The Amazing Adventures of Spider Silk
Spidey’s secret identity is being revealed, and it has nothing to do with Peter Parker. (via imagesource)
Today Periodic Tabloid welcomes regular guest blogger Rebecca Guenard.
Spider silk has been studied for decades. If you have ever encountered it, you can understand why. The fibers of a web lengthen and adhere. Given their density, they are also incredibly strong, beating out steel or Kevlar. The chemical composition that leads to these mechanical properties has useful industrial applications; high-performance threads and technical fabrics are logical in reference to a fiber. But spider silk to aid human healing? Actually, it’s not a stretch. Spider silk is surprisingly biocompatible.
Like hair, cartilage or tendons, spider silk is a biopolymer made up of amino acid monomers that form proteins called spidrions. Spidroins occupy both a rigid, crystalline, and floppy amorphous structure along an extensive amino acid chain. It is this arrangement that gives the fiber its desirable mechanical traits.
But spider farms are expensive and produce low yields (since spiders have a tendency to eat each other). With these limitations, “natural spider silk will unlikely enter any commercial market in the near future,” says Dr. Thomas Scheibel, chair of the biomaterials department at the Universität Bayreuth in Germany.
Instead, scientists are looking to take silk out of the hands—well, legs—of spiders. Following trends in biotechnology, researchers induced host organisms like E. coli to produce spider silk proteins. From there the proteins can be tuned, chemically and physically, until they are optimized for a given application.
In the field of biomedical engineering applications abound. “Silk proteins show several advantages over other proteins,” says Dr. Scheibel. “They can be easily processed into three-dimensional structures including fibers, but also particles, hydrogels, films, capsules, non-woven meshes, etc.” Because silks can be manipulated in this way, they can be used to propagate human tissue, encapsulate slow-release drugs, or deliver lethal genes to tumor cells.
Recombinant and natural spider silk have been tested extensively in the lab, but in recent years a few research groups have boldly conducted experiments in vivo, the most remarkable being an artificial nerve graft. Dr. Peter Vogt and colleagues in the department of plastic, hand and reconstructive surgery at Hannover Medical School in Hannover, Germany severed the sciatic nerve of a rat and the tibial nerve of a sheep. They then replaced a portion of the nerve with spider silk-lined veins (no longer containing living cells). Within months nerve cells were regenerated and electrical pulses were reestablished along the spider silk. The sheep even regained a normal gait. Dr. Scheibel presumes that nerve growth may be a trait of other biopolymers and recommends that “other fibers should be tested in order to gain more insights into nerve growth.”
A nerve damaged sheep restored to health by an implanted spider web? Sounds like the plot for a comic book. Until then, pick up a June copy of Biopolymers—the entire issue is dedicated to silks.
Rebecca Guenard is formerly a chemistry professor and currently a science writer. She maintains the humorous science blog Atomic-o-licious, aimed at simultaneously entertaining and educating nonscientists.
Episode 14: Blockbuster Science [Distillations]
Nylon: A Revolution in Textiles [Chemical Heritage]
How Spider Silk’s Molecular Make-up Lets It Morph [80beats]