Determination of ascorbic acid in individual liver cancer cells by capillary electrophoresis with a platinum nanoparticles modified electrode

Nanoparticles-based electrochemical sensor has received significant interest. In this work, platinum nanoparticles modified carbon fiber micro-disk electrode (PtNPsME) was electrochemically prepared and exploited as an amperometric detector for capillary electrophoresis. The prepared sensor displayed rapid and sensitive response towards ascorbic acid (AA), which was attributed to the electrocatalytic effect of platinum nanoparticles. Under optimized detection conditions, AA responded linearly from the range of 1.0 μM to 8.0 μM and 8.0 μM to 1 mM with correlation coefficients of 0.9981 and 0.9993. The concentration detection limits was 0.5 μM (S/N = 3). Compared with carbon fiber micro-disk electrode, the sensitivity was enhanced nearly four times. Acceptable repeatability of the microanalysis system was verified by ten consecutive injections of 0.5 mM, 50 μM and 5 μM AA without capillary and electrode treatments, the relative standard deviations of peak areas and migration time were 4.9% and 2.5%; 5.3% and 2.5%; 5.9% and 2.8%, accordingly. Meanwhile, well-shaped electrophoretic peaks were observed, mainly due to the fast electron transfer of electroactive species on the PtNPsME. The developed capillary electrophoresis–electrochemistry setup was first applied to the determination of ascorbic acid in single liver cancer cells (HepG2). The mean amount of AA in HepG2 cells extract and the average amount in single cells could amount to 9.4 ± 1.3 fmol (n = 3) and 12.9 ± 4.3 fmol (n = 20), respectively. Several merits of the novel electrochemical sensor coupled with capillary electrophorsis, such as comparative repeatability, easy fabrication and high sensitivity, hold great potential for the single-cell assay.