This work was supported by the U.S. National Institutes of
Health (GM067201). YNT acknowledges an A*STAR NSS
scholarship.
Notes and references
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Fig. 4 Images of esterase sensing in HeLa cells. (a–d) True color
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Compared to traditional fluorophore-based sensors, our new
ODF-based fluorescence sensor design for esterases/lipases has
several advantages. We used ODF as the fluorophore of choice,
which confers good aqueous solubility due to the negatively
charged DNA backbone, enhanced quenching characteristics,
and ease of synthesis on an automated DNA synthesizer. Our
design provides a modular structure whereby the ODF fluoro-
phore could be easily constructed with multiple sequences27 to
give other emission colors in the sensor without the need to
modify conjugation chemistries.
Also unlike previous sensors in which the enzymatic activity
is dependent on the structure of the fluorophore, the current
modular design allows more freedom of substrate selection.
Indeed, our results have already shown that different enzymes
have different preferences for substrates. By changing only the
substrate moiety, we may potentially find specific substrates
for specific enzymes of interest. This can greatly facilitate
substrate and enzyme screening in drug discovery and bio-
logical studies. In addition, quenching efficiency may well be
improved by selecting a more efficient quencher,32,33 which can
easily be varied without altering the remainder of the structure.
The current proof-of-principle suggests that the favorable
photophysical properties of ODFs might be harnessed to design
sensors in a variety of colors, all excited at a single wavelength,
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ꢁc
This journal is The Royal Society of Chemistry 2010
Chem. Commun., 2010, 46, 1221–1223 | 1223