Determination of intracellular sulphydryl compounds by microchip electrophoresis with selective chemiluminescence detection
An analytical method based on microchip electrophoresis (MCE) and chemiluminescence detection (CL) was developed for the determination of intracellular sulphydryl compounds. Cell injection/loading, cytolysis, electrophoretic separation, and CL detection were integrated onto a simple cross-microfluidic chip. Selective CL detection of sulphydryl compounds was achieved by deploying the luminol-Na(2)S(2)O(8) reaction. Under the CL conditions selected, many endogenous compounds in biological systems such as amino acids, biogenic amines, peptides and proteins did not produce any CL signal, which further ensured a high selectivity of the proposed MCE-CL assays. Sulphydryl compounds including cysteine (Cys), glutathione (GSH), and hemoglobin (Hb) were selected as the test compounds. The MCE separation was completed within 120s. The detection limits were estimated to be 7amol for Cys, 32amol for GSH and 69amol for Hb, respectively. The present method was applied to analyze individual red blood cells collected from both healthy subjects and cancer patients. It was found that the average intracellular contents of Cys, GSH and Hb were in the ranges of 26-43amol/cell, 128-323amol/cell and 522-667amol/cell, respectively for cancer patients, compared to 579-609amol Hb/cell and not detectable Cys and GSH for healthy subjects.