Background Copper is a vital trace element that plays a crucial role in various physiological processes due to its ability to exist in multiple oxidation states. Inspired by natural enzymes, researchers have developed copper-based nanozymes that mimic enzyme functions, offering cost-effective and stable alternatives to traditional enzymes. Despite their promising properties, the design and synthesis of these nanozymes can be complex and challenging. To address this issue, this work explores an intuitive approach to construct “soft” nanozymes simply by binding Cu 2+ with its aptamers to form Cu(II)-aptamer complexes. Results Using a screening strategy, we identified a specific aptamer against Cu 2+ , designated P8, that significantly enhanced peroxidase-like activity when complexed with Cu 2+ , demonstrated by a notably smaller K m value. Furthermore, we investigated the effects of various lengths of a “molecular clamp” on the conformational dynamics of the P8 aptamer, which perturbs the encapsulation of Cu 2+ and modulated its peroxidase activity. Our findings indicate that optimizing the molecular clamp to a moderate length ( N d = 20) can further enhance the peroxidase activity of the Cu 2+ -P8 complex. The peroxidase-like soft nanozymes based on copper(II)-aptamer complexes were finally utilized for label-free detection of EDTA. The developed colorimetric sensing method exhibits outstanding detection capabilities for EDTA in Sprite and mineral water samples, achieving an extended dynamic range that accommodates higher concentrations through the incorporation of molecular clamps. Significance and novelty This work highlights a novel and straightforward approach to generate and improve the enzymatic properties of copper-based nanozymes. The strategy to regulate the enzymatic activity effectively addresses the limitations of narrow detection ranges commonly observed in traditional methods.
Xing Qian,Zijing Wang,Zeyu Chen,Salah M. El-Bahy,Dongxiang Li,Lianjie Qin,Chunfang Li,Zeinhom M. El-Bahy,Jikuan Zhao
Copper is essential for human body because it plays an important role in various physiological processes, so the sensitive detection of Cu 2+ ions is a vital topic in human health and environment safe. In this work, green-emitting carbon quantum dots (CQDs) facilely synthesized by a microwave-assisted hydrothermal method were used as fluorescent probes for Cu 2+ detection. The CQDs showed a rapid and sensitive response to Cu 2+ with a color change and brightened fluorescence. The fluorescence enhancement of CQDs reaches 4.51-fold by 5 μM Cu 2+ as a typical “turn-on” strategy. A good linear relation of the fluorescence enhancement by Cu 2+ appears in a range of 0.1–1 μM Cu 2+ with a limit of detection (LOD) of 2.46 nM. Then, the enhanced fluorescence of Cu 2+ -CQDs could be rapidly decreased by EDTA via a quenching response (“turn-off”). A linear range of the fluorescence decrease and EDTA concentration is 1–10 μM with a LOD of 0.19 μM. The interference experiments for the detections of both Cu 2+ and EDTA show a high selectivity. The practical detections of both Cu 2+ and EDTA in actual water samples and spiked samples demonstrated good reproducibility and effective recovery rates. In addition, the Cu 2+ -CQDs even had a slow “turn-off” response to histidine over 20 natural amino acids. Overall, the CQDs-based “turn-on-off” detection methods with high sensitivity and selectivity in this work can be considered a promising new choice for the fluorescence analysis of Cu 2+ and EDTA.
Mingxi Yang,Qiuling Tang,Yang Meng,Junjun Liu,Tanglue Feng,Xiaohuan Zhao,Shoujun Zhu,Weixian Yu,Bai Yang
Zn2+-passivated carbon dots (named Z-CDs) were synthesized from zinc gluconate for the first time through a one-step pyrolysis treatment. The mechanism of Zn2+-enhanced fluorescence was carefully investigated, and a new strategy to passivate the surfaces of CDs by Zn2+ was proposed. Inspired by the complexation reaction between Zn2+ and ethylenediaminetetraacetic acid (EDTA), a reversible “off–on” fluorescent nanosensor for the detection of EDTA and Zn2+ was constructed based on the depassivation and repassivation of Z-CDs, with a limit of detection as low as 3.2 × 10–7 M and 5.1 × 10–7 M, respectively. The proposed Z-CD-based nanosensor had been further utilized for EDTA and Zn2+ monitoring in tap water with excellent recovery. To the best of our knowledge, this was the first report of a fluorescence-based sensor of EDTA and a turn-on sensor of Zn2+ based on CDs with reversible detection capability. Also, benefiting from the low toxicity of zinc, Z-CDs were applied for multicolor bioimaging and in vitro detection in cells.
危险品化学品经营许可证（带存储）