Enzyme-free amplification for sensitive electrochemical detection of DNA via target-catalyzed hairpin assembly assisted current change

Ultrasensitive Aptasensor for Microcystin-LR Detection in Food Samples Based on Target-Activated Assembly of Y-Shaped Hairpin Probes

As a kind of algal toxin, microcystin-LR (MC-LR) causes a tremendous treat to food safety and the detection of trace levels of MC-LR is highly desirable. Herein, we developed an ultrasensitive aptasensor for MC-LR detection based on target-activated assembly of Y-shaped hairpins. The aptamer-target recognition initiates the assembly step between two Y-shaped hairpin probes through toehold-mediated DNA replacement. One of the hairpins was modified with FAM and BHQ. Through cyclic assembly reactions, a high fluorescence signal can be observed in the product. The detection limit is 0.2 pM for MC-LR detection. In addition, the biosensor is robust and has been successfully explored to assess the MC-LR concentrations in real fish and water samples with satisfactory recovery rates and good accuracy. The signal amplification can be gained through the cyclic Y-shaped hairpin assembly, which offers a simple, ultrasensitive, and reliable method for MC-LR monitoring in food samples.

Carbon Dots/α-Fe2O3-Fe3O4 nanocomposite: Efficient synthesis and application as a novel electrochemical aptasensor for the ultrasensitive determination of aflatoxin B1

Developing an effective method for the detection of aflatoxin B1 (AFB1) remains an arduous task due to the high toxicity of AFB1 to a health concern. In this study, a sensitive and reliable electrochemical aptasensor based on carbon dots/α-Fe₂O₃-Fe₃O₄ nanocomposite (CDs/α-Fe₂O₃-Fe₃O₄) is constructed for the determination of AFB1. The CDs have good electrical conductivity and large specific surface areas to improve the aptasensor's sensitivity. The α-Fe₂O₃-Fe₃O₄ can not only improve the catalytic performance of the aptasensor but also have magnetism, which can realize the recovery of CDs/α-Fe₂O₃-Fe₃O₄ to avoid material waste and environmental pollution. This electrochemical aptasensor can achieve a good linear (0.001-100.0 nM) and excellent detection limit (0.5 pM) for the determination of AFB1. In addition, the aptasensor was also applied to determine AFB1 in beer, rice, and peanuts, all results were in good agreement with HPLC, indicating that the electrochemical aptasensor has a broad application prospect.

Application of peptide nucleic acid in electrochemical nucleic acid biosensors

The early diagnosis of major diseases, such as malignant tumors, has always been an important field of research. Through screening, early detection of such diseases, and timely and effective treatment can significantly improve the survival rate of patients and reduce medical costs. Therefore, the development of a simple detection method with high sensitivity and strong specificity, and that is low cost is of great significance for the diagnosis and prognosis of the disease. Electrochemical DNA biosensing analysis is a technology based on Watson Crick base complementary pairing, which uses the capture probe of a known sequence to specifically recognize the target DNA and detect its concentration. Because of its advantages of low cost, simple operation, portability, and easy miniaturization, it has been widely researched and has become a cutting-edge topic in the field of biochemical analysis and precision medicine. However, the existing methods for electrochemical DNA biosensing analysis have some shortcomings, such as poor stability and specificity of capture probes, insufficient detection sensitivity, and long detection cycles. In this review, we focus on improving the sensitivity and practicability of electrochemical DNA biosensing analysis methods and summarize a series of research work carried out by using electrically neutral peptide nucleic acid as an immobilized capture probe.

An in situ assembly strategy for the construction of a sensitive and reusable electrochemical aptasensor

In situ assembly of an electroactive AuNPs–Cu²⁺–l-cysteine tag was applied for the construction of a sensitive and reusable aptasensor.

Toehold integrated molecular beacon system for a versatile non-enzymatic application

A molecular beacon (MB) is an oligonucleotide hybridization probe with a hairpin-shaped structure that leads to specific and instantaneous nucleic acid hybridization, enabling a variety of applications. However, integration of additional module sequences interferes with the performance of MBs and increases the complexity of sequence design. Herein, we develop and characterize a toehold integrated molecular beacon (ToMB) strategy for nucleic acid hybridization, where the reaction rate can be flexibly regulated by a target-induced MB conformational switch. Using this basic mechanism, the ToMB is capable of identifying nucleic acids with high specificity and a wider linearity range compared with the conventional molecular beacon system. We further applied the ToMB to the construction of a hybridization chain reaction system and a basic OR logic gate VJHto explore its programmability and versatility. Our results strongly suggest that the novel ToMB can act as a powerful nano-module to construct universal and multifunctional biosensors or molecular computations. Graphical abstract Molecular beacon is employed as a flexible and switchable spacer to control the toehold-mediated strand displacement reaction.

Single electrode biosensor for simultaneous determination of interferon gamma and lysozyme

Simultaneous detection of multiple biomarkers holds great promise for acute leukemia evaluation. Here, a novel biosensor is developed for simultaneous electrochemical detection of interferon gamma (IFN-γ) and lysozyme (Lys) based on aptamer recognition by coupling "signal-on" and "signal-off" modes. On one Au electrode, two kinds of signaling probes labeled by the thiolated ferrocene (Fc)- and methy blue (MB)- were designed to hybridize with IFN-γ and Lys aptamers respectively to form partial complementary DNA duplexes. In the presence of IFN-γ and Lys, the target-aptamer interaction led to the release of aptamer from duplex DNA structure. The single-stranded signaling probes thus suffered from the conformation changes, which resulted in the decreased (or increased) oxidation peak current of Fc (or MB) according to the "signal-off (or signal-on)" mode. Electrodes were characterized using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Under the optimized conditions, the signal changes were quantified using square wave voltammetry (SWV). This proposed biosensor for IFN-γ and Lys possessed linear detection range from 0.01 to 10 nM and 0.1 to 100 nM, with the detection limits of 1.14×10(-3) nM and 0.0164 nM, respectively. Moreover, this biosensor was readily regenerated and proved successful toward the practical analysis. The proposed strategy could provide more integrated and reliable information for acute leukemia evaluation.