Effect of superparamagnetic iron oxide nanoparticles on fluidity and phase transition of phosphatidylcholine liposomal membranes

Abstract

Superparamagnetic iron oxide nanoparticles (SPIONs) with multifunctional properties have shown great promise in theranostics. The aim of our work was to compare the effects of SPIONs on the fluidity and phase transition of the liposomal membranes prepared with zwitterionic phosphatidylcholine lipids. In order to study if the surface modification of SPIONs has any influence on these membrane properties, we have used four types of differently functionalized SPIONs, such as: plain SPIONs (primary size was shown to bê11 nm), silica-coated SPIONs, SPIONs coated with silica and functionalized with positively charged amino groups or negatively charged carboxyl groups (the primary size of all the surface-modified SPIONs was ~20 nm). Small unilamellar vesicles prepared with 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine lipids and multilamellar vesicles prepared with 1,2-dipalmitoyl-sn-glycero-3-phosphocholine lipids were encapsulated or incubated with the plain and surface-modified SPIONs to determine the fluidity and phase transition temperature of the bilayer lipids, respectively. Fluorescent anisotropy and differential scanning calorimetric measurements of the liposomes that were either encapsulated or incubated with the suspension of SPIONs did not show a significant difference in the lipid ordering and fluidity; though the encapsulated SPIONs showed a slightly increased effect on the fluidity of the model membranes in comparison with the incubated SPIONs. This indicates the low potential of the SPIONs to interact with the nontargeted cell membranes, which is a desirable factor for in vivo applications.

Keywords:

• encapsulated SPIONs
• incubated SPIONs
• zwitterionic liposomes
• membrane integrity
• phase behavior

Acknowledgments

This work was supported by the Slovene Human Resources Development and Scholarship Fund (Grant no 11013-9/2012-6). The investigation was also supported by the Ministry of Education, Science, Culture and Sport of Republic of Slovenia under a grant “Innovative scheme of co-funding doctoral studies promoting co-operation with the economy and solving of contemporary social challenges” (Grant no 160-21). This project has also received funding from the Slovenian Research Agency (ARRS) under grant agreement no J1-4109, P4-0121 and P3-0108. We acknowledge the use of equipment in the Center of Excellence on Nanoscience and Nanotechnology-Nanocenter. The authors would like to thank Dr Janez Valant, Dr Ajda Ota, and Linda Štrus for their technical assistance.

Disclosure

The authors report no conflicts of interest in this work.