Dual signal amplification via ATRP and ROMP for ultra-sensitive detection of miRNA-21.

The creation of a highly sensitive and practical assay for the early detection of lung cancer through miRNA-21 quantification is of considerable importance for the proactive management of this disease. Herein, we describe the design of an innovative electrochemical biosensor for ultrasensitive detection of miRNA-21, via atom transfer radical polymerization (ATRP) and ring opening metathesis polymerization (ROMP) dual signal amplification. The biosensor functions through the sequence-specific hybridization of a peptide nucleic acid probe with target miRNA-21 on a gold electrode, providing the recognition foundation for signal generation. This hybridization event initiates a sequential dual amplification process in which ATRP is first employed to grow dense polyacrylate brushes from the hybridized sites, creating a high-capacity scaffold. Subsequently, ROMP is utilized to graft a large number of ferrocene-labeled units onto these brushes, thereby dramatically enhancing the electrochemical signal. Under the optimized experimental conditions, the developed biosensor demonstrated exceptional analytical performance, with a linear detection range of 1 aM-100 pM and a strong correlation (R = 0.993). Crucially, an ultrasensitive limit of detection of 0.136 aM was achieved. Furthermore, the biosensor demonstrated robust selectivity against mismatched and non-target RNA sequences and maintained high performance in complex serum samples, highlighting its anti-interference capabilities. This enzyme-free, highly sensitive, and selective platform for miRNA-21 quantification holds significant potential for early-stage cancer diagnostics, therapeutic monitoring, and can be further applied to the detection of diverse critical biomarkers, offering a promising avenue for advanced clinical applications.