On-chip labeling with NDA for determining glutathione in single cell using microfluidic chip electrophoresis

A simple method for the defection of glutathione (GSH) in single human erythrocyte was developed using on-chip mode dynamic labeling by adding the 2,3-naphthalene-dicarboxaldehyde (NDA) simply in microchip electrophoresis buffer, with functional integration of cell sampling, single cell loading docking, lysing, dynamic labeling, electrophoresis separation and laser induced fluorescence (LIF) detection. By using a combination of hydrostatic pressure and low electric field, single cell sampling speed and long-term stability were improved. After lysing, the reaction between the released GSH and NDA included in electrophoresis buffer can be completed within a migrating distance of 0.5 cm in the. microchip separation channel during electrophoresis. The average separation efficiency for GSH was 2.4 x 10(6) plates/m, which was not a significant difference from off-chip derivatization. The GSH migration time on the on-chip mode and off-chip method were 116 and 110 s, respectively. The present method can be used to minimize the dilution of the contents of single cell during the derivatization to maintain favorable kinetics for the labeling reaction, simplify the cell treatment and save the sample and reagent. A half fife of 5 days of GSH in human erythrocyte was found by using this method.