Utrecht scientists develop real-time DNA repair sensor for living cells

A team at Utrecht University has built something that changes how scientists watch cells heal themselves. They've created a fluorescent sensor that lets researchers observe DNA damage and repair happening in real time inside living cells—not as a series of frozen moments, but as a continuous process unfolding. The work, published in Nature Communications, opens doors to experiments that weren't possible before, with implications for cancer research, drug safety testing, and our understanding of aging.

DNA breaks constantly. Sunlight, chemicals, radiation, and the ordinary machinery of staying alive all leave their marks on the genetic code inside every cell. Most of the time, cells fix these breaks quickly and efficiently. When they don't, the consequences ripple outward: aging accelerates, cancer takes hold, disease spreads. But until now, scientists have struggled to actually watch this repair work as it happens. The standard approach required killing cells at different moments and examining them under a microscope—like trying to understand a movie by looking at individual frames pulled at random.

The Utrecht team, led by researcher Tuncay Baubec, approached the problem differently. They borrowed a tiny piece of a protein that cells already use naturally, attached a fluorescent tag to it, and engineered it to bind gently and reversibly to the markers that appear on damaged DNA. The key insight was gentleness. Existing tools like antibodies bind so tightly to DNA that they can actually interfere with the cell's own repair machinery, getting in the way of the very process scientists want to study. This new sensor lights up the damage without blocking the work.

Biologist Richard Cardoso Da Silva, who engineered and tested the tool, remembers the moment he knew it would work. He was testing some drugs and watched the sensor light up exactly where commercial antibodies did. That alignment—that confirmation that the sensor was seeing what it should see—told him they had something real. The difference in practice is striking. Instead of running ten separate experiments to capture ten snapshots of the repair process, scientists can now follow the entire sequence in one continuous observation. They see when damage appears, how quickly repair proteins arrive, and when the cell finally resolves the problem. The result is more data, finer detail, and crucially, a more honest picture of what actually happens inside a living cell.

The team didn't stop with cells in a dish. Collaborators tested the sensor in C. elegans, a roundworm widely used in biological research. It worked just as well there, revealing programmed DNA breaks that form during the worm's development. For Baubec, this was a turning point. The tool wasn't confined to the lab anymore. It could work in living organisms.

The sensor's potential extends beyond simple observation. Researchers can attach it to other molecular components to map where DNA damage occurs across the genome, identify which proteins gather at damage sites, or even move damaged DNA to different locations in the cell nucleus to test what factors affect repair speed and success. The tool is flexible, waiting for researchers to ask their own questions and find their own uses.

While the sensor itself isn't a medical treatment, it could reshape how medical research happens. Many cancer therapies work by deliberately damaging tumor cell DNA. In drug development, scientists need to measure precisely how much damage a compound causes. Right now, they often use antibodies for this assessment. Baubec suggests the new tool could make these tests cheaper, faster, and more accurate. The researchers also see applications in studying natural aging, detecting radiation exposure, and identifying mutagenic substances.

The team has made the sensor freely available to other laboratories. Even before publication, other researchers were reaching out, eager to use it in their own work. Everything is online. The barrier to entry is gone. What happens next depends on the questions other scientists ask and the experiments they design—but the tool is ready.