Novel analytical method to evaluate the surface condition of polyethylene glycol-modified liposomes

. [Display omitted] ► We established a new chromatography for the evaluation of PEGylated liposomes. ► It was able to separate PEGylated liposomes by their PEG-lipid contents. ► It enabled the evaluation of the PEG-lipid deviation among PEGylated liposomes. ► We also demonstrated the difference between the pre- and post-modification method. ► We found that proper incubation time was needed to achieve high quality PEGylation. In liposomal drug delivery, polyethylene glycol (PEG) modification is known to prolong the circulation time of liposomes in the blood stream, and hence, this method has been employed for liposomes in clinical use. To achieve effective prolongation of liposomal circulation time using PEG-modification, it is of importance to control not only the average amount of PEG chains incorporated in the liposomes but also the deviation in PEG amount among PEG-modified liposomes (PEGylated liposomes). Therefore, evaluation of PEG-modification is essential for the quality control of PEGylated liposomes. In this study, we developed a novel method to estimate PEG-modification for PEGylated liposomes using chromatography with an anion-exchange column. We applied this method to liposomes with varying PEG-lipid contents and found that the chromatography could successfully separate PEGylated liposomes on the basis of the PEG-lipid content of their liposome membranes. Results demonstrate that the established method can be potentially used to control the quality of PEGylated liposomes not only for research and but also for manufacturing processes.