Hydrazine induced toxicity causes serious harm to the health of humans. The detection of N 2 H 4 in vitro and in vivo has attracted a great deal of attention, especially in the context of fluorescent probes. Although some fluorescent N 2 H 4 probes have been reported, only a few operate in purely aqueous media and, as a result, require the use of organic cosolvents which hinders their use in analysis of real samples. In addition, most of the current N 2 H 4 probes are either "off−on" or "on−off" types, in which it is difficult to eliminate interference from background fluorescence commonly occurring in in vitro and in vivo systems. Furthermore, some probes are unable to differentiate hydrazine from other organic amines. To address the above problems, we developed a novel oligo(ethylene glycol)-functionalized fluorescent probe for the detection of N 2 H 4 . The probe, which has a donor−π-acceptor (D−π−A)-type structure, is water-soluble, and it can be utilized to selectively detect N 2 H 4 in both colorimetric and ratiometric mode. Furthermore, the probe is able to differentiate hydrazine from other organic amines and can be used to detect hydrazine vapor and for imaging A549 cells and zebrafish.
MicroRNA (miRNA) is a promising biomarker for the diagnosis,
monitoring,
and prognostic evaluation of diseases, especially cancer. The existing
miRNA detection methods usually need external instruments for quantitative
signal output, limiting their practical applications in point-of-care
(POC) settings. Here, we propose a distance-based biosensor through
a responsive hydrogel, in combination with a CRISPR/Cas12a system
and target-triggered strand displacement amplification (SDA) reaction
for visual quantitative and sensitive measurement of miRNA. The target
miRNA is first converted into plenty of double-stranded DNA (dsDNA)
via target-triggered SDA reaction. Then, the dsDNA products trigger
the collateral cleavage activity of CRISPR/Cas12a, leading to the
release of trypsin from magnetic beads (MBs). The released trypsin
can hydrolyze gelatin, and hence the permeability of gelatin-treated
filter paper is increased, resulting in a visible distance signal
on a cotton thread. Using this system, the concentration of the target
miRNA can be quantified visually without any assistance of instruments,
and a detection limit of 6.28 pM is obtained. In addition, the target
miRNA in human serum samples and cell lysates can also be detected
accurately. Owing to the characteristics of simplicity, sensitivity,
specificity, and portability, the proposed biosensor provides a new
tool for miRNA detection and holds great promise in POC applications.
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