•A novel “clickable” sensing platform relied on AIE-active molecules is established to achieve sensitive and selective detection of Cu2+.•The dramatic “turn-on” luminescent induced by Cu2+ can be observed with the naked eye.•Attractively, the detection process achieves superior selectivity and extremely low-background interference.•The method can be practically applied for Cu2+ monitoring in real drinking and environmental water; and good potential for monitoring of copper contamination.A novel “clickable” sensing platform for signal-on fluorescent detection of Cu2+ has been developed based on the high regioselectivity of Cu(I)-catalyzed azide–alkyne click reaction (CuAAC) and the aggregated AIE-active molecules (BATPE) as the signal reporters. The CuAAC reaction causes a structural change of BATPE from molecularly dispersed to aggregate state in the presence of trace Cu2+, thus inducing a dramatic fluorescence “turn-on” response which can be judged with the naked eye. Under the optimum conditions, down to 0.2 μM and 0.5 μM Cu2+ were successfully detected by fluorescence spectrophotometer and naked eye, respectively. This method is simple and low-cost without the need for expensive equipment. Thanks to the superior specificity of CuAAC reaction, our assay is capable of sensing Cu2+ in the existence of other environmentally relevant metal ions in real samples, indicating that it may serve as a promising sensor for on-site Cu2+ analysis.

•A novel fluorescence biosensor for highly sensitive and selective detection of miRNA was established.•A dual signal amplification strategy based on single enzyme (DSN) was developed and evaluated.•DNA/2-OMe-RNA chimeric probe was utilized to connect two rounds of cyclical amplification.•This strategy can easily be applied to all miRNAs and holds great potential for further application.The accurate and quantitative analysis of microRNA (miRNA) expression is critical for biomedical research and clinical theranostics. In this study, we report a novel sensor for the sensitive detection of miRNA based on a duplex-specific nuclease (DSN)-assisted dual signal amplification strategy. A chimeric probe (DNA/2-OMe-RNA) that consists of a miRNA recognition DNA sequence and a Taqman probe hybridization RNA sequence (2′-O-methyl RNA) was designed and synthesized. One molecule of target miRNA can trigger cyclical cleavage of the chimeric probes to produce 2′-O-methyl RNA by DSN in the first round of amplification. The 2′-O-methyl RNA molecules can subsequently hybridize with Taqman probes and initiate the second round of cyclical amplification to generate detectable fluorescence by DSN. The proposed strategy exhibits high specificity in discriminating cognate miRNAs, and the dual signal transduction process enables the detection of miRNA concentrations as low as 7.3 fM. We further applied this assay to miRNA quantification in cancer cells to confirm its applicability. The present study provides a sensitive, specific and simple method for miRNA detection and holds great potential for further application in biomedical research and in the clinical laboratory.

•An electrochemical sensing assay for sensitive determination of HIV-1 in a homogeneous solution has been developed.•The electrochemical molecular beacon (CAs-MB) for HIV-1 gag gene is beneficial to the simplification of detection procedure and improvement of signal-to-noise ratio.•The nafion–graphene/SPCE microelectrode was used to monitor the changes of CAs-MB in order to further improve the sensitivity.•This work may lead to the development of an effective method for early point-of-care diagnosis of HIV-1 infection.A novel electrochemical sensing assay for sensitive determination of HIV-1 in a homogeneous solution has been developed using an electrochemical molecular beacon combined with a nafion–graphene composite film modified screen-printed carbon electrode (nafion–graphene/SPCE). The electrochemical molecular beacon (CAs-MB), comprising a special recognition sequence for the conserved region of the HIV-1 gag gene and a pair of carminic acid molecules as a marker, can indicate the presence of the HIV-1 target by its on/off electrochemical signal behavior. It is suitable for direct, electrochemical determination of HIV-1, thereby simplifying the detection procedure and improving the signal-to-noise (S/N) ratio. To further improve the sensitivity, the nafion–graphene/SPCE was used to monitor changes in the CAs-MB, which has notable advantages, such as being ultrasensitive, inexpensive, and disposable. Under optimized conditions, the peak currents showed a linear relationship with the logarithm of target oligonucleotide concentrations ranging from 40 nM to 2.56 μM, with a detection limit of 5 nM (S/N=3). This sensing assay also displays a good stability, with a recovery of 88–106.8% and RSD<7% (n=5) in real serum samples. This work may lead to the development of an effective method for early point-of-care diagnosis of HIV-1 infection.

microRNAs (miRNAs) are evolutionarily conserved small non-coding RNAs, approximately 22 nucleotides (nts) in length, widely found in animals, plants, and viruses. Mature miRNAs control gene expression at a post-transcriptional level through blocking protein translation or inducing mRNA degradation. Many recent studies have shown that hepatitis B virus x protein (HBx), a viral protein with a crucial role in hepatogenesis, is associated with the regulation of miRNAs. This interaction impacts fundamental tumor processes, such as cell proliferation, differentiation, and apoptosis. In this review, we summarized the recent literature on the roles of HBx-regulated miRNAs in the pathogenesis of hepatocellular carcinoma.

A novel electrochemical biosensor was developed for the analysis of BRAF V600E mutation in colorectal cancer cell samples based on a dual amplification strategy of amplification-refractory mutation system (ARMS) PCR and multiple enzyme labels. The labeled amplicons were conjugated on Fe3O4/Au nanoparticles using Au–S linkages. Alkaline phosphatases were then loaded onto the nanoparticles through biotin–streptavidin interactions. The resultant composite nanoparticles were characterized by transmission electron microscopy, electrochemical impedance spectroscopy, and cyclic voltammetry. In the presence of 2-phospho-l-ascorbic acid, the mutant alleles were quantified on a screen-printed carbon electrode (SPCE) from the anodic current of the enzymatic product, ascorbic acid. BRAF V600E mutant alleles concentrations as low as 0.8% were successfully determined in an excess of wild-type background. In a cell-line dilution model, the proposed method was more sensitive than were DNA sequencing and agarose gel electrophoresis. This work demonstrates a new strategy for sensitivly detecting BRAF V600E variations. It can pave the way for analyzing other rare mutations in complex cancer samples because of its high sensitivity, simplicity, low cost, and easy validation of assay procedures.Highlights► A novel electrochemical biosensor for BRAF V600E mutation in colorectal cancer cell was established. ► A dual amplification strategy of ARMS PCR and multienzyme functionalized Fe3O4/Au nanoparticles was developed and evaluated. ► As low as 0.8% of BRAF V600E mutations were detectable among an excess of wild-type background. ► This strategy can easily be adapted to discern other hotspot mutations in clinical specimens.