Quantitative analysis of phosphorothioate oligonucleotides in biological fluids using direct injection fast anion-exchange chromatography and capillary gel electrophoresis.

The analysis of antisense phosphorothioate DNA (SODN) in human plasma via direct injection using anion-exchange high-performance liquid chromatography (AE-HPLC) is presented. The method relies on the ability to selectively extract phosphorothioate DNA from undigested serum, plasma and urine on anion-exchange resins. The automated HPLC method can analyze a sample every 5 min with a limit of detection of 50 ng/ml (ppb). The DNA was collected, desalted and analyzed by capillary gel electrophoresis. Due to the high resolving power of this technique, a qualitative assessment of enzymatic degradation of the antisense oligonucleotide can be made.