Three-dimensional hierarchical plasmonic nano-architecture based label-free surface-enhanced Raman spectroscopy detection of urinary exosomal miRNA for clinical diagnosis of prostate cancer

The urinary exosomal miRNAs are recently emerging prostate cancer (PC)-associated biomarkers for the early-stage diagnosis and prognosis due to their non-invasiveness, inherent stability and the representation of the status of the originated cells. However, developing a urinary exosomal miRNA detection method with high accuracy is challenging because of the low abundance and high sequence homology of miRNAs. Herein, we present a quantitative and label-free miRNA sensing platform using surface-enhanced Raman scattering (SERS) based on three-dimensional (3D) hierarchical plasmonic nano-architecture to detect urinary exosomal miRNAs. This hierarchical nanostructure is constructed by self-assembly between target-complementary DNA probes-conjugated gold nanoparticles and head-flocked gold nanopillars in the presence of the target miRNAs, creating numerous 3D plasmonic hot-spots inducing exceedingly high amplification of SERS signals. This 3D SERS biosensor achieved ∼10 aM detection limits for the target miRNAs (miR-10a and miR-21), which is over 1000-fold more sensitive than previously reported miRNA sensors without the requirement of any labelling or pre-treatment steps. Finally, the clinical validation using urinary samples revealed that our 3D SERS sensor discriminates PC patients from healthy control with high diagnostic accuracy (0.93) based on the differential expression level of urinary exosomal miRNAs. These outputs demonstrate that our SERS sensor based on 3D hierarchical nano-architecture can offer facile, accurate and rapid methods to measure miRNA expression and is helpful for the diagnosis of various diseases.