Hong Zhang,Chuance Cheng,Nalin Dong,Xiaoming Ji,Jiandong Hu
S1 nuclease plays an important role in DNA transcription, recombination and repair. Here, we synthesized a positively charged [email protected] core-shell nanoparticles ((+) [email protected] CSNPs) and used as highly stable and enhanced fluorescence quenching platform for one-step S1 nuclease activity detection. In the sensor, fluorophore labeled DNA was used as signal probe and its fluorescence signal could be effectively quenched based on the electrostatic interaction of it with (+) [email protected] CSNPs. In the presence of S1 nuclease, DNA probe was hydrolyzed into DNA fragments and cannot interact with (+) [email protected] CSNPs, inducing an obvious fluorescence signal increase that was proportional with S1 nuclease concentration in the range of 2.5 × 10 −4 –3.0 × 10 −2 U/mL. The enhanced quenching efficiency of (+) [email protected] CSNPs paved the way for sensitive S1 detection with a detection limit of 6.0 × 10 −5 U/mL. Moreover, the high stability of such nanocomposite can achieve the one-step detection of S1 in complex solution containing salt, protein or other metal ions. In addition, the method also exhibited high selectivity for nuclease detection, making our sensing platform has a potential application value in bioanalysis and clinical diagnosis.
As an important antitumor drug, bleomycin (BLM) is widely used in the treatment of a variety of cancers. In addition, nucleases play a crucial role in DNA replication, recombination and repair which are associated with cancer development. Thus, the development of BLM and nuclease detection methods is of great significance in cancer therapy and related biological mechanism research. Here, a WS 2 nanosheet-based turn-on fluorescent sensing platform for simple, fast and sensitive detection of BLM and nuclease was reported. WS 2 nanosheet exhibits different affinity toward ssDNA with different length and excellent fluorescence quenching ability. A fluorescein (FAM)-labeled long ssDNA could be adsorbed on the surface of WS 2 nanosheet and the fluorescence was therefore quenched. In the presence of BLM·Fe(II) or S1 nuclease (a ssDNA-specific nuclease which was used as a model enzyme), an irreversible scission of long ssDNA was underwent through the BLM-induced oxidation cleavage or S1 nuclease-induced enzymatic hydrolysis. Short FAM-linked oligonucleotide fragments which could not be adsorbed on the nanosheet surface were then produced, resulting in a weak fluorescence quenching after mixing WS 2 nanosheets. Thus, the fluorescence signal was restored. The proposed sensor displays a wide linear range and a high sensitivity with a detection limit of 0.3 nM for BLM and 0.01 U mL −1 for S1 nuclease. It also exhibits a good performance in complex biological samples. This method not only provides a strategy for BLM or S1 nuclease assay but also offers a potential application in biomedical and clinical study.
Herein we propose a rational design to construct peroxidase mimetics in response to S1 nuclease by employing guanine-rich oligonucleotides and Cu2+ ions. The enzymatic activities of DNA–Cu(II) are highly dependent upon the binding stoichiometry between Cu2+ and DNA. In the H2O2-mediated oxidation of 3,3′,5,5′-tetramethylbenzidine, the catalytic activity of Cu2+ can be accelerated approximately 88 times in the presence of AG3(T2AG3)3, whereas it shows slight enhancement in the presence of a mononucleotide (GMP). The coordination of Cu2+ with DNA structures greatly strengthens its ability to generate reactive oxygen species. The most intriguing finding in this study is that DNA–Cu(II) complexes lose their enzymatic activities after the cleavage of DNA scaffolds by S1 nuclease. A colorimetric method was established for selectively evaluating the S1 nuclease activity with a limit of detection of 4.7 × 10−3 U mL−1, only by using label-free oligonucleotides and copper ions without complicated synthesis and apparatus. This facile method can also be applicable for quantitative analysis in biological fluids.
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