Physical Chemistry and in Vivo Tissue Heating Properties of Colloidal Magnetic Iron Oxides with Increased Power Absorption Rates
Superparamagnetic colloidal magnetic iron oxides (CMIO) are non-toxic, biocompatible, injectable agents that dissipate the energy of radiofrequency electromagnetic fields in the form of heat and therefore may be useful in providing local hyperthermic treatment of tumors. CMIO with greatly enhanced specific power absorption rates (SAR > 400 watts/gm Fe at I MHz, 100 Oersted) were synthesized with optimized procedures. These high-SAR CMIO have a peculiar spatial organization of magnetic grains around the polymer matrix with an unique dextran/iron ratio of 0.1–0.5 by weight, high values of initial magnetic susceptibilities and magnetic moments, which all contribute and correlate strongly with the high heat production properties. In vivo local hyperthermia at concentrations as low as 0.5 to 1 mg Fe/gm of tumor tissue can be easily achieved with these high-SAR CMIO with low non-specific heating of normal surrounding tissues.
KeywordsMagnetic Fluid Eddy Current Loss Localize Hyperthermia Magnetic Microparticle Residual Loss
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