Dextrin-Based Nanomagnetogel: In Vivo Biodistribution and Stability

The biodistribution profile of a new dextrin nanomagnetogel, which consists of γ-Fe₂O₃ superparamagnetic nanoparticles loaded within a polymeric matrix of modified dextrin, was studied in mice. The nanomagnetogel bear a monomodal size distribution profile (average diameter 110 nm) close to neutral surface charge and higher relaxivity (<i>r</i>₂ <i>=</i> 215–248 mM^–1 s^–1 and <i>r</i>₂/<i>r</i>₁ = 13–11) than those of commercial formulations (<i>r</i>₂ <i>=</i> 160–177 mM^–1 s^–1 and <i>r</i>₂/<i>r</i>₁ <i>=</i> 4–7). Also, the observed blood half-lifeapproximately 4 his superior to that of similar commercially available formulations, which remain for a few minutes in circulation. PEGylation resulted in 1.7- and 1.2-fold lower accumulation in the liver and spleen, respectively, within the first 24 h. Noteworthy, a good correlation was obtained between the amount of polymer (quantified by scintigraphy) in the spleen, 48 h after administration, and the amount of iron physically loaded through hydrophobic interactions (quantified by ICP) indicating the absence of iron leakage from the polymeric matrix. This study provides evidence of the in vivo stability of a self-assembled nanomagnetogel, a relevant feature which is seldom reported in the literature