Size-Controlled Synthesis of Vaterite Calcium Carbonate by the Mixing Method: Aiming for Nanosized Particles

Extensive use of vaterite for encapsulation and drug delivery requires the means for controlling the size of crystals synthesized via simple mixing of calcium chloride and sodium carbonate. Importantly, to take full advantage of vaterite for nanomedicine, the particle size has to be confined to the nanoscale. The impacts of temperature, salt concentration, and polyol additives are systematically researched with the purpose to achieve nanosized crystals of vaterite in a controlled way. The influence of polyols (ethylene glycol, glycerol, and erythritol) is studied here with respect to their concentration, viscosity of water/polyol mixtures, and number of hydroxyl groups per polyol molecule. Among the investigated polyols, ethylene glycol and glycerol are found to promote the formation of vaterite enabling spherical framboid particles in the size range of 2 mu m to 350 nm. The conditions suitable for synthesis of submicron CaCO3 are chosen to obtain nanosized sacrificial templates (500 +/- 100 nm in diameter) for capsules of dextran sulfate and poly-L-arginine assembled in a layer-by-layer fashion.