Junhua Chen

An enzyme-free and label-free assay for copper(II) ion detection based on self-assembled DNA concatamers and Sybr Green I

An enzyme-free and label-free fluorescence turn on biosensor for amplified copper(II) ion (Cu(2+)) detection has been constructed based on self-assembled DNA concatamers and Sybr Green I. This assay is simple, inexpensive and sensitive, enabling quantitative detection of as low as 12.8 pM Cu(2+).

An autonomous T-rich DNA machine based lateral flow biosensor for amplified visual detection of mercury ions

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 glucometer-based biosensor for portable and quantitative detection of transcription factors

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.

A self-assembled deoxyribonucleic acid concatemer for sensitive detection of single nucleotide polymorphism.

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, BRAF(T1799A) 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 BRAF(T1799A) DNA, which is better than those previously published methods for SNP detection. This method is robust and can be used directly to measure the BRAF(T1799A) 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.