Molecular beacon decorated silver nanowires for quantitative miRNA detection by a SERS approach

Advantages of biosensors based on surface enhanced Raman scattering (SERS) rely on improved sensitivity and specificity, and suited reproducibility in detecting a target molecule that is localized in close proximity to a SERS-active surface. Herein, a comprehensive study on the realization of a SERS biosensor designed for detecting miRNA-183, a miRNA biomarker that is specific for chronic obstructive pulmonary disease (COPD), is presented. The used strategy exploits a signal-off mechanism by means of a labelled molecular beacon (MB) as the oligonucleotide biorecognition element immobilized on a 2D SERS substrate, based on spot-on silver nanowires (AgNWs) and a multi-well low volume cell. The MB was properly designed by following a dedicated protocol to recognize the chosen miRNA. A limit of detection down to femtomolar concentration (3 x 10-16 M) was achieved and the specificity of the biosensor was proved. Furthermore, the possibility to regenerate the sensing system through a simple procedure is shown: with regeneration by using HCl 1 mM, two detection cycles were performed with a good recovery of the initial MB signal (83%) and a reproducible signal after hybridization. To overcome the issues connected to the need of multiple steps in amplification methods for SERS biosensors, we propose a strategy for microRNA detection based on a signal-off mechanism of a labelled molecular beacon immobilized on the SERS substrate.

Automated summary

This paper presents a comprehensive study on the design and implementation of a SERS biosensor for detecting the specific miRNA biomarker miRNA-183 for COPD. By utilizing a labeled molecular beacon and a specially designed MB, the biosensor achieves high sensitivity and specificity in detecting target molecules at femtomolar concentrations, and the sensor's regenerability is also demonstrated.