Effects of sugar concentration on the magnetite nanoparticles induced deformation and poration in giant vesicles

Abstract

This study integratedthree objectssuch as giant unilamellar vesicles (GUVs), anionic magnetite nanoparticles (NPs), and sugar concentrations to understand the mechanism for interacting the NPs with vesicle membranes under various sugar concentrations. We used sucrose inside the GUVs and glucose outside with equal osmolarity. 1,2-dioleoyl-sn-glycero-3-phospho-(1-rac-glycerol) (DOPG) and 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) were used to prepare the charged membranes, whereas only DOPC was used to prepare the neutral membranes. Phase contrast fluorescence microscopy shows that the adsorption of 18 nm anionic magnetite NPs to the vesicle membranes depends on the sugar concentration. The alterations of GUVs induced by the NPs are characterized in terms of i) vesicle compactness, ii) deformation, and iii) membrane poration. The presence of sugar provides additional structural stability to the GUVs and reduces the adverse effects of the NPs with respect to these parameters; more precisely, the higher the sugar concentration, the smaller the alteration induced by the NPs. The average compactnessdecreased with increase sugar concentration and at 60 min it was 1.34 0.004 and1.24  0.007 at 50 mM and 300 mM sugar in charged DOPG/DOPC-GUVs, and it also analogous for neutral DOPC-GUVs for the corresponding sugar concentration. The fraction of deformed GUVs decreased with the increase of sugar concentration. The time of poration at 50 mM was 50  7 s while its value was 189  9 s at 300 mMfor charged membranes. The differences in NPs effects at lower and higher sugar concentrations are explained by the change in the type of interaction between sugar molecules and lipid membranes, namely enthalpy and entropy-driven interaction, respectively. We have revealed the interaction of NPs with lipid bilayer at lower and higher sugar concentrations.