Printing Human Body Parts: Bio-Ink Drops Showing Promise for Regenerative Medicine

A method of making bioink droplets to stick to each other using an enzyme driven crosslinking method has been developed by researchers from Osaka University that increases the range of cell types with the availabllity to be used in the 3D printing of complex biological structures from a vast variety of cell types which holds promise for regenerative medicine such as use in iPS cells as published in Macromolecular Rapid Communications.

Printing of human body parts may seem like it’s science fiction to some individuals, but it is rapidly becoming a technology of science reality. This technology has a strong potential to contribute greatly in regenerative medicine. Bioprinting may still face some technical challenges, but is well on its way. Processing the bioink and making it stick to itself and hold the printed gel object have been proving tricky especially in the inkjet printing. Only a few methods exist for gluing the bioink droplets, with not all methods working for every kind of cell, inspiring the researchers to come up with new and alternative techniques, refining an enzyme driven approach in which to stick the biological ink droplets together, enabling complex biological structures to be printed.

The process of actually printing tissue structures/objects is a complex process. The bioink must have low viscosity to flow through the printer, but needs to be able to rapidly form a high viscose gel like object when printed. This new approaches does just that while avoiding sodium alginate, offering great potential for tailor made scaffold materials for specific regenerative purposes says Shinji Sakai.

Sodium alginate is currently the main agent used for gelling in inkjet bioprinting, which has issues in compatibility with certain cell types. The new method using hydrogelation mediation by an enzyme called horseradish peroxidase creates cross links between phenyl phenyl groups of added polymer when in the presence of the oxidant hydrogen peroxide.

Hydrogen peroxide can damage cells, researchers carefully timed the delivery of cells and the hydrogen peroxide into separate droplets as to limit contact so that the cells would not get damage and keeps them alive. Over 90% of the cells remained viable in the conduction of biological test gels that were prepared in this new manner. A number of other complex test structures may also be grown in this manner from different types of cells.

It is possible to induce stems cells to differentiate in a variety of different manners which has been made possible by the advances in induced pluripotent stem cell technologies. There is a need for new scaffolds to be able to print and support these cells to move closer to achieving the goal of printing full 3D functional tissues. This new method is extremely versatile and has the ability to help all groups working towards this goal says Makoto Nakamura.