Evaluating Hybridization Chain Reaction to Improve miRNA Measurements at Portable Electroanalytical Strip: miRNA-21 as a Case of Study

This work reports on the evaluation of the hybridization chain reaction recognition system to be combined with a frugal sensing platform, namely screen-printed electrode, for the measurement and the amplification of circulating nucleic acids, without the use of time-consuming and complex procedures. In fact, if traditional strategies usually rely on nanomaterials or intricate modifications, our method places the target sequence and hairpins directly on the electrode surface, reducing both cost and preparation time while maintaining efficient signal amplification. Two specific DNA-based hairpins, modified with methylene blue as a redox mediator, has been rationally designed and characterized, yielding a "signal-off" response triggered by the presence of miRNA target. The system has been applied toward both standard and human serum samples, obtaining satisfactory detection limit of ca. 100 pM, with a repeatability less than 10%. This platform does not require modification and/or complex work flow, it offers a cost-effective, sensitive, and decentralized solution for point-of-care diagnostics and real-time miRNA monitoring in clinical settings, not only for cancer monitoring.