Furthermore, by taking advantage of the distinct fluorescence
recovery rates of PPE-(COOK)4/Cu2+ caused by GSH and
GSSG, a new fluorescence turn-on assay for GR activity has
successfully been developed. As the first GR activity assay based
on CPEs, it is highly sensitive and robust as compared to most
fluorescent and spectrophotometric methods. At present, the
assay of GR activity in a continuous and real-time manner on
microfluidic chips is under investigation.
Acknowledgements
Fig. 7 Emission intensity changes of PPE-(COOK)4/Cu2+ (5 mM/5 mM)
caused by various proteins in the presence of GSSG (3 mM) and NADPH
(30 mM). The concentrations of most proteins are 10 mg mLꢂ1 with the
exception of [GR] ¼ 2 mU/mL (ꢃ2.34 mg mLꢂ1).
This work is supported by the National Natural Science Foun-
dation of China (20805042), Natural Science Foundation of
Zhejiang Province (Y4090154), Fundamental Research Funds
for the Central Universities (2009QNA5006), and Innovation
Method Fund of China (2008IM040800).
Given that an effective GR activity assay should be capable of
monitoring the inhibition process, a typical inhibitor 1,3-bis(2-
chloroethyl)-1-nitrosourea (BCNU) has been examined, which is
the most commonly used irreversible GR inhibitor.26 As shown
in Fig. 6, the fluorescence turn-on response was apparently
decreased in the presence of BCNU with varying concentrations,
which demonstrated clearly an efficient restraint of the GR-
catalyzed reduction of GSSG. It should be noted that the
incomplete inhibition of GR in this experiment was actually
because of the fairly poor water solubility of this inhibitor. Thus,
the proposed sensor protocol can certainly be used in screening
potential drugs based on the inhibition of GR, e.g., anticancer or
antimalarial medicines.
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10906 | J. Mater. Chem., 2010, 20, 10901–10907
This journal is ª The Royal Society of Chemistry 2010