Mussels and geckos just may be some of the stickiest creatures in nature, and scientists such as biomedical engineer Phillip Messersmith are harnessing their adhesive properties.
In a recent lecture, Messersmith outlined how he is stuck on these creatures for applications that could aid insurgery and the treatment of diseases.
He described the adhesive properties of mussels and geckos in the lecture, part of the Dean’s Grand Challenges Lecture Series in Medicine and Engineering at Northwestern University. Gecko foot pads adhere to surfaces temporarily, enabling them to move upside-down, while mussels attach permanently to surfaces by secreting a sort of protein glue that works underwater, Messersmith explained.
By understanding these daunting adhesive strategies, Messersmith is working to develop synthetic adhesives that can be used to repair tissue during surgery. The materials are in "pre-clinical stage testing,"
“The grand challenge is water,” Messersmith said. In most surgical situations, the tissue being repaired will be wet. By learning from the mussel, a medical adhesive can be made that is effective in these conditions.
Messersmith is a professor of biomedical engineering, materials science and engineering, and chemical and biological engineering at Northwestern.
He talks to the Medill News Service about tapping nature for adhesives:
Q. What does your research focus on?
A. My group does research in biomimetic materials. We are interested in exploiting strategies from nature to make new materials that have interesting and useful physical properties, and lend themselves to practical applications. Most of our interest is in developing materials that can be used to repair tissues or treat disease.
Q. Do you focus on just mussels and geckos for adhesives?
A. Mussels mostly, and the strategies that they use to attach to a surface. They live in the intertidal zone where there are a lot of forces from the movement of water. So, if they are not anchored securely they would be cast away or thrown against the rocks and their shells would crack. Their solution to this problem is to basically secrete protein glues that hold the organism down onto a surface. We are interested in understanding those proteins and how they work as adhesives.
Q. What would be some of the applications that you could derive from your understanding of mussel proteins?
A. Well, one of the things is a family of surgical adhesives or sealants that can be used to seal puncture wounds in tissues that are either created through traumatic injury or through a traumatic event. Also, [adhesives can be used] to bond tissues together, such as in a surgical procedure when you want to attach two surfaces together.
Q. What inspired you to do this research?
A. Just reading the academic literature. It was maybe 10 to 12 years ago that I began to become interested in this area of research—the mussel adhesive proteins. As a material scientist I became interested in using my skills to try and basically mimic the properties of this natural material that works well as an adhesive in the presence of water.
Let me take a step back and actually tell you what is not always obvious to the public, which is that adhesion in a wet environment is very difficult to achieve. The simple fact that a mussel can attach to a wet surface that’s submerged underwater during adhesion is actually quite remarkable. There are very few man-made adhesives that work well under those conditions. Considering our interest in developing materials that can work well to repair tissues, one has to recognize that in almost all surgical situations you have wet tissue surfaces as well. Learning from an organism in nature that has mastered the feat of wet adhesion makes, on some basic logical level, good sense. That’s sort of how we start from a natural material and work toward developing synthetic materials.
Q. Where do the geckos come in?
A. Consistent with my fascination with biological adhesion, geckos have almost the entirely different type of adhesive strategy in nature compared to mussels. Geckos have to accomplish very temporary adhesion for the purposes of locomotion. So, the adhesion is between the foot pad of the gecko and the surface it’s walking on. Geckos can climb up walls and across the ceiling; they have to adhere strongly enough to hold [their mass] but not so well they can’t get their foot off. It’s like a post-it. In one really interesting difference between gecko adhesion and mussel adhesion, geckos cannot adhere to surfaces that are wet. What we did in one of our synthetic adhesives that’s mimicking the mussel was combine ideas from gecko adhesion with ideas from mussel adhesion into a new material that kind of works like a post-it, but also works underwater. The gecko component of our research is relatively small part of the group and related somehow to the mussel in terms of combining the two strategies.
Q. What would be the practical applications of gecko-type adhesion?
A. Any type of temporary adhesive situation where you would want the adhesive to withstand environmental conditions in the presence of water are potential applications. Some are adhesion to skin or surgical bandages; maybe even consumer applications like band-aids. You’ve probably had the experience of band-aids not sticking well underwater or, if you sweat, they often come off. That would be a property we could perhaps improve upon with this strategy. Then there are also a lot of medical adhesion applications where you would want to adhere to a wet surface, but for a short period of time, like during a surgical procedure.