A DNAzyme-driven random biped DNA walking nanomachine for sensitive detection of uracil-DNA glycosylase activity

A novel nanoparticle surface-constrained CRISPR-Cas12a 3D DNA walker-like nanomachines for sensitive and stable miRNAs detection

The CRISPR-Cas system has broad prospects as a new type of nucleic acid signal amplification technology based on the trans-cleavage activity of Cas12a to single-stranded DNA, but the trans-cleavage reaction efficiency is relatively low in solution. In order to overcome this negative factor, a new 3D DNA nanomachine whose CRISPR-Cas12a is limited to the surface of nanoparticles is used for sensitive and stable detection of miRNA. By loading Cas12a activator onto spherical nucleic acid (SNA), the CRISPR-Cas12a activator system on the surface of Au nanoparticles (AuNPs) acts as a walker to carry out continuous recognition-walking-cutting reaction on the surface of AuNPs, which enhances the trans-cleavage activity of Cas12a to SNAs. Benefiting from the confinement effect of spherical nucleic acids surface, a 3D DNA nanomachine has been developed for the detection of miRNA-21, which has achieved high sensitivity and accuracy, and the detection limit is able to reach 8.0 pM. This new 3D DNA walker-like nanomachine provided another insight for future bioanalysis and early clinical diagnoses of disease and liquid biopsy.

DNA Dendrimer-Based Directed 3D Walking Nanomachine for the Sensitive Detection and Intracellular Imaging of miRNA

Taking advantage of the remarkable processivity and membrane penetrability, the gold nanoparticle (AuNP)-based three-dimensional (3D) DNA walking nanomachine has induced tremendous promise in molecular diagnostics and cancer therapy, whereas the executive ability of this nanomachine was eventually limited because of the disordered assembly between the walker and the track. Therefore, we developed a well-directed 3D DNA walking nanomachine by employing a DNA dendrimer as the track for intracellular imaging with high directionality and controllability. The nanomachine was constructed on a DNA dendrimer decorated with a substrate strand serving as the DNA track and a DNAzyme restrained by a locking strand as the walker. In this system, the distribution of the substrate strand and DNAzyme on the DNA dendrimer could be precisely regulated to achieve expected goals because of the specificity and predictability of the Watson-Crick base pairing, paving an explicit route for each walker to move along the track. Moreover, such a DNA dendrimer-based nanomachine owned prominent stability and anti-interference ability. By choosing microRNA-21 as a model analyte, the nanomachine was applied for the imaging of microRNA-21 in different cell lines and the monitoring of the dynamic microRNA-21 expression level in cancer cells. Therefore, we believe that this directed DNA walking nanomachine will have a variety of applications in molecular diagnostics and biological function modulation.

Target-manipulated drawstring DNAzyme for ultrasensitive detection of UDG using Au@Ag NRs indicator

Uracil-DNA glycosylase (UDG) is a common glycosylase that can expressly recognize and remove damaged uracil bases, and the ultrasensitive detection of which is significant to maintain genomic stability and early clinical diagnosis of disease. Herein, we proposed a sensitive colorimetric sensing platform to detect UDG. Combined with target-manipulated drawstring DNAzyme and Au@Ag nanorods (Au@Ag NRs) indicator, we achieved in naked-eyes observation and ultrasensitive detection of UDG. Briefly, when the UDG exists, the dynamic reaction of rope pulling will occur generating the active conformation of DNAzyme. The cutting effect will be further produced when we add Mg²⁺, thus the generated trigger chain can mediate the occurrence of CHA reaction, followed by generating amount of ·OH which can etch Au@Ag NRs causing the shifted of localized surface plasmon resonance (LSPR) peak. By contrast, there is no obvious shift of LSPR peak. This strategy shows extraordinary specificity and sensitivity toward UDG providing a detection limit of 4.6 × 10^-5 U mL^-1. By using of this method, we detected UDG specifically in complex samples, proving that it's potential applications in biomedical research and clinical diagnosis are fantastic.