# Copper- and Iron-Based Nanoflowers in Cancer Theranostics
## 4 Synthesis Methods and Applications of Flower-like Copper- and Iron-Based Nanostructures  
### Iron-Based NFs  
Iron oxide NPs have been examined for their safety, biocompatibility, and significant clinical applications over the years. Various methods exist to activate their therapeutic properties, with superparamagnetic iron oxide nanoparticles (SPIONs) being particularly notable for their use as MRI contrast agents due to their non-toxic nature and the lack of residual magnetic force once the external field is removed. Transition metals or metal oxides are often selected for their high magnetic saturation to enhance therapeutic effectiveness. Magnetite (Fe\({}_{3}\)O\({}_{4}\)) and maghemite (\(\gamma\)-Fe\({}_{2}\)O\({}_{3}\)) nanoparticles have diverse biomedical applications, including drug delivery and cancer treatment. Their non-toxicity, biocompatibility, and relative ease of functionalization with various polymers or functional groups further enhance their utility [42]. Conventional Fe\({}_{3}\)O\({}_{4}\) nanoparticles are typically synthesized using a hydrothermal method without modifications, which frequently results in particle aggregation and precipitation. To address this issue, surface modifications and coatings are commonly employed to enhance the stability of Fe\({}_{3}\)O\({}_{4}\) nanoparticles. Mesoporous silica is often used as a material for surface passivation [108]. Iron NFs, along with other ferrous-based nanoparticles, are currently studied to be used in cancer theranostics, due to their excellent magnetic properties [76]. As an imaging modality, iron-based NFs have an auxiliary role as contrasting agents in MRI scans both in vitro and in vivo experiments. Concerning cancer therapy, NFs find use in PTT. Usually,  
Figure 11: FE-SEM images of enzyme-functionalized Cu(II) HNFs. Effect of (**a**) pH, (**b**) temperature, and (**c**) incubation time on their morphologies. Modified and reproduced with permission from Ref. [104]. PTT is based on photothermalria: the optical excitation of plasmonic nanoparticles by an infrared laser causing localized heating that can destroy nearby cancer cells. Likewise, when using magnetic nanoparticles, a high-frequency magnetic field is applied, exciting the fluctuations of the magnetic moment and resulting in magnetic energy release in the form of heat. In other words, it is the use of the photoirradiation of photothermal agents (in this case, NFs) in order to generate heat for the localized thermal damage of solid cancerous tumors [109]. Table 3 presents iron-based nanoflowers synthesized by different processes, and Table 4 shows the synthesized iron nanoflowers under diverse reaction conditions and their main findings. \begin{table}
\begin{tabular}{c c c c} \hline
**Nanflower** & **Synthesis Parameters** & **Main Findings** & **Ref.** \\
**Type** & & & In imaging: \\  & Temperature: 365 \({}^{\circ}\)C; & Contrast enhancement in MRI, easier tumor & \\  & Reaction time: 1 h; & identification. & \\  & Precursors: Mn(acac)\({}_{2}\) & In vitro: & \\ Fe\({}_{0.6}\)Mn\({}_{0.4}\)O & Fe(acac)\({}_{3}\) (0.65:1 mol/mol); & Hyperhemia at low dosage against MCF-7 & [110] \\  & Reducing agent/solvent: trioctylamine; & cancer cells. & \\  & Surfactants: oleic acid, oleylamine; & In vivo: & \\  & Washing solvents: hexane, EtOH. & Complete tumor inhibition without & \\  & Temperature: 200 \({}^{\circ}\)C; & appreciable side effects on the treated mice. & In imaging: \\  & Reaction time: 16 h; & Magnetic properties for MRI monitoring of & \\  & Precursor: FeCl\({}_{3}\) GHz\({}_{2}\)O; & the therapeutic process. & \\ Fe\({}_{3}\)O\({}_{4}\)@PEG & Reducing agent: NaAc 3H\({}_{2}\)O; & As a PTT agent: & \\  & Stabilizer: PEG; & Under 808 nm laser, Fe\({}_{3}\)O\({}_{4}\) NFs are more & \\  & Solvent: ethylene glycol; & efficient than the reported Fe\({}_{3}\)O\({}_{4}\) NPs. & In vitro and in vivo results show that they & \\  & Washing solvents: EtOH, DI H\({}_{2}\)O. & In vitro and in vivo results show that they & \\ \hline \end{tabular}
\end{table}