Formation and regulation of fullerene-incorporation in liposomes under the phase transition temperature

The fullerene-exchange reaction from a cyclodextrin cavity to liposomes represents one of the best methods to prepare lipid membrane-incorporated [70]fullerenes (C-70). The C-70-exchange reaction occurred completely at temperatures above the phase transition temperature (T-m) of the liposomes; however, lowering the temperature to below the T-m led to C-70 aggregation outside the liposomes. This observation has limited the development of more functional LMIC70 using a variety of liposome compositions. In this paper, this reaction was found to occur efficiently by the addition of small amounts of lipids bearing a pi-moiety. The pi-moieties act as a gate when hydrophobic C-70 migrates into the hydrophilic liposome surface. Therefore, the pi-moieties should exist in the polar head groups of the lipids and the C-70-exchange reaction can be controlled by pH.