P‐selectin dependent targeting to inflamed endothelium of recombinant P‐selectin glycoprotein ligand‐1 immunoglobulin chimera‐coated poly[N‐(2‐hydroxypropyl) methacrylamide]‐DNA polyplexes in vivo visualised by intravital microscopy

Background Developing vectors that target specifically to disease sites after systemic injection is an important goal in gene therapy research. Methods We prepared fluorescent DNA polyplexes (⩽150 nm in diameter) comprising plasmid DNA condensed with poly(L-lysine) and coated with a multivalent reactive copolymer based on poly[N-(2-hydroxypropyl)methacrylamide] (pHPMA). These polyplexes were then surface modified with a recombinant P-selectin glycoprotein ligand-1 immunoglobulin chimera (rPSGL-Ig) previously investigated as a selectin antagonist in clinical studies. Results Five minutes after jugular vein injection of these polyplexes, fluorescence accumulation in inflamed cremasteric venules of C57BL6 mice was more than eight-fold higher than that observed after injection of Fc-blocked control polyplexes. Fluorescence above background was not observed in P-selectin deficient mice, confirming the specificity for P-selectin in this model. Conclusions These data provide encouragement for the further development of rPSGL-Ig-coated polyplexes as potential nonviral vectors for targeted gene therapy in inflammatory conditions, such as ischaemia reperfusion injury, unstable atherosclerotic plaques and myocarditis. This approach may also be transferable to the use of other targeting ligands whose cognate partner is specifically upregulated on the vascular endothelium in individual pathological situations. Copyright © 2009 John Wiley & Sons, Ltd.