Living 3D Bio-ink Shows Potential for Use in Skin Replacement

Living 3D Bio-ink Shows Potential for Use in Skin Replacement

3D printers can be used to create artificial bones with high tensile strength out of inorganic material, but when it comes to printing biological materials that require flexibility, there are many challenges. However, a team of researchers have made a breakthrough and have successfully developed a living ink that can be used to create a flexible material that can be printed into complex three-dimensional geometries.

The living bio-ink contains live bacteria that survive the printing process and remain active in the printed materials. The bacteria are capable of breaking down toxins, can synthesize vitamins, and create biologically useful bacterial cellulose. Scaffolds containing bacterial cellulose is particularly useful for treating skin wounds. The material contains a lot of water, is soothing on the skin, and is not rejected.

Creating 3D structures flexible enough to be beneficial is difficult, especially with 3D printing. One of the problems that had to be overcome by the researchers is how to add the bacteria to a printable ink. The ink needed to have the right properties to allow it to be used in the printers, and achieving the right thickness was a major challenge. Too thick and the bacteria would be frozen in place. Too thin, and the ink would not be suitable for printing.

The printed material needed to allow the bacteria to be mobile, as strands of bacterial cellulose are only created when the bacteria move. The ink also needed to include a variety of nutrients to keep the bacteria alive and ensure they continued to produce cellulose.

First author of the paper, Manuel Schaffner, said “We have developed a 3D printing platform that enables additive manufacturing of complex 3D living architectures of bacteria-laden hydrogels with full localization and concentration control of bacteria.”

The researchers named their creation Flink, short for functional living ink. The researchers used two strains of bacteria in their bio-ink – Pseudomonas putida and Acetobacter xylinum, although other bacteria could easily be used. Pseudomonas putida can degrade phenol, while Acetobacter xylinum was used to form bacterial cellulose scaffolds in situ.

The printed material is flexible, can be used to coat biomedical devices to prevent rejection, and also to create scaffolds for skin replacement. Flink is cheap to produce and it is straightforward to culture bacteria for use in the ink. Different bacteria can be incorporated into Flink to give it different biomedical properties.

To demonstrate how the material could be printed for use as skin grafts, the researchers printed the material on a dolls head, with the material exactly matching the contours of the dolls face without the formation of any pockets or wrinkles. The researchers believe their printing technique can easily be scaled up for printing skin grafts for use on human patients, and that the material can be used for a wide range of biomedical purposes.

“We envision this versatile bacteria-printing platform to be used for the additive manufacturing of a new generation of biologically generated functional materials,” said Schaffner.

The study – 3D printing of bacteria into functional complex materials – was recently published in Science Advances.

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