Enhancing Precision in Photodynamic Therapy: Innovations in Light-Driven and Bioorthogonal Activation.

Over the past few decades, photodynamic therapy (PDT) has evolved as a minimally invasive treatment modality offering precise control over cancer and various other diseases. To address inherent challenges associated with PDT, researchers have been exploring two promising avenues: the development of intelligent photosensitizers activated through light-induced energy transfers, charges, or electron transfers, and the disruption of photosensitive bonds. Moreover, there is a growing emphasis on the bioorthogonal delivery or activation of photosensitizers within tumors, enabling targeted deployment and activation of these intelligent photosensitive systems in specific tissues, thus achieving highly precise PDT. This concise review highlights advancements made over the last decade in the realm of light-activated or bioorthogonal photosensitizers, comparing their efficacy and shaping future directions in the advancement of photodynamic therapy.

A first-in-class ß-glucuronidase responsive conjugate for selective dual targeted and photodynamic therapy of bladder cancer.

In this report, we present a novel prodrug strategy that can significantly improve the efficiency and selectivity of combined therapy for bladder cancer. Our approach involved the synthesis of a conjugate based on a chlorin-e6 photosensitizer and a derivative of the tyrosine kinase inhibitor cabozantinib, linked by a ß-glucuronidase-responsive linker. Upon activation by ß-glucuronidase, which is overproduced in various tumors and localized in lysosomes, this conjugate released both therapeutic modules within targeted cells. This activation was accompanied by the recovery of its fluorescence and the generation of reactive oxygen species. Investigation of photodynamic and dark toxicity in vitro revealed that the novel conjugate had an excellent safety profile and was able to inhibit tumor cells proliferation at submicromolar concentrations. Additionally, combined therapy effects were also observed in 3D models of tumor growth, demonstrating synergistic suppression through the activation of both photodynamic and targeted therapy.

One-Pot Lewis Acid Mediated Water-Promoted Transformation of Styrenes to α-Substituted Conjugated Enals.

We report herein an unusual one-pot preparation of α-benzyl-substituted conjugated enals via ZnCl2/LiCl/H2O-mediated transformation of styrenes. On the basis of experimental and computational studies, an underlying mechanism including electrophilic addition and hydride transfer with iminium cations has been proposed. The effect of the LiCl/ZnCl2/H2O combination on the reaction yield has been studied, demonstrating their participation in the activation and the key isomerization of an iminium electrophile.

Conjugates of Porphyrinoid-Based Photosensitizers with Cytotoxic Drugs: Current Progress and Future Directions toward Selective Photodynamic Therapy.

Photodynamic therapy (PDT) is a treatment modality where light-mediated activation of photosensitizers in a patient's body leads to the generation of cytotoxic reactive oxygen species (ROS), eliminating cancer cells. One direction that has been firmly established over past years is the conjugation of photosensitizers with various molecules that demonstrate their own cytotoxic activity. As a result, improved selectivity and treatment outcomes are observed compared to those of unconjugated drugs. The attractiveness of such an approach is due to the variability of cytotoxic warheads and specific linkers available for the construction of conjugates. In this review, we summarize and analyze data concerning these inventions with the ultimate goal to find a promising conjugation partner for a porphyrinoid-based photosensitizer. The current challenges toward successful conjugation are also outlined and discussed. We hope that this review will motivate researchers to pay closer attention to conjugates and possibilities hidden in these molecules for the PDT of cancer.

Water-Soluble Chlorin/Arylaminoquinazoline Conjugate for Photodynamic and Targeted Therapy.

A new water-soluble conjugate, consisting of a chlorin-e6 photosensitizer part, a 4-arylaminoquinazoline moiety with affinity to epidermal growth factor receptors, and a hydrophilic ß-d-maltose fragment, was synthesized starting from methylpheophorbide-a in seven steps. The prepared conjugate exhibited low levels of dark cytotoxicity and pronounced photoinduced cytotoxicity at submicromolar concentrations in vitro, with an IC50(dark)/IC50(light) ratio of ∼368 and a singlet oxygen quantum yield of about 20%. In tumor-bearing Balb/c nude mice, conjugate 1 preferentially accumulates in the tumor tissue. Irradiation of the nude mice bearing A431 xenograft tumors after intravenous administration of the prepared conjugate with a relatively low light dose (50 J/cm2) produced an excellent therapeutic effect with profound tumor regression and low systemic toxicity.

Synthesis and biological evaluation of new water-soluble photoactive chlorin conjugate for targeted delivery.

A new water-soluble conjugate, consisting of a chlorin-based photosensitizing part, and a 4-arylaminoquinazoline moiety with high potential affinity to an epidermal growth factor receptors (EGFR) and vascular endothelial growth factor receptors (VEGFR), suitable for photodynamic therapy (PDT), was synthesized starting from methylpheophorbide-a in seven steps. An increased accumulation of this compound in A431 cells with high level of EGFR expression, in comparison with CHO and HeLa cells with low EGFR expression was observed. The prepared conjugate exhibits dark and photoinduced cytotoxicity at micromolar concentrations with IC50dark/IC50light ratio of 11-18. In tumor-bearing mice, the conjugate preferentially accumulates in the tumor tissue.