In this work, we have investigated the effect of nanostructured surfaces on the attachment and viability of two bacterial
species of medical relevance. Surfaces having squares, channels and dots in the nano size range with intermittent
hydrophobicity and hydrophilicity showed complex effects on both live and dead E. coli cells. Nevertheless the
behaviour of S. aureus was found to be less modulated by the surface properties. The square structures had promising
repellent effect on both live and dead E. coli species while S. aureus populated these surfaces very well. On dot
nanostructures the population by E. coli was considerably higher than on the surrounding spaces while the distribution of
S. aureus cells remained uniform on both structured and unstructured areas. When the bacteria were applied to surfaces
with channels, live E. coli cells showed a very interesting fluctuation in function depending on the width of the channels
but this fluctuation was not observed in case of dead cells. Because of its spherical form, lacking flagellae and production
of extracellular substances, S. aureus adhered to this structure more evenly and no fluctuation was observed. Strain
specific bacterial physiology and reactivity to these surfaces may possibly also be a factor in influencing the interaction.
These initial results contribute to the purposeful design of species-specific pro- or anti-bacterial surfaces for the use of
lab-on-a-chip devices and various types of medical devices.
Self-assembling polymers have recently attracted significant scientific interest, since they spontaneously generate highly
ordered structures with high resolution precision, and provide simple, parallel, and cost-effective processes for
nanofabrication. Such systems can be achieved with block copolymers which, when produced as thin films, offer great
potential as lithographic templates for the fabrication of photonic band-gap materials, ultrahigh-density nanodots or
nanowire arrays, memory and capacitor devices, and nano-patterned substrates for biosensors. Although self-assembling
block copolymers can form a variety of surface topographies at the nm scale, like spheres, cylinders, and lamellae, their
structural steering through the annealing conditions has in many cases not been fully investigated. In the present
investigation optimum production conditions for the preparation of nanostructures from poly(styrene)-block-poly(MMA)
diblock copolymers have been established to enable the production of surfaces as thin films (<40 nm) on spin-coated
silicon wafers either with parallel cylindrical structures or with vertical cylinders. The resulting self-assembling
structures were then evaluated by atomic force microscopy. The obtained nanostructured polymers were then incubated
with two microbial species, the gram negative E. coli and the gram positive S. aureus to assess their behaviour. The
patterns of the thin film surfaces affected the bacterial attachment. Such self assembly processes can be used to create
surfaces acting as bacterial attractants or repellents.
In this work, we have investigated the effect of changes in the properties of planar surfaces on the attachment and
viability of two bacterial species of medical relevance. Polydimethylsiloxane (PDMS) surfaces showed a promising
repellent effect on both live and dead E. coli and S. aureus cells. When the hydrophilicity of the PDMS was increased by
UV-radiation this repellent effect disappeared. On gold surfaces coated with hydrophobic and hydrophilic self assembled
monolayers (SAM) very few bacterial cells were found, compared to plain gold. Moreover, the behaviour of E. coli and
S. aureus was modulated differently by the surface properties. Thus, while S. aureus cells lived in slimy conglomerates
and colonised the surfaces at the same high density from both diluted and concentrated solutions, in contrast, single cells
of E. coli colonised the surfaces at lower densities from diluted solutions. Also, dead E. coli cells were easily washed off from most surfaces, whilst dead S. aureus cells were frequently found attached to the surfaces, which may also be
explained by its occurrence in conglomerates. Strain specific bacterial physiology and reactivity to these surfaces may
possibly also be a factor in influencing the interaction. These initial results contribute to the purposeful design of species-specific
pro- or anti-bacterial surfaces for the use of lab-on-a-chip devices and medical devices.
Many bacterial species are able to colonize the surfaces of biomedical tools or devices and form biofilms creating a
source of infection and other deleterious effects. Biofilms constitute environments in which bacteria grow and are
protected from the host's immune system and antimicrobial medications. The bacterial adhesion, which is an important
and first step in biofilm formation, is influenced by several physico-chemical and topographical factors at the interfaces
between the bacterial cell and the surface. Therefore, the mechanism of initial adhesion needs to be investigated to better
understand the events of anchorage and film formation as bacteria colonise surfaces. In this work, atomic force
microscopy (AFM) in the tapping mode of imaging has been employed to investigate the attachment of bacteria onto a
structured surface patterned with different hydrophilic and hydrophobic areas. The interactions of Escherichia coli and
Staphylococcus aureus with these structures were also monitored by fluorescence microscopy. AFM was successfully
employed for the study of the cell responses to both nanotopography and the surface chemistry via observation of various
cell functions; including extracellular polymeric substance (EPS) mediated cellular adhesion.
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