The Effect of Surface Coating of Iron Oxide Nanoparticles on Magnetic Resonance Imaging Relaxivity

Fatemeh Ahmadpoor,Atif Masood,Wolfgang J Parak,Seyed Abbas Shojaosadati,Neus Feliu

doi:10.3389/fnano.2021.644734

Abstract

Iron oxide nanoparticles (IONPs) with acceptable biocompatibility and size-dependent magnetic properties can be used as efficient contrast agents in magnetic resonance imaging (MRI). Herein, we have investigated the impact of particle size and surface coating on the proton relaxivity of IONPs, as well as engineering of small IONPs' surface coating as a strategy for achieving gadolinium-free contrast agents. Accordingly, polymer coating using poly(isobutylene-alt-maleic anhydride) (PMA) with overcoating of the original ligands was applied for providing colloidal stability to originally oleic acid–capped IONPs in aqueous solution. In case of replacement of the original ligand shell, the polymer had been modified with dopamine. Furthermore, the colloidal stability of the polymer-coated IONPs was evaluated in NaCl and bovine serum albumin (BSA) solutions. The results indicate that the polymer-coated IONPs which involved replacement of the original ligands exhibited considerably better colloidal stability and higher proton relaxivity in comparison to polymer-coated IONPs with maintained ligand shell. The highest r2/r1 we obtained was around 300.

Highlights

IntroductionMagnetic iron oxide nanoparticles (IONPs) exhibit unique magnetic properties that make them attractive for different biomedical applications, including drug delivery (Karimi et al, 2016), magnetic resonance imaging (MRI) (Bruns et al, 2009; Kudr et al, 2017; Li et al, 2017; Smith and Gambhir, 2017; Woodard et al, 2018), magnetic particle imaging (Bauer et al, 2015), and magnetic hyperthermia (Laurent et al, 2011; Pardo et al, 2020)
The aim of this work is to prepare Superparamagnetic iron oxide nanoparticles (SPIONs) stabilized with polymer by overcoating and replacement of the original ligand shell methods, in order to elucidate the influence of the polymer type and polymer coating on the corresponding longitudinal (r1) and transverse (r2) relaxivities
Iron oxide nanoparticles (IONPs) of 6, 15, and 18 nm core diameter with a narrow size distribution were synthesized through thermal decomposition, followed by polymer coating with/without replacement of the original ligand shell

Summary

Introduction

Magnetic iron oxide nanoparticles (IONPs) exhibit unique magnetic properties that make them attractive for different biomedical applications, including drug delivery (Karimi et al, 2016), magnetic resonance imaging (MRI) (Bruns et al, 2009; Kudr et al, 2017; Li et al, 2017; Smith and Gambhir, 2017; Woodard et al, 2018), magnetic particle imaging (Bauer et al, 2015), and magnetic hyperthermia (Laurent et al, 2011; Pardo et al, 2020). Superparamagnetic iron oxide nanoparticles (SPIONs) are single-domain IONPs with a diameter of a few to a few tens nanometers that exhibit no remanent magnetization in the absence of an external magnetic field at room temperature. SPIONs-based T2 contrast agents generate dark signal in T2-weighted MRI that can mislead the clinical diagnosis (Zhao et al, 2013; Fernández-Barahona et al, 2020).

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