Visual optical discrimination and detection of microbial pathogens based on diverse interactions of conjugated polyelectrolytes with cells

Pathogen infections caused by Candida albicans (C. albicans) and Escherichia coli (E. coli) have led to extremely serious consequences. Cultures of blood samples, which are regarded as the diagnosis standard, often exhibit variable sensitivity and always take several days to detect certain pathogens. Here we demonstrate for the first time that a blend of two cationic conjugated polymers, between which fluorescence resonance energy transfer (FRET) can be induced, is used to detect and discriminate C. albicans and E. coli in a rapid, simple and visual way without the need for any complicated instrumentation. Coupled with general polymerase chain reaction (PCR) technology, the method can detect pathogens specifically independent of electrophoresis analyses and real-time PCR, which avoids utilizing detrimental nucleic dyes and expensive fluorophore-labeled primers. Our new cationic conjugated polymer blend has two unique features. Firstly, the assay is simple and rapid. Upon mixing fungi or bacteria with the polymer blend, one can trigger the signal response directly in solution using a fluorimeter, which may have a far-reaching impact on clinical diagnosis. Secondly, the most important characteristic of the assay is direct visualization under UV light, which makes it more convenient than other methods that require sophisticated instruments. The cationic conjugated polymer blend exhibits great potential as an ideal diagnostic agent for the identification of pathogens.