Lab in a Tube: Ultrasensitive Detection of MicroRNAs at the Single-Cell Level and in Breast Cancer Patients Using Quadratic Isothermal Amplification

MnO2 Nanotube-Based NanoSearchlight for Imaging of Multiple MicroRNAs in Live Cells

Sensitive assay and imaging of multiple low-abundance microRNAs (miRNAs) in living cells remain a grand challenge. Herein, based on polyelectrolyte-induced reduction, a facile approach has been proposed to synthesize novel MnO2 nanotubes. Owing to the remarkably strong fluorescence quenching ability, low cytotoxicity, and excellent colloid stability, the as-prepared MnO2 nanotubes showed great potential for simultaneous detection and imaging of multiple miRNAs in vitro and in situ in living cells for the first time. Besides, MnO2 nanotubes can be reduced to Mn2+ by intracellular acid pH or glutathione, which may serve as an activatable contrast reagent for MRI. Therefore, the MnO2 nanotube-based probes, termed "NanoSearchlight", provide a promising, multimodal imaging tool for precise and accurate diagnosis and prognosis of cancers.

A Quasi-direct LC-MS/MS-based Targeted Proteomics Approach for miRNA Quantification via a Covalently Immobilized DNA-peptide Probe

MicroRNAs (miRNAs) play a vital role in regulating gene expression and are associated with a variety of cancers, including breast cancer. Their distorted and unique expression is a potential marker in clinical diagnoses and prognoses. Thus, accurate determination of miRNA expression levels is a prerequisite for their applications. However, the assays currently available for miRNA detection typically require pre-enrichment, amplification and labeling steps, and most of the assays are only semi-quantitative. Therefore, we developed a quasi-direct liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based targeted proteomics approach to quantify target miRNA by innovatively converting the miRNA signal into the mass response of a reporter peptide via a covalently immobilized DNA-peptide probe. Specifically, the probe containing the targeted proteomics-selected substrate/reporter peptide, GDRAVQLGVDPFR/AVQLGVDPFR, and the DNA sequence complementary to the target miRNA (i.e., miR-21) was first immobilized on APMTS modified silica nanoparticles using PDITC. After the immobilized probe was recognized and hybridized with the target miRNA, the excess probe was degraded using MBN and followed by a trypsin digestion of the hybrids. The reporter peptide was released and quantified using LC-MS/MS. The obtained LOQ was 5 pM. Finally, the developed assay was used for the quantitative analysis of miR-21 in breast cells and tissue samples.

Double-loop hairpin probe and doxorubicin-loaded gold nanoparticles for the ultrasensitive electrochemical sensing of microRNA

An electrochemical microRNA (miRNA) analysis platform by combining double-loop hairpin probe (DHP) and doxorubicin-loaded gold nanoparticles (AuNPs@Dox) for ultrasensitive miRNA detection is proposed. Firstly, we here report a DHP that is simultaneously engineered to incorporate a miRNA recognition sequence, an output segment and output's complementary fragment. The important aspect of this hairpin probe is that it would not be degraded by duplex specific nuclease (DSN) and circumvents elaborately chemical modification disadvantages encountered by classic molecular beacon. For the DHP-based DSN signal amplification system, DHP hybridizes with target miRNA to form DNA-miRNA heteroduplexes, and the DSN can hydrolyze the DNA in the heteroduplexes structure selectively, while released target miRNA strand can initiate another cycle resulting in a significant signal amplification and the accumulated output segments could be responsible for strand displacement on the electrode directly. Furthermore, a great deal of doxorubicin (Dox) are loaded on the gold nanoparticles (AuNPs) to fabricate the AuNPs@Dox biocomposites that could magnify the electrochemical signal and enable the ultrasensitive analysis of miRNA. As a result, the miRNA was capable of being detected in a limit of 0.17pM and other kinds of miRNA were discriminated facilely by this method. The described DHP as a toolbox and the nano-biocomposites as a novel signal material would not only promote the design of electrochemical biosensors but also open a good way to promote the establishment of test method in malignant tumors.

Multifunctional substrate of label-free electrochemical immunosensor for ultrasensitive detection of cytokeratins antigen 21-1

Poly(thionine)-Au, a novel multifunctional substrate with excellent redox signal, enzyme-like activity, and easy antibody immobilisation, was synthesised using HAuCl₄ as the oxidising agent and thionine as the monomer. The prepared poly(thionine)-Au composite exhibited an admirable electrochemical redox signal at -0.15 V and excellent H₂O₂ catalytic ability. In addition, gold nanoparticles in this composite were found to directly immobilise antibodies and further improve conductivity. In addition, a label-free electrochemical immunosensor was developed using poly(thionine)-Au as the sensing substrate for ultrasensitive detection of cytokeratin antigen 21-1 (CYFRA 21-1), an immunoassay found in human serum. The prepared immunosensor showed a wide liner range from 100 ng mL^-1 to 10 fg mL^-1 and an ultralow detection limit of 4.6 fg mL^-1 (the ratio of signal to noise (S/N) = 3). Additionally, this method was used to analyse human serum samples and yielded results consistency with those of ELISA, implying its potential application in clinical research. The poly(thionine)-Au composite can be easily extended to other polymer-based nanocomposites, which is significant for other electrochemical immunoassays.

Isothermal Amplification for MicroRNA Detection: From the Test Tube to the Cell

MicroRNAs (miRNAs) are a class of small noncoding RNAs that act as pivotal post-transcriptional regulators of gene expression, thus involving in many fundamental cellular processes such as cell proliferation, migration, and canceration. The detection of miRNAs has attracted significant interest, as abnormal miRNA expression is identified to contribute to serious human diseases such as cancers. Particularly, miRNAs in peripheral blood have recently been recognized as important biomarkers potential for liquid biopsy. Furthermore, as miRNAs are expressed heterogeneously in different cells, investigations into single-cell miRNA expression will be of great value for resolving miRNA-mediated regulatory circuits and the complexity and heterogeneity of miRNA-related diseases. Thus, the development of miRNA detection methods, especially for complex clinic samples and single cells is in great demand. In this Account, we will present recent progress in the design and application of isothermal amplification enabling miRNA detection transition from the test tube to the clinical sample and single cell, which will significantly advance our knowledge of miRNA functions and disease associations, as well as its translation in clinical diagnostics. miRNAs present a huge challenge in detection because of their extremely short length (∼22 nucleotides) and sequence homology (even with only single-nucleotide variation). The conventional golden method for nucleic acid detection, quantitative PCR (qPCR), is not amenable to directly detecting short RNAs and hardly enables distinguishing between miRNA family members with very similar sequences. Alternatively, isothermal amplification has emerged as a powerful method for quantification of nucleic acids and attracts broad interest for utilization in developing miRNA assays. Compared to PCR, isothermal amplification can be performed without precise control of temperature cycling and is well fit for detecting short RNA or DNA. We and other groups are seeking methods based on isothermal amplification for detecting miRNA with high specificity (single-nucleotide resolution) and sensitivity (detection limit reaching femtomolar or even attomolar level). These methods have recently been demonstrated to quantify miRNA in clinical samples (tissues, serum, and plasma). Remarkably, attributed to the mild reaction conditions, isothermal amplification can be performed inside cells, which has recently enabled miRNA detection in single cells. The localized in situ amplification even enables imaging of miRNA at the single-molecule level. The single-cell miRNA profiling data clearly shows that genetically identical cells exhibit significant cell-to-cell variation in miRNA expression. The leap of miRNA detection achievements will significantly contribute to its full clinical adoption and translation and give us new insights into miRNA cellular functions and disease associations.

DNA nanomachine-based regenerated sensing platform: a novel electrochemiluminescence resonance energy transfer strategy for ultra-high sensitive detection of microRNA from cancer cells

The construction of DNA nanomachines holds great significance in the development of DNA nanostructures; however, the real application of nanomachines is still in its early stage. Moreover, one-step regenerated sensing platforms for the detection of biomarkers in the current research remain a practical challenge. Herein, a novel electrochemiluminescence resonance energy transfer (ERET) strategy between Alexa Flour 488 (AF 488), which is a type of small molecule dye, as the donor and CdSe@ZnS quantum dots (QDs) as the acceptor, which easily enter the cells, has been reported and was applied for the construction of a DNA nanomachine-based regenerated biosensor for the ultra-high sensitive determination of cancer cells without any enzyme. First, a dual amplification strategy, including target recycling and signal transformation, was employed to achieve the conversion of a small number of miRNAs into a large amount of universal DNA reporters. Initially, the DNA tweezer was kept in the "off" state with two arms labeled with QDs and AF488, respectively. Second, in the presence of DNA reporters, the tweezer transformed to the "on" state through the hybridization of the reporter DNA and exposed the arms of the tweezer. Simultaneously, QDs and AF488 on the two arms were close enough to generate ERET, which remarkably increased the ECL intensity of the QDs. Impressively, the sensor could be regenerated by a one-step strand displacement and could be cycled for more than seven times. Owing to the dual amplification strategy and the high efficiency of the ERET between the QDs and AF488, the proposed biosensor performs in the linear range from 10 pM to 0.1 fM with a detection limit of 0.03 fM for miRNA determination, and the monitoring of different cancer cells was also achieved. Moreover, the elaborated biosensor can also realize the sensitive detection of Pb²⁺, which indicates that it can be potentially used for field environmental analysis and monitoring, thus offering a new modular platform for the construction of functional DNA nanomachines in the ultra-high sensitive analysis of promising biomarkers and toxic metals.

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.

Exonuclease-assisted target recycling amplification for label-free chemiluminescence assay and molecular logic operations

A versatile exonuclease-assisted target recycling amplification strategy is demonstrated to achieve label-free chemiluminescence detection of DNA and construction of a series of two-input molecular logic gates.

Liposome-encoded magnetic beads initiated by padlock exponential rolling circle amplification for portable and accurate quantification of microRNAs

In this work, we propose a strategy for glucoamylase-encapsulated liposome-encoded magnetic beads initiated by padlock exponential rolling circle amplification (P-ERCA) for portable and accurate quantification of miRNA by using a glucometer (GM) for readout.

One-step detection of microRNA with high sensitivity and specificity via target-triggered loop-mediated isothermal amplification (TT-LAMP)

A target-triggered loop-mediated isothermal amplification (TT-LAMP) mechanism is developed for simple one-step but highly sensitive detection of microRNAs.

The development of nanostructure assisted isothermal amplification in biosensors

Developing simple and inexpensive methods to ultrasensitively detect biomarkers is important for medical diagnosis, food analysis and environmental security. In recent years, isothermal amplifications with sensitivity, high speed, specificity, accuracy, and automation have been designed based on interdisciplinary approaches among chemistry, biology, and materials science. In this article, we summarize the advances in nanostructure assisted isothermal amplification in the past two decades for the detection of commercial biomarkers, or biomarkers extracted from cultured cells or patient samples. This article has been divided into three parts according to the ratio of target-to-signal probe in the detection strategy, namely, the N : N amplification ratio, the 1 : N amplification ratio, and the 1 : N(2) amplification ratio.

In-flow real-time detection of spectrally encoded microgels for miRNA absolute quantification

We present an in-flow ultrasensitive fluorescence detection of microRNAs (miRNAs) using spectrally encoded microgels. We researched and employed a viscoelastic fluid to achieve an optimal alignment of microgels in a straight measurement channel and applied a simple and inexpensive microfluidic layout, allowing continuous fluorescence signal acquisitions with several emission wavelengths. In particular, we chose microgels endowed with fluorescent emitting molecules designed for multiplex spectral analysis of specific miRNA types. We analysed in a quasi-real-time manner circa 80 microgel particles a minute at sample volumes down to a few microliters, achieving a miRNA detection limit of 202 fM in microfluidic flow conditions. Such performance opens up new routes for biosensing applications of particles within microfluidic devices.

Self-assembled silk fibroin nanoparticles loaded with binary drugs in the treatment of breast carcinoma

Self-assembled nanoparticles of the natural polymer, silk fibroin (SF), are a very promising candidate in drug delivery due to their biocompatible and biodegradable properties. In this study, SF nanoparticles loaded with 5-fluorouracil (5-FU) and curcumin with size 217±0.4 nm and with a loading efficacy of 45% and 15% for 5-FU and curcumin, respectively, were prepared. The in vitro release effect of 5-FU and curcumin from nanoparticles was evaluated as ~100% and ~5%, respectively. It has been revealed that the application of such a nanodrug can increase the level of reactive oxygen species, which in turn induces apoptosis of cancer cells in vitro. Animal studies have shown that tumors could be noticeably reduced after being injected with the drug-entrapped nanoparticles. More apoptotic cells were found after 7 days of treatment with SF nanoparticles by a hematoxylin–eosin staining assay. These results demonstrate the future potential of nanoparticle-loaded binary drugs in the treatment of breast cancer.

Sensitive detection of miRNA by using hybridization chain reaction coupled with positively charged gold nanoparticles

Positively charged gold nanoparticles (+)AuNPs can adsorb onto the negatively charged surface of single-stranded DNA (ssDNA) or double-stranded DNA (dsDNA). Herein, long-range dsDNA polymers could form based on the hybridization chain reaction (HCR) of two hairpin probes (H₁ and H₂) by using miRNA-21 as an initiator. (+)AuNPs could adsorb onto the negatively charged surface of such long-range dsDNA polymers based on the electrostatic adsorption, which directly resulted in the precipitation of (+)AuNPs and the decrease of (+)AuNPs absorption spectra. Under optimal conditions, miRNA-21 detection could be realized in the range of 20 pM-10 nM with a detection limit of 6.8 pM. In addition, (+)AuNPs used here are much more stable than commonly used negatively charged gold nanoparticles ((−)AuNPs) in mixed solution that contained salt, protein or other metal ions. Importantly, the assay could realize the detection of miRNA in human serum samples.

Naked eye detection of multiple tumor-related mRNAs from patients with photonic-crystal micropattern supported dual-modal upconversion bioprobes

We have designed a biochip-based mRNA detection device by combining a hydrophilic–hydrophobic micropattern with upconversion luminescence (UCL) probes.

Development of a portable device for the detection of multiple mRNAs is a significant need in the early diagnosis of cancer. We have designed a biochip-based mRNA detection device by combining a hydrophilic–hydrophobic micropattern with upconversion luminescence (UCL) probes. The device achieves highly sensitive detection, using the naked eye, of multiple mRNAs among patient samples. The high sensitivity is attributed to enrichment of the target concentration and a fluorescence enhancement effect. In addition, since the photonic crystal (PC) dot biochip is functionalized with dual-wavelength excitation UCL probes, two kinds of mRNAs in the heterogeneous biological samples are detected simultaneously, and the corresponding luminescence signals are captured using an unmodified camera phone. The biochip-based mRNA detection device reported here demonstrates that multiple mRNAs extracted from patient samples can be simultaneously and sensitively detected in a visual way without sophisticated instrumentation. Therefore, this device is promising for real-time detection of multiple biomarkers in patient samples, and it is anticipated that it will provide a powerful tool for convenient early diagnosis of cancer.

Cascaded multiple amplification strategy for ultrasensitive detection of HIV/HCV virus DNA

Ultrasensitive detection of HIV and HCV virus DNA is of great importance for early accurate diagnostics and therapy of HIV virus-infected patients. Herein, to our best knowledge, it is the first to use DNA cascaded multiple amplification strategy for ultrasensitive detection of HIV virus DNA with G-quadruplex-specific fluorescent or colorimetric probes as signal carriers. The developed strategy also exhibited universal applicability for HCV virus DNA detection. After reaction for about 4h, high sensitivity and specificity can be achieved at both fluorescent and colorimetric strategies (limit of detection (LOD) of 10 fM and 0.5pM were reached for fluorescent and colorimetric detection, respectively). And the single-based mismatched DNA even can be distinguished by naked eyes. It is believed that the cascaded multiple amplification strategy presents a huge advance in sensing platform and potential application in future clinical diagnosis.

Sensitive and specific detection of miRNA using an isothermal exponential amplification method using fluorescence-labeled LNA/DNA chimera primers

MicroRNAs (miRNAs) are currently considered as potential biomarkers for various human diseases. In the present study, miRNA-triggered real-time fluorescent isothermal reaction with exponential amplification (ReFIRE) with or without Thermus aquaticus MutS (Taq MutS) was developed to analyze miRNAs using DNA polymerase, a nicking endonuclease, and fluorescently labeled primers. In the absence of Taq MutS, the ReFIRE system permitted the detection of 100 ymol of targeted miRNA in 80 min. However, this system enabled limited differentiation between homologous miRNA family members. Upon addition of Taq MutS to the ReFIRE system, non-specific amplification generated from the mishybridization between primers and primer dimers or primers and the template duplex was eliminated. The addition of Taq MutS enabled the ultrasensitive detection of as little as 10 ymol of targeted miRNAs in 50 min, which corresponds to less than 10 copies of miRNAs in a total volume of 20 μl. Additionally, the assay exhibited a dynamic range of up to 12 orders of magnitude. The ReFIRE system also showed high specificity, enabling differentiation between homologous miRNA family members exhibiting only single-base differences. The sensitivity, specificity, and dynamic range associated with this system were greater than most currently available miRNA isothermal amplification assays. Moreover, when target-specific primers were labeled with different fluorescent reporters, multiplex analysis was easily performed in a single tube, permitting accurate normalization of miRNA expression. This simple, fast, ultrasensitive, highly specific, and easy-to-multiplex method could significantly contribute to research investigations pertaining to the biological roles of miRNA, as well as clinical diagnosis of various diseases that involve miRNA disruptions. Graphical Abstract The principle of ReFIRE system.

DNA-fueled molecular machine for label-free and non-enzymatic ultrasensitive detection of telomerase activity

Herein, a non-enzymatic and label-free strategy based on DNA-fueled molecular machine was developed for ultrasensitive detection of telomerase activity in cancer cell extracts even at the single-cell level.

Quantitative Detection of MicroRNA in One Step via Next Generation Magnetic Relaxation Switch Sensing

One-step, quantitative and rapid detection of microRNA (miRNA) in tumor cells or tissues can provide critical information for clinical diagnosis and cancer treatment. In this work, we develop a magnetic relaxation switch sensing (MRS)-based miRNA sensor using magnetic microparticle (1 μm in diameter, MM1000)-DNA probe-magnetic nanoparticle (30 nm in diameter, MN30) conjugates (MM1000-DNA-MN30). In the presence of target miRNA, DSN enzyme selectively cleaves the DNA tether after miRNA/DNA hybridization to release MN30 and leaves the miRNA intact to lead to the declustering of more MN30 than before. In contrast to conventional MRS by measuring the change of transverse relaxation time (ΔT2) induced by the aggregation or dissociation of magnetic particles in the presence of target, we use the cleaved MN30 from conjugates as the direct readout of ΔT2, which is more sensitive and stable. This MRS-based assay allows for one-step detection of 5 fM of miR-21 in urine samples, quantification of miR-21 from 100 cancer cells, and differentiation of the expression of miR-21 in tumor and surrounding tissues. The merits of this assay, rapidity, ability for quantitation, high sensitivity, and one-step operation, ensure a promising future in diagnostic technology.

Near-Infrared Ag2S Quantum Dots-Based DNA Logic Gate Platform for miRNA Diagnostics

Dysregulation of miRNA expression is correlated with the development and progression of many diseases. These miRNAs are regarded as promising biomarkers. However, it is challenging to measure these low abundant molecules without employing time-consuming radioactive labeling or complex amplification strategies. Here, we present a DNA logic gate platform for miRNA diagnostics with fluorescence outputs from near-infrared (NIR) Ag2S quantum dots (QDs). Carefully designed toehold exchange-mediated strand displacements with different miRNA inputs occur on a solid-state interface, which control QDs release from solid-state interface to solution, responding to multiplex information on initial miRNAs. Excellent fluorescence emission properties of NIR Ag2S QDs certify the great prospect for amplification-free and sensitive miRNA assay. We demonstrate the potential of this platform by achieving femtomolar level miRNA analysis and the versatility of a series of logic circuits computation.

Multicolor-Encoded Reconfigurable DNA Nanostructures Enable Multiplexed Sensing of Intracellular MicroRNAs in Living Cells

Despite the widespread utilization of gold nanoparticles and graphene for in vivo applications, complex steps for the preparation and functionalization of these nanomaterials are commonly required. In addition, the cytotoxicity of such materials is currently still under debate. In this work, by taking the significant advantages of DNA in terms of biocompatibility, nontoxicity, and controllability as building blocks for DNA nanostructures, we describe the construction of a reconfigurable, multicolor-encoded DNA nanostructure for multiplexed monitoring of intracellular microRNAs (miRNAs) in living cells. The DNA nanostructure nanoprobes containing two fluorescently quenched hairpins can be obtained by simple thermal annealing of four ssDNA oligonucleotides. The presence of the target miRNAs can unfold the hairpin structures and recover fluorescent emissions at distinct wavelengths to achieve multiplexed detection of miRNAs. Importantly, the DNA nanostructure nanoprobes exhibit significantly improved stability over conventional DNA molecular beacon probes in cell lysates and can steadily enter cells to realize simultaneous detection of two types of intracellular miRNAs. The demonstration of the self-assembled DNA nanostructures for intracellular sensing thus offers great potential application of these nanoprobes for imaging, drug delivery and cancer therapy in vivo.

Metal nanoclusters: novel probes for diagnostic and therapeutic applications

Metal nanoclusters, composed of several to a few hundred metal atoms, have received worldwide attention due to their extraordinary physical and chemical characteristics. Recently, great efforts have been devoted to the exploration of the potential diagnostic and therapeutic applications of metal nanoclusters. Here we focus on the recent advances and new horizons in this area, and introduce the rising progress on the use of metal nanoclusters for biological analysis, biological imaging, therapeutic applications, DNA assembly and logic gate construction, enzyme mimic catalysis, as well as thermometers and pH meters. Furthermore, the future challenges in the construction of biofunctional metal nanoclusters for diagnostic and therapeutic applications are also discussed. We expect that the rapidly growing interest in metal nanocluster-based theranostic applications will certainly not only fuel the excitement and stimulate research in this highly active field, but also inspire broader concerns across various disciplines.

Colorimetric detection of sequence-specific microRNA based on duplex-specific nuclease-assisted nanoparticle amplification

Developing simple and rapid methods for sequence-specific microRNA (miRNA) analysis is imperative to the miRNA study and use in clinical diagnosis. We have developed a colorimetric method for miRNA detection based on duplex-specific nuclease (DSN)-assisted signal amplification coupled to the aggregation of gold nanoparticles (AuNPs). The proposed method involves two processes: target-mediated probe digestion by a DSN enzyme and probe-triggered AuNP aggregation as a switch for signal output. The reaction system consists of a rationally designed probe complex formed by two partly complementary DNA probes, and two sets of different oligonucleotide-modified AuNPs with sequences complementary to a DNA probe in the probe complex. In the presence of target miRNA, the probe complex is invaded, resulting in the formation of a miRNA-probe heteroduplex as the substrate of the DSN enzyme, and releasing the other probe to link to the AuNPs. The proposed method allows quantitative detection of miR-122 in the range of 20 pM to 1 nM with a detection limit of ∼16 pM, and shows an excellent ability to discriminate single-base differences. Moreover, the detection assay can be applied to accurately quantify miR-122 in cancerous cell lysates which is in excellent agreement with the results from a commercial miRNA detection kit. This method is simple, cost-effective, highly selective, and free of dye label and separation procedures.

A microRNA-activated molecular machine for non-enzymatic target recycling amplification detection of microRNA from cancer cells

The presence of the microRNA-141 target molecules activates the DNA molecular machine powered by the DNA fuel strands, leading to non-enzymatic target cyclic reuse of microRNA-141 and significantly amplified fluorescent signals for sensitive monitoring of microRNA-141 from low numbers of human prostate cancer cells.

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.

Human serum biomarker detection based on a cascade signal amplification strategy by a DNA molecule machine

A convenient method is presented that employs a DNA machine for protein biomarker detection. The detection limit is 400 times lower compared to the method without a DNA machine. This study provides a promising method that could realize most protein biomarker detections without the corresponding aptamers, using a DNA machine for signal amplification.

Sensitive and homogeneous microRNA detection using branched cascade enzymatic amplification

This assay, termed branched cascade enzymatic amplification (BCEA), can be a novel and straightforward method for sensitive and specific microRNA detection in crude cellular extracts of cancer cells at physiological temperature, by coupling two ordinary polymerases, Klenow fragment exo(-) and terminal deoxynucleotidyl transferase.

Invading stacking primer: A trigger for high-efficiency isothermal amplification reaction with superior selectivity for detecting microRNA variants

Searching for a strategy to enhance the efficiency of nucleic acid amplification and achieve exquisite discrimination of nucleic acids at the single-base level for biological detection has become an exciting research direction in recent years. Here, we have developed a simple and universal primer design strategy which produces a fascinating effect on isothermal strand displacement amplification (iSDA). We refer to the resultant primer as "invading stacking primer (IS-Primer)" which is based on contiguous stacking hybridization and toehold-mediated exchange reaction and function by merely changing the hybridization location of the primer. Using the IS-Primer, the sensitivity in detecting the target miR-21 is improved approximately five fold compared with the traditional iSDA reaction. It was further demonstrated that the IS-Primer acts as an invading strand to initiate branch migration which can increase the efficiency of the untwisting of the hairpin probe. This effect is equivalent to reducing the free energy of the stem, and the technique shows superior selectivity for single-base mismatches. By demonstrating the enhanced effect of the IS-Primer in the iSDA reaction, this work may provide a potentially new avenue for developing more sensitive and selective nucleic acids assays.