Scientists have for years been investigating methods to develop means in which to create living materials for a wide range of applications. Authentic tissue engineering. Although it is true that great strides had been made, achieving any three-dimensional structure on demand did not seem an easy task. The new step taken by the signatories of the article has been the use of the versatile Escherichia coli to produce a product that can be used as a base and then be implemented in 3D printers, as if it were any ink . Almost nothing, because it is far from a simple task.
The first steps were framed in the bioengineering of bacteria, whose objective here was to produce living nanofibers. The next step would be to group these thin fibers, and then add other components in order to turn it into a live ink compatible with conventional 3D printers . When they saw that the process was viable, the team turned to bioengineering with other bacteria to produce other types of living nanofibers that they added to their ink, which they have called “microbial ink.”
The research has been published in the journal Nature Communications, under the title Programmable microbial ink for 3D printing of living materials produced from genetically engineered protein nanofibers . The work explains in detail the strategy that the authors have followed in order to manufacture this innovative biological ink. The final product had to have a consistency similar to toothpaste: firm enough to hold its shape at rest but with the necessary pour point (no more) to flow under pressure through the printer nozzle : “A printable biotin it requires a viscosity low enough to facilitate extrusion, but high enough to retain its shape after printing. ” Extrusion is the process by which a mass of metal or other materials is passed through a hole or other cavities in order to spin or flatten it. Neel Joshi, co-author of the study, stated that “hydrogels flow by shear, decreasing their viscosity with increasing shear force.”
To achieve the desired viscoelasticity, they relied on a genetically programmed crosslinking strategy inspired by fibrin, a protein involved in blood clotting. Fibrin is a kind of glue between platelets when they are exposed to a wound. Fibrin polymerization is driven in part by the interaction between two domains at the ends of the alpha chain (“knob” domain) and the gamma chain (“hole” domain). They are joined by the so-called “button- into-hole” (knob into hole). “Our microbial ink design reuses this bonding interaction between the alpha and gamma domains, that is, the button-eyelet assembly , to introduce non-covalent cross-links between the nanofibers to improve mechanical consistency while remaining shear thinning properties. ”. To achieve this, they used a technique that they developed in their laboratory and published in 2014: Biofilm Integrated Nanofiber Display (BIND).
“By introducing genetically programmed E. coli cells into the microbial ink, we achieved 3D printing of therapeutic living material, sequestration living material, and self-regulating living material ,” continues Joshi. One of these impressions was a material that secreted azurine. Azurine is a bacterial cuproprotein that blocks the cell proliferation of breast cancer and induces apoptosis (programmed cell death) through the mitochondrial pathway, thus opening an interesting application in chemotherapy for the treatment of breast cancer. Another of the team’s creations has been a living material capable of sequestering bisphenol A, without the help of other chemicals. Bisphenol A (BPA) is a toxin that has entered the environment. BPA is a toxic organic compound and was sequestered by printed material up to 27% after 24 hours.
The applications of this revolutionary technology go far beyond making grids, squares, circles or cones (see attached image). The researchers think that the concept can lead to an ink that is self-manufactured under certain conditions. By means of this incipient microbe engineering technique, they could be motivated to produce copies of themselves, that is, literally grow the ink in flasks . Along these lines, the ink could be used to print renewable construction materials that would not only grow by themselves but would repair themselves if they suffered any kind of damage, as if it were a starfish or the very T-3000 of the Mythical Terminator film saga. Therefore, alongside the ability to print with living cells can come a veritable wave of exciting opportunities of all kinds, among which are biomedical applications in the manufacture of drugs or the elimination of toxins in the air. They would also be ideal materials to build self-sufficient constructions on Earth, the Moon or Mars . In short, it would be an ideal option for constructions in other worlds where the transport of raw materials is limited or practically impossible. The constructions would be done in situ , with extremely limited resources, only what is fair and necessary. A future in which astronauts would carry microbial biotin with them to 3D print the materials and structures they would need. Space travelers with jars and printers. Nothing more. Maybe in the future we will see printers on the Moon.
