Skip to main content
SpringerLink
Log in

Self-assembled nanostructured photosensitizer with aggregation-induced emission for enhanced photodynamic anticancer therapy

具有自组装纳米结构的AIE光敏剂用于增强光动力治疗

  • Articles
  • Published:
Science China Materials Aims and scope Submit manuscript

Abstract

Three nanostructured photosensitizers with aggregation-induced emission (AIE) characteristics based on 2,3-bis(4′-(diphenylamino)-[1,1′-biphenyl]-4-yl) fumaronitrile (BDBF) were prepared for image-guided photodynamic therapy (PDT). BDBF was encapsulated with Pluronic F-127 (F127) to form usual spherical nanoparticles (F127@BDBF NPs) with a red fluorescence emission and 9.8% fluorescence quantum yield (FQY). Moreover, BDBF self-assembled into nanorods (BDBF NRs) in water. Compared with F127@BDBF NPs, BDBF NRs exhibited stronger orange fluorescence with a higher FQY of 23.3% and similar singlet oxygen (1O2) generation capability. BDBF NRs were further modified with F127 to form BDBF@F127 NRs with the same 1O2 generation ability as BDBF NRs. The three nanostructures exhibited a higher 1O2 production capacity than BDBF molecule in dissolved state and favorable stability in an aqueous solution as well as under physiological condition. In vitro photocytotoxicity experiments indicated that the three nanostructures inhibited tumor cell proliferation effectively. Therefore, to construct eligible nanostructures with a high FQY and 1O2 generation ability, simple self-assembly can serve as a valuable method to prepare photosensitizers with enhanced PDT.

摘要

基于具有聚集诱导发光(AIE)性质的2,3-双(4′-(二苯基)-[1,1′-联苯]-4-基]富甲腈(BDBF)分子, 制备了三种纳米结构并用于图像引导光动力学治疗(PDT). 普兰尼克F127可包封BDBF形成常见的球形纳米粒子(F127@BDBF NPs), 该纳米粒子可发射红色荧光, 荧光量子效率(FQY)为9.8%. 此外, BDBF也可在水中自组装成纳米棒(BDBF NRs). 与F127@BDBF NPs 相比, BDBF NRs呈现出较强的橙色荧光, 具有较高的荧光量子产率(23.3%), 以及基本相同的单线态氧(1O2)产生能力. 利用F127对BDBF NRs进行进一步修饰可得到BDBF@F127 NRs, 该纳米粒子仍然保持了棒状形貌和较好的1O2产生能力. 同时, 与溶解态的BDBF相比, 三种纳米结构的单线态氧产生效率增强. 这些纳米结构在水溶液和生理条件下具有良好的稳定性. 细胞的光毒性实验表明, 三种纳米结构均能有效抑制肿瘤细胞增殖. 因此, 通过简单的自组装方法制备高荧光量子效率和较强单线态氧产生能力的纳米结构可作为一种有效的途径来增强光动力.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Log in via an institution

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Institutional subscriptions

Similar content being viewed by others

References

  1. Felsher DW. Cancer revoked: Oncogenes as therapeutic targets. Nat Rev Cancer, 2003, 3: 375–379

    CAS  Google Scholar 

  2. Osedach TP, Andrew TL, Bulović V. Effect of synthetic accessibility on the commercial viability of organic photovoltaics. Energy Environ Sci, 2013, 6: 711

    CAS  Google Scholar 

  3. Huang P, Lin J, Wang X, et al. Light-triggered theranostics based on photosensitizer-conjugated carbon dots for simultaneous enhanced-fluorescence imaging and photodynamic therapy. Adv Mater, 2012, 24: 5104–5110

    CAS  Google Scholar 

  4. Wang H, Xie H, Wang J, et al. Self-assembling prodrugs by precise programming of molecular structures that contribute distinct stability, pharmacokinetics, and antitumor efficacy. Adv Funct Mater, 2015, 25: 4956–4965

    CAS  Google Scholar 

  5. Huang Z, Xu H, Meyers AD, et al. Photodynamic therapy for treatment of solid tumors—Potential and technical challenges. Technol Cancer Res Treat, 2008, 7: 309–320

    CAS  Google Scholar 

  6. Dougherty TJ, Gomer CJ, Henderson BW, et al. Photodynamic therapy. J Natl Cancer Institute, 1998, 90: 889–905

    CAS  Google Scholar 

  7. Wang C, Cheng L, Liu Z. Upconversion nanoparticles for photodynamic therapy and other cancer therapeutics. Theranostics, 2013, 3: 317–330

    Google Scholar 

  8. Zhou Z, Song J, Nie L, et al. Reactive oxygen species generating systems meeting challenges of photodynamic cancer therapy. Chem Soc Rev, 2016, 45: 6597–6626

    CAS  Google Scholar 

  9. Lucky SS, Soo KC, Zhang Y. Nanoparticles in photodynamic therapy. Chem Rev, 2015, 115: 1990–2042

    CAS  Google Scholar 

  10. Juarranz Á, Jaén P, Sanz-Rodríguez F, et al. Photodynamic therapy of cancer. Basic principles and applications. Clin Transl Oncol, 2008, 10: 148–154

    CAS  Google Scholar 

  11. Chang CC, Hsieh MC, Lin JC, et al. Selective photodynamic therapy based on aggregation-induced emission enhancement of fluorescent organic nanoparticles. Biomaterials, 2012, 33: 897–906

    CAS  Google Scholar 

  12. Pei Q, Hu X, Zheng X, et al. Light-activatable red blood cell membrane-camouflaged dimeric prodrug nanoparticles for synergistic photodynamic/chemotherapy. ACS Nano, 2018, 12: 1630–1641

    CAS  Google Scholar 

  13. Zheng X, Wang L, Liu S, et al. Nanoparticles of chlorin dimer with enhanced absorbance for photoacoustic imaging and phototherapy. Adv Funct Mater, 2018, 28: 1706507

    Google Scholar 

  14. He H, Zheng X, Liu S, et al. Diketopyrrolopyrrole-based carbon dots for photodynamic therapy. Nanoscale, 2018, 10: 10991–10998

    CAS  Google Scholar 

  15. Chen W, Ouyang J, Liu H, et al. Black phosphorus nanosheet-based drug delivery system for synergistic photodynamic/photothermal/chemotherapy of cancer. Adv Mater, 2017, 29: 1603864

    Google Scholar 

  16. Sun C, Ji S, Li F, et al. Diselenide-containing hyperbranched polymer with light-induced cytotoxicity. ACS Appl Mater Interfaces, 2017, 9: 12924–12929

    CAS  Google Scholar 

  17. Kessel D. Apoptosis, paraptosis and autophagy: Death and survival pathways associated with photodynamic therapy. Photochem Photobiol, 2019, 95: 119–125

    CAS  Google Scholar 

  18. Li X, Kim CY, Lee S, et al. Nanostructured phthalocyanine assemblies with protein-driven switchable photoactivities for biophotonic imaging and therapy. J Am Chem Soc, 2017, 139: 10880–10886

    CAS  Google Scholar 

  19. Yu B, Wei H, He Q, et al. Efficient uptake of 177Lu-porphyrin-PEG nanocomplexes by tumor mitochondria for multimodal-imaging-guided combination therapy. Angew Chem Int Ed, 2018, 57: 218–222

    CAS  Google Scholar 

  20. Fan W, Lu N, Xu C, et al. Enhanced afterglow performance of persistent luminescence implants for efficient repeatable photodynamic therapy. ACS Nano, 2017, 11: 5864–5872

    CAS  Google Scholar 

  21. Zhao J, Xu K, Yang W, et al. The triplet excited state of bodipy: Formation, modulation and application. Chem Soc Rev, 2015, 44: 8904–8939

    CAS  Google Scholar 

  22. Guo Z, Zou Y, He H, et al. Bifunctional platinated nanoparticles for photoinduced tumor ablation. Adv Mater, 2016, 28: 10155–10164

    CAS  Google Scholar 

  23. Ye S, Rao J, Qiu S, et al. Rational design of conjugated photosensitizers with controllable photoconversion for dually cooperative phototherapy. Adv Mater, 2018, 30: 1801216

    Google Scholar 

  24. Tang Q, Si W, Huang C, et al. An aza-bodipy photosensitizer for photoacoustic and photothermal imaging guided dual modal cancer phototherapy. J Mater Chem B, 2017, 5: 1566–1573

    CAS  Google Scholar 

  25. Cai Y, Liang P, Tang Q, et al. Diketopyrrolopyrrole—triphenylamine organic nanoparticles as multifunctional reagents for photoacoustic imaging-guided photodynamic/photothermal synergistic tumor therapy. ACS Nano, 2017, 11: 1054–1063

    CAS  Google Scholar 

  26. Singh S, Aggarwal A, Bhupathiraju NVSDK, et al. Glycosylated porphyrins, phthalocyanines, and other porphyrinoids for diagnostics and therapeutics. Chem Rev, 2015, 115: 10261–10306

    CAS  Google Scholar 

  27. Guo M, Mao H, Li Y, et al. Dual imaging-guided photothermal/photodynamic therapy using micelles. Biomaterials, 2014, 35: 4656–4666

    CAS  Google Scholar 

  28. Li X, Lee S, Yoon J. Supramolecular photosensitizers rejuvenate photodynamic therapy. Chem Soc Rev, 2018, 47: 1174–1188

    CAS  Google Scholar 

  29. Shen Y, Shuhendler AJ, Ye D, et al. Two-photon excitation nanoparticles for photodynamic therapy. Chem Soc Rev, 2016, 45: 6725–6741

    CAS  Google Scholar 

  30. Fan W, Huang P, Chen X. Overcoming the Achilles’ heel of photodynamic therapy. Chem Soc Rev, 2016, 45: 6488–6519

    CAS  Google Scholar 

  31. Zhang W, Lin W, Zheng X, et al. Comparing effects of redox sensitivity of organic nanoparticles to photodynamic activity. Chem Mater, 2017, 29: 1856–1863

    CAS  Google Scholar 

  32. Li B, Li J, Fu Y, et al. Porphyrins with four monodisperse oligofluorene arms as efficient red light-emitting materials. J Am Chem Soc, 2004, 126: 3430–3431

    CAS  Google Scholar 

  33. DeRosa M, Crutchley RJ. Photosensitized singlet oxygen and its applications. Coord Chem Rev, 2002, 233-234: 351–371

    CAS  Google Scholar 

  34. Abbas M, Zou Q, Li S, et al. Self-assembled peptide- and protein-based nanomaterials for antitumor photodynamic and photothermal therapy. Adv Mater, 2017, 29: 1605021

    Google Scholar 

  35. Luo J, Xie Z, Lam JWY, et al. Aggregation-induced emission of 1-methyl-1,2,3,4,5-pentaphenylsilole. Chem Commun, 2001, 740–1741

    Google Scholar 

  36. Mei J, Leung NLC, Kwok RTK, et al. Aggregation-induced emission: Together we shine, united we soar! Chem Rev, 2015, 115: 11718–11940

    CAS  Google Scholar 

  37. Wu W, Mao D, Hu F, et al. A highly efficient and photostable photosensitizer with near-infrared aggregation-induced emission for image-guided photodynamic anticancer therapy. Adv Mater, 2017, 29: 1700548

    Google Scholar 

  38. Mao D, Wu W, Ji S, et al. Chemiluminescence-guided cancer therapy using a chemiexcited photosensitizer. Chem, 2017, 3: 991–1007

    CAS  Google Scholar 

  39. Yuan Y, Feng G, Qin W, et al. Targeted and image-guided photodynamic cancer therapy based on organic nanoparticles with aggregation-induced emission characteristics. Chem Commun, 2014, 50: 8757–8760

    CAS  Google Scholar 

  40. Zhang R, Zhang CJ, Feng G, et al. Specific light-up probe with aggregation-induced emission for facile detection of chymase. Anal Chem, 2016, 88: 9111–9117

    CAS  Google Scholar 

  41. Gao H, Zhang X, Chen C, et al. Unity makes strength: How aggregation-induced emission luminogens advance the biomedical field. Adv Biosys, 2018, 2: 1800074

    Google Scholar 

  42. Jiang N, Shen T, Sun JZ, et al. Aggregation-induced emission: Right there shining. Sci China Mater, 2019, 62: 1227–1235

    Google Scholar 

  43. Gu B, Wu W, Xu G, et al. Precise two-photon photodynamic therapy using an efficient photosensitizer with aggregation-induced emission characteristics. Adv Mater, 2017, 29: 1701076

    Google Scholar 

  44. Liu B. Aggregation-induced emission: Materials and biomedical applications. MRS Bull, 2017, 42: 458–463

    Google Scholar 

  45. Qi J, Chen C, Zhang X, et al. Light-driven transformable optical agent with adaptive functions for boosting cancer surgery outcomes. Nat Commun, 2018, 9: 1848

    Google Scholar 

  46. Chen C, Ou H, Liu R, et al. Regulating the photophysical property of organic/polymer optical agents for promoted cancer phototheranostics. Adv Mater, 2019, 35: 1806331

    Google Scholar 

  47. Ni X, Zhang X, Duan X, et al. Near-infrared afterglow luminescent aggregation-induced emission dots with ultrahigh tumor-to-liver signal ratio for promoted image-guided cancer surgery. Nano Lett, 2018, 19: 318–330

    Google Scholar 

  48. Xu M, Wang X, Wang Q, et al. Analyte-responsive fluorescent probes with AIE characteristic based on the change of covalent bond. Sci China Mater, 2019, 62: 1236–1250

    CAS  Google Scholar 

  49. Lovell JF, Liu TWB, Chen J, et al. Activatable photosensitizers for imaging and therapy. Chem Rev, 2010, 110: 2839–2857

    CAS  Google Scholar 

  50. Yogo T, Urano Y, Ishitsuka Y, et al. Highly efficient and photostable photosensitizer based on bodipy chromophore. J Am Chem Soc, 2005, 127: 12162–12163

    CAS  Google Scholar 

  51. McDonnell SO, Hall MJ, Allen LT, et al. Supramolecular photonic therapeutic agents. J Am Chem Soc, 2005, 127: 16360–16361

    CAS  Google Scholar 

  52. Xu S, Yuan Y, Cai X, et al. Tuning the singlet-triplet energy gap: A unique approach to efficient photosensitizers with aggregation-induced emission (AIE) characteristics. Chem Sci, 2015, 6: 5824–5830

    CAS  Google Scholar 

  53. Xu S, Wu W, Cai X, et al. Highly efficient photosensitizers with aggregation-induced emission characteristics obtained through precise molecular design. Chem Commun, 2017, 53: 8727–8730

    CAS  Google Scholar 

  54. Yuan Y, Xu S, Zhang CJ, et al. Dual-targeted activatable photosensitizers with aggregation-induced emission (AIE) characteristics for image-guided photodynamic cancer cell ablation. J Mater Chem B, 2016, 4: 169–176

    CAS  Google Scholar 

  55. Wu W, Feng G, Xu S, et al. A photostable far-red/near-infrared conjugated polymer photosensitizer with aggregation-induced emission for image-guided cancer cell ablation. Macromolecules, 2016, 49: 5017–5025

    CAS  Google Scholar 

  56. Wu W, Xu S, Qi G, et al. A cross-linked conjugated polymer photosensitizer enables efficient sunlight-induced photooxidation. Angew Chem Int Ed, 2019, 58: 3062–3066

    CAS  Google Scholar 

  57. Liu S, Zhang H, Li Y, et al. Strategies to enhance the photosensitization: Polymerization and the donor-acceptor even-odd effect. Angew Chem Int Ed, 2018, 57: 15189–15193

    CAS  Google Scholar 

  58. Wang S, Wu W, Manghnani P, et al. Polymerization-enhanced two-photon photosensitization for precise photodynamic therapy. ACS Nano, 2019, 13: 3095–3105

    CAS  Google Scholar 

  59. Wu W, Mao D, Xu S, et al. Polymerization-enhanced photosensitization. Chem, 2018, 4: 1937–1951

    CAS  Google Scholar 

  60. Qi J, Chen C, Ding D, et al. Aggregation-induced emission luminogens: Union is strength, gathering illuminates healthcare. Adv Healthcare Mater, 2018, 7: 1800477

    Google Scholar 

  61. Yu CYY, Xu H, Ji S, et al. Mitochondrion-anchoring photosensitizer with aggregation-induced emission characteristics synergistically boosts the radiosensitivity of cancer cells to ionizing radiation. Adv Mater, 2017, 29: 1606167

    Google Scholar 

  62. Gao Y, Zheng QC, Xu S, et al. Theranostic nanodots with aggregation-induced emission characteristic for targeted and imageguided photodynamic therapy of hepatocellular carcinoma. Theranostics, 2019, 9: 1264–1279

    CAS  Google Scholar 

  63. Cai X, Mao D, Wang C, et al. Multifunctional liposome: A bright AIEgen-lipid conjugate with strong photosensitization. Angew Chem Int Ed, 2018, 57: 16396–16400

    CAS  Google Scholar 

  64. Feng G, Wu W, Xu S, et al. Far red/near-infrared AIE dots for image-guided photodynamic cancer cell ablation. ACS Appl Mater Interfaces, 2016, 8: 21193–21200

    CAS  Google Scholar 

  65. Fateminia SMA, Kacenauskaite L, Zhang CJ, et al. Simultaneous increase in brightness and singlet oxygen generation of an organic photosensitizer by nanocrystallization. Small, 2018, 14: 1803325

    Google Scholar 

  66. Wang J, Mao W, Lock LL, et al. The role of micelle size in tumor accumulation, penetration, and treatment. ACS Nano, 2015, 9: 7195–7206

    CAS  Google Scholar 

  67. Feng G, Mao D, Liu J, et al. Polymeric nanorods with aggregation-induced emission characteristics for enhanced cancer targeting and imaging. Nanoscale, 2018, 10: 5869–5874

    CAS  Google Scholar 

  68. Cai Y, Si W, Tang Q, et al. Small-molecule diketopyrrolopyrrole-based therapeutic nanoparticles for photoacoustic imaging-guided photothermal therapy. Nano Res, 2016, 10: 794–801

    Google Scholar 

  69. Liang P, Huang X, Wang Y, et al. Tumor-microenvironment-responsive nanoconjugate for synergistic antivascular activity and phototherapy. ACS Nano, 2018, 12: 11446–11457

    CAS  Google Scholar 

  70. Liang P, Wang Y, Wang P, et al. Triphenylamine flanked furandiketopyrrolopyrrole for multi-imaging guided photothermal/photodynamic cancer therapy. Nanoscale, 2017, 9: 18890–18896

    CAS  Google Scholar 

  71. Zhang J, Xu B, Tian W, et al. Tailoring the morphology of AIEgen fluorescent nanoparticles for optimal cellular uptake and imaging efficacy. Chem Sci, 2018, 9: 2620–2627

    CAS  Google Scholar 

  72. Han X, Bai Q, Yao L, et al. Highly efficient solid-state near-infrared emitting material based on triphenylamine and diphenylfumaronitrile with an EQE of 2.58% in nondoped organic light-emitting diode. Adv Funct Mater, 2015, 25: 7521–7529

    Google Scholar 

  73. Wang Y, Han X, Xi W, et al. Bright AIE nanoparticles with F127 encapsulation for deep-tissue three-photon intravital brain angiography. Adv Healthcare Mater, 2017, 6: 1700685

    Google Scholar 

  74. Liu W, Wang Y, Han X, et al. Fluorescence resonance energy transfer (FRET) based nanoparticles composed of AIE luminogens and NIR dyes with enhanced three-photon near-infrared emission for in vivo brain angiography. Nanoscale, 2018, 10: 10025–10032

    CAS  Google Scholar 

  75. Yu J, Zhang X, Hao X, et al. Near-infrared fluorescence imaging using organic dye nanoparticles. Biomaterials, 2014, 35: 3356–3364

    CAS  Google Scholar 

  76. Hao X, Zhou M, Zhang X, et al. Highly luminescent and photostable core—shell dye nanoparticles for high efficiency bioimaging. Chem Commun, 2014, 50: 737–739

    CAS  Google Scholar 

  77. Zheng X, Wang L, Pei Q, et al. Metal—organic framework@porous organic polymer nanocomposite for photodynamic therapy. Chem Mater, 2017, 29: 2374–2381

    CAS  Google Scholar 

Download references

Acknowledgements

This work was financially supported by the National Natural Science Foundation of China (21835001, 51773080, 21674041, 51573068, 21221063, and 81870117), the Program for Changbaishan Scholars of Jilin Province, Jilin Province project (20160101305JC), Jilin Province Science and Technology Development Plan (20190201252JC), and “Talents Cultivation Program” of Jilin University.

Author information

Authors and Affiliations

  1. State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, 130012, China

    Wenkun Han  (韩文坤), Song Zhang  (张松), Jingyu Qian  (钱靖宇), Bin Xu  (徐斌) & Wenjing Tian  (田文晶)

  2. State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, International Joint Research Laboratory of Nano-Micro Architecture Chemistry (NMAC), International Research Center for Chemistry-Medicine Joint Innovation, College of Chemistry, Jilin University, Changchun, 130012, China

    Rong Deng  (邓荣), Yangyang Du  (杜阳阳) & Fei Yan  (闫飞)

  3. State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, 130022, China

    Xiaohua Zheng  (郑孝华) & Zhigang Xie  (谢志刚)

Authors
  1. Wenkun Han  (韩文坤)
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Song Zhang  (张松)
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Rong Deng  (邓荣)
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Yangyang Du  (杜阳阳)
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. Jingyu Qian  (钱靖宇)
    View author publications

    You can also search for this author in PubMed Google Scholar

  6. Xiaohua Zheng  (郑孝华)
    View author publications

    You can also search for this author in PubMed Google Scholar

  7. Bin Xu  (徐斌)
    View author publications

    You can also search for this author in PubMed Google Scholar

  8. Zhigang Xie  (谢志刚)
    View author publications

    You can also search for this author in PubMed Google Scholar

  9. Fei Yan  (闫飞)
    View author publications

    You can also search for this author in PubMed Google Scholar

  10. Wenjing Tian  (田文晶)
    View author publications

    You can also search for this author in PubMed Google Scholar

Contributions

Han W designed and performed the experiments, analyzed data and wrote the paper; Zhang S, Deng R, Qian J and Zheng X performed partial experiments. Yan F designed partial experiments. Tian W conceived the framework of this paper and revised the paper. All authors contributed to the general discussion.

Corresponding authors

Correspondence to Fei Yan  (闫飞) or Wenjing Tian  (田文晶).

Additional information

Wenkun Han received his BSc degree from Jilin University (JLU) in 2015. He is currently a PhD candidate under the supervision of Prof. Wenjing Tian. His research interest focuses on the self-assembly fluorogens for bioimaging and anticancer applications.

Fei Yan is an associate professor in the Chemistry Department, JLU. He received his PhD degree from JLU in 2010, and worked as a postdoctoral fellow first at Ohio State University and then at the University of Minnesota during 2010–2017. His research interests include the bioinorganic chemistry, translational nanomedicine and cancer epigenetics.

Wenjing Tian received her Bachelor’s degree from the Department of Physics, JLU in 1988, and her PhD from Changchun Institute of Applied Chemistry, Chinese Academy of Sciences in 1993. She was a postdoctoral fellow at the Department of Chemistry, JLU from 1994 to 1996. She is currently a professor at the State Key Laboratory of Supramolecular Structure and Materials of JLU. Her research interest focuses on organic/polymer optoelectronic materials and devices.

Electronic supplementary material

40843_2019_9477_MOESM1_ESM.pdf

Self-assembled nanostructured photosensitizer with aggregation-induced emission for enhanced photodynamic anticancer therapy

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Han, W., Zhang, S., Deng, R. et al. Self-assembled nanostructured photosensitizer with aggregation-induced emission for enhanced photodynamic anticancer therapy. Sci. China Mater. 63, 136–146 (2020). https://doi.org/10.1007/s40843-019-9477-3

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1007/s40843-019-9477-3

Keywords

Search

Navigation