Interaction of stearylamine-liposomes with erythrocyte ghosts: analysis of membrane lipid mixing and aqueous contents mixing, and the effect of carboxymethyl chitin on the interaction

Abstract

We have investigated the interaction of stearylamine (SA)-containing liposomes (SA-liposomes) with erythrocyte ghosts (EGs), utilizing the Tb-dipicolinate (Tb-DPA) assay for the mixing of the aqueous contents and a resonance energy transfer (RET) assay for the mixing of lipid. The results demonstrate that SA-liposomes and EGs, after aggregation, have a great tendency to mix their lipid before the mixing of the internal contents. The mixing of their contents takes place inside the vesicles due to the fusion of SA-liposomes and EGs, followed by the leakage of the contents from the vesicles. We have also explored the properties of the interaction of SA-liposomes with carboxymethyl chitin (CM-chitin), an inhibitor of the lipid mixing between SA-liposomes and EGs, using fluorescein-labeled CM-chitin (Flu-CMC). The polarization value of Flu-CMC increased upon SA-liposome binding, the amount of Flu-CMC on the liposome surfaces increased with the increase in the concentration of phospholipid and SA, and it decreased by 20–40% in the presence of 10 mM Ca 2+ ions, which have a high affinity for CM-chitin. These results show that the association of CM-chitin with SA-liposomes could be due to both electrostatic and hydrophobic interactions between SA-liposomes and CM-chitin.