β-Glucosidase
is associated with many diseases, so it is
important to be able to accurately determine β-glucosidase activity.
Here, we describe a turn-on fluorescence method for sensitively determining
β-glucosidase activity. The method involves the formation of
water-soluble fluorescent polymer nanoparticles. β-Glucosidase
initially hydrolyzes the β-arbutin substrate to release hydroquinone
(1,4-dihydroxybenzene). The hydroquinone then forms cross-links between
branched polyethylenimine molecules to give fluorescent water-soluble
polymer nanoparticles. The polymer nanoparticles were found to fluoresce
with excitation and emission peaks at 373 and 510 nm, respectively,
and the fluorescence intensity was related to the β-glucosidase
activity. The fluorescence intensity could therefore be used to determine
the β-glucosidase activity. The lowest β-glucosidase activity
that could be determined was 0.4 U L–1, and the
dynamic linear range was 1.0–36.0 U L–1.
The method was very selective for β-glucosidase activity and
was not sensitive to other proteins. The method was successfully used
to determine β-glucosidase in spiked samples containing human
serum albumin at a concentration of 0.5%, and the recoveries were
95.2%–104.5%.
Nonconjugated polymer dots (NPDs) were successfully used as fluorescent probes to selectively and sensitively detect picric acid (PA). The NPDs were prepared from polyethylenimine and 1,4phthalaldehyde under mild conditions and had excitation and emission maxima of 351 and 474 nm, respectively. Fluorescence of the NPDs was efficiently quenched by PA through the inner filter effect because of the overlapping PA absorption band and NPD excitation spectrum. The NPDs allowed PA to be determined with a high degree of sensitivity. The linear range was 0-140 μM and the detection limit was 0.5 μM. The work involved developing a novel method for synthesizing NPDs and a promising platform for determining PA in environmental media.
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