# Magnetic Nanoparticles: Synthesis, Characterization, and Their Use in Biomedical Field
## 2 Synthesis Methods
### Biological Methods  
The field of nanotechnology has witnessed the rise of a significant field known as biological synthesis of magnetic nanoparticles (MNPs). This approach offers an environmentally friendly and sustainable alternative to conventional physical and chemical manufacturing techniques. This method employs biological entities, such as microorganisms, plant extracts, and enzymes, to synthesize MNPs. Each of these biological entities holds distinct advantages and is suited for a range of applications, as follows:  
* **Microorganism-based synthesis** involves the utilization of microorganisms, including bacteria, fungi, viruses, and actinomycetes, to generate MNPs. The presence of microorganisms greatly enhances the efficiency of metal ion reduction, hence facilitating NP synthesis. Magnetotactic bacteria are renowned for their ability to synthesize MNPs intracellularly. The nanoparticles are employed for orienting themselves in geomagnetic fields [68; 69]. Furthermore, the use of fungi in the production of MNPs has been extensively recorded. Various fungal species have been recognized for their ability to generate iron oxide nanoparticles, which have significant promise in the domains of remediation and biomedicine [70; 71].
* **Plant extracts**, including phytochemicals, are utilized in the manufacture of nanoparticles. They serve as both reducing and stabilizing agents. This is achieved through the utilization of botanical extracts. The method's simplicity, cost-effectiveness, and scalability are driving its increasing worldwide popularity. Numerous plants have been employed for this objective. Diverse parts of plants such as leaves, stems, and roots were employed to provide the necessary bioactive constituents. For instance, the utilization of plant extracts, such as aloe vera and green tea, has proven to be successful in the production of IONPs. The nanoparticles showed promise in the areas of drug delivery and magnetic resonance imaging (MRI) applications [34; 72].
* **Enzymatic synthesis** process employs specific enzymes to catalyze the reduction of metal ions in order to produce metal nanoparticles. Enzymes have significant control over the nucleation and growth processes, leading to the formation of NPs that exhibit a uniform size and shape. The enzymatic approach is extremely intriguing for use in medical and pharmaceutical areas due to its exceptional biocompatibility and precision. Several enzymes are currently under investigation [72; 73] as a direct consequence of growing research efforts in this area. Moreover, some protein assisted synthesis models were implemented for biosensing applications [74].  
Since these methods apply biological principles for nanoparticle formation, they are also called biomimetic synthesis procedures [75]. These techniques are not only environmentally benign, but they yield products that are highly suitable for delicate applications such as drug administration, bioimaging, and environmental remediation. Due to their high biocompatibility and minimal environmental impact, they represent a very promising research topic in the field of nanotechnology.