Liposomes and Blood Cells: A Flow Cytometric Study

Abstract

To clarify the interactions of liposomes with blood cells, this study examined the behaviour of liposomes of a range of compositions in the presence of purified human blood cells in buffer or plasma; or in whole blood, or in mice in vivo. Liposomes, labeled with the hydrophilic fluorochrome, carboxy fluorescein (CF), or with membrane-sequestering R18 or FITC-labeled phospholipids, were mixed with blood cells and the appearance of the fluorochromes in the blood cell population was monitored by flow cytometry. Irrespective of composition, with or without poly(ethylene glycol), all types of liposomes were found to interact rapidly and dose-dependently with red cells, leukocytes and platelets, both in vitro and in vivo. This took place equally in the presence and the absence of plasma proteins and functional enzyme cascades, suggesting that the prime facie interaction is opsonization-independent and is consistent with liposome-blood cell fusion.

Blood Compatibility of Cetyl Alcohol/Polysorbate-Based Nanoparticles

“…4), indicating that the character of the interaction is most likely not related to the surface of the nanoparticle. In fact, similar findings were reported by Constantinescu et al (6) where kinetics of liposomes/platelet association were the same for uncoated liposomes and PEG-coated liposomes.…”

“…The rapid interaction of nanoparticles with platelets agrees with other reports (6). Constantinescu et al (6) observed that association of liposomes with blood cells was in most cases complete within 1 min.…”

“…Based on these observations, it was concluded that negatively charged liposomes have the ability to activate contact factors such as Hageman factor and possibly factor XI, which further leads to activation of the blood clotting system (10). The association of various types of liposomes with blood cells was also studied by Constantinescu et al (6). Liposomes were mixed with whole blood, and association with platelets, red blood cells, and leukocytes was determined using flow cytometry.…”

“…Constantinescu et al (6) hypothesized that phospholipids from the liposomes fuse with cell membranes. However, no studies were performed to investigate the influence of liposomes on the function on each blood cell component and hemostasis.…”

Enhanced efficacy of recombinant FVIII in noncovalent complex with PEGylated liposome in hemophilia A mice

“…9 Microparticles not only generally provide a phosphatidylserine-enriched surface for the assembly of Xase and prothrombinase, but also express sustained high-affinity receptors for FVIII to promote a thrombin burst on their membranes. 10,11 Liposomes have been shown to interact rapidly with blood cells such as platelets via lipid exchange, membrane fusion, 12 or sequestration. 13,14 Therefore, it was hypothesized that via association with PEG-Lips, a small fraction of rFVIII was deposited to the cellular and subcellular compartments of blood including microparticles, where FVIII would be protected for a prolonged period of time to effectively promote clot formation, and yet evade detection in plasmabased assays.…”