“Many bioink designs have already been explored, none so far have fully leveraged the genetic programmability of microbes to rationally control the mechanical properties of the bioink.”
Attempts to print living microbial structures have been attempted with inkjet printing, contact printing, screen printing, and lithographic techniques, but so far, it’s extrusion, or 3D-printing that has allowed the field to truly advance.
Various forms of printed microbial structures have been experimented with before now, but all of these required some sort of additional polymer. Instead, the team has developed a type of bioink that is completely derived from proteins produced by E.coli cells. It is by then injecting other, genetically modified E.coli cells, that the living structures are formed to allow for drug release and toxin absorption.
The genetically modified E.coli produces this ink by fusing positively and negatively charged protein modules, which attach to one another and lock to create crosslinked fibers. After this, the team filtered the resulting product to further concentrate the bacteria in order to create a compound of the suitable viscosity and elasticity needed for printing.
The result? A gel that can be piped to produce threads half a millimeter wide: that’s half the size of a pencil tip! This thread is strong enough to hold up even when stretched 16 milliliters apart, a giant distance for something so thin. This proved that their new technique for making bioink worked, and that they could get away with creating a bioink from nothing more than the protein connections produced by the E.coli bacteria.
Once the researchers knew that their new microbial ink worked, they introduced genetically engineered microbes to the mixture. This produced 3D-printed living functional architectures: living material capable of carrying out a massive range of therapeutic applications.
By seeding this new bioink with a cancer-fighting drug called azurin, the researchers discovered that they could ensure the bioink released azurin whenever it detected a chemical called IPTG. These tests showed that the bioink could respond to its environment, actively producing the anticancer drug only when it needed to. This meant that the bioink could be further engineered to effectively control and/or induce cell growth and death, depending on the need of a patient.
Their next step was to see if their new biofilm could be taught to absorb something harmful. For this, the team chose the harmful chemical BPA (bisphenol A), an industrial chemical that has been used to make certain plastics and resins since the 1950s despite being shown to cause harmful effects.
The researchers added new modified cells that, via the same interlinking feature they used to connect to one another, could connect and trap particles of BPA: almost a full 30 percent of the toxin in the text liquid within just 24 hours.
The science is complex, but the outcome is simple and beautiful. Future bioinks will be able to respond to the environment they are inside: such as a human body. There, they can automatically release lifesaving drugs directly to the source of serious conditions.
These new bioinks will also be able to tackle toxins in a patient’s body by binding to those toxins (using part of the same bonding mechanism that holds the bioink together). They will then be able to thereby capture those toxins and remove them from the body.
Best of all, this new 3D-printing process is cost-effective, fast, and incredibly stable when compared to previous methods that have been used. It pushes the boundaries of what such technology can do and, while you probably won’t be able to 3D-print your own anti-cancer therapy any time soon, there might be a day in the not-so-distant future when some of our worst illnesses are combated from by genetically-engineered living structures that defend us from within.