Occlusion of polymeric capsules in calcite single crystals for storage of active pharmaceutical ingredients

Developing a new drug storage system is imperative, especially for macromolecules with limited shelf-lives, pharmaceutical cures for unforeseeable epidemics, and drugs with short-lived therapeutic windows. In this work, calcite is proposed as a new system for drug storage. Since it is a single crystal, it is impenetrable by the primary agents of decay (oxygen, humidity and UV radiation). The system explored in this work achieved 20% occlusion in mass, which is 5% higher than the most excellent occlusion reported in the literature. This is the first evidence of a neutral capsule occluded inside of calcite, which breaks with the assumption that charge is a requisite for crystal-additive interactions. Using CLSM and FIB-SEM tomography, three-dimensional models are built of the occluded capsules in crystals. The occlusion patterns observed revolve around the third-order axis of symmetry. Size selectivity of around 1 µm has been calculated, although most of the occluded capsules observed are in the 100-300 nm range. We propose that this system be applied at the manufacturer scale and that the drugs stored in the crystals can later be processed into consumer-ready pharmaceuticals when needed. The pharmaceutical industry can apply this technology to control the spread of infectious diseases or simply profit from price fluctuations on synthetic precursors.