An approach to sequence DNA without tagging

Abstract

Microarray technology is playing an increasingly important role in biology andmedicine and its application to genomics for gene expression analysishas already reached the market with a variety of commercially availableinstruments. In these combinatorial analysis methods, known probe single-strandDNA (ssDNA) ‘primers’ are attached in clusters of typically 100 µm × 100µm pixels. Each pixel of the array has a slightly different sequence. On exposureto ‘unknown’ target ssDNA, the pixels with the right complementaryprobe ssDNA sequence convert to double-stranded DNA (dsDNA) by ahybridization reaction. To transduct the conversion of the pixel to dsDNA,the target ssDNA is labelled with a photoluminescent tag during thepolymerase chain reaction (PCR) amplification process. Due to the statisticaldistribution of the tags in the target ssDNA, it becomes significantly difficult toimplement these methods as a diagnostic tool in a pathology laboratory. Amethod to sequence DNA without tagging the molecule is developed. Thefabrication process is compatible with current microelectronics and (emerging)soft-material fabrication technologies, allowing the method to be integrablewith micro-electromechanical systems (MEMS) and lab-on-a-chip devices.An estimated sensitivity of 10−12 g on a 1 cm2 device area is obtained.