What looks a bit like a pupil is actually a cross-section through a special kind of blood vessel: this multi-layered structure was created from living cells and a gel matrix using 3D printing.
3D printing has revolutionized many areas of technology, but it is also becoming increasingly important in biomedicine. With these processes, precisely fitting implants, scaffolding structures for organs grown in the laboratory and other useful tools can be printed. Thanks to bioprinting, it is now even possible to print living cells and tissue. Hydrogels are usually used as “ink” into which living stem cells are injected in the desired structure.
So far, however, bioprinting processes are still in their infancy and it has been difficult to produce more complex or hollow biological tissue structures. However, a team led by Marc Falandt from the Regenerative Medicine Center Utrecht has now combined two bioprinting processes and optimized them in such a way that such tissues and structures can also be produced with them. The starting point for this is so-called volumetric bioprinting, in which a hydrogel is hardened by fine laser beams only in the desired areas, the rest is washed away. This creates the finest framework structures.
Falandt’s team has optimized this process in such a way that it can be used to create gelatin-based hollow frameworks that can later be moved with molecules and cells. To do this, the researchers first use melt electroprinting to print a template of the required blood vessels from plastic – they serve as placeholders for the subsequent cavity of the vessels. This placeholder framework is then sunk into the photoactive hydrogel. Then the gel is stabilized by a laser in the area around the stencils, and the rest is washed away. Finally, biomolecules and cells can be specifically placed in the gel layer inside or outside the templates and grow into tissue there.
This image shows a cross-section of a blood vessel grown using this technique. It consists of two types of stem cells that were placed on the scaffold in such a way that they grew into a multi-layered vessel-like structure. The fluorescence staining shows the different cell types. These cells have not yet differentiated and not all layers of a finished blood vessel are present. Falandt and his team now want to tackle this in their next attempts.