Strategies to Improve Photodynamic Therapy Efficacy of Metal-Free Semiconducting Conjugated Polymers

Figures & data

Figure 1 Timeline of SCPs for PDT.

Figure 2 (A) Schematic illustration of SCPs photophysical and photochemical basis of PDT. (B) Reduction potential diagram of reactive oxygen species.

Table 1 Bandgap of SCPs

SCPs	Bandgap (eV)	Reference
Polyaniline	2.90	[^Citation33]
Polythiophene	2.10	[^Citation34]
Ladder-type polythiophene	1.50–1.60	[^Citation34]
Polystyrene pyridine copolymer	2.00–2.55	[^Citation35]
Polystyrene Pyridine thiophene terpolymer	1.95–2.31	[^Citation35]
Fluorene-based copolymers	1.95–2.00	[^Citation36]
Poly(4,7-dithien–2-yl-2,1,3-benzothiadiazole)	1.10	[^Citation37]
Polypyridine	2.06	[^Citation38]
Polypyrrole	2.33–2.39	[^Citation39]
Polyacetylene	1.35	[^Citation40]
Fullerene	0.85–1.24	[^Citation41]
Black phosphorus	0.30–2.00	[^Citation42]
g-C3N4	2.70	[^Citation43]
Porphyrin-based COF	1.60	[^Citation44]

Abbreviations: COF, covalent organic framework; SCP, semiconducting conjugated polymers.

Figure 3 Chemical structures of SCPs for PDT (electron acceptors are shown in blue; electron donors are shown in red).

Figure 4 Chemical structures and singlet and triplet energy levels of three model compounds.

Notes: Reproduced with permission from: Wang S, Wu W, Manghnani P, et al. Polymerization-enhanced two-photon photosensitization for precise photodynamic therapy. ACS Nano. 2019;13(3):3095–3105.⁵⁷ Copyright © 2019, American Chemical Society.

Figure 5 Chemical structures of SCPs (electron acceptors are shown in blue; electron donors are shown in red).

Figure 6 Chemical structures of SCPs for PDT.

Figure 7 Chemical structures of SCPs.

Figure 8 (A) Schematic illustration of P44 for hypoxia-activated synergistic PDT and chemotherapy. Reproduced from: Cui D, Huang J, Zhen X, Li J, Jiang Y, Pu K. A semiconducting polymer nano-prodrug for hypoxia-activated photodynamic cancer therapy. Angew Chem Int. 2019;58(18):5920–5924.⁷⁶ Copyright © 2019 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim. (B) Schematic illustration of the self-regulated photodynamic properties of P48 at physiologically neutral, pathologically acid conditions and comparison between self-regulated and conventional. Reproduced with permission from: Zhu H, Fang Y, Miao Q, et al. Regulating near-infrared photodynamic properties of semiconducting polymer nanotheranostics for optimized cancer therapy. ACS Nano. 2017;11(9):8998–9009.⁷⁹ Copyright © 2017, American Chemical Society.

Figure 9 The scheme for synthesis of COP-P-SO₃H.

Notes: Reproduced with permission from: Xiang Z, Zhu L, Qi L, et al. Two-dimensional fully conjugated polymeric photosensitizers for advanced photodynamic therapy. Chem Mater. 2016;28(23):8651–8658.²⁸ Copyright © 2016, American Chemical Society.

Figure 10 Syntheses of precursors and COFs (precursors of connection unit are shown in blue).

Notes: Reproduced with permission from: Hynek J, Zelenka J, Rathouský J, et al. Designing porphyrinic covalent organic frameworks for the photodynamic inactivation of bacteria. ACS Appl Mater Interfaces. 2018;10(10):8527–8535.¹³⁸ Copyright © 2018, American Chemical Society.

Table 2 Summary of Oxygen-Generating Strategies for Tumor Oxygenation

Materials	O2 Generation Mechanism	Reference
g-C3N4	Water splitting	[^Citation149]
CeOx	Ce^4+ convert H2O2 to H2O and O2	[^Citation153]
Metformin	Inhibition of the respiration of tumor cells	[^Citation153]
Catalase	Catalytic degradation of H2O2	[^Citation150]
Fe-doped-C3N4	Catalytic degradation of H2O2	[^Citation151]
MnO2	Catalytic degradation of H2O2	[^Citation152]
Heme	Catalytic degradation of H2O2	[^Citation161]
Pt-NPs	Catalytic degradation of H2O2	[^Citation154,^Citation159]
Au NPs	Glucose decomposition and H2O2 production	[^Citation158]
FeOCl and Mn^2+	Catalytic degradation of H2O2	[^Citation156]
Fe-Pt NPs	Fe-based Fenton reaction	[^Citation157]
MOF	MOF adsorption of O2	[^Citation160]
Cyanobacteria	Photosynthesis	[^Citation162]

Abbreviation: MOF, metal-organic framework.

Table 3 Summary of Light Penetration Strategies

Materials	Light Penetration Mechanism	Reference
N-doped GQDs/adjusting g-C3N4 size	Two-photon excitation	[^Citation84,^Citation123]
g-C3N5/Zn^2+ and K^+-doped g-C3N4	Decrease bandgap	[^Citation86,^Citation87]
g-C3N4/UCNPs	Conversion of NIR into ultraviolet and visible light	[^Citation164,^Citation165]
g-C3N4 QDs	Microwave induction	[^Citation85]
BP/Bi2O3	Cherenkov radiation of X-ray	[^Citation167]
MEH-PPV	Chemiluminescence	[^Citation171]
(p-Phenylene vinylene) derivative	Bioluminescence	[^Citation172]

Abbreviations: MEH-PPV, poly(2-methoxy-5-[(2-ethylhexyl)oxy]-p-phenylene vinylene); GQDs, graphene quantum dots; NIR, near-infrared; QDs, quantum dots.

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