Analytical ultracentrifugation for measuring drug distribution of doxorubicin loaded liposomes in human serum

Abstract The potential of analytical ultracentrifugation (AUC) in the analysis of the drug distribution of liposomal doxorubicin formulation (with nominal diameter of 85 nm) in the presence of human serum proteins is demonstrated using the absorbance detection function of the instrument. Based on the AUC measurement (and model fitting for molecular mass calculation), we show that in a single experiment, it is possible to measure the relative amounts of the free drug, of the liposome-encapsulated drug, and of the serum protein-bound drug. In addition, the same data provides both the accurate particle size distribution of the liposomal formulation in human serum and information on the protein that binds doxorubicin in the drug-protein fraction (in this case, human serum albumin). Thus, a single experiment (that requires only minimal sample preparation) provides several critical physical-chemical attributes of liposomal drug formulations. This innovative approach will greatly help in the development of improved methods for the challenging problem of characterizing nanomedicine in relevant biological matrices.