Francisco J. Teran

Controlled synthesis of uniform magnetite nanocrystals with high-quality properties for biomedical applications

Uniform iron oxide magnetic nanoparticles, with sizes in the range 9–22 nm, have been synthesized by thermal decomposition of an iron oleate complex in 1-octadecene, controlling reaction parameters related to the nucleation and growth processes. After transferring to water through a ligand substitution process, nanoparticles display very good magnetic and magneto-thermal properties. The relationship between these properties and the size and size distribution of the particles is discussed. The colloidal stability of the nanoparticles dispersed in common biological buffers has also been studied.

Highly asymmetric magnetic behavior in exchange biased systems induced by noncollinear field cooling

A detailed study of the angular dependence of the magnetization reversal in polycrystalline ferromagnetic (FM)/antiferromagnetic Co/IrMn bilayers with noncollinear FM and unidirectional anisotropies shows a peculiar asymmetric magnetic behavior. The anisotropy configuration is set via a field cooling (FC) procedure with the magnetic field misaligned with respect to the easy magnetization direction of the FM layer. Different magnetization reversal modes are observed for either positive or negative angles with respect to the FC direction. The angular dependence of both coercivity and exchange bias also clearly displays the broken symmetry of the induced noncollinearity. Our findings are reproduced with a modified Stoner–Wohlfarth model including the induced anisotropy configuration. Our results highlight the importance of the relative angle between anisotropies in exchange bias systems, opening a new path for the tailoring of their magnetic properties.

BSA-coated magnetic nanoparticles for improved therapeutic properties

In recent years, magnetic nanoparticles have been widely investigated due to their potential in biomedical applications. For successful in vivo applications, magnetic nanoparticles must satisfy several requirements such as biocompatibility, invisibility to the immune system, high colloidal stability in biological fluids, and long blood circulation times. In this study, we have developed a formulation in which the magnetic nanoparticles are coated with bovine serum albumin to provide enhanced colloidal stability in biological fluids preserving their magnetic properties. In addition, the nanoparticles carry a chemotherapeutic drug, showing their potential as drug delivery systems. Our results reveal the influence of protein adsorption on the colloidal stability and the dynamical magnetic response of functionalized magnetic nanoparticles. Moreover, cellular internalization and in vitro cytotoxic activity in Panc-1 pancreatic cancer cells reveal enhanced cellular internalization, successful intracellular drug delivery, and efficient anticancer activity.

Safety assessment of chronic oral exposure to iron oxide nanoparticles.

Iron oxide nanoparticles with engineered physical and biochemical properties are finding a rapidly increasing number of biomedical applications. However, a wide variety of safety concerns, especially those related to oral exposure, still need to be addressed for iron oxide nanoparticles in order to reach clinical practice. Here, we report on the effects of chronic oral exposure to low doses of γ-Fe2O3 nanoparticles in growing chickens. Animal observation, weight, and diet intake reveal no adverse signs, symptoms, or mortality. No nanoparticle accumulation was observed in liver, spleen, and duodenum, with feces as the main excretion route. Liver iron level and duodenal villi morphology reflect the bioavailability of the iron released from the partial transformation of γ-Fe2O3 nanoparticles in the acid gastric environment. Duodenal gene expression studies related to the absorption of iron from γ-Fe2O3 nanoparticles indicate the enhancement of a ferric over ferrous pathway supporting the role of mucins. Our findings reveal that oral administration of iron oxide nanoparticles is a safe route for drug delivery at low nanoparticle doses.

Role of anisotropy configuration in exchange-biased systems

We present a systematic study of the anisotropy configuration effects on the magnetic properties of exchange-biased ferromagnetic/antiferromagnetic (FM/AFM) Co/IrMn bilayers. The interfacial unidirectional anisotropy is set extrinsically via a field cooling procedure with the magnetic field misaligned by an angle bFC with respect to the intrinsic FM uniaxial anisotropy. High resolution angular dependence in-plane resolved Kerr magnetometry measurements have been performed for three different anisotropy arrangements, including collinear bFC ¼ 0 � and two opposite noncollinear cases. The symmetry breaking of the induced noncollinear configurations results in a peculiar nonsymmetric magnetic behavior of the angular dependence of magnetization reversal, coercivity, and exchange bias. The experimental results are well reproduced without any fitting parameter by using a simple model including the induced anisotropy configuration. Our finding highlights the importance of the relative angle between anisotropies in order to properly account for the magnetic properties of exchange-biased FM/AFM systems. V C 2011 American Institute of

Functionalized magnetic nanowires for chemical and magneto-mechanical induction of cancer cell death

Exploiting and combining different properties of nanomaterials is considered a potential route for next generation cancer therapies. Magnetic nanowires (NWs) have shown good biocompatibility and a high level of cellular internalization. We induced cancer cell death by combining the chemotherapeutic effect of doxorubicin (DOX)-functionalized iron NWs with the mechanical disturbance under a low frequency alternating magnetic field. (3-aminopropyl)triethoxysilane (APTES) and bovine serum albumin (BSA) were separately used for coating NWs allowing further functionalization with DOX. Internalization was assessed for both formulations by confocal reflection microscopy and inductively coupled plasma-mass spectrometry. From confocal analysis, BSA formulations demonstrated higher internalization and less agglomeration. The functionalized NWs generated a comparable cytotoxic effect in breast cancer cells in a DOX concentration-dependent manner, (~60% at the highest concentration tested) that was significantly different from the effect produced by free DOX and non-functionalized NWs formulations. A synergistic cytotoxic effect is obtained when a magnetic field (1 mT, 10 Hz) is applied to cells treated with DOX-functionalized BSA or APTES-coated NWs, (~70% at the highest concentration). In summary, a bimodal method for cancer cell destruction was developed by the conjugation of the magneto-mechanical properties of iron NWs with the effect of DOX producing better results than the individual effects.

Magnetization reversal in half metallic La0.7Sr0.3MnO3 films grown onto vicinal surfaces

We present the study of the magnetic properties of well-characterized epitaxial half metallic La0.7 Sr0.3 MnO3 films grown onto vicinal SrTiO3(001) substrates with different miscut angles. Room temperature high resolution vectorial Kerr magnetometry measurements have been performed at different applied magnetic field directions in the whole angular range. The films present a substrate-induced uniaxial (twofold) magnetic anisotropy originated from in-plane [110]-oriented elongated structures, whereas the strength of this anisotropy increases with the miscut angle of the substrate surfaces. Our results demonstrate that we can artificially control the magnetic anisotropy of epitaxial films, up to 120 nm thick, by exploiting the substrate-induced anisotropy. We also determine in this case the minimum vicinal angle required to get well-defined uniaxial magnetic anisotropy.

Nanoparticle-based hyperthermia distinctly impacts production of ROS, expression of Ki-67, TOP2A, and TPX2, and induction of apoptosis in pancreatic cancer

So far, the therapeutic outcome of hyperthermia has shown heterogeneous responses depending on how thermal stress is applied. We studied whether extrinsic heating (EH, hot air) and intrinsic heating (magnetic heating [MH] mediated by nanoparticles) induce distinct effects on pancreatic cancer cells (PANC-1 and BxPC-3 cells). The impact of MH (100 µg magnetic nanoparticles [MNP]/mL; H=23.9 kA/m; f=410 kHz) was always superior to that of EH. The thermal effects were confirmed by the following observations: 1) decreased number of vital cells, 2) altered expression of pro-caspases, and 3) production of reactive oxygen species, and 4) altered mRNA expression of Ki-67, TOP2A, and TPX2. The MH treatment of tumor xenografts significantly (P≤0.05) reduced tumor volumes. This means that different therapeutic outcomes of hyperthermia are related to the different responses cells exert to thermal stress. In particular, intratumoral MH is a valuable tool for the treatment of pancreatic cancers.

Cancer treatment using magnetic nanoparticles

Patients suffering from any cancer will benefit from early diagnosis and more effective therapeutic …

Uniaxial magnetic anisotropy induced by vicinal surfaces in half metallic La0.7Sr0.3MnO3 thin films

We present a detailed study of the angular dependence of the magnetization reversal at room temperature of well characterized epitaxial La0.7Sr0.3MnO3 (001) thin films grown onto SrTiO3 (001) vicinal substrates. The step edges at the substrate surface promote a topological modulation of the films along the step direction, breaking the four-fold magneto crystalline symmetry and favoring a two-fold magnetic anisotropy term. The competition between the biaxial and uniaxial anisotropy is depicted within the framework of the current theory, resulting in a vanishing biaxial contribution. The films hence show the magnetization easy (hard) direction parallel (perpendicular) to the steps direction. The thickness-dependent of both anisotropy and magnetization reversal are discussed in terms of topographic changes.