Off-on detection of glutathione based on the nitrogen, sulfur codoped carbon quantum dots@MnO2 nano-composite in human lung cancer cells and blood serum.

An illustration of development of N,S-CQD-MnO 2 nanoprobe for the GSH detection • Highly fluorescent N,S-CQDs is synthesized hydrothermally with high QY. • N,S-CQDs-MnO 2 nano-composite based nanoprobe is designed for the rapid detection of GSH. • The proposed sensing system possesses high sensitivity and selectivity with a detection limit 0.012 μM. • To check the reliability, the developed method is fruitfully applied on human A549 cells and blood serum sample. In present study, the N,S-CQD-MnO 2 nano-composite is designed, which can perform as a sensitive nanoprobe for the 'off-on' sensing of GSH. The fluorescent N,S-CQDs were synthesized from the hydrothermal treatment of tartaric acid and taurine precursors. The synthesized N,S-CQDs exhibit strong blue emission with the high QY up to 47.4 %. MnO 2 nanosheet significantly quenches the blue fluorescence emission of N,S-CQDs by the phenomenon of fluorescence resonance energy transfer and strong electrostatic interactions between the N,S-CQDs and MnO 2 nanosheet. This reaction system could also work as off-on nanoprobe for GSH detection; the introduction of GSH into the reaction system reappears the fluorescence emission of N,S-CQDs by eradicating the fluorescence resonance energy transfer. Moreover, it is also found that the as-prepared N,S-CQD-MnO 2 based nanoprobe show very low cytotoxicity and good biocompatibility. The calculated detection limit is found to be 0.012 μM in a GSH concentration having a linear range of 0.1-0.7 μM. Interference study confirmed that the designed sensing system is specific toward the GSH detection compared to different amino acids along with some other biomolecules and metal interfering ingredients. Furthermore, the proposed method is successfully applied for the in vitro detecting and imaging GSH in A549 human lung cancer cells. Apart from this, the practicability of the proposed sensing system is also successfully applied in the quantification of GSH from human blood serum. Thus, our designed nanoprobe could be trustworthy for the several analytical and disease diagnosis. [ABSTRACT FROM AUTHOR]