Cambridge, Mass - Juillet 30, 2012 - Des biofilms pourraient bientôt ne plus être nécessaires sur des supports solides dans les hôpitaux. En effet, une équipe de chercheurs de Harvard a mis au point un moyen habile pour éviter que des communautés bactériennes gênantes ne se forment jamais sur une surface. Les biofilms sont appliqués sur à peu près tout, des tuyaux en cuivre aux coques de navires en acier en passant par des cathéters de verre. Les revêtements visqueux sont plus qu’une simple nuisance, car ils réduisent l’efficacité énergétique, contaminent l’eau et les vivres, et surtout dans les installations médicales, provoquent des infections persistantes. Même les cavités dans les dents sont le résultat fâcheux de colonies bactériennes.

Dans une étude publiée dans les "Proceedings of the National Academy of Sciences (PNAS)", les coauteurs Joanna Aizenberg, Alexander Epstein, et Tak-sing Wong ont recouvert des surfaces solides avec un film liquide immobilisé pour tromper les bactéries leur faisant croire qu’elles n’avaient aucun endroit pour se fixer et à croître.

"Les gens ont essayé toutes sortes de choses pour décourager l’accumulation de biofilms comme les surfaces texturées, les revêtements chimiques et les antibiotiques, par exemple," assure Joanna Aizenberg, professeur de science des matériaux à la Harvard School of Engineering and Applied Sciences (SEAS). "Dans tous ces cas, les solutions sont de courte durée, au mieux. Les traitements de surface s’estompent, se couvrent de poussière, ou les bactéries même déposent leurs propres revêtements au-dessus du revêtement destiné à les prévenir. En fin de compte, les bactéries parviennent à s’établir et à croître sur à peu près n’importe quelle surface solide"

Adoptant une approche complètement différente, les chercheurs ont utilisé leur technique développée récemment, baptisée SLIPS (Slippery-Liquid-Infused Porous Surfaces : Surfaces Poreuses poreuses) pour créer efficacement une surface hybride qui est lisse et glissante à cause de la couche de liquide qui est immobilisée sur elle.

First described in the September 22, 2011, issue of the journal Nature, the super-slippery surfaces have been shown to repel both water- and oil-based liquids and even prevent ice or frost from forming.

The SLIPS technology for preventing biofilm formation as compared to a Teflon coated surface. (Photo courtesy of Joanna Aizenberg and Tak-Sing Wong.)

“By creating a liquid-infused structured surface, we deprive bacteria of the static interface they need to get a grip and grow together into biofilms,” says Epstein, a recent Ph.D. graduate who worked in Aizenberg’s lab at the time of the study.

“In essence, we turned a once bacteria-friendly solid surface into a liquid one. As a result, biofilms cannot cling to the material, and even if they do form, they easily ‘slip’ off under mild flow conditions,” adds Wong, a researcher at SEAS and a Croucher Foundation Postdoctoral Fellow at the Wyss Institute.

Aizenberg and her collaborators reported that SLIPS reduced by 96–99% the formation of three of the most notorious, disease-causing biofilms—Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus—over a 7-day period.

The technology works in both a static environment and under flow, or natural conditions, making it ideally suited for coating implanted medical devices that interact with bodily fluids. The coated surfaces can also combat bacterial growth in environments with extreme pH levels, intense ultraviolet light, and high salinity.

SLIPS is also nontoxic, readily scalable, and—most importantly—self-cleaning, needing nothing more than gravity or a gentle flow of liquid to stay unsoiled. As previously demonstrated with a wide variety of liquids and solids, including blood, oil, and ice, everything seems to slip off surfaces treated with the technology.

The word "SLIPS" is coated with the SLIPS technology to show its ability to repel liquids and solids and even prevent ice or frost from forming. The slippery discovery has now been shown to prevent more than 99% of harmful bacterial slime from forming on surfaces. (Image courtesy of Joanna Aizenberg, Rebecca Belisle, and Tak-Sing Wong.)

To date, this may be the first successful test of a nontoxic synthetic surface that can almost completely prevent the formation of biofilms over an extended period of time. The approach may find application in medical, industrial, and consumer products and settings.

In future studies, the researchers aim to better understand the mechanisms involved in preventing biofilms. In particular, they are interested in whether any bacteria transiently attach to the interface and then slip off, if they just float above the surface, or if any individuals can remain loosely attached.

“Biofilms have been amazing at outsmarting us. And even when we can attack them, we often make the situation worse with toxins or chemicals. With some very cool, nature-inspired design tricks we are excited about the possibility that biofilms may have finally met their match,” concludes Aizenberg.

Aizenberg and Epstein’s coauthors included Rebecca A. Belisle, research fellow at SEAS, and Emily Marie Boggs ’13, an undergraduate biomedical engineering concentrator at Harvard College. The authors acknowledge support from the Department of Defense Office of Naval Research ; the Croucher Foundation ; and the Wyss Institute for Biologically Inspired Engineering at Harvard University.

CONTACT :

Michael Patrick Rutter
(617) 496-3815
mrutter@seas.harvard.edu

 http://www.seas.harvard.edu/news-events/press-releases/biofilms-may-no-longer-have-a-place-to-stand