Ultrasensitive and rapid detection of miRNA with three-way junction structure-based trigger-assisted exponential enzymatic amplification

Evaluation of miR-155 silencing using a molecular beacon in human lung adenocarcinoma cell line

Lung cancer (LC) is a leading cause of global cancer-related deaths, highlighting the development of innovative methods for biomarker detection improving the early diagnostics. microRNAs (miRs) alterations are known to be involved in the initiation and progression of human cancers and can act as biomarkers for diagnostics and treatment. Herein, we develop the application of molecular beacon (MB) technology to monitor miR-155-3p expression in human lung adenocarcinoma A549 cells without complementary DNA synthesis, amplification, or expensive reagents. Furthermore, we produced gold nanoparticles (AuNPs) for delivering antisense oligonucleotides into A549 cells to reduce miR-155-3p expression, which was subsequently detectable using the MB. The MB was designed and structural characterized by Förster Resonance Energy Transfer (FRET)-melting, Circular Dichroism (CD), Nuclear magnetic resonance (NMR), and fluorometric experiments, and then the hybridization conditions were optimized for an in vitro approach involving the detection of miR-155-3p in total RNA extracted from A549 cell line. The expression profile of miR-155-3p was obtained by RT-qPCR. The results demonstrated that MB was properly designed and showed efficacy in targeting miR-155-3p. Furthermore, a limit of detection down to nanomolar concentration was achieved and the specificity of the biosensor was proved. Moreover, the self-assembly of ASOs with AuNPs exhibited exceptional target specificity, effectively silencing miR-155-3p. Notably, compared to lipid-based transfection agent, AuNPs displayed superior silencing efficiency. We highlighted the ability of MB to detect changes in the target gene expression after gene silencing. Overall, this innovative approach represents a promising tool for detecting various biomarkers at the same time, with potential applications in clinical settings.

Three-way junction structure-mediated reverse transcription-free exponential amplification reaction for pathogen RNA detection

Since RNA is an important biomarker of many infectious pathogens, RNA detection of pathogenic organisms is crucial for disease diagnosis and environmental and food safety. By simulating the base mismatch during DNA replication, this study presents a novel three-way junction structure-mediated reverse transcription-free exponential amplification reaction (3WJ-RTF-EXPAR) for the rapid and sensitive detection of pathogen RNA. The target RNA served as a switch to initiate the reaction by forming a three-way junction (3WJ) structure with the ex-trigger strand and the ex-primer strand. The generated trigger strand could be significantly amplified through EXPAR to open the stem-loop structure of the molecular beacon to emit fluorescence signal. The proofreading activity of Vent DNA polymerase, in combination with the unique structure of 2+1 bases at the 3'-end of the ex-primer strand, could enhance the role of target RNA as a reaction switch to reduce non-specific amplification and ensure excellent specificity to differentiate target pathogen from those causing similar symptoms. Furthermore, detection of target RNA showed a detection limit of 1.0×104 copies/mL, while the time consumption was only 20 min, outperforming qRT-LAMP and qRT-PCR, the most commonly used RNA detection methods in clinical practice. All those indicates the great application prospects of this method in clinical diagnostic.

Target-initiated triplex signal amplification cascades for non-label and sensitive fluorescence sensing of microRNA

The aberrant expression of microRNAs (miRs) in cells is closely linked to the initiation and progression of various diseases. Sensitive monitoring of their level is hence vital for biomedical research and disease diagnosis. Herein, a highly sensitive and non-label fluorescence sensor based on multiple recycling signal amplification cascades is constructed for the detection of miR-21 in human sera. The presence of miR-21 initiates the primer-fueled target recycling process for the generation of many primer/hairpin templates for the subsequent auto-cycling primer extension (APE) amplification cycles, which result in the formation of lots of long-stem hairpins. The enzyme-based cleavage of such hairpins via polymerization/excision cycles further leads to the generation of abundant G-quadruplex strands, which associate with the thioflavin T (ThT) dye to emit remarkably magnified fluorescence for detecting miR-21 in the range of 1 pM-100 nM with a 0.32 pM detection limit without labeling the probes. Besides, the proposed assay can selectively discriminate miR-21 against other control molecules and realize the sensing of low levels of miR-21 in diluted sera. With features of high sensitivity via the triplex signal amplification cycles and simplicity in a non-label homogeneous manner, our miR sensing protocol can be a robust means for detecting various nucleic acids for the early diagnosis of diseases.

Platelet Microparticle-Derived MiR-320b Inhibits Hypertension with Atherosclerosis Development by Targeting ETFA

Hypertension and atherosclerosis often occur simultaneously. This study aimed to explore the role and mechanism of platelet microparticle (PMP) -derived microRNA-320b (miR-320b) in patients with hypertension accompanied by atherosclerosis.We collected samples from 13 controls without hypertension and atherosclerosis and 20 patients who had hypertension accompanied by atherosclerosis. In vitro, platelets were activated by Thrombin receptor-activating peptide to produce PMPs. HUVECs were induced by CoCl2 to mimic a hypoxic environment in vitro. RT-qPCR was employed to detect the expression levels of CD61, miR-320b, and ETFA. The protein expression level of ETFA was evaluated via Western blotting. Furthermore, 3- (4,5-dimethylthiazol-2-yl) -2,5-diphenyltetrazolium bromide, 5-ethynyl-2'-deoxyuridine, and wound healing assays were employed to assess the proliferation and migration of HUVECs. Enzyme-linked immunosorbent assay was used to measure the oxidative stress and inflammation-related factor expression.The expression of miR-320b was reduced in both platelets and PMPs but increased in plasma. MiR-320b promoted CoCl2-induced HUVEC viability, proliferation, and migration. The levels of the oxidative stress factors SOD and GSH as well as the inflammatory factor IL-10 were elevated in the CoCl2 + miR-320b mimics group compared with both the CoCl2 + mimics NC and CoCl2 groups. Conversely, the levels of the oxidative stress factors MDA and ROS as well as the inflammatory factors IL-6, TNF-α, and IL-1β were decreased. These results were regulated by miR-320b targeting ETFA.PMP-derived miR-320b inhibits the development of hypertension accompanied by atherosclerosis by targeting ETFA.

Enhancement of Escherichia coli Ribonuclease R Cytosine-Sensitive Activity by Single Amino Acid Substitution

Exoribonucleases are frequently used as nuclei acids detection tools for their sequences, modifications, and structures. Escherichia coli ribonuclease R (EcR) is the prototypical exoribonuclease of the RNase II/RNB family degrading RNA in the 3'-5' direction. Different from RNase II, EcR is capable of degrading structured RNA efficiently, which makes it a potential analysis tool for various RNA species. In this work, we examined the nuclease activity of EcR degrading a series of RNA substrates with various sequences. Our biochemical work reveals that EcR is significantly sensitive to cytosine compared with other bases when catalyzing RNA degradation. EcR shows higher cytosine sensitivity compared to its homolog RNase II when degrading RNAs, and the hydrolysis process of EcR is transiently halted and produces apparent intermediate product when the 1-nt upstream of C is A or U, or G. Furthermore, the substitution of glycine with proline (G273P) in EcR enhances its cytosine sensitivity. These findings expand our understanding of EcR enzymatic activities. The EcR G273P mutant bearing higher cytosine sensitivity could help enrich cytosine trails in RNAs and will have potential implications in the detection and analysis of various RNA species especially small RNAs in biological and clinical samples.

Biomineralized zeolitic imidazolate framework-8 nanoparticles enable polymerase/endonuclease synergetic amplification reaction in living cells for sensitive microRNA imaging

In this work, we have implemented a polymerase and endonuclease synergetic amplification reaction in living cells for intracellular miRNA imaging by using biomineralized ZIF-8 NPs.

A compact fiber-integrated optofluidic platform for highly specific microRNA Förster resonance energy transfer detection

MicroRNAs (miRNAs) have attracted extensive interest as promising biomarkers for the profiling of diseases. However, quantitative measurement of miRNAs presents a significant challenge in biochemical studies. In this work, we developed an innovative optofluidic platform to perform a rapid, simple, quantitative and high-specificity miRNA assay using the Förster resonance energy transfer (FRET) principle. A novel three-way junction FRET probe was proposed to enable rapid and enzyme-free miRNA detection. Using this platform, we performed one-step, amplification-free miRNA detection with simple device operation and achieved miRNA identification at a low concentration. The detection system could achieve high specificity for discrimination of three-base mismatches, and the sample volume was significantly reduced, favorable for low-level miRNA detection in material-limited samples. The establishment of a compact, low-cost, highly sensitive and selective miRNA analysis platform provides a valuable tool for point-of-care diagnosis.

Hairpin DNA-Mediated isothermal amplification (HDMIA) techniques for nucleic acid testing

Nucleic acid detection is of great importance in a variety of areas, from life science and clinical diagnosis to environmental monitoring and food safety. Unfortunately, nucleic acid targets are always found in trace amounts and their response signals are difficult to be detected. Amplification mechanisms are then practically needed to either duplicate nucleic acid targets or enhance the detection signals. Polymerase chain reaction (PCR) is one of the most popular and powerful techniques for nucleic acid analysis. But the requirement of costly devices for precise thermo-cycling procedures in PCR has severely hampered the wide applications of PCR. Fortunately, isothermal molecular reactions have emerged as promising alternatives. The past decade has witnessed significant progress in the research of isothermal molecular reactions utilizing hairpin DNA probes (HDPs). Based on the nucleic acid strand interaction mechanisms, the hairpin DNA-mediated isothermal amplification (HDMIA) techniques can be mainly divided into three categories: strand assembly reactions, strand decomposition reactions, and strand creation reactions. In this review, we introduce the basics of HDMIA methods, including the sensing principles, the basic and advanced designs, and their wide applications, especially those benefiting from the utilization of G-quadruplexes and nanomaterials during the past decade. We also discuss the current challenges encountered, highlight the potential solutions, and point out the possible future directions in this prosperous research area.

An integrated fluorescence biosensor for microRNA detection based on exponential amplification reaction-triggered three-dimensional bipedal DNA walkers

Sensitive and specific miRNA detection is essential for the early cancer diagnosis. In this work, we design a fluorescent microRNA biosensor based on exponential amplification reaction (EXPAR) and nicking endonuclease-powered three-dimensional (3-D) bipedal DNA walkers (BDW). Target microRNA initiates EXPAR with the help of polymerase and nicking endonuclease to generate the large number of BDW in solution. The newly generated BDW can be continuously assembled onto polystyrene microsphere track co-modified with fluorescence-labeled DNA strand. Thus, in the presence of nicking endonuclease, the walking machine is activated to produce enhanced fluorescent signal in the supernatant. Besides, we prove that BDW holds the faster walking speed than single-legged DNA walker (SDW) based on comparative study. Under optimal conditions, the proposed amplification method owns a wide linear range from 10 fM to 5 nM with a detection limit down to 5.2 fM. The reaction time of the assay takes about 70 min. The combination of enzyme-assisted EXPAR in solution and enzyme-powered BDW on particle significantly increases the signal amplification efficiency and improves the detection sensitivity. Therefore, our method has enormous potential for the application of BDW-related biosensors.

Expanding the analytical applications of nucleic acid hybridization using junction probes

Nucleic acid hybridization is crucial in target recognition with respect to in vitro and in vivo nucleic acid biosensing. Conventional linear probes and molecular beacons encounter challenges in multiplexing and specific recognition of intractable nucleic acids. Advances in nucleic acid nanotechnologies have resulted in a set of novel structural probes: junction probes (JPs), which make full use of the advantages of specificity, stability, programmability and predictability of Watson-Crick base pairing. In recent years, junction probes have been regularly implemented in constructing systems related to biosensing, synthetic biology and gene regulation. Herein, we summarize the latest advances in JP designs as potential nucleic acid biosensing systems and their expansive applications, and provide some general guidelines for developing JP based sensing strategies for implementation of such systems.

Sensitive detection of microRNA using a label-free copper nanoparticle system with polymerase-based signal amplification

The abnormal expression of microRNAs (miRNAs) has been reported in many diseases, so it is of great interest to develop simple and accurate methods for the detection and analysis of miRNA expression. We have developed a novel biosensor to detect miRNAs. This method is based on a polymeric double-stranded DNA (dsDNA) copper nanoparticle (CuNP) template that is synthesised by a polymerase. When Cu²⁺ and ascorbic acid are added to the system, the dsDNA template (which is rich in A-T bases) promotes the formation of CuNPs, resulting in high fluorescence intensity. This system provides sensitive analysis of miRNA expression with a limit of detection down to 17.8 pmol/L, due to significant changes in the fluorescence signal of the system before and after the addition of the target. The linear range between F₀-F and concentration of miR-122 is 80.0 pmol/L to 4.50 nmol/L, and the recovery rate in spiked HepG2 cell lysates is 93.33-102.53%. This method expands the applications of fluorescent DNA-CuNPs in the field of biosensor analysis, and can be used to detect and analyse any miRNA marker by changing the target recognition sequence. Graphical abstract A label-free dsDNA-CuNP-based and enzyme-assisted signal amplification method for microRNA is constructed.

Aptamer based high throughput colorimetric biosensor for detection of staphylococcus aureus

To develop a high throughput colorimetric biosensor for detection of Staphylococcus aureus (SA) based on specific aptamer and catalysis of dsDNA-SYBR Green I (SG I) complex. SA specific aptamer was immobilized on a 96-well plate by hybridization with the capture probe anchored on the plate surface through streptavidin-biotin binding. In presence of SA, the aptamer was dissociated from the capture probe-aptamer duplex due to the stronger interaction between the aptamer and SA. The consequent single-strand capture probe could be hybridized with a three-way junction (TWJ) probe. With the presence of SG I, the dsDNA-SG I complex catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) under photo-irradiation, producing sensitive photo-catalyzed colorimetric response to SA. Under the optimal conditions, the proposed method could directly detect SA with the limit of detection (LOD) at 81 CFU mL⁻¹ in PBS buffer in 5.5 hours, which demonstrated the sensitive and fast quantification of target pathogenic bacteria. The method showed weak colorimetric signal to Escherichia coli and Pseudomonas aeruginosa, indicating the high specificity for SA. In addition, the method can simultaneously detect 96 samples which can be used for high throughput analysis. The designed method may become a powerful tool for pathogenic microorganisms screening in clinical diagnostics, food safety and environmental monitoring.

Physical and chemical template-blocking strategies in the exponential amplification reaction of circulating microRNAs

The detection of circulating miRNA through isothermal amplification wields many attractive advantages over traditional methods, such as reverse transcription RT-qPCR. However, it is challenging to control the background signal produced in the absence of target, which severely hampers applications of such methods for detecting low abundance targets in complex biological samples. In the present work, we employed both the cobalt oxyhydroxide (CoOOH) nanoflakes and the chemical modification of hexanediol to block non-specific template elongation in exponential amplification reaction (EXPAR). Adsorption by the CoOOH nanoflakes and the hexanediol modification at the 3' end effectively prevented no-target polymerization on the template itself and thus greatly improved the performance of EXPAR, detecting as low as 10 aM of several miRNA targets, including miR-16, miR-21, and miR-122, with the fluorescent DNA staining dye of SYBR Gold™. Little to no cross-reactivity was observed from the interfering strands present in 10-fold excess. Besides contributing to background reduction, the CoOOH nanoflakes strongly adsorbed nucleic acids and isolated them from a complex sample matrix, thus permitting successful detection of the target miRNA in the serum. We expect that simple but sensitive template-blocking EXPAR could be a valuable tool to help with the discovery and validation of miRNA markers in biospecimens. Graphical abstract.

Three-way junction-induced isothermal amplification for nucleic acid detection

We, herein, describe a three-way junction (3WJ)-induced isothermal amplification (ThIsAmp) reaction for target nucleic acid detection. In this strategy, target nucleic acid induces the formation of 3WJ structure by associating a specially designed ThIsAmp template and ThIsAmp primer. Upon the formation of 3WJ structure, ThIsAmp primer is subjected to continuously repeated extension and nicking reaction by the combined activities of DNA polymerase and nicking endonuclease, consequently producing a large number of trigger strands. The trigger strands then initiate two separate but interconnected pathways by binding to either 3' overhang of ThIsAmp template within the 3WJ structure or free ThIsAmp template. As a consequence, a large number of final double-stranded DNA products are produced under an isothermal condition, which can be monitored in real-time by detecting the fluorescence intensity resulting from SYBR Green I staining. Based on this principle, we successfully detected target DNA down to 78.1 aM with excellent specificity. The sophisticated design principle employed in this work would provide great insight for the development of self-operative isothermal amplifying system enabling target nucleic acid detection.

Direct and sensitive detection of circulating miRNA in human serum by ligase-mediated amplification

MicroRNAs (miRNA) involve in regulating different physiological processes whose dysregulation is associated with a wide range of diseases including cancers, diabetes and cardiovascular problems. Herein, we report a direct, sensitive and highly selective detection assay for circulating microRNA (miRNA). This detection strategy employs magnetic nanoparticles as the reaction platform which can not only allow online pre-concentration and selective separation but also integrates ligation reaction with amplification to enhance the sensitivity of the detection assay. With the presence of the target miRNA, the locked nucleic acid (LNA)-modified molecular beacon (MB) opens up, exposing the binding sites at two ends. The 3'- and 5'-end of the MB responsible for the attachment onto the magnetic nanoparticles, and reporting probe for the attachment of the pair of amplification probes respectively. The ligase ligate RNA to DNA enhance the amplification efficiency. Upon labelled with intercalating fluorophores (YOYO-1) on the hybrids, the quantification of the target miRNA was determined by measuring the fluorescence intensity. A detection limit of 314 fM was achieved with trace amount of sample consumption (~20 μL). As a proof of concept, miRNA-149 was chosen as the target miRNA. This assay is capable of discriminating single-base and reliably quantifying circulating miRNA-149 in both healthy and cancer patient's serums. The result obtained was comparable with that of quantitative reverse transcription polymerase chain reaction (qRT-PCR), suggesting that this direct and sensitive assay can be served as a promising, non-invasive tool for early diagnosis of breast cancer and colorectal cancer.

Smart engineering of a dual-DNA machine with a high signal-to-noise ratio for one-pot robust and sensitive miRNA signaling

A target triggered dual-DNA machine composed of RCA and SDA was developed for robust and one-pot determination of miRNA.

Ultrasensitive electrochemical detection of Hg2+ based on an Hg2+-triggered exonuclease III-assisted target recycling strategy

In the present work, a simple, rapid, isothermal, and ultrasensitive homogeneous electrochemical biosensing platform for target Hg2+ detection was developed on the basis of an exonuclease III (Exo III)-aided target recycling amplification strategy. In the assay, a label-free hairpin probe (HP1) was ingeniously designed, containing a protruding DNA fragment at the 3'-termini as the recognition unit for target Hg2+. Also, the DNA fragment in the loop region and 5'-termini (Helper) could be used when a secondary target analog is introduced, but it is caged in the stem region of HP1 when without such a target. The produced secondary target Helper opened the methylene blue (MB)-labeled hairpin probe (HP2) and triggered the Exo III cleavage process, accompanied with the secondary target recycling. This accordingly resulted in the autonomous reduction of the electroactive material MB on the electrode, inducing a distinct decrease in the electrochemical signal. The current developed homogeneous strategy provides a means for the ultrasensitive electrochemical detection of Hg2+ down to the 227 pM level, with high selectivity. It could be further used as a general autocatalytic and homogeneous strategy toward the detection of a wide spectrum of analytes and may be associated with more analytical techniques.

A Novel Design Combining Isothermal Exponential Amplification and Gold-Nanoparticles Visualization for Rapid Detection of miRNAs

MicroRNAs (miRNAs) play important roles in a wide range of biological processes, and their aberrant expressions are associated with various diseases. The levels of miRNAs can be useful biomarkers for cellular events or disease diagnosis; thus, sensitive and selective detection of microRNAs is of great significance in understanding biological functions of miRNAs, early-phase diagnosis of cancers, and discovery of new targets for drugs. However, traditional approaches for the detection of miRNAs are usually laborious and time-consuming, with a low sensitivity. Here, we develop a simple, rapid, ultrasensitive colorimetric assay based on the combination of isothermal Exponential Amplification Reaction (EXPAR) and AuNP-labeled DNA probes for the detection of miRNAs (taking let-7a as a model analyte). In this assay, the presence of let-7a is converted to the reporter Y through EXPAR under isothermal conditions. The subsequent sandwich hybridization of the reporter Y with the AuNP-labeled DNA probes generates a red-to-purple color change. In other words, if the reporter Y is complementary to the AuNP-labeled DNA probes, the DNA-functionalized AuNPs will be aggregated, resulting in the change of solution color from red to purple/blue, while when the AuNP-labeled DNA probes are mismatched to the reporter Y, the solution remains red. This assay represents a simple, time-saving technique, and its results can be visually detected with the naked eye due to the colorimetric change. The method provides superior sensitivity, with a detection limit of 4.176 aM over a wide range from 1 nM to 1 aM under optimal conditions. The method also shows high selectivity for discriminating even single-nucleotide differences between let-7 miRNA family members. Notably, it is comparable to the most sensitive method reported to date, thus providing a promising alternative to standard approaches for the direct detection of let-7a miRNA. Importantly, through combination with specific templates, different miRNAs can be converted to the same reporter Y, which can hybridize with the same set of AuNP-labeled DNA probes to form sandwich hybrids. The color change of the solution can be observed in the presence of the target miRNA. This technique has potential as a routine method for assessing the levels of miRNAs, not only for let-7, but also for various miRNAs in the early phase of cancers. In addition, it can be a useful tool in biomedical research and clinical diagnosis, as well as diagnosis or surveillance programs in field conditions.

Rapid and label-free fluorescence bioassay for microRNA based on exonuclease III-assisted cycle amplification

A new assay for the rapid and simple detection of microRNA based on G-quadruplex and Exonuclease III (ExoIII) dual signal amplification was constructed.

Isothermal amplification detection of miRNA based on the catalysis of nucleases and voltammetric characteristics of silver nanoparticles

MiRNAs are a fascinating kind of biomolecule due to their vital functions in gene regulation and potential value as biomarkers for serious diseases including cancers. Exploiting convenient and sensitive methods for miRNA expression assays is imperative. In this study, we employ an exonuclease (RecJ_f) and a nicking endonuclease (Nt.BbvCI) to catalyse isothermal reactions for the amplified detection of miRNA. The degree of cyclical enzymatic amplification depends on the initial target miRNA level, which can determine the density of DNA probes bound on the electrode surface. Since DNA probes with an amino group at the 3' end are able to locate silver nanoparticles on the electrode, which provide intense stripping responses, the sensitive quantification of miRNA can be achieved. The proposed method has a limit of detection as low as 35 aM, with remarkable specificity, which offers a new approach for investigating miRNA networks and for clinical diagnosis applications.

An Exonuclease I-Based Quencher-Free Fluorescent Method Using DNA Hairpin Probes for Rapid Detection of MicroRNA

MicroRNAs (miRNAs) act as biomarkers for the diagnosis of a variety of cancers. Since the currently used methods for miRNA detection have limitations, simple, sensitive, and cost-effective methods for the detection of miRNA are required. This work demonstrates a facile, quencher-free, fluorescence-based analytical method for cost-effective and sensitive detection of miRNA using a super 2-aminopurine (2-AP)-labeled hairpin probe (HP) and exonuclease I activity. Specifically, the fluorescence of 2-AP is strongly quenched when it is incorporated within DNA. In the presence of a target miRNA, HP attains an open conformation by hybridizing with the target miRNA to form a double-stranded structure with a protruding 3′-terminus. Next, the digestion of the protruding 3′-terminus is triggered by exonuclease I, during which 2-AP is released free in solution from the DNA, thereby increasing fluorescence. This method is highly sensitive, with a detection limit of 0.5 nM—10 times lower than a previously reported quencher-free fluorescence method. Furthermore, this method has potential applications in clinical diagnosis and biomedical research.

High-sensitive surface plasmon resonance microRNA biosensor based on streptavidin functionalized gold nanorods-assisted signal amplification

Herein, a facile and sensitive microRNA (miRNA) biosensor was designed by using interfacial biotinylated thiolated DNA molecular beacon (MB) as probe and streptavidin functionalized gold nanorods (Stre-GNRs) as tag for the enhanced surface plasmon resonance (SPR) signal. The MB probe with two terminals labeled with biotin and thiol groups, respectively, was modified on the gold film via thiol-gold interaction. Upon hybridization with the target, the biotinylated group became accessible to the Stre-GNRs. The introduction of the Stre-GNRs tag to the gold film produced strong SPR signal for detection. Our work has illustrated that the plasmonic field extension generated from the gold film to GNRs and the mass increase due to the GNRs have led to drastic sensitivity enhancement. Under optimal conditions, this proposed approach allowed detection of miRNA with the limit of detection (LOD) down to 0.045 pM. The results have shown that the MB probe functionalized sensing film, together with streptavidin-conjugated GNRs, was readily served as a plasmonic coupling partner that can be used as a powerful ultrasensitive sandwich assay for miRNA detection, and GNRs were readily served as promising amplification labels in SPR sensing technology.

Branched RCA coupled with a NESA-based fluorescence assay for ultrasensitive detection of miRNA

This work is the first report that branched-RCA coupled with NESA has been used for fluorescence assay of miRNA.

A three-way junction structure-based isothermal exponential amplification strategy for sensitive detection of 3′-terminal 2′-O-methylated plant microRNA

A versatile and general 3WJ-EXPAR strategy is developed for the sensitive detection of 3′-terminal 2′-O-methylated plant microRNAs.

Live Cell MicroRNA Imaging Using Exonuclease III-Aided Recycling Amplification Based on Aggregation-Induced Emission Luminogens

Enzyme-assisted detection strategies of microRNAs (miRNAs) in vitro have accomplished both great sensitivity and specificity. However, low expression of miRNAs and a complex environment in cells induces big challenges for monitoring and tracking miRNAs in vivo. The work reports the attempt to carry miRNA imaging into live cells, by enzyme-aided recycling amplification. We utilize facile probes based yellow aggregation-induced emission luminogens (AIEgens) with super photostable property but without quencher, which are applied to monitor miRNAs not only from urine sample extracts (in vitro) but also in live cells (in vivo). The assay could distinguish the cancer patients' urine samples from the healthy urine due to the good specificity. Moreover, the probe showed much higher fluorescence intensity in breast cancer cells (MCF-7) (miR-21 in high expression) than that in cervical cancer cells (HeLa) and human lung fibroblast cells (HLF) (miR-21 in low expression) in more than 60 min, which showed the good performance and super photostability for the probe in vivo. As controls, another two probes with FAM/Cy3 and corresponding quenchers, respectively, could perform miRNAs detections in vitro and parts of in vivo tests but were not suitable for the long-term cell tracking due to the photobleach phenomena, which also demonstrates that the probe with AIEgens is a potential candidate for the accurate identification of cancer biomarkers.