In Vivo Bioimaging and Photodynamic Therapy Based on Two-Photon Fluorescent Conjugated Polymers Containing Dibenzothiophene-S,S-dioxide Derivatives

Abstract

As a critical component for photodynamic therapy toward cancer treatment, photosensitizers require high photoinduced reactive oxygen species generation efficiency, good biocompatibility, and high phototoxicity. Herein, a series of donor−acceptor conjugated polymers containing dibenzothiophene-S,Sdioxide derivatives are designed and synthesized, which can be used as effective photosensitizers. The resulting copolymer PTA5 shows strong green light emission with high photoluminescence quantum yields owing to the intercrossed excited state of local existed and charge transfer states. The PTA5 nanoparticles can be fabricated by encapsulation with a biocompatible polymer matrix. Upon excitation at 800 nm, these nanoparticles present a relatively large two-photon absorption cross section of 3.29 × 10 6 GM. These nanoparticles also exhibit good photostability in water and thus can be utilized for bioimaging. The tissuepenetrating depths of up to 170 μm for hepatic vessels and 380 μm for blood vessels of mouse ear were achieved using PTA5 nanoparticles. Furthermore, PTA5 nanoparticles show impressive reactive oxygen species generation capability under the irradiation of a white light source. This can be attributed to the effective intersystem crossing between high-level excited state. Upon irradiation with white light (400−700 nm) at 50 mW cm −2 for 5 min every other day, the tumor growth can be effectively suppressed in the presence of PTA5 nanoparticles. These findings demonstrate that PTA5 nanoparticles can be used as a photosensitizer for photodynamic therapy.

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

“…Adding electron-deficient groups to the fluorene-phenylene structure can significantly improve ROS generation. 61 Guo et al 62 synthesized P21–23 containing dibenzothiophene-S and S-dioxide derivative acceptors and introduced SO units into conjugated main chains, which had a narrower bandgap, thus enhancing the electron transport capacity. 63 P22 has a relatively large two-photon absorption cross-section of 3.29×10 6 GM and good ROS generation capacity.…”

From main-chain conjugated polymer photosensitizer to hyperbranched polymer photosensitizer: expansion of the polymerization-enhanced photosensitization effect for photodynamic therapy

“…S1, ESI †). [27][28][29][30][31] Possibly because the polymerization-enhanced photosensitization effect was proposed based on the main-chain polymers, almost all of the conjugated polymer PSs reported so far have been mainchain polymers, whose skeletons are composed of alternating units of donors and accepters (Fig. 1 and Fig.…”

“…S1, ESI †). [27][28][29][30][31] As for the other types of conjugated polymer, there has been no work focused on them. What is more, nearly all of these reported conjugated polymer PSs are the Type-II PSs, meaning that they transfer energy to the nearby oxygen to generate singlet oxygen ( 1 O 2 ) upon excitation.…”

Fluorescent Polymers Conspectus

“…This is especially advantageous due to its superior visco-elastic and mechanical properties, which aid in the manufacturing of new devices [ 14 , 15 , 16 , 17 , 18 , 19 ]. FPs, similar to small fluorescent molecules, have a wide range of uses for sensing [ 20 , 21 ] and imaging [ 22 , 23 , 24 , 25 , 26 , 27 ], optoelectronics [ 28 ], fluorescent bioprobes [ 29 ], molecular imaging [ 30 ], photodynamic treatments [ 31 ], OLEDs [ 32 ], storage data security [ 33 ], encryption [ 34 ], anti-counterfeiting materials [ 35 ], and other fields [ 27 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 ].…”