Insights into the Formation of DNA-Magnetic Nanoparticle Hybrid Structures: Correlations between Morphological Characterization and Output from Magnetic Biosensor Measurements.

Understanding the binding mechanism between probe-functionalized magnetic nanoparticles (MNPs) and DNA targets or amplification products thereof is essential in the optimization of magnetic biosensors for the detection of DNA. Herein, the molecular interaction forming hybrid structures upon hybridization between DNA-functionalized magnetic nanoparticles, exhibiting Brownian relaxation, and rolling circle amplification products (DNA-coils) is investigated by the use of atomic force microscopy in a liquid environment and magnetic biosensors measuring the frequency-dependent magnetic response and the frequency-dependent modulation of light transmission. This approach reveals the qualitative and quantitative correlations between the morphological features of the hybrid structures with their magnetic response.

Structural, microstructural and magnetic evolution in cryo milled carbon doped MnAl.

The low cost, rare earth free τ-phase of MnAl has high potential to partially replace bonded NdFeB rare earth permanent magnets. However, the τ-phase is metastable and it is experimentally difficult to obtain powders suitable for the permanent magnet alignment process, which requires the fine powders to have an appropriate microstructure and high τ-phase purity. In this work, a new method to make high purity τ-phase fine powders is presented.

Influence of Cobalt Substitution on the Magnetic Properties of FePB.

The substitutional effects of cobalt in (FeCo)PB have been studied with respect to crystalline structure and chemical order with X-ray diffraction and Mössbauer spectroscopy. The magnetic properties have been determined from magnetic measurements, and density functional theory calculations have been performed for the magnetic properties of both the end compounds, as well as the chemically disordered intermediate compounds. The crystal structure of (FeCo)PB is tetragonal (space group I4/mcm) with two different metal sites, with a preference for cobalt atoms in the M(2) position (4c) at higher cobalt contents.

Magnetophoretic Transport Line System for Rapid On-Chip Attomole Protein Detection.

A lab-on-a-chip traveling wave magnetophoresis approach for sensitive and rapid protein detection is reported. In this method, a chip-based magnetic microarray comprising lines of micrometer-sized thin film magnetic elements was used to control the movement of magnetic beads (MBs). The MBs and the chip were functionalized, forming a sandwich-type assay.

Free-standing magnetic nanopillars for 3D nanomagnet logic.

Nanomagnet logic (NML) is a relatively new computation technology that uses arrays of shape-controlled nanomagnets to enable digital processing. Currently, conventional resist-based lithographic processes limit the design of NML circuitry to planar nanostructures with homogeneous thicknesses. Here, we demonstrate the focused electron beam induced deposition of Fe-based nanomaterial for magnetic in-plane nanowires and out-of-plane nanopillars.

2D to 3D crossover of the magnetic properties in ordered arrays of iron oxide nanocrystals.

The magnetic 2D to 3D crossover behavior of well-ordered arrays of monodomain γ-Fe(2)O(3) spherical nanoparticles with different thicknesses has been investigated by magnetometry and Monte Carlo (MC) simulations. Using the structural information of the arrays obtained from grazing incidence small-angle X-ray scattering and scanning electron microscopy together with the experimentally determined values for the saturation magnetization and magnetic anisotropy of the nanoparticles, we show that MC simulations can reproduce the thickness-dependent magnetic behavior. The magnetic dipolar particle interactions induce a ferromagnetic coupling that increases in strength with decreasing thickness of the array.

Real-space transmission electron microscopy investigations of attachment of functionalized magnetic nanoparticles to DNA-coils acting as a biosensor.

The present work provides the first real-space analysis of nanobead-DNA coil interactions. Immobilization of oligonucleotide-functionalized magnetic nanobeads in rolling circle amplified DNA-coils was studied by complex magnetization measurements and transmission electron microscopy (TEM), and a statistical analysis of the number of beads hybridized to the DNA-coils was performed. The average number of beads per DNA-coil using the results from both methods was found to be around 6 and slightly above 2 for samples with 40 and 130 nm beads, respectively.

A magnetic microchip for controlled transport of attomole levels of proteins.

A novel method of controlled transport of proteins immobilized on micrometre-sized magnetic beads in a lab-on-a-chip environment is presented. Bead motion is controlled by lithographically made magnetic elements forming transportation lines in combination with an applied in-plane rotating magnetic field. In this way, transport of attomole amounts of proteins is controlled with micrometre precision.

Multiplex detection of DNA sequences using the volume-amplified magnetic nanobead detection assay.

The possibility for conducting multiplex detection of DNA-sequences using the volume-amplified magnetic nanobead detection assay [Stromberg, M.; Goransson, J.; Gunnarsson, K.

Sensitive molecular diagnostics using volume-amplified magnetic nanobeads.

In this letter, we demonstrate a new principle for diagnostics based on DNA sequence detection using single-stranded oligonucleotide tagged magnetic nanobeads. The target DNA is recognized and volume-amplified to large coils by circularization of linear padlock probes through probe hybridization and ligation, followed by rolling circle amplification (RCA). Upon hybridization of the nanobeads in the RCA coils, the complex magnetization spectrum of the beads changes dramatically, induced by the attached volume-amplified target molecules.