A bioinspired approach to the generation of novel antimicrobial materials.

摘要

Advancements in particle beam microscopy have allowed scientists to discover a wealth of surface architectures with nanoscale dimensions, many of which endow the surfaces with fascinating properties. Investigations of such surfaces have revealed some exciting physical phenomena, ranging from complex interactions with light such as brilliant iridescent colors resulting from diffraction and interference to water repelling self-cleaning superhydrophobic surfaces. Interestingly, the biological world, especially that of insects, has perhaps contributed the greatest number of these discoveries and will likely continue to do so as long as scientists entertain the idea that nature still has a vast collection of lessons to teach us. Examples of such phenomena include the structurally derived colors displayed by Chrysiridia rhipheus (Madagascan sunset moth), the anti-reflective and self-cleaning wings of Psaltoda claripennis (Clanger cicada), along with its more recent discovery of mechanically induced bactericidal activity. The implications of such a discovery are truly revolutionary as it is the first time that surface topography has been linked to microbial death. With this discovery a new defensive strategy against biofilm derived pathogenesis and related problems has arrived and must be further investigated for a more thorough understanding. It's a generally accepted notion that fungi much like bacteria can form complex protective biofilms and are undoubtedly a source of pathogenesis. For example C. albicans is the fourth most frequent organism found in the blood of hospitalized patients. While bacterial infections have been given much attention, less has been given to fungal biofilms though they are a major source of nosocomial infections attributed in part to adhesion to invasive devices such as catheters, cardiac pacemakers, prosthetic heart valves etc. S. cerevisiae, a generally non-pathogenic yeast, has been proposed as a model for fungal biofilm formation with similar behaviors but far more genetic tools available. In the present work I investigate the effects that the nano-structured wings of our local Dog Day cicada Tibicen tibicen have on adhered S. cerevisiae to assess for antifungal activity. Resembling that of the bactericidal activity, my study concludes antifungal activity of a cell rupturing mechanical nature attributed to the nano-topography of the Dog Day cicada wing. Following this discovery I utilize nano-sphere lithography (NSL) to fabricate analogous nanostructures as well as proportionally smaller and larger nanostructures in common synthetic polymers to be tested for translation of function. Studies with E. coli and S. cerevisiae reveal the overlooked but fundamentally important mechanical properties of nano-structures as they apply to mechanical microbicidal functionality. In addition to biocidal activity studies, I also demonstrate the remarkable anti-adhesive nature of a particular scale nano-patterned surface relative to flat surfaces of analogous chemistry.