3D Bioprinting Process Produces Living Coral Microhabitats

An international team of scientists led by the University of California San Diego has produced the first 3D-printed synthetic coral tissues that can house symbiotic algae.

The team built three different 3D-bioprinted corals. Each mimicked a feature of real corals: the skeleton, the gut, and the skin. Scientists now can use these novel tools to study the causes of coral bleaching, how to minimize it, and how to identify resilient strains of algae.

“In the longer term, it may allow us to build living 3D-printed corals for restoration,” said team member Martin Tresguerres, a Scripps Oceanography marine physiologist.

But for now, the 3D bioprinting technology makes it possible to study the parts of the complex symbiotic system one by one. This is significant because even two coral colonies of the same species may coexist with different strains of algae and microbes in different structural arrangements.

“It’s difficult to understand the fundamental mechanisms that drive the coral-alga symbiosis when your experimental specimens are so different from each other,” Tresguerres said.

“Because we can finely control light with special optics, we can create nanometer-to-microscale-structured 3D features in a couple of seconds,” said team leader Daniel Wangpraseurt, a marine biologist at UC San Diego’s Jacobs School of Engineering and Scripps Institution of Oceanography. “This is motivated by understanding the functioning and breakdown of the symbiosis, including phenomena such as coral bleaching.”

Coral bleaching threatens reef survival. As hotspots of biological diversity, healthy coral reefs serve economic interests through tourism, fisheries, and the prevention of coastal erosion.

The complexity of symbiosis involves an interconnected microscale landscape that creates very different physical and chemical conditions affecting algae physiology and many other factors. Wangpraseurt and 17 co-authors detail these and other findings in the journal Advanced Functional Materials. The work is supported by the Gordon and Betty Moore Foundation’s Symbiosis in Aquatic Systems Initiative and the National Science Foundation.

Wangpraseurt and co-authors published a 2020 paper in Nature Communications that described using 3D printing of polymers to mimic the coral skeleton and encapsulate green microalgae. The process of enhanced photosynthesis allowed algae to grow at high density, an important biotechnology for producing biodiesel.

“The long-term goal would be, instead of using polymers to create the tissue scaffolds, to use living coral cells,” said Tresguerres. “The technology is similar to that currently being used for building human organs and tissues for biomedical purposes.”

Co-author Shaochen Chen, professor and chair of the nanoengineering at the UC San Diego Jacobs School of Engineering, pioneered the method for 3D bioprinting of organs and tissues used in the project. Also contributing to the study from UC San Diego were nanoengineering postdoctoral researchers David B. Berry and Shangting You; nanoengineering PhD students Henry H. Hwang, Yazhi Sun, and Yi Xiang; and from Scripps Oceanography, biogeochemist Julia M. Diaz, postdoctoral scholar Alexander M. Clilfford, and graduate students Sydney Plummer and Samantha K. Noël.

The team mimicked the different skeletal porosities of the corals with 3D printing to see how they would affect the production of hydrogen peroxide. This toxic form of oxygen is a prime suspect in driving the loss of symbiotic algae from coral during the bleaching process.

The more porous skeleton allowed the hydrogen peroxide to flow away more easily than the less porous one, establishing a potential link to bleaching resilience.

“This highlights the importance of the skeleton microhabitat for physiological processes such as coral bleaching,” Wangpraseurt said. “Our future focus will be to have co-cultures of coral and algae cells growing in an artificial tissue, eventually developing a more stable synthetic symbiotic system that has enhanced longevity.”

Study co-authors include Sing-Teng Chua and Silvia Vignolini, University of Cambridge; Helena F. Willard and Jaap Kaandorp, University of Amsterdam, The Netherlands; Todd C. LaJeunesse, Pennsylvania State University; and Mathieu Pernice, University of Technology, Australia.