Synthesis of Porphyrin Semitelechelic Polymers and Application in Photodynamic Therapy

Porphyrin and its derivatives, which are widely existed in organisms and participate in essential physiological processes, are well-known and promising photosensitizers. However, many drawbacks, such as strong hydrophobicity and self-quenching induced by aggregation, have greatly limited their applications in photodynamic therapy (PDT). Herein, a series of water-soluble porphyrin semitelechelic polymers (TPP-PEG) were successfully synthesized via click reaction between hydrophilic polyethylene glycol chains with various molecular weight (PEG, M_n=1 000, 2 000, 5 000) and tetraphenyl porphyrin unit (TPP). Compared with small porphyrin molecules, these PEGlated porphyrin semitelechelic polymers exhibit excellent solubility in aqueous solution, greatly reducing the intermolecular π-π stacking and thereby enhancing the singlet oxygen generation. In addition, the introduction of PEG chains also improves the biocompatibility of the porphyrin photosensitizer. Using 1,3-diphenylisobenzofuran (DPBF) as the ¹O₂ detecting probe, the UV-vis absorption intensity results show that the ¹O₂ generation of TPP-PEG are faster and more extensive than the free TPP molecules. Additionally, the results indicate that the ¹O₂ generation capability of TPP-PEG decreases with the increase of the lergth of PEG chain. The Thiazolyl Blue Tetrazolium Bromide method (MTT) assay results of dark cytotoxicity and phototoxicity in HeLa cells also confirmed that TPP-PEG possesses good biocompatibility and high cytotoxicity under light irradiation.