In recent decades, magnetite nanoparticles received greater attention in nanobiotechnology due to wide applications. This study presents the influence of the oxidative stress caused by magnetite nanoparticles coated with aspartic acid (A-MNP) of 9.17 nm mean diameter size, on maize (Zea mays) seedlings, in terms of growth, enzymatic activity and chlorophyll content as evaluated in exposed plant tissues. Diluted suspensions of colloidal magnetite nanoparticles stabilized in water were added to the culture medium of maize seeds, such as to equate nanoparticle concentrations varying from 0.55 mg/L to 11 mg/L. The obtained results showed that the growth of maize was stimulated by increasing the level of A-MNPs. Plant samples treated with different concentrations of A-MNP proved increased activities of catalase and peroxidase, and chlorophyll content, as well. The exposure of plants to magnetite nanoparticles may induce oxidative stress, which activates the plant defense/antioxidant mechanisms.

Aspartic acid stabilized iron oxide nanoparticles (A-IONPs) with globular shape and narrow size distribution were prepared by the co-precipitation method in aqueous medium. A quantum-mechanical approach to aspartic acid optimized structure displayed negative charged sites, relatively high dipole moment, and hydrophilicity, which recommended it for interaction with iron cations and surrounding water electrical dipoles. A-IONPs were characterized by TEM, XRD, ATR-FTIR, EDS, DSC, TG, DLS, NTA, and VSM techniques. Theoretical study carried out by applying Hartree-Fock and density functional algorithms suggested that some aspartic acid properties related to the interaction can develop with nanoparticles and water molecules. The results of experimental investigation showed that the mean value of particle physical diameters was 9.17 ± 2.2 nm according to TEM image analysis, the crystallite size was about 8.9 nm according to XRD data, while the magnetic diameter was about 8.8 nm, as was determined from VSM data interpretation with Langevin’s theory. The A-IONP suspension was characterized by zeta-potential of about −11.7 mV, while the NTA investigation revealed a hydrodynamic diameter of 153.9 nm. These results recommend the A-IONP suspension for biomedical applications.

Hyaluronic acid (HA) has attracted much attention in tumor-targeted drug delivery due to its ability to specifically bind to the CD44 cellular receptor, which is widely expressed on cancer cells. We present HA-capped magnetic nanoparticles (HA-MNPs) obtained via the co-precipitation method, followed by the electrostatic adsorption of HA onto the nanoparticles’ surfaces. A theoretical study carried out with the PM3 method evidenced a dipole moment of 3.34 D and negatively charged atom groups able to participate in interactions with nanoparticle surface cations and surrounding water molecules. The ATR-FTIR spectrum evidenced the hyaluronic acid binding to the surface of the ferrophase, ensuring colloidal stability in the water dispersion. To verify the success of the synthesis and stabilization, HA-MNPs were also characterized using other investigation techniques: TEM, EDS, XRD, DSC, TG, NTA, and VSM. The results showed that the HA-MNPs had a mean physical size of 9.05 nm (TEM investigation), a crystallite dimension of about 8.35 nm (XRD investigation), and a magnetic core diameter of about 8.31 nm (VSM investigation). The HA-MNPs exhibited superparamagnetic behavior, with the magnetization curve showing saturation at a high magnetic field and a very small coercive field, corresponding to the net dominance of single-domain magnetic nanoparticles that were not aggregated with reversible magnetizability. These features satisfy the requirement for magnetic nanoparticles with a small size and good dispersibility for long-term stability. We performed some preliminary tests regarding the nanotoxicity in the environment, and some chromosomal aberrations were found to be induced in corn root meristems, especially in the anaphase and metaphase of mitotic cells. Due to their properties, HA-MNPs also seem to be suitable for use in the biomedical field.