Rapid and sensitive drug metabolism studies by SU-8 microchip capillary electrophoresis-electrospray ionization mass spectrometry

• Published in: Journal of Chromatography A 2011-02, Vol.1218 (5), p.739-745
• Main Authors: Nordman, Nina, Sikanen, Tiina, Moilanen, Maria-Elisa, Aura, Susanna, Kotiaho, Tapio, Franssila, Sami, Kostiainen, Risto
• Format: Article
• Language: English
• Subjects: Analysis; Analytical chemistry; Biological and medical sciences; Chemistry; Chromatographic methods and physical methods associated with chromatography; Electrophoresis; Epoxy photoresist SU-8; Exact sciences and technology; General pharmacology; Mass spectrometry; Medical sciences; Metabolism; Microfluidics; Other chromatographic methods; Pharmacology. Drug treatments
• ISSN: 0021-9673
• DOI: 10.1016/j.chroma.2010.12.010

Monolithically integrated, polymer (SU-8) microchips comprising an electrophoretic separation unit, a sheath flow interface, and an electrospray ionization (ESI) emitter were developed to improve the speed and throughput of metabolism research. Validation of the microchip method was performed using bufuralol 1-hydroxylation via CYP450 enzymes as the model reaction. The metabolite, 1-hydroxybufuralol, was easily separated from the substrate ( R s = 0.5) with very good detection sensitivity (LOD = 9.3 nM), linearity (range: 50–500 nM, r 2 = 0.9997), and repeatability (RSD Area = 10.3%, RSD Migration time = 2.5% at 80 nM concentration without internal standard). The kinetic parameters of bufuralol 1-hydroxylation determined by the microchip capillary electrophoresis (CE)-ESI/mass spectrometry (MS) method, were comparable to the values presented in literature as well as to the values determined by in-house liquid chromatography (LC)-UV. In addition to enzyme kinetics, metabolic profiling was demonstrated using authentic urine samples from healthy volunteers after intake of either tramadol or paracetamol. As a result, six metabolites of tramadol and four metabolites of paracetamol, including both phase I oxidation products and phase II conjugation products, were detected and separated from each other within 30–35 s. Before analysis, the urine samples were pre-treated with on-chip, on-line liquid-phase microextraction (LPME) and the results were compared to those obtained from urine samples pre-treated with conventional C18 solid-phase extraction (SPE, off-chip cartridges). On the basis of our results, the SU-8 CE-ESI/MS microchips incorporating on-chip sample pre-treatment, injection, separation, and ESI/MS detection were proven as efficient and versatile tools for drug metabolism research.