# Recent Progress and Challenges Regarding Magnetic-Based Nanoparticles for Targeted Drug Delivery
## 3.3. **Magnetite-Based Nanomaterials for Specific Cancer Treatment**
### Breast Cancer Treatment
The diatom-based biohybrid microrobot demonstrated high DOX-loading capacity and pH sensitivity. Notably, the possibility of magnetic control of the nanocar was deeply investigated. The microrobots can be controlled individually and as dimers, trimers, or multimers. However, high drug delivery efficiency is possible only by using swarms of microrobots. Low concentration of the biohybrid microrobots resulted in independent movements due to long distances between magnetic species. On the other hand, higher concentrations initiated the interaction, followed by the swarming behavior and, consequently, larger-dose drug delivery. Lately, several original papers have emerged featuring other drugs loaded into magnetite-based nanocarriers for the potential treatment of breast cancer. Platinum-based drugs (e.g., cis-platin, cis-[Pt(NH\({}_{3}\))\({}_{2}\)Cl\({}_{2}\)]) are responsible for the direct damaging of DNA and are used for the treatment of various cancers. Carboplatin functions as an alkylating agent that produces platinum complexes. The complexes are linked to the DNA, resulting in double-strand breaks. Magnetic-chitosan (CS-Fe\({}_{3}\)O\({}_{4}\)) and magnetite-chitosan-graphene oxide (CS-Fe\({}_{3}\)O\({}_{4}\)-GO) nanocomposites were used for loading and targeted delivery of carboplatin to breast cancer cell lines [59]. The entrapment of the drug in magnetite-based systems reduced the systemic toxicity of carboplatin and enhanced its activity against MCF-7 cell lines. However, the release rates in the physiological and acidic medium were only slightly different. On the other hand, platinum could also be applied as a nanoenzyme with catalytic activity responsible for directly combating cancer cells and subsequently improving drug permeability. Therefore, the Fe\({}_{3}\)O\({}_{4}\) nanospheres loaded with platinum and 5-fluorouracil coated with polyethylene glycol (Fe\({}_{3}\)O\({}_{4}\)/Pt-5-FU@PEG) were investigated as platforms for the treatment of solid breast cancer [60]. The nanocarriers showed pH-sensitive drug release under acidic conditions. Pt demonstrated peroxidase and catalase mimic activity, increasing levels of reactive oxygen species and O\({}_{2}\). Cytotoxic studies proved reduced proliferation of 4T1 cancer cells, while in vivo studies showed tumor size reduction and overcoming its hypoxia. Platinum was also introduced into core-shell nanospheres composed of an Fe\({}_{3}\)O\({}_{4}\)-Pt@metal-organic framework (MOF) for eprintbicin delivery [61]. The nanocarriers was synthesized by hydrothermal and layer-by-layer methods. MOF coating should increase porosity, colloidal stability, bioavailability, catalytic activity and facilitate drug release in an acidic environment. The nanoplatform exhibited pH-sensitive drug release in a tumor microenvironment. EPI-loaded nanospheres effectively inhibited triple-negative 4T1 cancer cell proliferation due to improved penetration compared to pristine EPI. However, the in vitro results were not confirmed by in vivo studies. MOF was also successfully adapted to prepare the targeted delivery system of antibiotic ciprofloxacin (CPX) [62]. MOFs produced from transition metal ions are biocompatible, chemically stable, capable of modification, and have high drug loading efficiency. In turn, a particular group of MOFs, Material Institute Lavoisiers (MILs), are a network of trivalent ions and carboxylic acid-derived linkers. Therefore, MIL-100(Fe) with high surface area and stability was applied for drug encapsulation. MIL-100(Fe) was prepared in the presence of magnetite-silica NPs. The nanomaterial demonstrated the biocompatibility, while the CPX-loaded nanocarriers showed significant toxicity against cancer cells. Among the systems designed for delivering alternative drugs, it is noteworthy to mention the system incorporating an aptamer (Apt) conjugated to paclitaxel (Fe\({}_{3}\)O\({}_{4}\)@PTX-Apt) [63]. The aptamer is a peptide or oligonucleotide molecule acting as a chemical antibody.