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Fig. 4 Confocal fluorescence microscopy images of MHCC97H cells
incubated with fluorescein loaded MS@polymer nanoparticles
(5 mg mLÀ1) before (A–C) and after (D–F) UV irradiation. (A) and
(D) show the emissions of fluorescein excited at 488 nm; (B) and (E)
show the emissions of Hoechst 33258 excited at 405 nm, which indicate
the cell nucleus; (C) and (F) show the overlay images.
that the hybrid nanoparticles are cell permeable and bio-
compatible so they are suitable for intracellular light-controlled
drug delivery. However, at this stage the dispersion in aqueous
solution of the hybrid nanoparticles in pore-closed state is not
high due to the hydrophobic nature of the polymer shell
(Fig. S8). We hope that modification of the silica surface or
polymer shell with hydrophilic macromolecules such as PEG
would improve this parameter.8
In conclusion, we have developed a novel controlled-release
system that uses mesoporous silica nanoparticles as nano-
containers and polymer as light-responsive valve. Light-
responsive polymer that has a LCST of 14 1C, below 37 1C,
was tethered to the surface of MCM-41 type MS nanoparticles
to lock the loaded molecules within the MS pores. Upon UV
irradiation, the hydrophobic NBAE groups in the polymer
backbone were photolysed into hydrophilic acrylate which led
to an increase in the LCST of the resulting copolymers to
46 1C, now higher than 37 1C. Thus the polymer changed its
phase state at 37 1C and the loaded molecules were released
from the hybrid nanoparticles. The system possesses
advantages such as non-invasive and high spatiotemporal
resolution resulting from the using of light stimulus, as well
as good biocompatibility and ease in functionalization. The
results reported here suggest that it can be applied in stimulus
controlled drug and gene delivery systems for biological
applications.
We thank Yunbao Jiang for suggestions and editing of
English while revising the paper. This work was supported
by the National Natural Science Foundation of China
(20875079 and 20835005), The Planned Science and
Technology Project of Xiamen, China (3502z20080011) and
the Specialized Research Fund for the Doctoral Program of
Higher Education of China (200803840007).
7 X. Jiang, C. Lavender, J. Woodcock and B. Zhao, Macromolecules,
2008, 41, 2632; X. Jiang, S. Jin, Q. Zhong, M. Dadmun and
B. Zhao, Macromolecules, 2009, 42, 8468.
8 Q. He, J. Zhang, J. Shi, Z. Zhu, L. Zhang, W. Bu, L. Guo and
Y. Chen, Biomaterials, 2010, 31, 1085.
c
7372 Chem. Commun., 2010, 46, 7370–7372
This journal is The Royal Society of Chemistry 2010