Journal of Magnetism and Magnetic Materials 252 (2002) 396–398 A double-coated magnetite-based magnetic fluid evaluation by cytometry and genetic tests M.L.L. Freitas a , L.P. Silva a , R.B. Azevedo a , V.A.P. Garcia a , L.M. Lacava a , C.K. Gris ! olia a , C.M. Lucci a , P.C. Morais b , M.F. Da Silva b , N. Buske c , R. Curi d , Z.G.M. Lacava a, * a Dept. de Genetica e Morfologia, Instituto de Ci # encias Biol ! ogicas, Universidade de Bras ! ılia, 70910-900 Bras ! ılia-DF, Brazil b Instituto de F! ısica, Universidade de Bras ! ılia, C.P. 04455, 70919-970 Bras ! ılia-DF, Brazil c Berlin Heart AG, Wiesenweg 10, D-12247 Berlin, Germany d Instituto de Ci # encias Biol ! ogicas, Universidade de S * ao Paulo, 05508-900 S * ao Paulo-SP, Brazil Abstract Magnetite nanoparticles pre-coated with dodecanoic acid and ethoxylated alcohol (DE) were used to obtain a physiologically stable magnetic fluid (DE–MF) sample. Three different doses of DE–MF were intraperitoneally applied to mice. Blood and peritoneum cytometry and micronucleus test were performed for 1–21 days after injection to investigate the DE–MF toxicity. Changes in cell population, peritoneum inflammation, and potential DE–MF genotoxic action were all time and dose dependent. At the lowest dose (5  10 15 particles/kg), DE–MF seems to be useful as a drug precursor with both diagnostic and therapeutic values. r 2002 Elsevier Science B.V. All rights reserved. Keywords: Biocompatibility; Cytometry; Magnetic fluid; Magnetite; Micronucleus Magnetic fluids (MFs) are stable colloidal suspensions composed of magnetic nanoparticles (MNPs) dispersed in organic or inorganic liquid carriers. In order to be used for biomedical purposes, MNPs must be pre-coated with substances that let them stable, biodegradable, and non-toxic in physiological medium. After pre-coating, biological effectors can be adsorbed at the MNP surface to produce biocompatible materials with specific biomedical applications. However, the drawback that mostly concerns the wide use of the biocompatible MF technology is the possibility of biological effector desorption from the MNP surface and the biological effects of the pre-coated MNP alone. The present study reports on several in vivo biological tests carried out with a water-based MF containing magnetite nanoparticles obtained by chemical co-pre- cipitation of Fe (II) and Fe (III) ions in alkaline medium. After precipitation the nanoparticles were pre-coated with dodecanoic acid followed by an ethoxylated polyalcohol (DE) to obtain a stable DE– MF sample developed as a precursor of anticancer drug [1]. Previous results showed an average core particle diameter of 9.4 nm [2] and grafting coefficients of 10 11 and 10 12 mol/cm 3 for the inner and outer shell, respectively [3]. Six different groups of female Swiss mice (n ¼ 5) were studied: control animals were not treated (Group 1) or treated either with 0.002M ethoxylated alcohol (Group 2) or with 0.002 M ethoxy- lated alcohol plus 0.002 M dodecanoic acid (Group 3). Experimental groups were intraperitoneally treated with a bolus dose of the DE–MF sample containing about 5  10 15 (Group 4), 5  10 16 (Group 5) or 5  10 17 (Group 6) particles/kg. Blood and peritoneum cytome- try experiments were carried out 1, 7, 14, and 21 days after DE-MF application using the methodology pre- viously described [4]. The results were analyzed by the statistical Scheffe test (ANOVA, po0:05). The micro- nucleus (MN) test was performed 24h after MF application to evaluate the DE–MF genotoxic and *Corresponding author. Fax: +55-61-3072963. E-mail address: zulmira@unb.br (Z.G.M. Lacava). 0304-8853/02/$-see front matter r 2002 Elsevier Science B.V. All rights reserved. PII:S0304-8853(02)00655-8