Silk cocoons promise much for medical treatments

Microscopic cocoons have been created that can store sensitive proteins, making them useful for biotechnology or medicinal purposes. Invisible to the naked eye, these micron-scale capsules are comprised of silk nano-fibrils. To create these cocoons, scientists imitated the mechanisms by which the Chinese silkworm (Bombyx mori) spins silk.

Dr Chris Holland, head of the Natural Materials Group at the University of Cambridge and co-author of the paper, said: “Silk is amazing because whilst it is stored as a liquid, spinning transforms it into a solid. This is achieved by stretching the silk proteins as they flow down a microscopic tube inside the silkworm."

The capsules are comprised of a solid and tough shell of silk nano-fibrils that surround and protect a centre of liquid cargo and are more than a thousand times smaller than those created by silkworms. Dr Ulyana Shimanovich, a postdoctoral researcher at St John’s College at the University, said: “Silk is a fantastic example of a natural structural material. But we had to overcome the challenge of controlling the silk to the extent that we could mould it to our designs, which are much smaller than the natural silk cocoons."

The 'micrococoons' were able to store liquid silk for several months, with no noticeable effect on its functionality. As these cocoons can preserve antibodies that would otherwise degrade in walls that can be designed to dissolve over time, it could open the door to new treatments for cancer or neurodegenerative diseases. During the study, the researchers successfully tested these 'micrococoons' with an antibody that had been developed to act on alpha-synuclein, a protein whose malfunction is implicated in neurodegenerative diseases.

Silk also has the benefit of being biodegradable as well as less energy intensive and easier to produce than conventional synthetic capsules. The study was published in Nature Communications.