Ultrasensitive and specific microRNA detection via dynamic light scattering of DNA network based on rolling circle amplification

In this paper, rolling circle amplification (RCA)-based self-assembly DNA network was developed for ultrasensitive and specific detection of microRNA (miRNA) with dynamic light scattering (DLS) technology. A dumbbell-shaped padlock probe was designed, which could be connected with itself as a template under the action of T4 DNA ligase to form a dumbbell-shaped sealed probe. In the presence of the target miRNA, the miRNA bound to the toehold domain of the sealed probe. The sealed probe was activated into a circular probe to start RCA reaction by a spontaneous chain displacement reaction. The DNA functionalized AuNPs probe was hybridized with the RCA products to form RCA-DNA-AuNPs polymer with network, whose diameter was measured by DLS. Not only did this method greatly improve the sensitivity of detection, but the specificity of detection increased by using sealed probe as well. The limit of detection (LOD) was 0.11 fM. Furthermore, this strategy has been successfully used to analyze target miRNA in cancer cell samples, which confirmed that RCA-DLS analysis has broad application prospects in early clinical diagnosis.