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Biomaterials

Living ceramic can smell formaldehyde

The material can also capture carbon, depending on the bacteria it holds

by Prachi Patel
December 18, 2024 | A version of this story appeared in Volume 102, Issue 39

 

By populating porous clay with bacteria, researchers have made living ceramics that sense tiny amounts of toxic formaldehyde and that capture carbon dioxide from air (Adv. Mater. 2024, DOI: 10.1002/adma.202412555).

Engineered living materials typically consist of soft hydrogels, polymers, or biofilms seeded with microorganisms that allow the materials to sense and degrade toxins, deliver therapies, and repair themselves.

A pentagonal cylinder placed in a shallow glass dish with liquid on left; the same cylinder glowing green on right.
Credit: Adv. Mater.
After 4 days of incubation with engineered Escherichia coli bacteria, 3D-printed ceramic scaffolds (left) glow under ultraviolet light (right).

For the challenging task of hosting living cells in a hard material, bioengineer Anton Kan, materials scientist André R. Studart, and colleagues at Swiss Federal Institute of Technology (ETH), Zurich, 3D printed ceramic structures with pores ranging in size from 20 µm to 130 µm and 20 nm to 80 nm. The smaller pores create a large surface area for cells to stick and proliferate, while the bigger pores allow the flow of nutrients.

The team used a vacuum to pull nutrient-laden liquid into the ceramic’s pores and dipped the structures into different bacterial cultures for inoculation. They then placed the structures in shallow pools of the nutrient solution. As water in the ceramic evaporates, capillary action takes over, Kan says. “The liquid moves up the ceramic column from the reservoir.”

The bacteria multiplied and performed their functions for at least 2 weeks. When the team used wild photosynthetic cyanobacteria, the microbes pulled CO2 from the air into the ceramic to grow. To make a formaldehyde detector, the researchers used Escherichia coli engineered with a genetic circuit that converts isoamyl alcohol into banana-scented isoamyl acetate in the presence of as little as 1 PPM of formaldehyde.

Avinash Manjula-Basavanna, a bioengineer at Northeastern University, says that the mechanical properties of the living porous ceramics might limit their applications but that this is “a nice demonstration of harnessing microbes for smart functionalities.”

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