INVESTIGATION OF THE INTERACTION BETWEEN MAGNETITE NANOPARTICLES SURFACE – COATED WITH CARBOXYMETHYLDEXTRAN

AND BLOOD CELLS USING RAMAN SPECTROSCOPY.

Santana J. F. B. ¹ , Soler M. A. G. ¹ , Silva S. W. ¹ , Morais P. C. ¹ ,

Guedes M. H. ² , Lacava Z. G. M. ²

1. Universidade de Brasilia, Instituto de Fisica, nucleo de Fisica Aplicada, C. P. 04455, 70919-970, Brasilia-DF, Brazil.

2. Universidade de Brasilia, Instituto de Ciencias Biologicas, Departamento de Genetica e Morfologia, 70910-900. Brasilia-DF, Brazil.

Magnetic nanoparticles offer many attractive possibilities for biomedical applications. Their typical sizes are smaller than or comparable to the size of a cell, a virus, a protein molecule, or a gene. These nanoparticles can be engineered by surface-coating them with special molecules to interact with or bind to a biological structure, thereby providing a controllable means of targeting specific biological sites. More specifically, magnetic nanoparticles surface-coated with organic molecules can be dispersed as a stable colloid in physiological medium, named biocomatible magnetic fluids, which may be used in magnetic cell separation, drug delivery carriers, hypothermia treatments, and magnetic resonance imaging contrast enhancement, among others. The drawback that mostly concerns the wide use of biocompatible magnetic fluids in new technologies is the possible adverse effect of foreign particles in the organism, In particular, the mechanism of interaction between the surface-coated magnetic nanoparticles and the blood components, as an example, is still not clearly elucidated.

This study reports on in vitro biological tests performed with a biocompatible magnetic fluid based on carboxymethyldextran-coated magnetite nanoparticle. The biocompatible magnetic fluid sample was developed with the purpose of actively targeting cells for diagnostic and therapeutic purposes [1]. Micro Raman spectroscopy was used to investigate the effect of dispersing carboxymethyldextran-coated magnetite nanoparticle in mice’s blood. The focus here is the use of the Raman spectroscopy for monitoring the hemoglobin structural changes, which may be associated with the oxygen-binding process or electron transfer mechanism. Blood aliquots were obtained by picture heart puncture from healthy mice and placed in glass tubes containing ethylendiamine tetra-acetate acid as an anticoagulant agent, and used afterwards as a reference sample. Fresh blood aliquots were also mixed with the biocompatible magnetic fluid, resulting in a series of blood-doped samples. Typical concentrations of the carboxymethyldextran-coated magnetite nanoparticle in the blood-doped samples range from 1 x 10 ¹³ to 1 x 10 ¹⁵ particle per cubic centimeter.

The Raman spectra of the reference and blood-doped samples were taken with the 514 nm Ar ⁺ laser excitation. The Raman spectra in the 1200 to 1700 cm – 1 region show the presence of bands, typical of the core-size band region (1500 – 1650 cm ^{– 1}) and pyrolle ring stretching region (1300 – 1400 cm ^{– 1}) [2]. Many of these bands are sensitive to changes in oxygenation or binding and are related to changes in conformation of the pyrrole ring system. The Raman spectra show the presence of four bands. In the oxyhaemoglobin species the Raman features appear at 1640 and 1587 cm ^{– 1}, whereas in the deoxyhaemoglobin species the Raman feature appear at 1607 and 1552 cm ^{– 1} [3]. Compared to the reference sample the blood-doped samples show Raman peaks with different peak intensities depending on the nanoparticle concentration. The Raman data will be discussed taking into account the level of the oxygen bounded to the hemoglobin species (oxyhaemoglobin and deoxyhaemoglobin) and the nanoparticle concentration in the blood-doped samples.

1. Hasegawa M., Hanaichi T., Shoji H., Kawaguchi T., Maruno S. // Jpn. J. Appl. Phys., 37 (1998) 1029.

2. Wood B. R., McNaughton D. // J. Raman. Spec., 33 (2002) 517.

3. Spiro T. G., Strekas T. C. // J. Am. Chem. Soc. 96 (1974) 338.