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Herein, an ultrasensitive electrochemical biosensor for microRNA-155 (miR-155) detection based on the powerful catalytic and continuous walking signal amplification capability of 3D DNAzyme walker and the gold nanoparticles/graphene aerogels carbon fiber paper-based (AuNPs/GAs/CFP) flexible sensing electrode with excellent electrochemical performance was successfully constructed. In a proof-of-concept experiment, in the presence of miR-155, the DNAzyme strands anchored on the streptavidin-modified magnetic beads (MBs) silenced by locked strands can be activated, thus generating the walking arm of the 3D DNAzyme walker. Meanwhile, the substrate strands modified with Fe-MOF-NH 2 nanoparticles were evenly distributed on the surface of MBs and served as tracks of the 3D DNAzyme walker. Once the DNAzyme strand was activated, the catalytic site in the substrate strand can be cleaved in the presence of Mn2+, and a large number of stumps modified with Fe-MOF-NH 2 nanoparticles (output@Fe-MOF-NH 2) will be generated during the continuous and efficient walking cleavage of the DNAzyme walker, driving the recognition-catalysis-release cycle process for signal amplification. Immediately afterwards, the signal was read out through the base complementary pairing of capture probe (PS) immobilized on the surface of the paper-based flexible sensing electrode AuNPs/GAs/CFP and signal probes output@Fe-MOF-NH 2 , thus achieving the quantitative detection of miR-155. Under optimal experimental conditions, the designed 3D DNAzyme walker-based biosensor exhibited a relatively lower limit of detection (LOD) of 56.23 aM, with a linear range of 100 aM to 100 nM. Overall, the proposed 3D DNAzyme walker biosensor exhibited good interference and reproducibility, demonstrating a promising future in the field of clinical disease diagnosis. [Display omitted] • An electrochemical biosensor based on AuNPs/GAs/CFP electrode for miR-155 detection was successfully constructed. • Target-responsive 3D DNAzyme walker provided an important guarantee for ultrasensitive detection of miR-155. • The designed 3D DNAzyme walker-based biosensor exhibited a relatively lower limit of detection (LOD) of 56.23 aM. [ABSTRACT FROM AUTHOR]

Multiplex microRNAs (miRNAs) detection is beneficial for early diagnosis and prognosis of cancer. Herein, duplex-specific nuclease (DSN) powered 3D DNA walker and quantum dots (QDs) barcodes were designed for the simultaneous detection of miRNAs in a homogeneous electrochemical sensor. In the proof-of-concept experiment, the effective active area of the as-prepared graphene aerogel-modified carbon paper (CP-GAs) electrode was ∼14.30 times larger than that of the traditional glassy carbon electrode (GCE), endowing the enhanced capability of loading more metal ions for ultrasensitive detection of miRNAs. In addition, DSN-powered target recycling and DNA walking strategy assured the sensitive detection of miRNAs. After the introduction of magnetic beads (MNs) and electrochemical double enrichment strategies, the integration of triple signal amplification methods yielded good detection results. Under optimal conditions, towards simultaneous detection of microRNA-21 (miR-21) and miRNA-155 (miR-155), a linear range of 10−16–10−7 M and a sensitivity of 10 aM (miR-21) and 2.18 aM (miR-155) were achieved, respectively. It was worth mentioning that the prepared sensor can detect miR-155 down to 0.17 aM, which was also extremely advantageous among the sensors reported so far. What's more, through verification, the prepared sensor had good selectivity and reproducibility, and exhibited good detection ability in complex serum environments, showing great potential in early clinical diagnosis and screening. [Display omitted] • Homogeneous electrochemical sensor for miRNAs simultaneous detection was designed. • DSN-powered 3D DNA walker guaranteed the detection sensitivity. • Quantum dot barcodes provided stable output signal for the constructed sensor. • The detection limits were 10 aM (miR-21) and 2.18 aM (miR-155), respectively. • The prepared sensor exhibited good detection ability in complex serum environment. [ABSTRACT FROM AUTHOR]

• We first proposed a nucleic acid functionalized Zr-MOF paper-based sensor. • This bio-platform can simultaneously detect multiple tumor exosomal miRNAs. • The ability of CFP/GWs/Au bio-platform to detect exosomal miRNAs at aM level. • The practicability of the bio-platform in clinical sample detection was confirmed. Compared with free microRNAs (miRNAs) in blood, miRNAs in exosomes are more abundant and stable. However, simple, reliable and simultaneous detection of exosomal microRNAs remains a challenging. In this study, we proposed a disposable paper-based electrochemical strategy based on nucleic acid functionalized Zr-MOF, which is label-free and enzyme-free, and could simultaneously detect multiple tumor exosomal miRNAs. We constructed a functionalized metal–organic framework (MOF) with electroactive dyes and capped it with hairpin DNA. This proposed bio-platform and MOF can display different electrochemical signals for different target analyses by changing the structures of dye-loaded and hairpin DNA. In view of this, we skill fully designed two kinds of functional MOFs (Zr/MB and Zr/BG) and used them to simultaneously detect exosomal miRNA-155 and exosomal miRNA-21 (as proof-of-concept analysis). This robust biosensor eliminates multiple time-consuming steps associated with existing miRNAs quantification methods, such as reverse transcription and thermocycler amplification, and achieves molecular-level sensitivity to exosomal miRNA-155 (33.4 aM) and exosomal miRNA-21 (23.1 aM). This study combines the advantages of simultaneous biosensing, which disposable paper-based biosensing strategies and represents an important advance in the field of electrochemical analysis and provides unlimited possibilities for the development of flexible, easy-to-use, and inexpensive bioelectrodes. [ABSTRACT FROM AUTHOR]

Abnormal expression of microRNAs is greatly associated with the occurrence of various cancer types, revealing great potential of microRNA as biomarkers for cancer diagnosis and prognosis. Herein, a MXene-MoS 2 heterostructure enhancing electrochemical biosensor coupled with catalytic hairpin assembly (CHA) amplification approach for label-free determination of microRNA-21 (miR-21) was successfully assembled. In particular, the unique micro-nano heterostructure with large specific area and favorable electroconductivity exhibited the ability of excellent confinement effect. Thus, rendered the MXene-MoS 2 heterostructure the ability to trigger more target recycling reaction, giving new vitality to the traditional CHA amplification method. Meanwhile, thionine (Thi) and gold nanoparticles (AuNPs) were anchoring at the surface of MXene-MoS 2 heterostructure, respectively, empowered the sensor the capability of capture probes fixation and miR-21 label-free determination. When numerous electronegative double-stranded DNA generated, the electron transfer was greatly hindered, resulting in signal decrease. Accordingly, the design denoted a broad dynamic range from 100 fM to 100 nM and a detection limit of about 26 fM, comparable or lower than previous reported methods for miR-21 detection. Furthermore, the sensing platform supplied satisfactory selectivity, reproducibility and stability towards the miR-21 detection. The real sample determination also showed a promising performance under clinical circumstance. Finally, from the clinical standpoint, the proposed biosensor is a considerable platform toward early disease detection and monitoring. [Display omitted] • MXene-MoS 2 's highly fold structure and superior reactive area increased hybridization efficiency through collision. • CHA synergized with MXene-MoS 2 showed a superb detection performance toward miR-21 with a low limit of detection (26 fM). • The proposed biosensor performed well in normal human serum with good accuracy and dependability. [ABSTRACT FROM AUTHOR]