## 4 Discussion  
Water-soluble, biocompatible patchy Fe\({}_{3}\)O\({}_{4}\)-Au nanoparticles (Fe\({}_{3}\)O\({}_{4}\)@Au pNPs) were prepared through a facile one-pot synthesis procedure followed by functionalization with Imidazolium-PA forming a positively charged, self-assembled monolayer on the surface [31]. The one-pot synthesis route started with a redox reaction in acidic solution and was followed by co-precipitation under alkaline conditions. The initial redox reaction between Au\({}^{3+}\) and Fe\({}^{2+}\) cations did not only produce elemental Au\({}^{0}\) and thereupon, Au nuclei but also Fe\({}^{3+}\) cations which fed the subsequent alkaline co-precipitation process. In the supersaturated acidic reaction solution, AuNCs were formed. The subsequent alkaline co-precipitation provided the formation of Fe\({}_{3}\)O\({}_{4}\) NPs in the presence of AuNC which epitaxially grew on the surface of the Fe\({}_{3}\)O\({}_{4}\) NPs, probably under prosecution of the redox reaction. The morphology, composition and surface chemistry, crystallographic, magnetic and optical \begin{table}
\begin{tabular}{c c c c} \hline
**DMF** & **MCF-7** & **A549** & **MCF-10A** \\ \hline Fe\({}_{3}\)O\({}_{4}\)-NP & 0.616 & 0.642 & 0.731 \\ AuNC & 0.611 & 0.607 & 0.344 \\ Au-Fe\({}_{3}\)O\({}_{4}\)-NP & 0.447 & 0.422 & 0.804 \\ \hline \end{tabular}
\end{table} 
Table 1: DMF values obtained from the radiation dose survival curves of MCF-7, A549 and MCF-10A cells depicted in Figure 10.  
Figure 11: (**a**) Reaction scheme of the Fe\({}^{2+}\)/Fe\({}^{3+}\)-catalyzed Fenton reaction and Haber-Weiss cycle; radiation dose survival curves of MCF-7 cells (**b**), A549 cell (**c**) and MCF-10A cells (**d**) in medium (green) and incubated with Fe\({}_{3}\)O\({}_{4}\)@Au pNPs (blue), Fe\({}_{3}\)O\({}_{4}\) NPs (black) and AuNC (red). properties of the Fe\({}_{3}\)O\({}_{4}\)@Au pNPs were characterized using HRTEM, EDX, and FTIR transmission spectroscopy, XRD, SQUID, and UV-Vis absorption spectroscopy, respectively. As is evident from the XRD data, HRTEM and EDX analysis, the 12.5 nm-sized Fe\({}_{3}\)O\({}_{4}\)@Au pNPs consist of a spherical monocrystalline Fe\({}_{3}\)O\({}_{4}\) core that is partially coated with crystalline AuNCs and Au nanopatches (Figure 3). Consistently, the Fe\({}_{3}\)O\({}_{4}\)@Au pNPs were found to exhibit superparamagnetism, with a Ms value of 43.6 emu/g, which is smaller than that of nearly equally sized Fe\({}_{3}\)O\({}_{4}\) NPs [30]. This difference is thought to arise from the interface communication between the Au nanopatches and the Fe\({}_{3}\)O\({}_{4}\) core, which partially degrades the magnetization. This is corroborated by the quenching of the surface plasmon resonance band in the UV-Vis absorption spectrum (Figure 5), as indicating interfacial electron transfer from the Au\({}^{0}\) to Fe\({}^{3+}\) cations. As is obvious from the TEM image (Figure 7) displaying agglomerates in endosomes, internalization by MCF-7 cells followed the endocytic pathway. The impact of the different kinds of nanoparticles on the viability of the cancerous MCF-7 and A549 cells and healthy epithelial MCF-10A cells was evaluated by performing the neutral red assay (Figure 8). Imidazolium-PA-stabilized Fe\({}_{3}\)O\({}_{4}\)@Au pNPs at a concentration of 10 \(\upmu\)g/mL degraded the viability of MCF-7 and MCF-10A cells by 20%, whereas the A549 cells were hardly damaged. Intracellular AuNC were observed to decrease the viability of MCF-7, A549 and MCF-10A cells to values between 87% and 90%. In contrast, the biocompatibility of the Imidazolium-PA-stabilized Fe\({}_{3}\)O\({}_{4}\) NPs is remarkably high, exhibiting cell viability values of around 95% for all kinds of cells under study. This is due to the shielding effect of Imidazolium-PA, which is self-assembled in a monolayer on the Fe\({}_{3}\)O\({}_{4}\) NP surface, obviously preventing the formation of HO\({}^{\bullet}\) at the Fe\({}^{2+}\) cation-containing surface.