# Copper- and Iron-Based Nanoflowers in Cancer Theranostics
## 1 Introduction
Their structure enhances surface reactions, offering benefits such as strong adsorption capacity, great catalytic ability, and efficient drug loading potential [29]. NFs can be produced from a range of organic and inorganic materials, including polymers, metals, metal oxides, and carbon. Additionally, hybrid nanoflowers (HNFs) made from DNA, proteins, enzymes, and polymers are also a significant area of interest [30]. In 2012, [PERSON] and his team created an organic-inorganic hybrid--by adding Cu(II) sulfate to phosphate-buffered saline containing a protein, expanding the focus beyond metal NFs [31]. This discovery paved the way for new nanohybrids, expanding the scope of nanofiber research. These NFs possess a distinctive geometry, with petal- or branch-like structures radiating from a central core, resembling natural flowers [32]. The unique design of NFs is achieved through controlled synthesis involving seed-mediated growth, optimized reactions, and selected precursor materials [33]. Their layered structure enhances adsorption capacity, electrocatalytic activity, loading capacity, and stability [34]. Hybrid nanoflowers composed of metal ions and polymers exhibit unique characteristics. Recently, multiple reviews have explored the synthesis of nanoflowers. [PERSON] and his team offered an in-depth analysis of hybrid nanoflowers, covering their design, synthesis methods, mechanisms, and properties. They also emphasized advanced biomedical applications such as biosensing, biocatalysis, and cancer treatment [35]. In 2022, [PERSON] and team reviewed inorganic nanoflowers, emphasizing their applications in various treatments, including cancer therapy. Two years later, the same group released another review that categorized inorganic nanoflowers into categories according to their attributes. They discussed preparation methods, morphology, size control, mechanisms, and possible uses to advance future research and promote synergistic implementations across various fields [36]. [PERSON] and his team investigated the synthetic methods, properties, and biomedical applications of various nanostructures, including nanoflowers and other nanostructures. Their work provides insights into their use as advanced functional materials for a wide range of applications. [PERSON] et al., published a recent review that focuses on the synthesis, characterization, and analytical applications of nanoflowers. The review covers a range of synthesis techniques, including sol-gel, hydrothermal and biosynthesis [33]. To date, nanoflowers with metal compositions present certain challenges, particularly in design strategies, as their performance can vary significantly depending on the approach used [35]. This complexity has led to inconsistent experimental results. For example, copper ions have been shown to negatively affect the enzyme \(\beta\)-galactosidase [37], while for other proteins like lacase, copper ions in the nanoflower structure can enhance the enzyme's activity, as seen in the case of Cu\({}_{3}\)(PO\({}_{4}\))\({}_{2}\) NFs [31]. To address this issue, one potential solution is to develop new nanostructured materials that combine multiple metals and allow precise control over the metal ratio. Such a fine manipulation of metal oxides can significantly impact performance, making it challenging to select the ideal candidate for specific applications. However, the use of mixed-metal nanoparticles offers various benefits [38; 39; 40], such as improved attributes through synergistic effects, tailored functionalities, stability and cost efficiency. Given the scarcity of comprehensive reviews on the applications of NFs, particularly those with metallic compositions, this review aims to outline the role of iron- and copper-based NFs in cancer theranostics. First, we elaborate on the mechanisms of various synthetic methods based on previously reported strategies.