Release of TRITC-Dextran from Composite Microcapsules under the Influence of a Low-Frequency Alternating Magnetic Field

— Composite microcapsules based on polyelectrolytes and nanoparticles of iron oxides are synthesized, and the release of encapsulated high-molecular dextran under the influence of a low-frequency alternating magnetic field due to the magnetomechanical actuation of nanoparticles in a polymer shell is investigated. As a result of the chemical condensation of ferrous and ferric iron, single-domain magnetic spherical Fe 3 O 4 nanoparticles are synthesized and characterized by transmission electron microscopy, dynamic light scattering, powder X-ray diffraction, and Mössbauer spectroscopy. Polyelectrolyte microcapsules from polyallylamine hydrochloride and sodium polystyrene sulfonate are modified with magnetic nanoparticles due to electrostatic adsorption on an oppositely charged polyelectrolyte layer. Dextran, labeled with tetramethyl rhodamine-5-isothiocyanate (TRITC-dextran), is used as the model substance for encapsulation; it is incorporated into CaCO 3 particles (soluble cores for the formation of capsules) by coprecipitation. The capsule samples are examined by scanning electron microscopy, dynamic light scattering, and fluorescence confocal microscopy. The capsules are exposed to an alternating magnetic field with an amplitude of 100 mT and frequencies of 30–110 Hz. The content of labeled dextran in the shell of the microcapsules and the supernatant is determined using fluorimetry and fluorescence confocal microscopy. The duration of exposure and the frequency of the magnetic field, at which the maximum release of dextran from composite capsules is achieved, are established. Exposure to a low-frequency alternating magnetic field can lead to significant deformation of the shell of polyelectrolyte microcapsules modified with magnetic nanoparticles and successful release of the encapsulated substance.