Dual-Response Detection of Oxidized Glutathione, Ascorbic Acid, and Cell Imaging Based on pH/Redox Dual-Sensitive Fluorescent Carbon Dots

The pH/redox dual-sensitive fluorescent carbon dots (pHRCDs) with the fluorescence quantum yield of 16.97% were synthesized by the pyrolysis of l-glutamic acid (l-glu) and dopamine (DA). Compared with the quantum dot (QD)–dopamine conjugate, when the pH value of the solution was changed from neutral to alkaline, the pHRCDs exhibited unique optical phenomenon including red-shift of fluorescence peak and the fluorescence intensity first decreasing from pH 7 to 10 and then increasing from pH 10 to 13. The pHRCDs could be developed for a discriminative and highly sensitive dual-response fluorescent probe for the detection of oxidized glutathione (GSSG) and ascorbic acid (AA) activity in human blood. Under the optimized experimental conditions, the dual-response fluorescent probe can detect GSSG and AA in the linear range of 1.2–3.6 and 27–35 μM with the detection limits of 0.1 and 3.1 μM, respectively. In addition, the pHRCDs demonstrated low cytotoxicity and good biocompatibility, which can be well applied to in vitro cell imaging, and the pHRCDs/GSH fluorescence system has been successfully developed for the detection of AA in real samples.