Magnetic resonance of polyaspartic acid-coated magnetite nanoparticles administered in mice

Molecular-coated magnetic nanoparticles (MNPs) have attracted a lot of attention, not only because of their unusual properties but also due to their potential biomedical applications. Preliminary genetic and toxicity tests with a magnetic fluid (MF) sample based on magnetite nanoparticles surface-coated with polyaspartic acid (PAMF) showed reasonable biocompatibility. Nevertheless, biodistribution aspects of PAMF sample were not investigated yet. In the present study PAMF was given as an intravenous bolus dose to mice, while magnetic resonance and light microscopy were used to investigate biodistribution parameters. The magnetic resonance (MR) spectra revealed a broad single line around g = 2, typical of magnetic nanoparticles (MNPs) suspended in a nonmagnetic matrix. All samples collected from the liver, spleen and lung presented similar MR spectra with no visible multiple features. Control tissue samples showed no resonance signal. MR analysis revealed that 10 minutes after injection the highest concentrations of PAMF nanoparticles were in the liver and blood. Nevertheless, at 60 minutes the highest concentrations of PAMF nanoparticles were in spleen and lung. PAMF signals were not detected in the blood 30 minutes after PAMF injection. In accordance with MR data, light microscopy analysis showed the presence of MNP clusters in the spleen, liver, and lungs. Nevertheless, in spite of the presence of MNP clusters in the organs, no morphological alterations or inflammatory process were observed. Several data on literature show that aspartic acid may effectively inhibit the tumor cell growth or increase the antitumor activities of several chemotherapeutic drugs. Taken together these data indicate that MNPs surface-treated with polyaspartic acid may be considered as a potential precursor of anticancer drugs.