# Recent Progress and Challenges Regarding Magnetic-Based Nanoparticles for Targeted Drug Delivery
###### Abstract  
Magnetic-based nanoparticles are of constant interest in the scientific community as potential systems for biomedical applications. Over the years, the ability to synthesize diverse systems based on iron (II, III) oxide nanoparticles has been mastered to maximize their potential effectiveness in the targeted delivery of active substances in cancer therapy. The present review explores recent literature findings that detail various magnetic nanosystems. These encompass straightforward designs featuring a polymer coating on the magnetic core and more intricate matrices for delivering chemotherapeutic drugs. This paper emphasizes novel synthetic approaches that impact the efficacy and progress of anticancer investigations, specifically targeting a particular cancer type. The research also delves into combinations with alternative treatment methods and diagnostic approaches. Additionally, it highlights a critical aspect--the interaction with cells--identifying it as the least developed aspect in current research on these systems. magnetic; targeted drug delivery; chemotherapy; multifunctional nanosystems +
Footnote †: journal: Medical  
coprecipitation method allows for obtaining nanoparticles of uniform sizes, often below 10 nm, but many reports indicate a significant variation in sizes (10-40 nm). Another popular technique is hydrothermal synthesis, which uses high temperature (>200 \({}^{\circ}\)C) and high pressure (>6000 Pa) in a reactor to obtain uniform and homogeneous crystals. The modification of precursor salt, reducing agent, temperature, and solvent type is applied to obtain nanoparticles of the desired morphology. The method enables the fabrication of NPs with high levels of crystallinity and uniform morphology, but process conditions generate high synthesis costs. Higher temperatures are also required in a thermal parsing technique that generates Fe3O4 NPs with controlled size. The procedure includes an oxidation process in high boiling temperature organic solvents with stabilizing surfactants (oleic acid, hexadecylamine). However, such magnetite NPs are only dissolved in non-polar solvents. In turn, sol-gel synthesis belongs to wet chemical processes, and it is based on polycondensation and hydrolysis of precursors to form a colloidal sol, and after drying it (removing the solvent), gel, and finally magnetite nanoparticles. The synthesis results in products with high purity and good crystallinity. Additionally, it allows for the production of homogenous structures without using high temperatures. On the other hand, the completion time is relatively high, and the method requires toxic organic solvents. Another method, sonochemical synthesis, applies ultrasound irradiation for the chemical reaction. Ultrasonic bubbles generate high temperatures, pressures, and a strong impact force, promoting multiple reactions. It allows for the formation of small particles with high crystallinity, narrow size distribution, and limited agglomeration. Unfortunately, it is difficult to control the size and shape of the obtained nanoparticles precisely. In turn, the laser ablation method involves using laser power with energies ranging from 90 to 370 mJ. The particle morphology and size distribution can be controlled by using different laser power and organic solvents. Additionally, the ball milling method belongs to physical top-down approaches that generate nanoparticles by breaking up large pieces of the initial material. The particles can be obtained in a ball mill equipped with jars under dry and wet conditions.