extended totally below the LCST and drugs are stabilized in the nanoparticles core. However, when the temperature increases above the LCST, PNIPAM become hydrophobic and collapsed, and further cause the agglomerate of nanoparticles, which can be proved by SEM of PNIPAM-DOX-CPNs after drug release (Figure 4C). In addition, the absorption and emission intensity of PNIPAM-DOX-CPNs decrease after drug release (Figure S1), which may be caused by the agglomeration of nanoparticles. The aggregation process greatly reduces interparticle space and thus squeezes out DOX. Besides, under acidic conditions, protonation of the amine moiety of DOX improves the hydrophilicity of DOX and weakens the hydrophobic interaction, which contributes to the DOX release. These results indicate that the thermo-responsive conjugated polymer nanoparticles would be potential for application in biomedicine as a drug carrier.


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Hoechst

LysoTracker

PFV

DOX

Merged

Bright field

4h

8h h

12h

16h

24h

Figure 5. Confocal laser scanning microscopy (CLSM) images of MCF-7 cells treated with 5.0 μg/mL of PNIPAM-DOX-CPNs for varying time intervals. Lysosomes were stained with Lysotracker red DND 99 and nucleus were stained with Hoechst33342. The fluorescence imaging of Hoechst 33342, PFV, DOX, and Lysotracker red DND 99 were collected at 420−460 nm (λex: 405nm), 470−510 nm (λex: 488 nm), 520−610 nm (λex: 488 nm) and 570−670 nm (λex: 559 nm), respectively. Scale bar is 40 μm.


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Tracking of drug release. Tracking of drug in cells is significant for the investigation of drugs targets and mechanism. To monitor the cell uptake of the nanoparticles and intracellular drug release, MCF-7 cells were cultured and incubated with PNIPAM-DOX-CPNs at 37 oC for 4 h. As shown in Figure 5, the weak red fluorescence of DOX and green fluorescence of PNIPAMDOX -CPNs are observed in cells and all of them match well with the cell endolysosomes that are stained by Lysotracker red DND 99. After incubation for a longer time (8 h and 12 h), red fluorescence and green fluorescence are elevated and accumulated in the lysosome region, suggesting continuous cell uptake of drug-loaded nanoparticles. During incubation within 12 h, slight red fluorescence is observed in cytoplasm, which shows only very few DOX escape from the lysosomes and enter into the cytoplasm. But after incubation for a longer time, such as 16 h and 24 h, it can be observed from the images that the deeper and stronger red fluorescence appears in cytoplasm and even in nucleus, indicating that more and more DOX molecules are released from PNIPAM-DOX-CPNs and finally internalized into the nucleus. Interestingly, the characteristic green emission of the PNIPAM-DOX-CPNs retains in the lysosome, which demonstrates that they keep in lysosome and don’t enter into the nucleus. More importantly, the green fluorescence gradually enhances with the DOX releasing due to the quenching effect of DOX for the nanoparticles being weakened, which provides the platform for tracking drug release conveniently. Moreover, the images of bright field show that the cell morphology are dramatically changed after incubating with nanoparticles for a period of time, which illustrates that cells are damaged by chemotherapy after treating with PNIPAM-DOX-CPNs.

Therefore,

the

thermo-responsive

conjugated

polymer-based


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nanoparticles are successfully used for temperature triggered release of drugs and drug release tracking.

Figure 6. The cell cytotoxicity of (A) PNIPAM-CPNs, (B) PNIPAM-DOX-CPNs and free DOX against MCF-7 for 72 h at different concentrations under white light irradiation or in the dark.

Chemo-/PDT synergistic therapy. On the basis of preferable controlled drug release behavior and ROS generation ability of NPs in the water solution, the in vitro cell toxicities of PNIPAMDOX-CPNs and PNIPAM-CPNs against two model tumor cell lines, A549 and MCF-7, were further investigated by using typical MTT assay. In a 96-well plate, the cells were seeded with a density of 5000 per well and incubated with free DOX, PNIPAM-CPNs or PNIPAM-DOXCPNs for 72 h. As shown in Figure 6A, PNIPAM-CPNs have no obvious cytotoxicity toward the MCF-7 without irradiation even the concentration increases to 10 μg/mL. However, under


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irradiation (white light, 25 mW cm−2, 30 min), PNIPAM-CPNs show significant cytotoxicity to cancer cells. The cell viability for MCF-7 is 24.6% at 10 μg/mL PNIPAM-CPNs, whereas a negligible effect on the cell viability is observed for the controls under light irradiation. These results indicate the production of ROS by PNIPAM-CPNs under white light irradiation plays a key role in cell apoptosis. Interestingly, as shown in Figure 6B, PNIPAM-DOX-CPNs show dose-dependent anticancer activities against MCF-7 without irradiation, and the cell viability decreases along with the increasing of DOX concentration. When the concentration of DOX is 2.5 μg/mL (the corresponding concentration of PNIPAM-DOX-CPNs is 10 μg/mL), the cell viability is 12.5%, which is far lower than that of PNIPAM-CPNs in dark. The enhanced cell cytotoxicity of PNIPAM-DOX-CPNs stems from the release of DOX triggered by rising temperature and low acidity in tumor cells. Moreover, the drug-loaded nanoparticles PNIPAM-DOX-CPNs have almost the same effect as free DOX, which means that the nanocarrier could indeed be used to deliver drugs. Additionally, due to the EPR effect of nanoparticles, PNIPAM-DOX-CPNs could decrease the adverse effects of chemotherapy. As shown in Figure S2A, the cell viability of MCF-7 treated with PNIPAM-DOX-CPNs for 48 h is higher than that for 72 h, which indicates the system also has the function of sustained release. Similar to PNIPAM-CPNs, PNIPAM-DOX-CPNs produce the higher cell cytotoxicity under irradiation than in dark. The cell viability of MCF-7 is only 3.2% after treating with PNIPAM-DOX-CPNs under white irradiation at 2.5 μg/mL DOX, which is much lower than that obtained from nanoparticles alone or PDT. The similar results were observed for A549 cells after treating with PNIPAM-CPNs or PNIPAM-DOX-CPNs at the same conditions


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(Figure S2B and S3). These results indicate that an enhanced therapy efficiency was achieved by combining PDT with stimuli-responsive chemotherapy based on PNIPAM-DOX-CPNs. CONCLUSION

In summary, a new multifunctional thermal-responsive nano drug delivery platform has been successfully developed based on cationic conjugated polymer PFV, temperature-responsive polymer PNIPAM and model drug DOX. The introduction of PNIPAM on the surface of nanoparticles enabled them to release drug on-demand for chemotherapy. PFV act as drug carrier and cell imaging agent for tracking drug release. Importantly, PFV act as the PDT agent in favor of chemo- and photodynamic synergistic therapy, producing the enhanced cell cytotoxicity compared to sole therapeutic effect. In a word, this thermal-responsive drug loaded nanoparticles platform provides a new method for controlling and tracking delivery of drugs, and for effective chemo- / PDT synergistic therapy.

ASSOCIATED CONTENT

Supporting Information.

The Supporting Information is available free of charge on the ACS Publications website.

Experimental section, Figure S1 - Figure S3.

AUTHOR INFORMATION Corresponding Author


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*Email: [email protected]. Tel:+86-29-81530844. ORCID

Yanli Tang: 0000-0002-9979-6808

Notes The authors declare no conflict of interest.

ACKNOWLEDGMENT We are grateful for the financial support from the National Natural Science Foundation of China (Grant 21675106), Fundamental Research Funds for the Central Universities (No. GK201901003), and the 111 Project (Grant B14041).

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