Enhancing Photodynamic Therapy Efficacy by Using Fluorinated

Jan 13, 2016 - The production of reactive oxygen species is highly dependent on oxygen concentration, and thus, the therapeutic efficacy of PDT would ...
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Enhancing Photodynamic Therapy Efficacy by Using Fluorinated Nanoplatform Yurong Que,† Yajing Liu,‡ Wei Tan,† Chun Feng,*,† Ping Shi,‡ Yongjun Li,† and XiaoyuHuang*,† †

Key Laboratory of Synthetic and Self-Assembly Chemistry for Organic Functional Molecules, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, People’s Republic of China ‡ State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, People’s Republic of China S Supporting Information *

ABSTRACT: Photodynamic therapy (PDT) is a noninvasive therapeutic modality with fast healing process and little or no scarring. The production of reactive oxygen species is highly dependent on oxygen concentration, and thus, the therapeutic efficacy of PDT would be retarded by inefficient oxygen supply in hypoxic tumor cell and the oxygen self-consuming mechanism of PDT. It is well-known that perfluorocarbons are endowed with properties of enhanced oxygen solubility and transfer capacity. Herein, we prepared a series of nanoplatforms of spherical micelles with different ratios of pentafluorophenyl to porphyrin in the core and utilized these micelles as models to examine the influence of content of fluorinated segments on the PDT effect of porphyrins. It was found for the first time, as far as we are aware, that the production efficacy of singlet oxygen increased with the rising in the ratio of pentafluorophenyl to porphyrin. Thus, this work presents a new avenue to improve PDT efficacy by enhancing oxygen solubility and diffusivity of nanoplatforms with the incorporation of perfluorocarbon segments. ince photodynamic therapy (PDT) was first approved for the treatment of bladder cancer in 1993, it has been widely utilized as a therapeutic modality for many localized and superficial cancers.1,2 PDT combines three nontoxic components, a photosensitizer (PS), a proper light source, and tissue oxygen, where energy is transferred from the light-excited PS to surrounding oxygen and other molecules in the tissue to generate cytotoxic reactive oxygen species (ROS), especially singlet oxygen (1O2). Because many PSs are amphiphilic or hydrophobic, they tend to aggregate in aqueous environment. This would not only lead to insufficient uptake of PSs by tumors, but result in a significant decrease in PDT efficacy. Hence, various delivery platforms have been employed for the transport of water-insoluble PSs.3−6 Among these platforms, polymeric micelle-based nanocarriers have been widely utilized to selectively deliver PSs to tumors via the enhanced permeation and retention (EPR) effect.7−9 Although these nanocarriers could solubilize PSs in the core of micelle and prevent the aggregation of PSs, the core of micelle where the PSs locate, would impede the diffusion of oxygen. Tissue oxygen is one of three key components of PDT, and thus, effects of almost all PDT are oxygen-dependent so that photosensitization typically can not occur in anoxia areas of tissue.1 The efficiency of oxygen supply from surrounding tissues to the areas of photosensitizer localization is dependent on diffusivity of oxygen. In addition, because of the high reactivity and short half-life of ROS, only cells or tissues

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proximal to the areas of photosensitizer localization, where generated ROS could reach via diffusion, can be affected by PDT.10 The diffusion distance of ROS is highly dependent on its diffusivity. Furthermore, it is well recognized that hypoxic is one characteristic feature of solid tumors and tissue oxygen would be consumed continuously during PDT process.11,12 The hypoxia microenvironment within a tumor and the continuous consumption of O2 by PDT would be detrimental to photosensitization and severely reduce the efficiency of PDT. Although strategies of a lower photosensitizer dose rate and fractionated light dose can lead to high overall PDT efficacy by sacrificing its instant PDT efficacy, this would increase the time of treatment to some extent.1 Increased delivery of oxygen by the inhalation of pure oxygen at high pressure during PDT was also employed in an attempt to increase oxygen supply and overcome tumor hypoxia.13,14 However, marginal benefits were observed due to the temporary cessation of blood flow during PDT. Perfluorocarbons (PFCs) consist of carbon chains with complete fluorination of the carbon skeleton, where the high electronegativity of fluorine endows PFCs with excellent oxygen affinity.15,16 Therefore, oxygen solubility and diffusivity in various PFCs are much higher than those in hydrocarbonReceived: December 21, 2015 Accepted: January 11, 2016 Published: January 13, 2016 168

DOI: 10.1021/acsmacrolett.5b00935 ACS Macro Lett. 2016, 5, 168−173

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For this purpose, we first synthesized a diblock copolymer of PEG-b-PPFMA by RAFT polymerization, using a PEG-based macroRAFT chain transfer agent (Mn,NMR = 2250 g/mol, Mw/ Mn = 1.03). Role of PEG component was to serve as a watersoluble corona to stabilize the micelles formed by PEG-bPPFMA in aqueous media. Details about the synthesis and characterization of PEG-b-PPFMA are provided in Supporting Information. The average number of PFMA repeated unit in the copolymer was estimated to be 12 based on 1H NMR (Figure S2B) and average length of PEG block (45). Porphyrin functionality, a typical photosensitizer for PDT, was then installed into the copolymer as a model photosensitizer by amidation reaction between pentafluorophenyl ester and 5,10,15,20-tetrakis(4-aminophenyl) porphyrin (Scheme 1), which was monitored by 19F NMR (Figure S3A). Four amino groups in 5,10,15,20-tetrakis(4-aminophenyl) porphyrin not only provided a pathway for facile incorporation of porphyrin, but led to partly freezing of porphyrin by its four anchoring sites so as to avoid its aggregation and self-quenching of the excited state to a certain extent.22 The appearance of typical signals attributed to porphyrin in 1H NMR (Figure S4A) and pentafluorophenol in 19 F NMR (Figure S3A) spectra demonstrated the successful introduction of porphyrin. The extinction coefficient of porphyrin at 430 nm (ε430) was obtained from UV/vis absorbance standard curve (Figure S5) with a value of 1.84 × 105 M−1cm−1; therefore, the content of porphyrin in the copolymer was evaluated to be 0.4 porphyrin per chain via UV/vis spectroscopy and ε430, consistent with the result obtained from 1H NMR (Figure S4A). Subsequently, amidation reactions between benzylamine and pentafluorophenyl ester monitored by 19F NMR (Figure S3B,C) were employed to prepare the copolymers with different contents of pentafluorophenyl by the replacement of pentafluorophenyl with benzyl (Scheme 1).20 The details about the composition of obtained polymers are listed in Table 1. TEM images of

based compounds and water.17−19 Inspired by these special properties of highly enhanced oxygen solubility and diffusivity of PFCs, we hypothesized that the incorporation of fluorinated segments into the core of polymeric micelle nanocarriers would not only solubilize the PSs, but significantly increase the local oxygen concentration surrounding PSs and improve the diffusivity of oxygen (3O2) and singlet oxygen (1O2). Thus, the incorporation of fluorinated segments might have positive effect on the efficacy of PDT. Herein, in order to testify this hypothesis and explore the effect of content of fluorinated segment on the efficacy of PDT, we prepared a series of spherical micelles with different ratios of pentafluorophenyl to porphyrin in the core formed by the self-assembly of PEGbased amphiphilic copolymers (Scheme 1). It was found for the Scheme 1. Synthesis of PEG-Based Amphiphilic Copolymers Containing Porphyrin, Pentafluorophenyl, or Benzyl by RAFT Polymerization and Postpolymerization Functionalization

Table 1. Composition of PEG-Based Copolymers first time that the efficacy of PDT was highly dependent on the ratio of pentafluorophenyl to porphyrin and a higher content of pentafluorophenyl led to a more efficient production of ROS. Although, a great deal of advances in PDT have been achieved in the past decade, and a variety of photosensitizers and their delivery systems were developed for enhancing selectivity and efficacy of PDT, there has been an effort to increase the efficacy of PDT for more efficient treatment of cancers.1−10 The information presented in this study not only exhibited the importance of the surrounding photosensitizer located on PDT efficacy, but provided some experimental guides for rational design of photosensitizer delivery system by the incorporation of fluorinated segment to obtain a high PDT efficacy. In our experimental design, fluorine-containing nanoparticles with different ratios of pentafluorophenyl to porphyrin in the core would be prepared as models to examine the influence of PPFMA on the production of ROS by photodynamic effect of porphyrin. The reasons for choosing pentafluorophenyl as fluorinated segment were 2-fold. First, similar to other PFCs, pentafluorophenyl has a high activity in dissolution of oxygen.20 second, pentafluorophenyl ester has a high reactivity toward amino group,21 which will lead to a great variety of conjugates for introducing photosensitizers and tuning the composition of core of micelles.

sample

NEG/NPFMA/NBMA/Nporphyrina

PEG-b-PPFMA PEG-b-PPFMA/porphyrin PEG-b-(PPFMA-co-PBMA)/porphyrin PEG-b-PBMA/porphyrin

45:12:0:0 45:10:0:0.4 45:5:5:0.4 45:0:10:0.4

a

Ratios of PFMA to EG and benzyl were obtained from 1H and 19F NMR, respectively. Ratio of EG to porphyrin was calculated based on extinction coefficient of porphyrin.

micelles formed by above-mentioned four copolymers (Figure S6) indicated spheres for all copolymers. DLS results showed that the hydrodynamic diameters of spheres (Dh) formed by PEG-b-PPFMA, PEG-b-PPFMA/porphyrin, PEG-b-(PPFMAco-PBMA)/porphyrin, and PEG-b-PBMA/porphyrin were 17.3, 28.2, 28.3, and 28.2 nm, respectively (Figure S7). UV/vis absorption and fluorescence spectra of 5,10,15,20tetrakis(4-aminophenyl)porphyrin, PEG-b-PPFMA/porphyrin, PEG-b-(PPFMA-co-PBMA)/porphyrin, and PEG-b-PBMA/ porphyrin in THF, a good solvent for porphyrin and copolymers, are shown in Figure 1A and B, respectively. One can see from Figure 1A that all samples possessed a very similar Soret band at 431 nm and three Q bands at 524, 566, and 662 nm in UV/vis spectra. Their fluorescence intensities at 672 nm are almost same (Figure 1B). UV/vis spectra of micellar solutions of PEG-b-PPFMA/porphyrin and PEG-b-(PPFMA169

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Figure 1. (A) UV/vis and (B) fluorescence spectra of 5,10,15,20-tetrakis(4-aminophenyl) porphyrin (red), PEG-b-PPFMA/porphyrin (magenta), PEG-b-(PPFMA-co-PBMA)/porphyrin (blue), and PEG-b-PBMA/porphyrin (olive) in THF; (C) UV/vis and (D) fluorescence spectra of aqueous micellar solutions of PEG-b-PPFMA/porphyrin (red), PEG-b-(PPFMA-co-PBMA)/porphyrin (olive), and PEG-b-PBMA/porphyrin (blue), [porphyrin] = 0.008 mmol/L, λex = 430 nm.

co-PBMA)/porphyrin were very similar and Soret bands were both located at 433 nm (Figure 1C), while a 4 nm red-shift was observed for PEG-b-PBMA/porphyrin (Figure 1C), whose Soret band appeared at 437 nm. The fluorescence intensities at about 669 nm for PEG-b-PPFMA/porphyrin, PEG-b-(PPFMAco-PBMA)/porphyrin, and PEG-b-PBMA/porphyrin are 670, 1162, and 555, respectively. Previous reports showed that porphyrin was apt to form face-to-face H-type aggregation in a poor solvent and the aggregation would lead to a red-shift in absorption spectrum and a significant decrease in fluorescence.23,24 The red-shift combined with the obvious decrease in fluorescence intensity indicated that porphyrin located in the core of micelles formed by PEG-b-PBMA/porphyrin had a stronger tendency to aggregate compared to PEG-b-PPFMA/ porphyrin and PEG-b-(PPFMA-co-PBMA)/porphyrin. Additionally, in aqueous media, porphyrins were located in the core of micelles with different contents of PPFMA, not surrounded by solvent as in THF. The intersystem crossing (ISC) from the photoexcited singlet to the photoexcited triplet state would be promoted within matrices containing heavy atoms of F due to heavy atom effect.25,26 Therefore, the fluorescence intensity of PEG-b-PPFMA/porphyrin was lower than that of PEG-b(PPFMA-co-PBMA)/porphyrin. Even so, the fluorescence intensities of PEG-b-PPFMA/porphyrin and PEG-b-(PPFMAco-PBMA)/porphyrin were still higher than that of fluorineabsent PEG-b-PBMA/porphyrin, which indicated that the aggregation effect was more pronounced than heavy atom effect on the fluorescence in these systems. The efficacy of 1O2 production of micelles formed by PEG-bPPFMA, PEG-b-PPFMA/porphyrin, PEG-b-(PPFMA-coPBMA)/porphyrin, and PEG-b-PBMA/porphyrin with irradiation at 655 nm was evaluated by the oxidation reaction of 9,10-anthracemediyl-bis(methylene)dimalonic acid (ABDA), a sensitive and widely used 1O2 detection reagent.27 During this investigation, micelles formed by PEG-b-PPFMA without porphyrin in the core were employed as a negative control. In order to quantitatively evaluate the influence of content of PPFMA segment, the contents of porphyrin in micellar solutions of PEG-b-PPFMA/porphyrin, PEG-b-(PPFMA-coPBMA)/porphyrin, and PEG-b-PBMA/porphyrin were first normalized to be 0.008 mmol/L based on the extinction coefficient of porphyrin (1.84 × 105 M−1 cm−1). Since the contents of porphyrin in PEG-b-PPFMA/porphyrin, PEG-b(PPFMA-co-PBMA)/porphyrin, and PEG-b-PBMA/porphyrin were the same, the main difference was the content of PPFMA within the core for each micellar solution. Figure 2A shows typical absorption spectra of ABDA in the micellar solution of

Figure 2. (A) UV/vis absorption spectra of ABDA in micellar solution of PEG-b-PPFMA/porphyrin under irradiation at 655 nm (1.52 mW/ cm2) with different time after aerating with oxygen for 15 min and (B) the change of UV/vis absorbance of ABDA at 378 nm against irradiation time for the micelle solutions of PEG-b-PPFMA (magenta), PEG-b-PPFMA/porphyrin (red), PEG-b-(PPFMA-co-PBMA)/porphyrin (olive), PEG-b-PBMA/porphyrin (blue), and PEG-bPPClMA/porphyrin (purple) with aerating with oxygen; [porphyrin] = 0.008 mmol/L, [ABDA] = 0.06 mmol/L.

PEG-b-PPFMA/porphyrin with different exposure time to a LED light source (λmax = 655 nm, 1.52 mW/cm2) after the solution was fully aerated with oxygen for 15 min. The change of absorbance at 378 nm was plotted against the irradiation time for the micellar solutions of PEG-b-PPFMA, PEG-bPPFMA/porphyrin, PEG-b-(PPFMA-co-PBMA)/porphyrin, and PEG-b-PBMA/porphyrin, as shown in Figure 2B. One can clearly notice that no 1O2 was produced for the micellar solution of PEG-b-PPFMA without porphyrin in the core, which meant that PEG-b-PPFMA itself can not convert 3O2 to 1 O2. For other micelles with porphyrin in the core, the production efficiency was significantly dependent on the content of PPFMA. For the micellar solution of PEG-bPBMA/porphyrin without PPFMA segment, the change of absorbance at 378 nm was 0.50; it increased to 0.66 and 0.82 for the micellar solutions of PEG-b-(PPFMA-co-PBMA)/ porphyrin and PEG-b-PPFMA/porphyrin after irradiation for 80 min, respectively. This indicated that 50, 66, and 82% of ABDA were oxidized by 1O2. If we assumed that all 1O2 produced were trapped by ABDA, about 0.05, 0.04, and 0.03 mmol/L of 1O2 were generated for micellar solutions of PEG-bPPFMA/porphyrin, PEG-b-(PPFMA-co-PBMA)/porphyrin, and PEG-b-PBMA/porphyrin under the irradiation of 80 min based on the extinction coefficient of ABDA (ε378 = 1.14 × 104 M−1 cm−1, Figure S8). We also examined 1O2 production efficiency of these micellar solutions without aeration of oxygen at the irradiation at 655 (Figure S9) and 430 nm (Figure S10), 170

DOI: 10.1021/acsmacrolett.5b00935 ACS Macro Lett. 2016, 5, 168−173

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ACS Macro Letters where the 1O2 production efficiency was also dependent on the content of PPFMA. Particle size is one of critical factors affecting oxygen mass transfer and increased particle size would result in decrease in oxygen diffusion.28 Both the average size and size distribution of micelles formed by PEG-b-PPFMA/porphyrin, PEG-b(PPFMA-co-PBMA)/porphyrin, and PEG-b-PBMA/porphyrin were very close, as shown in Figure S7. Thus, the size effect could be excluded for different PDT efficacy of micelles. UV/vis and fluorescence spectra (Figure 1C,D) indicated that porphyrin within the core of micelles formed by PEG-bPBMA/porphyrin might have a higher tendency to aggregate. This would partly account for a lower PDT efficacy for PEG-bPBMA/porphyrin. However, UV/vis spectra of micellar solutions of PEG-b-PPFMA/porphyrin and PEG-b-(PPFMAco-PBMA)/porphyrin almost overlapped. Thus, the aggregation effect should not be responsible for the different PDT efficacy of PEG-b-PPFMA/porphyrin and PEG-b-(PPFMA-co-PBMA)/ porphyrin. In order to examine the influence of content of PPFMA on oxygen solubility and diffusivity, the porphyrin moieties in copolymers were loaded with Pd to obtain PEG-b-PPFMA/ porphyrin-Pd, PEG-b-(PPFMA-co-PBMA)/porphyrin-Pd, and PEG-b-PBMA/porphyrin-Pd (Scheme S2), respectively, in which porphyrin-Pd is a widely used oxygen sensor.29 On the basis of Stern−Volmer relationship, the ratio of fluorescence intensities of porphyrin-Pd in the absence and presence of oxygen quencher (I0/I) could reflect the solubility and diffusivity of oxygen within the micelle and a higher oxygen solubility and diffusivity would lead to a higher I0/I.30 Figure 3A shows typical fluorescence spectra of micelle solution of PEG-bPPFMA/porphyrin-Pd by alternating aeration of O2 and N2. It shows good reversibility of fluorescence of porphyrin-Pd to O2 quencher. Average values of I0/I were 78, 39, and 16 for PEG-b-

PPFMA/porphyrin-Pd, PEG-b-(PPFMA-co-PBMA)/porphyrin-Pd, and PEG-b-PBMA/porphyrin-Pd, respectively (Figure 3B). Although the content of micelles was about 0.1 mg/mL in water and only a small part of core of micelle was with perfluorination, I0/I of PEG-b-PPFMA/porphyrin-Pd, PEG-b(PPFMA-co-PBMA)/porphyrin-Pd were 4.9 and 2.4× that of PEG-b-PBMA/porphyrin-Pd, respectively. These results might indicate that oxygen solubility and diffusivity was highly enhanced due to the incorporation of fluorinated segments and a higher PPFMA content resulted in higher oxygen solubility and diffusivity (Figure 3C), which was consistent with previous results.31,32 The heavy atom effect could enhance with the rising of the content of PPFMA segment.25 This would result in the increase in the rate of ISC and, thus, improving the 1O2 production efficiency.26 In order to check whether heavy atom effect was the dominant factor for the increase in 1O2 production efficiency, pentachlorophenyl functionalities were introduced into the copolymer by the complete replacement of pentafluorophenyl groups of PEG-b-PPFMA/porphyrin to give PEG-b-PPClMA/porphyrin (Scheme S1). Under similar conditions, the change of absorbance at 378 nm was 0.70 for PEG-b-PPClMA/porphyrin (Figure 2B), which was lower than that of PEG-b-PPFMA/porphyrin (0.82), but higher than those of PEG-b-(PPFMA-co-PBMA)/porphyrin (0.66) and PEG-bPBMA/porphyrin (0.50). Since the absorption spectrum of micellar solution of PEG-b-PPClMA/porphyrin almost overlapped with that of PEG-b-(PPFMA-co-PBMA)/porphyrin (Figure S11), there was no difference in the degree of aggregation of porphyrins. PEG-b-PPClMA/porphyrin-Pd was also prepared to evaluate the influence of pentachlorophenyl group on the solubility and diffusivity of oxygen (Figure 3B). Average value of I0/I of PEG-b-PPClMA/porphyrin-Pd was 25, higher than that of PEG-b-PBMA/porphyrin-Pd (16), but much lower than those of PEG-b-PPFMA/porphyrin-Pd (78) and PEG-b-(PPFMA-co-PBMA)/porphyrin-Pd (39). Although the oxygen solubility and diffusivity of PEG-b-PPClMA/ porphyrin was much lower than that of PEG-b-(PPFMA-coPBMA)/porphyrin, its 1O2 production efficiency was still comparable to that of PEG-b-(PPFMA-co-PBMA)/porphyrin. Additionally, the fluorescence intensity of PEG-b-PPClMA/ porphyrin was lower than that of PEG-b-(PPFMA)/porphyrin. (Figure S12). Thus, the contribution of heavy atom effect to the increase of 1O2 production efficiency could not be excluded. However, 1O2 production efficiency of PEG-b-PPClMA/ porphyrin was much lower than that of PEG-b-PPFMA/ porphyrin. This meant that though the heavy atom effect of PEG-b-PPClMA/porphyrin should be more pronounced than that of PEG-b-PPFMA/porphyrin, the effect of increase in solubility and diffusivity of oxygen overwhelmed the heavy atom effect in the improvement of singlet oxygen production efficiency. One might argue that the photodegradation of porphyrin might be less as the decrease in the content of PPFMA segment since PPFMA domains might protect the porphyrins from photodegradation. To make this clear, we measured the absorption spectra of these micellar solutions (Figure S14), which showed that the maximum absorbance at about 430 nm was reduced to 0.92, 0.93, and 0.94 for micellar solutions of PEG-b-PPFMA/porphyrin, PEG-b-(PPFMA-co-PBMA)/porphyrin, and PEG-b-PBMA/porphyrin, respectively, after the irradiation for 80 min. This result indicated that the photodegradation of the porphyrin in PEG-b-PBMA/porphyrin

Figure 3. (A) Fluorescence spectra of micellar solution of PEG-bPPFMA/porphyrin-Pd by alternating aeration of O2 and N2; (B) The ratio of fluorescence intensities in the absence and presence of oxygen quencher (I0/I) for PEG-b-PPFMA/porphyrin-Pd(red), PEG-b(PPFMA-co-PBMA)/porphyrin-Pd(olive), PEG-b-PBMA/porphyrinPd (blue), and PEG-b-PPClMA/porphyrin-Pd (magenta); (C) Schematic illustration of possible mechanism for enhancing PDT efficacy by fluorinated domains. 171

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production efficacy of 1O2 increased with the rising in the content of pentafluorophenyl within the core of micelles, probably due to the increase in oxygen solubility and diffusivity, the enhancement in heavy atom effect, and the hindrance in aggregation of porphyrin with the content of PPFMA moiety. Given an obvious enhancement of PDT by the incorporation of fluorinated segment and relative ease in its introduction, this work undoubtedly provides a new approach for designing, preparing, and optimizing nanoplatform for more efficient cancer treatment by PDT.

was less than those of PEG-b-PPFMA/porphyrin and PEG-b(PPFMA-co-PBMA)/porphyrin, probably due to its slower rate in the production of singlet oxygen. Thus, we could exclude the possibility that the perfluorinated aromatic rings may protect the photosensitizer from photodegration and contribute to the increase in singlet oxygen production. In summary, the increase in 1O2 production efficiency with the rising of the content of PPFMA segment might result from the increase in oxygen solubility and diffusivity, the enhancement in heavy atom effect, and the hindrance in aggregation of porphyrin with the content of PPFMA moiety, where the effect of oxygen solubility and diffusivity should be the dominant factor for the improvement in 1O2 production efficiency. Finally, we performed proof-of-concept in vitro experiments on the examination of photocytotoxicity of micelles formed by PEG-b-PPFMA, PEG-b-PPFMA/porphyrin, PEG-b-(PPFMAco-PBMA)/porphyrin, and PEG-b-PBMA/porphyrin against SMMC-7721 cells (a human hepatoma cell line), as shown in Figure 4. For PEG-b-PPFMA as a blank control, it was

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsmacrolett.5b00935. Experimental details for the polymer synthesis, determination of extinction coefficients of porphyrin and ABDA, ROS generation and cytotoxicity with or without light illumination, GPC, 19F and 1H NMR spectra of the obtained copolymers, TEM and DLS of aqueous micellar solutions of obtained copolymers, and PDT efficacy study without aerating with oxygen (PDF).

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AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected]. Tel.: +86-21-54925520. Fax: +86-21-64166128. *E-mail: [email protected]. Tel.: +86-21-54925310. Fax: +86-21-64166128. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The authors thank the financial support from National Basic Research Program of China (2015CB931900), National Natural Science Foundation of China (21504102 and 21474127), and Shanghai Scientific and Technological Innovation Project (13ZR1464800, 14JC1493400, 14QA1404500, and 14520720100).

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Figure 4. Cytotoxicity and phototoxicity of PEG-b-PPFMA, PEG-bPPFMA/porphyrin, PEG-b-(PPFMA-co-PBMA)/porphyrin, and PEGb-PBMA/porphyrin against SMMC-7721 cells in darkness and irradiation upon red light (655 nm, 1.52 mW/cm2); [polymer] = 10 μg/L.

REFERENCES

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noncytotoxic in darkness and with irradiation upon red light (λmax = 655 nm, 1.52 mW/cm2) for 60 min; while for PEG-bPPFMA/porphyrin, PEG-b-(PPFMA-co-PBMA)/porphyrin, and PEG-b-PBMA/porphyrin, they were all noncytotoxic in the darkness, but exhibited substantial cytotoxicity upon illumination with the light. The cell viability reduced from 33% (PEG-b-PBMA/porphyrin) to 29% (PEG-b-(PPFMA-coPBMA)/porphyrin) and 23% (PEG-b-PPFMA/porphyrin). Obviously, the cytotoxic effect can be enhanced with the increase in the content of PPFMA segment within the core of micelles. In summary, we prepared a series of nanosized spherical micelles with different ratios of pentafluorophenyl to porphyrin in the core and utilized these spherical micelles as models to investigate the influence of the content of fluorinated segment on PDT effect of porphyrin. The results demonstrated that the 172

DOI: 10.1021/acsmacrolett.5b00935 ACS Macro Lett. 2016, 5, 168−173

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DOI: 10.1021/acsmacrolett.5b00935 ACS Macro Lett. 2016, 5, 168−173