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Title: Novel Biophysical Techniques for Monitoring the Development and Stability of Microbial Biofilms.
Author: Schofield, Amy Louisa
ISNI:       0000 0001 3556 5237
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2007
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Quartz crystal microbalance with dissipation monitoring (QCM-D) was used to continuously monitor cell attachment and growth ofStreptococcus lIIutans (+1-1 % (w/v) sucrose) and Candida albicans (+1-10 % (v/v) horse serum) as biofilms within an overnight period of approximately 20 h. S. 11I11tans biofilms generated using a 'continuous flow' method had a greater mass and were more dissipative (more viscoelastic) than those established using an 'attach and flow' strategy with or without 1% sucrose. Biofilms of C. albieans grown with 10 % horse serum had a greater mass and were more dissipative than those grown without the addition of horse serum. Cell numbers (as colony forming units, c.f.u.) in QCM-D derived biofilms after a 2-h attachment phase and during a -20-h growth period could be related to frequency (f) changes and these increased after growth of S. lIIutans and C. albicans. The energy losses displayed by the increases in the dissipative factor (D) indicated an increase in 'softness' of the attached cells. The ratio of D/f was used to provide information of the way in which viscoelasticity changed per unit mass. For S. 1II11tans flow conditions over the cells on the surface appeared to be important in creating biofilms of a greater complexity and stability and the QCM-D enabled properties of cells during attachment and binding, proliferation and removal to be monitored continuously. The percentage surface coverage on the QCM-D crystals by biofilms was estimated using the surface analysis features of the atomic force microscope and image analysis software. Mean percentage coverage also increased after the growth of these organisms. Mean percentage coverage was also increased after the overnight growth of C. albicans in the presence of horse serum. QCM-D was also used to create in situ a Zetag® 17 nm diameter silica nanoparticulate surface and a silvernanoparticulate surface (AgNPs). The influence of the Zetag 1silica nanoparticulate surface was assessed in terms of the responses in f and D on the growth of S. 11I11tans and C. albicans as biofilms. Biofilms of S. 1II11tans had a reduced mass and viscoelasticity when grown on this modified surface and also showed increased variability in terms of their complexity and stability as shown by the D/f ratio. Biofilms of C. albicans showed a reduced level of viscoelasticity as indicated by a reduced D factor and reduced complexity indicated by the D/fratio. Biofilms of C. albicans grown upon an AgNPs surface showed reduced mass and viscoelasticity in comparison with the growth on an unmodified surface and growth upon the various stages of surface creation i.e. an MUA Self Assembled Monolayer and a hydrazide surface. AFM images and analyses supported the presence of cells on these surfaces, as well as the reduction in cell number due to inhibition by nanopartic1es.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available