###### Abstract  
This study investigates the cytotoxicity profile of superparamagnetic Fe\({}_{3}\)O\({}_{4}\)-Ag decorated nanoparticles against human fibroblasts (HFF-1) and breast cancer cells (MCF-7). The nanoparticles underwent comprehensive characterization employing scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis, X-ray photoelectron spectroscopy (XPS), and magnetic assays including hysteresis curves and zero-field-cooled (ZFC) plots. The nanoparticles exhibited superparamagnetic behavior as evidenced by magnetic studies. Cytotoxicity assays demonstrated that both HFF-1 and MCF-7 cells maintained nearly 100% viability upon nanoparticle exposure, underscoring the outstanding biocompatibility of Fe\({}_{3}\)O\({}_{4}\)/Ag decorated nanoparticles and suggesting their potential utility in biomedical applications such as drug delivery and magnetic targeting. Furthermore, the study analyzed the cytotoxic effects of Fe\({}_{3}\)O\({}_{4}\) and Fe\({}_{3}\)O\({}_{4}\)-Ag decorated nanoparticles to evaluate their biocompatibility for further therapeutic efficacy. Results showed that neither type of nanoparticle significantly reduced cell viability in HFF-1 fibroblasts, indicating non-cytotoxicity at the tested concentrations. Similarly, MCF-7 breast cancer cells did not exhibit a significant change in viability when exposed to different nanoparticle concentrations, highlighting the compatibility of these nanoparticles with both healthy and cancerous cells. Additionally, the production of reactive oxygen species (ROS) by cells exposed to the nanoparticles was examined to guarantee their biosafety for further therapeutic potential. Higher concentrations (50-100 ug/mL) of Fe\({}_{3}\)O\({}_{4}\)-Ag nanoparticles decreased ROS production in both HFF-1 and MCF-7 cells, while Fe\({}_{3}\)O\({}_{4}\) nanoparticles were more effective in generating ROS. This differential response suggests that Fe\({}_{3}\)O\({}_{4}\)-Ag nanoparticles might modulate oxidative stress more effectively, thus beneficial for future anticancer strategies due to cancer cells' susceptibility to ROS-induced damage. These findings contribute to understanding nanoparticle interactions with cellular oxidative mechanisms, which are crucial for developing safe and effective nanoparticle-based therapies. This investigation advances our understanding of nanostructured materials in biological settings and highlights their promising prospects in biomedicine. superparamagnetic nanoparticles; cytotoxicity; biocompatibility; biomedical applications 1  
A.J.R.-B. therapeutic interventions [1; 2; 3]. Among the diverse nanomaterials available, superparamagnetic iron oxide nanoparticles (SPIONs) have garnered significant attention due to their exceptional physicochemical properties, including their high surface area, biocompatibility, and magnetic responsiveness [4]. These unique characteristics have led to the exploration of iron oxide nanoparticles, particularly Fe\({}_{3}\)O\({}_{4}\), in various biomedical applications, such as magnetic resonance imaging (MRI), hyperthermia-based cancer treatment, and drug delivery [5; 6]. The synthesis and functionalization of Fe\({}_{3}\)O\({}_{4}\) nanoparticles have been extensively investigated, with researchers exploring different strategies to enhance their stability, biocompatibility, and targeting capabilities [7; 8]. One approach that has shown promise is the decoration of Fe\({}_{3}\)O\({}_{4}\) nanoparticles with silver (Ag) to create Fe\({}_{3}\)O\({}_{4}\)-Ag structures [9]. The addition of silver can potentially improve the antibacterial properties and electrical conductivity of the nanoparticles, making them attractive for a wide range of biomedical applications [10; 11]. Another application of the Fe\({}_{3}\)O\({}_{4}\)-Ag nanoparticles is in the field of cancer therapy [12; 13]. The enhanced magnetic and plasmonic properties of the decorated nanoparticles can be leveraged for targeted drug delivery, photothermal therapy, and magnetic hyperthermia.