Decorated Magnetoliposomes: An Attractive Idea for Multifunctional Therapeutics

Liposomes, particles composed of a thin bilayer shell surrounding an aqueous core, have recently gained attention as a potential biomedical tool for diagnostic or therapeutic use. Hybridizing liposomes with bound or encapsulated nanoparticles could extend their range of functionality, leading to applications including hyperthermia treatments. Though drug delivery remains one of the most promising potential applications, it carries several challenges, including preventing leakage of cargo in circulation and controlling release upon arriving at the target site. In principle, decorating liposomes with bound nanoparticles then supplying selective and local heating to the bilayer could be used to control therapeutic delivery. To test this idea, Chen et al. (p 3215) looked to decorated magnetoliposomes (dMLs), a type of hybrid liposome/nanoparticle assembly. The researchers prepared dMLs of 5 nm Fe2O3 (maghemite) capped with oleic acid embedded within lipid bilayers, with various ratios of lipid molecules to nanoparticles. Cryogenic transmission electron microscopy showed that the loaded magnetoliposomes ranged in size from about 156 to 198 nm, with diameter increasing as the ratio of lipid molecule to nanoparticle increased. Tests with carboxyfluorescein showed that the liposomes became more stable and yielded less spontaneous leakage with increasing nanoparticle loading. When the researchers heated the dMLs using alternating-current electromagnetic fields operating under physiologically acceptable radio frequencies (RFs), they were able to release the fluorescent molecule selectively. Under RF heating, the initial rate and extent of leakage increased significantly as a function of nanoparticle loading and electromagnetic field strength. Though additional tests in vivo will be necessary, the researchers note that this system shows promise for therapeutic delivery.