A promising new inkjet bioprinting technique has been developed by researchers in Japan that solves many of the challenges of printing bioinks into solid structures.
One of the main problems with developing bioinks is to create an ink out of living cells which is sufficiently fluid to allow it to pass through the nozzle of the printer, yet sticky and thick enough to allow 3D shapes to be printed that retain their shape. For the technique to be of use, the cells used in the ink must also be capable of surviving the printing process.
Significant advances have been made in this area, although most of the bioinks developed so far use sodium alginate. Sodium alginate has a sufficiently low viscosity to allow it to pass through the nozzle of the printer but forms a gel-like structure when printed, allowing it to be used to create a 3D shape. Unfortunately, sodium alginate is it is not suitable for use with all cell types. Since organs are made up of many different types of cells, a bioink must be developed capable of supporting a wide range of cell types.
Researchers at Osaka University in Japan have identified an alternative inkjet bioprinting method. Instead of using sodium alginate, the researchers use a method of hydrogelation using an enzyme – horseradish peroxidase. The enzyme sticks printed droplets together by creating crosslinks between phenyl groups in a polymer in the bioink.
For that process to occur, it is necessary to add hydrogen peroxide. Hydrogen peroxide can kill cells, so contact between the hydrogen peroxide and the cells must be limited. The researchers have got around this problem by carefully timing the release of the bioink containing the cells and the hydrogen peroxide, which allows the enzyme to bond the polymer in the bioink without killing the cells. The researchers report that 90% of the cells survived the printing process and that the new inkjet bioprinting technique allowed them to print several complex 3D structures.
While this is certainly a breakthrough in 3D inkjet bioprinting, before the researchers can use the technique to print more complex structures such as organs, they need to find new scaffolds that can be used to support the 3D printed tissues during the printing process.
The research paper – Drop-On-Drop Multimaterial 3D Bioprinting Realized by Peroxidase-Mediated Cross-Linking – was recently published in the journal Macromolecular Rapid Communications.