Quantitative LC–MS determination of liposomal encapsulated prednisolone phosphate and non-encapsulated prednisolone concentrations in murine whole blood and liver tissue

Abstract

The underlying pharmacokinetic profile of liposomal drug delivery systems is not yet fully known. This is primarily due to a lack of suitable quantitative bioanalytical methodology to simultaneously determine separate liposomal-encapsulated and non-encapsulated drug tissue concentrations in complex biological samples. Here, an LC–MS method was developed which enables the simultaneous quantification of separate liposomal-encapsulated prednisolone phosphate and non-encapsulated prednisolone concentrations in whole blood and liver tissue.Liquid chromatography, negative electrospray ionization and Orbitrap-MS analysis allowed highly accurate and sensitive detection of prednisolone phosphate (PP) and prednisolone (P) in complex matrix. Using dexamethasone phosphate and dexamethasone as internal standards, the quantitative LC–MS method was optimized and validated for high selectivity, sensitivity and quantitative accuracy of PP and P from liposomes.The lower limits of quantitation were 0.99μmol/L blood and 0.53nmol/g liver for PP, and 229nmol/L blood and 0.514nmol/g liver for P. Quantitative accuracies of 84–118% were observed. The intra-run precision was ≤11%.Application of this new LC–MS method will yield the first liposomal pharmacokinetic profile showing accurate encapsulated and non-encapsulated drug tissue concentrations separately. This is also the first quantitative LC–MS method for the simultaneous quantification of the prodrug PP and its parent drug P in whole blood and liver tissue samples.