Detection of <I>K</I>-Ras Oncogene from the Human Genomic DNA Using Ultrasonication and a Quantum Dots-Based Microfluidic Chip

Abstract

In clinical diagnostics, single-stranded DNAs (ssDNA) have been prepared from the human genomic DNA for the detection of a specific gene. In this study, the human genomic DNA was degraded via ultrasonication in solution, and K-ras oncogene was detected from the DNA fragments via the fluorescence quenching of quantum dots (QDs) by intercalating dyes after hybridization of the target, to probe DNAs in a microfluidic chip. K-ras is one of the most activated common oncogenes, and many human tumors are known to be due to the mutation of this gene. QDs are nano-sized semiconductors with a wide selection of emission wavelengths and exceptional stability against photo bleaching. In this study, probe DNA-conjugated QDs were immobilized to polystyrene microbeads, and the DNA-microbead-QDs complexes were packed through a microchannel by pillars that trap the beads in the microfluidic chip. The fluorescence of the QDs could be quenched by intercalating dye (TOTO-3) after hybridization of K-ras oncogene to the probe DNA in the channel. The fluorescence intensity decrease of the QDs can be used as an indication of the K-ras oncogene. By introducing an alkaline buffer solution, the DNAs were denatured, and the fluorescence intensity of the QDs again increased, which shows the possibility of reuse of the microfluidic chip for the detection of the K-ras gene.