Study Of Liposomes Decorated By Hydrophobic Magnetic Nanoparticles:Microstructure, Properties And Applications

Magnetoliposomes(MLs), consisting of liposomes and magnetic nanoparticles (MNPs), have been tailored as very promising delivery vehicles in biotechnology and biomedicine applications. Liposomes with hydrophilic MNPs in their inner water are the major targets of numerous studies, while liposomes with hydrophobic MNPs in membrane were scarcely reported. In this paper, researches were carried out on magnetoliposomes with the latter structure. The main contents are as follows:1Hydrophobic MNPs coated with AOT was synthesized by microemulsion method, which was followed by rotary evaporation treatment in order to coat the synthesized MNPs with hydrophobic surface. The superparamagnetic MNPs are spherical in shape with the diameter of about6nm, and it can be dispersed stably in chloroform. Liposomes with hydrophobic MNPs in membrane were prepared by modified supercritical carbon dioxide method. The hydrophobic MNPs were successfully embedded in the lipid bilayer, which was proved by the distorted lipid bilayer and the changed membrane fluidity.2The interaction between hydrophobic MNPs and lipid bilayer was investigated applying atomic force microscope, steady-state/time-resolved fluorescence probe method and computer simulation method. The microstructure research indicated that the hydrophobic MNPs in the lipid bilayer not only improved membrane fluidity but also enlarged the nonpolar domain and the free volume in membrane. Moreover, systematic researches were carried out to investigate the effects of hydrophobic MNPs concentration on the morphology and microstructure of liposomes. The results show that the lipid bilayer was saturated with the hydrophobic MNPs when the mass ratio of MNPs to lipid reached0.002. The computer simulation results showed that the membrane area shrank after the MNPs embedment, because the diameter of MNPs was larger than the thickness of lipid bilayer.3In addition, the size distribution, encapsulation efficiency, release properties and magnetic response were also studied, which shed light on the potential applications of the magnetoliposomes. The phase transition temperature(Tm) of lipid bilayer was decreased due to the disordered membrane microstructure. The hydrophobic MNPs improved the encapsulation efficiency of MLs, because the portion of large unilamelar vesicle with higher encapsulation efficiency was enlarged. The hydrophobic MNPs exhibited superparamagnetic behavior with zero coercivity and zero remanence. As a result, they showed high and controllable magnetic responses. Cargo can be released from MLs by two triggered agents, temperature and alternating current electromagnetic field (AMF). The content release from liposomes could be triggered when the temperature was higher than Tm. The cargo could be repetitively released from liposomes controlled by switching on and off the AMF. The results indicated that the release from the liposomes is due to the magnetocaloric effect resulting in the liposome phase transition and the magnetic-impelled motions leading to the improved bilayer permeability, rather than the destruction of the liposome structure.The results of this study enriches the research of magnetoliposomes at home and abroad, and they make a useful exploration in the development of magnetoliposomes.