Sprayable Hydrogel Protects Heart from Post-Surgical Adhesions

Developed at the University of California, San Diego (UCSD; USA), the hydrogel barrier is comprised of aldehyde (ALD), aminooxy (AO), and oxime crosslinked poly(ethylene glycol) (PEG), functionalized with a catechol (CAT) group, that are mixed together to form the final gel (ALD-AO-CAT). The gel has favorable mechanical properties, degradation kinetics, minimal swelling, and superior tissue retention. The material is also cytocompatible, resists cell adhesion, and reduces the severity of adhesions. It can be easily removed from tissue and dissolves after four to six weeks.

The researchers also designed a device to safely and accurately spray the hydrogel inside the surgical field during open heart surgery. The spraying device houses the hydrogel's two main components in two different chambers; each is made of PEG with different reactive groups that crosslink together to form the hydrogel. One of the solutions also includes the catechol-modified PEG to ensure it stays on the heart. The two mix as they exit the device, forming the hydrogel. The researchers described the process as akin to using two cans of spray paint, for example blue and yellow, to create a third color, green. The study was published on June 18, 2021, in Nature Communications.

“We demonstrated here that the ALD–AO–CAT hydrogel possesses mechanical characteristics and degradation kinetics that are well-suited to the conditions within the chest cavity. The material also demonstrated a lower degree of swelling that surpasses the behavior of existing products,” said senior author Professor Karen Christman, PhD, and colleagues. “Our work is an engineering solution driven by a medical problem, and now it's poised to significantly improve cardiac surgery, both for adults and children.”

Depressed fibrinolytic activity resulting from surgical trauma to the epicardium during open-heart procedures can lead to fibrous adhesion formations between the epicardium and other tissues in the chest cavity. For children born with congenital heart defects, who will experience multiple surgeries over their lifetime, and adults receiving valve replacements, mechanical circulatory support, and/or coronary artery bypass grafting, this problem is particularly relevant, as these adhesions impede heart function and severely complicate resternotomy by obstructing visibility and increasing the risk of mortality and morbidity during dissection.

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