Multiplexed aptasensors and amplified DNA sensors using functionalized graphene oxide: application for logic gate operations

A label-free and enzyme-free system for operating various logic devices using poly(thymine)-templated CuNPs and SYBR Green I as signal transducers

For the first time by integrating fluorescent polyT-templated CuNPs and SYBR Green I, a basic INHIBIT gate and four advanced logic circuits (2-to-1 encoder, 4-to-2 encoder, 1-to-2 decoder and 1-to-2 demultiplexer) have been conceptually realized under label-free and enzyme-free conditions. Taking advantage of the selective formation of CuNPs on ss-DNA, the implementation of these advanced logic devices were achieved without any usage of dye quenching groups or other nanomaterials like graphene oxide or AuNPs since polyA strands not only worked as an input but also acted as effective inhibitors towards polyT templates, meeting the aim of developing bio-computing with cost-effective and operationally simple methods. In short, polyT-templated CuNPs, as promising fluorescent signal reporters, are successfully applied to fabricate advanced logic devices, which may present a potential path for future development of molecular computations.

An electrochemical aptasensor for detection of IFN-γ using graphene and a dual signal amplification strategy based on the exonuclease-mediated surface-initiated enzymatic polymerization

Tuberculosis is one of the major health problems in the world. The cytokine interferon γ (IFN-γ) is associated with the disease-specific immune responses and is used as a tuberculosis diagnosis marker. In this study, a novel electrochemical aptasensor was developed for IFN-γ detection based on the exonuclease-catalyzed target recycling and the TdT-mediated cascade signal amplification. To construct the aptasensor, a previously hybridized double-stranded DNA (capture probe hybridization with a complementary IFN-γ binding aptamer) was immobilized on a gold nanoparticle-graphene (Au-Gra) nanohybrid film-modified electrode. In the presence of IFN-γ, the formation of an aptamer-IFN-γ complex leads to the liberation of the aptamer from the double-stranded DNA (dsDNA). Using exonuclease, the aptamer was selectively digested, and IFN-γ was released for the target recycling. A large amount of single-stranded capture probes formed and led to the hybridization with signal probe-labelled Au@Fe3O4. Then, the labelled signal probe sequences were catalyzed at the 3'-OH group by terminal deoxynucleotidyl transferase (TdT) to form a long single-stranded DNA structure. As a result, the electron mediator hexaammineruthenium(III) chloride ([Ru(NH3)6](3+)) electrostatically adsorbed onto DNA producing a strong electrochemical signal which can be used to quantitatively measure the IFN-γ levels. With the conducting nanomaterial Au-Gra as a substrate and the target recycling-based surface-initiated enzymatic polymerization-mediated signal amplification strategy, the proposed aptasensor displayed a broad linearity with a low detection limit of 0.003 ng mL(-1). Moreover, the resulting aptasensor exhibited good specificity, acceptable reproducibility and stability, which makes this method versatile and suitable for detecting IFN-γ and other biomolecules.

Fluorescent biosensors enabled by graphene and graphene oxide

During the past few years, graphene and graphene oxide (GO) have attracted numerous attentions for the potential applications in various fields from energy technology, biosensing to biomedical diagnosis and therapy due to their various functionalization, high volume surface ratio, unique physical and electrical properties. Among which, graphene and graphene oxide based fluorescent biosensors enabled by their fluorescence-quenching properties have attracted great interests. The fluorescence of fluorophore or dye labeled on probes (such as molecular beacon, aptamer, DNAzymes and so on) was quenched after adsorbed on to the surface of graphene. While in the present of the targets, due to the strong interactions between probes and targets, the probes were detached from the surface of graphene, generating dramatic fluorescence, which could be used as signals for detection of the targets. This strategy was simple and economy, together with great programmable abilities of probes; we could realize detection of different kinds of species. In this review, we first briefly introduced the history of graphene and graphene oxide, and then summarized the fluorescent biosensors enabled by graphene and GO, with a detailed account of the design mechanism and comparison with other nanomaterials (e.g. carbon nanotubes and gold nanoparticles). Following that, different sensing platforms for detection of DNAs, ions, biomolecules and pathogens or cells as well as the cytotoxicity issue of graphene and GO based in vivo biosensing were further discussed. We hope that this review would do some help to researchers who are interested in graphene related biosening research work.

3D hydrogel scaffold doped with 2D graphene materials for biosensors and bioelectronics

Hydrogels consisting of three-dimensional (3D) polymeric networks have found a wide range of applications in biotechnology due to their large water capacity, high biocompatibility, and facile functional versatility. The hydrogels with stimulus-responsive swelling properties have been particularly instrumental to realizing signal transduction in biosensors and bioelectronics. Graphenes are two-dimensional (2D) nanomaterials with unprecedented physical, optical, and electronic properties and have also found many applications in biosensors and bioelectronics. These two classes of materials present complementary strengths and limitations which, when effectively coupled, can result in significant synergism in their electrical, mechanical, and biocompatible properties. This report reviews recent advances made with hydrogel and graphene materials for the development of high-performance bioelectronics devices. The report focuses on the interesting intersection of these materials wherein 2D graphenes are hybridized with 3D hydrogels to develop the next generation biosensors and bioelectronics.

An enzyme-free and DNA-based Feynman gate for logically reversible operation

A logically reversible Feynman gate was successfully realized under enzyme-free conditions by integrating graphene oxide and DNA for the first time. The gate has a one-to-one mapping function to identify inputs from the corresponding outputs. This type of reversible logic gate may have great potential applications in information processing and biosensing systems.

An ideal detector composed of a 3D Gd-based coordination polymer for DNA and Hg2+ ion

A 3D Gd-based CP was employed as an effective fluorescent sensing platform for DNA and Hg²⁺ ion detection with sensitivity and selectivity, due to its ability to highly quench fluorescence and its different affinities toward ssDNA and dsDNA.

A novel aptamer-mediated CuInS2quantum dots@graphene oxide nanocomposites-based fluorescence “turn off–on” nanosensor for highly sensitive and selective detection of kanamycin

A novel aptamer-mediated fluorescence “turn off–on” nanosensor for highly sensitive and selective detection of kanamycin using CuInS₂quantum dots@graphene oxide.

Electrochemiluminescent molecular logic gates based on MCNTs for the multiplexed analysis of mercury(ii) and silver(i) ions

In this paper, logic gates with electrochemiluminescence (ECL) signal as outputs were constructed based on the use of the thymine (T)-rich (S₁) or cytosine (C)-rich (S₂) oligonucleotides for the selective analysis of mercury ions (Hg²⁺) or silver ions (Ag⁺).

Graphene oxide enhanced specificity at aptamer and its application to multiplexed enzymatic activity sensing

Based on the finding that sufficient GO could enhance the specificity of an ATP aptamer, we proposed a fluorescence assay for alkaline phosphatase and creatine kinase.

Highly intense fluorescence of novel carbon nanocrystals combined with a DNAzyme-assisted autocatalytic multiple amplification strategy for sensitive detection of thrombin

Novel water-soluble CNCs with excellent fluorescence were prepared, and successfully applied to sensitive fluorescence detection of thrombin by using an enzyme-assisted autocatalytic DNA recycling amplification strategy.

Graphene oxide: strategies for synthesis, reduction and frontier applications

In this review article, we describe a general introduction to GO, its synthesis, reduction and some selected frontier applications. Its low cost and potential for mass production make GO a promising building block for functional hybrid materials.

A colorimetric and fluorometric dual-modal DNA logic gate based on the response of a cyanine dye supramolecule to G-quadruplexes

The INHIBIT DNA logic gate with dual-modal outputs based on the response of MTC aggregates to G-quadruplexes.

Graphene-Assisted Label-Free Homogeneous Electrochemical Biosensing Strategy based on Aptamer-Switched Bidirectional DNA Polymerization

In this contribution, taking the discrimination ability of graphene over single-stranded (ss) DNA/double-stranded (ds) DNA in combination with the electrochemical impedance transducer, we developed a novel label-free homogeneous electrochemical biosensor using graphene-modified glassy carbon electrode (GCE) as the sensing platform. To convert the specific aptamer-target recognition into ultrasensitive electrochemical signal output, a novel aptamer-switched bidirectional DNA polymerization (BDP) strategy, capable of both target recycling and exponential signal amplification, was compatibly developed in this study. In this strategy, all the designed DNA structures could be adsorbed on the graphene/GCE and, thus, serve as the electrochemical impedance signal reporter, while the target acts as a trigger of this BDP reaction, in which these designed DNA structures are bound together and, then, converted to long dsDNA duplex. The distinct difference in electrochemical impedance spectroscopy between the designed structures and generated long dsDNA duplex on the graphene/GCE allows label-free and homogeneous detection of target down to femto-gram level. The target can be displaced from aptamer through the polymerization to initiate the next recognition-polymerization cycle. Herein, the design and signaling principle of aptamer-switched BDP amplification system were elucidated, and the working conditions were optimized. This method not only provides a universal platform for electrochemical biosensing but also shows great potential in biological process researches and clinic diagnostics.

Exonuclease-Catalyzed Target Recycling Amplification and Immobilization-free Electrochemical Aptasensor

A simple, sensitive, and selective immobilization-free electrochemical aptasensor had been developed which combines the advantages of the discrimination of the aggregation of long and short DNA on a negatively charged indium tin oxide (ITO) electrode, high selectivity of the aptamer, and high efficiency of exonuclease-catalyzed target recycling amplification. Ochratoxin A (OTA), a type of mycotoxin, has been chosen as the model target. Methylene blue (MB) labeled probe DNA had been hybridized with the OTA aptamer first, which cannot diffuse freely to the negative charged ITO electrode surface due to the repulsion of the negative charges, since the hybridized DNA contains large negative charges. In the presence of target (OTA), the aptamer prefers to form an OTA-aptamer complex in lieu of an aptamer-DNA duplex, which results in the dissociation of probe DNA from the probe DNA-aptamer complex. The released probe DNA could be digested into mononucleotides, including a MB-labeled electroactive mononucleotide (eT), due to the employment of the RecJf exonuclease, a single-stranded DNA specific exonuclease. Since the eT contains little negative charge, it can diffuse easily to the negative charged ITO electrode surface, which results in the enhanced electrochemical response detected. At the same time, the aptamer in the OTA-aptamer complex can be digested by RecJf exonuclease also to liberate the target, which can participate in the next reaction cycling and realize the electrochemical signal amplification. Based on this strategy, an ultrasensitive homogeneous immobilization-free electrochemical aptasensor for OTA can be developed with a low detection limit (LOD) of 0.004 ng mL(-1) (S/N = 3). The proposed biosensor combines the advantages of the simplicity of immobilization-free homogeneous ITO based electrochemical determination, high efficiency of exonuclease-catalyzed target recycling, and high selectivity of the aptamer. The fabricated biosensor has been applied to detect OTA in real samples with satisfactory results. The same strategy can be applied to develop biosensors for diverse targets.

Isothermal Amplification of Nucleic Acids

Isothermal amplification of nucleic acids is a simple process that rapidly and efficiently accumulates nucleic acid sequences at constant temperature. Since the early 1990s, various isothermal amplification techniques have been developed as alternatives to polymerase chain reaction (PCR). These isothermal amplification methods have been used for biosensing targets such as DNA, RNA, cells, proteins, small molecules, and ions. The applications of these techniques for in situ or intracellular bioimaging and sequencing have been amply demonstrated. Amplicons produced by isothermal amplification methods have also been utilized to construct versatile nucleic acid nanomaterials for promising applications in biomedicine, bioimaging, and biosensing. The integration of isothermal amplification into microsystems or portable devices improves nucleic acid-based on-site assays and confers high sensitivity. Single-cell and single-molecule analyses have also been implemented based on integrated microfluidic systems. In this review, we provide a comprehensive overview of the isothermal amplification of nucleic acids encompassing work published in the past two decades. First, different isothermal amplification techniques are classified into three types based on reaction kinetics. Then, we summarize the applications of isothermal amplification in bioanalysis, diagnostics, nanotechnology, materials science, and device integration. Finally, several challenges and perspectives in the field are discussed.

Design of nuclease-based target recycling signal amplification in aptasensors

Compared with conventional antibody-based immunoassay methods, aptasensors based on nucleic acid aptamer have made at least two significant breakthroughs. One is that aptamers are more easily used for developing various simple and rapid homogeneous detection methods by "sample in signal out" without multi-step washing. The other is that aptamers are more easily employed for developing highly sensitive detection methods by using various nucleic acid-based signal amplification approaches. As many substances playing regulatory roles in physiology or pathology exist at an extremely low concentration and many chemical contaminants occur in trace amounts in food or environment, aptasensors for signal amplification contribute greatly to detection of such targets. Among the signal amplification approaches in highly sensitive aptasensors, the nuclease-based target recycling signal amplification has recently become a research focus because it shows easy design, simple operation, and rapid reaction and can be easily developed for homogenous assay. In this review, we summarized recent advances in the development of various nuclease-based target recycling signal amplification with the aim to provide a general guide for the design of aptamer-based ultrasensitive biosensing assays.

Fluorometric detection of mutant DNA oligonucleotide based on toehold strand displacement-driving target recycling strategy and exonuclease III-assisted suppression

We describe here a fluorometric assay for sensitive detection of oligonucleotides, based on a target recycling amplification strategy driven by toehold-mediated strand displacement reaction and on exonuclease III (Exo Ш)-assisted fluorescence background suppression strategy. The network consists of a pair of partially complementary DNA hairpins (HP1 and HP2) with 3' overhang ends, between which the spontaneous hybridization is kinetically hindered by the stems. The target DNA is repeatedly used to trigger a recycling progress between the hairpins, generating numerous HP1-HP2 duplex complexes. Exo III was then employed to digest the double strand parts of the residual hairpins and the intermediate products. The fluorescent dye, SYBR Green I, binds to the double-strand DNA products and emits strong fluorescence to achieve sensitive detection of the target DNA with the detection limit of 5.34 pM. Moreover, this proposed strategy showed high discrimination efficiency towards target DNA against mismatched DNA and was successfully applied in the analysis of human serum sample.

Functional nucleic acid-based sensors for heavy metal ion assays

Heavy metal contaminants such as lead ions (Pb(2+)), mercury ions (Hg(2+)) and silver ions (Ag(+)) can cause significant harm to humans and generate enduring bioaccumulation in ecological systems. Even though a variety of methods have been developed for Pb(2+), Hg(2+) and Ag(+) assays, most of them are usually laborious and time-consuming with poor sensitivity. Due to their unique advantages of excellent catalytic properties and high affinity for heavy metal ions, functional nucleic acids such as DNAzymes and aptamers show great promise in the development of novel sensors for heavy metal ion assays. In this review, we summarize the development of functional nucleic acid-based sensors for the detection of Pb(2+), Hg(2+) and Ag(+), and especially focus on two categories including the direct assay and the amplification-based assay. We highlight the emerging trends in the development of sensitive and selective sensors for heavy metal ion assays as well.

Enzyme-assisted target recycling (EATR) for nucleic acid detection

Fast, reliable and sensitive methods for nucleic acid detection are of growing practical interest with respect to molecular diagnostics of cancer, infectious and genetic diseases. Currently, PCR-based and other target amplification strategies are most extensively used in practice. At the same time, such assays have limitations that can be overcome by alternative approaches. There is a recent explosion in the design of methods that amplify the signal produced by a nucleic acid target, without changing its copy number. This review aims at systematization and critical analysis of the enzyme-assisted target recycling (EATR) signal amplification technique. The approach uses nucleases to recognize and cleave the probe-target complex. Cleavage reactions produce a detectable signal. The advantages of such techniques are potentially low sensitivity to contamination and lack of the requirement of a thermal cycler. Nucleases used for EATR include sequence-dependent restriction or nicking endonucleases or sequence independent exonuclease III, lambda exonuclease, RNase H, RNase HII, AP endonuclease, duplex-specific nuclease, DNase I, or T7 exonuclease. EATR-based assays are potentially useful for point-of-care diagnostics, single nucleotide polymorphisms genotyping and microRNA analysis. Specificity, limit of detection and the potential impact of EATR strategies on molecular diagnostics are discussed.

Colorimetric Detection of Small Molecules in Complex Matrixes via Target-Mediated Growth of Aptamer-Functionalized Gold Nanoparticles

A versatile and sensitive colorimetric assay that allows the rapid detection of small-molecule targets using the naked eye is demonstrated. The working principle of the assay integrates aptamer-target recognition and the aptamer-controlled growth of gold nanoparticles (Au NPs). Aptamer-target interactions modulate the amount of aptamer strands adsorbed on the surface of aptamer-functionalized Au NPs via desorption of the aptamer strands when target molecules bind with the aptamer. Depending on the resulting aptamer coverage, Au NPs grow into morphologically varied nanostructures, which give rise to different colored solutions. Au NPs with low aptamer coverage grow into spherical NPs, which produce red-colored solutions, whereas Au NPs with high aptamer coverage grow into branched NPs, which produce blue-colored solutions. We achieved visible colorimetric response and nanomolar detection limits for the detection of ochratoxin A (1 nM) in red wine samples, as well as cocaine (1 nM) and 17β-estradiol (0.2 nM) in spiked synthetic urine and saliva, respectively. The detection limits were well within clinically and physiologically relevant ranges, and below the maximum food safety limits. The assay is highly sensitive, specific, and able to detect an array of analytes rapidly without requiring sophisticated equipment, making it relevant for many applications, such as high-throughput drug and clinical screening, food sampling, and diagnostics. Furthermore, the assay is easily adapted as a chip-based platform for rapid and portable target detection.

Ultrasensitive and feasibly achieved protein detection based on the integration of three signal amplification reactions via sharing a DNA sequence

This communication reports a novel strategy for the detection of proteins based on the integration of three signal amplification reactions via sharing a specially designed DNA sequence. This strategy has been demonstrated by the assay of human TNF-α in the serum of ovarian cancer patients, showing potential clinical applications.

A label-free fluorescence assay for thrombin based on aptamer exonuclease protection and exonuclease III-assisted recycling amplification-responsive cascade zinc(II)-protoporphyrin IX/G-quadruplex supramolecular fluorescent labels

A simple, label-free and sensitive fluorescence protein assay has been developed on the basis of aptamer exonuclease protection and exonuclease III (Exo III)-assisted recycling amplification-responsive cascade ZnPPIX/G-quadruplex supramolecular fluorescent labels. In the sensing system, a special aptamer probe containing the aptamer sequence at the 3'-terminus and the DNAzyme sequence at the 5'-terminus was applied, which has the capacity to recognize a protein target with high affinity and specificity. Exonuclease I (Exo I) can efficiently catalyze the degradation of free single stranded DNA probes in the 3' to 5' direction. In the presence of the target protein, the strong binding between the target protein and its aptamer can protect aptamer probes from degradation. Subsequently, the protected aptamer probes act as catalysators to trigger hybridization with the hairpin DNA probe that contains a partially "caged" G-quadruplex sequence. Upon interaction with the protected aptamer probes, the hairpin opens to yield the active G-quadruplex structure. In the presence of exonuclease III (Exo III), Exo III-assisted recycling amplification occurs generating numerous G-quadruplex supramolecular structures. The zinc(ii)-protoporphyrin IX (ZnPPIX) fluorophore binds to the G-quadruplexes and this results in the enhanced fluorescence of the fluorophore. The resulting fluorescence of the ZnPPIX/G-quadruplex provides the readout signal for the sensing event. Thrombin is used as the model analyte in the current proof-of-concept. The developed method was demonstrated to have very high sensitivity for the detection of proteins with a limit of detection of 0.2 pM without using washes or separations. In addition, this new method for protein detection is simple and inherits all the advantages of aptamers. The mechanism, moreover, may be generalized and used for other forms of protein analysis.

A turn-on fluorescent aptasensor for adenosine detection based on split aptamers and graphene oxide

A simple, sensitive and selective turn-on fluorescent aptasensor for adenosine detection was developed based on target-induced split aptamer fragment conjunction and different interactions of graphene oxide and the two states of the designed aptamer sequences.

A universal platform for building molecular logic circuits based on a reconfigurable three-dimensional DNA nanostructure

Molecular logic gates are capable of performing various logic tasks for biomarker detection, disease diagnostics and therapy, and controlling biological progress. Herein, we integrated multiple components of a logic device into a single DNA 3D nano-assembly with a triangular prism structure. Compared with the separate construction of each component in previously reported DNA logic gate systems, such an integrated design strategy made the 3D DNA nanoprism universal for logic gates, it can be reconfigured to execute diverse logic operations. Binary basic logic gates (OR, AND, INHIBIT and XOR), combinatorial gates (INHIBIT-OR), and multi-valued logic gates (ternary INHIBIT gate) were readily achieved by taking this DNA nanoprism as a universal platform. Moreover, a logic gate system for identification of even numbers and odd numbers from natural numbers was established successfully by employing only this single DNA nanoprism and four short single-stranded DNA. The universality of this nanoprism greatly simplified the design of DNA logic gate system. Additionally, this nanoprism was able to perform logic operation steadily in a biological matrix, indicating that this box-like DNA nanostructure applies to logic gates in a complicated environment. This study provided a unique opportunity to design versatile 3D DNA nanostructure-based intelligent nanodevices, which show great potential in biocomputing, multi-parameter sensing, and intelligent disease diagnostics and therapy.

Amplified thrombin aptasensor based on alkaline phosphatase and hemin/G-quadruplex-catalyzed oxidation of 1-naphthol

An alkaline phosphatase (ALP)-based biosensor can in situ generate an electroactive product by enzymatic hydrolysis of inactive substrates. To obtain a higher signal-to-background ratio, a chemical redox cycling signal-amplified strategy based on the addition of a strong reducing agent has often be applied in the construction of ALP-based biosensors. However, the strong reducing agent not only affects the activity of ALP but also readily reacts with dissolved oxygen, leading to inaccurate results. In this work, a new signal-amplified strategy for a thrombin (TB) aptasensor based on the catalytic oxidation of ALP-generated products, 1-naphthol (NP), using hemin/G-quadruplex DNAzymes was reported. We implemented gold-nanoparticle-decorated zinc oxide nanoflowers (Au-ZnO) as the matrix for immobilizing ALP and TB aptamer (TBA) and then labeled it with hemin to form hemin/G-quadruplex/ALP/Au-ZnO bioconjugates (TBA II bioconjugates). Through a "sandwich" reaction, TBA II bioconjugates were captured on the electrode surface. The amplified signal was carried out in two steps: (i) an ALP-catalyzed inactive substrate, 1-naphthyl phosphate (NPP), in situ produces NP on the surface of the electrode; (ii) on the one hand, NP as a new reactant could be directly electrooxidized and generated an electrochemical signal, but, on the other hand, NP could be oxidized by hemin/G-quadruplex in the presence of H2O2, resulting in amplification of the electrochemical signal. The proposed TB aptasensor achieved a linear range of 1 pM to 30 nM with a detection limit of 0.37 pM (defined as S/N = 3).

DNA-based machines

The base sequence in nucleic acids encodes substantial structural and functional information into the biopolymer. This encoded information provides the basis for the tailoring and assembly of DNA machines. A DNA machine is defined as a molecular device that exhibits the following fundamental features. (1) It performs a fuel-driven mechanical process that mimics macroscopic machines. (2) The mechanical process requires an energy input, "fuel." (3) The mechanical operation is accompanied by an energy consumption process that leads to "waste products." (4) The cyclic operation of the DNA devices, involves the use of "fuel" and "anti-fuel" ingredients. A variety of DNA-based machines are described, including the construction of "tweezers," "walkers," "robots," "cranes," "transporters," "springs," "gears," and interlocked cyclic DNA structures acting as reconfigurable catenanes, rotaxanes, and rotors. Different "fuels", such as nucleic acid strands, pH (H⁺/OH⁻), metal ions, and light, are used to trigger the mechanical functions of the DNA devices. The operation of the devices in solution and on surfaces is described, and a variety of optical, electrical, and photoelectrochemical methods to follow the operations of the DNA machines are presented. We further address the possible applications of DNA machines and the future perspectives of molecular DNA devices. These include the application of DNA machines as functional structures for the construction of logic gates and computing, for the programmed organization of metallic nanoparticle structures and the control of plasmonic properties, and for controlling chemical transformations by DNA machines. We further discuss the future applications of DNA machines for intracellular sensing, controlling intracellular metabolic pathways, and the use of the functional nanostructures for drug delivery and medical applications.

Single-layer transition metal dichalcogenide nanosheet-based nanosensors for rapid, sensitive, and multiplexed detection of DNA

Single-layer transition metal dichalcogenide nanosheets, including MoS2, TiS2, and TaS2, are used as novel sensing platforms for sensitive and selective detection of DNA, based on their high fluorescence-quenching ability and different affinities toward single-stranded DNA and double-stranded DNA. Importantly, for the first time, a single-layer TaS2 nanosheet-based multiplexed DNA sensor is also developed.

A coordination and ligand replacement based three-input colorimetric logic gate sensing platform for melamine, mercury ions, and cysteine

A three-input colorimetric logic gate of melamine, cysteine, and Hg²⁺using Au NP has been reported, in which the colour changes of the Au NPs solution provide sensitive and selective detections of melamine, cysteine, and Hg²⁺.

Enzyme-free and DNA-based multiplexer and demultiplexer

A DNA-based 2:1 multiplexer and 1:2 demultiplexer have been conceptually realized in enzyme-free conditions.

Design of enzyme-interfaced DNA logic operations (AND, OR and INHIBIT) with an assaying application for single-base mismatch

We devised AND, OR and INHIBIT logic gates.

A biosensing platform for sensitive detection of concanavalin A based on fluorescence resonance energy transfer from CdTe quantum dots to graphene oxide

The sandwich method can detect different lectins simply by exchanging the carbohydrates functionalized on the quantum dots and graphene oxide.

The graphene/nucleic acid nanobiointerface

In this critical review, we present the recent advances in the design and fabrication of graphene/nucleic acid nanobiointerfaces, as well as the fundamental understanding of their interfacial properties and various nanobiotechnological applications.

G-quadruplex-based logic gates for HgII and AgI ions employing a luminescent iridium(iii) complex and extension of metal-mediated base pairs by polymerase

We report herein the synthesis of a series of cyclometallated iridium(iii) complexes as luminescent G-quadruplex-selective probes to construct AND, OR and INHIBIT logic gates for the detection of Hg^II and Ag^I ions.