Simultaneous detection of exosomal microRNAs by nucleic acid functionalized disposable paper-based sensors

Compared with free microRNAs (miRNAs) in blood, miRNAs in exosomes are more abundant and stable. However, simple, reliable and simultaneous detection of exosomal microRNAs remains a challenging. In this study, we proposed a disposable paper-based electrochemical strategy based on nucleic acid functionalized Zr-MOF, which is label-free and enzyme-free, and could simultaneously detect multiple tumor exosomal miRNAs. We constructed a functionalized metal–organic framework (MOF) with electroactive dyes and capped it with hairpin DNA. This proposed bio-platform and MOF can display different electrochemical signals for different target analyses by changing the structures of dye-loaded and hairpin DNA. In view of this, we skill fully designed two kinds of functional MOFs (Zr/MB and Zr/BG) and used them to simultaneously detect exosomal miRNA-155 and exosomal miRNA-21 (as proof-of-concept analysis). This robust biosensor eliminates multiple time-consuming steps associated with existing miRNAs quantification methods, such as reverse transcription and thermocycler amplification, and achieves molecular-level sensitivity to exosomal miRNA-155 (33.4 aM) and exosomal miRNA-21 (23.1 aM). This study combines the advantages of simultaneous biosensing, which disposable paper-based biosensing strategies and represents an important advance in the field of electrochemical analysis and provides unlimited possibilities for the development of flexible, easy-to-use, and inexpensive bioelectrodes.