Bacterial biofouling is a huge problem within food production industries (food processing surfaces, processing equipments). The adhesion of bacteria to a surface is given by a combination of factors such as chemical composition, surface topography, mechanical properties and environmental conditions. Among them, surface topography is the most important parameter to trigger cell adhesion. Therefore, one method to prevent bacterial biofouling would be to modify the topographical structure of the surface. There are different opinions on how surface characteristics affect bacterial adhesion. Some reports have shown a positive correlation between adhesion and increased surface roughness while others reported no correlation at all.
In this study, we investigate how micro/nano-scale topographies impact bacterial surface attachment. Gram-negative bacterial strain Pseudomonas aeruginosa was exposed to sets of polyethylene terephthalate (PET) substrates with submicron-sized structures. The PET substrates were prepared by Direct Laser Interference Patterning (DLIP). The shape and dimensions of the interference patterns can be modified by controlling the geometrical configuration and the number of laser beams. The periodicity of the structure was chosen to be similar or smaller than the cell size of P. aeruginosa bacteria which has a length between 1.5 – 3 µm and a diameter between 0.5 – 0.8 µm. Line and cross-like patterns were selected for the experiment, with a periodicity of 0.7 µm and average depth of 0.85 µm.
The results indicated that the smooth surface had no colony forming units (CFU) after 48 h at 28ºC and 37ºC, but increased only after 96 h at 37ºC. The line pattern had almost no CFU attachment at 37ºC, the number of cells were near 0 during 48 h and 96 h. However a high number of CFU were found at 28ºC after 96 h of incubation, which means there was attachment. The cross pattern had no CFU at all after 48 h, at both temperatures. It showed no attachment at all at 28ºC and a high number of adherents CFU at 37ºC after 96 h of incubation. In summary, these preliminary results showed no attachment variations between the smooth and cross pattern surfaces at both temperatures, while the line pattern surface presented no cell adhesion at 37ºC and attachment at 28ºC after 96 h. More studies are presently being done to explain the attachment differences found between the line and cross pattern.