Food Dyes Facilitate 3D Bioprinting of Complex Tissue

By David Douglas

May 20, 2019

NEW YORK (Reuters Health) - Using synthetic and natural food dyes rather than standard toxic light-blocking chemicals enables production of biocompatible and cytocompatible hydrogels containing intricate and functional vascular architectures, according to researchers.

This could help pave the way to three-dimensional printing of replacement organs, they note in the May 3 issue of Science.

"One of the biggest road blocks to generating functional tissue replacements has been our inability to print the complex vasculature that can supply nutrients to densely populated tissues," senior author Dr. Jordan S. Miller of the University of Washington, Seattle, said in a statement.

"Ours is the first bioprinting technology that addresses the challenge of multivascularization in a direct and comprehensive way," he added.

The projection-stereolithography process used by the authors allows complex structures to be generated "in minutes," they note in their article.

Dr. Miller and colleagues produced monolithic transparent hydrogels with functional intravascular topologies, including efficient intravascular 3D fluid mixers and 3D functional bicuspid venous valves. They then went on to explore the oxygenation and flow of human red blood cells during tidal ventilation and distension of a proximate airway via printed hydrogels patterned with alveolar model topology.

The hydrogels, say the researchers, could withstand more than 10,000 ventilation cycles over six hours during RBC perfusion and while switching the inflow gas between humidified oxygen and humidified nitrogen.

To further test the approach as therapeutic implants for liver disease, the team built a more advanced carrier "that can deliver hepatic aggregates within natural fibrin gel, has a vascular compartment that can be seeded with endothelial cells, and incorporates structural hydrogel anchors to physically, rather than chemically, retain the fibrin gel and facilitate remodeling between the graft and host tissue."

After 14 days of engraftment in mice with chronic liver injury, tests indicated surviving functional hepatocytes. These findings, among others, "address long-standing design limitations in tissue engineering that have hindered progress of preclinical studies."

Dr. Miller told Reuters Health by email, "In the short term we definitely need many more people to register to be organ donors; human organ transplant will continue to be a crucial part of medicine."

"I expect bioprinted tissues to become a major part of medicine within the next 10 to 20 years," he added. "Our goal over the next decade is to be able to generate patient-specific organ replacements at scale made from their own cells, and understand how they could integrate nearly seamlessly with the human body's anatomy and physiology. There is much work left to be done but there are many reasons to be optimistic for that exciting future."

Dr. Anthony Atala, director of the Wake Forest Institute for Regenerative Medicine, in Winston-Salem, North Carolina, told Reuters Health by email, "This work represents a significant advance in the ability to print small blood vessels."

"The authors," he observed, "used an established printing technique, but used food dye on gels to help create miniature channels. This technology would be useful for the printing of tissues and organs."


Science 2019.