Researchers based in Dresden, Germany are pondering not only the future of healthcare materials, but also their potential beyond Earth. Michael Gelinski, professor and head of the Center for Translational Bone, Joint, and Soft Tissue Research, and his team are developing living inks that can be used by astronauts without assistance from Earth. Not an option — like Mars.
Similar to the ink cartridge in your office printer, bioinks contain living cells suspended in a solution of biopolymer or a mixture of biopolymers such as alginate or gelatin. But instead of printing a document, extrusion-based bioprinters use bioinks to produce layered 3D hydrogel structures embedded with cells contained in the ink.
These constructs, whose shapes are preprogrammed into a computer, have been used to make patient-specific implants and to create living models that mimic organ tissue, which can be used for basic research purposes.
Challenges facing bioinks in space
Currently, only cell-filled bioinks are printed where the necessary facilities, equipment, and staff are available on Earth and the effects of gravity are known. Bioprinting under microgravity, such as on the International Space Station (ISS), where resources and personnel are limited, is a more complex matter.
In order for the cell-filled bioinks to survive the rocket launch and journey to the ISS, they need to be stored at low temperatures for up to a month. They are preferably stored in the form of a ready-to-use cartridge that astronauts can load into an extrusion-based bioprinter installed on the ISS.
“The European Space Agency ESA has commissioned an industry consortium to build such a device in combination with a unit for further cultivation of bioprinted constructs,” Johannes Windisch, Ph.D. student in Gelinski’s research group informed us. “If pre-added (That iscell-laden) bioinks can be launched and used directly for the bioprinting process, which will significantly facilitate the entire procedure.
Preparation and evaluation of bioinks
To investigate the feasibility of this scenario, researchers embedded green microalgae and different mammalian cells into alginate-methylcellulose (Alg-MC) scaffolds. These include human mesenchymal stem cell line (hTERT-MSC), liver (HepG2) and bone (SAOS-2) cell lines, and primary human dental pulp stem cells.
To prepare the bioinks, they first dissolved a mixture of alginate and methylcellulose in water, phosphate-buffered saline, or human plasma. Then, they added live cells and loaded different bioink formulations into cartridges, which were stored at 4 degrees Celsius for one to four weeks, which could easily be maintained throughout the cargo delivery process to the ISS.
After warming the cartridges to room temperature, they used bioinks to print 3D scaffolds, which were ionically crosslinked and incubated under ideal conditions for up to 28 days.
The authors found that all bioinks retained their printability, regardless of the cold-storage period, despite the reduction in viscosity. Notably, storage of bioink containing microalgae at 4°C did not affect the viability and activity of microalgae, which are known to tolerate various environmental conditions.
Even after four weeks of storage, the microalgae were able to undergo photosynthesis and produce oxygen with the same efficiency as the reference group of fresh microalgae using the available light. In space missions, bioinks containing microalgae could be used as a food or nutrient source for life support and wastewater treatment.
Unlike microalgae, where viability was not affected by low-temperature storage, the viability of human cells decreased to varying degrees. However, when the cells were restored to optimal conditions after storage, their viability was recovered. The data indicate that metabolically active cells are more affected by cold storage than quiescent cells and that storage temperature has a greater effect than storage duration.
“For each cell type of interest, the optimal bioink composition and storage conditions must first be evaluated. “Our study is a starting point for more detailed investigations,” Johannes pointed out.
While the authors envision that these bioinks could one day be used to create patient-specific tissues to treat injured astronauts, in the meantime, they could be used to make 3D tissue models to investigate the effects of microgravity, radiation, and other astronaut conditions. subject in space.
“Furthermore, the effect of microgravity on the bioprinting process needs to be further investigated to set up a workflow and define the design of bioprinted constructs that will eventually operate on the ISS,” said Anja Lod, another author of the study. . “To this end, with the support of the German Space Agency at DLR, our lab will conduct the first bioprinting experiments in a parabolic flight campaign in September 2023.”
When asked how storable bioinks could improve current bioprinting processes on Earth and what new applications might emerge, Johannes had several ideas.
“Proposable bioinks will allow bioprinting experiments to be conducted in labs not equipped for the production and harvesting of large cell numbers. They could also facilitate bioprinting applications outside of research labs, for example, in hospitals or even for the treatment of people injured in natural disasters or military conflicts. Finally, the production and trade of storable bioinks could be an interesting business model.
Reference: Johannes Windisch, Olena Reinhardt, Michael Gelinski, et al.,Bioinks for space missions: effects of long-term storage of alginate-methylcellulose-based bioinks on printing, cell viability and function, Advanced Healthcare Materials (2023). DOI: 10.1002/adhm.202300436
Feature image credit: New York Public Library on Unsplash