Dynamic DNA nanotechnology, a subfield of DNA nanotechnology, is concerned with the study and application of nucleic acid strand-displacement reactions. Strand-displacement reactions generally proceed by three-way or four-way branch migration and initially were investigated for their relevance to genetic recombination. Through the use of toeholds, which are single-stranded segments of DNA to which an invader strand can bind to initiate branch migration, the rate with which strand displacement reactions proceed can be varied by more than 6 orders of magnitude. In addition, the use of toeholds enables the construction of enzyme-free DNA reaction networks exhibiting complex dynamical behavior. A demonstration of this was provided in the year 2000, in which strand displacement reactions were employed to drive a DNA-based nanomachine (Yurke, B.; et al. Nature 2000, 406, 605–608). Since then, toehold-mediated strand displacement reactions have been used with ever increasing sophistication and the field of dynam...

Principles and Applications of Nucleic Acid Strand Displacement Reactions

Implications for management.

Progress on nanostructured electrochemical sensors and their recognition elements for detection of mycotoxins: A review.

Bimetallic cerium and ferric oxides nanoparticles embedded within mesoporous carbon matrix: Electrochemical immunosensor for sensitive detection of carbohydrate antigen 19-9.

This article provides a comprehensive review of biosensing with DNAzymes, providing an overview of different sensing applications while highlighting major progress and seminal contributions to the field of portable biosensor devices and point-of-care diagnostics. Specifically, the field of functional nucleic acids is introduced, with a specific focus on DNAzymes. The incorporation of DNAzymes into bioassays is then described, followed by a detailed overview of recent advances in the development of in vivo sensing platforms and portable sensors incorporating DNAzymes for molecular recognition. Finally, a critical perspective on the field, and a summary of where DNAzyme-based devices may make the biggest impact are provided.

Biosensing with DNAzymes

Electrochemical aptasensor for thrombin using co-catalysis of hemin/G-quadruplex DNAzyme and octahedral Cu 2 O-Au nanocomposites for signal amplification.

A signal-decreased electrochemical immunosensor for the sensitive detection of LAG-3 protein based on a hollow nanobox-MOFs/AuPt alloy.

Target-inspired Pb2+-dependent DNAzyme for ultrasensitive electrochemical sensor based on MoS2-AuPt nanocomposites and hemin/G-quadruplex DNAzyme as signal amplifier.

The authors describe an electrochemical immunoassay for ultrasensitive detection of the mycotoxin zearalenone (ZEA). A nanocomposite was prepared from carboxy-functionalized multi-walled carbon nanotubes and chitosan (cMWCNTs/Chit). The morphology and electrochemical performance of the materials was characterized by field-emission scanning electron microscopy, atomic force microscopy, differential pulse voltammetry, cyclic voltammetry, and electrochemical impedance spectroscopy. In this assay, ZEA–BSA conjugated covalently to activated cMWCNTs/Chit film, then the indirect competition between ZEA–BSA and free ZEA when immobilization of excess anti-ZEA. The secondary antibody is labeled with the enzyme alkaline phosphatase which can hydrolyze the substrate 1-naphthylphosphate to produce 1-naphthol which gives a stable and strong anodic electrochemical signal at a low working voltage of 0.3 V (vs. Ag/AgCl). The use of the modified GCE results in a strongly enhanced electrochemical current response. Compared with conventional methods, the established immunosensor exhibited a high level of sensitivity. Under optimal conditions, this immunoassay can quantify ZEA in the 10 pg·mL−1 to 1000 ng·mL−1 concentration range with a detection limit of 4.7 pg·mL−1 and the sensitivity is 0.51 μA·μM−1·cm−2. The method was applied to the determination of ZEA in cereal and feedstuff samples. Results showed satisfactory recovery and good consistency with high-performance liquid chromatography. Therefore, the indirect competitive electrochemical immunosensor provide a viable tool based on bioanalysis.

Electrochemical indirect competitive immunoassay for ultrasensitive detection of zearalenone based on a glassy carbon electrode modified with carboxylated multi-walled carbon nanotubes and chitosan

An ultrasensitive immunosensor for the direct detection of the illegally used livestock feed clebuterol (CLB) is described. It is based on the use of a glassy carbon electrode modified with an MoS2-AuPt nanocomposite and on biotin-streptavidin interaction. The use of MoS2-AuPt accelerates electron transfer, and this leads to a sharp increase in the electrochemical signal for the electrochemical probe hydrogen peroxide. Differential pulse voltammetry was used to record the current signal at a peak potential of −0.18 V (vs SCE). Under optimal conditions, the electrode has a linear response in the 10 pg·mL−1 to 100 ng·mL−1 CLB concentration range and a 6.9 pg·mL−1 detection limit (based on the 3σ criterium). This immunosensor is sensitive, highly specific and acceptably reproducible, and thus represents a valuable tool for the determination of CLB in pork.

Wei Xu

Papers

Electrochemical aptasensor for thrombin using co-catalysis of hemin/G-quadruplex DNAzyme and octahedral Cu 2 O-Au nanocomposites for signal amplification.

A signal-decreased electrochemical immunosensor for the sensitive detection of LAG-3 protein based on a hollow nanobox-MOFs/AuPt alloy.

Target-inspired Pb2+-dependent DNAzyme for ultrasensitive electrochemical sensor based on MoS2-AuPt nanocomposites and hemin/G-quadruplex DNAzyme as signal amplifier.

Electrochemical indirect competitive immunoassay for ultrasensitive detection of zearalenone based on a glassy carbon electrode modified with carboxylated multi-walled carbon nanotubes and chitosan

A voltammetric immunosensor for clenbuterol based on the use of a MoS 2 -AuPt nanocomposite