Development and validation of a high-performance liquid chromatography method with fluorescence detection for the quantification of the resistance protein P-gp in cancer cells

A method using high-performance liquid chromatography coupled with fluorescence detection (HPLC-FLD) was developed and validated to quantify the innovative tool LightSpot®-FL-1, a selective permeability-glycoprotein (P-gp)-targeted fluorescent conjugate used to measure P-gp expression in cell samples. Quantifying P-gp is a major challenge in oncology as its overexpression in many cancer cells results in Multidrug Resistance (MDR) associated with chemotherapy failure. To develop the method reported herein, both sample preparation and analysis parameters were investigated. Optimal chromatographic conditions were achieved with 5 µL injections at a 1 mL/min flow rate on a reversed-phase Zorbax® Eclipse Plus 3.5 µm C18 column (150 × 4.6 mm) with isocratic acetonitrile/water (85/15, by volume) elution. Detection was performed with 505 nm excitation and 510 nm emission wavelengths. Validation studies were designed and performed according to the International Council for Harmonization (ICH) guidelines for bioanalytical method validation. The limit of quantification (LOQ) and limit of detection (LOD) were determined to be 0.5 and 0.2 nmol/L, respectively. The linearity range was demonstrated between 10 and 500 nmol/L, and the trueness and precision of the method were validated. Good stability was shown in three relevant analytical conditions. The greenness of the developed method was also demonstrated with the AGREE, AGREEprep and MoGAPI tools. Finally, the rapid, precise and sensitive validated analytical method was successfully applied to determine the difference in P-gp expression in three cancer cell lines: DU4475, CCRF-CEM and KG-1a.