Abstract: We investigated the bio-distributions of [¹²⁵I]Spiro-I formulated in sterically stabilized liposomes (SSL) or targeted liposomes (SSTL) in mice, especially their brain uptake. The [¹²⁵I]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 [¹²⁵I]Spiro-I-SSL and [¹²⁵I]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, [¹²⁵I]Spiro-I was quickly eliminated from blood. SSL could prolong the retention time of [¹²⁵I]Spiro-I in blood and SSTL improved its brain uptake. The AUC of [¹²⁵I]Spiro-I-SSTL in brain was increased by 1.52 times as compared to [¹²⁵I]Spiro-I, indicating that SSTL could be used for the formulation of [¹²⁵I]Spiro-I for the imaging of central nervous system (CNS).

Key words: [125I]Spiro-I, RMP-7, Liposome, Bio-distribution