[Preparation of 125I-oligonucleotide-long-circulation liposomes]

To investigate the preparation and the encapsulation efficiency of 125I-oligonucleotide(ON)-long-circulation liposomes (LCL).

(1) Oligonucleotide was labeled with 125I using thallium chloride tetrahydrate (TICl3) as an oxidizing agent. 125I-oligonucleotide was separated from free 125I by Sephadex G25 column chromatography. The following radiolabeling efficiency, radiochemistry purity and specific radioactivity were obtained respectively. Subsequently, the stability of 125I-ON was observed. (2) 125I-ON-LCL were prepared by means of reverse-phase evaporation. The quality of 125I-ON-LCL was evaluated after the crude LCL were repeatedly extruded through 400 nm, 200 nm, 100 nm polycarbonate membranes consecutively. Results (1) The radiolabeling efficiency, radiochemistry purity and specific radioactivity of 125I-antisense oigonucleotide (ASON) were (72.80 +/- 0.68)%, (98. 33 +/- 0.39)% and (0.63 +/- 0.11) MBq/microg; of 125I-sense oigonucleotide (SON) were (72.21 +/- 0.60)%, (98.28 +/- 0.36)%, (0.63 +/- 0.14) MBq/microg; and of 125I-nonsense oligonucleotide (NON) were (72.77 +/- 0.81)%, (98.42 +/- 0.40)%, (0.62 +/- 0.11) MBq/microg, respectively. (2) The radiochemistry purity of 125I-ON, in 0.01 mol/L HEPES buffer and human serum at 1 h, 2 h and 4 h were all above 93%, 80%, respectively. (3) LCL formulations were 115 nm in mean diameter with a PDI (polydispersibility index) of 0.103 and Zeta potential of -29.23. The encapsulation efficiencies of 125I-ASON, 125I-SON and 125I-NON were (66.21 +/- 0.21)%, (70.93 +/- 0.03)% and (67.67 +/- 0.10)% respectively.

LCL were prepared in high loading efficiency for 125I-ON with small particle sizes and symmetric distributions.