SPIONnanopartikkeleiden

SPIONs (superparamagnetic iron oxide nanoparticles) are nanoscale particles composed of iron oxide that exhibit superparamagnetism when small enough. The core is typically magnetite (Fe3O4) or maghemite (γ-Fe2O3), with diameters commonly in the 5–50 nm range. To enable stability in biological environments and to provide functional handles for further modification, the core is coated with polymers (such as dextran, carboxymethyl dextran, or PEG), silica, or other inorganic shells.

In magnetic resonance imaging, SPIONs act as T2 and T2*-shortening agents, generating dark signals in T2-weighted images and improving contrast. Their properties and coatings influence biodistribution, clearance, and immunogenicity. Some dextran-coated formulations were approved historically but later withdrawn or restricted; current work emphasizes alternative coatings and dosing strategies.

Beyond imaging, SPIONs are investigated for magnetic hyperthermia, in which alternating magnetic fields induce localized heating to kill cancer cells. They are also explored as vehicles for targeted drug delivery, with surface ligands directing particles to tumor markers, and as components in biosensors and magnetic separation techniques.

Synthesis methods influence size, uniformity, and surface functionality. Common approaches include co-precipitation of iron salts in basic solution, which is scalable but can yield broader size distributions, and thermal decomposition, which provides narrow distributions at higher temperatures but with more complex processing. Surface modification enables biocompatibility, colloidal stability, and conjugation of targeting ligands, dyes, or therapeutic agents.

Safety and regulatory considerations center on biocompatibility, biodegradation, and potential iron overload or oxidative stress. In vivo fate typically involves uptake by the reticuloendothelial system, especially liver and spleen, followed by iron metabolism pathways. Side effects can arise from surface coatings or impurities; as a result, regulatory approval varies by jurisdiction and product, with ongoing research to address long-term safety and clinical efficacy.