Catalytic Hairpin Self-Assembly-Based SERS Sensor Array for the Simultaneous Measurement of Multiple Cancer-Associated miRNAs

The abnormal expression of some miRNAs is often closely related to the development of tumors. Available detection methods or biosensors that can simultaneously quantify multiple miRNAs in a single sample have rarely been reported. Herein, a novel catalytic hairpin self-assembly (CHA)-based surface-enhanced Raman scattering (SERS) sensor array was developed to simultaneously measure multiple miRNAs associated with cancer in one sample. The sensor array with four different sensing units was constructed by immobilizing one of four different hairpin-structured DNA sequence 1 (hp1) onto one of four Au/Ag alloy nanoparticle (AuAgNP)-coated detection wells. When target miRNA is present, the SERS tags, which were prepared by modifying AuAgNPs with a Raman reporter molecule of 4-mercaptobenzonitrile (MPBN) and the related hairpin-structured DNA sequence 2 (hp2), were captured onto the corresponding sensor unit through a repeated specific CHA reaction. This generated many "hot spots" because of interactions between the SERS tags and the AuAgNP layer-coated surface of the sensor, which ultimately produced a strong SERS signal that allowed the detection of target miRNAs with the detection limit of 0.15 pM. Using this SERS sensor array, multiple cancer-associated miRNAs (miR-1246, miR-221, miR-133a, and miR-21) were successfully determined in buffer, serum, and cellular RNA extracts.