Double-layered microparticles with enzyme-triggered release for the targeted delivery of water-soluble bioactive compounds to small intestine

Double-layered microparticles for enzyme-triggered release in the gastrointestinal tract were prepared by spray-chilling a water/oil/water emulsion, which could be a promising candidate for the targeted delivery of water-soluble bioactive compounds. Based on response surface methodology, the optimum conditions for 2nd emulsifier content, concentration ratio of the single emulsion to the coating material, and dispersion fluid temperature were 201.5 μmol, 0.30, and 10.1 °C, respectively. Morphological characterisation using an FE-SEM indicated that double-layered microparticles with diameters of 7–10 μm were spherical and possessed scores of inner droplets. Release profiles generated using in vitro digestion models revealed that the core of double-layered microparticles was gradually released by enzymatic degradation when exposed to the simulated intestinal environment. The accumulative release reached 59.8 ± 0.2% within a residence time of 3 h, whereas they were resistant to gastric release-stimuli, such as extremely low pH and pepsin (below 2.4 ± 0.6%).