Floating films capture pathogens

A US researcher is working on a project to develop floating films that collect and concentrate pathogens at the surface of water.

The films could facilitate the collection of water samples for analysis, for example, and provide early warning of harmful biological contamination in rivers, lakes and reservoirs – once they have been developed beyond the research stage.

Even though low concentrations of harmful microbes and toxins are difficult to detect in large bodies of water, Elaine Mullen, a biological researcher at MITRE's Center for Integrated Intelligence Systems - where the research is underway - thinks that the new films can do the trick.

The films themselves are made from oils and glycoproteins found in plant and animal tissue. Wave action breaks the film into tiny globules or micelles. The outer surface of the micelle contains glycoproteins that contact waterborne pathogens.

Mullen explained that, on a molecular level, the glycoprotein is a protein with an attached carbohydrate that resembles a tree branch composed of branching sugar units.

"These sugars are the key," said Mullen, "because they act like biological Velcro when a pathogen contacts a certain sequence of sugar molecules. Specific sugar chains can grab onto pathogens and biotoxins like a burr sticks to your clothes."

In one case, a film with a human blood-type sugar group has been shown to capture certain E. coli strains from biological fluids. In another case, proteins in the whites of pigeon eggs were shown to have sugars that capture several serious pathogens, including E. coli strains that cause infections.

Before Mullen creates new films, she conducts research involving two bioinformatics databases. The first is a commercial database called GlycoSuite that lists sugars attached to proteins and is licensed by MITRE. The second is the new SugarBindDB database, also developed by the company.

SugarBindDB is a compilation of literature about sugars that attach to various bacteria and viruses. It lists human and domestic animal pathogens that bind to certain specific sugar configurations that are on the cells of tissue that is infected by that pathogen. Thus, Mullen works to create specific films to detect specific pathogens. Multiple glycoproteins can also be put into a film so that one film can detect a variety of pathogens.

MITRE is working with the Johns Hopkins University Applied Physics Laboratory (APL) to investigate ways of enhancing biocapture films by varying glycoprotein components.

A new atomic force microscope at APL will be used to look at film surfaces on a nanometre scale. Another company, Versar/GEOMET, is working with MITRE and APL to do scale-up studies to test the ability of films to capture bacteria in different environments.