Читать книгу Nanopharmaceutical Advanced Delivery Systems - Группа авторов - Страница 47

Iron oxide nanoparticles are nanoplatforms prepared from magnetite (Fe₃O₄), maghemite (γ-Fe₂O₃), and mixed ferrites (MFe₂O₄ where M = Co, Mn, Ni, or Zn). Iron oxide nanoparticles with particle size less than 200 nm are superparamagnetic, i.e., the particles become magnetized only when there is an external magnetic field. SPIONs are versatile moieties having potential applications in the field of diagnostics and drug delivery. Superparamagnetic iron oxide nanoparticles (SPIONs) are a material of choice as contrast probes for magnetic resonance imaging, and for these applications, coating is done with poly(ethylene glycol) (PEG), poly(vinyl alcohol) (PVA), or natural polysaccharides (dextran and modified chitosan) to provide long shelf lives to these systems. For targeting specific tissues, SPIONS are coupled with antibodies or aptamers and can even be surface-coated with gold and gadolinium ions to enhance the contrasting potential [65]. Nanoparticles with hydrodynamic diameter in the range of 50–150 nm accumulate fast in the mononuclear phagocyte system and can thus be used for liver imaging purposes. For imaging purposes, Ferumoxsil (Lumirem (USA), GastroMARK (EU)) is the only FDA-approved iron oxide nanoparticle. SPIONs coupled with anti-mesothelin antibodies have been studied for targeting pancreatic carcinoma cells and showed no cytotoxicity and high specificity as MRI contrast agents. Similarly, increase in the antitumor immune response was observed with SPIONs coated with membrane Heat Shock Protein 70 (mHSP70) expressed highly on the glioma cells’ surface [66]. Primovist^®, gadolinium-based contrast agents, show specific uptake by hepatocytes instead of macrophages and are specifically used for hepatocellular carcinoma (HCC) detection. Other contrast agents like Ferumoxtran (Combidex^® (USA), Sinerem^® (EU)) and ferumoxytol (Feraheme^® (USA), Rienso^® (EU)) are in clinical trials for lymph node imaging to examine metastatic colonization [67]. By using iron oxide nanoparticles in magnetic particle imaging (MPI), the background noise is reduced drastically, and thus imaging of vascular and cardiac perfusion, as well as cardiac procedures, can be successfully monitored by MPI.

The SPIONs can also be used in magnetic hyperthermia by application of AMF (alternating magnetic field), which results in change of iron’s magnetization against some resistance forces, thereby releasing heat to the environment. Hyperthermia can be used for stand-alone cancer therapy or as an adjuvant in chemotherapy or radiotherapy [68]. The use of SPIONs as drug carriers is also being studied after modifying hydrophilicity of these nanoparticles with suitable polymers like PEG, PEI (poly(ethylenimine)) [69], PLGA [70], etc. Further, their use as drug carriers can be enhanced by addition of functional groups in order to modify drug release or target binding properties [69].