3D Bio-Printed Graphene

The most important epistemological change in synthetic biology as a branch of life sciences is the understanding of life gained by using it in implementing our projects. The technology presented in this article explores the phenomenon of bioleaching discovered in the late 1990s and whose research continues to enrich the fields of biology and nanotechnology. It is a new 3D printing technique that ensures the transformation of inorganic matter properties by living organisms during a process called microconstruction.

The Quest for Graphene

Researchers from the Bionanoscience Department of Delft University of Technology (TU Delft) in the Netherlands created a 3D printing process that uses bacteria to produce a material approximating graphene. Keep in mind that graphene is a relatively new material that was extracted for the first time in 2004 by Andre Geim from the Department of Physics at the University of Manchester. Renowned for its many physicochemical properties, this material is the object of several major technological and theoretical studies (fundamental physics) in order to better understand it and guide its industrial development, mainly by reducing its very high production cost. Graphene is best known for its lightness, ductility, energy storage capabilities, conductivity, mechanical strength and many other features that lead to many applications, from electronics and photonics to medicine.

Discovery of graphene

Potential of Graphene Oxide

Graphene oxide is currently the most coveted compound used by scientists for the production of graphene. Its chemical reduction represents the most favoured approach to transform it into graphene flakes. Also, graphene oxide is itself valued for its conductivity properties. The Delft TU team, through biotransformation, successfully converted graphene oxide into a reduced compound that approximates graphene. Their study entitled “A Straightforward Approach for 3D Bacterial Printing” was published on February 22, 2017, in the Journal of the American Chemical Society. Co-writers of the study were researchers Benjamin A. E. Lehner, Dominik T. Schmieden and Anne S. Meyer. In this article, the team members detail the three main stages of bioproduction printing of reduced graphene oxide and explain the potential of their method in the production of new materials. Of course, bacteria are frequently used in the synthesis of inorganic materials such as amyloid adhesives, and in the production of bioplastics and mother-of-pearl. Yet the method of Delft TU’s research team is a breakthrough, as it integrates 3D printing in its process.

Printing Biosynthesized Reduced Graphene Oxide

A culture of Escherichia coli (E. coli)—intestinal bacteria found in mammals—placed on graphene oxide sheets can reduce this compound by removing oxygen atoms from the material through metabolism. Based on this, the researchers thought of using E. Coli in 3D bio-printing techniques to produce small graphene constructions. Low-cost printers used for the additive manufacture of non-biological materials such as stereolithography or selective laser sintering, use high temperature, which kills bacteria. However, bio-printing machines designed for applications in tissue engineering and medicine are very expensive. Faced with this dilemma, the researchers chose to create their own printer by modifying a commercial machine and drawing inspiration from biological printing techniques. The changes they made improved the resolution of the machine. The printer’s extruder and print head were replaced with pipettes that transport bacteria at room temperature and allow three-dimensional deposits.

As for the printing technique, the team used a mix of alginate gel and E. coli as bio-ink, which solidifies during the printing process. The alginate molecules form a biocompatible medium. The ink is deposited on a calcium chloride-treated printing surface, which causes the gel to solidify without killing the bacteria. In order to optimize the bio-ink and avoid having the solution gel inside the pipettes, the researchers tested several concentrations of alginate and calcium ions. The final goal would be to use the gel to print a type of proteobacteria, called Shewanella oneidensis, in order to reduce the graphene oxide according to a specific pattern, and so adjust its properties. Since being isolated by Kenneth H. Nealson in 1988, Shewanella oneidensis is used in the biosynthesis of metallic nanomaterials.