Accumulation of fibrinogen-coated microparticles at a fibrin(ogen)-rich inflammatory site

We have developed methods for coating with fibrinogen both liposomes and mi croscopic droplets of olive oil. Because the fibrinogen bound to them is fu nctional in the classic sense of fibrin gelation, the coated microparticles may have potential as vehicles for the targeted delivery of various molecu les to sites of fibrin(ogen) deposition in vivo. So that we could assess di rectly this potential, we first established a method for eliciting reproduc ibly a focal, fibrin(ogen)-rich, inflammatory lesion in a hind footpad of m ice. We then monitored the tissue distribution of fibrinogen-coated micropa rticles following their injection into the tail vein of mice bearing this w ell-defined lesion. As happens with most microparticles following their int ravenous administration, liposomes and oil droplets, whether coated with fi brinogen or not, accumulate rapidly in the liver and spleen of treated anim als, Indeed, in the case of oil droplets, accumulation of fibrinogen-coated microparticles in those organs and in the lungs is even greater than that of fibrinogen-free microparticles, However, as distinct from fibrinogen-fre e liposomes and oil droplets, fibrinogen-coated microparticles also accumul ate in the inflamed hind footpad. We conclude that fibrinogen-coated liposo mes and oil droplets do have potential as vehicles for delivering molecules to sites of fibrin(ogen) deposition in vivo.