Inspired by a sticky substance that spiders use to catch their prey, a double-sided tape was developed that can rapidly seal tissues together. The new tape can tightly bind tissues such as the lungs and intestines within five seconds. The tape could eventually be used in place of surgical sutures, which don’t work well in all tissues and can cause complications in some patients. The double-sided tape can also be used to attach implantable medical devices to tissues including the heart. In addition, it works much faster than tissue glues, which usually take several minutes to bind tightly and can drip onto other parts of the body.
Forming a tight seal between tissues is considered to be very difficult because water on the surface of the tissues interferes with adhesion. Existing tissue glues diffuse adhesive molecules through the water between two tissue surfaces to bind them together but this process can take several minutes or even longer. To create a double-sided tape that could rapidly join two wet surfaces together, researchers drew inspiration from the natural world — specifically, the sticky material that spiders use to capture their prey in wet conditions. This spider glue includes charged polysaccharides that can absorb water from the surface of an insect almost instantaneously, clearing off a small, dry patch to which the glue can adhere.
To mimic this with an engineered adhesive, the researchers designed a material that first absorbs water from wet tissues and then rapidly binds two tissues together. For water absorption, they used polyacrylic acid, a very absorbent material used in diapers. As soon as the tape is applied, it sucks up water, allowing the polyacrylic acid to quickly form weak hydrogen bonds with both tissues. These hydrogen bonds and other weak interactions temporarily hold the tape and tissues in place while chemical groups called NHS esters — which are embedded in the polyacrylic acid — form much stronger bonds, called covalent bonds, with proteins in the tissue. This takes about five seconds.
To make the tape tough enough to last inside the body, the researchers incorporated either gelatin or chitosan (a hard polysaccharide found in insect shells). These polymers allow the adhesive to hold its shape for long periods of time. Depending on the application, the researchers can control how fast it breaks down inside the body by varying the ingredients that go into it. Gelatin tends to break down within a few days or weeks in the human body, while chitosan can last longer (a month or even up to a year).
This type of adhesive could have an impact on surgeons’ ability to seal incisions and heal wounds. The tape could also successfully attach materials such as silicone rubber, titanium, and hydro-gels to tissues.