One-Step Ambient-Condition Synthesis of PEG- and PVA-Coated SPIONs: Morphological, Magnetic, and MRI Performance Assessment

Superparamagnetic iron oxide nanoparticles (SPIONs) are commonly produced through wet-chemical methods that require high temperature and pressure and involve multiple synthesis steps. Our research group has developed an innovative, sustainable, and patented one-step aqueous synthesis operating at ambient temperature and pressure, enabling the direct production of SPIONs in suspension. In this work, we investigated the extension of this method to obtain polymer-coated SPIONs for biomedical imaging applications. Two water-soluble and biocompatible polymers-poly(ethylene glycol) (PEG) and poly(vinyl alcohol) (PVA)-were selected and prepared into twelve samples varying in polymer concentration and iron precursor molarity. Each formulation was characterized and compared to bare SPIONs synthesized with the same approach using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), and alternating gradient magnetometry (AGM). The results confirm that the one-step method yields polymer-coated nanoparticles with a cubic spinel magnetite core. PEG produced spherical, monodisperse particles (10-30 nm) exhibiting superparamagnetic behavior but lower magnetization values (1-5 emu/g). In contrast, PVA-coated nanoparticles showed a morphology dependent on polymer concentration and reagent molarity, while maintaining an average size of ~10 nm and superparamagnetic behavior, with magnetization comparable to bare SPIONs (25-50 emu/g). A preliminary MRI evaluation of a selected PVA-coated sample revealed relaxivity values of r₁ = 0.12 mM^-1 s^-1 and r₂ = 6.44 mM^-1 s^-1, supporting the potential of this synthesis route for imaging-oriented nanomaterials.