Preparation of liposomes containing small gold nanoparticles using electrostatic interactions

The development of liposome-nanoparticle colloid systems offers a versatile approach towards the manufactureof multifunctional therapeutic platforms. A strategy to encapsulate small metallic nanoparticles (< 4 nm) withinmultilamellar vesicles, effected by exploiting electrostatic interactions was investigated. Two liposome-goldnanoparticle (lipo-GNP) systems were prepared by the reverse-phase evaporation method employing cationic oranionic surface functionalised particles in combination with oppositely charged lipid compositions withsubsequent post-formulation PEGylation. Structural characterisation using electron microscopy and elementalanalysis revealed a regular distribution of GNPs between adjacent lipid bilayers of intact liposomes. Nanoparticleencapsulation efficacy of the two lipo-GNP systems was revealed to be significantly different (p=0.03),evaluated by comparing the ratio of measured lipid to gold concentration (loading content) determined by acolorimetric assay and atomic emission spectroscopy, respectively. It was concluded that the developed syntheticstrategy is an effective approach for the preparation of liposome-nanoparticle colloids with potential to controlthe relative concentration of encapsulated particles to lipids by providing favourable electrostatic interactions.