Smart biocathodic double signal amplification design empowered self-powered bioplatform ultrasensitive detection of tumor biomarker

MicroRNA-21 (miRNA-21) is widely expressed in various organs and tissues of mammals, including the heart, lungs, brain, pancreas, small intestine, colon, breast, and kidneys, showing high sensitivity and specificity in the diagnosis of multiple types of tumors. It can serve as a new clinical early diagnosis and prognostic biomarker for tumors. This study proposes a self-powered bioplatform, which employs a biological cathode double signal amplification design to construct a high-performance enzyme biofuel cell for the ultra-sensitive detection of tumor biomarker miRNA-21. The biocathodic double signal mechanism involves the catalyzed hairpin selfassembly introduction signal I bilirubin oxidase and a tetrahedral DNA nanostructure that produces a doublehelical DNA chain to adsorb signal II electron acceptor [Ru(NH3)6]3+. This approach not only improves the stability of the sensing system, but also synergistically enhances the open circuit voltage. The developed assay exhibits a wide linear range from 0.1 fM to 1000 pM, with a low detection limit of 0.04 fM (S/N = 3). This study provides a strategy for designing biosensors with improved sensitivity and potential application in medical diagnosis field.