This article is more than 5 years old. Information may no longer be current.
Plasma gun may 'fire' tPA to unclog retinal vein
Click Here to Manage Email Alerts
PALO ALTO, Calif. — Researchers at Stanford University here believe they may be able to treat retinal vein occlusions with a new instrument that uses a plasma to fire tiny "bullets" of blockage-dissolving drugs into a clogged vein.
Stanford researchers Daniel Palanker and Dan Fletcher have developed a needle-shaped probe they say could fire drugs right at the site of the occlusion and reopen the vein. The hollow needle is 1.5 mm in diameter and tapers to a point just 50 µm across. Inside the needle, a fine wire electrode surrounded by a metal sheath is bathed in electrically conductive saline solution containing a drug.
The researchers plan to mix tissue plasminogen activator (tPA) into the saline solution within the probe.
"If you can get the tip of the probe near the blocked vein, you could shoot the drug into the vein, where it will dissolve the blockage," Dr. Palanker said, adding that the hole made by the probe will heal quickly.
The probe has advantages over surgical needles, Dr. Palanker said. "These veins are very thin. If your hand is trembling slightly, you'll end up causing far more damage," he said. But the new probe will never touch the vulnerable vein, so mistakes would not be disastrous.
Dr. Palanker found that when he applied 1000 V between the electrode and the metal sheath, an ultra-hot plasma formed at the electrode tip, producing a rapidly expanding vapor bubble. By alternating the voltage, he could make the bubble expand and collapse within 1 µs.
"Each time the bubble expands, it ejects a pulse of saline," Dr. Palanker said.
"There's no new treatment for this at the moment, so any new ideas are good news," said John Forrester, an ophthalmologist at the University of Aberdeen, Scotland. "But like treating a heart attack, you'd have to get going quickly to save sight." The treatment would need to be done in a matter of hours after an occlusion, he said.
According to Rodney Grey, a surgeon at Bristol Eye Hospital in England, "The key question is: can they get enough drug into the vein to have a good effect?"
Dr. Palanker next plans to test how good the plasma-powered bullets are at cutting tissue during microsurgery. While lasers tend to damage surrounding tissues by creating bubbles in local body fluids, the pure saline jets might make finer cuts without stressing nearby tissue.
For more information, visit www.newscientist.com.