Abstract:
Microbial colonization of surfaces can lead to medical device related infections, promote the spread of infectious and spoilage organisms via contamination of hospital surfaces and food processing equipment, cause damage to equipment in industry and cause damage to buildings and decorations. One approach to reduce contamination is to create micro- or nano- structures on the surface that are less easily colonized by microbes. The aim of this research is 1) to develop a protocol where attachment of test bacterial strain to material surfaces can be imaged allowing surface coverage measurements and 2) to identify surface structures able to prohibit bacterial attachment and growth. Using nanosecond and femtosecond laser etching technology, arrays of test patterns were etched onto the surface of polyurethane (PU) sheets (termed coupons). Different test patterns were produced by pairing the chosen base structure (elongated rectangle) with varying set parameters, such as the structure peak-to-peak distance and laser pulse frequency. The laser etched coupon surfaces were challenged with test bacterial strain Escherichia coli 25922 by immersion in broth culture for 48h at 37oC, 100 rpm shaking. A selection of fluorescent and chromogenic stains and microscopes were trialled for the visualization of attachment to PU, and Coomassie Brilliant Blue R-250 staining followed by visualization using a stereo microscope was chosen for preliminary testing. Imaging of fabricated micropatterns were carried out using Scanning Electron Microscope (SEM). Bacterial attachment to the test coupons was quantified using ImageJ software measurements of surface coverage. Two patterns from scale up experiments showed no reduction in E. coli 25922 adhesion to PU despite the preliminary results showing 46 % and 61 % reduction in surface coverage, respectively. The Sharklet micropattern, and the two variants of this design (Reduced-gap and Enlarged design) showed reduction in surface coverage, demonstrating effective micropattern designs capable of resisting bacterial attachment. Ultimately, the outcomes of this project suggest that while not all structured surfaces are capable of inhibiting bacterial adhesion, it is still possible to attain anti bio-fouling properties through laser-assisted microfabrication method. However, further work and testing for wider range of micropatterns and additional tests on surface characterizations will be needed to better understand factors contributing to the capability of structured surfaces to reduce bacterial adhesion to material surfaces.