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Hydrophobic coatings

The potential benefits of hydrophobic coatings can be used in a wide variety of application areas, such as hydrophobic clothes, anti-fouling coatings, anti-corrosion coatings on different materials such as wood or concrete, hydrophobic paint and even medical coatings for drug delivery or against biofilm formation. Many of these coatings have been developed, at least partially, in the lab. But not all coatings have been put into use successfully outside the lab, so the search for a cheap, multi-functional hydrophobic coating is still on.

Anti-fouling coatings

Surface hydrophobicity could also be beneficial in the antifouling industry, for instance when applied on ships. When marine micro-organisms like algae or pocks adhere to the hull of ships, they form a layer which greatly increases drag in the water. This results in higher fuel costs and increased erosion. To prevent organisms to adhere to the hull of ships, chemical antifouling paints, which often contain copper and tin, are used. A lot of these chemicals eventually end up in the oceans ecosystems accumulating in all trophic levels of marine life and contaminating estuarial silt near shipping routes. Estimates show that in the Netherlands alone, approximately 19 tons of organotin and 30 tons of copper end up in the environment every year.

Biofilm coatings

Although a biofilm is not ideal for all of these coating purposes (imagine a biofilm jacket), an hydrophobic biofilm coating could be applied in fields ranging from anti-fouling coatings on ships, peers and buoys, to coatings used to protect catheters and protheses from pathogenic bacteria. Moreover, with introducing our kill switch and our chaplin coating without living bacteria, a even broader range of applications can be taken into consideration as certain ethicial and safety issues are dealth with.

The main advantage of a biofilm coating is that it is very cheap, applying it requires no technical expertise and it is more environmentally friendly than certain chemical coatings. Next to that, biofilms can grow on a wide variety of surfaces: They are found on your teeth, in catheters, in plumbing, in water cleaning installations (beneficial), in bioreactors and, if you're one of those students, on your bathroom floor (blech).

So far there have been coatings with biological substances, but bacteria where only used to produce the coating material. In our project the bacteria will form a biofilm on the desired surface, which will then function as a coating. Our bacteria therefore execute the coating process themselves, which could save a lot of effort. In the case of using chaplins as a material for hydrophobic coating, the biofilm is also used to orient and anchor the proteins in the right way. As chaplins are amphipathic, the orientation in their pure form is determined by the properties of the surface they coat as well: Using a biofilm to structure them the right way is an easy and smart solution that helps us to get around some problems of using the chaplins in their pure form as a coating.

Medical coatings

Because of their surface modifying abilities, hydrophobic biofilms of non- pathogenic bacteria might be used to prevent pathogenic biofilms from adhering to implants or catheters. Keeping in mind that growing a biofilm, even our good biofilm coating, in a catheter or on prothesis can give serious medical problems (shock, inflammation) we make use of a kill switch to kill off living bacteria. Bacillus subtilis however, is not pathogenic, and we could also make use of some inhabitants of our body like Lactococcusto form the hydrophobic biofilm. The principle via which we form a Bacillus biofilm coating is of course applicable to a number of hosts. Next to that, using model hosts like Bacillus to produce chaplins also enables us to genetically modify the chaplins. That way they can be used to further functionalize the coating for drug delivery, cell adhesion or anti-bacterial activity.

Concrete protection

As the team of Newcastle enters this years competition with a B. subtilis machine that fixes cracks in concrete, preventing corrosion and water or frost induced damage to buildings, roads or monuments, we have a great addition to their project (or the other way around ;) ). Hydrophobic coatings are used to protect concrete structures, especially when reinforced with metal bars, from corrosion damage. Our B. subtilis biofilm would be able to do the same thing by filling up cracks and reducing water inflow by chaplin production: Thus preventing damage.

A combination of both projects would of course create an even more awesome bacteria, as the crack filling bacteria repel the water and ice that is damaging concrete structures.