Received for publication July 2, 2004.
Revised December 10, 2004.
Accepted for publication December 10, 2004.

Optimized targeting of PEG-stabilized anti-ICAM-1 ODN/lipid particles to liver sinusoidal endothelial cells

Abstract

We prepared poly (ethylene glycol) (PEG)-stabilized antisense oligonucleotide (ODN)/lipid particles from a lipid mixture including the positively charged amphiphile DOTAP, and anti-ICAM-1 antisense ODN, by an extrusion method in the presence of 40 % ethanol. These particles were targeted to scavenger receptors on liver endothelial cells by means of covalently coupled polyanionized albumin. Two types of such targeted particles were prepared. One with the albumin coupled to a maleimide group attached to the particle's lipid bilayer, and the other with the protein coupled to a maleimide group attached at the distal end of, additionally added, bilayer-anchored PEG chains. Upon intravenous injection, the ODN particles with bilayer-coupled albumin were cleared from the blood circulation at the same low rate as untargeted particles (< 5 % in 30 min). By contrast, the distal-end coupled particles were very rapidly cleared from the blood and preferentially taken up by the endothelial cells of the hepatic sinusoid (55 % of injected dose after 30 min). In spite of this substantial endothelial targeting no consistent inhibition of ICAM-1 expression could be demonstrated in this cell type, either in vivo or in vitro. However, in J774 cells, that also express scavenger receptors and ICAM-1, significant downregulation of ICAM-1 mRNA was achieved with distal-end targeted lipid particles, as determined with real-time RT-PCR. It is concluded that massive delivery of ODN to cells types that express scavenger receptors can be achieved if lipid particles are provide with negatively charged albumin distally attached to bilayer anchored PEG chains.

Key words: Liposome, Receptor-mediated, Antisense, Metastasis