What are the biggest challenges to being able to print organs?

Answer

Moving beyond the adherent 2D culture, building cells up in any 3D geometry means you must keep the cells alive. As the volumes we are attempting to construct get thicker than about 200um, we will have to somehow address the innermost cells and keep them healthy. If you have ever done cell culture, you might not think about this, but it is pretty simple because the cells are pretty flat and you can address a large surface area– simple steps of aspirating old media and changing to fresh media will usually do the trick to keep your culture happy. But in considering the structure of thicker tissues, it is quite amazing to study the vascular design that nature uses to deliver nutrients (and remove wastes) to our tissues and to every cell. In order to print out thicker viable tissues and organs, how can we get a flow of oxygen and nutrients into thicker tissues? Can we somehow print out blood vessels along with the layers of cells and growth factors? ArtiVasc 3D is just one example of a group dedicated to solving this very problem, and researchers all over the world are working on this. In addition to vascular constructs, there are alternative approaches that could be considered, such as: Can we exploit diffusion properties, and perhaps develop materials that create structure and allow for diffusion deep into the structures?

Another challenge to building any type of tissue is in getting the resolution needed to deposit the various cell types into the patterns needed to mimic natural tissue. While it’s true that biology takes the reins and cells can self-organize, they do need to first be placed in proximity to one another. To this end, researchers have developed laser assisted bioprinting: a method in which people can actually control individual cells and deposit them very precisely. Another method uses acoustic energy to generate very small droplets and can also be used to get the resolution needed.