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-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.”
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.