A simple “mix-and-detection” method for the sensitive detection of telomerase from cancer cells under absolutely isothermal conditions

We develop a simple “mix-and-detection” method for the sensitive detection of telomerase from cancer cells under absolutely isothermal conditions.

Towards Multiplex Molecular Diagnosis-A Review of Microfluidic Genomics Technologies

Highly sensitive and specific pathogen diagnosis is essential for correct and timely treatment of infectious diseases, especially virulent strains, in people. Point-of-care pathogen diagnosis can be a tremendous help in managing disease outbreaks as well as in routine healthcare settings. Infectious pathogens can be identified with high specificity using molecular methods. A plethora of microfluidic innovations in recent years have now made it increasingly feasible to develop portable, robust, accurate, and sensitive genomic diagnostic devices for deployment at the point of care. However, improving processing time, multiplexed detection, sensitivity and limit of detection, specificity, and ease of deployment in resource-limited settings are ongoing challenges. This review outlines recent techniques in microfluidic genomic diagnosis and devices with a focus on integrating them into a lab on a chip that will lead towards the development of multiplexed point-of-care devices of high sensitivity and specificity.

Nanoprobe-Initiated Enzymatic Polymerization for Highly Sensitive Electrochemical DNA Detection

Electrochemical DNA (E-DNA) sensors have been greatly developed and play an important role in early diagnosis of different diseases. To determine the extremely low abundance of DNA biomarkers in clinical samples, scientists are making unremitting efforts toward achieving highly sensitive and selective E-DNA sensors. Here, a novel E-DNA sensor was developed taking advantage of the signal amplification efficiency of nanoprobe-initiated enzymatic polymerization (NIEP). In the NIEP based E-DNA sensor, the capture probe DNA was thiolated at its 3'-terminal to be immobilized onto gold electrode, and the nanoprobe was fabricated by 5'-thiol-terminated signal probe DNA conjugated gold nanoparticles (AuNPs). Both of the probes could simultaneously hybridize with the target DNA to form a "sandwich" structure followed by the terminal deoxynucleotidyl transferase (TdT)-catalyzed elongation of the free 3'-terminal of DNA on the nanoprobe. During the DNA elongation, biotin labels were incorporated into the NIEP-generated long single-stranded DNA (ssDNA) tentacles, leading to specific binding of avidin modified horseradish peroxidase (Av-HRP). Since there are hundreds of DNA probes on the nanoprobe, one hybridization event would generate hundreds of long ssDNA tentacles, resulting in tens of thousands of HRP catalyzed reduction of hydrogen peroxide and sharply increasing electrochemical signals. By employing nanoprobe and TdT, it is demonstrated that the NIEP amplified E-DNA sensor has a detection limit of 10 fM and excellent differentiation ability for even single-base mismatch.

A Label-Free, Sensitive, Real-Time, Semiquantitative Electrochemical Measurement Method for DNA Polymerase Amplification (ePCR)

Oligonucleotide hybridization to a complementary sequence that is covalently attached to an electrochemically active conducting polymer (ECP) coating the working electrode of an electrochemical cell causes an increase in reaction impedance for the ferro-ferricyanide redox couple. We demonstrate the use of this effect to measure, in real time, the progress of DNA polymerase chain reaction (PCR) amplification of a minor component of a DNA extract. The forward primer is attached to the ECP. The solution contains other PCR components and the redox couple. Each cycle of amplification gives an easily measurable impedance increase. Target concentration can be estimated by cycle count to reach a threshold impedance. As proof of principle, we demonstrate an electrochemical real-time quantitative PCR (e-PCR) measurement in the total DNA extracted from chicken blood of an 844 base pair region of the mitochondrial Cytochrome c oxidase gene, present at ∼1 ppm of total DNA. We show that the detection and semiquantitation of as few as 2 copies/μL of target can be achieved within less than 10 PCR cycles.

Electrical and electrochemical monitoring of nucleic Acid amplification

Nucleic acid amplification is a gold standard technique for analyzing a tiny amount of nucleotides in molecular biology, clinical diagnostics, food safety, and environmental testing. Electrical and electrochemical monitoring of the amplification process draws attention over conventional optical methods because of the amenability toward point-of-care applications as there is a growing demand for nucleic acid sensing in situations outside the laboratory. A number of electrical and electrochemical techniques coupled with various amplification methods including isothermal amplification have been reported in the last 10 years. In this review, we highlight recent developments in the electrical and electrochemical monitoring of nucleic acid amplification.