An undergraduate research project at Worcester Polytechnic Institute in Massachusetts led to creation of process to bind antimicrobial peptides to gold and silicon surfaces. The students, working under the direction of chemical engineering professor Terri Camesano, published their findings in a recent issue of the journal ACS Applied Materials and Interfaces (paid subscription required).
The students — Ivan Ivanov, Alec Morrison, Jesse Cobb, and Catherine Fahey — worked on the study during a Research Experiences for Undergraduates summer project at Worcester. The idea came from the capability of fish to extract oxygen through their gills, while filtering out pathogens with antimicrobial peptides.
“Fish have a wonderful solution for blocking bacterial and fungal infections,” says Camesano (pictured right). “In this study, we are working to better understand the biochemical mechanics of that process.”
The team tried two methods to bind the peptides to the surfaces. In the first method, the gold and silicon crystals directly absorbed the antimicrobial peptides. The second method involved attaching the tips of the peptides to the gold and silicon surfaces, with a glue-like substance. This second method enabled the peptides to array vertically from the surface, like blades of grass.
The researchers then cultured each of the surfaces with E. coli bacteria, and measured the ability of the coated surfaces to kill the bacterial cells. The findings showed that when the peptides are bound directly to the crystals and lying flat, they killed 34 percent of the bacteria in the culture. However, with the peptides attached at the tip and allowed to stand vertically, they killed 82 percent of the bacteria.
The students also devised a method for real-time monitoring of the attachment of antimicrobial peptides to surfaces. The team adapted a technique called quartz crystal microbalance with dissipation monitoring that measures the change in frequency of resonance of a quartz crystal, which can track the rate of deposition on a crystal of molecules or cells, and thus affect the crystal’s resonance.
With this technique, the researchers were able to measure the quantity of peptides attached to the surfaces in both the horizontal and vertical orientations, as well as the density of the peptide layers, and other properties. “This was a powerful process, to be able to essentially watch the binding process as it happened,” says Camesano.
Gold and silicon surfaces were selected for their chemical properties that are well-suited for binding with antimicrobial peptides. Camesano’s lab plans to continue to test the mechanics of peptide binding with other materials, including titanium, stainless steel, and plastics often found in food preparation and health care facilities.
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