The second phase of our project involved the attachment of nanoparticles to cells. The images above are of gold nanoparticles ranging in size from 1-10 nm attached to Saccharomyces cerevisiae cells. This followed the synthesis of nanoparticles and confirmation of their size and presence. More details on the synthesis can be found on our synthesis results page (insert link). The nanoparticles in the images above were synthesized using the Martin method and then coated with L-cysteine which allowed them to bind to the cell surface of yeast cells. This creates a gold nanoshell that we hope will serve as a form of protection for our yeast cells during the cell battle. To confirm that attachment was successful, the samples were viewed using bright-field microscopy. While individual nanoparticles are not visible through a typical light microscope, large aggregates of the nanoparticle are visible. This attempt at attachment was indeed successful as can be seen by the images above. The dark purple ring surrounding the yeast cells corresponds to our gold nanoshell. When we compare the nanoparticle-coated yeast to control yeast cells, we can see that the dark purple rings are not present in the control. Furthermore, when the cells are viewed in different planes it is clear that the outside of the yeast cells appear dark purple, corresponding to the nanoparticles attached to the surface. The last set of images show what happens if we increase the ratio of nanoparticles-to-cells during the attachment procedure. Some clumping appears in these images.

After confirming the success of nanoparticle attachment through bright-field microscopy, our team searched for a way to add further support to our results. We discovered some studies in which researchers used dark-field microscopy to view nanoparticle attachment to cells. The images above are of spherical gold nanoparticles ranging in size from 1-10 nm attached to Saccharomyces cerevisiae viewed under a dark-field microscope with a camera attachment. The images have been color inverted to better visualize the nanoparticles. The gold nanoparticles appear to glow green under dark-field, this makes it clear which cells are coated in nanoparticles. In the first three images, the nanoparticles used were synthesized from the Martin method and were successfully attached to the yeast cells. In the last image, the nanoparticles were synthesized using garlic extract. These nanoparticles were less successful at attaching to the cells. It is possible that they need to be further purified so there is no plant extract left in the solution to interfere with attachment.