Lipid-Assisted Formation and Dispersion of Aqueous and Bilayer-Embedded Nano-C60

Lipid assemblies provide a biocompatible approach for preparing aqueous nanoparticles. In this work, dipalmitoyl-phosphatidylcholine (DPPC) was used to assist in the formation and dispersion Of C-60 and nano-C-60 aggregates using a modified reverse phase evaporation (REV) method. This method led to the rapid formation of aqueous nano-C-60 at DPPC/C-60 molar ratios from 500:1 to 100: 1 (12-38 nm; verified by cryogenic transmission electron microscopy), which were present in the bulk phase and encapsulated within vesicles. In addition to forming nanoparticles, C-60 was trapped within the vesicle bilayer and led to a reduction in the lipid melting temperature. Solvent extraction was used to isolate nano-C-60 from the lipids and bilayer-embedded C-60. Our results suggest that bilayer-embedded C-60 was present as molecular C-60 and as small amorphous nano-C-60 (2.3 +/- 0.4 nm), which clustered in the aqueous phase after the lipids were extracted. In addition to developing a new technique for nano-C-60 formation, our results suggest that the lipid bilayer may be used as a hydrophobic region for dispersing and assembling small nano-C-60.