It looks like a bizarre, green waffle, but the 3D printed structure could offer a sustainable way to clean pollutants from water, say University of California San Diego researchers.
The researchers describe the structure as an "engineered living material”.
The ‘waffle’ is a 3D-printed structure made of a seaweed-based substance combined with genetically engineered bacteria.
The bacteria are engineered to produce an enzyme that transforms various organic pollutants into safe molecules.
The bacteria were also engineered to self-destruct in the presence of a molecule called theophylline, which is often found in tea and chocolate. This offers a way to eliminate them after they have done their job.
Jon Pokorski, a professor of nanoengineering at UC San Diego who co-led the research, said, "What's innovative is the pairing of a polymer material with a biological system to create a living material that can function and respond to stimuli in ways that regular synthetic materials cannot.”
Susan Golden, a faculty member in the School of Biological Sciences, said, "This collaboration allowed us to apply our knowledge of the genetics and physiology of cyanobacteria to create a living material.
“Now we can think creatively about engineering novel functions into cyanobacteria to make more useful products."
To create the living material in this study, the researchers used alginate, a natural polymer derived from seaweed.
The researchers hydrated it to make a gel and mixed it with a type of water-dwelling, photosynthetic bacteria known as cyanobacteria.
The mixture was fed into a 3D printer.
After testing various 3D-printed geometries for their material, the researchers found that a grid-like structure was optimal for keeping the bacteria alive.
The chosen shape has a high surface area to volume ratio, which places most of the cyanobacteria near the material's surface to access nutrients, gases and light.
The increased surface area also makes the material more effective at decontamination.
In this study, the researchers demonstrated that their material can be used to decontaminate the dye-based pollutant indigo carmine, which is a blue dye that is widely used in the textile industry to color denim.
In tests, the material decolourised a water solution containing the dye.
The researchers also developed a way to eliminate the cyanobacteria after the pollutants have been cleared. They genetically engineered the bacteria to respond to a molecule called theophylline. The molecule triggers the bacteria to produce a protein that destroys their cells.
Pokorski said, "The living material can act on the pollutant of interest, then a small molecule can be added afterwards to kill the bacteria. This way, we can alleviate any concerns about having genetically modified bacteria lingering in the environment."
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