Title

MICROTOPOGRAPHIC PATTERNS AFFECT BACTERIAL ADHESION AND BIOFILM FORMATION ON POLY(DIMETHYLSILOXANE)

Date of Award

January 2015

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Biomedical and Chemical Engineering

Advisor(s)

Dacheng Ren

Second Advisor

Liviu Movileanu

Keywords

Antibiotics, Bacterial biofilm, Bio-manufacturing, Biomaterials, Medical devices, Patterned surfaces

Subject Categories

Engineering

Abstract

Bacterial biofilms are sessile microbial communities that cause serious problems, such as antibiotic resistant chronic infections in humans, and persistent biofouling of engineering facilities. Biofilm formation is initiated by bacterial adhesion to a surface followed by the formation of microcolonies and further development of heterogeneous structures with water channels between cell clusters. The mechanism of biofilm structural heterogeneity and the bacterial genes involve in structural organization are still poorly understood. Nevertheless, once microbes adhere to a surface and form biofilm on it, they are up to 10-1,000 times more resistant to antimicrobial agents than their free-swimming counterparts. It is well accepted that biofilm formation involves multicellular behaviors, associated with major changes in microbial gene expression and protein synthesis. These changes are influenced by many environmental factors such as surface hydrophobicity, topography, chemistry, and charge. To better understand bacteria-surface interactions and to develop more effective biofilm control, we created poly(dimethylsiloxane) (PDMS) surfaces with micrometer scale topography and characterized bacterial adhesion and biofilm formation on these surfaces. It was found that the wild-type Pseudomonas aeruginosa PA14 cells preferred to align perpendicularly to the orientation of line patterns, while its fliC and pilB mutants did not show such bias and oriented randomly like observed for the wild-type PA14 cells on flat surfaces. Besides, cell clusters on the protruding line patterns were found to increase with the pattern width (from 5 to 20 (mu)m). Moreover, the PDMS surfaces with 10 (mu)m tall hexagon features (15 (mu)m side length and 2 (mu)m inter-pattern distance) reduced Escherichia coli biofilm formation by 70% compared to flat PDMS surfaces. The effects of surface topography on bacterial conjugation were also investigated. These results provided new information about the effects of surface topography on bacterial adhesion and biofilm physiology, which can help develop better control methods.

Keywords: biofilm formation, cell attachment, bacterial-surface interaction, conjugation, cluster formation, PDMS surfaces, surface topography.

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