The mass extinction of coral reefs is a global catastrophe, but the extent of their success as organisms has lessons for science. A typical example: These 3D-printed “bionic corals” by Cambridge researchers are more than just scaffolds for fragile microorganisms – they are made up of them.
When 3D-printed corals seem familiar, a few years ago, some other researchers suggested using structures printed to resemble the complex shapes of reefs as a solid base on which new corals and other animals could grow. It's a good idea, but a reef has more to offer than a solid foundation.
Corals are indeed a highly developed symbiosis between the coral organisms themselves and the algae living in them. The algae use photosynthesis to produce sugar for their host, and the corals provide a safe living environment – and interestingly enough, they are also very efficient in collecting and redirecting light. This partnership has been fruitful for millions of years, although rising sea temperatures and acidity disrupt the delicate balance necessary for success.
The Cambridge team realized that to successfully mimic the coral micro-ecosystem, it is necessary to reproduce the special quality of the collection and scattering of sunlight for use by resident algae. To this end, they closely examined the structure of corals and worked on redesigning them at the microscopic level. But instead of using an ordinary durable substrate, they created a kind of living gel.
"We developed an artificial coral tissue and scaffold with a combination of polymer gels and hydrogels doped with cellulose nanomaterials to mimic the optical properties of living corals," said Cambridge chemist Daniel Wangpraseurt, lead author of the paper, in which the Technology is described. Algae were also infused into the mixture, so the researchers printed essentially living matter.
This technique is already being tested and used for medical purposes – for example to print part of an organ or tissue for implantation. In this case, it does not have to be printed with a specific large format shape, but with an extremely complex internal geometry that maximizes the range of the light falling on the surface. This must be done very quickly, otherwise the algae will die from exposure.
The resulting bioprinted structure is an ideal home for the algae and generates growth rates that are many times faster than that of a normal medium. That doesn't mean the next step is to grow corals super-fast. In fact, there is no reason to believe that this will actually lead to coral restoration. On the other hand, this type of simulation could lead to a better understanding of the ecosystem in which the coral-algae partnership thrives and how it can be promoted.
In the meantime, the promise of multiplying the growth rate of algae has found commercial acceptance today, and a startup called Mantaz has been founded to use the technology in the short term.