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In this work, a novel DNA nanostructure with a shorter assembly time and larger loading capacity was constructed using amphiphilic DNA–alkane group (Spacer C12)10 conjugates encapsulating plentiful fat-soluble fluorescent dyes into the hydrophobic core to form the DNA micelles, which could be rapidly self-disassembled via target induced hydrophilic–hydrophobic regulation to release fluorescent dyes from micelles to the organic phase, realizing the fast and sensitive detection of microRNA. [ABSTRACT FROM AUTHOR]

A kind of organic microcrystal, 9,10-diphenylanthracene microcrystals (DPA MCs), was developed as a novel electrochemiluminescence (ECL) coreactant accelerator to efficiently catalyze dissolved O2 for more reactive oxygen species (ROSs) generation, achieving intense ECL for a H2O2-free luminol system. Moreover, based on this ternary ECL system, a signal "off–on" ECL biosensor for microRNA-21 (miRNA-21) detection was constructed combining a sensitive target recycling amplification strategy and an enzyme-mediated recycling strand displacement reaction (RSDR). [ABSTRACT FROM AUTHOR]

Perylene and its derivatives, as classical organic polycyclic aromatic hydrocarbon (PAH) ECL materials, have attracted extensive attention due to their excellent photoelectric activity and good structural controllability. As is well-known, the molecular structure of perylene is composed of five coplanar aromatic rings. There are intense π–π stacking interactions between perylene molecules, which lead to their aggregation and poor solubility in aqueous media. Unfortunately, this aggregation can weaken or even quench the emission intensity of perylene owing to the aggregation-caused quenching (ACQ) effect, finally limiting the analytical application of perylene in biological detection. In this work, perylene composite microcrystals (ETTA@Pe MCs) doped with non-planar molecular tetrakis(4-aminophenyl)ethene were synthesized in the aqueous phase by a surfactant-assisted self-assembly method. During this process, the intense π–π stacking interactions between perylene monomers were suppressed by doping. As a result, the ETTA@Pe MCs exhibited a significantly enhanced ECL signal as compared to that of perylene microcrystals (Pe MCs) in the presence of S2O82− as a co-reactant. Moreover, the ETTA@Pe MCs were utilized as a novel electrochemiluminescent (ECL) luminophores to fabricate a sensitive ECL biosensor for the quantitative analysis of dopamine (DA), which displayed a favorable linear response from 1 to 100 μmol L−1 with a detection limit of 0.96 nmol L−1. [ABSTRACT FROM AUTHOR]

Here, a near-infrared (NIR) light-controlled, ultrasensitive one-step photoelectrochemical (PEC) strategy was constructed to simultaneously detect cell apoptosis indicators, phosphatidylserine (Pho) and sodium–potassium adenosine triphosphatase (Sat), on living cancer cells. Using NIR light as excitation, the signal probe methylene blue (Tagkinetic) could be released, leading to a gradually decreased photocurrent signal Ikinetic; meanwhile, the photocurrent Istable of the signal probe carbon quantum dots (Tagstable) remained stable. The simultaneous detection of Pho and Sat could be achieved based on rapid one-step PEC detection under single NIR light with the assistance of a smart signal decryption strategy with Ikinetic and Istable. Importantly, this proposal provides more effective drug candidates with milder pharmaceutical effect but improved safety. [ABSTRACT FROM AUTHOR]

By using multivalent manganese oxides microflowers (MnOx MFs) as prominent a coreaction accelerator in luminol/dissolved oxygen system, and by combining these with DNA nanostructures for efficient immobilization of the electrochemiluminescence (ECL) quencher doxorubicin-ferrocenecarboxylic acid (Dox-FcCOOH), an ultrasensitive biosensing platform was constructed to conduct a microRNA assay in tumour cells. [ABSTRACT FROM AUTHOR]

Herein, by anchoring cholesterol-labelled DNA probes to silicon-supported lipid bilayers via cholesterol–lipid interaction, a dynamic three-dimensional (3D) DNA nanostructure could be facilely assembled, which is applied as a microRNA (miRNA)-induced self-powered 3D DNA nanomachine with high movement efficiency. Once the self-powered 3D DNA nanomachine is triggered by target miRNA, it achieves autonomous operation without external addition of fuel DNA strands or protein enzymes. Impressively, the biocompatible lipid bilayers not only preserve the biological character of the DNA probes, but also improve the movement efficiency of the DNA nanomachine, which directly solves the key challenge of the steric barrier effect of traditional rigid surfaces (Au or silicon) for DNA probe diffusion. As a proof of concept, our proposed DNA nanomachine is successfully applied in rapid and sensitive detection of miRNAs, which gives a new idea for the construction of highly efficient DNA nanomachines for biosensing and clinic diagnosis. [ABSTRACT FROM AUTHOR]

Herein, a novel photoelectrochemical (PEC) assay was developed for the sensitive detection of C-reactive protein (CRP) based on a zirconium-based metal–organic framework (PCN-777) as the photoelectric material and thioflavin-T (Th-T) as the effective signal sensitizer coupled with rolling circle amplification (RCA). [ABSTRACT FROM AUTHOR]

On the basis of BSA stabilized tetraphenylethylene nanocrystals (BSA-TPE NCs) as aggregation-induced enhanced electrochemiluminescence (ECL) emitters with high ECL efficiency and good biocompatibility, as well as molecular recognition between β-CD and ferrocene, an ultrasensitive and versatile ECL biosensing platform was constructed to achieve microRNA detection in cancer cells. [ABSTRACT FROM AUTHOR]

In this work, a novel “signal on” photoelectrochemistry (PEC) biosensor was constructed with dual-functional hemin as a signal quencher and electronic mediator for ultrasensitive target microRNA-141 assay with the assistance of T7 exonuclease (Exo)-initiated target amplification technology. [ABSTRACT FROM AUTHOR]

In this work, a novel fluorescent assay was proposed for the ultrasensitive detection of microRNA-21 (miRNA-21) based on the efficient immobilization of protoporphyrin IX (PPIX) as signal indicators in massive G-quadruplex structures obtained by target recycling, three-dimensional DNA walker and a rolling circle amplification (RCA) coupled cascade nucleic acid amplification strategy. [ABSTRACT FROM AUTHOR]

Herein, an adenosine triphosphate (ATP)-fueled nucleic acid signal amplification strategy based on toehold-mediated strand displacement (TMSD) and fluorescence resonance energy transfer (FRET) was proposed for highly sensitive detection of microRNA-21. More importantly, the target microRNA-21 could be regenerated with ATP as the fuel rather than a nucleotide segment in conventional approaches, which made the proposed strategy simple and efficient due to the high affinity and strength of the aptamer–target interaction. [ABSTRACT FROM AUTHOR]

An electrochemiluminescence biosensor was proposed based on distance-controlled energy transfer and a 3D-DNA walking machine network to significantly improve mass transport and offer an ultrasensitive and controllable strategy for the detection of different types of target. [ABSTRACT FROM AUTHOR]

Electrochemiluminescence (ECL) has attracted much attention in various fields of analysis owing to low background signals, high sensitivity, and excellent controllability. In recent years, to further boost the performance of biosensors, diverse output signal modes have been developed, which exhibited respective advantages. In this review, we summarize the latest sensing applications of ECL bioanalysis by generalizing different output signal modes and give future perspectives for new developments in ECL analytical technology. [ABSTRACT FROM AUTHOR]

A sensitive electrochemiluminescent (ECL) aptasensor consisting of a novel ECL signal tag of DNA nanoflowers (DNA NFs) and a highly efficient target conversion strategy for the MUC1 assay was developed, which not only increased the stability for luminophore loading, but also greatly improved the detection sensitivity. [ABSTRACT FROM AUTHOR]

An ultrasensitive fluorescence assay for intracellular Pb2+ determination was proposed through target–intermediate recycling amplification based on metal-assisted DNAzyme catalysis and strand displacement reactions. Compared with only target recycling-based fluorescence assay with an M amplification ratio, the proposed assay could achieve an M×N amplification ratio to obtain an improved sensitivity by more than 10 times, in which M and N are the amplification ratios of target recycling and intermediate recycling, respectively. Remarkably, this proposed ultrasensitive fluorescence assay could be applied to the determination of various analytes with the well-designed detection probe, especially in intracellular assay, providing a promising tool for clinical diagnosis and biomedical detection. [ABSTRACT FROM AUTHOR]

Herein, a rigid 3D DNA nanopillar was used to investigate the influence of spatial organization on the cascade activity in multienzyme systems, realizing controllable regulation of the mimic enzyme ratio and spacing for acquiring a high-efficiency enzyme cascade catalytic platform. Initially, the ratio of mimic enzyme AuNPs (glucose oxidase-like activity) and hemin/G-quadruplex DNAzyme (peroxidase-like activity) fixed at the designed position was adjusted by changing the number of edges in a DNA polyhedron, resulting in an optimal mimic enzyme ratio of 1 : 4 with a quadrangular prism as the scaffold. Notably, the DNA nanopillar formed by quadrangular prism layer-by-layer assembly acted as a track for directional and controllable movement of a bipedal DNA walker based on the toehold mediated strand displacement reaction (TSDR), which endowed the assay system with continuous enzyme spacing regulation compared with previous enzyme cascade systems that induced inflexible operation. Furthermore, enzyme mimetics in this work circumvented the drawbacks of natural enzymes, such as time-consuming purification processes and poor thermal stability. As a proof of concept, the proposed dual regulation strategy of cascade enzymes was applied in the ultrasensitive electrochemical detection of Pb 2+ , which provided a new route to fabrication of high-performance artificial enzyme cascade platforms for ultimate application in bioanalysis and biodiagnostics., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

A kind of organic microcrystal, 9,10-diphenylanthracene microcrystals (DPA MCs), was developed as a novel electrochemiluminescence (ECL) coreactant accelerator to efficiently catalyze dissolved O 2 for more reactive oxygen species (ROSs) generation, achieving intense ECL for a H 2 O 2 -free luminol system. Moreover, based on this ternary ECL system, a signal "off-on" ECL biosensor for microRNA-21 (miRNA-21) detection was constructed combining a sensitive target recycling amplification strategy and an enzyme-mediated recycling strand displacement reaction (RSDR).

By using multivalent manganese oxides microflowers (MnOx MFs) as prominent a coreaction accelerator in luminol/dissolved oxygen system, and by combining these with DNA nanostructures for efficient immobilization of the electrochemiluminescence (ECL) quencher doxorubicin-ferrocenecarboxylic acid (Dox-FcCOOH), an ultrasensitive biosensing platform was constructed to conduct a microRNA assay in tumour cells.

Herein, we report a three-dimensional (3D) DNA walking nanomachine innovatively constructed from a functionalized 3D DNA track, which runs in an orderly manner with favorable directionality to allow for programming certain pathways of information transduction for some target tasks. The nanomachine was constructed using a departure station of walker (U B + W) and a functionalized 3D track, which was made up of a rolling circle amplification (RCA)-generated backbone chain and numerous triangular rung units with stators (U A + S) assembled into a repeating array along the backbone. A specific domain (SD) was designed at the 5'-end of the backbone to capture the U B + W, and stators with specific RNA substrates were immobilized at the three U A corners for the DNA walker to travel on. Powered by 10-23 DNAzyme, the DNA walker started moving from the SD end to the other end of the track by the autonomous cleavage of RNA substrates. Significantly, the homogeneous distribution of stators in the longitudinal and horizontal extensions paved a specific path for each walker to move along the 3D track. This resulted in random and inactive self-avoiding walking; thus, the nanomachine exhibited good executive ability. These properties allowed the DNA walking nanomachine to program the certain pathways of information transduction for the stepwise and programmed execution of some target tasks, such as the synthesis of specific polyorganics and cargo delivery. We believe that such a 3D DNA walking nanomachine could enrich the concept in the field of dynamic DNA nanotechnology, and may improve the development of novel DNA nanomachines in cargo delivery and composite product synthesis., Competing Interests: The authors declare no competing financial interest., (This journal is © The Royal Society of Chemistry.)

Herein, by directly introducing mismatched reactant DNA, high-reactivity and high-threshold enzyme-free target recycling amplification (EFTRA) is explored. The developed high-efficiency EFTRA (HEEFTRA) was applied as a programmable DNA signal converter, possessing higher conversion efficiency than the traditional one with perfect complement owing to the more negative reaction standard free energy (Δ G ). Once traces of input target miRNA interact with the mismatched reactant DNA, amounts of ferrocene (Fc)-labeled output DNA could be converted via the EFTRA. Impressively, the Fc-labeled output DNA could be easily captured by the DNA tetrahedron nanoprobes (DTNPs) on the electrode surface to form triplex-forming oligonucleotide (TFO) at pH = 7.0 for sensitive electrochemical signal generation and the DTNPs could be regenerated at pH = 10.0, from which the conversion efficiency ( N ) will be accurately obtained, benefiting the selection of suitable mismatched bases to obtain high-efficiency EFTRA (HEEFTRA). As a proof of concept, the HEEFTRA as an evolved DNA signal converter is successfully applied for the ultrasensitive detection of miRNA-21, which gives impetus to the design of other signal converters with excellent efficiency for ultimate applications in sensing analysis, clinical diagnosis, and other areas., (This journal is © The Royal Society of Chemistry 2020.)

A new strategy was described for amplifying the response of the antigen-antibody sensing processes by functionalizing SiO(2) nanoparticles labeled secondary antibodies based on a sandwich immunoassay in this work. At first, the multi-walled carbon nanotubes (CNTs) were individually dispersed in the aqueous bovine serum albumin (BSA) to obtain BSA molecules coated CNTs (BSA-CNTs). Then the gold colloids (nano-Au) were absorbed on the BSA-CNTs surface by the amido and disulfide groups of BSA. Later, a functionalized gold/carbon nanotube composite nanohybrid (DpAu/nano-Au/BSA-CNTs) modified electrode was developed by electrochemical deposition of Au(3+) onto nano-Au/BSA-MWNTs surface. Thus, a sensitive immunosensor for carbohydrate antigen 19-9 (CA19-9) has been constructed by further employment of Nafion coated SiO(2) nanoparticles labeled secondary antibody (SiO(2)-Ab(2)) for the signal amplification. More importantly, the loading of SiO(2)-Ab(2) can not only cause the construction of the dielectric antigen-antibody immunocomplex layer but also introduce the insulated Nafion coated SiO(2) nanoparticles which demonstrate the relatively high resistance, resulting in a strong detection signal. The proposed sensing strategy provides a wide linear dynamic range from 0.15 to 150 U mL(-1) with a low detection limit of 0.06 U mL(-1) at 3 times the background noise. Moreover, the extremely high stability of the functionalized gold/carbon nanotube composite nanohybrid monolayer allows the designed biosensing interface to obtain a good stability and long-term life.