Dual-layer 3D DNA nanostructure: The next generation of ultrafast DNA nanomachine for microRNA sensing and intracellular imaging

A ratiometric SERS aptasensor based on catalytic hairpin self-assembly mediated cyclic signal amplification strategy for the reliable determination of E. coli O157:H7

A ratiometric SERS aptasensor based on catalytic hairpin self-assembly (CHA) mediated cyclic signal amplification strategy was developed for the rapid and reliable determination of Escherichia coli O157:H7. The recognition probe was synthesized by modifying magnetic beads with blocked aptamers, and the SERS probe was constructed by functionalizing gold nanoparticles (Au NPs) with hairpin structured DNA and 4-mercaptobenzonitrile (4-MBN). The recognition probe captured E. coli O157:H7 specifically and released the blocker DNA, which activated the CHA reaction on the SERS probe and turned on the SERS signal of 6-carboxyl-x-rhodamine (ROX). Meanwhile, 4-MBN was used as an internal reference to calibrate the matrix interference. Thus, sensitive and reliable determination and quantification of E. coli O157:H7 was established using the ratio of the SERS signal intensities of ROX to 4-MBN. This aptasensor enabled detection of 2.44 × 102 CFU/mL of E. coli O157:H7 in approximately 3 h without pre-culture and DNA extraction. In addition, good reliability and excellent reproducibility were observed for the determination of E. coli O157:H7 in spiked water and milk samples. This study offered a new solution for the design of rapid, sensitive, and reliable SERS aptasensors.

DNA-Based Molecular Machines: Controlling Mechanisms and Biosensing Applications

The rise of DNA nanotechnology has driven the development of DNA-based molecular machines, which are capable of performing specific operations and tasks at the nanoscale. Benefitting from the programmability of DNA molecules and the predictability of DNA hybridization and strand displacement, DNA-based molecular machines can be designed with various structures and dynamic behaviors and have been implemented for wide applications in the field of biosensing due to their unique advantages. This review summarizes the reported controlling mechanisms of DNA-based molecular machines and introduces biosensing applications of DNA-based molecular machines in amplified detection, multiplex detection, real-time monitoring, spatial recognition detection, and single-molecule detection of biomarkers. The challenges and future directions of DNA-based molecular machines in biosensing are also discussed.

Strand displacement amplification triggered 3D DNA roller assisted CRISPR/Cas12a electrochemiluminescence cascaded signal amplification for sensitive detection of Ec-16S rDNA

BACKGROUND

Escherichia coli can cause gastrointestinal infection, urinary tract infection and other infectious diseases. Accurate detection of Escherichia coli 16S rDNA (Ec-16S rDNA) in clinical practice is of great significance for the identification and treatment of related diseases. At present, there are various types of sensors that can achieve accurate detection of Ec-16S rDNA. Electrochemiluminescence (ECL) has attracted considerable attention from researchers, which causes excellent performance in bioanalysis. Based on the previous research, it is significance to develop a novel, sensitive and efficient ECL biosensor.

RESULTS

In this work, an ECL biosensor for the detection of Ec-16S rDNA was constructed by integrating CRISPR/Cas12a technology with the cascade signal amplification strategy consisting of strand displacement amplification (SDA) and dual-particle three-dimensional (3D) DNA rollers. The amplification products of SDA triggered the operation of the DNA rollers, and the products generated by the DNA rollers activated CRISPR/Cas12a to cleave the signal probe, thereby realizing the change of the ECL signal. The cascade amplification strategy realized the exponential amplification of the target signal and greatly improved the sensitivity. Manganese dioxide nanoflowers (MnO2 NFs) as a co-reaction promoter effectively enhanced the ECL intensity of tin disulfide quantum dots (SnS2 QDs). A new ternary ECL system (SnS2 QDs/S2O82-/MnO2 NFs) was prepared, which made the change of ECL intensity of biosensor more significant. The proposed biosensor had a response range of 100 aM-10 nM and a detection limit of 27.29 aM (S/N = 3).

SIGNIFICANCE AND NOVELTY

Herein, the cascade signal amplification strategy formed by SDA and dual-particle 3D DNA rollers enabled the ECL biosensor to have high sensitivity and low detection limit. At the same time, the cascade signal amplification strategy was integrated with CRISPR/Cas12a to enable the biosensor to efficiently detect the target. It can provide a new idea for the detection of Ec-16S rDNA in disease diagnosis and clinical analysis.