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Fig. 3 Release of IBU in vitro from IBU@HMS@b-CD@PPP under
different light irradiation at 37 1C (a) and under the conversion of UV
and Vis (b).
80 wt% of IBU was released within 100 h under UV irradiation
while less than 10 wt% of IBU was released under Vis-radiation.
This result strongly demonstrated that HMS@b-CD@PPP
would only release drugs by the stimulation of UV light.
To further investigate the reversibility of this ‘‘gate-keeper’’
system, an IBU@HMS@b-CD@PPP sample solution was
treated with alternating UV and Vis irradiation every 6 h.
The concentration of the released drug was analyzed by UV-Vis
spectroscopy every 2 h and the results are summarized in Fig. 3b.
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once the light irradiation switched from UV to Vis. This results
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In summary, we have obtained a reversible polymer ‘‘gate-
keeper’’ system based on light-triggered binding and unbinding
between Azo and b-CD-modified HMS. The UV light could
transform the isomerism of the Azo groups from trans to cis
conformation, which result in detachment of PPP from b-CD
modified HMS, triggering the drug release. Most importantly,
this drug delivery also could stop releasing by irradiation with
Vis light. This strategy is expected to solve the problem of
premature drug release in normal MSN based drug delivery and
‘‘secondary’’ side effects caused by the residual drug in the
irreversible ‘‘gate-keeper’’ systems.
We acknowledge that funding for this work came from National
Natural Science Foundation of China (20902065, 21076134),
Supporting Project for Science and Technology of Jiangsu Province
(Industry) (BE2011074), a project funded by the Priority Academic
Program Development of Jiangsu Higher Education Institutions
(PAPD) and the Innovative Research Team of Advanced
Chemical and Biological Materials, Suzhou University. We would
like to thank Prof. Qinghua Xu from the National University of
Singapore for technical revision of the manuscript.
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10012 Chem. Commun., 2012, 48, 10010–10012
This journal is The Royal Society of Chemistry 2012