A novel microfluidic paper-based analytic device (μPAD) biosensor is developed for sensitive and visualized detection of glucose. This biosensor is easily fabricated using the wax printing technique, with a hybrid nanocomplex composed of dual enzymes glucose oxidase (GOx) and horseradish peroxidase (HRP) and Cu(PO) inorganic nanocrystals incorporated in the detection zones. The hybrid nanocomplex is found to exhibit a flower-like structure, which allows co-immobilization of these two enzymes in a biocompatible environment. These nanoflowers not only preserve the activity and enhance the stability of the enzymes, but also facilitate the transport of the substrates between the two enzymes. The biosensor is demonstrated to enable rapid and sensitive quantification of glucose in the concentration range of 0.1-10 mM with a limit of detection (LOD) of 25 μM. It is also shown to be applicable to colorimetric quantitative detection of glucose in human serum and whole blood samples, implying its potential for clinical applications.
The efficient detection and in situ monitoring of telomerase activity is of great importance for cancer diagnosis and biomedical research. Here we report for the first time that the development of a novel multivalent self-assembled DNA polymer, constructed through telomerase primer sequence (I TS ) triggered hybridization chain assembly using two functional hairpin probes (tumor-trageting aptamer modified H1 and signal probe modified H2), for sensitive detection and imaging of telomerase activity in living cells. After internalizing into the tumor cells by multivalent aptamer targeting, the I TS on DNA polymers can be elongated by intracellular telomerase to generate telomere repeat sequences that are complementary with the signal probe, which can proceed along the DNA polymers, and gradually light up the whole DNA polymers, leading to an enhanced fluorescence signal directly correlated with the activity of telomerase. Our results demonstrated that the developed DNA polymer show excellent performance for specifically detecting telomerase activity in cancer cells, dynamically monitoring the activity change of telomerase in response to telomerase-based drugs, and efficiently distinguishing cancer cells from normal cells. The proposed strategy may afford a valuable tool for the monitoring of telomerase activity in living cells and have great implications for biological and diagnostic applications.
DNA molecular probes have emerged as a powerful tool for RNA imaging. Hurdles in cell-specific delivery and other issues such as insufficient stability, limited sensitivity, or slow reaction kinetics, however, hinder the further application of DNA molecular probes in vivo. Herein, we report an aptamer-tethered DNA polymer for cell-specific transportation and amplified imaging of RNA in vivo via a DNA cascade reaction. DNA polymers are constructed through an initiator-triggered hybridization chain reaction using two functional DNA monomers. The prepared DNA polymers show low cytotoxicity and good stability against nuclease degradation and enable cell-specific transportation of DNA circuits via aptamer−receptor binding. Moreover, assembling the reactants of hairpins C1 and C2 on the DNA polymers accelerates the response kinetics and improves the sensitivity of the cascade reaction. We also show that the DNA polymers enable efficient imaging of microRNA-21 in live cells and in vivo via intravenous injection. The DNA polymers provide a valuable platform for targeted and amplified RNA imaging in vivo, which holds great implications for early clinical diagnosis and therapy.
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