Researchers have synthesized a silk-protein-based hydrogel that can be used as a bio-ink for printing three-dimensional tissues such as cartilage, which can replace the damaged cartilage of osteoarthritis sufferers1.
Bioprinting is an emerging technique that employs bio-inks to print the exact three-dimensional shapes of human tissues. However, current bio-inks tend to be unstable and hence unable to replicate the exact three-dimensional shapes of specific tissues.
To produce a stable bio-ink that can print three-dimensional tissues and support their growth, the researchers synthesized a hydrogel by mixing gelatin with the silk protein fibroin. They then prepared two bio-inks ― one by adding an enzyme derived from mushrooms and the other by agitating the hydrogel with sound waves. They assessed the efficacies of the two bio-inks in printing mesenchymal stromal (stem) cells derived from human nasal inferior turbinate tissue and compared them with that of an alginate-based bio-ink.
Using a specially designed printer, the researchers deposited the bio-inks loaded with the human stem cells through a nozzle in a layer-by-layer manner. Of the three bio-inks, the enzyme-based one had the longest stability time of one month, during which time the bio-ink kept the human stem cells alive.
This long-term survival of the human stem cells in the enzyme-based bio-ink suggests that this bio-ink could be used for tissue regeneration. Human stem cells can differentiate into different types of cells. By analysing tissue-specific marker genes, the researchers found that the stem cells in the enzyme-based bio-ink retained their ability to grow into cartilage, bone or fat tissue.
“Currently, we are probing the efficiencies of the bio-ink to deposit monolayer of corneal cells and developing a cartilage-damaging disease model for screening potential drugs,” says Sourabh Ghosh, a senior author of the study.
