Scientists at the University of Bristol have developed a new stem cell-containing bio-ink that allows 3D printing of living tissue, known as Artist’s impression of bio-printing—a rapidly emerging technique for the building of living 3D tissue constructs. Image credit: University of Bristol.Artist’s impression of bio-printing—a rapidly emerging technique for the building of living 3D tissue constructs. Image credit: University of Bristol.bio-printing. Ultimately, it could allow for the production of complex tissues for surgical implants.

The bio-ink contains two different polymer components: a sacrificial synthetic polymer used in the medical industry and a natural polymer extracted from seaweed. 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.

Lead researcher Dr. Adam Perriman, from the School of Cellular and Molecular Medicine, says the bio-ink formulation was extruded from a retrofitted benchtop 3D printer as a liquid that transforms to a gel at 37 degrees Celsius, which allows for the construction of complex living 3D architectures. The team was able to differentiate the stem cells into osteoblasts, cells that secrete the substance of bone, and chondrocytes, 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 says. "This, in turn, created microscopic pores in the structure, which provided more effective nutrient access for the stem cells."

The team's findings could eventually lead to the ability to print complex tissues using the patient's own stem cells for surgical bone or cartilage implants, which in turn could be used in knee and hip surgeries.

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