Porous vaterite particles as drug delivery system:synthesis, encapsulation, and controlled release

We report on the synthesis and characterization of vaterite microcontainers for controlled drug release. Moreover, we present experiments on possible release strategies of encapsulated substances via recrystallization, pH controlled, or by desorption methods. Vaterite spherical particles were fabricated with controllable average sizes from 400±12nm till 10±1hm. We considered two ways of functionalization of the containers: encapsulation of the substances during the vaterite synthesis or their adsorption onto the prepared particles. As model experiments, vaterite containers, encapsulating Rhodamine 6G, were imaged by two-photon microscopy, showing dye release into the aqueous medium due to recrystallization to calcite within 3 days. Differently, in ethanol only small amounts of the encapsulated markers were diffusion released after one week. The release mechanisms can be further controlled by covering the microcontainers with additional polymer layers to increase diffusion and recrystallization time. A change of the pH from neutral to acid conditions leads to the destruction of the vaterite matrix followed by a quick release of the encapsulated materials. These flexible control mechanisms make this system an interesting candidate for pharmaceutical applications.