Bioengineers of the University of Pennsylvania have made a significant contribution to the field of tissue engineering. The technology could one day be applied to generate replacement organs for ailing patients or produce meat for consumption without the need to slaughter animals.
So far, bioengineers have successfully generated 2D living tissue but engineering larger 3D structures has proved difficult.
Until bioengineers Jordan S. Miller, Christopher S. Chen and their team decided to deploy the open source Reprap 3D printer and take a different approach at solving identified problems.
For cells to stay alive they need a constant supply of oxygen and nutrients. When structured in 2D layers the cells can extract oxygen from their environment. But when cells are stacked in 3D those blocked-in quickly die off.
In most ‘natural’ living tissue a vascular system serves as the cells’ oxygen supply route but attempts to recreate a blood vessel network in engineered tissue failed.
The key to Miller’s team success was reversing previous experiments.
In those earlier attempts bioengineers also used the 3D printing technique. The cells, immersed in a gel, are deposited layer-by-layer forming tissue interlaced with hollow tunnels. But the printing proces produces seams making the tunnels weak. As soon as nutrient-rich fluids are pumped through the vascular network the seams burst. Another problem is that many useful cells like liver cells can’t survive the printing process.
Miller and his team turned the printing process inside out. Instead of printing the tissue, they printed the vascular network.
They used the Reprap 3D printer to produce a lattice of sugar within a mold. Than they filled the mold with gel containing the living cells, encapsulating the lattice. When the cells have formed into solid tissue the sugar is dissolved leaving a network of hollow tunnels.
The open source Raprep 3D printer used in the experiment contributed to the success. Miller: “We launched this project from innovations rooted in RepRap and MakerBot technology and their supporting worldwide communities. A RepRap 3D printer is a tiny fraction of the cost of commercial 3D printers, and, more important, its open source nature means you can freely modify it. Many of our additions to the project are already in the wild.”
Image: 3D printer by Thijs Beckers