Limpet tooth inspires strongest biomaterial

An interdisciplinary team of biologists, chemists and engineers from the University of Portsmouth (U.K.; www.port.ac.uk) have become the first to successfully grow a limpet-inspired biomaterial with extreme strength. The common limpet (Patella vulgata) is a small, snail-like mollusk with a tongue covered with microscopic teeth that are used for scraping food from rocks. The teeth are a hard, flexible composite of chitin and goethite (α-FeO(OH)) that, in 2015, was found to be the strongest known biomaterial — much stronger than spider silk and comparable to man-made substances.

The team has now successfully mimicked limpet tooth formation in the laboratory and used it to create a new composite biomaterial, which is described in a study published last month in Nature Communications.

“Fully synthetic composites like Kevlar are widely used, but the manufacturing processes can be toxic, and the materials difficult and expensive to recycle,” says lead author Robin Rumney, from the University’s School of Pharmacy and Biomedical Sciences. “Here we have a material that potentially is much more sustainable in terms of how it’s sourced and made, and at the end of its life can be biodegraded.”

The key to the limpet tooth’s strength is thought to be due to a structure that combines flexible, tightly packed fibers of a scaffold material (chitin) interspersed with fine crystals of goethite. Those fibers are laced through each other in much the same way that carbon fibers are used to strengthen plastic.

The researchers developed methods that allowed cell populations to grow outside of their natural environment (ex vivo) on serum-coated glass, onto which they deposited chitin and iron oxide. After two weeks, the material self-organized into structures that resembled the limpet organ, known as the radula, which makes the teeth. Ribbons of teeth could also be grown from tissue samples and individual teeth from populations containing stem cells.

After successfully replicating the limpet tooth formation, the team was then able to produce samples of biomaterial 0.5-cm wide by mineralizing a sheet of chitin. Now that proof-of-concept has been established, the researchers will explore scaleup and manufacturing possibilities.