Fluorescent polymers flag bacterial infections.

A team of Swiss and US chemists has developed a novel method for detecting bacteria using fluorescent polymers. This quick and flexible method may be tuned to detect a wide range of different bacteria to provide a means of testing for pathogens in food and water.

The chemists from the Swiss Federal Institute of Technology, Zürich, and the Massachusetts Institute of Technology, Cambridge, have taken advantage of the fact that bacteria usually infect cells by binding to carbohydrate molecules on their surface. Scientists have already identified and studied many of these cell surface carbohydrates, and realised that if they attach carbohydrates to a fluorescent polymer then it could be used to stain populations of bacteria.

To test the idea, multiple molecules of the carbohydrate mannose – which Escherichia coli naturally binds to – were linked to a chain of the polymer poly(p-phenylene ethynylene) (PPE). On incubating PPE with E. coli, the bacteria would bind to the polymer to form clusters of up to several thousand bacteria. These clusters could easily be detected by irradiating the solution, causing the polymers to fluoresce.

By steadily diluting the solutions of E. coli, the chemists discovered that the fluorescently-stained clusters could still be observed when relatively few bacteria were present. Furthermore, this method is faster than current methods for detecting bacteria, taking 10–15 minutes compared with days.

To use this method to detect other species of bacteria, researchers need only attach different carbohydrates to the polymer. ‘We are working on the detection of cholera, gingivitis and hospital-borne pathogens common to many bacterial infections,’ lead researcher Peter Seeberger told Chemistry World. ‘In addition, we are now using carbohydrate arrays to determine pathogen specificity for certain sugars and are using this information for the preparation of polymers carrying more sophisticated carbohydrate structures.’

Jon Evans