Cancer is one of the most common diseases nowadays and derives from the uncontrollable growth of a single cell. Magnetic nanoparticles (NpMag) offer various possibilities for use in the biomedical area, including drug delivery mediated by magnetic fields. In the current study, we evaluated the in vitro effects of iron-oxide magnetic nanoparticles conjugated with the antitumor drug doxorubicin (Dox) on human breast cancer cells. Our results revealed that magnetic nanoparticles with Dox (NpMag+Dox) induce cellular redox imbalance in MCF-7 cells. We also demonstrate that iron-oxide nanoparticles functionalized with Dox induce oxidative stress evidenced by DNA damage, lipid peroxidation, cell membrane disruption, and loss of mitochondria potential. As a result, NpMag+Dox drives MCF-7 cells to stop the cell cycle and decrease cell migration. The association of NpMg+Dox induced a better delivery of Dox to MCF cells, mainly in the presence of a magnetic field, increasing the death of MCF cells which might reduce the toxicity for healthy cells providing a better efficacy for the treatment. Thus, iron-oxide nanoparticles and doxorubicin conjugated may be candidate for anticancer therapy.

The incidence of female breast cancer has increased; it is the most commonly diagnosed cancer, at 11.7% of the total, and has the fourth highest cancer-related mortality. Magnetic nanoparticles have been used as carriers to improve selectivity and to decrease the side effects on healthy tissues in cancer treatment. Iron oxide (mainly magnetite, Fe${}_3$O${}_4$), which presents a low toxicity profile and superparamagnetic behavior, has attractive characteristics for this type of application in biological systems. In this article, synthesis and characterization of magnetite (NP-Fe${}_3$O${}_4$) and silica-coated magnetite (NP-Fe${}_3$O${}_4$/SiO${}_2$) nanoparticles, as well as their biocompatibility via cellular toxicity tests in terms of cell viability, are carefully investigated. MCF-7 cells, which are commonly applied as a model in cancer research, are used in order to define prognosis and treatment specifics at a molecular level. In addition, HaCaT cells (immortalized human keratinocytes) are tested, as they are normal, healthy cells that have been used extensively to study biocompatibility. The results provide insight into the applicability of these magnetic nanoparticles as a drug carrier system. The cytotoxicity of nanoparticles in breast adenocarcinoma (MCF-7) and HaCat cells was evaluated, and both nanoparticles, NP-Fe${}_3$O${}_4$/SiO${}_2$ and NP-Fe${}_3$O${}_4$, show high cell viability (non-cytotoxicity). After loading the anti-tumor drug doxorubicin (Dox) on NP-Fe${}_3$O${}_4$/Dox and NP-Fe${}_3$O${}_4$/SiO${}_2$/Dox, the cytotoxicity against MCF-7 cells increases in a dose-dependent and time-dependent manner at concentrations of 5 and 10 $\mathsf{\mu }$g/mL. HaCat cells also show a decrease in cell viability; however, cytotoxicity was less than that found in the cancer cell line. This study shows the biocompatibility of NP-Fe${}_3$O${}_4$/SiO${}_2$ and NP-Fe${}_3$O${}_4$, highlighting the importance of silica coating on magnetic nanoparticles and reinforcing the possibility of their use as a drug carrier system against breast adenocarcinoma cells (MCF-7).