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An exhaustive characterization of the physicochemical properties of gum arabic (GA)-coated Fe3O4 magnetic nanoparticles was conducted in this work. These nanoparticles were obtained via the in-situ coprecipitation method (a fast single-step method) in two GA:Fe ratios, 10:1 and 20:1, respectively. Several experimental techniques were applied in the characterization process, all of them described below. Using Transmission Electron Microcopy images, they were shown to have spherical-like morphology with 11 nm diameter. The Fourier Transform Infrared spectra confirmed the attachment of the GA on the surface of the magnetic nanoparticles (MNPs), providing good colloidal stability from pH 7 to 8. The thickness of the coatings (1.7 nm and 1.1 nm) was determined using thermogravimetric measurements. A high specific absorption rate and superparamagnetic properties were determined using alternant and static magnetic fields, respectively. The GA-coated MNPs were non-cytotoxic, according to tests on HT-29 human intestine cells. Additionally, HT-29 cells were exposed to magnetic fluid hyperthermia at 530 kHz, and the induction of cell death by the magnetic field, due to the heating of GA-coated MNP, was observed. [ABSTRACT FROM AUTHOR]

Highlights • Co–doped Fe 3 O 4 NPs presented an upconversion emission in the green and red region. • Fe 3 O 4 and co–doped Fe 3 O 4 NPs have magnetic response for an magnetic field. • Fe 3 O 4 and Yb3+ and Er3+co–doped Fe 3 O 4 NPs have superparamagnetic behavior. • Co–doped Fe 3 O 4 NPs can be used in imaging and hyperthermia therapy. Abstract The synthesis and characterization of ytterbium (Yb3+) and erbium (Er3+) co–doped Fe 3 O 4 nanoparticles (NPs) was reported for the first time in this work. A set of samples with fixed Er3+ (1 mol%) and different Yb3+concentrations (1, 10, 20 and 50 mol%) were prepared and systematically characterized to study their structural, magnetic, thermal and optical properties. The superparamagnetic behavior of Fe 3 O 4 and Yb3+ and Er3+co–doped Fe 3 O 4 NPs was verified by the hysteresis loop. The co–doped Fe 3 O 4 NPs also presented an upconversion emission in the green and red region. The Fe 3 O 4 and Fe 3 O 4 : Yb3+, Er3+ NPs showed hyperthermic behavior for an externally applied AC magnetic field, observing that the introduction of Yb3+ and Er3+ induced a temperature increase of 34.4% in optimal conditions with respect to the non–doped Fe 3 O 4 with a reduction in saturation magnetization of 7.8%. These observations suggest that Fe 3 O 4 : Yb3+, Er3+ NPs turns out to be an important candidate in biomedical applications for simultaneous optical imaging and hyperthermic therapy. [ABSTRACT FROM AUTHOR]