1.Introduction to Photodynamic Therapy (PDT)

Photodynamic Therapy (PDT) is a cancer treatment method that combines photosensitizing drugs with laser activation. It offers advantages such as minimal invasiveness, precise spatiotemporal control, low side effects, and a reduced likelihood of drug resistance. Traditional PDT relies on photoexciting a photosensitizer (PS) to transfer energy to oxygen, generating highly toxic reactive oxygen species (ROS) to induce tumor cell death. However, limitations such as poor water solubility and high oxygen dependency hinder its therapeutic efficacy.

2. Design and Properties of a Novel Iridium-Based Photocatalyst

Associate Professor Huang Huaiyi from Sun Yat-sen University designed and synthesized a water-soluble coumarin-functionalized Ir³⁺ photocatalyst. Experimental results show that Ir2 and Ir3, both modified with a coumarin-6 ligand, exhibit significantly higher absorbance in the visible light region compared to Ir1. Among them, Ir3, with its positively charged ligand, demonstrates superior water solubility relative to Ir1 and Ir2.

3. Optical Characterization of Ir³⁺ Complexes

The UV/Vis absorption spectra (in PBS) and emission spectra (in CH₂Cl₂) of three Ir³⁺ complexes were measured at room temperature, with an excitation wavelength of 465 nm. The inset illustrates their distribution behavior in water and n-octanol.

4. Mechanisms of ROS Generation: Type II vs. Type I Pathways

It is well known that photoactive Ir³⁺ complexes can generate highly cytotoxic singlet oxygen (¹O₂) through a Type II mechanism upon photoexcitation. Compared to Ir1 (77.0%) and Ir2 (90.4%), Ir3 (14.2%) exhibits significantly lower efficiency in ¹O₂ production. However, besides the Type II pathway, Type I photosensitization has attracted considerable attention due to its potent therapeutic effects under hypoxic conditions.

5. Photocatalytic Activity in Oxidizing Biomolecules

NADPH and NADH play critical roles in maintaining intracellular redox homeostasis, and alterations in their concentrations can lead to cell death. Oxidation of amino acids can disrupt cellular protein synthesis and function. Associate Professor Huang Huaiyi further investigated the photocatalytic activity of Ir3 in oxidizing NADH, NADPH, and several amino acids in PBS. The results demonstrate that Ir3 is an efficient photocatalyst for oxidizing these biomolecules via a single-electron transfer (SET) mechanism. During irradiation, the detection of H₂O₂ indicates the generation of superoxide anion radicals (O₂⁻).

6. Photocytotoxicity Against Normal and Drug-Resistant Cancer Cells

Associate Professor Huang Huaiyi examined the photocytotoxic activities of these three complexes against normal cells and cancer cells, including drug-resistant variants. The findings reveal that Ir3 exhibits low toxicity toward normal cells in the dark (IC₅₀ > 100 μM) while demonstrating potent photocytotoxicity against cisplatin- and sorafenib-resistant cell lines, with IC₅₀ values of approximately 0.37 μM and 20 μM, respectively.

7. In Vivo Anticancer Efficacy and Biocompatibility

In vivo tumor models in zebrafish and mice confirmed the high biocompatibility and photocatalytic anticancer efficacy of Ir3 .

Huang Huaiyi is a professor and doctoral supervisor at Sun Yat-sen Universit
His primary research focuses on the molecular mechanisms of tumor energy and substance metabolism reprogramming, and he has pioneered a tumor photocatalytic therapy strategy.
He has made substantial achievements in this field, having published over 60 papers as the first or corresponding author in prestigious international and domestic journals such as Nature Chemistry, Angewandte Chemie International Edition, Science China Chemistry, Coordination Chemistry Reviews, and Biomaterials. He has also been granted 11 Chinese invention patents related to metal-based drugs.

Product Advantages：

1.It exhibits excellent photocatalytic performance and can be applied in research fields such as tumor photocatalytic therapy, photocatalytic organic synthesis, photocatalytic hydrogen production, and cellular imaging.
2.With unique excited-state redox potentials, it can serve as an excited-state oxidant or reductant in photocatalytic reactions.
3.It offers high photostability, easy storage, safe operation, broad applicability, and high reaction efficiency.

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