In vitro characterization of movement, heating and visualization of magnetic nanoparticlesfor biomedical applications

Abstract

Magnetic nanoparticles can be used for a variety of biomedical applications. They can beused in the targeted delivery of therapeutic agents in vivo, in the hyperthermic treatmentof cancers, in magnetic resonance (MR) imaging as contrast agents and in the biomagneticseparations of biomolecules. In this study, a characterization of the movement and heatingof three different types of magnetic nanoparticles in physiological systems in vitro is madein a known external magnetic field and alternating field respectively. Infra-red (IR) imagingand MR imaging were used to visualize these nanoparticles in vitro. A strongdependence on the size and the suspending medium is observed on the movementand heating of these nanoparticles. First, two of the particles (mean diameterd = 10 nm, uncoatedFe3O4 andd = 2.8 µm, polystyrenecoated Fe3O4+γ-Fe2O3) did not move while only a dextran coated nanoparticle(d = 50 nm, γ-Fe2O3) moved in type 1 collagen used as an in vitro model system. It is also observed that the timetaken by a collection of these nanoparticles to move even a smaller distance (5 mm) in collagen(∼100 min) isalmost ten times higher when compared to the time taken to move twice the distance (10 mm) in glycerol(∼10 min) under the same external field. Second, the amount of temperature rise increases withthe concentration of nanoparticles regardless of the microenvironments in the heatingstudies. However, the amount of heating in collagen (maximum change in temperatureΔTmax∼9 °C at1.9 mg Fe ml−1 and19 °C at3.7 mg Fe ml−1) is significantly lessthan that in water (ΔTmax∼15 °C at 1.9 mg Fe ml−1 and33 °C at3.7 mg Fe ml−1) andglycerol (ΔTmax∼13.5 °C at 1.9 mg Fe ml−1 and 30 °C at 3.7 mg Fe ml−1). Further, IR imaging provides at least a ten times improvement in therange of imaging magnetic nanoparticles, whereby a concentration of(0–4 mg Fe ml−1) could bevisualizedas compared to (0–0.4 mg Fe ml−1) by MR imaging. Based on these in vitro studies, important issues and parameters thatrequire further understanding and characterization of these nanoparticles in vivo arediscussed.