23 July 2012
Bacterial biofilm is created when bacteria grow adhered to a surface and are surrounded by a matrix that they themselves produce and which makes them more resistant. “Bacteria,” according to the head researcher Jaione Valle-Turrillas, “stick to any surface; it can be the skin, internal organs, surfaces of materials, etc. and they produce this biofilm, a kind of film that makes them more resistant to antibiotic treatments, disinfectants, etc.” Biofilms can be found in nature (bacteria adhered to the surfaces of stones in rivers), in our own bodies (intestinal and buccal flora), in filters and pipes, in water tanks, on farms (milking equipment) and in the clinical ambit (prostheses, surgical catheters), etc.
“Thanks to DLIP [Direct Laser Interference Patterning] technology, a surface is interfered with and modified using different laser beams on a nanometric scale,” explains Jaione Valle. “You can create different patterns and drawings, of different periodicity, from nanometres to micra. We’ve already tested different surfaces and have found a material and a pattern that will stop the bacteria from sticking to the surface; it does not eliminate them completely, but the reduction is between 65 and 70%.”
First of all, the surface is modified by means of laser and then the bacteria are applied to see how they produce the biofilm and in what quantity. Various materials have been used during the tests, and it has been seen how the number of bacteria and the production of biofilm diminish according to bacteria type and type of structure applied to the surface.
To quantify the reduction in the number of bacteria and the extent to which they remain adhered to the nanostructured surface, the researchers used a reagent (Alamar Blue), which emits fluorescence when it comes into contact with live bacteria. “This reaction is measured in a fluorometer so that the more bacteria there are, the greater the fluorescence that is produced,” points out the researcher. The problem is that this technique cannot differentiate when the adhesion differences are small. That is why we are now using another method: we collect all the bacteria that have stuck to the surface, we sow them in a culture medium and count the number of colonies; it’s more laborious, but it’s also much more reliable.”