Sensitive SERS detection of oral squamous cell carcinoma-related miRNAs in saliva via a gold nanohexagon array coupled with hybridization chain reaction amplification

In this work, a highly specific and sensitive method for the detection of dual miRNAs was successfully developed by a hybridization chain reaction (HCR) amplification coupled with surface-enhanced Raman scattering (SERS) on Au-Ag hollow nanoparticles (Au-Ag HNPs) and a gold nanohexagon (AuNH) array. Two Raman reporter-labelled and hairpin DNA-modified Au-Ag HNPs acted as SERS probes (Au-Ag HNPs@4-MBA@HP1-1, Au-Ag HNPs@4-MBA@HP2-1, Au-Ag HNPs@DTNB@HP1-2, and Au-Ag HNPs@DTNB@HP2-2), and the hairpin DNA-modified AuNH array acted as the capture substrate. The HCR process could be triggered by the presence of target miRNAs, and long DNA hybridization chains on the substrate were formed by self-assembly rapidly, causing significant signal enhancement. Using the mentioned strategy, a low detection limit (LOD) of 6.51 aM for miR-31 and 6.52 aM for miR-21 in human saliva were obtained, showing the biosensor's remarkable sensitivity. The proposed biosensor also displays a significant specificity in detecting target miRNAs by introducing different interfering factors. This method has been successfully applied to detect and identify miR-21 and miR-31 in saliva from oral squamous cell carcinoma (OSCC) patients and healthy subjects. The results were consistent with those of the traditional test method in detecting target miRNAs, which confirmed the good accuracy of our method. Hence, the new assay method has great potential to be a valuable platform for detecting miRNAs in the early diagnosis of OSCC.