Targeted magnetic iron oxide nanoparticles: Preparation, functionalization and biomedical application

Iron oxide nanoparticles (IONPs) gained a lot of interest in biomedical research and have been approved for clinical application for years. IONPs are tamed for use in several biomedical applications such as hyperthermia, drug delivery, magnetic resonance imaging and theranostics. Hence, they perform multiple tasks in the treatment, diagnosis and targeting of diseases like cancer. The unique physical and chemical properties of IONPs allowed conducing further modifications improving their biocompatibility, targeting ability and circulation retention time. These modifications include biocompatible polymer coating, ligand functionalization and more which are called surface decorations. This paper reviews the biomedical applications of IONPs, gives a brief idea about the most common preparation methods including; co-precipitation, sol-gel method, spray/laser pyrolysis and sonolysis, and spots their main drawbacks and how to reduce them via surface modifications. These surface modifications like coating performs various functions on molecular, physical and biological behavior of IONPs after in vivo administration. Surface coating not only improves the drug pharmacodynamics but also optimizes the pharmacokinetics of the body via escaping the rapid elimination "stealth effect" and increasing the retention time of the nano-system within the body. The other face of surface modifications is the ligand functionalization as a targeting tool which is discussed in detail at receptor-mediated endocytosis targeting method. This review covered possible methods of targeting IONPs to the specific site of action either by direct local injection, enhanced permeability and retention of the tumor or diseased tissue, external magnetic field guidance, or receptor-mediated endocytosis based on over-expressed receptors on target cell.