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Laser Show in the Surgical Suite

Lasers and a century-old dye could supplant needles and thread.
February 11, 2009

Despite medicine’s inestimable progress over the past century, surgery can still leave scars that look more appropriate to Frankenstein’s monster than to the beneficiary of a precise, modern operation. But in the Wellman Center for Photomedicine at Massachusetts General Hospital, Irene Kochevar and Robert Redmond have developed a method that has the potential to replace the surgeon’s needle and thread. Using surgical lasers and a light-activated dye, the researchers are prompting tissue to heal itself.

Laser healing: Researchers at Massachusetts General Hospital are developing a method to heal surgical incisions with laser light. Surgeons Ying Wang and Min Yao position a metal frame that directs a green surgical laser over the incision. The frame keeps the instrument steady and at a measured distance from the skin. They shine the light onto the cut to activate the dye, leaving it on for three minutes.

Laser-bonded healing is not a new idea. For years, scientists have been trying to find ways to use the heat generated by lasers to weld skin back together. But they’ve had a difficult time finding the right balance. Too little heat and a wound won’t heal; too much and the tissue dies. Eight years ago, one of Kochevar and Redmond’s colleagues was examining pathology slides of cells killed by this kind of thermal healing when it occurred to him that it might be possible to use just the light of a laser, rather than its heat.

While the idea of skin weaving itself back together may sound more like superhero lore than surgical skill, the science is startlingly simple. The team took advantage of the fact that a number of dyes are activated in the presence of light. In the case of Rose Bengal–a stain used in just about every ophthalmologist’s office to detect corneal lesions–the researchers believe that light helps transfer electrons between the dye molecule and collagen, the major structural component of tissue. This produces highly reactive free radicals that cause the molecular chains of collagen to chemically bond to each other, or “cross-link.” Paint two sides of a wound with Rose Benga­l, illuminate it with intense light, and the sides will knit themselves back together. “We call this nano suturing,” Kochevar says, “because what you’re doing is linking together the little collagen fibers. It’s way beyond anything that a thread of any kind can do.”

The benefits of such nano suturing are manifold. In just about every case, it appears to result in faster procedures, less scarring, and possibly fewer infections, since it seals openings completely and leaves no gap through which bacteria can penetrate. This makes it particularly well suited for closing not only superficial skin incisions but also those made in eye and nerve operations. In eye surgeries, such as corneal replacement, stitches that can cause irritation and infection must sometimes be left in place for months, which can aggravate complications. In nerve surgeries, damage from scar tissue can decrease the conduction of neural impulses. “If you put a needle through skin, it’s not a big deal,” says Redmon­d. “But if you put it through a nerve it’s a big deal, because you’re destroying part of the nerve.”

Light Work
The operations take place in a surgical suite of tile and stainless steel. Min Yao, a surgeon on Kochevar and Redmond’s team, has carted a medical laser up from the lab downstairs. The instrument is already used for eye, ear, nose, and throat procedures, and its green light has just the right wavelength for maximum absorption by the pink Rose Bengal stain. The better the light is absorbed, the more it activates the dye and the more complete the collagen cross-linking. The box that generates the laser light is barely larger than a stere­o receiver; a thin fiber-optic cable snakes out of its side, and it gives off an appletini-green glow.

For this particular test surgery, on the skin of an anesthetized rabbit, surgeon Ying Wang measures and marks a patch of skin to be removed, an elliptical, leaf-shaped patch 1.5 centimeters wide by 3.5 centi­meters long. After removing the tissue, Wang begins closing the wound. Surgical cuts typically require two layers of suturing: buried, or subcutaneous, stitches to bring deep tissu­e together, and superficial ones to close up the skin itself. Wang moves her needle and thread through the subcutaneous layer, working her way deftly from one end of the incision to the other. Then she moves on to the epidermal layer.

Wang closes up the right half of the cut with three stitches, black thread standing out against the rabbit’s pink skin. Then she takes a vial of Rose Bengal and drips the neon-pink dye onto either side of the unclosed portion of the wound. She threads the laser’s fiber-optic cable into a metal stand, which maintains a set distance between laser and tissue while holding the light steady; a lens focuses the beam into a sharp, straight line that can be aligned with the incision. Wang positions the stand on the rabbit’s flank, dons a pair of orange safety glasses, sets a timer, and steps down on the pedal that activates the laser. A green glow washes over the room.

Three minutes later, the timer beeps and Wang releases the pedal. She removes her safety glasses, moves the laser stand away, and inspects her handiwork. A small line is visible–a remnant of the Rose Benga­l stain and of the black marker used to trace the location of the incision prior to surgery. But when she tugs on the wound, using a pair of forceps in each hand to pull the skin apart, the skin holds taut, and there’s little visible evidence of the cut itself.

A Bright Future
“It’s a very interesting technology, which would be useful to anyone who does any kind of skin surgery–plastic surgeons, d­ermatologists,” says Robert Stern, a professor of dermatology at Harvard Medical School and chief of dermatology at Beth Israel Deaconess Medical Center in Bosto­n. He notes that the technology must still prove itself, and he isn’t yet convinced that the benefits will offset the costs of photochemical dyes and laser equipment, which are far pricier than a needle and thread. But, he says, the potential to minimize scarring and perhaps speed healing “could be nice for patients and improve outcomes [too].”

So far, use of the technique in humans has been limited to skin surgeries: in a clinical trial, 31 patients with skin cancers and suspicious moles had their three-to-five-centimeter excisions closed with sutures on one side and photo­chemical tissue bonding on the other. The dermatological procedure will be submitted to the U.S. Food and Drug Administration for approval, which the researchers are awaiting before beginning additional human trials. Animal experiments have already shown the technique to be useful in nerve, eye, and blood vessel surgeries, among others–so useful, in fact, that Kocheva­r and Redmond have surgeons ready and waiting to start human trials the moment the hospital approves them.

“Talk to just about any physician about this, and they have an idea for how it could be used,” Kochevar says. The technology is limited by tissue depth: it works only where light will penetrate, so it could never replace subcutaneous sutures or be effective on dark or opaque tissue like liver and bone. The scientists have licensed the technology to a brand-new startup, still in stealth mode, which plans to commercialize the tech­nology once it receives FDA approval. The company has just begun seeking its first round of funding.

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