Investigation of Cubic and Spherical IONPs’ Rheological Characteristics and Aggregation Patterns from the Perspective of Magnetic Targeting

Abstract

Based on our prior research, we synthesized iron-oxide nanoparticles (IONPs) in two shapes (spherical and cubic) and sized them for the current inquiry. This research examined the magnetic, rheological, and sedimentation properties of the suspensions containing PEG-coated IONPs, considering that both produced particles are intended to be employed for magnetic targeting applications. The saturation magnetization of both IONPs was lower than the magnetite domain magnetization of 92 emu/g due to the surfactant and the dead surface magnetic layer. Under each investigated magnetic field (0, 34 and 183 mT), the shear viscosity behaviour of the MNP suspensions of both kinds was comparable. Shear thinning behaviour was seen for both particle suspensions in the low shear rate area (0.1 s−1 to 1 s−1). The rheological curves from this paper show that the suspensions present a higher viscosity at lower shear rates for spherical and cubic PEG-coated nanoparticles when a magnetic field is applied. The aggregation behaviour demonstrates that cubic-shaped IONPs are more stable throughout time, with hydrodynamic diameter measurements showing a relatively slow variation of the DLS size distribution from 250 nm to 210 nm in the first 600 s; contrarily, the hydrodynamic diameter of spherical IONPs fluctuated significantly, from 855 nm to 460 nm. Another key finding relates to the sedimentation profile, specifically that PEG-coated IONPs with spherical shapes have a stronger tendency to sediment than those with cubic forms, which are more stable.