Anti-CEA loaded maghemite nanoparticles as a theragnostic device for colorectal cancer

Mariana Campos da Paz,¹ Maria de Fátima M Almeida Santos,¹ Camila MB Santos,² Sebastião W da Silva,² Lincoln Bernardo de Souza,³ Emília CD Lima,³ Renata C Silva,¹ Carolina M Lucci,¹ Paulo César Morais,² Ricardo B Azevedo,¹ Zulmira GM Lacava<sup>1

1</sup>Instituto de Ciências Biológicas; ²Instituto de Física, Universidade de Brasília, Brasília, DF, Brazil; ³Instituto de Química, Universidade Federal de Goiás, Goiânia, GO, Brazil

Abstract: Nanosized maghemite particles were synthesized, precoated (with dimercaptosuccinic acid) and surface-functionalized with anticarcinoembryonic antigen (anti-CEA) and successfully used to target cell lines expressing the CEA, characteristic of colorectal cancer (CRC) cells. The as-developed nanosized material device, consisting of surface decorated maghemite nanoparticles suspended as a biocompatible magnetic fluid (MF) sample, labeled MF-anti-CEA, was characterized and tested against two cell lines: a high-CEA expressing cell line (LS174T) and a low-CEA expressing cell line (HCT116). Whereas X-ray diffraction was used to assess the average core size of the as-synthesized maghemite particles (average 8.3 nm in diameter), dynamic light scattering and electrophoretic mobility measurements were used to obtain the average hydrodynamic diameter (550 nm) and the zeta-potential (−38 mV) of the as-prepared and maghemite-based nanosized device, respectively. Additionally, surface-enhanced Raman spectroscopy (SERS) was used to track the surface decoration of the nanosized maghemite particles from the very first precoating up to the attachment of the anti-CEA moiety. The Raman peak at 1655 cm⁻¹, absent in the free anti-CEA spectrum, is the signature of the anti-CEA binding onto the precoated magnetic nanoparticles. Whereas MTT assay was used to confirm the low cell toxicity of the MF-anti-CEA device, ELISA and Prussian blue iron staining tests performed with both cell lines (LS174T and HCT116) confirm that the as-prepared MF-anti-CEA is highly specific for CEA-expressing cells. Finally, transmission electron microscopy analyses show that the association with anti-CEA seems to increase the number of LS174T cells with internalized maghemite nanoparticles, whereas no such increase seems to occur in the HCT116 cell line. In conclusion, the MF-anti-CEA sample is a biocompatible device that can specifically target CEA, suggesting its potential use as a theragnostic tool for CEA-expressing tumors, micrometastasis, and cancer-circulating cells.

Keywords: magnetic nanoparticles, anti-CEA antibody, targeted delivery, diagnostic, Raman, biocompatible device

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