miRNA Detection on Printed Electrochemical Strips Empowered by Hybridization Chain Reaction

Printed electrochemical strips are increasingly used in nucleic acid diagnostics due to their affordability portability, compactness, and ease of use. To respond to traditional electrochemical methods that require complex immobilization protocols, in this study, we introduce a simplified platform that combines a cost-effective electrode printed on a polyester substrate with a hybridization chain reaction (HCR) for DNA signal amplification. Unlike prior approaches that 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. Using DNA modified with methylene blue (MB) as a redox mediator, the system generates a "signal-off" response by suppressing electron transfer when MB intercalates into the DNA polymers formed by HCR. This approach eliminates the need for complex surface functionalization, enhancing ease of fabrication and consistency. Targeting miRNA-21, a known cancer biomarker, the sensor achieves picomolar sensitivity in both buffer and diluted human serum. This platform offers a cost-effective, sensitive, and portable solution for point-of-care diagnostics and real-time miRNA monitoring in clinical settings.