Development of a biocompatible magnetic nanofluid by incorporating SPIONs in Amazonian oils André S. Gaspar a,b , Friedrich E. Wagner c , Vítor S. Amaral d , Sofia A. Costa Lima e , Vladimir A. Khomchenko a , Judes G. Santos f , Benilde F.O. Costa a , Luísa Durães b, ⁎ a CFisUC, Physics Department, University of Coimbra, 3004–516 Coimbra, Portugal b CIEPQPF, Department of Chemical Engineering, University of Coimbra, 3030–790 Coimbra, Portugal c Physics Department, Technical University of Munich, 85747 Garching, Germany d Physics Department and CICECO, University of Aveiro, 3810–193 Aveiro, Portugal e UCIBIO-REQUIMTE, Department of Chemistry, Faculty of Pharmacy, University of Porto, 4050–313 Porto, Portugal f Federal University of Rondônia-UNIR, Faculty of Medicine, Laboratory of Nanomaterials and Nanobiomagnetism, CEP 76900–000, Amazonia, Brazil abstract article info Article history: Received 14 November 2015 Received in revised form 1 March 2016 Accepted 8 April 2016 Available online xxxx Higher quality magnetic nanoparticles are needed for use as magnetic nanoprobe in medical imaging techniques and cancer therapy. Moreover, the phytochemistry benefits of some Amazonian essential oils have sparked great interest for medical treatments. In this work, a magnetic nanoprobe was developed, allying the biocompatibility and superparamagnetism of iron oxide nanoparticles (SPIONs) with benefits associated with Amazonian oils from Copaiba and Andiroba trees. SPIONs were obtained by two thermal decomposition procedures and different amounts of precursors (iron acetylacetonates). Their characterization was accomplished by Fourier transform in- frared spectroscopy, thermogravimetric analysis, transmission electron microscopy (TEM), X-ray diffraction (XRD), Mössbauer spectroscopy and magnetization. The obtained nanoparticles composition and magnetic prop- erties were not affected by the relative proportion of iron(II) and iron(III) in the precursor system. However, when changing the reducing and stabilizing agents the coating layer shows different compositions/relative weight — the more promising SPIONs have a coating mainly composed by oleylamine and an iron oxide:coating wt% ratio of 55:45. Nanoparticles size distributions were very narrow and centred in the average size of 6–7 nm. Cellular assays confirmed the biocompatibility of SPIONs and their effective internalization in human colon can- cer cells. Mössbauer/XRD results indicated maghemite as their main iron oxide phase, but traces of magnetite proved to be present. Magnetization saturations of 57 emu/g at 5 K and 42 emu/g at 300 K were achieved. With incorporation of SPIONs into Copaiba and Andiroba essential oils, these values show a 4-fold decrease, but the supermagnetic behaviour is preserved providing the effective formation of a nanofluid. © 2016 Elsevier B.V. All rights reserved. Keywords: SPION Biocompatible magnetic nanoprobe Amazonian oil Mössbauer spectroscopy X-ray diffraction VSM 1. Introduction The ability to control and drive nanoparticles through the human bloodstream to a specific target by using an external magnetic field is of great interest to biomedical applications [1–3]. The superparamagnetic iron oxide nanoparticles (SPIONs) are a common choice for this purpose. Their superparamagnetism renders them the ability of behaving like a giant paramagnetic atom, granting a fast response to applied magnetic fields with negligible reminiscence and coercivity; it also diminishes the risk of agglomeration [1]. Moreover, SPIONs are usually biocompatible and non-toxic and other characteristics can be added to make them have a broader use. Because of their instability towards oxidation, SPIONs commonly have a protective shell against degradation. This shell may be used to bind specific drugs, proteins, enzymes, antibodies, etc., which can be delivered or may interact at targeted body sites [2]. The use of SPIONs can also greatly increase sensitivity needed to achieve high spatial resolu- tion in magnetic resonance imaging (MRI) [2]. Finally, SPIONs have shown promising results for cancer treatment by hyperthermia [3]. Magnetite (Fe 3 O 4 ) is the preferred iron oxide phase for SPIONs, due to its higher magnetization saturation. It shows ferrimagnetic behaviour when in coarse size and superparamagnetic behaviour below 6 nm [4]. At room temperature (RT), magnetite exhibits a face-centred cubic lattice, with an inverse spinel structure, being the tetrahedral sites (A sites) occupied by Fe 3+ and the octahedral sites (B sites) distributed between Fe 2+ and Fe 3+ [4]. Below the Verwey transition temperature (120 K), the trivalent and divalent iron atoms arrange themselves in a regular pattern giving rise to a normal spinel structure [4]. The mixed valence of iron in magnetite makes it thermodynamically unstable at atmospheric O 2 pressure and, thus, susceptible to oxidation, forming maghemite [5]. The iron oxide intermediates obtained through this process show decreasing amount of Fe 2+ in its composition, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy xxx (2016) xxx–xxx ⁎ Corresponding author. E-mail address: luisa@eq.uc.pt (L. Durães). SAA-14385; No of Pages 12 http://dx.doi.org/10.1016/j.saa.2016.04.022 1386-1425/© 2016 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa Please cite this article as: A.S. Gaspar, et al., Development of a biocompatible magnetic nanofluid by incorporating SPIONs in Amazonian oils, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy (2016), http://dx.doi.org/10.1016/j.saa.2016.04.022