By Edwin L. Aguirre
In the “Spider-Man” movies, the superhero was able to stop a packed cable car and a runaway commuter train from crashing by using the incredibly tough spider web that he shot from his wrists. While such feats were created using Hollywood special effects, there is a measure of scientific truth to the extraordinary toughness of the spider web’s fiber, or silk.
“Spider silks are the toughest materials in nature,” says Jessica Garb, an associate professor in the Department of Biological Sciences. They are tougher than steel, yet weigh much less, and some spider silks can be stretched up to three times their length without breaking.
Garb is conducting research to examine the molecular composition, biomechanical properties and evolution of an exceptional type of silk produced by an arachnid species known as Darwin’s bark spider. “This particular species is endemic to the rainforests of Madagascar and constructs the largest orb webs ever recorded, capable of extending across rivers and lakes,” she says.
Her study, which is funded with a four-year, $335,000 National Science Foundation (NSF) grant, may lead to the development of a new generation of high-performance synthetic biomaterials for military, medical and consumer applications.
“Several startup companies are already producing spider-silk-based products using genetic engineering techniques, and our work will add to these endeavors by providing new recipes for even tougher silk-based materials,” says Garb. “For example, these materials could be used to improve helmets and body armor or other protective equipment, medical devices like prosthetics, bandages and sutures, as well as sports gear.”
One of the silks spun by Darwin’s bark spider, known as dragline silk, has been shown to be twice as tough as those produced by other known spider species and 10 times tougher than the Kevlar used in body armor, she notes.
The goal of the project is to examine the molecular makeup of this dragline silk and compare it to those from other closely related species to understand what makes Darwin’s dragline silk ultratough, how these unique properties have evolved and whether the extreme toughness of this silk is associated with the evolution of giant webs.
Nature’s Wonder Fiber
Dragline silk is one of seven silk types produced by orb-weaving spiders. It is used to construct the radial lines and frame lines of orb webs, and it is designed to absorb the kinetic energy of impacts from flying prey.
“Toughness is how much energy a material can absorb without breaking. Dragline silk is tough because it combines high tensile strength with elasticity,” says Garb.
Garb’s lab at UML will characterize the genes and proteins that make up dragline silk from Darwin’s bark spider and some of its closest relatives.
“We will use tools from microscopy, molecular biology, high-throughput DNA sequencing, protein biochemistry, evolutionary biology and bioinformatics to determine what the proteins are, how they are related to each other evolutionarily and how the features of silk proteins dictate the fibers’ mechanical properties. And by analyzing the genes that encode the proteins, we hope to understand how to replicate this material using genetic engineering for diverse textile applications,” she says.
Her research is being conducted in partnership with the University of Akron and the University of Vermont. “U. Akron and U. Vermont are sharing the NSF grant with UMass Lowell,” says Garb, who is the principal investigator for UML.
Assisting her in the lab are graduate student Molly Dawson and undergraduate Winny Rojas-Velez.
“Postdoctoral researcher Robert Haney is also involved in the research. Former master’s student Lindsay Schulman has also made important contributions to the project. Another undergraduate, Musah Suhununu, participated in the research last summer. Both Winny and Musah received support through the NSF’s Louis Stokes Alliances for Minority Participation program,” says Garb.