Aggregation-Induced Triplet Symmetry-Breaking Charge Separation Drives Electron Transfer for Autophagy Blockade-Enhanced Type-I Photodynamic Therapy

Abstract

Electron transfer is considered to play a critical role in the Type-I photodynamic therapy process, which offers superior performance under hypoxic conditions. However, developing efficient Type-I photosensitizers remains challenging because of the competition between energy and electron transfer processes. Therefore, we designed cyanine dyes (Cy-R) with tunable intersystem crossing (ISC) efficiencies, with the ISC rate reaching 9.29 × 10⁶ s⁻¹. Unlike conventional dimers with short-lived charge-separated states, Cy-R aggregates having sufficiently high ISC efficiency undergo symmetry-breaking charge separation (SBCS) in the triplet state, generating long-lived triplet charge-separated species (Cy-R^•+−Cy-R^•−). This mechanism significantly enhances the production of Type-I reactive oxygen species. Furthermore, Cy-Ac self-aggregation facilitated passive tumor targeting and lysosomal accumulation. Upon photoactivation, Cy-Ac induces lysosomal membrane permeabilization, disrupts autophagy, and triggers lysosome-mediated cell death. This study provides a promising strategy for the development of hypoxia-tolerant Type-I photosensitizers via triplet-state SBCS.

Keywords

charge separation / hypoxia / photodynamic therapy / photosensitizers / self-aggregation

References

[1] P.-C. Lo, M. S. Rodríguez-Morgade, R. K. Pandey, D. K. P. Ng, T. Torres, and F. Dumoulin, “The Unique Features and Promises of Phthalocyanines as Advanced Photosensitisers for Photodynamic Therapy of Cancer,” Chemical Society Reviews 49 (2020): 1041–1056.

[2] Q. Lei, H. Yuan, J. Du, et al., “Photocatalytic CO₂ Reduction With Aminoanthraquinone Organic Dyes,” Nature Communications 14 (2023): 1087.

[3] N. Corrigan, J. Yeow, P. Judzewitsch, J. Xu, and C. Boyer, “Seeing the Light: Advancing Materials Chemistry Through Photopolymerization,” Angewandte Chemie International Edition 58 (2019): 5170–5189.

[4] X. Li, J. F. Lovell, J. Yoon, and X. Chen, “Clinical Development and Potential of Photothermal and Photodynamic Therapies for Cancer,” Nature Reviews Clinical Oncology 17 (2020): 657–674.

[5] M. S. Baptista, J. Cadet, P. Di Mascio, et al., “Type I and Type II Photosensitized Oxidation Reactions: Guidelines and Mechanistic Pathways,” Photochemistry and Photobiology 93 (2017): 912–919.

[6] M. J. Y. Tayebjee, S. N. Sanders, E. Kumarasamy, L. M. Campos, M. Y. Sfeir, and D. R. McCamey, “Quintet Multiexciton Dynamics in Singlet Fission,” Nature Physics 13 (2017): 182–188.

[7] R. Schmidt, “Photosensitized Generation of Singlet Oxygen,” Photochemistry and Photobiology 82 (2006): 1161.

[8] M. L. Li, Y. J. Shao, J. H. Kim, et al., “Unimolecular Photodynamic O₂-Economizer To Overcome Hypoxia Resistance in Phototherapeutics,” Journal of the American Chemical Society 142 (2020): 5380–5388.

[9] R. Guo, H. Sun, H. B. Gobeze, et al., “A Facile Supramolecular Strategy to Switch Photodynamic Pathway and Augment ROS Production of Sensitizers for Enhanced Tumor Therapy,” Nano Today 61 (2025): 102596.

[10] Y. Zhao, X. Huang, Y. Si, et al., “Additive-Assisted Forming High-Quality Thin Films of Sn–Oxo Cluster for Nanopatterning,” ACS Applied Materials & Interfaces 16 (2024): 41659–41668.

[11] X. Li, N. Kwon, T. Guo, Z. Liu, and J. Yoon, “Innovative Strategies for Hypoxic-Tumor Photodynamic Therapy,” Angewandte Chemie International Edition 57 (2018): 11522–11531.

[12] K.-X. Teng, L.-Y. Niu, and Q.-Z. Yang, “Supramolecular Photosensitizer Enables Oxygen-Independent Generation of Hydroxyl Radicals for Photodynamic Therapy,” Journal of the American Chemical Society 145 (2023): 4081–4087.

[13] R. Wang, M. He, Z. Zhang, et al., “Photodynamic therapy promotes hypoxia-activated nitrogen mustard drug release,” Smart Molecules 2 (2024): e20240010.

[14] M. Kang, Z. Zhang, W. Xu, et al., “Good Steel Used in the Blade: Well-Tailored Type-I Photosensitizers With Aggregation-Induced Emission Characteristics for Precise Nuclear Targeting Photodynamic Therapy,” Advanced Science 8 (2021): 2100524.

[15] G. Zhang, X. Fu, D. Zhou, R. Hu, A. Qin, and B. Z. Tang, “Smart aggregation-induced emission polymers: Preparation, properties and bio-applications,” Smart Molecules 1 (2023): e20220008.

[16] K. Li, Y. Hou, J. Han, et al., “A Non-peptide-based Fluorescent Probe Capable of Sensitively Visualizing Asparagine Endopeptidase,” Chemical Communications 60 (2024): 3031–3034.

[17] J. Zhao, K. Xu, W. Yang, Z. Wang, and F. Zhong, “The Triplet Excited state of Bodipy: Formation, Modulation and Application,” Chemical Society Reviews 44 (2015): 8904–8939.

[18] Z. F. An, C. Zheng, Y. Tao, et al., “Stabilizing Triplet Excited States for Ultralong Organic Phosphorescence,” Nature Materials 14 (2015): 685–690.

[19] G. C. Bao, R. R. Deng, D. Y. Jin, and X. G. Liu, “Hidden triplet states at hybrid organic–inorganic interfaces,” Nature Reviews Materials 10 (2025): 28–43.

[20] S. D. Tilley, “Metal-Like Molecules,” Nature Catalysis 5 (2022): 359–360.

[21] H. Liu, Z. Li, X. Zhang, et al., “Phthalocyanine Aggregates as Semiconductor-Like Photocatalysts for Hypoxic-tumor Photodynamic Immunotherapy,” Nature Communications 16 (2025): 326.

[22] Z. Zhang, Z. Wei, J. Guo, et al., “Metallopolymer Strategy to Explore Hypoxic Active Narrow-bandgap Photosensitizers for Effective Cancer Photodynamic Therapy,” Nature Communications 15 (2024): 170.

[23] X. Li, Y. Liu, Q. Hu, et al., “Mitochondria-targeted and Photo-activated CO Release for Synergistic Photodynamic Therapy,” Sensors and Actuators B: Chemical 418 (2024): 136357.

[24] P. He, M. Jia, L. Yang, et al., “Zwitterionic Photosensitizer-Assembled Nanocluster Produces Efficient Photogenerated Radicals via Autoionization for Superior Antibacterial Photodynamic Therapy,” Advanced Materials 3 (2025): 2418978.

[25] J. H. Kim, T. Schembri, D. Bialas, M. Stolte, and F. Würthner, “Slip-Stacked J-Aggregate Materials for Organic Solar Cells and Photodetectors,” Advanced Materials 34 (2022): 2104678.

[26] Y. Qin, X. Chen, Y. Gui, H. Wang, B. Z. Tang, and D. Wang, “Self-Assembled Metallacage With Second Near-Infrared Aggregation-Induced Emission for Enhanced Multimodal Theranostics,” Journal of the American Chemical Society 144 (2022): 12825–12833.

[27] E. Sebastian and M. Hariharan, “Symmetry-Breaking Charge Separation in Molecular Constructs for Efficient Light Energy Conversion,” ACS Energy Letters 7 (2022): 696–711.

[28] X. Zhao, R. M. Young, C. Tang, et al., “Manipulating Symmetry-breaking Charge Separation Employing Molecular Recognition,” Chem 11 (2025): 102248.

[29] Z. Wang, W. Ma, Z. Yang, et al., “A Type I Photosensitizer-Polymersome Boosts Reactive Oxygen Species Generation by Forcing H-Aggregation for Amplifying STING Immunotherapy,” Journal of the American Chemical Society 146 (2024): 28973–28984.

[30] W. Zhang, F. Huo, F. Cheng, and C. Yin, “Employing an ICT-FRET Integration Platform for the Real-Time Tracking of SO₂ Metabolism in Cancer Cells and Tumor Models,” Journal of the American Chemical Society 142 (2020): 6324–6331.

[31] K.-X. Teng, D. Zhang, B.-K. Liu, Z.-F. Liu, L.-Y. Niu, and Q.-Z. Yang, “Photo-Induced Disproportionation-Mediated Photodynamic Therapy: Simultaneous Oxidation of Tetrahydrobiopterin and Generation of Superoxide Radicals,” Angewandte Chemie International Edition 63 12 (2024): e202318783.

[32] Y. Li, T. Ma, H. Jiang, et al., “Anionic Cyanine J-Type Aggregate Nanoparticles With Enhanced Photosensitization for Mitochondria-Targeting Tumor Phototherapy,” Angewandte Chemie International Edition 61 (2022): e202203093.

[33] X. Mu, F. Wu, Y. Tang, et al., “Boost photothermal theranostics via self-assembly-induced crystallization (SAIC),” Aggregate 3 (2022): e170.

[34] S. Pullanchery, S. Kulik, B. Rehl, A. Hassanali, and S. Roke, “Charge transfer Across C–H⋅⋅⋅O hydrogen bonds stabilizes oil droplets in water,” Science 374 (2021): 1366–1370.

[35] J. Zhuang, G. Qi, Y. Feng, et al., “Thymoquinone as an Electron Transfer Mediator to Convert Type II Photosensitizers to Type I Photosensitizers,” Nature Communications 15 (2024): 4943.

[36] D. Bialas, E. Kirchner, M. I. S. Röhr, and F. Würthner, “Perspectives in Dye Chemistry: A Rational Approach Toward Functional Materials by Understanding the Aggregate State,” Journal of the American Chemical Society 143 (2021): 4500–4518.

[37] S. Hu, K. Hu, X. Jin, et al., “Isoelectronic Substitution-Induced Intrachromophoric Symmetry-Breaking Charge Separation,” CCS Chemistry 7 (2025): 3107–3118.

[38] D. Huang, J. Yin, Y. Zou, et al., “A self-reinforced activatable photosensitizer prodrug enabling synergistic photodynamic and chemotherapy,” Smart Molecules 2 (2024): e20240005.

[39] X. Chen, F. Niu, T. Ma, Q. Li, S. Wang, and S. Shen, “Anchoring Group Regulation in Semiconductor/Molecular Complex Hybrid Photoelectrode for Photoelectrochemical Water Splitting,” Smart Molecules 3 (2024): e20240056.

[40] H. Kim, Y. R. Lee, H. Jeong, et al., “Photodynamic and Photothermal Therapies for Bacterial Infection Treatment,” Smart Molecules 1 (2023): e20220010.

[41] F. Han, X. Zhou, Z. Wang, et al., “Red-Light Triggered H-Abstraction Photoinitiators for the Efficient Oxygen-Independent Therapy of Hypoxic Tumors,” Angewandte Chemie International Edition 63 (2024): e202408769.

[42] X. Zhou, C. Shi, S. Long, et al., “Highly Efficient Photosensitizers With Molecular Vibrational Torsion for Cancer Photodynamic Therapy,” ACS Central Science 9 (2023): 1679–1691.

[43] K.-X. Teng, L.-Y. Niu, J. Li, D. Zhang, and Q.-Z. Yang, “Rational Design of Type-I Photodynamic Agents,” Angewandte Chemie International Edition 64 (2025): e202509416.

[44] Y. Arisawa, Y. Kubota, T. Inuzuka, and K. Funabiki, “Photostability and Halochromic Properties of Near-Infrared Absorbing Anionic Heptamethine Cyanine Dyes,” ChemistrySelect 7 (2022): e202104213.

[45] S. V. Popov, Y. L. Slominsky, M. L. Dekhtyar, and A. B. Rozhenko, “Synthesis, Structure, and Spectra of Merocyanines Prepared From Anionic Polymethine Dyes,” Dyes and Pigments 18 (1992): 151–162.

[46] X. Hao, M. Gao, R. Zhang, et al., “Synergistic Phototherapy Using Zwitterionic Crystalline Nanoaggregates of Orthogonal Donor–Acceptor Small-Molecule Dyads,” Advanced Functional Materials 35 (2025): 2416317.

[47] L. N. Ferguson, “The Synthesis of Aromatic Aldehydes,” Chemical Reviews 38 (1946): 227–254.

[48] J. F. Larrow, E. N. Jacobsen, Y. Gao, Y. Hong, X. Nie, and C. M. Zepp, “A Practical Method for the Large-Scale Preparation of [N,N'-Bis(3,5-di-tertbutylsalicylidene)-1,2-cyclohexanediaminato(2-)]Manganese(III) Chloride, a Highly Enantioselective Epoxidation Catalyst,” Journal of Organic Chemistry 59 (1994): 1939–1942.

[49] M. L. Deb and P. J. Bhuyan, “Uncatalysed Knoevenagel Condensation in Aqueous Medium at Room Temperature,” Tetrahedron Letters 46 (2005): 6453–6456.

[50] N. Narayanan and G. Patonay, “A New Method for the Synthesis of Heptamethine Cyanine Dyes: Synthesis of New Near-Infrared Fluorescent Labels,” The Journal of Organic Chemistry 60 (1995): 2391–2395.

[51] H. Zhao, J. Xu, C. Feng, et al., “Tailoring Aggregation Extent of Photosensitizers to Boost Phototherapy Potency for Eliciting Systemic Antitumor Immunity,” Advanced Materials 34 (2022): 2106390.

[52] R. A. Marcus and N. Sutin, “Electron Transfers in Chemistry and Biology,” Biochimica Et Biophysica Acta (BBA)—Reviews on Bioenergetics 811 (1985): 265–322.

[53] C. M. Marian, “Understanding and Controlling Intersystem Crossing in Molecules,” Annual Review of Physical Chemistry 72 (2021): 617–640.

[54] R. Englman and J. Jortner, “The Energy Gap Law for Radiationless Transitions in Large Molecules,” Molecular Physics 18 (1970): 145–164.

[55] T. Lu and F. Chen, “Multiwfn: A Multifunctional Wavefunction Analyzer,” Journal of Computational Chemistry 33 (2012): 580–592.

[56] Z. Liu, T. Lu, and Q. Chen, “An sp-hybridized All-carboatomic Ring, Cyclo[18]Carbon: Electronic Structure, Electronic Spectrum, and Optical Nonlinearity,” Carbon 165 (2020): 461–467.

[57] T. Lu, “A Comprehensive Electron Wavefunction Analysis Toolbox for Chemists, Multiwfn,” Journal of Chemical Physics 161 (2024): 082503.

RIGHTS & PERMISSIONS

2025 The Author(s). Aggregate published by SCUT, AIEI, and John Wiley & Sons Australia, Ltd.