title: In vitro and in vivo platelet targeting by cyclic RGD-modified liposomes.
abstract: Cell-selective delivery using ligand-decorated nanoparticles is a promising modality for treating cancer and vascular diseases. We are developing liposome nanoparticles surface-modified by RGD peptide ligands having targeting specificity to integrin GPIIb-IIIa. This integrin is upregulated and stimulated into a ligand-binding conformation on the surface activated platelets. Activated-platelet adhesion and aggregation are primary events in atherosclerosois, thrombosis, and restenosis. Hence, platelet-targeted nanoparticles hold the promise of vascular site-selective delivery of drugs and imaging probes. Here, we report in vitro and ex vivo microscopy studies of platelet-targeting by liposomes surface-modified with a cyclic RGD peptide. The peptide-modified liposomes were labeled either with a lipophilic fluorophore or with lipid-tethered Nanogold(R). For in vitro tests, coverslip-adhered activated human platelets were incubated with probe-labeled liposomes, followed by analysis with fluorescence microscopy, phase contrast microscopy, and scanning electron microscopy (SEM). For in vivo tests, the liposomes were introduced within a catheter-injured carotid artery restenosis model in rats and post-euthanasia, the artery was imaged ex vivo by fluorescence microscopy and SEM. All microscopy results showed successful platelet-targeting by the peptide-modified liposomes. The in vitro SEM results also enabled visualization of nanoscopic liposomes attached to activated platelets. The results validate our nanoparticle design for site-selective vascular delivery.
authors.affiliation: Department of Biomedical Engineering, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio 44106, USA.
authors.forename: Rekha
authors.initials: R
authors.lastname: Srinivasan
authors.forename: Roger E
authors.initials: RE
authors.lastname: Marchant
authors.forename: Anirban Sen
authors.initials: AS
authors.lastname: Gupta
mesh_terms: D000818:Animals; D001792:Blood Platelets / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism* / Q000648:ultrastructure; D002339:Carotid Arteries / Q000187:drug effects / Q000473:pathology; D004195:Disease Models, Animal; D016503:Drug Delivery Systems / Q000379:methods*; D005434:Flow Cytometry; D006801:Humans; D008081:Liposomes / Q000494:pharmacology*; D008856:Microscopy, Fluorescence; D049329:Nanostructures / Q000737:chemistry; D010456:Peptides, Cyclic / Q000494:pharmacology*; D051381:Rats
chemical_list: D008081:Liposomes; D010456:Peptides, Cyclic; C507169:cyclic arginine-glycine-aspartic acid peptide