Qualitative and quantitative analysis of tumor cell metabolism via stable isotope labeling assisted microfluidic chip electrospray ionization mass spectrometry.

In this work, a stable isotope labeling assisted microfluidic chip electrospray ionization mass spectrometry (SIL-chip-ESI-MS) platform for qualitative and quantitative analysis of cell metabolism was developed. Microfluidic cell culture, drug-induced cell apoptosis analysis, and cell metabolism measurements were performed simultaneously on the specifically designed device. MCF-7 cells were cultivated in vitro and exposed in anticancer agent (genistein and genistein-d(2)) for cell-based drug assay. A dual-isotopic labeling was presented for effective qualitative analysis of multiplex metabolites. Interestingly, three coeluting pairs of isotopomers appeared with an m/z difference of two. Despite complex biological matrixes, they can be easily recognized and identified by chip-ESI-MS/MS, which significantly facilitates candidate biomarker discovery. The quantitative performance of this system was evaluated using genistein as a model drug by means of stable isotope dilution analysis. The linear equation obtained is y = 0.06x - 3.38 × 10(-3) (R(2) = 0.995) at the dynamic range from 0.5 to 40 μM. The detection limit is 0.2 μM. The method shows an excellent stability of 2.2% relative standard deviation (RSD) and a good repeatability of 5.5% RSD. Our results have successfully demonstrated the capability of selective and quantitative analysis of cell-based drug absorption and metabolites with high stability, sensitivity, and repeatability on the chip-ESI-MS system. Consequently, the present device shows promise as a high-throughput, low-cost, and online platform for cell metabolism studies and drug screening processes.