A lipophilic complex with 186Re/188Re incorporated in liposomes suitable for radiotherapy

Liposomes with a 70 nm diameter were made by the detergent removal technique on a gel filtration column. The complex oxodichloroethoxy-bis-(triphenylphosphine)rhenium(V)=(Rephos) was irradiated by neutrons in the reactor at PSI. 45 +/ 5% of the radioactive complex was incorporated into the bilayer of the lipsomes during the liposome formation. The stablility of these radioactive liposomes was tested by dialysis: a loss of 40% of the radioactivity identified as perrhenate was observed after 8 days. Addition of the antioxidant ascorbic acid diminished the loss to 20%. Such liposomes carrying the lipophilic radioactive Re-complex can potentially be used in beta-radiotherapy. The gamma-lines of the two rhenium isotopes are helpful for localizing them in therapy controls by a gamma-camera, a big advantage compared to other nuclides proposed for therapy (e.g. 90Yttrium).