Magnetic hydrogels form a class of soft materials with remote controllable properties that have attracted great attention due to their applications in biomedical engineering, including tissue engineering, drug delivery and release, enzyme immobilization and cancer therapy.
The production of hydrogels was carried out through condensation of prepolymers – polyacrylamide with MM = 40 kDa and polyhydroxyacrylamide with MM = 60 kDa in an aqueous solution. By this method hydrogels with incorporated magnetite nanoparticles (Fe3O4) or magnetite precursors (ferrum salts) were obtained. Investigated the influence of introducing into the hydrogel system of magnetite particles or their precursors on the parameters of hydrogel swelling. Established the effects of addition of additives on the dynamics of hydrogels formation, and on their characteristics depending on the ratio of prepolymers. At the ratio of polyacrylamide : poly-N-hydroxyacrylamide, as 1 to 0.6, the introduction of magnetite particles or their precursors during the structuring time of 12 hours at a temperature of 343 K ensures the achievement of stable hydrogel characteristics that are independent from the presence of inorganic components in the gel-forming composition.
For the synthesis of dispersions of the particles of the hydrogel, filled with magnetite or magnetite precursors (ferrum salts) was used dispergation of an aqueous composition of prepolymers with fillers in oleophase. Investigation of the stability of the reverse emulsions of a solution of prepolymers in water and in various organic phases (cyclohexane, toluene, and vaseline oil) showed that the most optimal oleophase is a mixture of cyclohexane : vaseline oil, in the ratio 40 : 60, respectively, using a mixture of surfactant compounds Tween 40 : Span 80 as 20 : 80.
The introduction of additives has a different effect on the formation of dispersions during structuring of prepolymers in the emulsion. Magnetite in the composition of the gelling composition while structuring of the particles of hydrogel reduces their stability (a significant amount of coagulum is formed), at the same time the particles obtained based on the composition containing the ferrum salts in the aqueous phase retained stability.
The resulting dispersions with hydrogel particles of 5 to 10 μm in the state of maximum swelling, that were filled with the salts of ferrum after treatment in ammonia vapor exhibit magnetically sensitive properties, which makes it easy to remove them from the reaction medium. Hydrogel particles of this size can serve as carriers of enzyme preparations and are most suitable for use in the processes of biotechnology.
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