An Electron Donor-Acceptor Structured Rhenium(I) Complex Photo-Sensitizer Evokes Mutually Reinforcing "Closed-Loop" Ferroptosis and Immunotherapy.

The hypoxic microenvironment of solid tumors severely lowers the efficacy of oxygen-dependent photodynamic therapy (PDT). The development of hypoxia-tolerant photosensitizers for PDT is an urgent requirement. In this study, a novel rhenium complex (Re-TTPY) to develop a "closed-loop" therapy based on PDT-induced ferroptosis and immune therapy is reported. Due to its electron donor-acceptor (D-A) structure, Re-TTPY undergoes energy transfer and electron transfer processes under 550 nm light irradiation and displays hypoxia-tolerant type I/II combined PDT capability, which can generate 1O2, O2 -, and ·OH simultaneously. Further, the reactive oxygen species (ROSs) leads to the depletion of 1,4-dihydronicotinamide adenine dinucleotide (NADH), glutathione peroxidase 4 (GPX4), and glutathione (GSH). As a result, ferroptosis occurs in cells, simultaneously triggers immunogenic cell death (ICD), and promotes the maturation of dendritic cells (DCs) and infiltration of T cells. The release of interferon-γ (IFN-γ) by CD8+ T cells downregulates the expression of GPX4, further enhancing the occurrence of ferroptosis, and thereby, forming a mutually reinforcing "closed-loop" therapeutic approach.

A 700 nm LED Light Activated Ru(II) Complex Destroys Tumor Cytoskeleton via Photosensitization and Photocatalysis.

Photoactivable chemotherapy (PACT) using metallic complexes provides spatiotemporal selectivity over drug activation for targeted anticancer therapy. However, the poor absorption in near-infrared (NIR) light region of most metallic complexes renders tissue penetration challenging. Herein, an NIR light triggered dinuclear photoactivable Ru(II) complex (Ru2) is presented and the antitumor mechanism is comprehensively investigated. The introduction of a donor-acceptor-donor (D-A-D) linker greatly enhances the intramolecular charge transition, resulting in a high molar extinction coefficient in the NIR region with an extended triplet excited state lifetime. Most importantly, when activated by 700 nm NIR light, Ru2 exhibits unique slow photodissociation kinetics that facilitates synergistic photosensitization and photocatalytic activity to destroy diverse intracellular biomolecules. In vitro and in vivo experiments show that when activated by 700 nm NIR light, Ru2 exhibits nanomolar photocytotoxicity toward 4T1 cancer cells via the induction of calcium overload and endoplasmic reticulum (ER) stress. These findings provide a robust foundation for the development of NIR-activated Ru(II) PACT complexes for phototherapeutic application.

Novel Ru(II) complexes with multiple anticancer photoreactivity: ligand exchange, photoredox catalysis, reactive oxygen generation and endoperoxide formation.

The hypoxic microenvironment and drug resistance of cancer cells have become a huge threat for clinical anticancer therapy. Anticancer phototherapy providing spatial and temporal control over drug activation may conquer this problem. Herein, we report a novel photoactivated Ru(II) complex (Ru2) with multiple activities including photochemotherapy, photodynamic and photocatalytic therapy, and endoperoxide formation. Upon white light irradiation, Ru2 can dissociate the coordinating ligands and form endoperoxides, produce diverse reactive oxygen species and catalytically oxidize cellular coenzymes. As a result, Ru2 shows promising antiproliferation activity toward cisplatin and 5-fluorouracil resistant tumor cell lines under normoxia and hypoxia. The multifunctional design strategy of metal-based anticancer drugs offers novel efficient therapeutics to combat drug-resistant cancer cells under hypoxia.

Axisymmetric bis-tridentate Ir(III) photoredox catalysts for anticancer phototherapy under hypoxia.

A novel axisymmetric bis-tridentate Ir(III) photocatalyst (Ir3) with synergetic type I/II photosensitization and photocatalytic activity was reported. Ir3 exhibited high photocytotoxicity toward drug-resistant cancer cells under normoxia and hypoxia. The photoactivated anticancer mechanism of Ir3 were investigated in detail. Overall, this new photo-redox catalyst can overcome hypoxia and drug resistance-related problems in clinical anticancer therapy.

Combination of Immunotherapy and Photo-pyroptosis as Novel Anticancer Strategy.

Immunotherapy has made great progress in clinical cancer treatment in recent years, but its therapeutic efficacy is significantly limited by the lack of immunogenicity in the tumor microenvironment. Pyroptosis is a type of programmed cell death in which the dying cancer cells produce inflammatory cytokines to relieve the immuno-suppressive microenvironment and thus increase anti-tumor immunity. Reactive oxygen species (ROS) produced during photodynamic therapy (PDT) are one of the efficient activators that induce pyroptosis. Recently, a few photosensitizers have emerged with the ability to induce immunogenic cancer cell death via pyroptosis, opening a new field for PDT. This highlight introduces the latest research on antitumor strategies achieved by the combination of immunotherapy and photodynamic therapy through photo-pyroptosis.

Engineered Exosomes as a Photosensitizer Delivery Platform for Cancer Photodynamic Therapy.

Photodynamic therapy (PDT), a non-/minimally invasive cancer treatment method, has the advantages of low side effects, high selectivity, and low drug resistance. It is currently a popular cancer treatment method. However, given the shortcomings of photosensitizers such as poor photostability, poor water solubility, and short half-life in vivo when used alone, the development of photosensitizer nano-delivery platforms has always been a research hotspot to overcome these shortcomings. In the human body, various types of cells generally release bilayer extracellular vesicles known as exosomes. Compared with traditional materials, exosomes are currently an ideal drug delivery platform due to their homology, low immunogenicity, easy modification, high biocompatibility, and natural carrying capacity. Therefore, in this concept, we focus on the research status and prospects of engineered exosome-based photosensitizer nano-delivery platforms in cancer PDT.