Materials Research. 2014; 17(3): 542-549 © 2014 DOI: http://dx.doi.org/10.1590/S1516-14392014005000050 Synthesis and Characterization of Fe3O4 Nanoparticles with Perspectives in Biomedical Applications Javier Bustamante Mamania*, Lionel Fernel Gamarraa,b,c, Giancarlo Espósito de Souza Britod aHospital Israelita Albert Einstein – HIAE, São Paulo, SP, Brazil bDepartamento de Neurologia e Neurocirurgia, Universidade Federal de São Paulo – UNIFESP, São Paulo, SP, Brazil cFaculdade de Ciências Médicas da Santa Casa de São Paulo – FCMSCSP, São Paulo, SP, Brazil dDepartamento de Física Aplicada, Instituto de Física – IF, Universidade de São Paulo – USP, São Paulo, SP, Brazil Received: February 27, 2013; Revised: December 5, 2013 Nowadays the use of magnetic nanoparticles (MNP) in medical applications has exceeded expectations. In molecular imaging, MNP based on iron oxide coated with appropriated materials have several applications in vitro and in vivo studies. For applications in nanobiotechnology these MNP must present some characteristics such as size smaller than 100 nanometers, high magnetization values, among others. Therefore the MNP have physical and chemical properties that are specific to certain studies which must be characterized for quality control of the nanostructured material. This study presents the synthesis and characterization of MNP of magnetite (Fe3O4) dispersible in water with perspectives in a wide range of biomedical applications. The characterization of the colloidal suspension based on MNP stated that the average diameter is (12.6±0.2) nm determined by Transmission Electron Microscopy where the MNP have the crystalline phase of magnetite (Fe3O4) that was identified by Diffraction X-ray and confirmed by Mössbauer Spectroscopy. The blocking temperature of (89±1) K, Fe3O4 MNP property, was determined from magnetic measurements based on the Zero Field Cooled and Field Cooled methods. The hysteresis loops were measured at different temperatures below and above blocking temperature. The magnetometry determined that the MNP showed superparamagnetic behavior confirmed by ferromagnetic resonance. Keywords: nanoparticles, iron oxide, synthesis, characterization, magnetite 1. Introduction The synthesis of magnetic nanoparticles (MNP) has of MNP in medical applications is mainly related to the received great interest in recent years because of new coating material, which are biocompatible, nontoxic and physical and chemical properties of materials at nanoscale. biodegradable. Among the commercial products based on Based on their mesoscopic physical, chemical, thermal and MNP, Endorem® and Lumirem® are used as contrast agents mechanical properties, and in conjunction with control of in MRI to the liver and intestine, respectively. size, composition and morphology of growth, the synthesis Several synthesis processes are used in the development of MNP lead to a wide range of specific technological of MNP. For this reason, the conditions of synthesis are applications1-4. crucial to determine the physicochemical properties of Among crystal polymorphs of iron (III) known, MNP such as concentration and pH of the solution as 11,12 magnetite (Fe3O4) is a promising candidate for its well as the mode of heat treatment used . The most biocompatibility and biodegradable activity5,6. Thus, important methods described in the literature to prepare iron oxide MNP with crystalline phase corresponding to MNP, which are suitable for biomedical applications13-16, magnetite appears as an important nanomaterial for various are: co-precipitation, microemulsions polyol process, high biomedical applications such as: (i) cellular therapy as cell temperature decomposition of organic precursors, assisted labeling, targeting, and as a tool for cell-biology research sonochemical, electrochemical methods and sol-gel process. to separate and purify cell populations, (ii) tissue repair; It is important for biomedical applications, to know the (iii) drug delivery, (iv) magnetic resonance imaging (MRI), synthesis process of the nanomaterial – which needs to be 7-9 (v) hyperthermia, (vi) magnetofection, among other . dispersed in water – and also, the study of biocompatibility In clinical applications, it is desirable MNP with sizes and toxicity that must possess adequate characteristics for between 10 and 200 nm, because MNP larger than 200 nm such applications. In the case of iron oxide MNP coated with can be filtered by the human spleen, and MNP smaller than biocompatible material determining the crystal phase, the 10 nm can be removed by renal clearance10. The usefulness average diameter and the magnetic property are important, *e-mail: [email protected] which can be measured using several techniques. 2014; 17(3) Synthesis and Characterization of Fe3O4 Nanoparticles with Perspectives in Biomedical Applications 543 This paper presents a synthesis route to prepar MNP grille containing parlodion and charcoal, and examined as well as the morphological, structural and magnetic using a LEO 906E equipment operating at 80 KV. characterization of the material synthesized to control quality The nanoparticles size poly-dispersity was analyzed of these MNP that are presented as promising particles in from the TEM micrographies using the image analysis biomedical applications. Morphological characterization program java ImageJ v 1.33u[17]. Mean diameters were was performed using the technique of transmission electron thus obtained by fitting the experimental data with a microscopy (TEM). The structural characterization was lognormal distribution function, as suggested by O’Grady 18 conducted using the technique of X-ray diffraction (XRD) and Bradbury . and Mössbauer spectroscopy. The magnetic characterization 2 lnDD− ln 0 was done using magnetometry (SQUID) and ferromagnetic 1 ( PP) fD()p =−exp (1) resonance (FMR). 2πw D 2w2 PP P 2. Experimental 0 2 With mean diameter <DP> = DP exp(wP/2) and wP as the standard deviation around ln D0 . The standard deviation of 2.1. Magnetic fluid preparation P the mean diameter sP is An alcoholic solution 200 ml of FeCl2 .6H O (Aldrich) 3 2 0 2 2 1/2 0.25M, in butanol, was prepared and heated under s=PPD [exp(2 w P ) − exp( w P )] (2) stirring to 90 °C. So, 8 mL of concentrated surfactant A commercial SQUID magnetometer was employed nonilpheniletoxilated (Renex 95®), another solution of to perform static and dynamic measurements as a function concentrated ammonia was prepared containing 4% (in field, temperature and driving frequency. Zero-field-cooled volume) of surfactant (Renex 95®). (ZFC) and field-cooled (FC) curves were taken in applied The ammonia solution was added drop by drop to magnetic fields up to 7 T, between 5K and 250 K to avoid the iron III solution to promote precipitation of iron oxi- melting of the solid matrix (solvent). hydroxide. The precipitate was centrifuged and washed with We used a ferromagnetic resonance (FMR) to verify butanol containing 4% (in volume) of surfactant at 90 °C the superparamagnetic behavior and to evaluate the in order to eliminate as possible the ammonium chloride. nanoparticles geometry. The derivative of the FMR After five washing cycles, we observed the peptization absorption spectrum was obtained using a Brucker X band of the precipitate and formation of 100 mL of true sol. homodyne spectrometer, model EMX-12 operating at Subsequently, 8 mL of surfactant (Renex 95®) and 10 mL frequency of 9.2GHz and modulated at 100 KHz with a TE102 of liquid paraffin (Nujol®) were added to the sol. dominant mode cavity. The measurements were carried out The sol was dried at 70 °C under stirring to aid butanol at room temperature. evaporation. After that, a viscous dark liquid was obtained. The viscous dark liquid was dried in a hermetically closed 3. Results and Discussion sintering chamber at 250 °C under N pressure (2 atm) for 2 Figure 1 shows the XRD profile of the redispersible half-hour. powder sample. We could observe a large low crystallinity After complete the procedure described above, we zone with 2θ = 30.19°. Typical diffuse profiles of iron obtained a black paste. This paste was dispersed in water oxide phases are added to the background and can be containing 4% of surfactant (Renex 95®) that formed a attributed to maghemite (γ-Fe O , ICSD Collection Code magnetic fluid. 2 3 79196), magnetite (Fe3O4, ICSD Collection Code 15840) 2.2. Characterization methods The crystalline phase of the redispersible black paste was determined by X-ray diffraction (XRD). The XRD data were collected between 10° < 2θ < 60° using the Cu- Kα radiation filtered by Ni in step scanning mode (0.05° for 10 s). Mössbauer spectroscopy (MS) measurements were performed at 78 K and 294 K using a constant-acceleration spectrometer in transmission geometry with a 57Co/Rh source. To calibrate isomer shifts and velocity scale, we used a foil of α-Fe at 294 K. For magnetic measurements, as-prepared samples were stored in closed containers before quenching the magnetite/carrier mixture below its freezing point (~268 K) at room temperature. Transmission electronic microscopy (TEM) was employed to check the size distribution of nanoparticles in Figure 1. Diffractogram of the synthesized sample, the inset shows the magnetic fluid. The magnetic fluid was dried at 70 °C by the possible existence of iron oxides magnetite (M), maghemite (m) water evaporation. Fine powders were aspersed on a cooper and / or hematite (H). 544 Mamani et al. Materials Research or hematite (α-Fe2O3, ICSD Collection Code 66756) corresponding