A simple yet highly sensitive and selective aptasensor architecture for rapid and portable miRNA detection

Electrochemical aptasensors are a versatile tool for detecting miRNA biomarkers associated with several diseases. However, most aptasensors require complex surface and probe modifications to achieve sufficiently high sensitivity and selectivity. Here, we introduce a simple yet ultrasensitive electrochemical aptasensor architecture for the rapid and portable detection of miRNA over a broad linear range of 109 orders of magnitude in concentration with a low limit of detection of 0.28 aM. We demonstrate sensing of miR-124 as a representative biomarker in light of its association with retinal diseases and in particular age-related macular degeneration. Unlike most of the existing miRNA biosensors, we use a short capture probe and establish a dual passivation and equilibration strategy of the biosensor surface before target miRNA sensing. This approach results in high sensitivity, selectivity, and reproducibility, minimizing cross-sensitivity to other miRNAs such as miR-155, miR-182, miR-183 and a scrambled miRNA sequence. The analytical utility of our aptasensor architecture is validated in mouse serum indicating immediate potential for clinical applications such as macular degeneration screening. Overall, these insights on the engineering of reproducible and stable electrochemical surfaces for miRNA detection provide directions for the design of a family of small footprint miRNA sensing devices.