Nitric Oxide Sensing through Azo-Dye Formation on Carbon Dots

Detection of Nitric oxide (NO) is very important as NO plays a crucial role in many biological process including neuronal, cardiovascular, and immunological processes associated with macrophage and neutrophil activation. Irregular NO homeostasis is an indication of inflammatory response generally associated with various diseases and disorders. We designed an amine functionalized Carbon dots (C-dots) from aminoguanidine and citric acid and perceived the detection of NO in aqueous solution and also in vivo (macrophage cells). The C-dots conserved the functional groups of aminoguanidine which further reacts with NO and is responsible for the color and the fluorescence transformations. Particularly, the aminoguanidine/citric acid C-dots were non-cytotoxic, so this nano-sensor has been used for real time monitoring of generation of intracellular NO on addition of LPS (lipopolysaccharides). This C-dot was further employed to observe the effect of a NOS (Nitric oxide synthase) inhibitor L-NAME (N_ω-Nitro-L-argininemethylesterhydrochloride) and a Ca²⁺ chelator known to interfere with NOS enzymatic activity BAPTA-AM. To understand the proposed mechanism multi-prong spectroscopic and chromatographic techniques were used, and we deciphered the molecular mechanism for the NO induced color change and fluorescence transformation. The polymerization of C-dots through azo-dye formation along with N₂ release from its surface was observed for the first time with concomitant fluorescence quenching.^[1]

Figure 1. Schematic presentation of detection methodology

References

[1] S. Bhattacharya, R. Sarkar, B. Chakraborty, A. Porgador and R. Jelinek, ACS Sensors 2 (2017) 1215-1224.

Acknowledgements

Financial assistance from the Ministry of Science, Israel, is acknowledged.