Scientists use light to expand implants, reducing child heart surgeries

“After the surgeon first puts in the tube, these children often have to go through an additional two or three, maybe even four, surgeries just to implant a slightly larger tube,” says Christopher Rodell, assistant professor of biomedical engineering at Drexel University. 

“Our goal is to expand the inside of the tube with a light-emitting catheter that we insert inside the shunt, completely eliminating the need for additional surgeries.”

Light-activated hydrogels

These congenital heart defects affect the heart’s lower chambers, known as ventricles, leading to restricted blood flow to the lungs and the rest of the body. Without surgical intervention, infants with these conditions cannot survive. Many of these babies are born small, but they can experience rapid growth after their first shunt implantation.

To accommodate this growth, surgeons often have to perform another open-chest surgery to replace the shunt with a larger one. Each surgery carries significant risks. In a study involving 360 patients who underwent the initial heart reconstruction, 41 required additional surgeries for a larger shunt, and sadly, seven patients did not survive.

Rodell collaborated with his Drexel colleagues, Amy Throckmorton and Kara Spiller, who had previously designed an expandable prototype to potentially replace the most commonly used shunt. Rodell’s role was to redesign the shunt materials to ensure they were safe for clinical use and adaptable to the needs of individual children.

He achieved this by creating new polymers for a hydrogel that could form additional crosslinks and expand the shunt’s inner diameter when triggered. To control this expansion, Rodell chose blue light as the activation method, as it has enough energy to start the reaction while remaining safe for living tissues.

40% dilation

“Light has always been one of my favorite triggers, because you can control when and where you apply it,” Rodell says in the press release.

For their new device, Rodell and his team, led by graduate student Akari Seiner, are utilizing a fiber-optic catheter—a long, slender tube with a light-emitting tip. To activate the light-sensitive hydrogel within the shunt, their goal is for surgeons to insert the catheter into an artery near the armpit and guide it into place, avoiding the need for open-chest surgery.

In laboratory tests, they discovered that the shunt could be expanded gradually, with the degree of expansion controlled by the duration of light exposure. These findings suggest that once the shunt is implanted, it can be adjusted to suit the needs of each child.

The team was able to dilate the shunt by up to 40%, increasing its diameter from 3.5 millimeters to 5 millimeters—comparable to the size of the largest shunts used in children.

Additionally, they evaluated how blood cells and vessels reacted to the modified shunt and found no signs of clot formation, inflammation, or other potential health risks associated with the implanted device.

Further research

The next step for the team involves testing full-length shunt prototypes in a simulated setup that replicates the human circulatory system. If these tests prove successful, the researchers plan to advance to experiments using animal models.

According to Rodell, this technology could have broader applications beyond treating single-ventricle heart defects. For instance, similar devices could potentially be used to replace blood vessels in children who have sustained injuries in car accidents.

“In these procedures, you run into the same problem: Children aren’t just tiny adults; they continue to grow,” Rodell concludes. “That’s something we need to account for in biomaterials, how that graft will behave over time.”

This research will be presented at the fall meeting of the American Chemical Society (ACS).