Using rapid 3D bioprinting technology developed in the lab of Shaochen Chen at UC San Diego, a team of international researchers has created coral-inspired structures that are capable of growing dense populations of microscopic algae. The work could lead to more efficient bioreactors for biofuel, new bio-inspired materials and new techniques to repair and restore dying coral reefs.
Chen’s 3D-printing method was essential to the process, as normal 3D printers would take hours—not minutes—to print a structure this complex featuring living tissue.
“It would be like keeping a fish out of the water,” Chen said. “The cells that we work with won't survive if kept too long out of their culture media. Our process is high throughput and offers really fast printing speeds, so it's compatible with human cells, animal cells, and even algae cells in this case.
In nature, coral capture and convert light to generate energy, and they do so efficiently in an extreme environment. To mimic that complex light-scattering ability, the researchers used cellulose nanomaterials to print the artificial skeleton, which supports coral-like tissue.
“Cellulose is an abundant biopolymer; it is excellent at scattering light and we used it to optimize delivery of light into photosynthetic algae,” lead researcher Silvia Vignolini, a professor at the University of Cambridge, explained.
According to the study, published in Nature Communications, while the skeleton contains cellulose nanocrystals, the coral tissue actually comprises a gelatin-based polymer hydrogel mixed with living algae cells and cellulose nanocrystals. Tiny cylindrical structures on the surface act as coral tentacles, increasing the surface area for absorbing light. The nanocrystals embedded throughout printed structure also serve to improve light-absorption so the living algae cells can photosynthesize efficiently.
Once designed and printed, Vignolini, Chen and colleagues tested the structures by using them as incubators for algae growth. The researchers found the-3D printed structures grew a commercial strain of microalgae, Marinichlorella kaistiae, up to 100 times more densely than natural corals.
While there are many uses for this technology, the researchers ultimately hope to find a way to restore dying coral reefs around the world.
“By copying the host microhabitat, we can also use our 3D bioprinted corals as a model system for the coral-algal symbiosis, which is urgently needed to understand the breakdown of the symbiosis during coral reef decline,” said first author Daniel Wangpraseurt, professor of chemistry at the University of Cambridge. “We hope that our technique will be scalable so it can have a real impact on the algal biosector and ultimately reduce greenhouse gas emissions that are responsible for coral reef death.”
In future studies, Chen and Wangpraseurt intend to build upon this work to better understand the symbiosis between algae and corals.
Photo: Microalgae growing on the 3D-printed coral structure. Credit: Nature Communications