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Calcium ion assisted fluorescence determination of microRNA-167 using carbon dotsa??labeled probe DNA and polydopamine-coated Fe3O4 nanoparticles
摘要： A selective and sensitive fluorescence biosensor is described for determination of microRNA-167 using fluorescent resonant energy transfer (FRET) strategy. The FRET system comprises carbon dots (CDs, donor) labeled with probe DNA (pDNA) and polydopamine (PDA)-coated Fe3O4 nanoparticles (Fe3O4@PDA NPs, acceptor). The CDs-pDNA can be absorbed onto the surface of Fe3O4@PDA NPs because of the strong π interaction between pDNA and PDA. With the enhanced adsorption ability of Fe3O4@PDA NPs by Ca2+, the fluorescence intensity of CDs at 445 nm (excitation at 360 nm) is quenched. In presence of microRNA-167, the hybridized complex of CDs-pDNA-microRNA-167 will be released from the surface of Fe3O4@PDA NPs due to the weak π interaction of the complex and PDA. This results in the fluorescence recovery of CDs. By application of twice-magnetic separation, the biosensor shows a wide linear range of 0.5–100 nM to microRNA-167 with a 76 pM detection limit. The method was applied to the determination of microRNA-167 in samples of total microRNA extractions from A. thaliana seedlings, and the recoveries ranged from 96.4 to 98.3%.
关键词： Fluorescent resonant energy transfer,Twice-magnetic separation,MicroRNA extractions,Hybridized complex,π interaction,Fluorescence biosensor
更新于2025-09-19 17:13:59
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Label-free optical biosensor for target detection based on simulation-assisted catalyzed hairpin assembly
摘要： Taking the advantage of the high selectivity of aptamers and enzyme-free catalyzed hairpin assembly (CHA) amplification strategy, we herein describe a label-free and enzyme-free sensitive fluorescent and colorimetric strategy for amplified thrombin detection in this paper. To support both biological inquiry and technological innovation, thermodynamic models are introduced to predict the minimum energy secondary structure of interacting nucleic acid strands and calculate the partition function and equilibrium concentration for complexes in our system. Then, the thermodynamics properties of interacting DNA strands and the reactions of toehold strand displacement-driven assembly have been simulated, validating the feasibility of the theory and optimizing the follow-up lab tests. Following that, our strategy for thrombin detection is proved to be feasible and effective in biological experiments.
关键词： Computation and simulation,G-quadruplex,catalyzed hairpin assembly,fluorescence biosensor,DNA strand displacement
更新于2025-09-10 09:29:36
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Carbon-Dot-Based Ratiometric Fluorescence Glucose Biosensor
摘要： A ratiometric fluorescence glucose biosensor based on carbon dots (CDs) and rhodamine 6G (Rh6G) was developed both as an aqueous solution and as a crosslinked poly(acrylic acid) solid-state film. A ratiometric fluorescence color change was realized by fluorescence quenching due to the bienzymatic reaction of glucose oxidase (GOx) and horseradish peroxidase (HRP) with glucose. When excited at 360 nm, the blue fluorescence emission of the CDs, prepared by a solvothermal method with citric acid and ethylene diamine, was quenched by the bienzymatic reaction with glucose, whereas the fluorescence of Rh6G was inert to glucose. Thus, a ratiometric fluorescence color change from blue to green was observed as the glucose concentration increased. The optimized CD/Rh6G/GOx/HRP aqueous solution showed a linear range of 0.1–500 μM with a limit of detection (LOD) of 0.04 μM, good selectivity for glucose over the major ingredients in human blood and could be used with human blood serum. A stable solid-state biosensor film was fabricated by immobilization of CD/Rh6G/GOx/HRP in the hydrogel film prepared by ultraviolet curing of a mixture of acrylic acid and diacrylated poly(ethylene glycol) (70:30, w/w). Compared to the CD/Rh6G/GOx/HRP aqueous solution, the hydrogel film showed a similar ratiometric fluorescence color change, sensitivity (linear range of 0.5–500 μM with an LOD of 0.08 μM), and selectivity. Further, the solid-state glucose biosensor film was inherently stable and could be used whenever needed, overcoming the instability of the aqueous solution (owing to aggregation, enzyme denaturation, etc.). These ratiometric biosensors increase the ability to detect glucose using the naked eye compared to simple turn-on or turn-off modes. Thus, this approach expands the potential applications of CDs in biosensors to provide more convenient and practical detection methods.
关键词： glucose,ratiometric,carbon dot,fluorescence,biosensor,enzyme
更新于2025-09-09 09:28:46