Abstract
The development of a smart microencapsulation system programmed to actively respond to environmental pH change has long been recognized a key technology in pharmaceutical and food sciences. To this end, we developed hollow microparticles (MPs) with self-controlled macropores that respond to environmental pH change, using an Oil-in-Water emulsion technique, for oral drug delivery. We observed that freeze-drying of MPs induced closure of macropores. The closing/opening behavior of macropores was confirmed by exposing MPs encapsulating different ingredients (sulforhodamine b, fluorescent nanoparticles, and lactase) to simulated gastrointestinal (GI) fluids. MPs maintained their intact, closed pore structure in gastric pH, and subsequent exposure to intestinal pH resulted in pore opening and ingredients release. Further, MPs displayed higher protection (>15 times) than commercial lactase formulation, indicating the protective ability of the system against harsh GI conditions. This study showed development of a hybrid MP system combining the advantages of solid particles and hollow capsules, exhibiting easy solvent-free loading mechanism and smart protection/release of encapsulates through controllable macropores. Ultimately, our MPs system strives to usher a new research area in smart drug delivery systems and advance the current oral drug delivery technology by solving major challenges in targeted delivery of pH-sensitive therapeutics.
Highlights
To date, microemulsion has been widely employed to fabricate microencapsulation systems for drug delivery[29,30,31,32]
We report a smart microencapsulation system with self-controlled macropores that respond to environmental pH change
After stirring at R.T. for 10 min, the mixture was sonicated for an additional 30 min. This is a simple process to fabricate hollow MPs with a macropore, and the overall process is less time consuming, which does not require long incubation in vacuum conditions like the method used for polystyrene MPs47. This process showed excellent repeatability of forming pored MPs even though it employs co-solvent system, which was hard to achieve from previously reported method due to the difficulty in controlling solvent evaporation
Summary
Microemulsion has been widely employed to fabricate microencapsulation systems for drug delivery (i.e., almost exclusively for solid particles and hollow capsules)[29,30,31,32]. The goal of this research is to develop an innovative oral drug delivery system which can meet multiple demands of convenient encapsulation, protection against MP fabrication and gastrointestinal (GI) environments, targeted delivery, and efficient release of functional ingredients simultaneously. For this purpose, we report a smart microencapsulation system with self-controlled macropores that respond to environmental pH change (see Fig. S1, Supporting Information). Lactase, as a model pH-sensitive functional ingredient, was encapsulated into MPs, and its functional activity was assayed using ortho-nitrophenyl-β-galactoside (ONPG) to confirm the preservation of enzymes in the simulated gastric environment via closed pored MP formulation, and to ensure release of the enzyme in the simulated intestine environment through pore opening
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