## 4 Conclusions  
The study analyzed the cytotoxic effects of Fe\({}_{3}\)O\({}_{4}\) and Fe\({}_{3}\)O\({}_{4}\)-Ag decorated nanoparticles on human fibroblasts (HFF-1) and breast cancer cells (MCF-7) to evaluate their biocompatibility and potential therapeutic efficacy. The results showed that neither type of nanoparticle significantly reduced cell viability in HFF-1 fibroblasts, indicating that they are non-cytotoxic at the tested concentrations on a non-cancerous cell line. Similarly, MCF-7 breast cancer cells did not exhibit a significant change in viability when exposed to different nanoparticle concentrations, suggesting that these nanoparticles are biocompatible and allow normal cell growth. While evaluating the cytotoxic effects of these nanosystems in  
Figure 9: Zeta potential graph of Fe\({}_{3}\)O\({}_{4}\) nanoparticles as a function of pH.  
combination with other antineoplastic drugs across various cell lines from healthy tissues and neoplasms is crucial, this study primarily focuses on elucidating the biocompatibility of magnetite nanoparticles. This highlights the potential of Fe\({}_{3}\)O\({}_{4}\) and Fe\({}_{3}\)O\({}_{4}\)-Ag nanoparticles for biomedical applications, given their compatibility with both normal and cancerous cells.  
Reactive oxygen species (ROS) production by Fe\({}_{3}\)O\({}_{4}\) and Fe\({}_{3}\)O\({}_{4}\)-Ag nanoparticles was also examined to assess their biocompatibility in aims of their future therapeutic potential. The study found that higher concentrations 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 at these concentrations. However, excessive ROS production can harm normal cells, underscoring the need to evaluate nanoparticle concentrations to balance therapeutic efficacy and safety carefully. These findings contribute to understanding nanoparticle interactions with cellular oxidative mechanisms, which are crucial for developing safe and effective nanoparticle-based therapies. Altogether, the results herein indicated that it is possible to use Fe\({}_{3}\)O\({}_{4}\)-Ag nanoparticles as future drug delivery agents and enhance the synergy of their physicochemical properties with the antiproliferative mechanisms of the anticancer agents, also seeking the repositioning of front-line drugs for the treatment of public health diseases.  
Not applicable.  
The raw data supporting the conclusions of this article will be made available by the authors on request.  
[PERSON] wishes to express profound gratitude for the invaluable support provided by the National Council for Humanities, Science, and Technology (CONAHCYT, Mexico), in collaboration with the Center of Applied Physics and Advanced Technology (CFATA-UNAM), through the \"Investigadoras e Investigadores por Mexico-CONAHCYT\" program. Additionally, heartfelt thanks are extended to the \"Instituto de Ciencias Biomedicas de la UACJ\" for their unwavering support during the sabbatical period. The authors would like to express their acknowledgment of [PERSON] (INB-UNAM), for her technical assistance. Additionally, the authors appreciate the support from the Microscopy Laboratory at the National Laboratory for Materials Characterization (LanCam), through the academic technician [PERSON].  
The authors declare no conflicts of interest.