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Ultrasmall superparamagnetic iron oxide: characterization of a new class of contrast agents for MR imaging.
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1990
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NanoparticlesContrast AgentsMagnetic PropertiesEngineeringBlood Half-lifeImaging AgentMagnetic ResonanceBiomedical EngineeringMagnetic MaterialsFerrofluidMagnetic Resonance ImagingOxidative StressMagnetismNanomedicineImaging AgentsUspio ParticlesClinical ChemistryRadiologyMedical ImagingNeuroimagingVascular BiologyContrast AgentPharmacologyIntravenous Contrast AgentBiomedical ImagingNew ClassNano-drug DeliveryMedicineMr Imaging
The authors developed an ultrasmall superparamagnetic iron oxide (USPIO) capable of crossing capillary walls, aiming to serve as a lymphatic, bone marrow, long‑half‑life perfusion, and organ‑targeted MRI contrast agent. USPIO particles are engineered to be ultrasmall, enabling migration across capillary walls—a prerequisite for targetable particulate pharmaceuticals. USPIO particles are predominantly <10 nm (70 %) and <5 nm (26 %), exhibit an 81‑minute blood half‑life in rats—much longer than larger SPIOs—transmigrate capillary walls via vesicular transport and interendothelial junctions, and accumulate 3.6 % ID/g in lymph nodes, 2.9 % in bone marrow, 6.3 % in liver, and 7.1 % in spleen after 24 h.
An ultrasmall superparamagnetic iron oxide (USPIO) preparation was developed that is small enough to migrate across the capillary wall, a prerequisite in the design of targetable particulate pharmaceuticals. Seventy percent of particles were smaller than 10 nm; 26%, smaller than 5 nm. The blood half-life of USPIO in rats was 81 minutes, considerably longer than that of larger superparamagnetic iron oxide preparations such as AMI-25 (6 minutes). Electron microscopy demonstrated that USPIO particles transmigrate the capillary wall by means of vesicular transport and through interendothelial junctions. Twenty-four hours after intravenous administration, 3.6% of the injected dose per gram of tissue was found in lymph nodes, 2.9% per gram in bone marrow, 6.3% per gram in liver, and 7.1% per gram in spleen. The major potential applications for USPIO are as (a) an intravenous contrast agent for the lymphatic system, (b) a bone marrow contrast agent, (c) a long-half-life perfusion agent for brain and heart, and (d) the magnetic moiety in organ-targeted superparamagnetic contrast agents for magnetic resonance imaging.