Confined DNA tetrahedral molecular sieve for size-selective electrochemiluminescence sensing.

Size selectivity is crucial in highly accurate preparation of biosensors. Herein, we described an innovative electrochemiluminescence (ECL) sensing platform based on the confined DNA tetrahedral molecular sieve (DTMS) for size-selective recognition of nucleic acids and small biological molecule. Firstly, DNA template (T) was encapsulated into the inner cavity of DNA tetrahedral scaffold (DTS) and hybridized with quencher (Fc) labeled probe DNA to prepare DTMS, accordingly inducing Ru(bpy) and Fc closely proximate, resulting the sensor in a "signal-off" state.

DNA tetrahedral scaffold-corbelled 3D DNAzyme walker for electrochemiluminescent aflatoxin B detection.

The reaction efficiency of surface-based DNA walker can directly affect the properties of a biosensor. Herein, three-dimensional (3D) DNAzyme walker were first fixed on the top of DNA tetrahedral scaffold to improve the immobilization efficiency. Ferrocene (Fc) that labeled at substrate strand ends effectively quenched the electrochemiluminescence (ECL) signal of Ru(bpy)(cpaphen), yielding the sensor in a "signal-off" state.

Two-step förster resonance energy transfer amplification for ratiometric detection of pathogenic bacteria in food samples.

We described a two-step förster resonance energy transfer (FRET) system for ratiometric Staphylococcus aureus (S. aureus) detection based on a dual-recognition proximity binding-induced toehold strand displacement reactions (TSDR). Ru(bpy) and platinum nanoparticles (Pt NPs) labeled DNA (Ru-S3 and Pt NPs-S4) hybridized to enable the occurrence of the primary FRET using Ru(bpy) as the energy donor and Pt NPs as the energy acceptor.

CTnI diagnosis in myocardial infarction using G-quadruplex selective Ir(Ⅲ) complex as effective electrochemiluminescence probe.

In this work, strong electrochemiluminescence (ECL) emission was achieved by using one type of the G-quadruplex selective iridium (III) complex as an efficient ECL signal probe. Based on the typical sandwich immunoreaction between the cardiac troponin-I antigen (cTnI) and its corresponding antibody, iridium (III) complex was introduced according to its specific interaction with G-quadruplex DNA that modified on the surface of negatively charged gold nanoparticles ((-)AuNPs), inducing an increased ECL signal, which was proportional to cTnI concentration. Based on of this, quantitative detection of cTnI could be realized in the range of 5.

G-quadruplex-selective iridium(III) complex as a novel electrochemiluminescence probe for switch-on assay of double-stranded DNA.

In this work, we synthesized an iridium(III) complex and studied its selective ability to interact with a specific G-quadruplex DNA sequence (GTGGGTAGGGCGGGTTGG). Results showed that the iridium(III) complex exhibits high selectivity for the G-quadruplex DNA and could be used as an efficient electrochemiluminescence (ECL) probe in a switch-on assay format for the detection of double-stranded DNA (dsDNA). To construct the assay, a hairpin-structured capture probe (CP) which was modified by thiol at its 3' end and contained the G-quadruplex sequence at its 5' end was firstly immobilized on a gold electrode.

Zettomole electrochemical HIV DNA detection using 2D DNA-Au nanowire structure, hemin/G-quadruplex and polymerase chain reaction multi-signal synergistic amplification.

Multi-signal synergistically amplified electrochemical sensing of HIV DNA was proposed based on two-dimensional (2D) DNA-Au nanowire structure coupled with hemin/G-quadruplex and polymerase chain reaction (PCR). In the design, by using target HIV DNA as the template, PCR generated numbers of double-stranded DNA (dsDNA) with free single-stranded DNA (ssDNA) tails on one side and free G-quadruplex sequences on the other side. Then, the ssDNA tails of the PCR products were hybridized with the capture probe (CP) to introduce the hemin/G-quadruplex to the electrode surface as a redox-active reporter and to amplify the electrochemical signal as mimic peroxidase catalysis in the presence of HO.

Polymerase chain reaction-based ultrasensitive detection of HBV DNA via G-quadruplex selective iridium(III) complex luminescent probe.

Polymerase chain reaction (PCR) is the gold standard for low-abundant DNA detection. Here, to expand the application of PCR with novel detecting methods, we developed a label-free fluorescent sensor for ultrasensitive and one-step detection of hepatitis B virus (HBV) DNA using the G-quadruplex selective iridium(III) complex luminescent probe. By using HBV DNA as the template with two hairpin structure primers that contained oxyethylene glycol tethers, PCR amplification occurred and generated numbers of specific PCR products with free G-quadruplex sequences at both ends.

Ultrasensitive and label-free detection of ATP by using gold nanorods coupled with enzyme assisted target recycling amplification.

Abnormal concentration of adenosine triphosphate (ATP) is directly asscociate with several diseases. Thus, sensitive detection of ATP is essential to early diagnosis of disease. Herein, we described an ultrasensitive strategy for ATP detection by using positively charged gold nanorods ((+)AuNRs) as an efficient fluorescence quenching platform, coupled with exonuclease Ⅲ (Exo Ⅲ) assisted target recycling amplification.

One-step and ultrasensitive ATP detection by using positively charged nano-gold@graphene oxide as a versatile nanocomposite.

A versatile nanocomposite was simply prepared based upon the electrostatic adsorption of positively charged gold nanoparticles with negatively charged graphene oxide (nano-gold@GO), and utilized as a novel fluorescence quenching platform for ultrasensitive detection of adenosine triphosphate (ATP). In the designed system, DNA-stabilized Ag nanoclusters (DNA/AgNCs) were used as fluorescent probes, DNA duplex was formed in the presence of ATP, and they can electrostatically adsorb onto the surface of nano-gold@GO to quench the fluorescence signal. Upon the addition of exonuclease III (Exo III), the DNA duplex would be hydrolyzed into DNA fragments and resulted in the recovery of the fluorescence signals due to the diffusion of AgNCs away from nano-gold@GO.

Electrochemical aptamer-based determination of protein tyrosine kinase-7 using toehold-mediated strand displacement amplification on gold nanoparticles and graphene oxide.

An electrochemical method is described for ultrasensitive determination of protein tyrosine kinase-7 (PTK7). It is based on (a) the use of positively charged gold nanoparticles (AuNPs) and negatively charged graphene oxide (GO), and (b) of toehold-mediated strand displacement amplification. A hairpin probe 2 (HP) containing the sgc8 aptamer was used to modify a glassy carbon electrode (GCE).

Fluorometric determination of mercury(II) using positively charged gold nanoparticles, DNA-templated silver nanoclusters, T-Hg(II)-T interaction and exonuclease assisted signal amplification.

The authors describe a method for detection of Hg by using positively charged gold nanoparticles ((+)AuNPs) as a quencher of the fluorescence of DNA-capped silver nanoclusters (DNA-AgNCs) which are negatively charged. In the presence of Hg, a DNA duplex is formed through T-Hg-T coordination chemistry. The duplex can be digested by exonuclease III to form smaller DNA fragments.

A gold nanoparticle based fluorescent probe for simultaneous recognition of single-stranded DNA and double-stranded DNA.

A fluorescent method is described for simultaneous recognition of single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA). It is based on the quenching of the fluorescence of fluorophore labeled DNA probes by gold nanoparticles (AuNPs). To demonstrate feasibility, two DNA probes labeled with spectrally different fluorophores were designed.

An ultrasensitive and switch-on platform for aflatoxin B detection in peanut based on the fluorescence quenching of graphene oxide-gold nanocomposites.

Graphene oxide-gold nanocomposites (GO/AuNCs) were prepared and used as a novel fluorescence quenching platform for ultrasensitive detection of aflatoxin B (AFB) coupled with hybridization chain reaction (HCR) amplification. In the designed system, two fluorophore labeled hairpin probes (HP/HP) were introduced, and the fluorescence signals of them were effectively quenched due to the adsorption on GO/AuNCs. Associate probe (AP) was used for the specific recognition of AFB, and the stem-loop structure of it was opened.

Label-Free Platform for MicroRNA Detection Based on the Fluorescence Quenching of Positively Charged Gold Nanoparticles to Silver Nanoclusters.

A novel strategy was developed for microRNA-155 (miRNA-155) detection based on the fluorescence quenching of positively charged gold nanoparticles [(+)AuNPs] to Ag nanoclusters (AgNCs). In the designed system, DNA-stabilized Ag nanoclusters (DNA/AgNCs) were introduced as fluorescent probes, and DNA-RNA heteroduplexes were formed upon the addition of target miRNA-155. Meanwhile, the (+)AuNPs could be electrostatically adsorbed on the negatively charged single-stranded DNA (ssDNA) or DNA-RNA heteroduplexes to quench the fluorescence signal.

A cyclometalated iridium(III) complex used as a conductor for the electrochemical sensing of IFN-γ.

A novel iridium(III) complex was prepared and used as a conductor for sensitive and enzyme-free electrochemical detection of interferon gamma (IFN-γ). This assay is based on a dual signal amplification mechanism involving positively charged gold nanoparticles ((+)AuNPs) and hybridization chain reaction (HCR). To construct the sensor, nafion (Nf) and (+)AuNPs composite membrane was first immobilized onto the electrode surface.

Sensitive detection of miRNA by using hybridization chain reaction coupled with positively charged gold nanoparticles.

Positively charged gold nanoparticles (+)AuNPs can adsorb onto the negatively charged surface of single-stranded DNA (ssDNA) or double-stranded DNA (dsDNA). Herein, long-range dsDNA polymers could form based on the hybridization chain reaction (HCR) of two hairpin probes (H1 and H2) by using miRNA-21 as an initiator. (+)AuNPs could adsorb onto the negatively charged surface of such long-range dsDNA polymers based on the electrostatic adsorption, which directly resulted in the precipitation of (+)AuNPs and the decrease of (+)AuNPs absorption spectra.

Fluorescence recognition of double-stranded DNA based on the quenching of gold nanoparticles to a fluorophore labeled DNA probe.

An ultrasensitive fluorescent platform for sequence-specific recognition of double-stranded DNA (dsDNA) based on the quenching of gold nanoparticles (AuNPs) to a fluorophore labeled DNA probe was developed. The target dsDNA could hybridize with the loop portion of the molecular beacon (MB) to form a triplex DNA structure and opened the "stem-loop" structure of the MB; such triplex DNA was used as an assistant probe (AP). Meanwhile, a fluorophore labeled DNA-AuNP probe that contained a specific enzyme cleavage site was introduced and its fluorescence signal was efficiently quenched due to the vicinity of the fluorophore to the AuNP surface.

Ultrasensitive electrochemical detection of protein tyrosine kinase-7 by gold nanoparticles and methylene blue assisted signal amplification.

We present here an ultrasensitive and simple strategy for protein tyrosine kinase-7 (PTK7) detection based on the recognition-induced structure change of sgc8 aptamer, and the signal change of methylene blue (MB) that interacted with sandwiched DNA complex. To construct such a sensor, an homogeneous nano-surface was formed firstly on the glass carbon electrode (GCE) by using negatively charged Nafion (Nf) as the inner layer and positively charged gold nanoparticles ((+)AuNPs) as the outer layer, followed by the immobilization of sgc8 aptamer based on Au-S bond. In the presence of helper probe (HP), sandwiched DNA complex was formed between the sgc8 aptamer and the DNA modified gold nanoparticle probe (DNA-AuNPs).

Ultrasensitive electrochemical sensor for Hg(2+) by using hybridization chain reaction coupled with Ag@Au core-shell nanoparticles.

A novel electrochemical biosensor for Hg(2+) detection was reported by using DNA-based hybridization chain reaction (HCR) coupled with positively charged Ag@Au core-shell nanoparticles ((+)Ag@Au CSNPs) amplification. To construct the sensor, capture probe (CP ) was firstly immobilized onto the surface of glass carbon electrode (GCE). In the presence of Hg(2+), the sandwiched complex can be formed between the immobilized CP on the electrode surface and the detection probe (DP) modified on the gold nanoparticles (AuNPs) based on T-Hg(2+)-T coordination chemistry.

Enhanced electrochemical recognition of double-stranded DNA by using hybridization chain reaction and positively charged gold nanoparticles.

Enhanced sequence-specific recognition of double-stranded DNA (dsDNA) was realized by using hybridization chain reaction (HCR) and positively charged gold nanoparticles ((+)AuNPs) dual signal amplification. To construct such a sensor, capture probe was initially assembled onto gold electrode surface. Upon addition of dsDNA, sandwiched DNA complex was formed between the capture probe and the detection probe, then another exposed part of the detection probe opened two alternating DNA hairpins (H1 and H2) in turn and initiated HCR to form a double-helix.