Relevance. BCRP is an efflux transporter protein that plays an important role in the pharmacokinetics of a wide range of drugs. The BCRP activity in vitro experiments is assessed by the transport of transporter protein substrates (methotrexate, etc.) across the bilipid membrane of cells overexpressingBCRP, for example, Caco-2 cells. The aim is to develop and validate a method for the quantitative determination of the BCRP substrate, methotrexate, in the transport medium of Caco-2 cells by HPLC-MS/MS. Methods. The work was performed on an Ultimate 3000 HPLC chromatograph (ThermoFisher, USA) with a TSQ Fortis tandem mass-selective detector (ThermoFisher, USA). The conditions of chromatographic analysis were as follows: column UCT Selectra C18 4.6 mm * 100 mm 5um, 100A, Selectra C18 Guard Cartridges SLC-18GDC46-5UM, separation temperature 35 °С, flow rate 0.3 ml/min, injected sample volume - 2 μl, analysis time - 10 min. Used a gradient elution: the ratio of the solution of 0.1 % formic acid and acetonitrile was at 0 min 75 and 25 %; 0.4 min 60 and 40 %; 6 minutes 20 and 80 %; 8 minutes 75 and 25 %. Under these conditions, the retention time of methotrexate is 3.11 minutes. Detection conditions: methotrexate - positive ionization mode, 455.15 m / z → 308.125 m / z, collision energy 22.99 V, source fragmentation 5, CID gas pressure 2 mTorr. The extraction of methotrexate from the transport medium (Hanks solution with 25 mM Hepes and 1% dimethyl sulfoxide) after incubation with Caco-2 cells for 3 h was carried out with a mixture of methanol + water in a ratio of 1: 1. Results. The developed method was validated according to the following parameters: selectivity, linearity, accuracy, precision, limit of quantitative determination, sample transfer, sample stability. The confirmed analytical range of the method was 60 -10,000 nmol / L in the transport medium. Conclusions: a method for the quantitative determination of methotrexate in the transport medium of Caco-2 cells by HPLC-MS / MS was developed and validated.
Fluorescence Quenching-Based Mechanism for Determination of Hypochlorite by Coumarin-Derived Sensors