Reversible rearrangement of magnetic nanoparticles in solution studied using time-resolved SAXS method.

Lanqing Huang,Xuanxuan Li,Siying Qin,Can Xie,Peilin Yang,Qihui Zhu,Jingeng Mai,Xiaotian Wang,Zhen Guo,Qining Wang,Haiguang Liu,Na Li,Yingchen Shi

doi:10.1107/s1600577519004909

Abstract

Superparamagnetic nanoparticles have broad applications in biology and medicines. Quantitative measurements of magnetic beads in solution are essential in gaining comprehensive understanding of their dynamics and developing applications. Here, using synchrotron X-ray sources combined with well controlled magnetic fields, the results from small-angle X-ray scattering (SAXS) experiments on superparamagnetic particles in solution under the influence of external magnetic fields are reported. The particles mostly remain in monodispersed states and the linear aggregates tend to be aligned with the external magnetic field. After removing the magnetic fields, the superparamagnetic nanoparticles quickly recover to their original states indicating high reversibility of the rearrangement under the control of a magnetic field. The external magnetic field instrument composed of paired permanent magnets is integrated into the SAXS beamline at the Shanghai Synchrotron Radiation Facility providing a platform for studying time-resolved dynamics induced by magnetic fields.

Highlights

Superparamagnetic nanoparticles (SMNPs) are magnetic particles that are sufficiently small to be considered as composed of single magnetic domains, such that an external magnetic field (MF) can magnetize the particles with high magnetic susceptibility (Akbarzadeh et al, 2012)
The chain-like assemblies were observed to be aligned with the direction of the external MF
As revealed from the 2D scattering patterns and 1D radial profiles, SMNPs in solutions quickly recover to their original states after the removal of the external MF

Summary

Introduction

Superparamagnetic nanoparticles (SMNPs) are magnetic particles that are sufficiently small to be considered as composed of single magnetic domains, such that an external magnetic field (MF) can magnetize the particles with high magnetic susceptibility (Akbarzadeh et al, 2012). In the absence of an external MF, the magnetization of such nanoparticles can randomly flip directions because of thermal fluctuations at finite temperatures. These nanoparticles have important applications in biological and biomedical sciences, such as controlled drug delivery (Gupta & Wells, 2004; Neuberger et al, 2005; Xu & Sun, 2013), cell/tissue labelling or imaging contrast enhancer (Chouly et al, 1996; Thorek et al, 2006), and reaction catalysis (Fan & Gao, 2006; Akbarzadeh et al, 2012; Dalpozzo, 2015).

Methods

Results

Conclusion