Colorimetric and fluorescent detection of glutathione over cysteine and homocysteine with red-emitting N-doped carbon dots

Abstract Glutathione (GSH) is an important biothiol in biological systems and serves as a significant biomarker for the health of humans. Herein, red-emitting carbon dots (p-CDs) prepared by a simple one-step solvothermal process can exclusively, rapidly and sensitively respond to GSH owing to the high content of pyridinic N. Upon addition of GSH, p-CDs instantly give a significant color change from orange to bluish-purple. The absorbance ratio of 576 nm to 486 nm is linearly proportional to the logarithmic concentration of GSH in a wide range of 12.5−800 μM, which is the level of cellular GSH. Meanwhile, the fluorescence of p-CDs quenches obviously. The LOD of p-CDs towards GSH in fluorescence mode is 0.7 μM. Moreover, p-CDs have no response to Cys, Hcy, amino acids and ions existing in biological systems. Such a promising responsiveness offers a great opportunity to accurately, sensitively and selectively detect GSH by colorimetric and fluorescent dual modes. In addition, cellulose/p-CDs hydrogels and p-CDs-based test papers have been fabricated to successfully detect GSH according to the color-change and fluorescence quenching. The biocompatible, environment-friendly and disposable cellulose/p-CDs materials readily provide a simple and visual strategy to detect GSH levels in the biomedical fields.