LAPONITE® nanodisk-"decorated" Fe3O4 nanoparticles: a biocompatible nano-hybrid with ultrafast magnetic hyperthermia and MRI contrast agent ability.

Magnetic Fe3O4 nanoparticles "decorated" by LAPONITE® nanodisks have been materialized utilizing the Schikorr reaction following a facile approach and tested as mediators of heat for localized magnetic hyperthermia (MH) and as magnetic resonance imaging (MRI) agents. The synthetic protocol involves the interaction between two layered inorganic compounds, ferrous hydroxide, Fe(OH)2, and the synthetic smectite LAPONITE® clay Na0.7+[(Si8Mg5.5Li0.3)O20(OH)4]0.7-, towards the formation of superparamagnetic Fe3O4 nanoparticles, which are well decorated by the diamagnetic clay nanodisks. The latter imparts high negative ζ-potential values (up to -34.1 mV) to the particles, which provide stability against flocculation and precipitation, resulting in stable water dispersions. The obtained LAPONITE®-"decorated" Fe3O4 nanohybrids were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), Mössbauer spectroscopy, dynamic light scattering (DLS) and vibrating sample magnetometry (VSM) at room temperature, revealing superior magnetic hyperthermia performance with specific absorption rate (SAR) values reaching 540 W gFe-1 (28 kA m-1, 150 kHz) for the hybrid material with a magnetic loading of 50 wt% Fe3O4/LAPONITE®. Toxicity studies were also performed with human glioblastoma (GBM) cells and human foreskin fibroblasts (HFF), which show negligible to no toxicity. Furthermore, T2-weighted MR imaging of rodent brain shows that the LAPONITE®-"decorated" Fe3O4 nanohybrids predominantly affected the transverse T2 relaxation time of tissue water, which resulted in a signal drop on the MRI T2-weighted imaging, allowing for imaging of the magnetic nanoparticles.

Novel nanohybrids derived from the attachment of FePt nanoparticles on carbon nanotubes.

Multiwalled carbon nanotubes (MWCNTs) were used as nanotemplates for the dispersion and stabilization of FePt nanoparticles (NPs). Pre-formed capped FePt NPs were connected to the MWCNTs external surface via covalent binding through organic linkers. Free FePt NPs and MWCNTs-FePt hybrids were annealed in vacuum at 700 degrees C in order to achieve the L1(0) ordering of the FePt phase. Both as prepared and annealed samples were characterized and studied using a combination of experimental techniques, such as Raman and Mössbauer spectroscopies, powder X-ray Diffraction (XRD), magnetization and transmittion electron microscopy (TEM) measurements. TEM measurements of the hybrid sample before annealing show that a fine dispersion of NPs along the MWCNTs surface is achieved, while a certain amount of free particles attached to each other in well connected dense assemblies of periodical or non-periodical particle arrangements is also observed. XRD measurements reveal that the FePt phase has the face-centered cubic (fcc) disordered crystal structure in the as prepared samples, which is transformed to the face-centered tetragonal (fct) L1(0) ordered crystal structure after annealing. An increase in the average particle size is observed after annealing, which is higher for the free NPs sample. Superparamagnetic phenomena due to the small FePt particle size are observed in the Mössbauer spectra of the as prepared samples. Mössbauer and magnetization measurements of the MWCNTs-FePt hybrids sample reveal that the part of the FePt particles attached to the MWCNTs surface shows superparamagnetic phenomena at RT even after the annealing process. The hard magnetic L1(0) phase characteristics are evident in the magnetization measurements of both samples after annealing, with the coercivity of the hybrid sample over-scaling that of the free NPs sample by a factor of 1.25.