Spatiotemporally Controllable MicroRNA Imaging in Living Cells via a Near-Infrared Light-Activated Nanoprobe

Precision detection of hepatocellular carcinoma-associated telomerase RNA with SA@Comb-HCR nanosystem

Accurate intracellular visualization of human telomerase RNA (hTR) is imperative for early diagnosis and treatment monitoring of hepatocellular carcinoma (HCC). While isothermal amplification-based DNA cascade strategies are promising, challenges persist in achieving great intake efficiency of detection probes within tumor cells and enhancing intracellular reaction efficiency. This study introduces a SA@Comb-HCR nanosystem, a highly effective approach for in situ hTR detection in HCC cells. Sodium alginate-coated liposomes ensures efficient nanoprobe delivery, which are then combined with proximity effect-inspired signal amplification. The coating of sodium alginate facilitates receptor-mediated endocytosis, prevents serum protein adhesion, and mitigates cationic liposome cytotoxicity. The designed Comb-like consolidated hairpin probe enhances the concentration of the local reactant, resulting in cascade amplification upon hTR activation. This technique achieves precision detection of intracellularly overexpressed hTR in HCC cells with a remarkable detection limit of 0.7 pM. This approach holds great promise for advancing targeted and sensitive early clinical diagnosis of HCC.

Exonuclease-iii -propelled DNAzyme cascade for sensitive and reliable cervical cancer related miRNA analysis

MicroRNAs (miRNAs) can serve as biomarkers for early-diagnosis, therapy, and postoperative care of cervical cancer. Sensitive and reliable quantification of miRNA remains a huge challenge due to its low expressing levels and background interference. Herein, we propose a novel exonuclease-III (Exo-III)-propelled DNAzyme cascade for sensitive and high-efficient miRNA analysis. This method involves the engineering of compact DNAzyme hairpin probes, including the H1 probe and H2 probe. The H1 probe is designed with exposed analyte recognition subunits that can specifically recognize target miRNA. This recognition triggers two processes: Exo-iii-assisted target regeneration and successive substrate cleavage catalyzed by DNAzyme. The unique character of Exo-III that catalyzes removal of mononucleotides from the blunt or recessed 3'-OH termini of dsDNA confers the approach with a minimal background signal. The multiple signal cycles provided an abundant signal amplification and consequently, the method exhibited a low limit of detection of 3.12 fM, and a better specificity over several homologous miRNAs. In summary, this powerful Exo-III driven DNAzyme cascaded system offers broader and more adaptable methods for comprehending the activities of miRNA in various biological occurrences.

Light-activated CRISPR-Cas12a for amplified imaging of microRNA in cell cycle phases at single-cell levels

An ortho-nitrobenzyl phosphate ester-caged nucleic acid hairpin structure coupled to the CRISPR-Cas12a complex is introduced as a functional reaction module for the light-induced activation of the CRISPR-Cas12a (LAC12a) machinery toward the amplified fluorescence detection of microRNA-21 (miRNA-21). The LAC12a machinery is applied for the selective, in vitro sensing of miRNA-21 and for the intracellular imaging of miRNA-21 in different cell lines. The LAC12a system is used to image miRNA-21 in different cell cycle phases of MCF-7 cells. Moreover, the LAC12a machinery integrated in cells enables the two-photon laser confocal microscopy-assisted, light-stimulated spatiotemporal, selective activation of the CRISPR-Cas12a miRNA-21 imaging machinery at the single-cell level and the evaluation of relative expression levels of miRNA-21 at distinct cell cycle phases. The method is implemented to map the distribution of cell cycle phases in an array of single cells.

Remotely Activated DNA Probe System for the Detection and Imaging of Dual miRNAs

Cancers remain the leading cause of mortality worldwide. It is crucial to detect cancer at an early stage for improving survival rates. Biomarkers have precise implications for cancer progression. Here, we built a straightforward DNA probe system that could be activated by near-infrared light to detect dual miRNAs with a high specificity. This probe is built on the basis of upconversion nanoparticles, which could emit ultraviolet light and activate DNA probes adsorbed on the outer layer. The DNA probe system is remotely controlled through manipulation of the near-infrared (NIR) light, enabling simultaneous detection of dual miRNAs. The DNA nanosystem could be effectively endocytosed by cancer cells and reflect expression levels of dual miRNAs. Overall, this study demonstrates a promising remote-controlled DNA nanoplatform for the simultaneous detection of dual miRNAs, which has tremendous potential for precise cancer diagnostics and therapies.

Stimuli-responsive probes for amplification-based imaging of miRNAs in living cells

MicroRNAs (miRNAs) have emerged as important biomarkers in biomedicine and bioimaging due to their roles in various physiological and pathological processes. Real-time and in situ monitoring of dynamic fluctuation of miRNAs in living cells is crucial for understanding these processes. However, current miRNA imaging probes still have some limitations, including the lack of effective amplification methods for low abundance miRNAs bioanalysis and uncontrollable activation, leading to background signals and potential false-positive results. Therefore, researchers have been integrating activatable devices with miRNA amplification techniques to design stimuli-responsive nanoprobes for "on-demand" and precise imaging of miRNAs in living cells. In this review, we summarize recent advances of stimuli-responsive probes for the amplification-based imaging of miRNAs in living cells and discuss the future challenges and opportunities in this field, aiming to provide valuable insights for accurate disease diagnosis and monitoring.

Overcoming tumor microenvironment obstacles: Current approaches for boosting nanodrug delivery

In order to achieve targeted delivery of anticancer drugs, efficacy improvement, and side effect reduction, various types of nanoparticles are employed. However, their therapeutic effects are not ideal. This phenomenon is caused by tumor microenvironment abnormalities such as abnormal blood vessels, elevated interstitial fluid pressure, and dense extracellular matrix that affect nanoparticle penetration into the tumor's interstitium. Furthermore, nanoparticle properties including size, charge, and shape affect nanoparticle transport into tumors. This review comprehensively goes over the factors hindering nanoparticle penetration into tumors and describes methods for improving nanoparticle distribution by remodeling the tumor microenvironment and optimizing nanoparticle physicochemical properties. Finally, a critical analysis of future development of nanodrug delivery in oncology is further discussed. STATEMENT OF SIGNIFICANCE: This article reviews the factors that hinder the distribution of nanoparticles in tumors, and describes existing methods and approaches for improving the tumor accumulation from the aspects of remodeling the tumor microenvironment and optimizing the properties of nanoparticles. The description of the existing methods and approaches is followed by highlighting their advantages and disadvantages and put forward possible directions for the future researches. At last, the challenges of improving tumor accumulation in nanomedicines design were also discussed. This review will be of great interest to the broad readers who are committed to delivering nanomedicine for cancer treatment.

Polyhedral Au Nanoparticle/MoOx Heterojunction-Enhanced Ultrasensitive Dual-Mode Biosensor for miRNA Detection Combined with a Nonenzymatic Cascade DNA Amplification Circuit

A novel homologous surface-enhanced Raman scattering (SERS)-electrochemical (EC) dual-mode biosensor based on a 3D/2D polyhedral Au nanoparticle/MoO_x nanosheet heterojunction (PAMS HJ) and target-triggered nonenzyme cascade autocatalytic DNA amplification (CADA) circuit was constructed for highly sensitive detection of microRNA (miRNA). Mixed-dimensional heterostructures were prepared by in situ growth of polyhedral Au nanoparticles (PANPs) on the surface of MoO_x nanosheets (MoO_x NSs) via a seed-mediated growth method. As a detection substrate, the resulting PAMS HJ shows the synergistic effects of both electromagnetic and chemical enhancements, efficient charge transfer, and robust stability, thus achieving a high SERS enhancement factor (EF) of 4.2 × 10⁹ and strong EC sensing performance. Furthermore, the highly efficient molecular recognition between the target and smart lock probe and the gradually accelerated cascade amplification reaction further improved the selectivity and sensitivity of our sensing platform. The detection limits of miRNA-21 in SERS mode and EC mode were 0.22 and 2.69 aM, respectively. More importantly, the proposed dual-mode detection platform displayed excellent anti-interference and accuracy in the analysis of miRNA-21 in human serum and cell lysates, indicating its potential as a reliable tool in the field of biosensing and clinical analysis.

Sensitive analysis of miRNAs via primer exchange reaction integrated with hairpin catalytic reaction

MicroRNAs (miRNAs) can serve as potential biological targets for early screening, targeted therapy, and prognosis in ovarian cancer (OC). However, sensitive and reliable quantification and identification of miRNA remain a huge challenge. Herein, we proposed a simple and reliable approach for the ultra-sensitive detection of miRNA by integrating endonuclease-III (Exo-III) assisted signal recycle, primer exchange reaction (PER), and hairpin catalytic reaction (HCR). In this method, target miRNA specifically binds with toehold sequence to form a blunt 3' terminus in the detection probe (dumbbell probe) that can be recognized by Exo-III, and to initiate subsequent signal amplifications. Based on this, the approach is successfully utilized in detecting OC related miRNAs with high sensitivity (limit of detection for miRNA-211 was 13 aM) and stability. By simply changing the toehold sequence in detection probe, the established approach can be easily extended to other miRNA detection. We believe that the platform is robust in detecting OS related biomarkers and is promising in renovating cancer diagnostic tools.

Intelligent Dual-Lock Deoxyribonucleic Acid Automatons Boosting Precise Tumor Imaging

An early and accurate cancer diagnosis holds the potential to improve treatment and prognosis. Nevertheless, the complexity of the biological system limits the selectivity of existing approaches and makes tumor imaging in vivo particularly challenging. In this study, tumor-specific fluorescence imaging was achieved by building intelligent dual-lock deoxyribonucleic acid automatons (IDEAs) that employed a DNA walking system standing on ZrMOF@MnO₂ multifunctional nanocomposites for controllable molecular recognition. The IDEAs exhibited significantly enhanced fluorescence signals only in the coexistence of both miRNA and GSH of tumor cells, enabling accurate distinguishing of tumor cells from healthy ones. Furthermore, the feasibility and specificity of IDEAs were also validated in vivo with tumor bearing mice successfully. This work highlights the potential of the proposed IDEA strategy for tumor-specific imaging, paving the way for successful precision diagnosis and treatment.

Sensitive miRNA Detection for Early Diagnosis of Psoriasis Based on Dual Signal Recycles

MicroRNAs (miRNAs) play a pivotal role in regulating a variety of biological processes and can be used as biomarkers for the early diagnosis of various diseases, such as psoriasis. Herein, we depict a simple and sensitive miRNA detection method based on dual signal recycles, which is developed on the basis of strand displacement amplification (SDA). The sensor is successfully applied to the detection of miRNA-21 with a wide linear range from 100 fM to 10 nM and a lower limit of detection (LOD) of 67 fM. Because of the simple operation yet improved detection capability, we thereby believe that the developed fluorescent biosensor can be potentially applied for early clinical diagnosis as well as biological researches.

DNA-enabled fluorescent-based nanosensors monitoring tumor-related RNA toward advanced cancer diagnosis: A review

As a burgeoning non-invasive indicator for reproducible cancer diagnosis, tumor-related biomarkers have a wide range of applications in early cancer screening, efficacy monitoring, and prognosis predicting. Accurate and efficient biomarker determination, therefore, is of great importance to prevent cancer progression at an early stage, thus reducing the disease burden on the entire population, and facilitating advanced therapies for cancer. During the last few years, various DNA structure-based fluorescent probes have established a versatile platform for biological measurements, due to their inherent biocompatibility, excellent capacity to recognize nucleic and non-nucleic acid targets, obvious accessibility to synthesis as well as chemical modification, and the ease of interfacing with signal amplification protocols. After decades of research, DNA fluorescent probe technology for detecting tumor-related mRNAs has gradually grown to maturity, especially the advent of fluorescent nanoprobes has taken the process to a new level. Here, a systematic introduction to recent trends and advances focusing on various nanomaterials-related DNA fluorescent probes and the physicochemical properties of various involved nanomaterials (such as AuNP, GO, MnO2, SiO2, AuNR, etc.) are also presented in detail. Further, the strengths and weaknesses of existing probes were described and their progress in the detection of tumor-related mRNAs was illustrated. Also, the salient challenges were discussed later, with a few potential solutions.

Accurate detection of lung cancer-related microRNA through CRISPR/Cas9-assisted garland rolling circle amplification

BACKGROUND

MicroRNA (miRNA) is reported to be closely related to a variety of pathophysiological processes for carcinoma and considered a potential biomarker for the diagnosis of lung cancer with brain metastasis. However, developing an accurate and sensitive miRNA detection method has proven to be a challenge. The aim of the present study was to integrate the advantages of rolling circle amplification (RCA), clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated nucleases 9 (Cas9), and catalytic hairpin assembly (CHA) technologies to develop an miRNA detection method.

METHODS

In the present study, we developed a novel approach for the sensitive and accurate detection of miRNA through integrating garland RCA and CRISPR/Cas9-assisted signal generation. In this method, target miRNA cyclized dumbbell padlock and triggered the RCA process to form long single-stranded DNA products with a repeated hairpin structure. Double-stranded DNA sequences (dsDNA) were formed with the addition of complementary sequences. With the assistance of the Cas9 enzyme for specific recognition and cleavage of formed dsDNA, RCA products were disassembled into hairpin probes. The generated hairpin probe could be unfolded by target miRNA to initiate the CHA process for signal generation.

RESULTS

Through integration of the RCA and CHA processes, the method demonstrated favorable detection performance. The correlation equation between the signal and concentration of target miRNA was determined to be Y=312.3 × lgC + 2108, with a high correlation coefficient of 0.9786. The approach also exhibited high selectivity to the mismatched miRNAs.

CONCLUSIONS

Our method could be used in the screening, diagnosis, and prognosis of multiple diseases without complicated thermal cycling instrumentation.

Recent advances of catalytic hairpin assembly and its application in bioimaging and biomedicine

Catalytic hairpin assembly (CHA) appears to be a particularly appealing nucleic acid circuit because of its powerful amplification capability, simple protocols, and enzyme-free and isothermal conditions, and can combine with various signal output modes for the biosensing of various analytes. Especially in the last five years, vast CHA related studies have sprung up. With the deep exploration of the CHA mechanism, some novel and excellent CHA strategies have been proposed; meanwhile the CHA cascade strategies with various amplification techniques further improve the analysis performance. Furthermore, diverse CHA based biosensors have been tactfully engineered and extensively employed in imaging applications in living cells and in vivo ascribed to its gentle reaction, efficient amplification and universality. Hence, we present a comprehensive and systematic summary of the progress in CHA and its application in bioimaging and biomedicine to date. At first, we introduced the mechanism and diversification of CHA in detail, including the newly developed CHA and its ingenious combination with a variety of other technologies. Concurrently, we summarized the latest application progress of different CHA strategies in bioimaging and biomedicine, highlighting the merits and drawbacks of representative approaches. Finally, we put forward some views on the challenges and prospects of CHA in bioimaging and biomedicine in the future.

Construction of simple and sensitive pancreatitis related microRNA detection strategy via self-priming triggered cascade signal amplification

Pancreatic diseases, such as pancreatitis and pancreatic cancer, remain the most threatening gastrointestinal diseases with a high mortality due to atypical symptoms. MicroRNA plays crucial roles in regulating metastasis and cell proliferation of pancreatic cancer, constituting important biomarkers for the early diagnosis of pancreatic cancers. Herein, we develop a sensitive and simple exosomal miRNA detection method with only a dual-hairpin-probe. In detail, the dual-hairpin-probe is constructed through combination of two functional sections for both target miRNA identification and signal amplification. With only one probe, the method possesses the capability to avoid interferences from concentration changes of other probes, and exhibits a higher stability which is demonstrated through the obtained low coefficients of variation (CV) of 6.73%. With let-7a as detection target, the LOD of the established method is determined to be 243 aM, while maintaining a high discriminating capability towards let-7a homogenous miRNAs.

Near-Infrared Light Controllable DNA Walker Driven by Endogenous Adenosine Triphosphate for in Situ Spatiotemporal Imaging of Intracellular MicroRNA

As a powerful signal amplification tool, the DNA walker has been widely applied to detect rare microRNA (miRNA) in vivo. Despite the significant advances, a near-infrared (NIR) light controllable DNA walker for signal amplification powered by an endogenous initiator has not been realized, which is crucial for spatiotemporal imaging of miRNA in living cells with high sensitivity. Herein, we constructed a NIR-photoactivatable DNA walker system, which was powered by endogenous adenosine triphosphate (ATP) for in situ miRNA imaging with spatial and temporal resolution. The system was very stable with an extremely low fluorescent background for the bioimaging in living cells. We employed upconversion nanoparticles (UCNPs) as the carriers of the DNA probe and transducers of converting NIR to UV light. Coupled with the DNA walker fueled by intracellular ATP, a smart system based on the NIR light initiated DNA walker was successfully developed for precise spatiotemporal control in living cells. Triggered by NIR light, the DNA walker could autonomously and progressively travel along the track with the assistance of intracellular ATP. The system has been successfully applied for in situ miRNA imaging in different cell lines with highly spatial and temporal resolution. This strategy can expand NIR photocontrol the DNA walker for precise imaging in a biological system.

Application of lanthanide-doped upconversion nanoparticles for cancer treatment: a review

With the excellent ability to transform near-infrared light to localized visible or UV light, thereby achieving deep tissue penetration, lanthanide ion-doped upconversion nanoparticles (UCNP) have emerged as one of the most striking nanoscale materials for more effective and safer cancer treatment. Up to now, UCNPs combined with photosensitive components have been widely used in the delivery of chemotherapy drugs, photodynamic therapy and photothermal therapy. Applications in these directions are reviewed in this article. We also highlight microenvironmental tumor monitoring and precise targeted therapies. Then we briefly summarize some new trends and the existing challenges for UCNPs. We hope this review can provide new ideas for future cancer treatment based on UCNPs.

Covalent Organic Framework-Derived Carbonous Nanoprobes for Cancer Cell Imaging

Covalent organic frameworks (COFs) have emerged as promising materials for biomedical applications, but their functions remain to be explored and the potential toxicity concerns should be resolved. Herein, it is presented that carbonization significantly enhances the fluorescence quenching efficiency and aqueous stability of nanoscale COFs. The probes prepared by physisorbing dye-labeled nucleic acid recognition sequences onto the carbonized COF nanoparticles (termed C-COF) were employed for cell imaging, which could effectively light up biomarkers (survivin and TK1 mRNA) in living cells. The C-COF has enhanced photothermal conversion capacity, indicating that the probes are also promising candidates for photothermal therapy. The potential toxicity concern from the aromatic rigid building units of COFs was detoured by carbonization. Overall, carbonization is a promising strategy for developing biocompatible and multifunctional COF-derived nanoprobes for biomedical applications. This work may inspire more versatile COF-derived nanoprobes for bioanalysis and nanomedicine.

Spatially Selective Imaging of Mitochondrial MicroRNAs via Optically Programmable Strand Displacement Reactions

MicroRNA (miRNA) functions are tightly regulated by their sub-compartmental location in living cells, and the ability to imaging of mitochondrial miRNAs (mitomiRs) is essential for understanding of the related pathological processes. However, most existing DNA-based methods could not be used for this purpose. Here, we report the development of a DNA nanoreporter technology for imaging of mitomiRs in living cells through near-infrared (NIR) light-controlled DNA strand displacement reactions. The sensing function of the DNA nanoreporters are silent (OFF) during the delivery process, but can be photoactivated (ON) with NIR light after targeted mitochondrial localization, enabling spatially-restricted imaging of two types of cancer-related mitomiRs with improved detection accuracy. Furthermore, we demonstrate imaging of mitomiRs in vivo through spatiotemporally-controlled delivery and activation. Therefore, this study illustrates a simple methodology that may be broadly applicable for investigating the mitomiRs-associated physiological events.

Visual detection of heart failure associated MiRNA with DSN enzyme-based recycling amplification strategy

MicroRNA 21 (miRNA-21) is reported to be closely associated with the development of heart failure, cardiac fibrosis and hypertrophy, which could be a promising biomarker for the early-diagnosis of heart failure. Herein, we propose a novel colorimetric miRNA detection method through the integration of duplex-specific nuclease (DSN)-based signal amplification and AuNPs assembly induced colorimetry. Highlights of the proposed method are calculated as: (i) no high temperature hybridization process is required; (ii) DSN enzyme induced recycling provides a favorable detection sensitivity and discrimination of color changes. We believe that the proposed DSN enzyme based colorimetric assay can be applied to heart failure related diagnostics.

MicroRNA 21 (miRNA-21) is reported to be closely associated with the development of heart failure, cardiac fibrosis and hypertrophy, which could be a promising biomarker for the early-diagnosis of heart failure.

Nanoparticles as Drug Delivery Systems of RNAi in Cancer Therapy

RNA interference (RNAi) can mediate gene-silencing by knocking down the expression of a target gene via cellular machinery with much higher efficiency in contrast to other antisense-based approaches which represents an emerging therapeutic strategy for combating cancer. Distinct characters of nanoparticles, such as distinctive size, are fundamental for the efficient delivery of RNAi therapeutics, allowing for higher targeting and safety. In this review, we present the mechanism of RNAi and briefly describe the hurdles and concerns of RNAi as a cancer treatment approach in systemic delivery. Furthermore, the current nanovectors for effective tumor delivery of RNAi therapeutics are classified, and the characteristics of different nanocarriers are summarized.

Orderly Assembled, Self-Powered FRET Flares for MicroRNA Imaging in Live Cells

Signal amplification provides unparalleled opportunities for visualizing low-abundance targets in living cells. However, self-powered signal amplification has not been achieved because of the lack of "fuel" in living cells. Thus, the aim of this work was to develop an integrated amplification platform for the detection of intracellular miRNA by itself. This system, termed self-powered FRET flares (SPF), was first established by self-assembly to form a DNA nanostructure, and then the FRET flares and fuel DNA as the driving force were precisely and orderly loaded on it, which was able to power target recycle and realize signal amplification without any auxiliary additives under the trigger of intracellular miRNA-21. In addition, it employed AS1411 aptamer to target specific cancer cells and facilitated cell internalization of assembly DNA nanostructures. As a proof of concept, we demonstrated that SPF enabled rapid response to miRNA-21 and improvement of the detection sensitivity compared to previously proposed FRET flares without amplification. This strategy is promising for advancing integrated and self-powered nanomachines to execute diverse tasks, facilitating their biological and medical application.

Nasopharyngeal carcinoma related miRNA detection through a DSN enzyme assisted tetrahedral probe for more accurate prognosis

MicroRNAs (miRNAs) play a pivotal role in cellular functions and in the development and progression of cancer. Precise quantification of miRNAs from different clinical samples is a challenging but necessary endeavor that is largely neglected by many emerging fluorescence technologies. Herein, we propose here a novel miRNA detection method through a designed tetrahedral probe and DSN enzyme for attached signal amplification. The highlights of the method are calculated as: (i) the tetrahedral probe induced a much higher transfection efficiency than normal probes; (ii) the DSN enzyme-based cleavage ensures amplification and thus leads to a high detection sensitivity. In all, we believe that the proposed method could greatly improve the sensitivity of intracellular miRNA imaging methods and contribute to the fundamental research and prognosis of cancer.

MicroRNAs (miRNAs) play a pivotal role in cellular functions and in the development and progression of cancer.

Ultrasensitive Detection of Nasopharyngeal Carcinoma-Related MiRNA through Garland Rolling Circle Amplification Integrated Catalytic Hairpin Assembly

MiRNA is reported to be closely related to nasopharyngeal carcinoma and has the potential to be a biomarker for the early diagnosis of nasopharyngeal carcinoma. However, the detection of miRNAs remains to be improved, given their complexity and low sensitivity. Herein, we propose here a novel miRNA detection method through the integration of garland RCA and CHA. In detail, the method is composed of two important signal amplification processes. For the first signal amplification process, the target miRNA could initiate garland RCA and then generate a nicking site on the products with the assistance of Nb.BbvCI enzymes. Afterward, a CHA process is induced with a designed H probe through the two signal amplification processes; the method exhibited a much-improved sensitivity. At last, we believe that this method is a promising approach capable of being applied in screening, diagnosing, and prognosticating multiple diseases.

Photo-driven self-powered biosensors for ultrasensitive microRNA detection based on metal-organic framework-controlled release behavior

We developed a "signal-on" self-powered biosensing strategy by taking full advantage of both photoelectrochemical biofuel cells (PBFCs) and metal-organic framework (MOF)-controlled release behavior for ultrasensitive microRNA assay. PBFC-based self-powered sensors have the unique characteristics of non-requirement of external power sources, simple fabrication process, miniature size, good anti-interference ability and low cost. Furthermore, based on the target microRNA-induced release of the electron donor ascorbic acid and the high catalytic ability of the biocathode to catalyse the oxygen reduction reaction, photo-driven self-powered biosensors for ultrasensitive microRNA detection were successfully realized. The as-proposed signal-on biosensor not only provides a simple and effective strategy, but also possesses the merits of a wide dynamic concentration response range and high sensitivity for microRNA detection, with a limit of detection down to 0.16 fM.