The proteins used by silkworms and spiders to spin their fibres is a valuable natural material, although its use has been limited due to its tendency to clump together once extracted. In order to avoid this, researchers have been using chemically processed silk fibres, which are relatively inert compared with natural silk.

Researchers from the Weizmann Institute of Science, Israel, the Universities of Cambridge, Oxford and Sheffield in the UK and ETH Zurich in Switzerland collaborated to investigate what prevents natural silk clumping together within the bug before spinning.

Silk proteins are stored as a liquid in the silkworm’s glands before spinning. The researchers placed proteins extracted from silkworm glands inside tiny channels on a chip, and caused the protein molecules to self-assemble into a gel-like material, much like inside a real silkworm.

This gel formed microscopic capsules. Within these capsules, the rest of the protein stayed protected as a liquid, seemingly for an unlimited about of time. By controlling the viscosity of the solution and the forces acting on it, the researchers were able to control the capsules’ shapes and size.

“Making synthetic capsules is normally a complex and energy-intensive process. In contrast, silk capsules are easier to produce and require less energy to manufacture. Moreover, silk is biodegradable,” said Dr Ulyana Shimanovich, who now heads a lab at the Weizmann Institute’s Materials and Interfaces Department.

The team suggests that these tough silk capsules could be used to protect sensitive molecules – such as antibodies and other proteins – and prevent them from losing their valuable qualities while they are being delivered to target organs. In particular, Dr Shimanovich hopes that they could help develop future therapies for neurodegenerative diseases, given the ability of the capsules to penetrate the blood-brain barrier.

Given that the capsules are also biodegradable, they could also have applications in skin treatments or in the food industry, to incorporate oil particles into bread and other foods.