Composite cyclodextrin–calcium carbonate porous microparticles and modified multilayer capsules: novel carriers for encapsulation of hydrophobic drugs

Abstract

Novel composite cyclodextrin (CD)–CaCO₃ spherical porous microparticles have been synthesized through Ca²⁺–CD complex formation, which influences the crystal growth of CaCO₃. The CDs are entrapped and distributed uniformly in the matrix of CaCO₃ microparticles during crystallization. The hydrophobic fluorescent molecules coumarin and Nile red (NR) are efficiently encapsulated into these composite CD–CaCO₃ porous particles through supramolecular inclusion complexation between entrapped CDs and hydrophobic molecules. Thermogravimetric (TGA) and infrared spectroscopy (IR) analysis of composite CD–CaCO₃ particles reveals the presence of large CDs and their strong interaction with calcium carbonate nanoparticles. The resulting composite CD–CaCO₃ microparticles are utilized as sacrificial templates for preparation of CD-modified layer-by-layer (LbL) capsules. After dissolution of the carbonate core, CDs are retained in the interior of the capsules in a network fashion and assist in the encapsulation of hydrophobic molecules. The efficient encapsulation of the hydrophobic fluorescent dye, coumarin, was successfully demonstrated using CD-modified capsules. In vitro release of the encapsulated coumarin from the CD–CaCO₃ and CD-modified capsules has been demonstrated.