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Saturday, February 26, 2011

Fluorescent Peptides Make Nerves Glow During Surgery

 Image: NP41 highlighting buried nerve branches invisible by standard illumination (photo courtesy University of California, San Diego).

HospiMedica International staff writers

Injectable fluorescent peptides that cause hard-to-see peripheral nerves to glow could alert surgeons to their location, even before the nerves are encountered.

Researchers at the University of California, San Diego (UCSD; USA) developed and injected a systemic, fluorescently labeled peptide (NP41) to laboratory mice. The peptide preferentially binds to peripheral nerve tissue, creating a distinct contrast--up to tenfold--from adjacent non-nerve tissues. The effect occurs within two hours and lasts for six to eight hours, with no observable effect upon the activity of the fluorescent nerves or behavior of the animals. The researchers also found that the fluorescent peptide labels nerves in human tissue samples. The fluorescence highlighting is independent of axonal integrity, suggesting that the probe could facilitate surgical repair of injured nerves and help prevent accidental transection. The study was published on the February 6, 2011, in the advance online edition of Nature Biotechnology.

“The analogy I use is that when construction workers are excavating, they need a map showing where the existing underground electrical cables are actually buried, not just old plans of questionable accuracy,” said study coauthor Roger Tsien, PhD, a UCSD professor of pharmacology, chemistry, and biochemistry, and cowinner of the 2008 Nobel Prize in chemistry for his work on green fluorescent protein. “Likewise when surgeons are taking out tumors, they need a live map showing where the nerves are actually located, not just a static diagram of where they usually lie in the average patient.”

Currently, the ability to avoid accidental damage to nerves during surgery depends primarily upon the skill of the surgeon, and electromyographic (EMG) monitoring, a technique that employs stimulating electrodes to identify motor nerves. However, EMG cannot identify sensory nerves, such as the neurovascular bundle around the prostate gland, damage of which can lead to urinary incontinence and erectile dysfunction following prostate surgery.

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