Role of Trapped Air in the Attachment of Staphylococcus aureus on Superhydrophobic Silicone Elastomer Surfaces Textured by a Femtosecond Laser

Surface texturing
is an easy way to control wettability as well
as bacterial adhesion. Air trapped in the surface texture of an immersed
sample was often proposed as the origin of the low adhesion of bacteria
to surfaces showing superhydrophobic properties. In this work, we
identified two sets of femtosecond laser processing parameters that
led to extreme superhydrophobic textures on a silicone elastomer but
showed opposite behavior against Staphylococcus aureus (S. aureus, ATCC 25923) over a short incubation times (6 h). The
main difference from most of the previous studies was that the air
trapping was not evaluated from the extrapolation of the results of
the classical sessile drop technique but from the drop rebound and
Wilhelmy plate method. Additionally, all wetting tests were performed
with bacteria culture medium and at 37 °C in the case of the
Wilhelmy plate method. Following this approach, we were able to study
the formation of the liquid/silicone interface and the associated
air trapping for immersed samples that is, by far, most representative
of the cell culture conditions than those associated with the sessile
drop technique. Finally, the conversion of these superhydrophobic
coatings into superhydrophilic ones revealed that air trapping is
not a necessary condition to avoid Staphylococcus aureus retention on one of these two textured surfaces at short incubation
times.