A Portable Self-Powered Electrochemical Sensor Based on Zinc-Air Battery for Detection of Hydrogen Sulfide.

The self-powered electrochemical sensor (SPES), an analytical sensing device without external power supply, is integrated with the dual function of power supply and detection performance, which lay the foundation for the development of intelligent and portable electrochemical sensing devices. Herein, a novel SPES based on a zinc-air battery was constructed for the detection of hydrogen sulfide (H2S) in the lysate of colon cancer cells. Typically, an Fe/Fe3C@graphene foam with oxygen reduction performance was used to construct SPES based on a zinc-air battery (ZAB-SPES), which brings the open-circuit voltage to 1.30 V. Among them, the poisoning effect of H2S causes the catalytic performance of the oxygen reduction catalyst to decrease, causing a significant decrease in the discharge voltage of ZAB. Based on this principle, ZAB-SPES was constructed for the detection of H2S using a digital multimeter. The proposed ZAB-SPES demonstrated good selectivity and reproducibility for detecting H2S compared to the results of the H2S-specific fluorescence probe. This strategy enriches the idea of constructing a self-powered sensor and a digital multimeter as detection devices, providing technical support for the portability of SPESs.

Reactive Oxygen-Correlated Photothermal Imaging of Smart COF Nanoreactors for Monitoring Chemodynamic Sterilization and Promoting Wound Healing.

Chemodynamic therapy (CDT) has emerged as a promising approach for treating infected diabetic wounds, while reliable imaging technology for simultaneous monitoring of ROS and therapeutic processes is still a formidable challenge. Herein, smart covalent organic framework (COF) nanoreactors (COF NRs) are constructed by hyaluronic acid (HA) packaged glucose oxidase (GOx) covalently linked Fe-COF for diabetic wound healing. Upon the breakdown of the HA protective layer, GOx consumes glucose to produce gluconic acid and hydrogen peroxide (H2O2), resulting in decreased local pH and H2O2 supplementation. Density functional theory (DFT) calculations show that Fe-COF has high catalytic activity towards H2O2, leading to in situ generation of hydroxyl radicals (·OH) for sterilization, and the localized downregulation of glucose effectively improved the microenvironment of diabetic wounds. Meanwhile, based on the near-infrared photothermal imaging of oxidized 3,3',5,5'-tetramethylbenzidine (oxTMB), the authors showed that TMB can be applied for the point-of-care testing of ·OH and glucose, and assessing the sterilization progress in vivo. More significantly, the facile photothermal signaling strategy can be extended to monitor various ROS-mediated therapeutic systems, enabling accurate prediction of treatment outcomes.

Human trophoblast invasion and migration are mediated by the YAP1-CCN1 pathway: defective signaling in trophoblasts during early-onset severe preeclampsia.

The transcription coactivator YAP1 mediates the major effects of the Hippo signaling pathway. The CCN family is a small group of glycoproteins known to be downstream effectors of YAP1 in diverse tissues. However, whether CCN family members mediate the effects of YAP1 in human trophoblasts is unknown. In this study, placental expression of both YAP1 and CCN1 was found to be impaired in pregnancies complicated by early-onset severe preeclampsia (sPE). CCN1 was expressed not only in cytotrophoblasts, trophoblast columns and mesenchymal cells, similar to active YAP1, but also in syncytiotrophoblasts of normal first-trimester placental villi; moreover, decidual staining of active YAP1 and CCN1 was found in both interstitial and endovascular extravillous trophoblasts. In cultured immortalized human trophoblastic HTR-8/SVneo cells, knockdown of YAP1 decreased CCN1 mRNA and protein expression and led to impaired cell invasion and migration. Also, CCN1 knockdown negatively affected HTR-8/SVneo cell invasion and migration but not viability. YAP1 knockdown was further found to impair HTR-8/SVneo cell viability via G0/G1 cell cycle arrest and apoptosis, while CCN1 knockdown had minimal effect on cell cycle arrest and no effect on apoptosis. Accordingly, treatment with recombinant CCN1 partially reversed the YAP1 knockdown-induced impairment in trophoblast invasion and migration but not in viability. Thus, CCN1 mediates the effects of YAP1 on human trophoblast invasion and migration but not apoptosis, and decreased placental expression of YAP1 and CCN1 in pregnancies complicated by early-onset sPE might contribute to the pathogenesis of this disease.

Ambient Synthesis of Porphyrin-Based Fe-Covalent Organic Frameworks for Efficient Infected Skin Wound Healing.

Reactive oxygen species (ROS) have emerged as a promising treatment option for antibacterial and biofilm eradication. However, their therapeutic efficacy is significantly hampered by the unique microenvironments of diabetic wounds. In this study, we designed and synthesized porphyrin-based Fe covalent organic frameworks (Fe-COF) through a Schiff base condensation reaction. Subsequently, Fe-COF were encapsulated with hyaluronic acid (HA) through electrostatic adsorption, resulting in a novel formulation named HA-Fe-COF for diabetic wound healing. HA-Fe-COF were engineered to respond to hyaluronidase in the infected wound, leading to the controlled release of Fe-COF. Those released Fe-COF served a dual role as photosensitizers, generating singlet oxygen and localized heating when exposed to dual light sources. Additionally, they acted as peroxidase-like nanozymes, facilitating the production of ROS through enzymatic reactions. This innovative approach enabled a synergistic therapeutic effect combining photodynamic, photothermal, and chemodynamic modalities. Furthermore, the sustained release of HA from HA-Fe-COF promoted angiogenesis, collagen deposition, and re-epithelialization during the diabetic wound healing process. This "all-in-one" strategy offers a novel approach for the development of antimicrobial and biofilm eradication strategies that minimize damage to healthy tissues in vivo.

Transistor-based immunosensor using AuNPs-Ab2-HRP enzyme nanoprobe for the detection of antigen biomarker in human blood.

Alpha-fetoprotein (AFP) is inextricably linked to various diseases, including liver cancer. Thus, detecting the content of AFP in biology has great significance in diagnosis, treatment, and intervention. Motivated by the urgent need for affordable and convenient electronic sensors in the analysis and detection of aqueous biological samples, we combined the solution-gated graphene transistor (SGGT) with the catalytic reaction of enzyme nanoprobes (HRP-AuNPs-Ab2) to accurately sense AFP. The SGGT immunosensor demonstrated high specificity and stability, excellent selectivity, and excessive linearity over a range of 4 ng/mL to 500 ng/mL, with the lower detection limit down to 1.03 ng/mL. Finally, clinical samples were successfully detected by the SGGT immunosensor, and the results were consistent with chemiluminescence methods that are popular in hospitals for detecting AFP. Notably, the SGGT immunosensor is also recyclable, so it has excellent potential for use in high-throughput detection.

Structure modulation of two-dimensional transition metal chalcogenides: recent advances in methodology, mechanism and applications.

Together with the development of two-dimensional (2D) materials, transition metal dichalcogenides (TMDs) have become one of the most popular series of model materials for fundamental sciences and practical applications. Due to the ever-growing requirements of customization and multi-function, dozens of modulated structures have been introduced in TMDs. In this review, we present a systematic and comprehensive overview of the structure modulation of TMDs, including point, linear and out-of-plane structures, following and updating the conventional classification for silicon and related bulk semiconductors. In particular, we focus on the structural characteristics of modulated TMD structures and analyse the corresponding root causes. We also summarize the recent progress in modulating methods, mechanisms, properties and applications based on modulated TMD structures. Finally, we demonstrate challenges and prospects in the structure modulation of TMDs and forecast potential directions about what and how breakthroughs can be achieved.

Effects of Deuterium Isotopes on Pt(II) Complexes and Their Impact on Organic NIR Emitters.

Insight into effect of deuterium isotopes on organic near-IR (NIR) emitters was explored by the use of self-assembled Pt(II) complexes H-3-f and HPh-3-f, and their deuterated analogues D-3-f and DPh-3-f, respectively (Scheme 2). In vacuum deposited thin film, albeit having nearly identical emission spectral feature maximized at ~810 nm, H-3-f and D-3-f exhibit remarkable difference in photoluminescence quantum yield (PLQY) of 29 % and 50 %, respectively. Distinction in PLQY is also observed for HPh-3-f (800 nm, 50 %) and DPh-3-f (798 nm, 67 %). We then elucidated the theoretical differences in the impact on near-infrared (NIR) luminescence between Pt(II) complexes and organic small molecules upon deuteration. The results establish a general guideline for the deuteration on NIR emission efficiency. From a perspective of practical application, NIR OLEDs based on D-3-f and DPh-3-f emitters attain EQEmax of 15.5 % (radiance 31,287 mW Sr-1 m-2 ) and 16.6 % (radiance of 32,279 mW Sr-1 m-2 ) at 764 nm and 796 nm, respectively, both of which set new records for NIR OLEDs of >750 nm.

N-doped carbon Co/CoOx with laccase-like activity for detection of epinephrine.

N-doped carbon Co/CoOx with laccase-like activity was directionally designed by pyrolyzing Co-coordination polymer and applied to detect epinephrine, which revealed a new preparation strategy for laccase mimics. The formation mechanism of the N-doped carbon Co/CoOx nanozyme was reconnoitered by a thermogravimetric-mass spectrometry system (TG-MS). N-doped carbon Co/CoOx exhibited outstanding laccase-like activity, and the Michaelis-Menten constant and maximum initial velocity were calculated to be 0.087 mM and 0.0089 µM s-1, respectively. Based on this principle, a simple colorimetric sensing platform was developed for the quantitative detection of epinephrine, which can be used to diagnose pheochromocytoma. In addition, the visual platform for detecting epinephrine exhibited a linear range of 3 to 20 µg mL-1 and a calculated detection limit of 0.42 µg mL-1. Therefore, the proposed colorimetric sensing platform is a promising candidate to be applied in precise early pheochromocytoma diagnosis.

In Situ Measurement of ATP in Single Cells by an Amphiphilic Aptamer-Assisted Electrochemical Nano-Biosensor.

In situ and quantitative measurements of adenosine 5'-triphosphate (ATP) in single living cells are highly desired for understanding several sorts of necessary physiological and pathological processes. Due to its small size and high sensitivity, an ultra-microelectrode can be used for single-cell analysis. However, ATP is difficult to detect in single cells because it is nonelectroactive and low in content. Herein, we introduced an electrochemical nano-biosensor based on an amphiphilic aptamer-assisted carbon fiber nanoelectrode (aptCFNE) with high signal-to-noise ratio. The low current (e.g., 60 pA) and the tiny diameter of the tip (ca. 400 nm) of the nanosensor made it noninvasive to living cells. The amphiphilic aptamer has good biocompatibility and can be stably modified to the surface of functionalized electrodes. CFNE, which was modified with ferrocene-labeled aptamer, could quickly and selectively detect ATP content in the nucleus, cytoplasm, and extracellular space of single HeLa cells. The results showed that the ATP contents in the nucleus, cytoplasm, and extracellular space were 568 ± 9, 461 ± 20, and 312 ± 4 µM, respectively. The anticancer drug treatment effects on the cellular level were further recorded, which was of great significance for understanding ATP-related biological processes and drug screenings. This strategy is universally applicable to detect other targets by changing the aptamer sequence, which will greatly improve our understanding of cell heterogeneity and provide a more reliable scientific basis for exploring major diseases at the single-cell level.

Tetraphenylethylene-Functionalized Metal-Organic Frameworks with Strong Aggregation-Induced Electrochemiluminescence for Ultrasensitive Analysis through a Multiple Convertible Resonance Energy Transfer System.

Since aggregation-induced electrochemiluminescence (AIECL) combined the merits of aggregation-induced emission (AIE) and electrochemiluminescence (ECL), it has become a research hotspot recently. Herein, novel kinds of functional metal-organic frameworks (MOFs) with strong AIECL were reported through doping tetraphenylethylene (TPE) into UiO-66. Due to the porosity and highly ordered topological structure that caused the confinement effect of MOFs, the molecular motion of TPE was effectively limited within UiO-66, resulting in strong AIE. Meanwhile, the large specific surface area and porous structure of UiO-66 allowed TPE to react with coreactants more effectively, which was beneficial to ECL. Thus, the TPE-functionalized UiO-66 (TPE-UiO-66) showed excellent AIECL performance surprisingly. Inspired by this, a multiple convertible ECL resonance energy transfer (ECL-RET) system was constructed through a DNA Y structure that regulated the distance between the energy donor (TPE-UiO-66) and different energy acceptors (gold nanoparticles and Adriamycin). Furthermore, an ultrasensitive ECL biosensor for the detection of Mucin 1 (MUC1) was developed through the introduction of the novel ECL-RET system. In the presence of MUC1, the DNA Y structure was constructed, keeping the gold nanoparticles (AuNPs) away from TPE-UiO-66. Then, Adriamycin (Dox) could be embedded in the DNA Y structure and act as an energy acceptor to receive the energy of TPE-UiO-66, which made the biosensor produce a strong ECL response. As expected, the developed ECL biosensor exhibited superior detection performance for MUC1. This work provided a novel way to realize AIECL and board the application of AIECL in analytical chemistry.

Zinc-Air Battery-Based Self-Powered Sensor with High Output Power for Ultrasensitive MicroRNA let-7a Detection in Cancer Cells.

Self-powered sensors do not require a power supply and are easy to miniaturize, which have potential for constructing wearable, portable, and real-time detection devices. However, it is challenging for the detection of low abundant targets due to the low output power density of fuel cells and much interference of complex biological environment. Herein, a new kind of photocatalytic zinc-air battery-based self-powered electrochemical sensor (ZAB-SPES) was constructed for the detection of microRNA let-7a (miRNA let-7a) by combining magnetic nanobeads (MBs) with a metal-organic framework loaded with glucose oxidase (MOFs@GOX). Poly(1,4-di(2-thienyl))benzene (PDTB) was used as the photocathode material, and the proposed ZAB-SPES had a high power density of 22.8 µW/cm2, which was 2-3-fold of commonly used photofuel cells. MBs can capture and separate miRNA from complex samples quickly with a high separation efficiency of 99% within 60 s. The competitive reaction of oxygen reduction reaction between PDTB and MOFs@GOX would change the output power density of the ZAB-SPES. Based on the relationship between output power density and target concentration, the ZAB-SPES realized ultrasensitive detection of miRNA let-7a with a detection limit down to 1.38 fM. Furthermore, the successful detection of miRNA let-7a in A549 cancer cells indicated the great prospects of ZAB-SPES in clinical analysis and early diagnosis of cancers.

Magnetic Rolling Circle Amplification-Assisted Single-Particle Collision Immunosensor for Ultrasensitive Detection of Cardiac Troponin I.

Owing to its simplicity, high throughput, and ultrasensitivity, single-particle collision electrochemistry (SPCE) has attracted great attention in biosensing, especially labeled SPCE. However, the low signal conversion efficiency and much interference from complex samples limit its wide application. Here, a new and robust SPCE immunosensor was proposed for ultrasensitive cardiac troponin I (cTnI) detection by combining target-driven rolling circle amplification (RCA) with magnetic beads (MBs). Antibody-modified MBs have good stability, dispersity, and magnetic response capacity in complex samples, enabling efficient capture and separation of cTnI with high specificity and anti-interference ability. The presence of cTnI could specifically drive the formation of magnetic immunocomplexes followed by triggering RCA and enzyme digestion reaction. By using Pt nanoparticles (Pt NPs)-modified ssDNA as signal probes, one cTnI molecule could induce the release of 4.5 × 104 Pt NPs for collision experiments, greatly enhancing signal conversion efficiency and detection sensitivity. Based on the integration of MBs with RCA, the SPCE immunosensor realized 0.57 fg/mL cTnI detection with a wide linear range of 1 fg/mL to 50 ng/mL. Furthermore, cTnI detection in serum samples of myocardial infarction patients was successfully performed, demonstrating great application prospect of the SPCE immunosensor in clinical diagnosis.

Efficient Pyrazolo[5,4-f]quinoxaline Functionalized Os(II) Based Emitter with an Electroluminescence Peak Maximum at 811†nm.

Upon fusing the pyrazinyl pyrazole entity in giving pyrazolo[3,4-f]quinoxaline chelate, the corresponding Os(II) based NIR emitter exhibited "invisible" and efficient electroluminescence with a peak maximum at 811 nm. A maximum external quantum efficiency of 0.97 % and a suppressed efficiency roll-off till a current density of 300 mA cm-2 was also exhibited.

High sensitivity and rapid detection of hepatitis B virus DNA using lateral flow biosensors based on Au@Pt nanorods in the absence of hydrogen peroxide.

Nanozymes are a kind of nanomaterial with enzymatic activity, and have attracted wide attention in signal probe fields owing to their good catalytic activity and stability. Herein, we designed gold@platinum nanorods (Au@Pt) with enhanced oxidase-like activity as signal probes to construct lateral flow biosensors (LFBs) for the detection of hepatitis B virus DNA (HBV-DNA). The enhanced oxidase-like activity of Au@Pt nanorods can effectively catalyze the oxidation of 3,3',5,5'-tetramethylenebenzidine (TMB) to a blue substrate in the absence of hydrogen peroxide (H2O2). Based on this principle, LFBs using Au@Pt nanorods as signal probes can provide an effective signal amplification strategy and prevent biomolecules from being affected by H2O2. Under optimal conditions, LFBs have a good linear relationship between 0.1 nM and 50 nM, and the calculated detection limit was 8.5 pM. The technological strategy in the detection and quantification of HBV-DNA in this work may be helpful to achieve a rapid and accurate diagnosis of early HBV-DNA and provide new ideas for the development of point-of-care testing.

The Effects of Migration and Limited Medical Resources of the Transmission of SARS-CoV-2 Model with Two Patches.

The sudden outbreak of SARS-CoV-2 has caused the shortage of medical resources around the world, especially in developing countries and underdeveloped regions. With the continuous increase in the duration of this disease, the control of migration of humans between regions or countries has to be relaxed. Based on this, we propose a two-patches mathematical model to simulate the transmission of SARS-CoV-2 among two-patches, asymptomatic infected humans and symptomatic infected humans, where a half-saturated detection rate function is also introduced to describe the effect of medical resources. By applying the methods of linearization and constructing a suitable Lyapunov function, the local and global stability of the disease-free equilibrium of this model without migration is obtained. Further, the existence of forward/backward bifurcation is analyzed, which is caused by the limited medical resources. This means that the elimination or prevalence of the disease no longer depends on the basic reproduction number but is closely related to the initial state of asymptomatic and symptomatic infected humans and the supply of medical resources. Finally, the global dynamics of the full model are discussed, and some numerical simulations are carried to explain the main results and the effects of migration and supply of medical resources on the transmission of disease.

Laparoscopic liver resection is associated with less significant muscle loss than the conventional open approach.

BACKGROUND: Laparoscopic liver resections (LLR) have been shown a treatment approach comparable to open liver resections (OLR) in hepatocellular carcinoma (HCC). However, the influence of procedural type on body composition has not been investigated. The aim of the current study was to compare the degree of skeletal muscle loss between LLR and OLR for HCC. METHODS: By using propensity score matching (PSM) analysis, 64 pairs of patients were enrolled. The change of psoas muscle index (PMI) after the operation was compared between the matched patients in the LLR and OLR. Risk factors for significant muscle loss (defined as change in PMI > mean change minus one standard deviation) were further investigated by multivariate analysis. RESULTS: Among patients enrolled, there was no significant difference in baseline characteristics between the two groups. The PMI was significantly decreased in the OLR group (P = 0.003). There were also more patients in the OLR group who developed significant muscle loss after the operations (P = 0.008). Multivariate analysis revealed OLR (P = 0.023), type 2 diabetes mellitus, indocyanine green retention rate at 15 min (ICG-15) > 10%, and cancer stage ≧ 3 were independent risk factors for significant muscle loss. In addition, significant muscle loss was associated with early HCC recurrence (P = 0.006). Metabolomic analysis demonstrated that the urea cycle may be decreased in patients with significant muscle loss. CONCLUSION: LLR for HCC was associated with less significant muscle loss than OLR. Since significant muscle loss was a predictive factor for early tumor recurrence and associated with impaired liver metabolism, LLR may subsequently result in a more favorable outcome.

The interaction between predictability and pre-boundary lengthening on syllable duration in Taiwan Southern Min.

This study investigated how predictability and prosodic phrasing interact in accounting for the variability of syllable duration in Taiwan Southern Min. Speech data were extracted from 8 hours of spontaneous speech. Three predictability measurements were examined: bigram surprisal, bigram informativity, and lexical frequency. Results showed that higher informativity and surprisal led to longer syllables. As for the interaction with prosodic positions, there was a general weakening of predictability effects for syllables closer to the boundary, especially in the pre-boundary position, where pre-boundary lengthening was the strongest. However, the effect of word informativity appeared to be least modulated by this effect of boundary marking. These findings are consistent with a hypothesis that prosodic structure modulates the predictability effects on phonetic variability. The robustness of informativity in predicting syllable duration also suggests a possibility of stored phonetic variants associated with a word's usual contextual predictability.

Metal-Mediated Polydopamine Nanoparticles-DNA Nanomachine Coupling Electrochemical Conversion of Metal-Organic Frameworks for Ultrasensitive MicroRNA Sensing.

The development of a robust sensing platform with an efficient probe assembly, and ingenious signal conversion is of great significance for bioanalytical application. In this work, a multipedal polydopamine nanoparticles-DNA (PDANs-DNA) nanomachine coupling electrochemical-driven metal-organic frameworks (MOFs) conversion-enabled biosensing platform was constructed. The PDANs-DNA nanomachine was designed based on Ca2+-mediated DNA adsorption and target-triggered catalytic hairpin assembly on PDANs, which not only maintained the DNA immobilization simplicity but also possessed a high walking efficiency. PDANs-DNA nanomachine could walk fast on the electrode via multiple legs under exonuclease III driving, resulting in the formation of DNA dendrimers through two hairpins assembly. The MOFs (Fe-MIL-88-NH2) probe was decorated on the DNA dendrimers to act as a porous metal precursor and converted into electroactive Prussian Blue by a controlled electrochemical approach, which was a facile, simple, and room-temperature approach compared with the commonly employed MOFs conversion methods. Using microRNA-21 (miRNA-21) as the model target, the proposed biosensor achieved miRNA-21 detection ranging from 10 aM to 10 pM with the detection limit of 5.8 aM. The proposed strategy presented a highly efficient walking platform with the ingenious electrochemical conversion of MOFs, providing more options for the design of an electrochemical platform and holding potential applications in clinical analysis and disease diagnosis.

Photocatalytic Fuel Cell-Assisted Molecularly Imprinted Self-Powered Sensor: A Flexible and Sensitive Tool for Detecting Aflatoxin B1.

The self-powered electrochemical sensor has gained big achievements in energy and devices, but it is challenging in analytical application owing to its low energy conversion efficiency and limited selectivity caused by the plentiful interference in actual samples. Herein, a new self-powered biosensor was constructed by the integration of a photocatalytic fuel cell (PFC) with a molecular imprinting polymer (MIP) to achieve sensitive and specific detection of aflatoxin B1 (AFB1). Compared with other fuel cells, the PFC owns the advantages of low cost, high energy, good stability, and friendly environment by using light as the excitation source. MoS2-Ti3C2Tx MXene (MoS2-MX) served as the photoanode material for the first time by forming a heterojunction structure, which can enhance the photocurrent by about 3-fold and greatly improve the photoelectric conversion efficiency. Aiming at the poor selectivity of the self-powered sensor, the MIP was introduced to achieve the specific capture and separation of targets without sample pretreatment. Using the MIP and PFC as recognition and signal conversion elements, respectively, the proposed self-powered biosensor showed a wide dynamic range of 0.01-1000 ng/mL with a detection limit of 0.73 pg/mL, which opened opportunities to design more novel self-powered biosensors and promoted its application in food safety and environmental monitoring.

Magnetic Nanobeads and De Novo Growth of Electroactive Polymers for Ultrasensitive microRNA Detection at the Cellular Level.

Detection of biomarkers at the cellular level can provide more accurate and comprehensive information that is important for early diagnosis of diseases and evaluation of new drugs. However, the interference of a large number of components in cells and the requirement of high sensitivity bring great challenges for their detection. Herein, a robust and enzyme-free electrochemical platform was proposed for microRNA-21 (miRNA-21) detection by integrating the efficient separation of magnetic nanobeads (MBs) with the multisignal amplification of strand displacement amplification (SDA) and electrochemically mediated atom transfer radical polymerization (eATRP). The eATRP is capable of de novo growth of a number of electroactive polymers on the electrode surface for signal amplification. Compared to simple hybridization, SDA and eATRP can enhance the signals by ∼35-fold, achieving high signal-to-noise ratio for low-abundant target detection. Owing to their superparamagnetism and strong magnetic response ability, MBs endow the method with excellent specificity and anti-interference ability to detect miRNA-21 in cells. Using MBs as capture carriers, SDA and eATRP for signal amplification, and gold nanoflower (AuNF)-modified electrodes as working electrodes, as low as 0.32 aM miRNA-21 was detected. Furthermore, the successful detection of miRNA-21 in cells indicated the great prospect of this method in the early diagnosis of cancers, life science research, and single-entity electrochemical detection.