Magnetic materials were suggested as carriers for protein immobilization about 10 years ago [1,2]. The main advantage of these carriers is their ability to be concentrated near magnetic terminals upon the application of the external magnetic field. This property is used in technological processes for selective catalyst removal from the reaction mixture [3], in immunological studies for the separation of cells to which magnetic particles are specifically bound modified with antibodies against cell surface components [4], in experiments for the drug targeting in vivo into appropriate tissues under the action of external magnetic field [5]. The properties of magnetic carriers are reviewed in [3].
There exist a number of methods to obtain porous magnetic carriers, containing immobilized matter not only on the surface, but also in the volume of a particle. Normally, these preparations are obtained by the granule formation from the suspension of ferromagnetic particles in the solution or melt of appropriate high-molecular-weight com-' pound [5,6].
The drawback of the above-mentioned methods is the pronounced aggregation of ferromagnetic particles. The aggregation does not permit to use concentrated enough suspensions of magnetic particles and causes the formation of the product with a variety of sizes and magnetic properties.
We made an attempt to synthesize the magnetic carrier for protein immobilization on the basis of commercial Sephadex porous spheres. Sephadex granules were made magnetic by adsorptional fixation of ferromagnetic particles in its pores. The properties of the "native" and "magnetic" Sephadexes as carriers for protein immobilization were compared by parallel immobilization on both carriers of a-chymotrypsin and '311-albumin.
In in vivo experiments we studied the ability of magnetic Sephadex to be concentrated in a desired region of the circulation under the action of external magnetic field.
Methods
The following reagents were used: Sephadexes G-25, G-50 (pharmacia), cyanogenbromide (Merk), a -chymotrypsin (Koch-Light and Reakhim), "'I-albumin (Reakhim). All other reagents, salts and buffer solution components were analytical grade preparations (Merk and Reakhim).