from the charlotte-would-be-proud dept.
Scientists have created a kilometer of synthetic spider silk fiber using spider silk proteins made by genetically engineered bacteria:
Spiders make silk by secreting a protein solution through a narrow duct. As the solution goes through the duct, the pressure makes the proteins link together to make the silk fiber. For the study published today in the journal Nature Chemical Biology, researchers designed a machine that does the same thing using a combination of two natural spider proteins. The resulting material is the strongest artificial spider silk yet. It's almost as good as the real thing, it's biodegradable, and it's pretty cheap to make.
Also at Live Science:
[...] researchers combined spidroin genes from two spider species to create a hybrid spider silk gene called NT2RepCT. The NT2RepCT coded for a completely new protein that combined the best properties from the spidroins of the two species: high solubility and high sensitivity to pH. They then inserted the gene for the hybrid silk protein into the DNA of bacteria, which produced the proteins. In the end, this process produced a highly concentrated solution of spider silk proteins that looked cloudy and viscous, just as real spider silk proteins do inside the silk glands. They then pumped this solution through a thin glass capillary, which mimicked the shearing that produced spider silk fiber in the real world, the researchers wrote in the paper. This process produced 3,280 feet (1,000 meters) of fiber in a 0.26 gallon (1 liter) flask, the researchers reported.
"The as-spun NT2RepCT fibers had a qualitatively similar stress-strain behavior to native spider silk in that they displayed an initial elastic phase up until a yielding point," after which the silk began to deform, the researchers wrote in the paper. Also, while the synthetic spider silk acted much like the real thing, it had lower toughness and tensile strength than its natural counterpart, meaning it breaks more easily.
Biomimetic spinning of artificial spider silk from a chimeric minispidroin (DOI: 10.1038/nchembio.2269) (DX)
Spider silk can be made stronger by feeding the spiders that produce the silk aqueous dispersions containing graphene or carbon nanotubes:
[Researchers] in Italy and the UK have found a way to make [spider] silk a lot stronger, using various different spider species and carbon nanotubes or graphene. The research team, led by Professor Nicola Pugno at the University of Trento, Italy, succeeded in having their spiders produce silk with up to three times the strength and ten times the toughness of the regular material.
[...] "We already know that there are biominerals present in in the protein matrices and hard tissues of insects, which gives them high strength and hardness in their jaws, mandibles and teeth, for example. So our study looked at whether spider silk's properties could be 'enhanced' by artificially incorporating various different nanomaterials into the silk's biological protein structures."
To do this, the team exposed three different spider species to water dispersions containing carbon nanotubes or graphene. After collecting the spiders' silk, the team tested its tensile strength and toughness. Professor Pugno said: "We found that the strongest silk the spiders spun had a fracture strength up to 5.4 gigapascals (GPa), and a toughness modulus up to 1,570 joules per gram (J/g). Normal spider silk, by comparison, has a fracture strength of around 1.5 GPa and a toughness modulus of around 150 J/g.
Spider silk reinforced by graphene or carbon nanotubes (DOI: 10.1088/2053-1583/aa7cd3) (DX)