Spherical nucleic acid nanoprobes for in situ and multiplex detection of exosomal PIWI-interacting RNAs

Abstract

PIWI-interacting RNAs (piRNAs) are a novel class of non-coding RNAs that bind specifically to the PIWI subfamily of Argonaut proteins. It has been increasingly demonstrated that piRNAs encased in circulating exosomes could be an ample source of potential tumor markers for cancer diagnostics. However, methods on exosomal piRNAs detections are limited, and most of them need extraction of piRNAs from the sample which is laborious and disadvantage to clinical applications. Herein, we developed two kinds of dual-targeted spherical nucleic acid nanoprobes for in situ and multiplex detection of exosomal piRNAs. The detection scheme was rationally designed for the large sized targets of PIWI-interacting RNA complex which could generate steric hindrance in the detection reaction. The probes were synthesized by modifying 13-nm gold particles with high-density double stranded anchor-report DNA through butanol dehydration method. The key synthesis condition of molar ratio between the two kinds of anchor-report DNA chains were optimized for preparing probes with good structural reproducibility. The probes can perform in situ and multiplex detection of piRNAs in exosomes after simple incubation. In the clinical assays of plasma from breast cancer patients and normal control groups, the probes can differentiate the expression levels of 3 types of piRNAs and their combinations in high specificity and sensitivity. These new piRNA probes are potentially to perform simple and accurate liquid biopsy for cancer diagnostics.