Cancer surgeons strive to remove cancerous cells while preserving as much healthy tissue as possible. Unfortunately, cancer cells are notoriously difficult to identify visually.

A group led by the National Cancer Institute’s Hisataka Kobayashi has developed a fluorescent spray that can label cancer cells within a minute. The hope is that surgeons could apply it during or after a procedure to catch any cancer cells they might have missed.

Several research teams have been working on fluorescent labels for cancer cells that could serve as a visual guide for surgeons, but other methods typically take much longer to work.

The researchers demonstrated the spray’s ability to label cancer cells in mice in a study published last week in Science Translational Medicine. The fluorescence is activated by an enzyme called y-glutamyl transpeptidase that is abundant in tumor cells but not in normal cells. The probe that Kobayashi and his team designed contains a chemical target of the tumor enzyme. The enzyme cleaves the chemical on contact, and this activates the fluorescence signal.