Microfluidic fabrication of hollow protein microcapsules for rate-controlled release

Droplet-based microfluidics is an emerging technique that is capable of producing sophisticated supramolecular microcapsules in one step. However, food materials, due to their physical and chemical complexity, have limited success with microfluidic processes. The objectives of this work were to produce food-grade protein microcapsules in a microfluidic system and to control their structural properties by adjusting the formulation and flow rates. In this study, a T-junction microfluidic chip was used to create an interface for zein to self-assemble, and therefore form microcapsules with tunable particle sizes, pore distributions, and permeabilities. Our SEM and CLSM results show that the particle size and number of pores increased with the flow rate of the dispersing phase, while the pore size decreased with the flow rate of the dispersing phase. In order to quantify the release profiles, the release half-life (t(50)) was used as an indicator for the particle permeability. A wide range of t(50), from 3 to 62 minutes, was achieved by changing the zein concentration and flow rate of the dispersing phase. Using Rhodamine B as an encapsulant, the release rate was positively correlated with the zein concentration and flow rate of the dispersing phase. Finally, response surface analysis of the formulation and flow rate was applied to aid the design of a carrier with a desirable release rate.