A biocompatible and highly elastic hydrogel sealant can effectively seal wounds in shape-shifting tissues without the need for common staples or sutures, a new study published in the journal Science Translational Medicine shows.

To repair ruptured or pierced organs and tissues, surgeons commonly use staples, sutures and wires to bring and hold the wound edges together so that they can heal.

However, these procedures can be difficult to perform in hard-to-reach areas of the body and wounds are often not completely sealed immediately. They also come with the risk that tissues are further damaged and infected.

The new study, led by Harvard University Professor Ali Khademhosseini and Northeastern University Assistant Professor Nasim Annabi, presents a robust solution for the efficient repair of wounds in mechanically challenging body areas — a surgical glue called MeTro.

“A good surgical sealant needs to have a combination of characteristics: it needs to be elastic, adhesive, non-toxic and biocompatible,” Dr. Annabi said.

“Most sealants on the market possess one or two of these characteristics, but not all of them. We set out to engineer a material that could have all of these properties.”

Professor Khademhosseini, Dr. Annabi and their colleagues from the United States and Australia demonstrated that MeTro can be photochemically tuned to effectively seal incisions in arteries and lungs of rats and to repair wounds in the lungs of pigs, all suture and staple-free.

“MeTro is shorthand for methacryloyl-substituted tropoelastin — a protein derived from the elastic fibers that make up human tissue,” the authors explained.

“MeTro’s high elasticity makes it ideal for sealing wounds in body tissues that continually expand and relax — such as lungs, hearts and arteries — that are otherwise at risk of re-opening.”

“The material also works on internal wounds that are often in hard-to-reach areas and have typically required staples or sutures due to surrounding body fluid hampering the effectiveness of other sealants.”

“MeTro sets in just 60 seconds once treated with UV light, and the technology has a built-in degrading enzyme which can be modified to determine how long the sealant lasts — from hours to months, in order to allow adequate time for the wound to heal.”

“MeTro seems to remain stable over the period that wounds need to heal in demanding mechanical conditions and later it degrades without any signs of toxicity,” Professor Khademhosseini said.

“It checks off all the boxes of a highly versatile and efficient surgical sealant with potential also beyond pulmonary and vascular suture and staple-less applications.”

“The beauty of the MeTro formulation is that, as soon as it comes in contact with tissue surfaces, it solidifies into a gel-like phase without running away,” Dr. Annabi added.

“We then further stabilize it by curing it on-site with a short light-mediated crosslinking treatment. This allows the sealant to be very accurately placed and to tightly bond and interlock with structures on the tissue surface.”

University of Sydney Professor Anthony Weiss described the process as resembling that of silicone sealants used around bathroom and kitchen tiles.

“When you watch MeTro, you can see it act like a liquid, filling the gaps and conforming to the shape of the wound,” he said.

“It responds well biologically, and interfaces closely with human tissue to promote healing. The gel is easily stored and can be squirted directly onto a wound or cavity.”

“The potential applications are powerful — from treating serious internal wounds at emergency sites such as following car accidents and in war zones, as well as improving hospital surgeries.”

“The next stage for the technology is clinical testing,” Professor Weiss said.

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Nasim Annabi et al. 2017. Engineering a highly elastic human protein-based sealant for surgical applications. Science Translational Medicine 9 (410): eaai7466; doi: 10.1126/scitranslmed.aai7466