An NIR-driven biosensor based on the metal-enhanced fluorescence effect and a signal amplification strategy for miRNA detection

Research has shown that the expression level of microRNA-155 (miRNA-155) is positively correlated with clinical stage and depth of invasion in patients with cervical cancer and cervical intraepithelial neoplasia and tends to be highly expressed. Therefore, it is very important to develop sensitive miRNA-155 analysis methods for the early diagnosis, treatment, and prognostic evaluation of cervical cancer. In this study, a near-infrared light-driven fluorescent biosensor based on the metal-enhanced fluorescence effect of polydopamine-coated upconversion nanoparticle (UP/Au) and two toehold-mediated strand displacement (TMSD) steps was constructed for the detection of miRNA-155. The target miRNA-155 can undergo a TMSD1 reaction with single-stranded DNA1 (ssDNA1) modified on wrinkled silica (WSNs) to form the ssDNA1/miRNA-155 complex and expose toehold 2. Through the TMSD2 reaction, ssDNA2 adsorbed on the UP/Au surface reacts with ssDNA1 to form the ssDNA1/ssDNA2 complex, which replaces miRNA-155 and enables the recovery of the UP/Au fluorescence signal. The target miRNA-155 was reacted with the new ssDNA1 to amplify the detection signal, with a detection range of 0.5–20 pM and a detection limit of 19.76 fM for miRNA-155. In addition, the fluorescent biosensor has been applied for the analysis of miRNA-155 in serum samples, indicating its good practicality.