Long term stability and reproducibility of magnetic colloids are key issues for steady values of Specific Power Absorption through time

TL;DR

This study demonstrates that polymer-coated magnetic nanoparticles in water-based colloids maintain long-term stability and reproducibility of their specific power absorption, crucial for consistent magnetic hyperthermia treatments.

Contribution

It shows that in situ polymer coating ensures long-term stability and reproducibility of SPA in magnetic colloids over one year.

Findings

SPA remains stable over several months

Reproducibility between different synthesis batches achieved

Colloidal stability prevents agglomeration and precipitation

Abstract

Virtually all clinical applications of magnetic nanoparticles (MNPs) require the formulation of biocompatible, water-based magnetic colloids. For magnetic hyperthermia, the requirements also include a high colloidal stability against precipitation and agglomeration of the constituent MNPs, in order to keep the heating efficiency of the ferrofluid in the long term. The specific power absorption (SPA) of single-domain MNPs depends critically on the average particle size and size distribution width, therefore first-rate reproducibility among different batches regarding these parameters are also needed. We have studied the evolution of the SPA of highly reproducible and stable water-based colloid composed of polymer coated $Fe_{3}O_{4}$ magnetic nanoparticles. By measuring the specific power absorption (SPA) values along one year as a function of field amplitude and frequencies ($H \leq 24 kA/m$; $260 \leq f \leq 830 kHz$), we demonstrated that SPA in these samples can be made reproducible between successive synthesis, and stable along several months, due to the in situ polymer coating that provides colloidal stability and keeps dipolar interactions negligible.