Synthesis and evaluation of 5,15-diaryltetrabenzoporphyrins as photosensitizers for photo-diagnosis and photodynamic activity of tumors

Photodynamic therapy (PDT) is a well-established treatment modality, typically conducted with single-wavelength irradiation, which may not always be optimal for varying tumor locations and sizes. To address this, photosensitizers with absorption wavelengths ranging from 550 to 760 nm are being explored. Herein, a series of 5,15-diaryltetrabenzoporphyrins (Ar₂TBPs) were synthesized. All compounds displayed obvious absorption at 550–700 nm (especially at ∼668 nm), intense fluorescence, efficient generation of singlet oxygen and good photodynamic antitumor effects. Notably, compound I₃ (5,15-bis[(4-carboxymethoxy)phenyl]tetrabenzoporphyrin) showed excellent cytotoxicity against Eca-109 cell line upon red light irradiation, with an IC₅₀ value of 0.45 μM, and phototherapeutic index of 25.8. Flow cytometry revealed that I₃ could induce distinct cell apoptosis. In vivo studies revealed that compound I₃ selectively accumulated at tumor site and exhibited outstanding PDT effect with antitumor activity under single-time administration and light irradiation, and revealed more efficiency than the clinical photosensitizer Verteporfin. These findings underscore the considerable promise of I₃ as a robust theranostic agent, offering capabilities in real-time fluorescence imaging and serving as a potent photosensitizer for personalized and precise photodynamic therapy of tumors.