DNA-templated copper nanocluster: A robust and universal fluorescence switch for bleomycin assay

One-step strand displacement-mediated nucleic acids signal-amplified analytical strategy based on superparamagnetism-functionalized DNA arrays

DNA nanostructure, as polymeric material with remarkable molecular recognition property, has been widely used in bioassay. However, it still faces some challenges to overcome complexity of signal-amplified strategies and to realize efficient separation of reaction products. Herein, we present an innovative signal-amplified approach by integrating the toehold-mediated strand displacement reaction with DNA tile self-assembly technology to construct superparamagnetism-functionalized DNA polymeric materials, establishing a new signal-amplified analytical strategy for nucleic acids. This strategy enables highly sensitive, rapid, and efficient nucleic acid detection, making it a promising candidate for point-of-care testing (POCT). The analytical performance of this strategy was validated using target DNA (tDNA) and PIWI-interacting RNA-36026 (piRNA-36026), achieving limits of detection (LOD) of 2.4 × 10-10 M and 2.7 × 10-10 M. Moreover, it successfully detected single-base mutations and demonstrated stability over seven days. Comparative experiments confirmed the superior signal-amplified efficiency of DNA arrays. Recovery experiments yielded recoveries of 88.53 %-101.89 % for tDNA and 87.58 %-108.61 % for piRNA-36026. Ultimately, the feasibility of this strategy for real-world applications was validated through detecting piRNA-36026 in cell lysates. In conclusion, this work introduces an innovative and efficient signal-amplified method, while expanding the application prospects of multifunctional DNA polymeric materials in biomedical diagnostics.

Novel Primer Design for Significantly Reducing Fluorescent Interferences in the Synthesis of DNA-Templated Copper Nanoclusters for the Detection of the HLA-B*5801 Gene

The optimal sequence for synthesizing copper nanoclusters is a promising research area. Initially, random dsDNA sequences yielded low fluorescence intensity, which constrained visual detection under UV light. Poly-AT dsDNA sequences later produced visible fluorescence, but it caused significant interference in negative samples when combined with gene amplification techniques. This interference occurs because the single-stranded poly-AT primer can self-anneal into a double-stranded AT sequence, efficiently synthesizing copper nanoclusters. To mitigate this, we designed a poly-AAT sequence at the primer's 5' end, creating a single base pair mismatch every three nucleotides during self-annealing. This adjustment reduced synthesis efficiency of copper nanoclusters in negative samples, improving the visual distinction between negative and positive results. We applied this method to identify the HLA-B*5801 gene, thereby demonstrating its efficacy even within a GC-rich region of human genomic DNA. Our method showed 100% agreement with a commercial qPCR kit, with results distinguishable under UV light. We conclude that the poly-AAT sequence is more suitable for integrating copper nanoclusters synthesis with nucleic acid amplification detection techniques, with potential applications in microelectronics, biosensing, and catalysis.

A facile synthesis of water-soluble copper nanoclusters as label-free fluorescent probes for rapid, selective and sensitive determination of alizarin red

Copper nanoclusters (FA@CuNCs) emitting blue fluorescence were successfully developed via a one-pot technique. In this method, the copper chloride, folic acid and hydrazine hydrate were applied as a precursor, protective agent and reducing agent, respectively. The absorption, fluorescence excitation and emission spectra of FA@CuNCs were carried out by using ultraviolet-visible and fluorescence spectrometry, respectively. The morphology, particle size, functional groups, oxidation states of elements of FA@CuNCs were discussed via using transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The stability of FA@CuNCs was studied under various conditions, such as storage time at 25 ℃, ultraviolet radiation time, sodium chloride solutione and pH. The FA@CuNCs displayed blue fluorescence under the excitation wavelength of 361 nm, and the fluorescence quantum yield was 7.45 %. As a result of the inner filter effect, the alizarin red could significantly weaken the blue fluorescence of FA@CuNCs. Thus, the as-prepared FA@CuNCs could be utilized as fluorescence nanosensors for the trace determination of alizarin red. This platform suggested an excellent linear range for alizarin red varying from 0.5 to 200 μM with a fitting coefficient of 0.9955. The detection limit was calculated to be 0.064 μM in the light of the 3b/k (b and k refer to the standard deviation and slope of fitted curve, respectively). Furthermore, the as-developed FA@CuNCs could be used to detect the alizarin red in real samples and for the sensing of temperature.

An ATMND/SGI based three-way junction ratiometric fluorescent probe for rapid and sensitive detection of bleomycin

In this work, we developed a rapid and sensitive label-free ratiometric fluorescent (FL) probe for the detection of bleomycin (BLM). The probe consists of a DNA sequence (D6) and two fluorophore groups, 2-amino-5,6,7-trimethyl-1,8-naphthalene (ATMND) and SYBR Green I (SGI). The D6 sequence could be folded into a three-way junction structure containing a C-C mismatch position in the junction pocket. The unique "Y" structure not only could entrap ATMND in the mismatch pocket with high affinity, leading to FL quenching at 408 nm, but also embed SGI in the grooves of the double-stranded portion, resulting in FL enhancement at 530 nm. In the presence of BLM-Fe(II), the "Y" structure of D6 was destroyed due to the specific cleavage of the BLM recognition site, the 5'-GT-3' site in D6. This caused the release of ATMND and SGI and thus the ratiometric signal change of FL enhancement by ATMND and FL quenching by SGI. Under optimal conditions, the ratiometric probe exhibited a linear correlation between the intensity ratio of F408/F530 and the concentration of BLM in the range of 0.5-1000 nM, with a detection limit of 0.2 nM. In addition, the probe was applied to detect BLM in human serum samples with satisfactory results, indicating its good clinical application potential.