Antibacterial coating
11/23/12

How can steel manufacturers and biologists work together? Among other things, they can cover steel with an antibacterial coating. The Biocoat programme, which began in 2006, has recently been rewarded with several publications (1) and patent registrations. This has led to a technological innovation platform: Symbiose Biomaterials. Why? To expand beyond the steel sector and extend Biocoat’s assets to other media and new applications.

It was with many questions in mind that Professor Joseph Martial, director of the University of Liège’s ‘biology and molecular genetics’ research unit at the time, went to a meeting in 2004 concerning the redeployment of Liège’s steel industry. Up until then, biologists and steel manufacturers had never met and knew absolutely nothing about each other. But among his researchers, Professor Martial had a team in ULg’s GIGA–R Biology and Molecular Genetics unit led by Cécile Van De Weerdt, now a project leader. And this is who Joseph Martial turned to after the meeting: “And what if we put proteins on steel?” And so began a good deal of spadework for Cécile Van De Weerdt. “I realised”, she remembers, “that there were a lot of publications in the United States about molecular biomimetics. These studies observed how nature formed materials, structures adapted to particular environments. Of course, the goal was to succeed in imitating this way of doing things. If you take a closer look, you'll find that there are proteins that assemble inorganic material to create original structures. A good example of this know-how is mother-of-pearl, which is a composite endowed with exceptional properties as yet unequalled in synthetic composites. The proteins/materials association therefore made sense. Even more so considering that nature constructs materials using foundation stones that aren't toxic, during gentle procedures, i.e. at room temperature, most often in an aqueous solution, without emitting any pollutants... The dream of every industrialist, you could say.”

The steel company Arcelor (not yet Mittal at the time) did indeed show an interest in these possibilities. Biologists and steel manufacturers then began to meet to get to know each other, with Catherine Archambeau, research engineer at Arcelor, taking responsibility for the project on the industrial side.  The aim of these preliminary meetings was also to determine whether there was a real industrial need which the scientists could meet. Several possibilities came to light and several functionalities were researched, but it was antibacterial coating that was chosen. The Walloon Region subsequently supported the project, appreciating the fact that two of Wallonia’s strongest areas of activity, an old one (the steel industry) and an emerging one (biotechnologies), were joining forces.  A PPP (public-private partnership), called Biocoat, was created in January 2006. Two other entities from the University of Liège then joined the programme: first of all, the laboratory of Professor Jérôme, and in particular Christophe Detrembleur (FNRS senior research associate, Center for Education and Research on Macromolecules); followed by that of Professor Anne-Sophie Duwez (Nanochemistry and Molecular Systems).  Why? To create an innovative coating on steel with antibacterial properties by associating biomolecules and polymers, while implementing the greenest technologies possible and respecting the technical and economic constraints dictated by Arcelor. To put it plainly, the coating had to be made in a minimum number of steps from aqueous based solutions.

mouleMussels and batrachians

Nature provided the scientists with models on two levels: for the glue and the antibacterial substance. The choice of glue was quickly resolved owing to the great number of studies on this subject. Marine molluscs, especially the mussel, secrete a DOPA-based adhesive which allows it to stick to almost any kind of surface; Christophe Detrembleur’s team took this active ingredient and inserted it into polymers. They tested different architectures until they found the best “glue”, i.e. the anchoring layer that would allow them to bind the antibacterial coating to steel.

(1) Among the most recent:

Sustainable and bio-inspired chemistry for robust antibacterial activity of stainless steel;
Faure, Emilie et al. In Journal of Materials Chemistry 2011, 21, 7901-7904.

A green and bio-inspired process to afford durable antibiofilm properties to stainless steel ; Faure, Emilie et al. In Biofouling 2012, 28, 719-728.

Antibacterial polyelectrolyte micelles for coating stainless steel ; Falentin Céline et al. In Langmuir 2012, 28, 7233-7241.

Functional nanogels as platforms for imparting antibacterial, antibiofilm, and antiadhesion activities to stainless steel ; Faure, Emilie et al. In Advanced Functional Materials 2012  DOI: 10.1002/adfm.201201106.

Catechols as versatile platforms in polymer chemistry ; Faure, Emilie et al. In Progress in Polymer Science 2012, http://dx.doi.org/10.1016/j.progpolymsci.2012.06.004.

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