Triple-Helix Molecular Switch Triggered Cleavage Effect of DNAzyme for Ultrasensitive Electrochemical Detection of Chloramphenicol

Abstract

The abuse of chloramphenicol (CAP) in animal-derived products leads to serious food safety problems, so the sensitive and accurate determination of CAP residues has great noteworthiness for public health. Herein, we present a novel electrochemical aptasensor that incorporates a poly­(diallyldimethylammonium chloride) functionalized graphene/Ag@Au nanosheets (PDDA-Gr/Ag@Au NSs) composite modified electrode and a DNAzyme signal amplification effect triggered by a triple-helix molecular switch (THMS) for detecting CAP. The PDDA-Gr/Ag@Au NSs composite has the advantages of high surface area, great conductivity, and dispersibility and has successfully improved the electrochemical performance of the electrode. Specific interaction with CAP will cause the signal transduction probe (STP) to be released from the THMS. After that, the DNAzyme will be activated with the help of Pb2+ and remove the immobilized signal probe on the electrode surface. The signal change was recorded by square wave voltammetry (SWV) and led to an accurate quantification of CAP. With all these features, the proposed sensing strategy yielded a satisfactory analytical performance with linearity between 1 pM and 1 μM and a limit of detection of 18.6 fM. Furthermore, the aptasensor shows excellent specificity for CAP in the presence of other antibiotics and resists interference with other common metal ions. Importantly, the performance is not diminished when the constructed aptasensor is applied to measuring CAP in milk powder. This THMS-based method is easy to design, and alteration to different targets can be achieved by simply replacing the aptamer sequence in the THMS. Therefore, this method shows significant prospects as a flexible platform for accurate monitoring of antibiotic residues in foodstuffs.

Lowering Entropic Barriers in Triplex DNA Switches Facilitating Biomedical Applications at Physiological pH

“…[10,12] Moreover, even slight variations within homopurine tracts tend to destabilize triplex motifs. [33] This limitation hinders their practical applications, especially when applying the triplex-based switches for mRNA silencing or delivering functional nucleic acids into cells, [27] since not all target RNAs or functional nucleic acids have polypurine sequences like SFO does. Inspired by the results revealed in Figure S2, we wondered whether the sequence restriction could be alleviated by the CTNS ds design.…”

“…[8,24] However, this approach is usually ineffective in dynamic biological systems. Substitution of CÀ G • C + triads with TÀ A • T triads in triple-helices can also facilitate triplex formation at physiological pH, [6,25] but it is not applicable when the sequence of a homopurine strand cannot be altered, for example, an mRNA, [3,26] an microRNA, [27] or a DNAzyme. [28] Therefore, there is a significant need for a simple and general approach to enhance triplex-forming capacity.…”

Wavelength-Dependent, Orthogonal Photoregulation of DNA Liberation for Logic Operations

“…This would result in structural transition of the DNA switch from triple to duplex conformations to inhibit the strand displacement process. More recently, researchers have put much effort on the light-activated DNA nanodevices to move forward for applications in cellular environments. , These photochemical stimuli could generally narrow the gap between silicon-based circuits and DNA-based logic devices using light to precisely control logic functions. However, the reported photochemical control of oligonucleotide activities is highly restricted to the use of single wavelength of light irradiation at 365 nm for UV-induced structural transformation or bond cleavage of caging molecules.…”

A Signal-Enhanced Regenerative Electrochemical Aptasensor for Amyloid-β Oligomers Based on Triple-Helix Aptamer Probe

“…A more stable and flexible triple-helix Apt probe (TAP) is an effective alternative of traditional sandwich sensing strategy. 38,39 For the past few years, based on Hoogsteen hydrogen bonds and Watson-Crick base pairing, TAP has been widely applied to EA, [40][41][42] characterized with the excellent performance and especial structure. With Apt sequence as loop and two short double-stranded DNA as stem, 43 TAP has several advantages over conventional double-helix aptamer probe (DAP).…”