Jul 29, 2017

Slug-inspired adhesive shows promise in treating wet wounds

The adhesive material adheres to biological tissue Photo: Wyss Institute at Harvard University

Inspired by slug secretion properties, scientists and engineers from Harvard have engineered a flexible, medical bandage made out of biomaterials that is able to adhere to wet or bloody wounds without serious side effects, according to a new study published in Science Thursday. The "tough adhesive" (TA) also is strong enough to transfer and dissipate stress, so it can be applied to beating hearts or to skin over joints.

Why this matters: Many current adhesive products are toxic to cells, inflexible when they dry, and do not bind strongly enough to biological tissue especially if the tissue is wet. Scientists have been researching tissue bioadhesives for years, due to the need to promptly control bleeding after trauma or during surgery to avoid severe blood loss in a manner that would also lessen the risk of infection or toxic reaction.

Other uses could be on the internal organs of children since it can stretch as they grow (such as kids with cardiovascular disease) or could be used to attach medical devices to their target structures, such as a pacemaker to support heart function.

Plus: The global market value of all medical adhesives was estimated to be about $5.8 billion in 2013 and is projected to reach $10 billion by 2019, according to MarketsandMarkets Research.

Nature's inspiration: Scientists often study nature's creative ways of dealing with crises to see if there are methods humans can use to adapt for their own use. In this case, the scientists were intrigued by a slug commonly found in Europe and parts of the U.S., called the Dusky Arion. When threatened, this slug produces a special kind of mucus that glues it in place so a predator cannot pry it off its wet or dry surface. "The polymer structure and mechanism of how defensive mucus works provide[d] a general design guideline in developing our material," study author Jianyu Li told Axios.

Yes, but: The TA is not made of slug mucus (as some other organizations may have erroneously stated). The main components of the material are 3 engineered biomaterials, Li said: chitosan derived from shrimp shells, alginate extracted from algae, and a synthetic polymer.

The team used these main ingredients to create a double-layered hydrogel containing positively charged polymers protruding from the surface, which allows it to form a strong bind to biological tissues. The current form is a patch similar to a bandaid but Li said "the design can lead to glue-like adhesive."

Test results: The team tested the material on dry and wet animal tissues, including skin, cartilage, heart, artery and liver. The material was successfully used to seal a hole in a pig heart that was mechanically inflated and deflated and subjected to tens of thousands of cycles of stretching. It stopped liver hemorrhage in mice without causing tissue damage or adhesions to surrounding tissues (common side effects from current adhesives like super glue and commercial thrombin-based adhesive).

"Our work represents a fundamentally new design of tissue adhesives that could achieve superior adhesion performance across various surfaces, even exposed with liquids," Li said. "The surprising finding is that the adhesion has been engineered as strong as one of the toughest soft tissues — articular cartilage."

Ingo Grunwald, a chemist in the Fraunhofer Institute for Manufacturing Technology and Advanced Materials who was not part of this study, told Axios: "Quite significant is the design of the polymer system and its estimated way of reaction. Although the single components are well known, the presented adhesion forces are very good and will open a broader field of application."

Limitations: This has not yet been tested on humans. Li said they have plans to test this form on humans, and research other forms such as a biodegradable form and an injectable adhesive with one-step injection.

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