Many research groups are testing “ink” made from silk proteins to print human tissues, implants and perhaps even organs. The process is a less costly alternative to conventional 3-D printing with collagen, a key protein in the body’s natural scaffolding. Researchers in Assam, a state in India, are investigating using local silkworm species for the task—they recently submitted a patent for bioinks using a combination of proteins extracted from local species Antheraea assamensis and Samia ricini, as well as the commonly used Bombyx mori. The scientists have woven them into synthetic structures ranging from blood vessels to liver lobes; in a paper published in September in ACS Applied Materials & Interfaces, they described mimicking the cartilage of an entire ear.
Silk is a natural polymer, a substance with long, repeating molecular chains. It is mechanically strong and completely biodegradable, well suited for applications in tissue engineering. To use it, researchers draw liquid silk from the silkworm’s glands or dissolve silk fibers in solvents. They carefully mix the gelatinous liquid with a patient’s stem cells, then build structures layer by layer with a 3-D printer. After implantation, the cells grow and replace the silken scaffold, which eventually degenerates into amino acids.