## 1 Introduction
These magnetite nanomaterials are used as absorbents, and also as photocatalysts to degrade various agents, including organic pollutants, antibiotics, and pesticides [27; 28; 29; 30; 31]. To avoid agglomeration and improve the stabilization of magnetite nanoparticles in the target tissue, they are generally covered with a coating shell [4; 32]. Another great applicability of magnetic iron oxide nanoparticles is in superparamagnetic iron oxide nanoparticles (SPIONs), which have attracted attention due to their properties for loading biological active agents with multiple purposes in biological applications. For this reason, it has been shown that superparamagnetic iron oxide nanoparticles (SPIONs) coated with silica presented potential in biomedical applications such as imaging, contrast agents, and drug targeted therapy [33]. [PERSON] et al. [34] demonstrated a facile, low-cost synthesis for the fabrication of a different type of magnetite such as monodisperse superparamagnetic single-crystal magnetite nanoparticles with a mesoporous structure (MSSMN) through a very simple solvothermal method with promising applications in drug delivery. In the context of surface functionalization, surface characteristics are aspects that should be considered when applying nanoparticles in biomedical applications. The size of nanoparticles and the surface ratio of atoms in a nanoparticle are critical issues when it comes to magnetization. Thus, the nanoparticles and their oxides have a ferromagnetic effect. For a better understanding of the characteristics of ferromagnetism, it has been brought to our attention that non-magnetic nanoparticles such as cerium oxide and aluminium oxide present magnetic hysteresis at room temperature, and materials such as niobium nitride have ferromagnetic properties. Since nanoparticles are small, the higher the ferromagnetic function is [15]. The sum of magnetization of a nanoparticle consists of two effects: one that occurs on the surface and the second inside the particle core. According to this research, the existence of superficial defects has promoted a magnetic disturbance that continues within the closest layer. The most prominent characteristic of magnetic nanoparticles to be understood is the superficial effect and anisotropy; therefore, their understanding is primordial in the development of magnetic nanoparticles with applications in biomedicine, such as MRI and magnetic hyperthermia [15; 35]. Through the surface functionalization of magnetite nanoparticles, researchers achieve unique and significant improvements in their properties, especially stability [36; 37]. The silica coating can be one of the best options for surface functionalization because of its greater stability against degradation compared to most organic shells. The test results suggested that functionalized silica exhibited improved properties compared to before functionalization. The immobilization of biological agents such as enzymes and drugs onto the porous structure of silica was conducted in developing better stability of the nanostructure [38]. Silica has groups of silanol on the surface and their presence improves the capacity for functionalization, biocompatibility, and hydrophilic-hydrophobic ratio, making them excellent materials for different biomedical [39; 40; 41] and environmental applications [42]. [PERSON] et al. [43] used the Stober method to coat silica on magnetite nanoparticles during trials, and [PERSON] et al. [44] used the sol-gel method to coat silica on maghemite nanosphere. The literature provides many studies involving micro-emulsion and reverses micro-emulsion that describe the coating methods for iron oxide with silica. These synthesis methods offer significant advantages in obtaining preferential nanoparticles and have significant implications for biomedical applications. The major challenge for researchers was to integrate the structure of cubic magnetic nanoparticles into the structure of magnetite and functionalize it with silica for developing a rising material for biomedical applications.