# Copper- and Iron-Based Nanoflowers in Cancer Theranostics
## 2 Synthesis Methods for Copper- and Iron-Based Nanoflowers
### Co-Precipitation Method  
Co-precipitation is the very frequently utilized in biomedical applications due to its ability to produce relatively less harmful and easily prepared particles [62]. Additionally, this approach offers safety and cost efficiency and operates at a lower temperature levels as opposed to alternative techniques [42].  
The overall reaction of ferric and ferrous ions can be expressed as  
\[\mathrm{Fe}^{2+}+2\mathrm{Fe}^{3+}+8\mathrm{OH}^{-}\rightarrow\mathrm{Fe}_{ 3}\mathrm{O}_{4}+4\mathrm{H}_{2}\mathrm{O}.\]  
If the reaction conditions are carefully controlled, it may oxidize to Fe(OH)\({}_{3}\), significantly impacting the properties of the NPs. This reaction can be represented as follows:  
\[4\mathrm{Fe}_{3}\mathrm{O}_{4}+\mathrm{O}_{2}+18\mathrm{H}_{2}\mathrm{O} \rightarrow 12\mathrm{Fe(OH)}_{3}.\]  
Other reaction parameters, including the rate at which the solution is added and the stirring speed, also influence the quality of the result. It is essential to regulate the pH of the reaction mixture throughout both the synthesis and purification stages. Additionally, due to their high surface-to-volume ratio, nanoparticles have the tendency to aggregate in solution to minimize their surface energy. As a result, alternative approaches have been established to achieve better outcomes and more uniform dimensions [42].  
[PERSON] et al., synthesized hydrophilic, surface-functionalized superparamagnetic iron oxide nanoparticles (SPIOs) for liver cancer treatment through magnetic fluid hyperthermia (MFH)-based thermotherapy. In calorimetric fluid hyperthermia  
Figure 2: Commonly chemical employed techniques for synthesizing inorganic nanoflowers.  
(C-MFH) studies, aqueous ferrofluid (AFF) based on SPIOs coated with 34 DABA demonstrated a faster thermal response to an applied alternating magnetic field (AMF). Furthermore, the 34 DABA-coated SPIO-based AFF exhibited superior heating efficiency, with specific absorption rate (SAR) and intrinsic loss power (ILP) values of 432.1 W gFe\({}^{-1}\) and 5.2 nHm\({}^{2}\) kg\({}^{-1}\), respectively, at 0.5 mg mL\({}^{-1}\). The high heating efficiency of 34 DABA-coated SPIOs is attributed to an enhanced \(\pi\)-\(\pi\) conjugation within the coating molecules and improved anisotropy from an SPIO cluster or chain formation in ferrofluid suspensions. These nanoparticles also exhibit excellent cytocompatibility over 24 and 48 h incubation periods and achieve a superior cancer cell killing efficiency of 61-88% against HepG2 liver cells through magnetic fluid hyperthermia (MFH), outperforming AMF- or water-bath-based thermotherapy alone [63].  
Figure 3 shows the coating molecules and the chemical synthesis process for these surface-functionalized SPIOs [63].  
The produced SPIOs successfully entered the HepG2 liver cancer cells, as confirmed by Prussian blue staining. These SPIOs could be valuable in cancer thermotherapy [63].  
[PERSON] et al., synthesized copper-molybdate (CuMoO\({}_{4}\)) nanoflowers by employing the co-precipitation method. In their experiment, an aqueous solution of Copper Salicylidene (Cu(Sal)\({}_{2}\)) in the presence of different surfactants was used as a precursor, while an aqueous solution of (NH\({}_{4}\))\({}_{6}\)Mo\({}_{7}\)O\({}_{24}\) 4H\({}_{2}\)O was used as a precipitating agent. To investigate the effect of surfactants on the morphology and size of the product, SEM images were obtained for the prepared samples using polyvinylpyrrolidone (PVP), polyethylene glycol 600 (PEG), sodium dodecyl sulfate (SDS), and cetyltrimethylammonium bromide (CTAB) as surfactants. In a typical procedure, the two solutions were mixed and heated together. After that, the product was further processed by filtration, cleaning and drying [64].