Tuesday, March 2, 2010

Bejeweling bugs to inspire bioadhesives?

ResearchBlogging.orgRemember those perhaps gross but cool insect jewelry artists I mentioned before? Now, their incredible tube-making skill might be used in an entirely different field: medicine.

Dr. Russell Stewart, an assistant professor at the University of Utah, has been studying natural adhesives for years. He was drawn to the caddisfly because it's one of the few creatures in this world to have accomplished a very difficult feat: it sticks things together underwater.

Creating an adhesive that works when wet isn't easy - just think of what happens to your average band-aid in the shower. But the caddisfly has mastered underwater engineering, and Stewart wanted to know exactly how it sticks together its living quarters.

Like many other organisms including spiders and silkworms, caddisfly larvae spin silk. It's their silken strands that stitch together their makeshift mobile homes. But scientists didn't understand how this worked while underwater - until now. A new study published online first in the journal Biomacromolecules reveals the caddisfly's architectural secrets.

The caddisfly larvae uses its silk like tape, researchers explain. They took larvae and placed them in aquaria with glass beads. Once the bugs had created their homes, the researchers analyzed their homes with a wide variety of technical tools, including scanning electron microscopy. The SEM images on the right show the criss-crossed strands of silk that have woven together the beads into the larvae's tube.

They learned that unlike the silk produced by terrestrial creatures, the caddisfly's silk works underwater because it's covered in phosphates (blue color in image F). Up to 95% of the serine residues in the silk protein are phosphorylated! We use phosphates in our own adhesives, including fillings and latex paints. In the caddisfly, these negatively-charged groups line up with positively charged proteins and cations like calcium, and the strong attraction between them holds the fiber together.

What's so special about this adhesive is that it can be used on just about anything, as artist Hubert Duprat found out when he placed caddisfly larvae in aquaria with gold flakes and precious gems. Their silk can bind all kinds of things, and this unique trait may make it an ideal candidate for medical use.

The hope is that since caddisfly silk works when wet, it could inspire a new kind of way to suture surgical wounds or even help repair small bone breaks. Characterizing the silk fibers is the first step towards copying the caddisfly's technology and creating a new line of medical glues or tapes that one day may replace sutures or stitches in sealing up wounds.

Stewart, R., & Wang, C. (2010). Adaptation of Caddisfly Larval Silks to Aquatic Habitats by Phosphorylation of H-Fibroin Serines Biomacromolecules DOI: 10.1021/bm901426d