The detection of nucleic acid analytes is crucial for biomedical purposes such as diagnosis of human diseases, as well as industrial and environmental use. For diagnosing infections, a simple and facile assay which can be directly visualized with minimal technical requirements is in great need. Herein, we introduce a simple and wash-free assay based on the precipitation of fluorescent carbon-dot nanoparticles and amplified target DNA (Cdot-DNA assay), for detecting multidrug-resistant bacteria. Compared with traditional organic dyes as molecular labels, carbon-dots have advantages, such as high fluorescence signals, large bulk volume, and abundant functional groups on the surface. Cationic carbon-dot nanoparticles were fabricated by pyrolysis of polyethyleneimine as the carbon precursor with citric acid, using microwave radiation. For performing the Cdot-DNA assay, carbon-dot solutions were added with various amounts of DNA with different sizes, resulting in precipitation of the DNA by charge interaction with the carbon-dots and allowing simple visualization under a UV illuminator. The interaction of carbon-dots with DNA was characterized by dynamic light scattering (DLS) and zeta potential measurements. Finally, the Cdot-DNA assay could be applied for detecting bacteria-derived DNA, which was obtained from reverse transcription and amplification of the mRNA of the drug-resistance gene <i>KPC </i>from carbapenem-resistant <i>Klebsiella pneumoniae</i>, one of the major human commensal bacteria that cause opportunistic infections and have shown high incidence of acquiring multidrug resistance. The Cdot-DNA method introduces a simple and easily applicable diagnostic tool as a bedside assay, for detecting various superbugs that are relevant in hospital-acquired infections.

Fluorescent precipitation-based sensing of nucleic acid targets using carbon-dot nanoparticles for detecting multidrug-resistant bacteria

253rd National Meeting (2017)

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