It is not easy to print with living cells; some tougher cells like bone marrow and skin have been 3D printed using modifed ink-jet printers, but they can subject the cells to shear forces and clog easily. Other techniques subject the cells to excessive heating.
At Heriot-Watt University, they have developed a new valve based technology that is gentle and sensitive enough that they can work with delicate human embryonic stem cells (hESCs) for the first time. Dr. Will Shu tells the BBC:
We found that the valve-based printing is gentle enough to maintain high stem cell viability, accurate enough to produce spheroids of uniform size, and most importantly, the printed hESCs maintained their pluripotency - the ability to differentiate into any other cell type.
Embryonic stem cells can turn into any kind of cell, and could theoretically be printed into almost any kind of organ. Shu continues in the Heriot-watt University release:
In the longer term, we envisage the technology being further developed to create viable 3D organs for medical implantation from a patient’s own cells, eliminating the need for organ donation, immune suppression and the problem of transplant rejection.
The researchers attached two reservoirs of "bio-ink" to large diameter nozzles that won't hurt the cells, with valves controlled by an arduino computer, and the whole thing mounted on a 3 axis CNC machine. They chose two reservoirs to dispense two different inks at the same time. They then printed out a grid of blobs and found that the cells in the blobs, (or spheroid aggregates), survived and thrived. They printed them in a pattern of the school's logo to show that they could do complex patterns. They conclude:
The ability to print hESCs for the generation of 3D structures will allow us to create more accurate human tissue model, which is essential to the in vitro drug development and toxicity-testing. Additionally, this may also pave the way for human stem cells to be incorporated into clinical protocols either for patient implantation of in-vitro regenerated organ or direct in-vivo cell printing for tissue regeneration.
We have joked before about how soon we would have a Kinko's for Kidneys, an easy way to print out organs as needed. Making a grid of blobs of stem cells isn't quite that, but it's a start.
Read the whole thing in IOP Science: Development of a valve-based cell printer for the formation of human embryonic stem cell spheroid aggregates