Spin Labels in the Investigation of Macromolecules Adsorption on Magnetic Nanoparticles

The new application aspect of spin labels technique to macromolecular adsorption on magnetic nanoparticles and quantitative adsorption layer characterization was developed. The technique is based on measurement of ESR signal intensity of stable nitroxide radicals, covalently bound to macromolecules. As a result of spin-labeled macromolecules adsorption on the nanoparticles surface ESR spectra lines broaden due to dipole-dipole interaction of unpaired electrons of radical with particles magnetic moment. This leads to signal intensity decreasing. Multilayer adsorption of biological macromolecules - fibrinogen and albumin, and also synthetic polymer - polyethyleneimine on magnetite particles with average diameter 17 nm was studied. It was shown that the method is applicable for adsorbed macromolecules number evaluation when the thickness of multilayer coat is up to 40 nm.