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DNA performsa vital function as a carrier of genetic code, but in the field ofnanotechnology, DNA molecules can catalyze chemical reactions in thecell, that is, DNAzymes, or bind with target-specific ligands, thatis, aptamers. These functional DNAs with different modifications havebeen developed for sensing, imaging, and therapeutic systems. Thus,functional DNAs hold great promise for future applications in nanotechnologyand bioanalysis. However, these functional DNAs face challenges, especiallyin the field of biomedicine. For example, functional DNAs typicallyrequire the use of cationic transfection reagents to realize cellularuptake. Such reagents enter the cells, increasing the difficulty ofperforming bioassays in vivo and potentially damaging the cell’snucleus. To address this obstacle, nanomaterials, such as metallic,carbon, silica, or magnetic materials, have been utilized as DNA carriersor assistants. In this Account, we describe selected examples of functionalDNA-containing nanomaterials and their applications from our recentresearch and those of others. As models, we have chosen to highlightDNA/nanomaterial complexes consisting of gold nanoparticles, graphene oxides, and aptamer–micelles, and we illustrate the potentialof such complexes in biosensing, imaging, and medical diagnostics. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, for the first time, Cu nanoparticles (CuNPs) were prepared by seed-mediated growth method with Au nanoparticles (AuNPs) playing the role of seeds. Carbon nanotubes (CNTs) and AuNPs were first dropped on the surface of glassy carbon (GC) electrode, and then the electrode was immersed into growth solution that contained CuSO4 and hydrazine. CuNPs were successfully grown on the surface of the CNTs. The modified electrode showed a very high electrochemical activity for electrocatalytic oxidation of glucose in alkaline medium, which was utilized as the basis of the fabrication of a nonenzymatic biosensor for electrochemical detection of glucose. The biosensor can be applied to the quantification of glucose with a linear range covering from 1.0×10−7 to 5×10−3 M and a low detection limit of 3×10−8 M. Furthermore, the experiment results also showed that the biosensor exhibited good reproducibility and long-term stability, as well as high selectivity with no interference from other oxidable species. [Copyright &y& Elsevier]

A highly selective electrochemical biosensor for the ultrasensitive detection of Hg2+in aqueous solution has been developed based on the strong and specific binding of Hg2+by two DNA thymine bases (T–Hg2+–T) and the use of AuNP-functionalized reporter DNA to achieve signal amplification. [ABSTRACT FROM AUTHOR]

Disease signaling molecules and biomarkers are important in biosensing and biomedicine, and their ultra‐sensitive detection and imaging are critical in medical diagnosis. However, most biomarkers have low levels of expression in cells and are easily degraded; therefore, they cannot be accurately detected in real time by conventional amplification methods, which are typically confined to cell lysates. To achieve highly sensitive detection of intracellular low‐abundance molecules, extensive efforts have been devoted to the development of in situ signal amplification techniques. This review tracks the development of recent advances in in situ signal amplification strategies, and systematically summarizes the advantages and disadvantages of enzymatic and non‐enzymatic amplification techniques for detecting and tracing intracellular targets. Further, perspectives, challenges, and opportunities for intracellular signal amplification are discussed to promote its adoption for in situ signal amplification in clinical settings and to provide new insights into signaling molecules and biomarkers in cellular functions and associated diseases. [ABSTRACT FROM AUTHOR]

Abstract: The self-assembly of cyclodextrin (CD) functionalized graphene (GR) and adamantane-modified horseradish peroxidase (HRP-ADA) by host–guest supramolecular interaction into novel nanostructures in aqueous solution is reported in the present study. Electrochemical impedance spectroscopy and cyclic voltammetry were applied to characterize the self-assembly process and study the electrochemical behaviors of the immobilized proteins. UV–vis spectra indicated that the native structure of HRP was maintained after the assembly, implying good biocompatibility of CD-functionalized GR (CD-GR). Furthermore, the HRP-ADA/CD-GR composites were utilized for the fabrication of enzyme electrodes (HRP-ADA/CD-GR electrodes). The proposed biosensor showed good reproducibility and high sensitivity to H2O2 with the detection limit of 0.1μM. In the range of 0.7–35μM, the catalytic reduction current of H2O2 was proportional to H2O2 concentration. [Copyright &y& Elsevier]

Abstract: A universal sensing platform for fluorescence turn-on detection of biomolecules is developed based on Fenton reaction triggered molecular beacon cleavage. Due to its high quenching efficiency, molecular beacons (MBs)-based sensing systems usually show low background fluorescence and large signal-to-background ratio. Glucose is chosen as a model biomolecule for constructing an MB-based fluorescence sensing system. In the presence of glucose, the glucose oxidase will bind with it and catalyze the oxidation to generate H2O2, which is further decomposed to produce OH through the Fe2+-catalyzed Fenton reaction. Then, in-situ-generated OH can trigger the cleavage of the MB, and its fluorescence intensity will be dramatically increased because of the complete separation of the fluorophore from the quencher. By employing molecular beacon as both recognition and reporter probes to low background signal, the proposed biosensors showed high sensitivity to targets. It also exhibited high selectivity owing to the high specificity of the enzymatic oxidation, which make it valuable for the detection of target biomolecule in complex biological samples. [Copyright &y& Elsevier]

Two-dimensional graphitic carbon nitride nanosheets (CNNSs) with planar graphene-like structure have stimulated increasingly research interest in recent years due to their unique physicochemical properties. CNNSs possess superior stability, high fluorescence quantum yield, low-toxicity, excellent biocompatibility, unique electroluminescent and photoelectrochemical properties, which make them appropriate candidates for biosensing. In this review, we first introduce the preparation and unique properties of CNNSs, with emphasis on their superior properties for biosensing. Then, recent advances of CNNSs in photoelectrochemical biosensing, electrochemiluminescence biosensing and fluorescence biosensing are highlighted. An additional attention is paid to the marriage of CNNSs and nucleic acids, which exhibits great potentials in both biosensing and intracellular imaging. Finally, current challenges and opportunities of this 2D material are outlined. Inspired by the unique properties of CNNSs and their advantages in biological applications, we expect that more attention will be drawn to this promising 2D material and extensive applications can be found in bioanalysis and diseases diagnosis. [ABSTRACT FROM AUTHOR]

Thiophenols are highly toxic industrial materials that, once released, will accumulate in the environment, and ultimately in human bodies, thereby causing serious health problems. To achieve their selective and sensitive detection, a novel near-infrared (NIR) fluorescent probe ( CCP-1) from a focused library was developed for thiophenol species. Our studies show that CCP-1 displays a thiophenol-triggered 28-fold fluorescence intensity enhancement at 706 nm, with a detection limit of 34 n m observed. It is also able to differentiate thiophenols from various other thiol-containing analytes including hydrogen sulfide, hydrogen persulfide, and aliphatic thiols. In total, the desirable properties (e.g., excitation/emission in the NIR region, good cell-membrane permeability, intracellular stability, and low cytotoxicity) make CCP-1 a potential candidate for thiophenol detection both in vitro and in vivo. In addition, CCP-1, for the first time, successfully visualized thiophenols in mice models of thiophenol inhalation. [ABSTRACT FROM AUTHOR]

The combination of nanostructures with biomolecules leading to the generation of functional nanosystems holds great promise for biotechnological and biomedical applications. As a naturally occurring biomacromolecule, DNA exhibits excellent biocompatibility and programmability. Also, scalable synthesis can be readily realized through automated instruments. Such unique properties, together with Watson–Crick base-pairing interactions, make DNA a particularly promising candidate to be used as a building block material for a wide variety of nanostructures. In the past few decades, various DNA nanostructures have been developed, including one-, two- and three-dimensional nanomaterials. Aptamers are single-stranded DNA or RNA molecules selected by Systematic Evolution of Ligands by Exponential Enrichment (SELEX), with specific recognition abilities to their targets. Therefore, integrating aptamers into DNA nanostructures results in powerful tools for biosensing and bioimaging applications. Furthermore, owing to their high loading capability, aptamer-modified DNA nanostructures have also been altered to play the role of drug nanocarriers for in vivo applications and targeted cancer therapy. In this review, we summarize recent progress in the design of aptamers and related DNA molecule-integrated DNA nanostructures as well as their applications in biosensing, bioimaging and cancer therapy. To begin with, we first introduce the SELEX technology. Subsequently, the methodologies for the preparation of aptamer-integrated DNA nanostructures are presented. Then, we highlight their applications in biosensing and bioimaging for various targets, as well as targeted cancer therapy applications. Finally, we discuss several challenges and further opportunities in this emerging field. [ABSTRACT FROM AUTHOR]

In this work we use a water-soluble cationic perylene derivative (compound 1) as the G-quadruplex (G4) structure fluorescence indicator to construct a fluorescent biosensor for simple, rapid and label-free detection of Pb 2+ . In the absence of Pb 2+ , strong electrostatic interactions between compound 1 and the G-rich DNA probe (PW17) induced the aggregation of compound 1 and resulted in the fluorescence quenching. In the presence of Pb 2+ , the PW17 formed Pb 2+ -stabilized G4 structure, which reduced the aggregation of compound 1 and gave rise to high fluorescence. This allowed us to use convenient “mix-and-detect” protocol for quantitative analysis of Pb 2+ . Since Pb 2+ can specially induce PW17 to form compact DNA fold, our proposed biosensor displayed high selectivity for Pb 2+ . It also exhibited a high sensitivity to Pb 2+ , with a limit of detection of 5.0 nM observed. Furthermore, the biosensor was applied for the detection of Pb 2+ in urine and paint samples, and both showed satisfactory results. [ABSTRACT FROM AUTHOR]

DNAzyme-based catalytic beacons have been widely studied for both in vivo and in vitro molecular detection. However, only a few label-free catalytic beacons with excellent analytical performance have been reported so far. In this work, by combining a catalytic DNAzyme for amplified sensing through enzymatic turnover with cleavage-induced G-quadruplex formation, a label-free DNAzyme biosensor was developed for amplified “turn-on” fluorescence detection of Pb 2+ with a detection limit of 3 nM. The method is very competitive compared to many other labeled or label-free methods with or without signal amplification. Due to the inherent specificity of the GR-5 DNAzyme, the method also exhibits excellent selectivity. This biosensor successfully detected Pb 2+ in river water samples with high sensitivity and selectivity. Such a method might provide a universal DNAzyme-based sensing platform for sensitive detection of various targets both in environmental and biomedical fields. [ABSTRACT FROM AUTHOR]

By employing DNAzyme as a recognition group and amplifier, and DNA-stabilized silver nanoclusters (DNA/AgNCs) as signal reporters, we reported for the first time a label-free catalytic and molecular beacon as an amplified biosensing platform for highly selective detection of cofactors such as Pb2+ and l-histidine. [ABSTRACT FROM AUTHOR]

Abstract: In this work, by combining the enzymatic recycling reaction with the DNA functionalized gold nanoparticles (AuNPs)-based signal amplification, we have developed an electrochemical biosensor for label-free detection of DNA with high sensitivity and selectivity. In the new designed biosensor, a hairpin-structured probe HP was designed to hybridize with target DNA first, and an exonuclease ExoIII was chosen for the homogeneous enzymatic cleaving amplification. The hybridization of target DNA with the probe HP induced the partial cleavage of the probe HP by ExoIII to release the enzymatic products. The enzymatic products could then hybridize with the hairpin-structured capture probe CP modified on the electrode surface. Finally, DNA functionalized AuNPs was further employed to amplify the detection signal. Due to the capture of abundant methylene blue (MB) molecules by both the multiple DNAs modified on AuNPs surface and the hybridization product of capture DNA and enzymatic products, the designed biosensor achieved a high sensitivity for target DNA, and a detection limit of 0.6pM was obtained. Due to the employment of two hairpin-structured probes, HP and CP, the proposed biosensor also exhibited high selectivity to target DNA. Moreover, since ExoIII does not require specific recognition sequences, the proposed biosensor might provide a universal design strategy to construct DNA biosensor which can be applied in various biological and medical samples. [Copyright &y& Elsevier]

Abstract: The double-strand DNA (dsDNA) can act as an efficient template for the formation of copper nanoparticles (Cu NPs) with high fluorescence, whereas the single-strand DNA (ssDNA) cannot support the formation of Cu NPs. This difference in fluorescent signal generation can be used for the detection of nuclease cleavage activity. Thus, a label-free strategy for sensitive detection of nuclease has been developed. The sensor contains a complete complementary dsDNA which acts as a template for the formation of Cu NPs and generation of fluorescence signal. The enzyme S1 nuclease was taken as the model analyte. Upon addition of S1 nuclease into the sensing system, the DNA was cleaved into fragments, preventing the formation of the Cu NPs and resulting in low fluorescence. In order to achieve the system''s best sensing performance, a series of experimental conditions were optimized. Under the optimized experimental conditions, the sensor exhibits excellent performance (e.g., a detection limit of 0.3UmL−1 with high selectivity). This possibly makes it an attractive platform for the detection of S1 nuclease and other biomolecules. [Copyright &y& Elsevier]

Abstract: A nonenzymatic electrochemical biosensor was developed for the detection of glucose based on an electrode modified with palladium nanoparticles (PdNPs)-functioned graphene (nafion–graphene). The palladium nanoparticle–graphene nanohybrids were synthesized using an in situ reduction process. Nafion–graphene was first assembled onto an electrode to chemically adsorb Pd2+. And Pd2+ was subsequently reduced by hydrazine hydrate to form PdNPs in situ. Such a PdNPs–graphene nanohybrids-based electrode shows a very high electrochemical activity for electrocatalytic oxidation of glucose in alkaline medium. The proposed biosensor can be applied to the quantification of glucose with a wide linear range covering from 10μM to 5mM (R =0.998) with a low detection limit of 1μM. The experiment results also showed that the sensor exhibits good reproducibility and long-term stability, as well as high selectivity with no interference from other potential competing species. [Copyright &y& Elsevier]

Abstract: Highly ordered Ni nanowire arrays (NiNWAs) were synthesized for the first time using a template-directed electropolymerization strategy with a nanopore polycarbonate (PC) membrane template, and their morphological characterization were examined by scanning electron microscopy (SEM) and transmission electron microscope (TEM). A NiNWAs based electrode shows very high electrochemical activity for electrocatalytic oxidation of glucose in alkaline medium, which has been utilized as the basis of the fabrication of a nonenzymatic biosensor for electrochemical detection of glucose. The biosensor can be applied to the quantification of glucose with a linear range covering from 5.0×10−7 to 7.0×10−3 M, a high sensitivity of 1043μAmM−1 cm−2, and a low detection limit of 1×10−7 M. The experiment results also showed that the sensor exhibits good reproducibility and long-term stability, as well as high selectivity with no interference from other oxidable species. [Copyright &y& Elsevier]

Abstract: A successively signal-amplified electrochemical immunoassay has been reported on the basis of the biocatalytic deposition of silver nanoparticles with their subsequent enlargement by nanoparticle-promoted catalytic precipitation of silver from the silver-enhancer solution. The immunoassay was carried out based on a heterogeneous sandwich procedure using polystyrene microwells to immobilize antibody. After all the processes comprising the formation of immunocomplex, biocatalytic deposition of silver nanoparticles and following silver enhancement were completed, the silver on polystyrene microwells was dissolved and quantified by anodic stripping voltammetry (ASV). The effect of relevant experimental conditions, including the concentration of ascorbic acid 2-phosphate (AA-p) substrate and Ag(I) ions, the biocatalytic deposition time, and of crucial importance, the silver enhancement time, were investigated and optimized. The anodic stripping peak current was proportional to the concentration of human IgG in a dynamic range of 0.1–10ngml−1 with a detection limit of 0.03ngml−1. Scanning electron microscope (SEM) was applied to characterize the silver nanoparticles before and after silver enhancement on the surface of polystyrene microplates. By coupling the highly catalytic effect of enzyme and nanoparticles to successively amplify the analytical signal, the sensitivity of immunoassay was enhanced so dramatically that this approach would be a promising strategy to achieve a lower detection limit for bioassays. [Copyright &y& Elsevier]

Abstract: By grafting with poly(amidoamine) (PAMAM) dendrimer, novel carbon nanotube (CNT) nano-composites have been successfully prepared. The novel functionalized matrix with plenty amino groups circumvents the troublesome solubility problem of CNTs in solvents, especially in water, greatly expanding the scope of the application of carbon nanotubes. The GO x and HRP immobilized CNT-PAMAM based on the functional CNTs was synthesized. The bi-enzymatic CNT-PAMAM nano-composites are highly dispersible in water and show very promising applications in the fabrication of mediator-free bi-enzymatic biosensors for sensitive detection of glucose. The cooperation of nano-composite between CNT and high dense GO x and HRP results in very high sensitivity to glucose with a current response of 2200nAmM−1 and fast response (∼1s). The modified electrode exhibits a wide linear response range for glucose from 4.0μM to 1.2mM (R =0.9971, N =15), with a detection limit of 2.5μM. The negative electrode potential of −0.34V is favorable for glucose detection in real samples without interference caused by other biomolecules. [Copyright &y& Elsevier]

Taking advantage of the super-quenching effect of the cationic perylene derivative on adjacent fluorophores, we for the first time reported a DNAzyme–perylene complex-based strategy for constructing fluorescence catalytic biosensors with improved sensitivity. [ABSTRACT FROM AUTHOR]

The use of a nanoscale DNA–Au dendrimer as a signal amplifier was proposed for the universal design of functional DNA-based ultra-sensitive SERS biosensors. This novel design combines the high specificity of functional DNA with the high sensitivity of surface-enhanced Raman scattering (SERS) spectroscopy, resulting in sensitivity superior to that of previously reported sensors. [ABSTRACT FROM AUTHOR]

Review: 150 refs. [ABSTRACT FROM AUTHOR]

Review: 132 refs. [ABSTRACT FROM AUTHOR]