Microfluidic Preparation of Multicompartment Microcapsules for Co-encapsulation and Controlled Release of Multiple Components
Wei Wang, Rui Xie, Xiao-Jie Ju, Tao Luo, Li Liu, Liang-Yin Chu*
School of Chemical Engineering, Sichuan University, Chengdu, China, 610065
Microcapsules are widely used as encapsulation systems for protection of active species, controlled release of various substances and confined microreaction of chemicals, etc. However, most of these microcapsules can only encapsulate one content within the same structure. How to co-encapsulate multiple incompatible or functional substances in one single microcapsule, especially with precise control over the encapsulation level of each substance, is still a major challenge[4.5]. Our previously reported monodisperse multicomponent multiple emulsions, with co-encapsulated different droplets in the same inner structure, offer novel and diverse templates to create microcapsules with different compartments for co-encapsulation of multiple incompatible actives or functional components. The precise and individuall control over the number, ratio and size of different inner droplets enable the optimization of the encapsulation of each active or functional component.
Here we present the microfluidic preparation of thermo-responsive multicompartment microcapsules for co-encapsulation and controlled release of different lipophilic components with multicomponent-double-emulsions as templates. Each of the microcapsule comprises different oil cores and a single thermo-responsive shell composed of poly(N-isopropylacrylamide) (PNIPAM). The different oil cores can be used as separate compartments for encapsulation of distinct lipophilic components. The precise manipulation of different oil cores afforded by our microfluidic device enables the fabrication of microcapsules with select number of each core, for optimizing the encapsulation of different lipophilic components. Because of the shell shrinking during heating process due to the thermo-responsive PNIPAM network, different lipophilic components co-encapsulated in the microcapsule can be simultaneously released via an external thermal trigger, as shown in Fig.1. The thermo-responsive multicompartment microcapsule provides an efficient system for co-encapsulation and controlled release of multiple lipophilic components. The thermo-responsive multicompartment microcapsules can be converted into other stimuli-responsive ones such as pH-responsive, molecular-recognizable, and glucose- responsive ones, by simply changing the shell materials. The microfluidic preparation approach presented here shows exciting potential in the design and fabrication of functional multicompartment microcapsules for co-encapsulation techniques.
Fig 1. Temperature-controlled release of the co-encapsulated lipophilic substances from the thermo-responsive multicompartment microcapsule. (a) Dark-field microscope image of multicompartment microcapsule co-encapsulated with one transparent oil core and two red oil cores. (b)-(h) The temperature-controlled release of different oil cores from the microcapsule when temperature is increased from 20 oC to 60 oC. With increase in temperature, the thermo-responsive PNIPAM shell of the microcapsule shrinks dramatically. Since the oil cores are incompressible but the internal pressure in oil cores keep increasing due to the shell shrinkage, the PNIPAM shell finally ruptures because of the limited mechanical strength, which results in burst releasing of the oil cores. Scale bar is 100 µm.
1 R. De Rose, A. N. Zelikin, A. P. R. Johnston, A. Sexton, S. F. Chong, C. Cortez, W. Mulholland, F. Caruso, S. J. Kent, Adv. Mater., 2008, 20, 4698.
2 L. Y. Chu, T. Yamaguchi, S. Nakao, Adv. Mater., 2002, 14, 386.
3 O. Kreft, M. Prevot, H. Möhwald, G. B. Sukhorukov, Angew. Chem. Int. Ed., 2007, 46, 5605.
4 H. Chen, Y. Zhao, Y. Song, L. Jiang, J. Am. Chem. Soc., 2008, 130, 7800.
5 B. J. Sun, H. C. Shum, C. Holtze, D. A. Weitz, ACS Appl. Mater. Interfaces, 2010, 2, 3411.
6 W. Wang, R. Xie, X. J. Ju, T. Luo, L. Liu, D. A. Weitz, L. Y. Chu, Lab Chip, 2011, 11: 1587.