An autonomous thymine rich DNA machine as an amplification unit was developed for the sensitive detection of mercury ions with high specificity. Combined with a lateral flow biosensor, the amplified signal of Hg2+ can be read out by the naked eye with a detection limit of 5 nM.

A universal biosensor for the portable and quantitative detection of transcription factors has been constructed using a commercially available glucometer as the sensing platform. With the specific protein-binding DNA and antibody as the recognition elements, invertase as the linker, and glucometer as the transducer, quantitative detection was achieved via target-induced capturing of invertase conjugates on magnetic beads, thereby transforming the concentration of the target in the sample into glucose through invertase-catalyzed hydrolysis of sucrose. In comparison with laboratory-based instruments or customized devices, the glucometer-based biosensor has the significant advantages of low cost, compact size, wide accessibility, and ease of use, making it as convenient for use at home as in the field. As a proof of concept, Oct4, an important transcription factor for the regulation of the process of embryonic stem cells differentiation, was used as the model target. Using the proposed point-of-care strategy, Oct4 can be quantified in the range from 0.05 to 25 ng mL−1 with a detection limit of 0.05 ng mL−1, which is comparable to the commercial Oct4 test kits. The glucometer-based biosensor is robust and can be used directly to measure the transcription factor activities in crude cell lysate with excellent selectivity. It is expected that this assay principle can be directed towards other DNA-binding transcription factors by simply changing the binding site sequence and the corresponding antibody.

•The gold-nanoparticle based lateral flow biosensor is extremely simple to use and enables visual detection.•The tedious cell lysis and DNA/RNA extraction was avoided, while a high sensitivity (101 CFU/mL) was achieved.•The specificity of the present assay is relative higher than that of nucleic acid based method. It has better response to the viable pathogens in the sample.Convenient and sensitive point-of-care rapid diagnostic tests for food-borne pathogens have been a long-felt need of clinicians. Traditional approaches such as culture-based methods have good sensitivity and specificity, but they tend to be tedious and time-consuming. Herein we present a simple and sensitive aptamer based biosensor for rapid detection of Salmonella enteritidis (S. enteritidis). One of the aptamers specific for the outmembrane of S. enteritidis was used for magnetic bead enrichments. Another aptamer against S. enteritidis was used as a reporter for this pathogen, which was amplified by isothermal strand displacement amplification (SDA) and further detected by a lateral flow biosensor. As low as 101 colony forming unit (CFU) of S. enteritidis was detected in this study. Without DNA extraction, the reduced handling and simpler equipment requirement render this assay a simple and rapid alternative to conventional methods.

•Limit of detection as low as 0.1 fM target single nucleotide polymorphism (SNP) in PBS, and 0.5 fM in human serum.•No need of polymerase or sophisticated equipment.•DNA self-assembled concatemers for signal amplification, SYBR Green I for fluorescence indicator.•Great potential application in the area of DNA diagnostics and clinical analysis.Polymerase-free and label-free strategies for DNA detection have shown excellent sensitivity and specificity in various biological samples. Herein, we propose a method for single nucleotide polymorphism (SNP) detection by using self-assembled DNA concatemers. Capture probes, bound to magnetic beads, can joint mediator probes by T4 DNA ligase in the presence of target DNA that is complementary to the capture probe and mediator probe. The mediator probes trigger self-assembly of two auxiliary probes on magnetic beads to form DNA concatemers. Separated by a magnetic rack, the double-stranded concatemers on beads can recruit a great amount of SYBR Green I and eventually result in amplified fluorescent signals. In comparison with reported methods for SNP detection, the concatemer-based approach has significant advantages of low background, simplicity, and ultrasensitivity, making it as a convenient platform for clinical applications. As a proof of concept, BRAFT1799A oncogene mutation, a SNP involved in diverse human cancers, was used as a model target. The developed approach using a fluorescent intercalator can detect as low as 0.1 fM target BRAFT1799A DNA, which is better than those previously published methods for SNP detection. This method is robust and can be used directly to measure the BRAFT1799A DNA in complex human serum with excellent recovery (94–103%). It is expected that this assay principle can be directed toward other SNP genes by simply changing the mediator probe and auxiliary probes.

A lateral flow biosensor based on immunoassay has been developed for the detection of human stem cells for the first time. Antibody specific for a human stem cell surface antigen, SSEA-4, is coated onto gold nanoparticles, whereas antibody against another human pluripotent stem cell surface antigen, SSEA-3, is immobilized on the test zone of the NC membrane. Target cells bind to the antibody coated on the gold nanoparticles to form nanoparticles–stem cell complexes, and the complexes are then captured by another antibody immobilized on the test zone to form a red line for visual detection. This biosensor has been successfully applied to human embryonic stem cells and induced pluripotent stem cells. It is capable of detecting a minimum of 10,000 human embryonic stem cells by the naked eye and 7000 cells with a portable strip reader within 20 min. This approach has also shown excellent specificity to distinguish other types of cells. The biosensor shows great promise for specific and handy detection of human pluripotent stem cells.

A rapid and reliable screening test for thalassemia carrier couples is the most effective strategy to decrease the risk of conceiving fetuses with severe thalassemia. We present an approach based on the isothermal strand-displacement polymerase reaction and the use of a lateral flow strip for the visual detection of an α-thalassemia Southeast Asian–type deletion. This assay was used to evaluate 86 clinical samples (72 cases of Southeast Asian–type deletions and 14 cases of other types of thalassemia), and the results obtained were 100% consistent with those obtained using conventional gap-PCR. The approach thus provides a simple, sensitive, rapid, and cost-effective method for the diagnosis of thalassemia genotypes.

A universal biosensor for the portable and quantitative detection of transcription factors has been constructed using a commercially available glucometer as the sensing platform. With the specific protein-binding DNA and antibody as the recognition elements, invertase as the linker, and glucometer as the transducer, quantitative detection was achieved via target-induced capturing of invertase conjugates on magnetic beads, thereby transforming the concentration of the target in the sample into glucose through invertase-catalyzed hydrolysis of sucrose. In comparison with laboratory-based instruments or customized devices, the glucometer-based biosensor has the significant advantages of low cost, compact size, wide accessibility, and ease of use, making it as convenient for use at home as in the field. As a proof of concept, Oct4, an important transcription factor for the regulation of the process of embryonic stem cells differentiation, was used as the model target. Using the proposed point-of-care strategy, Oct4 can be quantified in the range from 0.05 to 25 ng mL−1 with a detection limit of 0.05 ng mL−1, which is comparable to the commercial Oct4 test kits. The glucometer-based biosensor is robust and can be used directly to measure the transcription factor activities in crude cell lysate with excellent selectivity. It is expected that this assay principle can be directed towards other DNA-binding transcription factors by simply changing the binding site sequence and the corresponding antibody.

An autonomous thymine rich DNA machine as an amplification unit was developed for the sensitive detection of mercury ions with high specificity. Combined with a lateral flow biosensor, the amplified signal of Hg2+ can be read out by the naked eye with a detection limit of 5 nM.