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A dual-enzyme self-powered biosensor utilizing bimodal 3D DNA nanomachines and gold nanoparticle (AuNPs)/carbon/disulfide molybdenum hollow nanorods bioconjugates is developed for the electrochemical and visual detection of the tumor biomarker let-7a. DNA probes are immobilized on a flexible electrode substrate of AuNPs/graphdiyne/carbon cloth to improve probe loading capacity and electron transfer efficiency. The presence of let-7a initiates the work of dual-enzyme 3D DNA nanomachine, and the output DNA single strand cleaved by Nb.BbvCI is served as a bridge to connect glucose oxidase (GOD)-DNA conjugate. The GOD coordinates with the cathodic enzyme bilirubin oxidase and produces an increased open circuit voltage signal, which is attributed to the hexaammine ruthenium in the double-stranded adsorption system of the biocathode. By utilizing the H 2 O 2 generated during the oxidation process of GOD, a linear relationship between the color of 3,3′,5,5′-tetramethylbenzidine and the concentration of let-7a is established, enhancing the reliability of the detection results through the independent signal conversion mechanisms of electrochemical/colorimetric modes. The results demonstrate a wide dynamic range of 0.0001–0.1 pM with detection limits of 31.04 aM (S/N =3) in electrochemical mode and 59.99 aM (S/N =3) in the colorimetric mode. This dual-mode biosensing strategy can be expanded to detect additional nucleic acid biomarkers, providing a promising support and reference for biological analysis and medical diagnosis. • A dual-enzyme self-powered biosensor platform based on cathodic electron acceptors and bioconjugates has been developed. • The dual-mode detection of let-7a was achieved by utilizing the output of electrochemical and visual signals. • The platform exhibits high sensitivity, excellent selectivity, and high accuracy in the detection of let-7a. [ABSTRACT FROM AUTHOR]

MicroRNAs (miRNAs) are important cancer-associated biomarkers for early detection. However, accurately measuring miRNAs is challenging due to their low abundance and high homogeneity in human serum. CRISPR technology can greatly improve the specificity and sensitivity of detection in biosensor construction. In this study, we develop a remarkably responsive self-powered biosensing platform for detecting microRNA-21 (miRNA-21) using hybridization chain reaction (HCR) and CRISPR/Cas12a amplification cascade mediated by 3D DNA walkers. Carbon-coated molybdenum disulfide nanotubes with a large surface area and excellent conductivity are fabricated on flexible carbon paper as the anode and cathode for biological fuel cell construction. Glucose oxidase is loaded onto the anode surface, while serving as the biological cathode, it initiated HCR, generating abundant double-stranded DNA. The negatively charged DNA backbone captures electron acceptors [Ru(NH 3) 6 ]3+ through electrostatic adsorption, resulting in a significant open circuit voltage (E OCV ) signal. Through CRISPR/Cas12a amplification cascade mediated by 3D DNA walkers, a smaller E OCV is produced, enabling sensitive target detection. The method exhibits a detection range spanning from 0.0001 to 10,000 pM and capable of detecting as low as 19.0 aM (S/N = 3). This highly selective and sensitive method provides an effective approach for accurately detecting tumor markers in clinical applications. • HCR and 3D DNA Walker-mediated CRISPR/Cas12a cascade amplification strategy is used to fabricate biofuel cell. • Carbon-coated MoS 2 with large surface area and excellent conductivity are fabricated for construction of biofuel cells. • A high-performance self-powered biosensor developed based on biofuel cell for detection of microRNA-21. [ABSTRACT FROM AUTHOR]

Cancer is a serious threat to human health, and early identification of cancer biomarkers is crucial for timely treatment. A dual-mode biosensing platform has been developed to identify colon carcinoma suppressor microRNA-199a (miRNA-199a). A biofuel cell is firstly constructed using hybridization chain reaction and catalytic hairpin assembly self-assembly. The anode is a flexible carbon cloth (CP) loaded with glucose oxidase-functionalized molybdenum disulfide nanorods (MoS 2 nanorods), and the bio-cathode is made up of double-stranded deoxyribonucleotide chains generated by nucleic acid amplification technology. The linear range of the electrochemical method is 0.1 fM-100 pM, and the limit of detection is 24.1 aM (S/N = 3). The colorimetric method has a linear range of 0.1 fM-10000 pM with detection limit of 34.5 aM (S/N = 3). The combination of MoS 2 nanorods, enzyme-free cascade signal amplification technology, and dual-mode detection strategy provides high sensitivity and accuracy, offering a promising method for accurate determination of cancer biomarkers. • The two-dimensional nanomaterial MoS 2 nanorods are prepared as a substrate for a self-powered biosensor. • Smart self-powered sensor is developed with triple-signal amplification based on - MoS 2 nanorods, - HCR and CHA. • A colorimetric/electrochemical dual-mode sensing system is developed for colon cancer suppressor gene. [ABSTRACT FROM AUTHOR]

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 self-assembly introduction signal I bilirubin oxidase and a tetrahedral DNA nanostructure that produces a double-helical DNA chain to adsorb signal II electron acceptor [Ru(NH 3) 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. • A self-powered biosensor for detection of tumor biomarker is developed using biocathodic double signal amplification design. • CHA and tetrahedral DNA nanostructure can produce a long double-helical DNA chain to introduce signal- electron acceptor. • The developed assay not only improves the stability, but also greatly enhances the sensitivity and selectivity. [ABSTRACT FROM AUTHOR]