Exploiting Metal-to-Metal Electron Transfer in a Ru(II) Polypyridine-Deferasirox Conjugate for Hypoxic Photodynamic...

Area of Science:

• Photochemistry
• Oncology
• Materials Science

Background:

• Solid tumors feature hypoxic microenvironments, driving cancer treatment resistance and poor outcomes.
• Photodynamic therapy (PDT) efficacy is limited by its reliance on molecular oxygen, reducing activity in hypoxic tumor regions.

Purpose of the Study:

• To develop an oxygen-independent photochemical system for cancer therapy.
• To investigate iron coordination as a switch for activating alternative photodynamic pathways.

Main Methods:

• A ruthenium(II) polypyridine complex was designed to coordinate with intracellular iron.
• Investigated photochemical mechanisms under normoxic and hypoxic conditions using spectroscopic and cellular assays.
• Assessed cytotoxicity and cell death pathways in cancer cell lines.

Main Results:

• The ruthenium complex produces singlet oxygen under normoxia but switches to metal-to-metal electron transfer upon iron binding.
• This iron-mediated pathway generates cytotoxic hydroxyl radicals from hydrogen peroxide, effective even in severe hypoxia.
• Demonstrated induction of lipid peroxidation, glutathione depletion, and ferroptosis in both sensitive and multidrug-resistant cancer cells.

Conclusions:

• Iron coordination acts as a molecular switch to enable oxygen-independent photochemistry.
• Metal-to-metal electron transfer provides a general strategy for designing hypoxia-tolerant photochemical systems.
• This approach offers a new paradigm for adaptive PDT in oncology, overcoming limitations of conventional oxygen-dependent therapies.