Synthesis of KCl-doped lignin carbon dots nanoenzymes for colorimetric sensing glutathione in human serum

A KCl-doped lignin carbon dots (K,Cl-LCDs) nanoenzymes was successfully synthesized by hydrothermal method to construct a sensor for detecting glutathione (GSH). Sodium lignosulfonate with a lot of oxygen-containing functional groups as a carbon precursor can provide effective active sites, and KCl as a dopant can influence the charge distribution on the surface of CDs. In the enzyme catalyzing progress, K,Cl-LCDs with peroxidase-like activity can oxidize 3,3,5,5-tetramethylbenzidine (TMB) into blue oxTMB with the presence of H2O2, the absorbance of the system at 652 nm changed consequently. When GSH is introduced into the system, the reducibility of GSH restores oxTMB to colorless. So that, a sensor for colorimetric detection of GSH is constructed. In addition, through free radical experiments, the catalytic mechanism was explored, confirming that the reaction was induced by hydroxyl radicals (·OH). The sensor has a low detection limit (0.08 μM) for detecting GSH with good linear range (0.25–25 μM). The sensor system was applied to the determination of GSH concentration in human serum samples with the recoveries of 98.2%− 103.2% and RSDs of 2.3%− 4.7%. The proposed sensor for GSH detection has the advantages of simple operation, low cost, and high speed, indicating its potential application in bioanalysis.