Atomic force microscopy characterization of ultrasound-sensitive nanocomposite microcapsules

Polyelectrolyte and nanocomposite microcapsules with shells containing iron oxide (Fe3O4 magnetite) nanoparticles have been obtained using the layer-by-layer polyion assembly technique. The volume fraction of nanoparticles was varied by changing the number of their layers in the shell. The dependence of the microcapsule shell thickness on its structure, that is, on the total number of polyelectrolyte and magnetite nanoparticle layers, has been studied using atomic force microscopy. An increase in the number of polyelectrolyte layers in the shell structure leads to nonlinear growth of the shell thickness. Remote control over the permeability of microcapsules was achieved by their destruction under the action of an external acoustic (ultrasound) field. It has been established that the sensitivity of microcapsules to ultrasound depends on the volume fraction of magnetite nanoparticles in the shell. The ultrasonic treatment only produces breakage of the shells, without reducing their thickness and/or changing the composition. The results of this investigation can be used for to develop systems (in particular, magnetically sensitive) for targeted drug delivery and remote controlled release in the immediate vicinity of damaged cells and tissues in an organism.