A combined solid phase extraction/capillary gel electrophoresis method for the determination of phosphorothioate oligodeoxynucleotides in biological fluids, tissues and feces

A novel biological sample clean-up procedure has been developed for the determination of phosphorothioate oligodeoxynucleotides (PS-ODNs) and derived metabolites in biological fluids (plasma, urine and bile) and in tissues and feces from mice and rats. This method uses a one-step C18 solid-phase extraction (SPE) for biological matrix removal, and it uses capillary gel electrophoresis (CGE) for analyte detection. The assay is specific, and its linearity is superb (r > 0.99) for IV-AS (a 13-mer PS-ODN) and PS19 (a 19-mer PS-ODN) in a variety of biological matrices. For both IV-AS and PS19, the precision, accuracy and absolute recovery values were found to be <20%, ±20% and 80–120%, respectively. The LODs of IV-AS and PS19 were 0.6 mg/l for plasma, 0.8 mg/l for rat urine and bile, 6 μg/g for rat tissues, and 10 μg/g for rat feces, with a signal-to-noise ratio of 3 (S/N = 3). This method has been successfully applied to the analysis and quantitation of PS-ODNs in various biological samples arising from preclinical pharmacokinetic studies.