Rational design of a FRET-based nanoprobe of gold-conjugated carbon dots for simultaneous monitoring and disruption of Pseudomonas aeruginosa biofilm through selective detection of virulence factor pyocyanin

Successful and effective treatment of different types of infections depends upon fast and selective identification of the microorganisms. Pseudomonas aeruginosa is a Gram-negative bacterium which is involved in a number of human infections and may become life-threatening for immunocompromised persons. Pyocyanin is a unique exotoxin which is exclusively secreted as a virulence factor by P. aeruginosa. In this respect, a nano-assembly, composed of a carbon dot conjugated gold nanocomposite (Au@OPCDPEG) having a size of similar to 11.5 +/- 1.6 nm, was synthesized and used as both a fluorescence resonance energy transfer (FRET) and a colorimetric sensor for pyocyanin detection. When titrated with increasing concentrations of pyocyanin, Au@OPCDPEG NPs showed similar to 1.76 +/- 0.12 times increase in fluorescence intensity (at similar to 505 nm), whereas three distinct isosbestic points were observed in absorption studies. The limit of detection for pyocyanin was found to be similar to 3.04 +/- 0.27 mu M. It was found that Au@OPCDPEG NPs can selectively recognize pyocyanin even in the presence of other toxins under different biological interference. Real-time P. aeruginosa detection studies suggested the minimum detection limit to be similar to 1.5 x 10(6) cfu ml(-1) even in the presence of Staphylococcus aureus contamination in the sample. Confocal studies suggested that Au@OPCDPEG NPs can effectively penetrate P. aeruginosa biofilm under laser irradiation. Overall, the present engineered nanoprobe provides an easy, fast and selective method for the detection of P. aeruginosa in biological samples.