REVIEW Recent Advances in Iron Oxide Nanoparticles (IONPs): Synthesis and Surface Modification for Biomedical Applications Osama Abu Noqta 1,2 & Azlan Abdul Aziz 1,2 & Ibrahim Adamu Usman 1,2 & M. Bououdina 3 Received: 10 September 2018 /Accepted: 8 November 2018 # Springer Science+Business Media, LLC, part of Springer Nature 2018 Abstract In recent years, extensive researches were devoted to iron oxide nanoparticles (IONPs), including magnetite (Fe 3 O 4 ) and maghemite (γ-Fe 2 O 3 ), due to their low toxicity and cost, in addition to their unique physicochemical and magnetic properties. In this review, we present a brief introduction on IONPs in terms of classification and properties. Because the synthesis approach and surface modification are found to be key factors for better control of particle morphology and shape, as well as to produce monodispersed IONPs, which have direct influence on their properties and applications, particular emphasis will be given to the chemical synthesis methods and surface modifications by several organic materials such as polyvinylpyrrolidone (PVP), chito- san, and cetyltrimethylammonium bromide (CTAB). Recent trends and future prospects in this research field are also discussed. Keywords Surface modification . Iron oxide . Nanoparticles . Capping agent . Biomedical application 1 Introduction In recent years, iron oxide nanoparticles (IONPs) have attracted widespread attention due to their biocompatibility, low cost, chemically stable, and unique magnetic features. These unique properties of IONPs make them widely intrinsic for great biomedical applications, such as magnetic resonance (MR) contrast agents [1], bioseparation [2], tissue repair [3], and hyperthermia [4]. However, IONPs are one of the most commonly inorganic chemical compounds with diameters ranging from 1 to100 nm. It exhibit superparamagnetic behav- ior at particle size decreases less than 30 nm at room temper- ature [5]. In biomedical application, the main drawbacks of IONPs are agglomeration and lack of control on the particle size. The agglomeration of IONPs is due to high surface area, Van der Waals forces of attraction, and dipole-to-dipole interactions between the nanoparticles [6]. Therefore, the use of surfac- tants during the IONP synthesis plays important role to control the nucleation and growth as well as to avoid the agglomera- tion of nanoparticles [7, 8]. Numerous organic and inorganic materials, such as cetyltrimethylammonium bromide (CTAB), chitosan, polyvinylpyrrolidone (PVP), silica, and gold [9–14], have been used for modifying the surface of IONPs as well as preventing the agglomeration through either electrostatic re- pulsion or steric stabilization. This review focuses on the chemical synthesis methods and surface modification techniques of IONPs by several organic materials. The surface modification is presented with several organic coatings such as PVP, chitosan, CTAB, and citrate. Finally, the recent progress made in the usage of IONPs in biomedical applications will be discussed. * Osama Abu Noqta Osama1987ahmad@yahoo.com * Azlan Abdul Aziz lan@usm.my 1 Nano-Biotechnology Research and Innovation (NanoBRI), Universiti Sains Malaysia, Institute for Research in Molecular Medicine (INFORMM), 11800 Pulau Pinang, Malaysia 2 Nano-Optoelectronic Research and Technology Lab (NORLab), School of Physics, Universiti Sains Malaysia, 11800 Pulau Pinang, Malaysia 3 Department of Physics, College of Science, University of Bahrain, Zallaq, Kingdom of Bahrain Journal of Superconductivity and Novel Magnetism https://doi.org/10.1007/s10948-018-4939-6