Development and validation of a sensitive reversed-phase HPLC method to determine intracellular accumulation of hydroxycamptothecin

The intracellular accumulation of anti-cancer agents strongly influences the efficiency of chemotherapy for cancer. In the present study, a simple, rapid, sensitive reversed-phase high-performance liquid chromatographic (RP-HPLC) method was developed and validated to determine hydroxycamptothecin (HCPT) in Eca109 cells. HCPT in cellular lysis solution were measured by RP-HPLC with a C18 column after extraction with ethyl acetate. The mobile phase contained 0.1% triethylamine–phosphoric acid buffer (pH 3.0) and acetonitrile (75:25, v/v). Fluorescence detector with excitation and emission wavelengths of 382 and 528 nm was used for determination of HCPT. The calibration curve was linear from 2 to 100 ng/ml with correlation coefficient of 0.9999, while the limit of quantification is 2 ng/ml. The recovery of assay was between 86.5 and 105.2%. The intra- and inter-day coefficients of variation were less than 10% (R.S.D.). Furthermore, the validated method was used to determine the accumulation of HCPT after incubating the liposomal formulation of HCPT and HCPT for injection with the intact cells. HCPT liposomes showed higher intracellular accumulation of HCPT at different incubation times compared with that of conventional HCPT injection.