Ruhr University Researchers Develop Ruthenium Agent to Kill Cancer in Oxygen-Depleted Tumors

Ruhr University researchers develop a ruthenium-based agent that uses intracellular iron to kill cancer in oxygen-starved tumors via photodynamic therapy.

By: AXL Media

Published: Apr 7, 2026, 9:01 AM EDT

Source: Information for this report was sourced from Ruhr-Universitaet-Bochum

Overcoming the Limits of Photodynamic Therapy

Photodynamic therapy (PDT) has long been a staple in clinical cancer treatment, relying on light-activated substances to generate reactive oxygen species that kill malignant cells. However, the rapid growth of many aggressive tumors often outpaces vascular development, creating "hypoxic" zones devoid of oxygen where conventional PDT becomes ineffective. Professor Johannes Karges and his team at Ruhr University Bochum have addressed this critical limitation by developing a ruthenium-based active agent capable of switching its mechanism of action based on the surrounding environment. Their findings, published in the Journal of the American Chemical Society, offer a potential solution for treating fast-growing, deep-seated tumors.

A Dual-Action Electronic Mechanism

The innovation lies in the agent's ability to transition between two distinct chemical processes. In oxygen-rich tissue, the ruthenium-based substance behaves traditionally: targeted light irradiation elevates the agent to an excited electronic state, transferring energy to molecular oxygen to create singlet oxygen, which is toxic to cells. However, when oxygen is absent, the agent utilizes a newly discovered pathway. According to Professor Karges, the coordination of intracellular iron to the active agent alters the system's electronic characteristics, enabling an ultra-fast electron transfer that functions independently of oxygen levels.

Harnessing Cellular Metabolic Waste

This alternative mechanism leverages hydrogen peroxide, a natural metabolic byproduct found within cells. When the excited ruthenium center transfers electrons to the coordinated iron center, it converts the hydrogen peroxide into highly reactive hydroxyl radicals. These radicals cause severe oxidative damage to central cellular structures, effectively killing the cancer cells from within. Because this process relies on internal metabolic products rather than external oxygen delivery, the treatment remains active under the severe conditions of oxygen deprivation that typically cause other therapies to fail.