3D printing living ink

Researchers are using microbial inks to 3D print living materials
29 November 2021

Interview with 

Neel Joshi, Northeastern University


E. coli bacteria


Who’s seen the movie Flubber, with Robin Williams? Remember that wacky, green, jelly-like substance that comes alive and starts bouncing around breaking everything it encounters on its path? Well that’s not quite the direction science aspires to go, but a team of researchers at Northeastern University have successfully genetically programmed bacteria to make a printable ink that can be used in a 3D printer. Using this ink, they have created a gel that isn’t green and it doesn’t bounce around crazily against the walls, but it is alive because it contains living cells that can release therapeutic drugs or remove toxins from their surroundings. Iacopo Russo heard from Neel Joshi how it works...

Neel - It starts with genetic engineering of e-coli

Iacopo - Is that the bacteria we have in our intestines?

Neel - Yes. It's found in your intestines and in soil. We introduce new genes that didn't previously exist in e-coli and then we tell the cells when to produce a customized protein polymer that would assemble in multiple dimensions. Individual protein is like a building block, a 'bead'. That bead is going to assemble into this fibre, like many beads on a string, that fibre will intern bundle into larger structures.

Iacopo - Okay. What does it look like in practice? If I entered your lab what would I be looking at?

Neel - You would be looking at a lot of bacteria growing in an incubator. We load the material that comes out of those bacteria into the 3D printer setup.

Iacopo - When you say 3D printers, do you mean the ones that some people now have at home?

Neel - Yes. Very similar to that, the only difference is that our mechanism of printing doesn't involve heating. We designed the material that we made so that it's firm enough to hold its own weight when it's resting. But then when you apply pressure to it, it will flow like a liquid. I think everybody's familiar with this concept in the form of toothpaste, which is stuck in the tube. It will flow if you apply pressure. We designed our materials to have similar properties, and then we use pressure to do the printing rather than heat.

Iacopo - What kind of things have you made? What does it look like when it comes out of the printer?

Neel - A clear gelatine-like substance. Like jello with no food colouring in it. It's composed of our engineered cells and the custom protein polymer that they produced.

Iacopo - But jello is dead in a way, there's no living thing in it, whereas your material has living cells in it. What can these cells do?

Neel - We can not only program the ability to make the ink into the cells, but we can also introduce other features that you might find in a living system. For example, cells that can respond to their environment could release some drug or they could bind and remove some pollutant from their surroundings, or they could even undergo a process of cell suicide inside the material, if we wanted to limit the spread of those cells into the surrounding environment.

Iacopo - Right. Because this thing is alive and it's made of microbes and usually we want to defend ourselves from microbes whereas you've created something out of microbes.

Neel - We are certainly careful to use only non-pathogenic lab strains and I think that this is a realistic way to make materials in a scalable manufacturing context. It's already done in some cases with insulin, perhaps being the example that's been around for the longest.

Iacopo - This already sounds like science-fiction, but what's the wildest application you can envision for the future?

Neel - One of the things that's kind of obvious as a place that this could be particularly useful is for building structures in space organizations like NASA have already started planning for how they would build structures and habitats in extra terrestrial environments.

Iacopo - So we're talking about when we colonize Mars?

Neel - Yeah. Mars or the Moon, or perhaps on a space station. In all those contexts, 3D printing comes up repeatedly as a very versatile way to make multiple different buildings or structures or basically whatever you want. A problem with that is that it would be cost prohibitive to ship tons and tons of plastic for using a 3D printer. You would need a way to make your printing ink locally. The way to do that is really with microbes. You could take a few microbes with you in a small vial and then kind of make what you needed from those microbes.

Jassy - At the Royal Horticultural Society, we have a 'members advisory service' where people send us pictures of things that are going on in their gardens and ask for advice about them. One thing we've noticed this year is that we've had 76% more inquiries about saprophytic fungi, which grow on dead material, than we did last year. It's usually with the angle of, 'what is this? I'm afraid of it. Is it going to cause harm? How do I get rid of it?' We're trying to educate them to say, 'well, there's very few things that are out there that are going to be causing any harm to your garden. The overwhelming majority will be doing a good service by rotting down dead material.' This is the type that we've seen so many more of being sent into us this year and in doing so that liberates the nutrients locked up in that woody material.


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