Fabrication of Multicore Milli- and Microcapsules for Controlling Hydrophobic Drugs Release Using a Facile Approach

Herein, we designed two simple devices by exploiting the advantages of coaxial shear microfluidic and coextrusion minifluidic devices to generate multicore milli- and microcapsules for encapsulating hydrophobic drugs. The number of cores could be precisely controlled by tailoring the flow rate or number of inner tubes. Similarly, the shell thickness and core size could be controlled accurately. In this study, the UV stability of a-tocopherol (model drug) capsules was investigated. The result shows that the oxidation rate of alpha-tocopherol in millimeter capsules was much slower than that in free or micrometer capsules, which was related to the shell thickness of the capsules. Moreover, size- and core-number-dependent release was observed in vitro, where the millimeter capsules exhibited dramatic discrepancies of release rate compared with micrometer capsules. The release mechanism of capsules was primarily illustrated to include burst release, swelling and erosion release, and diffusion release, which was consistent with the phenomenon observed online using a high-speed camera.