RT Journal Article SR Electronic T1 Synthetic Lipid Nanoparticles Targeting Steroid Organs JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 1996 OP 2003 DO 10.2967/jnumed.113.121657 VO 54 IS 11 A1 Juliette Mérian A1 Raphaël Boisgard A1 Xavier Decleves A1 Benoît Thezé A1 Isabelle Texier A1 Bertrand Tavitian YR 2013 UL http://jnm.snmjournals.org/content/54/11/1996.abstract AB Lipidots are original nanoparticulate lipid delivery vectors for drugs and contrast agents made from materials generally regarded as safe. Here, we characterized the in vivo stability, biodistribution, and pharmacokinetics of lipidots. Methods: Lipidots 55 nm in diameter and coated with a phospholipid/poly(ethyleneglycol) surfactant shell were triply labeled with 3H-cholesteryl-hexadecyl-ether, cholesteryl-14C-oleate, and the 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindotricarbocyanine infrared fluorescent dye and injected intravenously into immunocompetent Friend virus B–type mice. The pharmacokinetics and biodistribution of lipidots were analyzed quantitatively in serial samples of blood and tissue and with in vivo optical imaging and were refined by microscopic examination of selected target tissues. Results: The plasmatic half-life of lipidots was approximately 30 min. Radioactive and fluorescent tracers displayed a similar nanoparticle-driven biodistribution, indicative of the lipidots’ integrity during the first hours after injection. Lipidots distributed in the liver and, surprisingly, in the steroid-rich organs adrenals and ovaries, but not in the spleen. This tropism was confirmed at the microscopic level by histologic detection of 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindotricarbocyanine. Nanoparticle loading with cholesterol derivatives increased accumulation in ovaries in a dose-dependent manner. Conclusion: This previously unreported distribution pattern is specific to lipidots and attributed to their nanometric size and composition, conferring on them a lipoproteinlike behavior. The affinity of lipidots for steroid hormone–rich areas is of interest to address drugs and contrast agents to lipoprotein-receptor–overexpressing cancer cells found in hormone-dependent tumors.