title: Imaging-based analysis of liposome internalization to macrophage cells: Effects of liposome size and surface modification with PEG moiety.
abstract: Liposome is one of the frequently used carriers for active targeting systems in vivo. Such parameters as its size, surface charge, and surface modifiers are known to influence the liposome uptake by macrophage cells. In this study, we investigated the effects of liposome size and polyethylene glycol (PEG) surface modifier on the liposomal internalization to murine macrophage (RAW-264.7), by using an imaging analysis technique. Three different sized liposomes (100, 200, and 400 nm in nominal diameter) labeled with rhodamine fluorescence were used. Liposome internalization appeared to reach a pseudo-steady plateau in about 5h incubation, and most of the internalized liposomes were seen to accumulate in the cytosol including cellular extensions. The maximum fluorescent density from the internalized liposomes was similar between 100 nm and 200 nm liposomes. However, that of the larger 400 nm liposome was approximately 1.7 times higher than the others, confirming the previous report that the larger the liposomes are the higher the degree of internalization is. When the outside of the 200 nm liposomes was modified with biocompatible anchor molecule (BAM) consisting of PEG (ca. 2kD molecular weight) moiety, the endocytosis was indeed reduced by about 2.1-fold, despite the increase of the hydrodynamic size due to BAM conjugation. This fluorescence-based cellular imaging analysis can be used to quantitatively monitor and optimize cellular internalization systems.
authors.affiliation: Department of Bionano Engineering, Hanyang University, Ansan, Republic of Korea.
authors.forename: Jae Sun
authors.initials: JS
authors.lastname: Lee
authors.affiliation: Department of Bionano Engineering, Hanyang University, Ansan, Republic of Korea.
authors.forename: Sang Youn
authors.initials: SY
authors.lastname: Hwang
authors.affiliation: Department of Bionano Engineering, Hanyang University, Ansan, Republic of Korea. Electronic address: eklee@hanyang.ac.kr.
authors.forename: E K
authors.initials: EK
authors.lastname: Lee
mesh_terms: D000818:Animals; D002460:Cell Line; D004705:Endocytosis; D008081:Liposomes; D008264:Macrophages / Q000378:metabolism*; D051379:Mice; D011092:Polyethylene Glycols / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D008081:Liposomes; D011092:Polyethylene Glycols
keywords: Endocytosis kinetics; Fluorescence intensity analysis; Liposomal internalization; PEG modification