This hydrogel heals bleeding hearts

Closing wounds in soft elastic organs such as the lungs and heart is tricky. Today’s surgical glues don’t stick strongly to wet tissue, lack the necessary elasticity, and are unable to stanch bleeding. A new injectable hydrogel made of human tissue protein and silicate nanoparticles could help (Sci. Transl. Med. 2025, DOI: 10.1126/scitranslmed.adr6458).

The hydrogel stops bleeding and seals injuries within seconds and then helps regenerate tissue over time. “There is no existing product or hydrogel formulation that offers all these properties in a single biomaterial,” says Nasim Annabi, a chemical and biomolecular engineer at the University of California Los Angeles.

Annabi and colleagues have previously made a gel using human tropoelastin protein modified with methacryloyl groups, and tested it on lung tissue. Now the researchers modified the gel and its properties by adding Laponite clay nanoparticles.

Laponite crystals are composed of alternating silica and magnesium sheets. They have a negative surface charge and are known to promote blood clotting due to electrostatic interactions between their charged surfaces and blood cells.

The new liquid hydrogel precursor quickly cross-links when exposed to visible light, which is safer than using chemical crosslinkers or UV light, Annabi says. Cross-linking is driven by ionic interactions between the Laponite’s magnesium ions and the modified protein’s carboxyl groups, as well as by formation of hydrogen bonds and C-C bonds in the modified protein.

The hydrogel repaired bleeding wounds of various sizes in pig lungs and in rat lungs and arteries better than commercial glues. Annabi says the hydrogel is biodegradable, so it would not have to be removed after application. The team now plans to conduct longer-term in vivo testing.

Adding Laponite nanoparticles to the gel also seems to improve its mechanical properties, says Emilio Alarcon, a bionanomaterials chemist at the University of Ottawa Heart Institute. Alarcon would like to see more testing and data on the material’s efficacy and safety but says the use of nanoparticles approved by the US Food and Drug Administration is a good thing “because that will mean better clinical translation and use in humans when the time comes.”