(618e) Microfluidic Preparation of Multicompartment Microcapsules for Co-Encapsulation and Controlled Release of Multiple Components

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^[1], controlled
release of various substances^[2] and confined microreaction of chemicals^[3],
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^[6], 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.

References

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.