Bio-ink breakthrough allows for 3D printing

Researchers create stem cell ‘bio-ink’ that they hope will be used for regenerative medicine, drug screening and the study of developmental biology.

Longevity.Technology: Even if growing organs from clusters of cells in the lab doesn’t sound particularly easy, it also follows the rule of being much harder than it sounds.

The TRL score for this Longevity.Technology domain is currently set at: ‘Early proof of concept demonstrated in the laboratory

The TRL score for the technology addressed in this article is: “Early proof of concept demonstrated in the laboratory’

This is particularly the case in the tricky task of making lab cells emulate the correct structure needed to create a transplantable organ. But some hope may be around the corner, according to a team at the University of Illinois in Chicago, who have developed a process for 3D printing biological tissues without the use of scaffolds [1].

Their novel technique sprays a bio ‘ink’ (made up only of stem cells) from a nozzle onto a bath of micron-scale hydrogel beads, which preserve the cells’ shape while they are being printed. Once in place, the cells are exposed to UV light that stimulates the creation of cross-links between the beads, effectively locking them into position. Once the beads are locked down, the cells too begin to interconnect and grow into the structure set out for them. The growing tissue is fed and cleaned by moving fresh nutrients and waste products in and out through the spaces between the cross-linked beads. Once the tissue has grown to the required size, the bead substrate can be removed by gentle shaking or by chemically induced decay, leaving the intact, ready to use, tissue behind.

“The hydrogel bead bath has unique properties which allow for both printing of the cell-only bio-ink in complex architectures, and subsequent temporary stabilization of these cell-only structures to allow for cell-cell junctions to form,” says the principal investigator Eben Alsberg. “Using chemistry we can then regulate when the beads go away.”

Stem cells were used because they can differentiate into a wide variety of other cell types, giving Alsberg and his team’s technology a broad portfolio of potential tissues to create. So far, they have used the stem cells to 3D print a cartilage ear and a rodent-sized “femur” in the hydrogel bead bath, but they hope to apply it to more complex tasks in the future.

“For the first time, cell-only constructs can be printed in intricate forms that are made up of different cell types without a hydrogel carrier or traditional scaffold that can then be stabilized for a period of a day to weeks. We’ve demonstrated that cell aggregates can be organized and assembled using this strategy to form larger functional tissues, which may be valuable for tissue engineering or regenerative medicine, drug screening and as models to study developmental biology,” Alsberg said.