Engineering Core-Shell Structures of Magnetic Ferrite Nanoparticles for High Hyperthermia Performance.

Magnetic ferrite nanoparticles (MFNs) with high heating efficiency are highly desirable for hyperthermia applications. As conventional MFNs usually show low heating efficiency with a lower specific loss power (SLP), extensive efforts to enhance the SLP of MFNs have been made by varying the particle compositions, sizes, and structures. In this study, we attempted to increase the SLP values by creating core-shell structures of MFNs. Accordingly, first we synthesized three different types of core ferrite nanoparticle of magnetite (mag), cobalt ferrite (cf) and zinc cobalt ferrite (zcf). Secondly, we synthesized eight bi-magnetic core-shell structured MFNs; Fe3O4@CoFe2O4 (mag@cf1, mag@cf2), CoFe2O4@Fe3O4 (cf@mag1, cf@mag2), Fe3O4@ZnCoFe2O4 (mag@zcf1, mag@zcf2), and ZnCoFe2O4@Fe3O4 (zcf@mag1, zcf@mag2), using a modified controlled co-precipitation process. SLP values of the prepared core-shell MFNs were investigated with respect to their compositions and core/shell dimensions while varying the applied magnetic field strength. Hyperthermia properties of the prepared core-shell MFNs were further compared to commercial magnetic nanoparticles under the safe limits of magnetic field parameters (<5 × 109 A/(m·s)). As a result, the highest SLP value (379.2 W/gmetal) was obtained for mag@zcf1, with a magnetic field strength of 50 kA/m and frequency of 97 kHz. On the other hand, the lowest SLP value (1.7 W/gmetal) was obtained for cf@mag1, with a magnetic field strength of 40 kA/m and frequency of 97 kHz. We also found that magnetic properties and thickness of the shell play critical roles in heating efficiency and hyperthermia performance. In conclusion, we successfully enhanced the SLP of MFNs by engineering their compositions and dimensions.

Facile and controllable electrochemical fabrication of cell-adhesive polypyrrole electrodes using pyrrole-RGD peptides.

Electrically conductive polymers, such as polypyrrole (PPy), have been widely used for the fabrication of various biosensors and tissue engineering scaffolds. For their biologically relevant applications, conductive biomaterials capable of intimate cellular interactions are highly desired. However, conventional methods to incorporate biomolecules into conductive polymers do not offer fine and easy control over the surface density of the biomolecules and/or their stability. We present a novel method to electrochemically immobilize cell-adhesive Arg-Gly-Asp (RGD) ligands on PPy electrode surfaces with a simple control over the peptide surface density by varying the electrodeposition time. Synthesized pyrrole-GGGRGDS conjugates were electrochemically incorporated onto the surfaces of PPy-coated electrodes. The electrochemical impedances of the RGD-grafted PPy electrodes were not significantly different from the unmodified PPy films. Time-of-flight secondary-ion mass spectroscopy confirmed the presence of the RGD motif on the surface of the modified electrodes. In vitro studies with human mesenchymal stem cells (hMSCs) showed higher adhesion and faster proliferation of hMSCs on the PPy with a higher RGD density. This facile electrochemical modification of electrode surfaces allowed for a good control over the peptide surface density and cellular interactions and will benefit the fabrication of cell-interactive scaffolds or bio-electrodes.