Oozes and aahs: Slugs' gooey substance may provide alternative to surgery

Transcription

1 Oozes and aahs: Slugs' gooey substance may provide alternative to surgery By Washington Post, adapted by Newsela staff on Word Count 687 Level 1220L This species of bright orange slug inspired the adhesive. The slug oozes sticky goo off its back to defend itself from predators. Photo from Andy Smith via Washington Post Inspired by slug slime, scientists have invented a flexible glue that can be used in surgery. This stretchy adhesive can be attached to a beating, bleeding heart and could someday replace stitches. Other glues create strong but inflexible bonds or stretchy but weak connections. The sluginspired glue cements tightly, and it is held together by a stretchy web. The sticking power of this adhesive is "probably on the order of 10 times better than what's currently on the market," said Phillip Messersmith. He is a professor of bioengineering at the University of California at Berkeley and was not involved with the study. In addition to gluing things together, the adhesive could be used to deliver medications that are supposed to be released into the body over a long period of time. Most intriguingly, the flexibility of the adhesive means it could potentially be used in the hearts of growing children This article is available at 5 reading levels at 1

2 with cardiovascular disease, said Nikolay Vasilyev of Boston Children's Hospital in Massachusetts. Vasilyev is one of the authors of the study, which was published Thursday in the journal Science. It Even Sticks With Blood Present In experiments with pig organs, the material stuck strongly to skin, cartilage, arteries, livers and hearts, even when they were wet with blood. In one experiment, it was used to patch a hole in a pig heart. When the heart was inflated to simulate beating, the glue stretched along with the heart, and the hole stayed plugged even after more than 10,000 times. In living rats, the adhesive sealed a liver wound. It also produced less scar tissue than a surgical tool that is commonly used to close blood vessels during an operation. "This is really what we dreamed of," said Andy Smith, who studies slug slime for its adhesive properties at Ithaca College in New York state. The slug species that inspired this work oozes sticky goo off its back to defend itself from predators. "Anything that tried to eat this slug would get a mouthful of glue," Smith said. The bright orange slug is smaller than a pinkie, but it can churn out 5 percent of its body weight in slime. Within seconds, the sticky slime hardens into a rubber cement that will stretch between your fingers and is tough to remove. Strong Attraction Smith says positively charged protein chains and calcium ions may help explain how the slug slime sticks. The positive charges in the glue are attracted to the surface of biological tissues, many of which have negative charges, he said. After the initial electrostatic attraction, stronger interactions take over. These include electronsharing bonds like those between the hydrogen and oxygen atoms in a molecule of water and "physical entanglements" between the chains of molecules in the glue and the surface of the tissue. It works like a chemical hook-and-loop fastener. This binding is quick but not immediate, so the new glue will be much easier for doctors to work with than existing tissue adhesives, which stick almost instantly. The main ingredient in the adhesive is water, so it can be injected, potentially replacing invasive surgery in some cases. The glue is a hydrogel, a stretchy web of starchy chains of molecules that is 90 percent water. For people with heart disease, Vasilyev said the adhesive This article is available at 5 reading levels at 2

3 could mean more time between heart surgeries. Because the material is stretchy, it will move with a bending joint or expand with a growing heart. This means it can also stay in the body long term as a prosthetic or to attach devices like pacemakers, even in children. No More Stitches? Jianyu Li is a researcher at Harvard in Massachusetts and first author of the study. He hopes the team might be able to design adhesives that dissolve over time as a complete alternative to stitches. Xuanhe Zhao, who studies hydrogels at the Massachusetts Institute of Technology in Cambridge but was not involved with the study, called their approach "very innovative." These "tough hydrogels" have been tested in various devices, from robotics to condoms. Thanks to slugs, this is the first time hydrogels have been adapted to bind human tissue, Zhao said. This article is available at 5 reading levels at 3

4 Quiz 1 Which of the following sentences from the introduction [paragraphs 1-4] BEST develops a central idea of the article? Inspired by slug slime, scientists have invented a flexible glue that can be used in surgery. This stretchy adhesive can be attached to a beating, bleeding heart and could someday replace stitches. Other glues create strong but inflexible bonds or stretchy but weak connections. In addition to gluing things together, the adhesive could be used to deliver medications that are supposed to be released into the body over a long period of time. 2 Which answer choice provides an accurate and objective summary of the article? Hydrogels are being produced to used in place of glue in surgery because of their potential to adhere better and to stretch more than glue. Hydrogels are gels that are primarily made of water and create a strong chemical bond that can be very useful in applications with human tissue. Scientists have created a type of slime that will change the way surgeries are performed because of its special properties and water-based nature. Scientists have developed a hydrogel based on the slime of an orange slug that is more flexible and strong than any medical adhesives currently being used. This article is available at 5 reading levels at 4

5 3 Read the paragraph from the section "It Even Sticks With Blood Present." In experiments with pig organs, the material stuck strongly to skin, cartilage, arteries, livers and hearts, even when they were wet with blood. In one experiment, it was used to patch a hole in a pig heart. When the heart was inflated to simulate beating, the glue stretched along with the heart, and the hole stayed plugged even after more than 10,000 times. Adding which of these sentences to the paragraph would help to explain the meaning of the word "simulate" in the context of the article? The pumping heart was studied to test the glue. The heart was removed from the pig before the procedure. The heart was then hooked up to a machine that replicates heart rhythm. The procedure took place in a research laboratory where medical studies are performed. 4 What is the meaning of the phrase "potentially replacing invasive surgery" as used in the following sentence? The main ingredient in the adhesive is water, so it can be injected, potentially replacing invasive surgery in some cases. It will be placed into the body without having to cut the body open. It can be used as an additional method in place of therapeutic actions. It could be used without needing to perform procedures that enter the body. It might be used as a supplement for surgeries that are performed inside the body. This article is available at 5 reading levels at 5