Alexander L. Kovarski

Free-radical cross-linking of serum albumin molecules on the surface of magnetite nanoparticles in aqueous dispersion

A novel universal approach to cross-linking of protein macromolecules on the surface of magnetite nanoparticles has been developed. The approach is based on protein liability to free-radical modification, leading to the formation of intermolecular covalent cross-links. Free radicals are locally generated on the surface of nanoparticles. Stable coatings of serum albumin 3 nm thick are formed on the surface of magnetite nanoparticles. Using a set of physicochemical methods, it has been proven that stable coatings composed of protein macromolecules are formed around individual nanoparticles. The presence of reactive groups in the protein structure makes it possible to perform subsequent modification of the surface layers-in particular, to graft nonprotein drugs. The approach developed can be used to create superfine systems with desired surface properties for targeted delivery of drugs and biologically active substances.

Interaction of fibrinogen with magnetite nanoparticles

The interaction between fibrinogen and magnetite nanoparticles in solution has been studied by the methods of spin labeling, ferromagnetic resonance, dynamic and Rayleigh light scattering. It is shown that protein molecules adsorb on the surface of nanoparticles to form multilayer protein covers. The number of molecules adsorbed on one nanoparticle amounts to ∼65 and the thickness of the adsorption layer amounts to ∼27 nm. Separate nanoparticles with fibrinogen covers (clusters) form aggregates due to interactions of the end D domains of fibrinogen. Under the influence of direct magnetic field, nanoparticles with adsorbed proteins form linear aggregates parallel to the force lines. It is shown that the rate of protein coagulation during the formation of fibrin gel under the action of thrombin on fibrinogen decreases ∼2 times in the presence of magnetite nanoparticles, and the magnitude of the average fiber mass/length ratio grows.

ESR line shape of paramagnetic particles in a magnetic liquid. Theory and experiment

A basic model has been proposed to describe the resonance spectra of the paramagnetic sensor particles in dispersions of magnetic nanoparticles aggregated in chains. A theory of the line shape of low-mobility sensors has been developed in the case of chains of a sufficiently homogeneous length. A specific line shift has been shown to appear in such systems and the spectrum may be asymmetric. The ESR spectra of a magnetite-based magnetic liquid have been measured and the main parameters of the chains have been determined.

Estimation of the Oblongness of Aggregates of Magnetic Particles Formed in Static Magnetic Field Using ESR Spectroscopy

Aggregation process in magnetic fluid has been investigated by electron spin resonance method. A low molecular paramagnet (paramagnetic sensor) has been added to magnetite hydrosol and its ESR spectra have been analyzed. Fraction of aggregated particles and aggregate oblongness have been calculated using new theoretical model for the ESR spectra of paramagnetic sensor in diluted magnetic media containing elongated structures.

Ferromagnetic track-etched membrane for high-gradient magnetic separation

High-gradient magnetic field formed near pores of a ferromagnetic track-etched membrane retains on the membrane surface particles having a higher magnetic permeability than the surrounding medium. The feasibility of capturing particles of aqueous magnetite slurry on the ferromagnetic track-etched membrane has been experimentally shown. Calculation of the field strength near the membrane confirms the experimental results.