Magnetic Field-Induced Polymerization of Molecularly Imprinted Polymers

In this work, we developed a novel approach for the preparation of molecularly imprinted polymer (MIP) coatings directly onto magnetic multicore nanoparticles (MMCs) using alternating magnetic fields to trigger the polymerization reaction. MIPs were synthesized with rhodamine 123 (R123) as model template molecule, methacrylic acid as functional monomer, and trimethylolpropane trimethacrylate as cross-linker. The amount of iron oxide nanoparticles and the composition of the polymerization mixture were optimized to enable the thermal polymerization of a thin MIP shell on each MMC using electromagnetic heating without altering the properties of the recognition layer. The thickness of the polymerized MIP layer grafted onto the MMCs was fine-tuned by adjusting the dose of electromagnetic field (101.4 kHz, total power dissipation = 105 W). The resulting magnetic multicore MIP nanoparticles (MMC-MIPs) were characterized by Fourier transform infrared and X-ray diffraction spectroscopy, transmission electron microscopy, and dynamic light scattering

Thermal Route for the Synthesis of Maghemite/Hematite Core/Shell Nanowires

Nowadays, iron oxide-based nanostructures are key materials in many technological areas. Their physical and chemical properties can be tailored by tuning the morphology. In particular, the possibility of increasing the specific surface area has turned iron oxide nanowires (NWs) into promising functional materials in many applications. Among the different possible iron oxide NWs that can be fabricated, maghemite/hematite iron oxide core/shell structures have particular importance since they combine the magnetism of the inner maghemite core with the interesting properties of hematite in different technological fields ranging from green energy to biomedical applications. However, the study of these iron oxide structures is normally difficult due to the structural and chemical similarities between both iron oxide polymorphs. In this work, we propose a route for the synthesis of maghemite/hematite NWs based on the thermal oxidation of previously electrodeposited iron NWs. A detailed spectroscopic analysis based on Raman, Mössbauer, and X-ray absorption shows that the ratio of both oxides can be controlled during fabrication. Transmission electron microscopy has been used to check the core/shell structure of the NWs. The biocompatibility and capability of internalization of these NWs have also been proven to show the potential of these NWs in biomedical applications

High-Performance Implantable Sensors based on Anisotropic Magnetoresistive La_0.67Sr_0.33MnO₃ for Biomedical Applications

We present the design, fabrication, and characterization of an implantable neural interface based on anisotropic magnetoresistive (AMR) magnetic-field sensors that combine reduced size and high performance at body temperature. The sensors are based on La0.67Sr0.33MnO3 (LSMO) as a ferromagnetic material, whose epitaxial growth has been suitably engineered to get uniaxial anisotropy and large AMR output together with low noise even at low frequencies. The performance of LSMO sensors of different film thickness and at different temperatures close to 37 °C has to be explored to find an optimum sensitivity of ∼400%/T (with typical detectivity values of 2 nT·Hz–1/2 at a frequency of 1 Hz and 0.3 nT·Hz–1/2 at 1 kHz), fitted for the detection of low magnetic signals coming from neural activity. Biocompatibility tests of devices consisting of submillimeter-size LSMO sensors coated by a thin poly(dimethyl siloxane) polymeric layer, both in vitro and in vivo, support their high suitability as implantable detectors of low-frequency biological magnetic signals emerging from heterogeneous electrically active tissues