Locating hard-to-see nerves during surgery may now be possible with injectable fluorescent peptides that preferentially bind to peripheral neurons, causing them to glow. Nerve preservation, important in almost every kind of surgery, can be challenging, according to scientists at the University of California School of Medicine. If nerves are invaded by a tumor, or if the surgery is required in the setting of trauma or infection, affected nerves may not look normal, or their locations may be distorted. To overcome this obstacle, the researchers developed a systemic, fluorescently labeled peptide and injected it into mice. The peripheral nerve tissue labeled with the peptide forms a distinct contrast to adjacent, non-nerve tissues. Focused lighting They found that the highlighting occurs within two hours and can last for six to eight hours, with no observable effect upon the activity of the fluorescent nerves or behavior of the animal. The probe has not yet been tested in patients; however, it has been observed to label nerves in human tissue samples. Fluorescence labeling can occur even in nerves that have been damaged or severed, as long as they retain a blood supply, the group discovered. This could prove useful in future surgeries to repair injured nerves. Currently, avoiding damage to nerves depends on the skill of the surgeon and electromyographic monitoring, a technique that uses stimulating electrodes to identify motor neurons. The method’s limitation is that it does not identify sensory neurons, such as the neurovascular bundle around the prostate gland, for example. Injury to this nerve bundle during prostate surgery can lead to urinary incontinence or erectile dysfunction. The new study complements the group’s previous work in surgical molecular navigation. The scientists will continue to refine their probes in animal models in preparation for eventual human clinical trials. The findings were published online Feb. 6, 2011, in Nature Biotechnology (doi: 10.1038/nbt.1764).