DNA in our cells faces continual harm from sunlight, chemicals, radiation and even the normal processes that keep the body functioning. Most of this damage is corrected very quickly. When these repairs fail, the resulting errors can play a role in aging, cancer and several other diseases.

For years, researchers struggled to directly observe these repair events as they occurred. Many traditional approaches required killing and preserving cells at different time points, producing only isolated snapshots instead of a continuous view.

A New DNA Damage Sensor for Living Cells

Scientists at Utrecht University have now introduced a sensor that changes this situation. Their tool allows researchers to watch damage appear and fade inside living cells and also inside living organisms. According to the study published in Nature Communications, this capability opens the way to experiments that were previously out of reach.

Lead researcher Tuncay Baubec describes the approach as a method for looking inside a cell "without disrupting the cell." He notes that common tools such as antibodies and nanobodies often bind too tightly to DNA, which can interfere with the cell's own repair systems.

"Our sensor is different," he says. "It's built from parts taken from a natural protein that the cell already uses. It goes on and off the damage site by itself, so what we see is the genuine behavior of the cell."

How the Fluorescent Sensor Works

The system relies on a fluorescent tag attached to a small domain taken from one of the cell's own proteins. This domain briefly recognizes a marker that appears only on damaged DNA. Because the interaction is gentle and reversible, the sensor highlights the affected region while leaving the cell's repair work untouched.

Biologist Richard Cardoso Da Silva, who helped design and evaluate the tool, recalls the moment he recognized its potential. "I was testing some drugs and saw the sensor lighting up exactly where commercial antibodies did," he says. "That was the moment I thought: this is going to work."

A Continuous View of DNA Repair

The contrast with older methods is striking. Instead of running many separate experiments to capture different moments, researchers can now watch the entire repair sequence as a single continuous movie. They can track when the damage appears, observe how rapidly repair proteins arrive and see when the cell resolves the issue. "You get more data, higher resolution and, importantly, a more realistic picture of what actually happens inside a living cell," says Cardoso Da Silva.

The research team also tested the sensor outside the lab dish. Collaborators at Utrecht University used the tool in the worm C. elegans, a widely used model organism. The sensor performed equally well and revealed programmed DNA breaks that occur during the worm's development. For Baubec, this demonstration was essential. "It showed that the tool is not only for cells in the lab. It can be used as well in real living organisms."

The potential applications extend beyond watching repair occur. The sensor's protein domain can be connected to other molecular components, allowing scientists to map the locations of DNA damage across the genome or determine which proteins gather around a damaged region. Researchers can also reposition damaged DNA inside the nucleus to test how its location influences repair. "Depending on your creativity and your question, you can use this tool in many ways," says Cardoso Da Silva.

Better Tools for Medical and Drug Research

Although the sensor is not a treatment, it could significantly improve medical research. Many cancer therapies work by inflicting deliberate DNA damage on tumor cells, and early drug development often requires precise measurements of how much damage a compound creates.

"Right now, clinical researchers often use antibodies to assess this," Baubec says. "Our tool could make these tests cheaper, faster and more accurate." The team also sees potential uses in clinical settings, such as studying natural aging or detecting exposure to radiation or other mutagenic factors.

The innovation is already attracting interest. Several laboratories contacted the team before publication, eager to use the sensor in their own repair studies. To support this demand, the researchers have made the tool available without restrictions. Baubec notes, "Everything is online. Scientists can use it immediately."