The new bio-ink contains two different polymer components: a natural polymer extracted from seaweed and a sacrificial synthetic polymer used in the medical industry.
"Designing the new bio-ink was extremely challenging. You need a material that is printable, strong enough to maintain its shape when immersed in nutrients and that is not harmful to the cells. We managed to do this," said lead researcher Adam Perriman from school of cellular and molecular medicine.
The synthetic polymer causes the bio-ink to change from liquid to solid when the temperature is raised and the seaweed polymer provides structural support when the cell nutrients are introduced.
"The special bio-ink formulation was extruded from a retrofitted benchtop 3D printer, as a liquid that transformed to a gel at 37 degrees Celsius, which allowed construction of complex living 3D architectures," Perriman added.
The findings, published in the journal Advanced Healthcare Materials, could help printing complex tissues using the patient's own stem cells for surgical bone or cartilage implants, which could be used in knee and hip surgeries.
The team was able to differentiate the stem cells into osteoblasts - a cell that secretes the substance of bone cells that have secreted the matrix of cartilage and become embedded in it - to engineer 3D printed tissue structures over five weeks, including a full-size tracheal cartilage ring.
"What was really astonishing for us was when the cell nutrients were introduced, the synthetic polymer was completely expelled from the 3D structure, leaving only the stem cells and the natural seaweed polymer," Perriman noted.
This created microscopic pores in the structure which provided more effective nutrient access for the stem cells.