Worms With A TiO₂ Diet Spin Superstrong Silk

Silk extruded by silkworms is a natural protein fiber prized for its strength and durability. But it’s not nature’s best biopolymer—spider silk is even stronger and able to stretch more before breaking, except it can’t easily be mass-produced. One way around this silky dilemma is to add titanium dioxide nanoparticles to the silkworm diet, reports a team led by Yaopeng Zhang of Donghua University, in China (ACS Sustainable Chem. Eng. 2015, DOI: 10.1021/acssuschemeng.5b00749). Zhang and colleagues were inspired by previous reports on feeding silkworms dye-containing food to yield colored cocoons. They also rationalized that feeding silkworms an additive would be easier than further processing the silk fiber. The team fed silkworms a diet containing up to 4% TiO₂ by weight. The silkworms excreted most of the TiO₂, but some was incorporated into the creatures’ cocoons. The silk from a 1% TiO₂ diet, containing 0.005% titanium by weight, outperformed unmodified silk on a strength test and was more resistant to degradation from UV radiation. Silk from a 2% diet performed similarly to unmodified silk, and silk from higher TiO₂ diets performed worse.