Water-Dispersible and Biocompatible Iron Carbide Nanoparticles with High Specific Absorption Rate

Abstract

Magnetic nanoparticles are important tools for biomedicine, where they serve as versatile multifunctional instruments for a wide range of applications. Among these applications, magnetic hyperthermia is of special interest for the destruction of tumors and triggering of drug delivery. However, many applications of magnetic nanoparticles require high-quality magnetic nanoparticles displaying high specific absorption rates (SARs), which remains a challenge today. We report here the functionalization and stabilization in aqueous media of highly magnetic 15 nm iron carbide nanoparticles featuring excellent heating power through magnetic induction. The challenge of achieving water solubility and colloidal stability was addressed by designing and using specific dopamine-based ligands. The resulting nanoparticles were completely stable for several months in water, phosphate, phosphate-buffered saline, and serum-containing media. Iron carbide nanoparticles displayed high SARs in water and viscous media (water/glycerol mixtures), even after extended exposition to water and oxygen (SAR up to 1000 W·g^-1 in water at 100 kHz, 47 mT). The cytotoxicity and cellular uptake of iron carbide nanoparticles could be easily tuned and were highly dependent on the chemical structure of the ligands used.

Keywords: biocompatibility; functionalization; iron carbide; magnetic hyperthermia; nanoparticles.

Figure 1:

Dopamine-based ligand structural design.

Figure 2:

(a,b) ICNPs in mesitylene, (c,d) functionalized ICNPs in water. DLS analysis of functionalized ICNPs in aqueous media as a function of time and temperature: (e,f) functionalized with DOP-TEG-C₆; (g,h) functionalized with DOP-TEG-COOH; (i,j) functionalized with DOP-TEG-Zwitter. PBS = Phosphate-Buffered Saline.

Figure 3:

Magnetic properties of ICNPs before (as synthesized) and after 4 months exposure to water and air (functionalized ICNPs, DOP-TEG-C₆ ligand). (a) VSM analysis at 300 K, (b) SAR measurement at 100 kHz.

Figure 4:

Cytotoxicity of different [ICNPs-ligand] systems as a function of the incubation time and of the ICNPs concentration of the incubation media. Color code: [100–80%]: green; [80–60%]: yellow; [60–0%]: red.