Synthesis and characterization of polyethylenimine-based iron oxide composites as novel contrast agents for MRI.
OBJECTIVE
Use of polyethylenimines (PEIs) of different molecular weight and selected carboxylated-PEI derivatives (PEI-COOH) in the synthesis and stabilization of iron oxide nanoparticles, to obtain possible multifunctional contrast agents.


METHODS
Oxidation of Fe(II) at slightly elevated pH and temperature resulted in the formation of highly soluble and stable nanocomposites of iron oxides and polymer. Composites were characterized and studied by atomic force microscopy (AFM), transmission electron microscopy (TEM), X-ray diffractometry, AC and DC magnetometry, NMR relaxometry and magnetic resonance imaging (MRI).


RESULTS
From AFM the dimensions of the aggregates were found to be in the ~150-250 nm size region; the mean diameter of the magnetic core of the compounds named PEI-25, PEI-500 and PEI-COOH60 resulted d approximately 20 +/- 5 nm for PEI-25, d approximately 9.5 +/- 1.0 nm for PEI-500 and d approximately 6.8 +/- 1.0 nm for PEI-COOH60. In PEI-COOH60 TEM and X-ray diffractometry revealed small assemblies of mineral magnetic cores with clear indications that the main constituents are maghemite and/or magnetite as confirmed by AC and DC SQUID magnetometry. For PEI-COOH60, the study of NMR-dispersion profiles revealed r (1) and r (2) relaxivities comparable to superparamagnetic iron-oxide commercial compounds in the whole investigated frequency range 7 < or = nu < or = 212 MHz.


CONCLUSIONS
PEI-25 was studied as possible MRI contrast agent (CA) to map the cerebral blood volume (CBV) and cerebral blood flow (CBF) in an animal model obtaining promising results. The reported compounds may be further functionalized to afford novel multifunctional systems for biomedical applications.
Dipartimento di Chimica, SAPIENZA Università di Roma, P.le A.Moro 5, 00185 Rome, Italy. andrea.masotti@uniroma1.it
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Masotti
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Pitta
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Ortaggi
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Corti
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Innocenti
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Lascialfari
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Marinone
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Marzola
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Daducci
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Sbarbati
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Micotti
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Orsini
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Poletti
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Sangregorio
D000818:Animals; D001921:Brain / Q000033:anatomy & histology*; D003287:Contrast Media / Q000737:chemistry; D005290:Ferric Compounds / Q000737:chemistry*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D011094:Polyethyleneimine / Q000737:chemistry*; D051381:Rats; D013194:Staining and Labeling / Q000379:methods
D003287:Contrast Media; D005290:Ferric Compounds; C000499:ferric oxide; D011094:Polyethyleneimine