We investigated the bio-distributions of [125 I]Spiro-I formulated in sterically stabilized liposomes （SSL） or targeted liposomes （SSTL） in mice,especially their brain uptake.The [125 I]Spiro-I liposomes were prepared by film-ultrasound dispersion method.Cereport （RMP-7） was covalently conjugated with DSPE-PEG,which was attached to the surface of SSL to form SSTL.The encapsulation efficiencies （ee%） of [125 I]Spiro-I-SSL and [125 I]Spiro-I-SSTL were 97.47%±4.01% and 93.02%±2.98%,respectively.The average particle sizes were （66.47±0.76） nm and （71.40±0.45） nm,respectively.After intravenous administration,[125 I]Spiro-I was quickly eliminated from blood.SSL could prolong the retention time of [125 I]Spiro-I in blood and SSTL improved its brain uptake.The AUC of [125 I]Spiro-I-SSTL in brain was increased by 1.52 times as compared to [125 I]Spiro-I,indicating that SSTL could be used for the formulation of [125 I]Spiro-I for the imaging of central nervous system （CNS）.
