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Acetal-Linked Hyperbranched Polyphosphoester Nanocarriers Loaded with Chlorin e6 for pH-Activatable Photodynamic Therapy Feng Li,†,⊥ Chao Chen,‡,⊥ Xixi Yang,§,⊥ Xinyu He,*,∥ Zhangyan Zhao,† Jie Li,‡ Yue Yu,*,§ Xianzhu Yang,*,∥ and Jun Wang∥ †
Department of Respiration, Shanghai Public Health Clinical Center, Fudan University, Shanghai 201508, China Department of Medical Materials and Rehabilitation Engineering, School of Biological and Medical Engineering, Hefei University of Technology, Hefei, Anhui 230009, China § Division of Gastroenterology, Affiliated Provincial Hospital, Anhui Medical University, No. 17 Lu Jiang Road, Hefei, Anhui 230001, China ∥ Institutes for Life Sciences, School of Medicine, and National Engineering Research Center for Tissue Restoration and Reconstruction, South China University of Technology, Guangzhou, Guangdong 510006, P. R. China ‡
S Supporting Information *
ABSTRACT: Nanocarrier-mediated photodynamic therapy (PDT), which involves the systemic delivery of photosensitizers (PSs) into tumor tissue and tumor cells, has emerged as an attractive treatment for cancer. However, insufficient PS release limits intracellular cytotoxic reactive oxygen species (ROS) generation, which has become a major obstacle to improving the PDT therapeutic efficacy. Herein, a novel hyperbranched polyphosphoester (hbPPE) containing numerous acetal bonds (S-hbPPE/Ce6) was explored as a chlorin e6 (Ce6) nanocarrier for PDT. S-hbPPE/Ce6 with a branched topological structure efficiently encapsulated Ce6 and then significantly enhanced its internalization by tumor cells. Subsequently, the endo-/lysosomal acid microenvironment rapidly cleaved the acetal linkage of S-hbPPE and destroyed the nanostructure of S-hbPPE/Ce6, resulting in increased Ce6 release and obviously elevated the intracellular ROS generation under illumination. Therefore, treatment with S-hbPPE/Ce6 noticeably enhanced the PDT therapeutic efficacy, indicating that such a pH-sensitive hbPPE nanocarrier has great potential to improve the PDT therapeutic efficacy for cancer therapy. KEYWORDS: hyperbranched polyphosphoester, pH-sensitive, photodynamic therapy, activatable PDT, pancreatic cancer
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INTRODUCTION Photodynamic therapy (PDT) that consists of a photosensitizer (PS), oxygen molecules, and excitation at an appropriate wavelength light is an approved therapeutic method for clinical use.1−3 The PDT therapeutic effect is limited to the illumination site, offering distinctive advantages of specific damage to the tumor tissue and minimal nonspecific toxicity to healthy tissues or cells.4−6 Much effort has been devoted to exploring advanced photosensitizing systems to improve the therapeutic efficacy of PDT.7,8 Among these systems, the general strategy is to generate more cytotoxic reactive oxygen species (ROS) within tumor cells by enhancing the accumulation of PSs in the tumor tissue.9−12 In this regard, nanocarriers, including liposomes,13−15 polymeric nanoparticles, 16−18 and inorganic nanoparticles,19−21 have been explored as the delivery systems of PSs, which can efficiently enhance the accumulation of PSs within the tumor site through the size effect, offering improved therapeutic efficacy of PDT. However, it should be noted that nanocarriers hinder the PDT efficacy of the loaded PSs © XXXX American Chemical Society
following internalization into tumor cells. Nanocarriers hindered the ROS generation by limiting the energy transfer between the excited PS and surrounding oxygen molecules.22,23 Additionally, the diffusion of the generated ROS from nanocarriers is also restricted, which subsequently inhibits the PDT efficacy because of the transient lifetime ( free Ce6, which is well consistent with the ROS generation ability within BxPC-3 cells (Figure 5B). Pharmacokinetics and PDT Therapeutic Efficacy of ShbPPE/Ce6 in Vivo. Encouraged by the superior therapeutic efficacy of S-hbPPE/Ce6 under illumination in vitro, we further evaluated its performance in vivo. The mice were treated with S-hbPPE/Ce6, inS-hbPPE/Ce6, or free Ce6, and then the plasma Ce6 concentration versus time was examined to detect the pharmacokinetics of these formulations (Figure 6A and Table S1). It could be observed that both S-hbPPE/ Ce6 and inS-hbPPE/Ce6 efficiently prolonged the circulation of Ce6 in the bloodstream compared to free Ce6, which could be due to the size and PEGylation effects. In addition, the biodistribution of these formulations was determined. The mice bearing BxPC-3 tumors were systemically administered S-hbPPE/Ce6 or inS-hbPPE/Ce6, and the Ce6 fluorescence signals were detected at the predetermined time points. Figure 6B demonstrated that the intensities of Ce6 fluorescence signals from the cells treated with S-hbPPE/Ce6 and inS-hbPPE/Ce6 were gradually enhanced, which had comparable tumor tissues. In addition, the main organs were collected and imaged at 24 h postinjection. Figure 6C further F
DOI: 10.1021/acsami.8b06758 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX
Research Article
ACS Applied Materials & Interfaces
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Rechargeable “Optical Battery” Implant for Irradiation-Free Photodynamic Therapy. Biomaterials 2018, 163, 154−162. (6) Guo, R.; Yang, G.; Feng, Z.; Zhu, Y.; Yang, P.; Song, H.; Wang, W.; Huang, P.; Zhang, J. Glutathione-Induced Amino-Activatable Micellar Photosensitization Platform for Synergistic Redox Modulation and Photodynamic Therapy. Biomater. Sci. 2018, 6, 1238− 1249. (7) Chen, Q.; Feng, L.; Liu, J.; Zhu, W.; Dong, Z.; Wu, Y.; Liu, Z. Intelligent Albumin-MnO2Nanoparticles as pH-/H2O2-Responsive Dissociable Nanocarriers to Modulate Tumor Hypoxia for Effective Combination Therapy. Adv. Mater. 2016, 28, 7129−7136. (8) Huang, L.; Li, Z.; Zhao, Y.; Zhang, Y.; Wu, S.; Zhao, J.; Han, G. Ultralow-Power Near Infrared Lamp Light Operable Targeted Organic Nanoparticle Photodynamic Therapy. J. Am. Chem. Soc. 2016, 138, 14586−14591. (9) Gao, S.; Wang, G.; Qin, Z.; Wang, X.; Zhao, G.; Ma, Q.; Zhu, L. Oxygen-Generating Hybrid Nanoparticles to Enhance Fluorescent/ Photoacoustic/Ultrasound Imaging Guided Tumor Photodynamic Therapy. Biomaterials 2017, 112, 324−335. (10) Li, X.; Kolemen, S.; Yoon, J.; Akkaya, E. U. Activatable Photosensitizers: Agents for Selective Photodynamic Therapy. Adv. Funct. Mater. 2017, 27, 1604053. (11) Park, J.; Jiang, Q.; Feng, D.; Mao, L.; Zhou, H.-C. SizeControlled Synthesis of Porphyrinic Metal-Organic Framework and Functionalization for Targeted Photodynamic Therapy. J. Am. Chem. Soc. 2016, 138, 3518−3525. (12) Zhu, W.; Dong, Z.; Fu, T.; Liu, J.; Chen, Q.; Li, Y.; Zhu, R.; Xu, L.; Liu, Z. Modulation of Hypoxia in Solid Tumor Microenvironment with MnO2Nanoparticles to Enhance Photodynamic Therapy. Adv. Funct. Mater. 2016, 26, 5490−5498. (13) Carter, K. A.; Shao, S.; Hoopes, M. I.; Luo, D.; Ahsan, B.; Grigoryants, V. M.; Song, W.; Huang, H.; Zhang, G.; Pandey, R. K.; Geng, J.; Pfeifer, B. A.; Scholes, C. P.; Ortega, J.; Karttunen, M.; Lovell, J. F. Porphyrin-Phospholipid Liposomes Permeabilized by Near-Infrared Light. Nat. Commun. 2014, 5, 3546. (14) Feng, L.; Cheng, L.; Dong, Z.; Tao, D.; Barnhart, T. E.; Cai, W.; Chen, M.; Liu, Z. Theranostic Liposomes with Hypoxia-Activated Prodrug to Effectively Destruct Hypoxic Tumors Post-Photodynamic Therapy. ACS Nano 2017, 11, 927−937. (15) Lovell, J. F.; Jin, C. S.; Huynh, E.; Jin, H.; Kim, C.; Rubinstein, J. L.; Chan, W. C. W.; Cao, W.; Wang, L. V.; Zheng, G. Porphysome Nanovesicles Generated by Porphyrin Bilayers for Use as Multimodal Biophotonic Contrast Agents. Nat. Mater. 2011, 10, 324−332. (16) Chen, H.; Tian, J.; He, W.; Guo, Z. H2O2-Activatable and O2Evolving Nanoparticles for Highly Efficient and Selective Photodynamic Therapy against Hypoxic Tumor Cells. J. Am. Chem. Soc. 2015, 137, 1539−1547. (17) Xing, R.; Liu, K.; Jiao, T.; Zhang, N.; Ma, K.; Zhang, R.; Zou, Q.; Ma, G.; Yan, X. An Injectable Self-Assembling Collagen-Gold Hybrid Hydrogel for Combinatorial Antitumor Photothermal/Photodynamic Therapy. Adv. Mater. 2016, 28, 3669−3676. (18) Gao, M.; Fan, F.; Li, D.; Yu, Y.; Mao, K.; Sun, T.; Qian, H.; Tao, W.; Yang, X. Tumor Acidity-Activatable TAT Targeted Nanomedicine for Enlarged Fluorescence/Magnetic Resonance Imaging-Guided Photodynamic Therapy. Biomaterials 2017, 133, 165−175. (19) Song, X.; Gong, H.; Yin, S.; Cheng, L.; Wang, C.; Li, Z.; Li, Y.; Wang, X.; Liu, G.; Liu, Z. Ultra-Small Iron Oxide Doped Polypyrrole Nanoparticles for In Vivo Multimodal Imaging Guided Photothermal Therapy. Adv. Funct. Mater. 2014, 24, 1194−1201. (20) Wang, H.; Yang, X.; Shao, W.; Chen, S.; Xie, J.; Zhang, X.; Wang, J.; Xie, Y. Ultrathin Black Phosphorus Nanosheets for Efficient Singlet Oxygen Generation. J. Am. Chem. Soc. 2015, 137, 11376− 11382. (21) Song, X.; Feng, L.; Liang, C.; Yang, K.; Liu, Z. Ultrasound Triggered Tumor Oxygenation with Oxygen-Shuttle Nanoperfluorocarbon to Overcome Hypoxia-Associated Resistance in Cancer Therapies. Nano Lett. 2016, 16, 6145−6153.
CONCLUSIONS Herein, a pH-sensitive hbPPE with numerous acetal linkages was successfully synthesized and then used as a nanocarrier of the PS. The obtained S-hbPPE/Ce6 had a diameter of 110 nm. S-hbPPE/Ce6 significantly prolonged the circulation and enhanced the tumor accumulation of Ce6. Within tumor cells, the release of Ce6 was rapidly accelerated because the acetal linkage was rapidly cleaved by the endo-/lysosomal acid microenvironment, resulting in further elevated intracellular ROS generation under illumination. Therefore, administration of S-hbPPE/Ce6 plus illumination significantly improved tumor growth inhibition, exhibiting great potential of such pH-sensitive polymers as PS nanocarriers for improved PDT therapeutic efficacy.
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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/acsami.8b06758. H NMR of S-hbPPE and inS-hbPPE, fluorescence spectrum of S-hbPPE/Ce6 and inS-hbPPE/Ce6, tumor images, body weights of mice, and H&E analysis of different organs (PDF)
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AUTHOR INFORMATION
Corresponding Authors
*E-mail:
[email protected] (X. He). *E-mail:
[email protected] (Y. Yu). *E-mail:
[email protected] (X. Yang). ORCID
Xianzhu Yang: 0000-0002-1006-0950 Author Contributions ⊥
F. Li, C. Chen, and X. Yang contributed equally to this work.
Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS This work was supported by the National Key R&D Program of China (2017YFA0205601), the Program for Guangdong Introducing Innovative and Enterpreneurial Teams (2017ZT07S054), National Natural Science Foundation of China (51473043, 51773067), the Natural Science Foundation for Distinguished Young Scholars of Guangdong Province (2017B030306002), and the Fundamental Research Funds for the Central Universities.
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DOI: 10.1021/acsami.8b06758 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX
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DOI: 10.1021/acsami.8b06758 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX
