Dual-catalytic hairpin amplification strategy as a highly efficient signal amplifier cooperative with COF@Au for ultrasensitive SERS detection of miRNA-21.

BACKGROUND

MicroRNAs (miRNAs) are crucial biomarkers for early disease diagnosis, but their low abundance in biological samples poses a significant challenge for detection. Surface-enhanced Raman scattering (SERS) biosensors have emerged as a powerful tool for ultrasensitive miRNA detection due to their high sensitivity. However, achieving rapid and efficient signal amplification remains a critical hurdle. Herein, a novel dual-catalytic hairpin amplification (D-CHA) strategy is introduced, combined with gold nanoparticle-doped covalent organic frameworks (COF@Au), to develop an advanced SERS biosensor. This approach creates a robust platform for miRNA-21 detection with enhanced Raman signals.

RESULTS

The proposed SERS biosensor integrates the D-CHA strategy with COF@Au to achieve ultrasensitive miRNA-21 detection. Unlike conventional CHA, D-CHA introduces an additional hairpin DNA (Hp1), enabling simultaneous release of Hp1 and target miRNA-21 to participate in subsequent amplification cycles. This design significantly improves signal amplification efficiency, achieving rapid detection within 20 min. The COF@Au substrate, with its high surface area and uniform Au NP distribution, provides strong and consistent Raman enhancement. Upon target binding, the hairpin DNA opens, triggering D-CHA and facilitating the attachment of SERS tags to COF@Au. Furthermore, the multi-gap structure of Au nanoflowers (Au NFs) generates multiple SERS "hot spots," amplifying the local electromagnetic field and synergistically enhancing the Raman signal of 4-nitrothiophenol (4-NTP). The biosensor demonstrates exceptional sensitivity, with a detection limit of 3.96 × 10 mol/L, and operates under a "signal-on" strategy, ensuring high specificity and reliability.

SIGNIFICANCE

This study presents a groundbreaking SERS biosensor that combines D-CHA signal amplification with COF@Au substrates for ultrasensitive miRNA-21 detection. The innovative D-CHA strategy significantly enhances amplification efficiency, while the COF@Au platform provides robust Raman enhancement. The biosensor's ability to achieve rapid and sensitive detection of miRNA-21 at ultralow concentrations opens new avenues for early disease diagnosis and biomedical research. This work provides a new way for sensitive and rapid detection of various biomarkers.