Activity of glucose oxidase functionalized onto magnetic nanoparticles

BACKGROUND: Magnetic nanoparticles have been significantly used for coupling with biomolecules, due to their unique properties. METHODS: Magnetic nanoparticles were synthesized by thermal co-precipitation of ferric and ferrous chloride using two different base solutions. Glucose oxidase was bound to the particles by direct attachment via carbodiimide activation or by thiophene acetylation of magnetic nanoparticles. Transmission electron microscopy was used to characterize the size and structure of the particles while the binding of glucose oxidase to the particles was confirmed using Fourier transform infrared spectroscopy. RESULTS: The direct binding of glucose oxidase via carbodiimide activity was found to be more effective, resulting in bound enzyme efficiencies between 94–100% while thiophene acetylation was 66–72% efficient. Kinetic and stability studies showed that the enzyme activity was more preserved upon binding onto the nanoparticles when subjected to thermal and various pH conditions. The overall activity of glucose oxidase was improved when bound to magnetic nanoparticles CONCLUSION: Binding of enzyme onto magnetic nanoparticles via carbodiimide activation is a very efficient method for developing bioconjugates for biological application

New two in one magnetic fluorescent nanocomposites

Magnetite nanoparticles have been coated by a porphyrin derivative to produce new magnetic materials with fluorescent properties. The magnetic nanoparticles were prepared using two different methods, one based on sol-gel techniques and ultrasonic processing, and the other via a controlled chemical co-precipitation. Different types of porphyrin functionalised magnetic nanoparticles have been prepared and have been characterised by electron microscopy (TEM and SEM), XRD, FTIR, Raman, UV-vis, and fluorescence spectroscopy. Microscopy results showed the formation of core-shell nanostructures, with IR and photoluminescence spectroscopy results confirming the presence of porphyrin in the shell

Scaling relations for magnetic nanoparticles

A detailed investigation of the scaling relations recently proposed by [J. d'Albuquerque e Castro, D. Altbir, J. C. Retamal, and P. Vargas, Phys. Rev. Lett. 88, 237202 (2002)] to study the magnetic properties of nanoparticles is presented. Analytical expressions for the total energy of three characteristic internal configurations of the particles are obtained, in terms of which the behavior of the magnetic phase diagram for those particles upon scaling of the exchange interaction is discussed. The exponent $\eta$ in scaling relations is shown to be dependent on the geometry of the vortex core, and results for specific cases are presented.Comment: 6 pages, 4 figure

Multifunctional Nanoparticles for Imaging Guided Interventions

We describe multifunctional magnetic nanoparticles (MNPs) encapsulated in thermosensitive, drug-bearing shells and delivered to the tumor site by genetically modified and non-pathogenic strains of bacteria with known affinity to tumors for an effective and minimally invasive protocol for tumor management. The magnetic nanoparticles also serve as a non-invasive imaging contrast agent, heating agent as well as thermometry monitoring agents. We have shown an efficient tumor management on a mouse model utilizing the MNPs. Our studies showed that these novel MNPs significantly reduce the progress of tumor and prolong the animal life and function as an imaging contrast to visually monitor the tumor treatment and evolution

Tunable Magnetic Relaxation In Magnetic Nanoparticles

We investigate the magnetization dynamics of a conducting magnetic nanoparticle weakly coupled to source and drain electrodes, under the assumption that all relaxation comes from exchange of electrons with the electrodes. The magnetization dynamics is characterized by a relaxation time $t_1$, which strongly depends on temperature, bias voltage, and gate voltage. While a direct measure of a nanoparticle magnetization might be difficult, we find that $t_1$ can be determined through a time resolved transport measurement. For a suitable choice of gate voltage and bias voltage, the magnetization performs a bias-driven Brownian motion regardless of the presence of anisotropy.Comment: 4 pages, 2 eps figure

Thermodynamics of Two Dimensional Magnetic Nanoparticles

A two dimensional magnetic particle in the presence of an external magnetic field is studied. Equilibrium thermodynamical properties are derived by evaluating analytically the partition function. When the external field is applied perpendicular to the anisotropy axis the system exhibits a second order phase transition with order parameter being the magnetization parallel to the field. In this case the system is isomorph to a mechanical system consisting in a particle moving without friction in a circle rotating about its vertical diameter. Contrary to a paramagnetic particle, equilibrium magnetization shows a maximum at finite temperature. We also show that uniaxial anisotropy in a system of noninteracting particles can be missinterpreted as a ferromagnetic or antiferromagnetic coupling among the magnetic particles depending on the angle between anisotropy axis and magnetic field.Comment: 4 pages 6 figures 19 reference