Probing topographical influences on biofilm formation using dynamic-mask multiphoton lithography

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Fox, Michelle Ann

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It has only been within recent decades that the complexity and heterogeneity of the biofilm mode of bacterial existence has been widely appreciated. Biofilms have persisted for billions of years as social communities of cells aggregated and attached on surfaces, and today they are both necessary and harmful within the human body and our surrounding environment. They show extremely high antibiotic resistance relative to planktonic cells and are sources of persistent infections. Biofilms are also the most common cause of failure for indwelling biomedical devices and implants. As a result, research efforts and commercial developments are focusing on creating better biomaterials that prevent bacterial attachment to surfaces leading to biofilm formation. While chemical methods to combat bacterial infections have been around for over a century in the form of antimicrobials, relatively little is known about how topographical methods can prevent bacterial attachment to surfaces. The reason for this is that micro- and nano-scale fabrication technologies (which are needed to produce topographies on size scales that might be expected to influence bacterial attachment) are fairly recent developments. In this thesis work, microscale topographies were developed for probing and influencing bacterial attachment to surfaces using dynamic-mask multiphoton lithography. Multiphoton lithography is an inherently three-dimensional fabrication technique. When combined with the dynamic-mask-based technology developed in the Shear laboratory, it allows for rapid prototyping of 3D structures of arbitrary complexity with submicron resolution in the radial dimension.
A variety of topographical approaches for influencing bacterial attachment of Pseudomonas aeruginosa cells were explored within this work. P. aeruginosa was selected as a model organism for biofilm formation and because it is commonly isolated from infections associated with biomedical implant devices. Topographical approaches included the design of topographies based on microscale surfaces of naturally-antifouling leaves and mathematical functions, pillars, and surfaces containing various sizes and geometries of holes. Challenges relating to an imaging artifact caused by light scattering induced by the surfaces shed light on issues associated with assessing bacterial attachment levels on microscale topographical surfaces. Finally, future directions for this work are presented with ideas that extend into the nanoscale regime.




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