Abstract The surface of Fe3O4 nanoparticles is very reactive and can oxidize to γ-Fe2O3 (maghemite) and α-Fe2O3 (hematite) structures. Based on this, the oxidation process of Fe3O4 nanoparticles must be prevented, and one of the strategies is surface functionalization with organic or inorganic molecules. Thus, this study analyzed the thermal behavior of Fe3O4 and Fe3O4-EDTA nanoparticles using X-ray diffraction (XRD), simultaneous thermogravimetry-differential thermal analysis (TG-DTA), differential scanning calorimetry (DSC). Results showed that γ- Fe2O3 was obtained as an intermediate in Fe3O4 and Fe3O4-EDTA decomposition, as confirmed by TG-DTA and DSC curves. Moreover, Fe3O4-EDTA exhibited a temperature peak (Tp = 573.5°C) of phase transformation (γ-Fe2O3 → α-Fe2O3) higher than that of Fe3O4 (Tp = 533.0°C), confirming that EDTA molecules stabilized the nanoparticles efficiently. The kinetic behavior of samples changed, and the activation energy for functionalized samples decreased.

The controlled release of Salicylic Acid (SA) influences the concentration and collateral effects of the drug. This release refers to the matrix in which the SA is incorporated. Among the matrices, Fe3O4 nanoparticles (NPs) stand out, for transporting drugs to specific sites. The functionalization of Fe3O4 by bovine serum albumin (BSA) can improve colloidal and chemical stability, in addition to increasing interactions with drugs. Thus, understanding the release kinetics of the AS incorporated in Fe3O4-BSA is essential to improve the controlled release. The study aimed the synthesis, characterization and release of the SA into the Fe3O4-BSA NPs. The results showed the functionalization of the Fe3O4-BSA NPs was effective and the average size was below 30 nm. The NPs showed colloidal stability above the pH of 7.5 which can be used as a drug carrier in blood plasma. Drug encapsulation into the NPs system was efficient (~91%) with about 30% of drug loading capability. The kinetic results showed the SA release mechanism was controlled by diffusion. The conclusion is that the incorporation of SA in Fe3O4-BSA NPs led to a release of SA in the first six hours, reaching equilibrium at 0.265 mg mL-1; and 1.83 mg.