Investigation of Bactericidal Polymers by Bioluminescent Reporter Pathogen Detection by
Thomas Stratton and Jeffrey P. Youngblood

Hydrophobic quaternary salts are active against gram-positive and gram-negative bacteria, even against drug-resistant strains. Unfortunately, these materials are also not water-soluble and have poor biocompatibility (they tend to irritate human cells). Our research aims to synthesize copolymers that combine the anti-bacterial properties of quaternary salts like poly(vinyl pyridine) (PVP) with the solubility and biocompatibility of common polymers like poly(ethylene glycol methacrylate) (PEGMA) and poly(hydroxyethyl methacrylate) (PHEMA). Hopefully these materials will be incorporated in such things as burn and wound dressing, contact lenses, dental materials, and disinfectant surfaces.

Currently I am conducting the microbial testing of our polymer samples.  Initially I developed a high-throughput method of sample analysis utilizing a CCD camera from Prof. Bruce Applegate's group in the Department of Food Science, which enables us to capture real video images of up to six samples simultaneously. Earlier testing used a photo-multiplier tube that could only analyze one sample at a time. We are also using a Wallac 1420 multi-well plate tester that uses a PMT to analyze eight (or more) samples simultaneously.

I currently plan to extend the breadth of our microbial testing to include a variety of other bacteria (p. aeruginosa and bacillus are currently planned), as well as fungi and viruses (bacteriophage studies are currently planned).  Ultimately I plan to further improve the antibacterial and biocompatible properties of our materials by refining the polymerization process and testing additional copolymer elements to further deter bacteria or improve surface characteristics.  I also want to ask further questions on a more basic level: Can we more accurately determine the exact method of action of quaternized PVP or other related polyquats?  Our research has shown that even a few percent of PEGMA copolymerized to PVP can drastically reduce the contact angle of water on the surface, lower than the contact angles of PVP or PEGMA alone.  What is the source of this anomalous behavior?  I hope to answer these and further questions with my research.

Preliminary CCD image of control (right column) and various bactericial formulations (left column) after one hour. The bacteria are e. coli which have been modified with the lux gene so they emit light as long as they are metabolising.

E. coli at 15000x magnification in a scanning electron microscope. NIH Image.