An allosteric switch-based hairpin for label-free chemiluminescence detection of ribonuclease H activity and inhibitors

Electrogenerated chemiluminescence resonance energy transfer between luminol and MnO2 nanosheets decorated with Cu2O nanoparticles for sensitive detection of RNase H

In the present work, a novel approach was developed for the preparation of Cu₂O nanoparticle decorated MnO₂ nanosheets (Cu₂O@MnO₂). Uniformly dispersed Cu₂O nanocrystals were produced on the surface of MnO₂ nanosheets by in situ reduction under refluxing conditions. The unique structure of the used MnO₂ nanosheet support played a vital role in the preparation of such Cu₂O@MnO₂ nanocomposites. The electrogenerated chemiluminescence (ECL) resonance energy transfer can occur between the luminol/H₂O₂ system and Cu₂O@MnO₂ nanocomposites, resulting in a decrease of the ECL intensity, which can be used to fabricate an ECL sensor. Cu₂O@MnO₂ nanocomposite modified heterologous DNA/RNA duplexes were modified on the GCE to construct an ECL-RET system, leading to the decrease of ECL intensity. As a highly conserved damage repair protein, RNase H can specifically hydrolyze RNA in DNA/RNA strands to release Cu₂O@MnO₂ nanocomposites and recover the ECL signal. As a result, an "off-on" mode ECL sensor for sensitive RNase H assay was fabricated. Under the optimal conditions, the detection limit of RNase H is 0.0005 U mL^-1, which is superior to other approaches. The proposed method provides a universal platform for monitoring RNase H, and exhibits great potential in bioanalysis.

Ruthenium(II) Complex-Based G-quadruplex DNA Selective Luminescent 'Light-up' Probe for RNase H Activity Detection

A bis-heteroleptic ruthenium(II) complex, 1[PF₆ ]₂ of benzothiazole amide substituted 2,2'-bipyridine ligand (bmbbipy) has been synthesized for the selective detection of G-quadruplex (GQ) DNA and luminescence-assay-based RNase H activity monitoring. Compound 1[PF₆ ]₂ exhibited aggregation-caused quenching (ACQ) in water. Aggregate formation was supported by DLS, UV-vis, and ¹ H NMR spectroscopy results, and the morphology of aggregated particles was witnessed by SEM and TEM. 1[PF₆ ]₂ acted as an efficient GQ DNA-selective luminescent light-up probe over single-stranded and double-stranded DNA. The competency of 1[PF₆ ]₂ for selective GQ structure detection was established by PL and CD spectroscopy. For 1[PF₆ ]₂ , the PL light-up is exclusively due to the rigidification of the benzothiazole amide side arm in the presence of GQ-DNA. The interaction between the probe and GQ-DNA was analyzed by molecular docking analysis. The GQ structure detection capability of 1[PF₆ ]₂ was further applied in the luminescent 'off-on' RNase H activity detection. The assay utilized an RNA:DNA hybrid, obtained from 22AG2-RNA and 22AG2-DNA sequences. RNase H solely hydrolyzed the RNA of the RNA:DNA duplex and released G-rich 22AG2-DNA, which was detected via the PL enhancement of 1[PF₆ ]₂ . The selectivity of RNase H activity detection over various other restriction enzymes was also demonstrated.

Enzyme-triggered DNA nanomimosa: A ratiometric nanoprobe for RNase H activity sensing in living cells

Since ribonuclease H (RNase H) exhibits its importance in a variety of cellular processes. It is necessary to establish strategy for RNase H detection. In this work, we are enlightened by mimosa, a natural plant which can fold in response to stimuli, to construct a DNA tetrahedron-based nanoprobe, termed DNA nanomimosa, to sensing RNase H activity based on fluorescent resonance energy transfer (FRET). The DNA nanomimosa was self-assembled from four DNA chains and one RNA chain. One of the four DNA chains contains a FRET-paired fluorophores-labeled hairpin DNA structures which is unfolded by the RNA chain through hybridization. Without RNase H, the RNA chain separate the two FRET-paired fluorophores in hairpin DNA structure, giving a feeble FRET signal. However, the presence of RNase H can selectively digest the RNA strand in RNA/unfolded-hairpin DNA section, resulting in the hairpin DNA configuration changed from "unfolded" state to "folded" state and further turn on the FRET signal. The DNA nanomimosa can be applied to achieve the determination of RNase H activity by recording the emission intensity of donor and acceptor fluorophores. This strategy shows a low detection limit by 0.017 U/mL, good specificity, and distinct advantages like the self-delivery ability, good biocompatibility, and the capacity to minimize the effects of fluctuations. This design provides a potential application in ribonuclease research and could be expanded for other biomedical research and clinical diagnostics.