Maltodextrins functionalised with pyrrolidine nitroxides: Synthesis and in vivo follow-up by magnetic resonance imaging

Maltodextrins (MDs) are polysaccharides derived from starch largely used in the food industry. MDs have high potentialities for the biomedical applications, and for this reason they have been employed for the development of smart polymeric materials for the drugs delivery. However, their direct application in vivo is still unexplored. In this work two MDs of different molecular weights were functionalized with pyrrolidine nitroxides (GL2-nitr, M_w ≈ 425 kDa and GL17-nitr, M_w ≈ 64 kDa). The content of radicals in the final samples was estimated by electron paramagnetic resonance (EPR) spectroscopy (≈0.38 mmol g^-1 for GL2-nitr and 0.54 mmol g^-1 for GL17-nitr). The introduction of nitroxide units on the MD backbone allowed to increase the T₁ relaxivity of the final compounds (≈0.11-0.13 mL mg^-1 s^-1). In vitro tests carried out on HaCaT, NIH/3 T3 and HK-2 cell lines showed the good cytocompatibility of GL2-nitr and GL17-nitr. Moreover, these compounds did not show a significant haemolytic activity. Finally, the nitroxide-labelled MDs were tested in vivo on mice, where their biodistribution was followed by magnetic resonance imaging (MRI). No acute adverse effects were observed during the experiments on the animals.