Thermoelectric method for sequencing DNA

This study describes a novel, thermoelectric method for DNA sequencing in a microfluidic device. The method measures the heat released when DNA polymerase inserts a deoxyribonucleoside triphosphate into a primed DNA template. The study describes the principle of operation of a laminar flow microfluidic chip with a reaction zone that contains DNA template/primer complex immobilized to the inner surface of the device's lower channel wall. A thin-film thermopile attached to the external surface of the lower channel wall measures the dynamic change in temperature that results when Klenow polymerase inserts a deoxyribonucleoside triphosphate into the DNA template. The intrinsic rejection of common-mode thermal signals by the thermopile in combination with hydrodynamic focused flow allows for the measurement of temperature changes on the order of 10(-4) K without control of ambient temperature. To demonstrate the method, we report the sequencing of a model oligonucleotide containing 12 bases. Results demonstrate that it is feasible to sequence DNA by measuring the heat released during nucleotide incorporation. This thermoelectric method for sequencing DNA may offer a novel new method of DNA sequencing for personalized medicine applications.

Electrochemical detection of oligonucleotide by attaching redox probes onto its backbone

An approach was demonstrated to detect oligonucleotide by attaching redox probes onto its backbone. First, peptide nucleic acid (PNA) with a neutral backbone was immobilized onto a gold (Au) electrode surface as a capture. Second, when the PNA capture hybridized with a target oligonucleotide (a short DNA), an assembly of Au-PNA-DNA formed and phosphate groups were thus brought into the assembly from the DNA's backbone. The linker ion of Zr(4+) exhibits a strong coordination interaction with the phosphate group and the carboxylic group. The hybridized target DNA provides the phosphate group while a derivatized redox probe of ferrocene (Fc) carboxyl acid offers the carboxylic group. Therefore, the redox probe can be attached to the phosphate group by the linker to form an assembly of Au-PNA-DNA-Zr-Fc. Its redox process was studied and the detection conditions of oligonucleotide were optimized. A limit of detection of 1.0×10(-12) M or ∼2 attomol was reached.

Structural optimization for heat detection of DNA thermosequencing platform using finite element analysis

For the past three decades, Sanger's method has been the primary DNA sequencing technology; however, inherent limitations in cost and complexity have limited its usage in personalized medicine and ecological studies. A new technology called "thermosequencing" can potentially reduce both the cost and complexity of DNA sequencing by using a microfluidic platform [Esfandyarpour, Pease, and Davis, J. Vac. Sci. Technol. B26, 661 (2008)]. To optimize the efficiency of the technology, finite element analysis was used to model the thermosequencing system by simulating the DNA incorporation reaction series and the resulting product concentration and heat production. Different models of the thermosequencing platform were created to simulate the effects of the materials surrounding the system, to optimize the geometry of the system, and to concentrate reaction heat into specific regions for detection in the real system. The resulting concentrations of reaction products were used to calibrate the reaction speed and to design the heat sensors in the thermosequencing technology. We recommend a modified gated structure for the microfluidic detection platform by using control valves and show how this new platform could dramatically improve the detection efficiency.