Reynaldo Diaz – Seminar/PhD Thesis Defense – Monday, March 12, 2018 at 11:00 A.M.

JSNN – Reynaldo Thomas Diaz – Ph.D. Thesis Defense/Monday Seminar

Candidate: Reynaldo Thomas Diaz

Major Advisor: Dennis Lajeunesse, Ph.D.

Department: Nanoscience

Time: 11:00 A.M. – 1:00 P.M.

Location: JSNN Auditorium

2907 E. Gate City Blvd., Greensboro, NC 27401

Title: “High Resolution Visualization and Characterization of Cell Surface Adhesion Protein in Three Dimensional Nanoscale Interphases.”


This dissertation presents the study of microbial adhesion to surfaces using high magnification scanning particle beam microscopy.  Baker’s yeast with various levels of adhesive protein served  as the microbial model and the wings cicada insects was our main surface of interest.  The cicada insect’s wing presents a unique surface, when magnified one hundred thousand times we can see that the wing is composed of an even array of tiny nails.  I found that surfaces with nanoscale-features triggered unexpected responses in microbes; these responses can range from cell proliferation to total cell-wall disruption.  The reasons why certain surfaces disrupted the cell-wall remain unclear To address this question, we tested the role an adhesive protein and the surface topography at the nanoscale.  Due to the small scale in which this interaction occurs, scanning particle beam microscopy had to be used to make observations. To chemically confirm the protein visual location, it was necessary to develop a labelling technique.  We examine the use of immunogold for scanning particle beam microscopes using secondary electrons, backscatter electrons detectors, and electron dispersive x-ray spectrometry.  The image generated by secondary electrons and backscattered electrons has been traditionally used as correlative microscopy, yet we advise incorporating electron energy dispersive x-ray spectrometry (EDS) to the analysis for elemental confirmation.  EDS has been discouraged from being used at the magnification and uneven morphology presented in the study of microorganisms on surfaces.  We present suggestions on ways of overcoming the challenge of volume interaction.  The use of these techniques further enables the study of microbe adhesion to surfaces and increase the through put of analysis overcoming potential artifacts that may arise in scanning particle beam microscopy.  The findings of this study highlight the importance of surface topography when designing surfaces for microbial control. This is a promising find towards developing alternative microbial control both in medical field and everyday life.