One-pot ultrasound synthesis of water dispersible superparamagnetic iron oxide@alginate nanocomposite

Abstract

A new one-pot ultrasound methodology to prepare stable water-dispersible superparamagnetic Fe3O4@alginate nanocomposite was investigated. The radical hydroxyl (HO⋅) produced during ultrasound cavitation process was applied to oxidize ferrous (Fe2+) to ferric (Fe3+) cations in a 1.0 mol L−1 NaOH solution to obtain Fe3O4 nanoparticles. Structure, morphology, size, and magnetic property were characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Dynamic Light Scattering (DLS), Scanning Transmission Electron Microscopy (STEM) and magnetic measurements; interaction between iron oxide nanoparticles and coating alginate was characterized by Fourier Transform Infrared Spectroscopy (FTIR). Carboxylate symmetric and asymmetric bound absorption comparison (Δ ∼ 195 cm−1) suggests a bridging interaction from alginate to iron oxide. Calculations using Scherrer equation show that the particles have average crystallite size ranging from 6.5 ± 0.1 nm to 28.0 ± 0.1 nm obtained as a function of alginate concentration. The highest magnetization found was 57 emu.g−1 for the sample with 23.9% of alginate, and 72 emu.(g Fe3O4)−1 for the 36.7% of alginate. A stable, dispersible and superparamagnetic composite was obtained for 2.00 × 10−2 g mL−1 of alginate concentration in the NaOH solution, with hydrodynamic diameter of 92.36 ± 0.24 nm in water and the r1 and r2 relaxivity values measured as 4.39 and 63.3 s−1 mM−1, respectively, with r2/r1 = 14.4, using a constant field B = 0.47 T, suggesting a T2 weighted contrast agent (CAs) application. The hydrodynamic diameter measured in phosphate-buffered saline (PBS) (1x) and NaCl (0,9% w/w) were 116.94 ± 2.56 nm and 350.77 ± 21.74 nm, respectively. The particle size of the dispersible nanocomposite predicted by Langevin equation was 6.7 ± 0.6 nm. Those results suggest that we obtained a water dispersible Fe3O4@alginate nanocomposite prepared by ultrasound technique as a promising Magnetic Resonance Imaging (MRI)-contrast agent.